This document summarizes femtosecond-resolved experiments on the primary photochemistry of 9-nitroanthracene. The experiments observed the ultrafast decay of the initially excited singlet state through time-resolved fluorescence, and detected the accumulation of the anthryloxy radical and formation of the relaxed phosphorescent T1 state through transient absorption experiments. The experiments provide timescales for the formation of the primary photoproducts, the anthryloxy radical and the T1 state, which both occur within a few picoseconds. Calculations were also performed to understand the molecular orbitals responsible for intersystem crossing between the singlet and triplet manifolds.
This document summarizes a study investigating the initialization behavior of reversible addition-fragmentation chain transfer (RAFT)-mediated styrene-maleic anhydride copolymerizations using in situ 1H NMR spectroscopy. The results indicate specificity of addition of the RAFT agent leaving groups for either styrene or maleic anhydride. Analysis of the NMR spectra also showed that monomers are added individually, favoring the penultimate unit model of polymer propagation over other proposed mechanisms. Stereoselectivity was observed during monomer addition to the RAFT agent.
The document describes using reversible addition-fragmentation chain transfer (RAFT) polymerization to synthesize novel block copolymers containing both a polyolefin block and a poly(styrene-co-maleic anhydride) block. Specifically, it details:
1) Using a commercially available polyolefin (Kraton L-1203) modified with a dithioester group to serve as a macroinitiator for RAFT polymerization and form the polyolefin block.
2) Conducting RAFT polymerizations of styrene and styrene-co-maleic anhydride using this macroinitiator and a small molecule RAFT agent to form the second block and yield polyolefin
Comparison of the structures and vibrational modes of carboxybiotin and n car...John Clarkson
J. Clarkson & P.R. Carey, "Comparison of the Structures and Vibrational Modes of Carboxybiotin and N-Carboxy-2-imidazolidone" J. Phys. Chem. A, 103, 2851-2856, 1999.
Coulomb Screening and Coherent Phonon in Methylammonium Lead Iodide PerovskitesLexi Cao
This document reports on a study of exciton and carrier dynamics in methylammonium lead iodide perovskite (CH3NH3PbI3) in the tetragonal and orthorhombic phases using transient absorption spectroscopy. The authors observe stronger saturation of free carrier concentration under high light intensity in the orthorhombic phase compared to the tetragonal phase. They attribute this to weaker Coulomb screening and more difficult exciton dissociation in the orthorhombic phase due to its smaller dielectric constant and larger exciton binding energy. At high excitation intensities and low temperature, they also observe a coherent phonon oscillation with a frequency of 23.4 cm-1 that may contribute
Induction of Luminol Chemiluminescence by the Manganese Cluster of the Photos...Igor Putrenko
This document summarizes research on the induction of chemiluminescence (CL) by the manganese cluster of the photosystem II water-oxidizing complex (WOC) in different S states. The key points are:
1) Luminol CL is induced when PSII particles or manganese coordination complexes are added to a luminol-peroxidase reaction medium, with the CL intensity varying based on the ligand environment and S state of the WOC or complex.
2) The CL from PSII particles consists of a fast (signal A) and slow (signal B) component, with signal B enhanced for particles illuminated with multiple flashes. Signal B is dependent on electron transfer in P
This document summarizes the mechanochemical synthesis of isoreticular metal-organic frameworks (IRMOFs) and their potential for nitrobenzene sensing. Specifically, it discusses:
1) The liquid-assisted grinding synthesis of IRMOF-1 and halogen-substituted IRMOF-2 frameworks containing chlorine, bromine, or iodine.
2) Characterization of the frameworks by powder X-ray diffraction and scanning electron microscopy, which confirmed their structures.
3) Investigation of the frameworks' fluorescence properties, which revealed IRMOF-1 is a highly sensitive and selective fluorescence quenching agent for nitrobenzene detection.
4) The role of
1) Veratrole was electrooxidized on a platinum electrode in acetonitrile solutions containing either tetrabutylammonium perchlorate or lithium perchlorate.
2) A green deposit formed containing hexamethoxytriphenylene radical cation species associated with perchlorate counterions.
3) Spectroelectrochemical experiments showed that oxidation of perchlorate anions above 2.3V dissolved the deposit, but sweeping the potential back regenerated the solid, allowing the process to be cycled.
Synthesis, Spectroscopic study & Biological Activity Of Some Organotin(Iv) De...IOSR Journals
Some di-and triorganotin(IV) derivatives of (2E)-N-methyl-(2
oxo1,2diphenylethylidne)hydrazinecarbothioamide synthesised by the reactions of the corresponding di and
triorganotin(IV) chlorides with the sodium salt of (2E)-N-methyl-(2-
oxo1,2diphenylethylidne)hydrazinecarbothioamide in different molar ratios. These derivatives have been
characterized by elemental analyses ,molecular weights, conductivity measurements and spectral(IR, 1H, 13C
and 119 Sn NMR) studies.
This document summarizes a study investigating the initialization behavior of reversible addition-fragmentation chain transfer (RAFT)-mediated styrene-maleic anhydride copolymerizations using in situ 1H NMR spectroscopy. The results indicate specificity of addition of the RAFT agent leaving groups for either styrene or maleic anhydride. Analysis of the NMR spectra also showed that monomers are added individually, favoring the penultimate unit model of polymer propagation over other proposed mechanisms. Stereoselectivity was observed during monomer addition to the RAFT agent.
The document describes using reversible addition-fragmentation chain transfer (RAFT) polymerization to synthesize novel block copolymers containing both a polyolefin block and a poly(styrene-co-maleic anhydride) block. Specifically, it details:
1) Using a commercially available polyolefin (Kraton L-1203) modified with a dithioester group to serve as a macroinitiator for RAFT polymerization and form the polyolefin block.
2) Conducting RAFT polymerizations of styrene and styrene-co-maleic anhydride using this macroinitiator and a small molecule RAFT agent to form the second block and yield polyolefin
Comparison of the structures and vibrational modes of carboxybiotin and n car...John Clarkson
J. Clarkson & P.R. Carey, "Comparison of the Structures and Vibrational Modes of Carboxybiotin and N-Carboxy-2-imidazolidone" J. Phys. Chem. A, 103, 2851-2856, 1999.
Coulomb Screening and Coherent Phonon in Methylammonium Lead Iodide PerovskitesLexi Cao
This document reports on a study of exciton and carrier dynamics in methylammonium lead iodide perovskite (CH3NH3PbI3) in the tetragonal and orthorhombic phases using transient absorption spectroscopy. The authors observe stronger saturation of free carrier concentration under high light intensity in the orthorhombic phase compared to the tetragonal phase. They attribute this to weaker Coulomb screening and more difficult exciton dissociation in the orthorhombic phase due to its smaller dielectric constant and larger exciton binding energy. At high excitation intensities and low temperature, they also observe a coherent phonon oscillation with a frequency of 23.4 cm-1 that may contribute
Induction of Luminol Chemiluminescence by the Manganese Cluster of the Photos...Igor Putrenko
This document summarizes research on the induction of chemiluminescence (CL) by the manganese cluster of the photosystem II water-oxidizing complex (WOC) in different S states. The key points are:
1) Luminol CL is induced when PSII particles or manganese coordination complexes are added to a luminol-peroxidase reaction medium, with the CL intensity varying based on the ligand environment and S state of the WOC or complex.
2) The CL from PSII particles consists of a fast (signal A) and slow (signal B) component, with signal B enhanced for particles illuminated with multiple flashes. Signal B is dependent on electron transfer in P
This document summarizes the mechanochemical synthesis of isoreticular metal-organic frameworks (IRMOFs) and their potential for nitrobenzene sensing. Specifically, it discusses:
1) The liquid-assisted grinding synthesis of IRMOF-1 and halogen-substituted IRMOF-2 frameworks containing chlorine, bromine, or iodine.
2) Characterization of the frameworks by powder X-ray diffraction and scanning electron microscopy, which confirmed their structures.
3) Investigation of the frameworks' fluorescence properties, which revealed IRMOF-1 is a highly sensitive and selective fluorescence quenching agent for nitrobenzene detection.
4) The role of
1) Veratrole was electrooxidized on a platinum electrode in acetonitrile solutions containing either tetrabutylammonium perchlorate or lithium perchlorate.
2) A green deposit formed containing hexamethoxytriphenylene radical cation species associated with perchlorate counterions.
3) Spectroelectrochemical experiments showed that oxidation of perchlorate anions above 2.3V dissolved the deposit, but sweeping the potential back regenerated the solid, allowing the process to be cycled.
Synthesis, Spectroscopic study & Biological Activity Of Some Organotin(Iv) De...IOSR Journals
Some di-and triorganotin(IV) derivatives of (2E)-N-methyl-(2
oxo1,2diphenylethylidne)hydrazinecarbothioamide synthesised by the reactions of the corresponding di and
triorganotin(IV) chlorides with the sodium salt of (2E)-N-methyl-(2-
oxo1,2diphenylethylidne)hydrazinecarbothioamide in different molar ratios. These derivatives have been
characterized by elemental analyses ,molecular weights, conductivity measurements and spectral(IR, 1H, 13C
and 119 Sn NMR) studies.
Gas chromatography is a technique used to separate mixtures based on differences in polarity. It involves injecting a sample into a column containing a stationary phase, then using an inert gas mobile phase to carry the separated components out of the column, where they are detected individually. Key aspects include using an inert gas like helium as the mobile phase, a coated solid or liquid stationary phase in the column, and detectors that can identify separated components as they exit the column. Gas chromatography is useful for separating compounds that are thermally stable up to 300°C and allows for both qualitative and quantitative analysis of sample mixtures.
The document reports on an experimental study to determine the pKa (acid dissociation constant) of perfluorooctanoic acid (PFOA) using potentiometric titration in a water-methanol mixed solvent system. The study found:
1) The pKa of monomeric PFOA was determined to be 3.8 ± 0.1. This value is important for understanding the environmental fate of PFOA as both its ionized and non-ionized forms have different physicochemical properties.
2) The pKa was suppressed to around 2.3 at higher PFOA concentrations due to aggregation of its conjugate base. Many previous studies measured partitioning coefficients at concentrations above environmental levels,
This document discusses spectroscopy problem solving techniques including:
1) Chemical shifts and how equivalent protons will have the same shift and not couple.
2) Identifying the number of signals in a spectrum by considering equivalent protons.
3) Examples of assigning proton and carbon signals in spectra of compounds like ethylacetate and determining structures.
4) Factors that influence chemical shifts like functional groups and solvents.
5) Details on 13C NMR spectra and how coupling to protons is observed but can be removed through decoupling.
This document discusses the synthesis and characterization of three-ring mesogens with a terminal dimethylamino group. Key findings include:
1. Three mesogens were synthesized with varying alkyl chain lengths. Differential scanning calorimetry and polarized optical microscopy showed the compounds exhibited nematic and smectic A phases.
2. X-ray diffraction of one compound (DdIMPDB) surprisingly found an interdigitated smectic A layer organization, which is uncommon for dimethylamino-based mesogens.
3. Density functional theory calculations and NMR spectroscopy were used to determine molecular geometry and carbon chemical shifts for structural analysis. Photophysical properties also indicated intramolecular charge transfer interactions.
4. Solid-
The document summarizes the preparation and characterization of a novel luminescent terbium inorganic/organic hybrid material. 4-tert-butylbenzoic acid was modified with 3-aminopropyl trimethoxysilane to create a ligand (TBBA-APMS) that can both coordinate with terbium ions and undergo a sol-gel reaction with TEOS. This resulted in a hybrid material (Tb-TBBA-APMS) with bonds between Tb-O and Si-O. Characterization with UV-Vis, fluorescence and phosphorescence spectroscopy confirmed energy transfer between the ligand and terbium, producing strong terbium luminescence.
This doctoral thesis uses computational methods like density functional theory and molecular dynamics simulations to study the structural and functional role of cytochrome P450 enzymes. It investigates the metabolism of various substrates by CYP3A4 and CYP450 enzymes to understand reaction pathways and influence of substrate structure on reactivity. Specific reactions studied include hydroxylation of phenyl rings, morpholine rings, and camphor. Flexibility studies using the RIGIX program also examined how the protein environment modulates electronic structure and reactivity. The research provides new insights into CYP450 catalysis at the molecular level and could aid in drug design.
The document describes an in situ study using UV-visible spectroscopy to measure the kinetics of propane oxidative dehydrogenation (ODH) on vanadium oxide catalysts. Transients in UV-visible intensity during ODH reactions were analyzed using a surface reaction mechanism. Rate constants for the kinetically relevant C-H bond activation step were determined and compared to values from steady-state ODH rates. The ratio of these values provides a measure of the fraction of active vanadium sites. Reoxidation rate constants, which cannot be obtained from steady-state analysis, were also determined and found to be orders of magnitude larger than C-H bond activation rates.
This document summarizes research on the bulk copolymerization of L-lactide (LLA) and ε-caprolactone (CL) catalyzed by the organocatalyst dibenzoylmethane (DBM), which allows for the metal-free synthesis of random copolyesters. The researchers achieved good control over the ring-opening copolymerization as indicated by linear increases in molecular weight with conversion and dispersities below 1.5. NMR spectroscopy and thermal analysis confirmed the formation of random copolymers with compositions matching initial monomer feed ratios and a single glass transition temperature. A bifunctional cooperative mechanism is proposed for the DBM-catalyzed copolymer
synthesis and characterization of hydrazone ligand and their metal complexesMUBASHIRA M
This slide mainly contain the synthesis, characterization of a few hydrazine based heterocyclic ligand such as hydralazone and phenyl hydralazone and also their metal complexes. so in this work, my aim is to synthesise the ligands; 2-thiophenecarboxylaldehydehydralazone and 2,3-butanedionephenylhydrazone. also to characterized the synthesised hydrazones by different physiochemical techniques.
Modulation of Flash-Induced Photosystem II Fluorescence by Events Occurring a...Igor Putrenko
This document discusses how events at the water-oxidizing complex (WOC) in photosystem II (PSII) can modulate PSII fluorescence. The key points are:
1) The decay of flash-induced PSII fluorescence was measured and showed three exponential decay components, reflecting different rates of QA- reoxidation.
2) Modification of the PSII donor side, such as changing pH or removing extrinsic proteins, affected both the period four oscillations in maximum fluorescence yield and the contribution of QA- reoxidation reactions.
3) Four-step oxidation of the manganese cluster was necessary but not sufficient to produce fluorescence modulation - oxygen evolution capacity was also required. However
Charge Transfer Complexation and Excited State Interactions in Porphyrin-Ag N...kamatlab
This document summarizes a study on the charge-transfer complexation and excited-state interactions between tetrakis(4-aminophenyl)porphyrin (TAPP) and silver nanoparticles. The amine groups of TAPP allow it to form charge-transfer complexes with silver nanoparticles, resulting in a red-shifted absorption band and chemical enhancement of the surface enhanced resonance Raman scattering signal. Time-resolved spectroscopy shows fast charge separation upon photoexcitation of the TAPP-silver nanoparticle complexes, followed by slower charge recombination.
this presentation describes light phase of photosynthesis. it explains Evidences for two phases, Photosynthetic unit & Harvesting of light energy, Emerson effect &two photosystem, Hill reaction & Photolysis /photo-oxidation of water, Redox potential & mechanism of light reaction, Cyclic photophosphorylation, Non- cyclic photophosphorylation .
Poly(3-hexylthiophene) (P3HT) forms nanowires on graphene oxide (GO) and reduced graphene oxide (RGO) surfaces through a crystallization process induced by the graphene sheets. Transmission electron microscopy and atomic force microscopy show that the P3HT nanowires grow from and connect individual RGO monolayers. Raman spectroscopy indicates an interaction between the P3HT and RGO that allows manipulation of the RGO's electrical properties. The composite of P3HT nanowires on RGO forms a supramolecular structure with potential for nano-electronic applications due to improved charge transport over the individual components.
The document summarizes research into reactions of trichlorophosphazene ([PCl2N]3) with oxygen-containing Lewis bases, with the goal of synthesizing [PON]3. Key findings include:
1) Reactions with HMPA and triethylphosphine oxide result in chlorine/oxygen exchange, forming intermediate salts that further react to give phosphazene products containing P3N3Cl4O fragments bound to the Lewis base.
2) The P3N3Cl4O fragment exhibits strong Lewis acidity based on its ability to form stable adducts and its Guttmann-Beckett acceptor number.
3) Reactions
Postfunctional approach to prepare second order nonlinear optical polyphophaz...NEWLINE Marketing
This document describes a new synthetic strategy for preparing polyphosphazene polymers with second-order nonlinear optical properties. The strategy involves first producing polyphosphazenes containing aniline or indole side chains, then performing a post-azo coupling reaction to attach sulfonyl-based chromophores to the side chains, yielding polymers P3, P4, and P5. These polymers exhibit good solubility and thermal stability, with absorption maxima blue-shifted compared to similar chromophores containing nitro groups. Poled films of P3 and P4 showed second-order nonlinear optical coefficients of 27 and 18 pm/V, respectively.
Methods of Determining Reaction Mechanisms - Andria D'SouzaBebeto G
This document discusses various methods used to determine reaction mechanisms, including isotopic labeling techniques, stereochemical evidence, crossover experiments, identification of products, and identification of reaction intermediates. Isotopic labeling involves replacing atoms with isotopes like deuterium or carbon-13 to follow the reaction path. Stereochemical evidence from chiral reactants and products can indicate SN1 or SN2 mechanisms. Crossover experiments use non-identical reactants to study intramolecular vs intermolecular rearrangements. Identification of products and intermediates through spectroscopy, isolation, or trapping with reagents provides clues about reaction steps.
Perfluorocyclopentenyl (PFCP) Aryl Ether Polymers via Polycondensation of Oct...Babloo Sharma, Ph.D.
A unique class of aromatic ether polymers
containing perfluorocyclopentenyl (PFCP) enchainment was
prepared from the simple step growth polycondensation of
commercial bisphenols and octafluorocyclopentene (OFCP)
in the presence of triethylamine. Model studies indicate that
the second addition/elimination on OFCP is fast and poly-
condensation results in linear homopolymers and copolymers
without side products. The synthesis of bis(heptafluoro-
cyclopentenyl) aryl ether monomers and their condensation
with bisphenols further led to PFCP copolymers with alternating structures. This new class of semifluorinated polymers exhibit surprisingly high crystallinity in some cases and excellent thermal stability.
This document summarizes an investigation into using an enzymatic catalyst to catalyze the esterification of telechelic polymers, specifically poly(butadiene) and poly(ethylene oxide), in order to generate macromolecular chain transfer agents (CTAs) for synthesizing block copolymers. Experiments were conducted to esterify a hydroxyl-functionalized poly(butadiene) with a carboxylic acid functional RAFT agent using Novozym 435 catalyst. NMR and GPC analysis indicated some esterification occurred, though the molecular weight increase was small. More investigation is needed to optimize the reaction conditions to fully synthesize the macromolecular CTA. The goal is to develop a mild method to
IEC TECHNOLOGY Presentation February 2016Mari Kimura
IEC is an innovative nano technology with hundreds of applications to help the environment, Some of the applications can be used to remove oil from water, desalinize sea water into potable water, material for renewable energy. The material is recyclable and cost efficient to use.
Thermatic simulation platform for nano materials design in kistKIST
This slides introduce the web based thematic materials design platform developed in the Computational Science Center at KIST. This platform is to provide an easy-to-use materials simulation environment where people can perform various advanced simulations using the workflows very similar to those of the real experiment. These platforms were designed to reduce the entrance barrier to the complicated materials simulation using the high performance cluster computer. We are anticipating that these platforms will become robust R&D tool to design novel (nano) materials.
Nanotechnology involves manipulating materials at the nanoscale (1-100 nm) to create structures with novel properties. There are different classifications of nanostructures based on their dimensions, including zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D). Nanotechnology has applications in medicine such as drug delivery and tissue engineering, information/communication such as memory storage and displays, heavy industry such as catalysis, and consumer goods such as foods and cosmetics. Environmental applications include using nanoparticles for carbon capture, pollutant sensors, heavy metal remediation, and wastewater treatment.
Gas chromatography is a technique used to separate mixtures based on differences in polarity. It involves injecting a sample into a column containing a stationary phase, then using an inert gas mobile phase to carry the separated components out of the column, where they are detected individually. Key aspects include using an inert gas like helium as the mobile phase, a coated solid or liquid stationary phase in the column, and detectors that can identify separated components as they exit the column. Gas chromatography is useful for separating compounds that are thermally stable up to 300°C and allows for both qualitative and quantitative analysis of sample mixtures.
The document reports on an experimental study to determine the pKa (acid dissociation constant) of perfluorooctanoic acid (PFOA) using potentiometric titration in a water-methanol mixed solvent system. The study found:
1) The pKa of monomeric PFOA was determined to be 3.8 ± 0.1. This value is important for understanding the environmental fate of PFOA as both its ionized and non-ionized forms have different physicochemical properties.
2) The pKa was suppressed to around 2.3 at higher PFOA concentrations due to aggregation of its conjugate base. Many previous studies measured partitioning coefficients at concentrations above environmental levels,
This document discusses spectroscopy problem solving techniques including:
1) Chemical shifts and how equivalent protons will have the same shift and not couple.
2) Identifying the number of signals in a spectrum by considering equivalent protons.
3) Examples of assigning proton and carbon signals in spectra of compounds like ethylacetate and determining structures.
4) Factors that influence chemical shifts like functional groups and solvents.
5) Details on 13C NMR spectra and how coupling to protons is observed but can be removed through decoupling.
This document discusses the synthesis and characterization of three-ring mesogens with a terminal dimethylamino group. Key findings include:
1. Three mesogens were synthesized with varying alkyl chain lengths. Differential scanning calorimetry and polarized optical microscopy showed the compounds exhibited nematic and smectic A phases.
2. X-ray diffraction of one compound (DdIMPDB) surprisingly found an interdigitated smectic A layer organization, which is uncommon for dimethylamino-based mesogens.
3. Density functional theory calculations and NMR spectroscopy were used to determine molecular geometry and carbon chemical shifts for structural analysis. Photophysical properties also indicated intramolecular charge transfer interactions.
4. Solid-
The document summarizes the preparation and characterization of a novel luminescent terbium inorganic/organic hybrid material. 4-tert-butylbenzoic acid was modified with 3-aminopropyl trimethoxysilane to create a ligand (TBBA-APMS) that can both coordinate with terbium ions and undergo a sol-gel reaction with TEOS. This resulted in a hybrid material (Tb-TBBA-APMS) with bonds between Tb-O and Si-O. Characterization with UV-Vis, fluorescence and phosphorescence spectroscopy confirmed energy transfer between the ligand and terbium, producing strong terbium luminescence.
This doctoral thesis uses computational methods like density functional theory and molecular dynamics simulations to study the structural and functional role of cytochrome P450 enzymes. It investigates the metabolism of various substrates by CYP3A4 and CYP450 enzymes to understand reaction pathways and influence of substrate structure on reactivity. Specific reactions studied include hydroxylation of phenyl rings, morpholine rings, and camphor. Flexibility studies using the RIGIX program also examined how the protein environment modulates electronic structure and reactivity. The research provides new insights into CYP450 catalysis at the molecular level and could aid in drug design.
The document describes an in situ study using UV-visible spectroscopy to measure the kinetics of propane oxidative dehydrogenation (ODH) on vanadium oxide catalysts. Transients in UV-visible intensity during ODH reactions were analyzed using a surface reaction mechanism. Rate constants for the kinetically relevant C-H bond activation step were determined and compared to values from steady-state ODH rates. The ratio of these values provides a measure of the fraction of active vanadium sites. Reoxidation rate constants, which cannot be obtained from steady-state analysis, were also determined and found to be orders of magnitude larger than C-H bond activation rates.
This document summarizes research on the bulk copolymerization of L-lactide (LLA) and ε-caprolactone (CL) catalyzed by the organocatalyst dibenzoylmethane (DBM), which allows for the metal-free synthesis of random copolyesters. The researchers achieved good control over the ring-opening copolymerization as indicated by linear increases in molecular weight with conversion and dispersities below 1.5. NMR spectroscopy and thermal analysis confirmed the formation of random copolymers with compositions matching initial monomer feed ratios and a single glass transition temperature. A bifunctional cooperative mechanism is proposed for the DBM-catalyzed copolymer
synthesis and characterization of hydrazone ligand and their metal complexesMUBASHIRA M
This slide mainly contain the synthesis, characterization of a few hydrazine based heterocyclic ligand such as hydralazone and phenyl hydralazone and also their metal complexes. so in this work, my aim is to synthesise the ligands; 2-thiophenecarboxylaldehydehydralazone and 2,3-butanedionephenylhydrazone. also to characterized the synthesised hydrazones by different physiochemical techniques.
Modulation of Flash-Induced Photosystem II Fluorescence by Events Occurring a...Igor Putrenko
This document discusses how events at the water-oxidizing complex (WOC) in photosystem II (PSII) can modulate PSII fluorescence. The key points are:
1) The decay of flash-induced PSII fluorescence was measured and showed three exponential decay components, reflecting different rates of QA- reoxidation.
2) Modification of the PSII donor side, such as changing pH or removing extrinsic proteins, affected both the period four oscillations in maximum fluorescence yield and the contribution of QA- reoxidation reactions.
3) Four-step oxidation of the manganese cluster was necessary but not sufficient to produce fluorescence modulation - oxygen evolution capacity was also required. However
Charge Transfer Complexation and Excited State Interactions in Porphyrin-Ag N...kamatlab
This document summarizes a study on the charge-transfer complexation and excited-state interactions between tetrakis(4-aminophenyl)porphyrin (TAPP) and silver nanoparticles. The amine groups of TAPP allow it to form charge-transfer complexes with silver nanoparticles, resulting in a red-shifted absorption band and chemical enhancement of the surface enhanced resonance Raman scattering signal. Time-resolved spectroscopy shows fast charge separation upon photoexcitation of the TAPP-silver nanoparticle complexes, followed by slower charge recombination.
this presentation describes light phase of photosynthesis. it explains Evidences for two phases, Photosynthetic unit & Harvesting of light energy, Emerson effect &two photosystem, Hill reaction & Photolysis /photo-oxidation of water, Redox potential & mechanism of light reaction, Cyclic photophosphorylation, Non- cyclic photophosphorylation .
Poly(3-hexylthiophene) (P3HT) forms nanowires on graphene oxide (GO) and reduced graphene oxide (RGO) surfaces through a crystallization process induced by the graphene sheets. Transmission electron microscopy and atomic force microscopy show that the P3HT nanowires grow from and connect individual RGO monolayers. Raman spectroscopy indicates an interaction between the P3HT and RGO that allows manipulation of the RGO's electrical properties. The composite of P3HT nanowires on RGO forms a supramolecular structure with potential for nano-electronic applications due to improved charge transport over the individual components.
The document summarizes research into reactions of trichlorophosphazene ([PCl2N]3) with oxygen-containing Lewis bases, with the goal of synthesizing [PON]3. Key findings include:
1) Reactions with HMPA and triethylphosphine oxide result in chlorine/oxygen exchange, forming intermediate salts that further react to give phosphazene products containing P3N3Cl4O fragments bound to the Lewis base.
2) The P3N3Cl4O fragment exhibits strong Lewis acidity based on its ability to form stable adducts and its Guttmann-Beckett acceptor number.
3) Reactions
Postfunctional approach to prepare second order nonlinear optical polyphophaz...NEWLINE Marketing
This document describes a new synthetic strategy for preparing polyphosphazene polymers with second-order nonlinear optical properties. The strategy involves first producing polyphosphazenes containing aniline or indole side chains, then performing a post-azo coupling reaction to attach sulfonyl-based chromophores to the side chains, yielding polymers P3, P4, and P5. These polymers exhibit good solubility and thermal stability, with absorption maxima blue-shifted compared to similar chromophores containing nitro groups. Poled films of P3 and P4 showed second-order nonlinear optical coefficients of 27 and 18 pm/V, respectively.
Methods of Determining Reaction Mechanisms - Andria D'SouzaBebeto G
This document discusses various methods used to determine reaction mechanisms, including isotopic labeling techniques, stereochemical evidence, crossover experiments, identification of products, and identification of reaction intermediates. Isotopic labeling involves replacing atoms with isotopes like deuterium or carbon-13 to follow the reaction path. Stereochemical evidence from chiral reactants and products can indicate SN1 or SN2 mechanisms. Crossover experiments use non-identical reactants to study intramolecular vs intermolecular rearrangements. Identification of products and intermediates through spectroscopy, isolation, or trapping with reagents provides clues about reaction steps.
Perfluorocyclopentenyl (PFCP) Aryl Ether Polymers via Polycondensation of Oct...Babloo Sharma, Ph.D.
A unique class of aromatic ether polymers
containing perfluorocyclopentenyl (PFCP) enchainment was
prepared from the simple step growth polycondensation of
commercial bisphenols and octafluorocyclopentene (OFCP)
in the presence of triethylamine. Model studies indicate that
the second addition/elimination on OFCP is fast and poly-
condensation results in linear homopolymers and copolymers
without side products. The synthesis of bis(heptafluoro-
cyclopentenyl) aryl ether monomers and their condensation
with bisphenols further led to PFCP copolymers with alternating structures. This new class of semifluorinated polymers exhibit surprisingly high crystallinity in some cases and excellent thermal stability.
This document summarizes an investigation into using an enzymatic catalyst to catalyze the esterification of telechelic polymers, specifically poly(butadiene) and poly(ethylene oxide), in order to generate macromolecular chain transfer agents (CTAs) for synthesizing block copolymers. Experiments were conducted to esterify a hydroxyl-functionalized poly(butadiene) with a carboxylic acid functional RAFT agent using Novozym 435 catalyst. NMR and GPC analysis indicated some esterification occurred, though the molecular weight increase was small. More investigation is needed to optimize the reaction conditions to fully synthesize the macromolecular CTA. The goal is to develop a mild method to
IEC TECHNOLOGY Presentation February 2016Mari Kimura
IEC is an innovative nano technology with hundreds of applications to help the environment, Some of the applications can be used to remove oil from water, desalinize sea water into potable water, material for renewable energy. The material is recyclable and cost efficient to use.
Thermatic simulation platform for nano materials design in kistKIST
This slides introduce the web based thematic materials design platform developed in the Computational Science Center at KIST. This platform is to provide an easy-to-use materials simulation environment where people can perform various advanced simulations using the workflows very similar to those of the real experiment. These platforms were designed to reduce the entrance barrier to the complicated materials simulation using the high performance cluster computer. We are anticipating that these platforms will become robust R&D tool to design novel (nano) materials.
Nanotechnology involves manipulating materials at the nanoscale (1-100 nm) to create structures with novel properties. There are different classifications of nanostructures based on their dimensions, including zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D). Nanotechnology has applications in medicine such as drug delivery and tissue engineering, information/communication such as memory storage and displays, heavy industry such as catalysis, and consumer goods such as foods and cosmetics. Environmental applications include using nanoparticles for carbon capture, pollutant sensors, heavy metal remediation, and wastewater treatment.
Photo chemistry7 identifying chemistry in our worldsunkyung
This document defines key chemistry concepts such as matter, elements, compounds, and mixtures. It provides examples to illustrate these concepts, such as how air is a gas and matter, and how compounds like nitrogen oxide are formed from multiple elements. The document also distinguishes between physical and chemical changes, giving examples of each like water changing state through heating and cooling, and salt dissolving in water.
This document is a table of contents for a chemistry textbook about identifying chemistry in the world. It lists various chemistry concepts and terms like matter, elements, compounds, physical and chemical changes. Each term links to a page explaining that concept in more detail with examples and photos.
The document presents information on nanotechnology and nanomaterials from a presentation. It defines nanotechnology as the study and manipulation of matter at the nanoscale, or one billionth of a meter. The presentation discusses the history of nanotechnology, approaches to working at the nanoscale, examples of nanomaterials like carbon nanotubes and buckyballs, advantages for applications in mechanics, computing, pollution cleanup and medicine, and implications for health, safety, and potential doomsday scenarios involving runaway self-replication of nanobots.
Recent Developments in the Adoption of Nano-Technology for Electronic ComponentsBrian Foster
The document discusses recent developments in the adoption of nano-technology for electronic components. It covers major trends like higher operating temperatures and frequencies. It also discusses various nano powder synthesis approaches and enabling materials like barium titanate and nano metal powders. These materials allow for smaller, lower cost, and higher performance electronic devices with applications in areas like energy storage, automotive, and consumer electronics.
the photo chemistry of ligand field is very important to have an idea for the intrinsic properties of different coordination compound, and the electronic properties such as, LMCT,LLCT, MLCH etc..........
1. Photochemistry is the study of chemical reactions caused by the absorption of light. It involves photochemical reactions, which require light for initiation, as well as photophysical processes during the de-excitation of excited molecules.
2. Key concepts in photochemistry include Grotthuss-Draper law, Lambert's law, Beer's law, and Stark-Einstein law of photochemical equivalence. Quantum yield determines the efficiency of photochemical reactions.
3. Photochemistry examines differences between photochemical and thermal reactions. It also explores photochemical processes like fluorescence, phosphorescence, internal conversion, and intersystem crossing depicted in Jablonski diagrams.
This document outlines the course roadmap for an organometallic chemistry course. It will cover the basics of organometallic chemistry including electron counting, main group and transition metal chemistry, and common reaction types like insertion, elimination, and oxidative addition/reductive elimination. As an example, it will discuss the industrial Monsanto process for producing acetic acid catalytically using a rhodium complex and methanol. Students will learn to understand and explain organometallic reactions and current research papers.
This document provides definitions and examples of key concepts in the classification and changes of matter. It defines matter, non-matter, pure substances, elements, compounds, mixtures, homogeneous and heterogeneous mixtures, physical properties like mass, volume, density and states of matter. It also distinguishes between physical and chemical changes, providing examples of each type of change.
This document discusses phosphorescence spectroscopy and provides information about molecular luminescence, including fluorescence and phosphorescence. It describes the basic principles, including how molecules are excited to higher energy states and then emit light as they relax to lower energy states. Singlet and triplet states are defined, along with electronic and vibrational energy levels. Electron transitions like internal conversion, intersystem crossing, and vibrational relaxation are explained. Instrumentation for measuring phosphorescence is also summarized, including components like light sources, monochromators, sample cells, and detectors. Some applications of phosphorescence are mentioned, such as in television screens, pigments, and glow-in-the-dark toys.
This document summarizes a seminar on photochemistry presented by Mr. Dinkar B. Kamkhede. The seminar covered topics including the definition of photochemistry, laws of photochemistry, mechanisms of light absorption, electronic transitions, photosensitization, and the Jablonski diagram. It discussed how photochemical reactions are initiated by the absorption of light energy and explained concepts such as quantum yield. The seminar provided an overview of the key concepts and processes in photochemistry.
This document provides an introduction to nanomaterials, including definitions and examples. It discusses that nanomaterials are between 1-100 nanometers in at least one dimension, exhibiting unique optical, electrical, and magnetic properties. Some nanomaterials occur naturally, but many are engineered for use in products like sunscreens, electronics, and medicine. Common engineered nanomaterials discussed include titanium dioxide, silicon dioxide, zinc oxide, silver, aluminum oxide, zirconium oxide, tungsten oxide, and carbon nanotubes. The document outlines several properties and applications of these nanomaterials when used in concrete and other construction materials.
This document discusses various techniques for synthesizing nanoparticles, including sol-gel synthesis, colloidal precipitation, co-precipitation, combustion technique, hydrothermal technique, high energy ball milling, and sonochemistry. It provides details on specific methods like the Frens method for synthesizing gold nanoparticles, co-precipitation reaction for iron oxide nanoparticles using FeCl3 and benzene tetracarboxylic acid, combustion synthesis using lithium nitrate and bismuth nitrate with urea and glycerol, and hydrothermal treatment for titanium dioxide nanoparticles. The advantages of these techniques in producing nanoparticles at low temperatures and with good control of properties are highlighted.
Dye-sensitized solar cells (DSSCs) convert sunlight to electricity via a photosensitizer dye attached to a semiconductor (typically titanium dioxide). When light is absorbed by the dye, electrons are injected into the semiconductor and collected at the anode. The dye is regenerated by accepting electrons from an electrolyte solution, and the process continues. Michael Gratzel invented the DSSC in 1991. DSSCs can be made flexible and are less expensive than silicon solar cells. Ruthenium-based dyes like N719 are most commonly used but research seeks replacements like organic or natural dyes.
This document discusses nano materials and their properties. It defines nano materials as materials with at least one dimension between 1-100 nanometers. The key properties of nano materials are an increased surface area to volume ratio and quantum confinement effects. Due to these factors, nano materials exhibit significantly different physical, chemical, electrical and magnetic properties compared to bulk materials. Some examples of these differences include lower melting points, increased chemical reactivity, discrete energy levels, and reduced magnetic moments. The document concludes by outlining several applications of nano materials in industries like chemicals, automotive, medicine, electronics, energy and cosmetics.
Nano-technology (Biology, Chemistry, and Physics applied)Muhammad Yossi
Nano-science involves research to discover new behaviors and properties of materials with dimensions at the nanoscale which ranges roughly from 1 to 100 nanometers(nm). Nanotechnology is the way discoveries made at the nanoscale are put to work. Nanotechnology is more than throwing together a batch of nanoscale materials - it requires the ability to manipulate and control those materials in a useful way. This slides contain a bit of History of Nanotechnology, The Application of Nanotechnology from the Previouses Centuries, The Applications of Nanotechnology in the Next Generation, The Advantages and The Disadvantages.
Nanotechnology involves creating and manipulating materials on an atomic or molecular scale. It can produce materials with novel properties due to their small size. The document discusses various applications of nanotechnology in areas like engineering, medicine, textiles and more. It also describes techniques for synthesizing and characterizing nanomaterials, such as top-down methods that break down bulk materials and bottom-up methods that build materials up atom by atom.
This document provides an overview of nanotechnology and its history. It discusses key terms like nanoscale and nanotechnology. Some important developments include the discovery of buckyballs in 1980 and carbon nanotubes in 1991. The document also outlines several types of nanotechnology like nano-materials, nano-electronics, nano-robotics and their applications. Nanotechnology is seen as having great potential impacts across many fields like engineering, electronics, medicine and more.
This document summarizes a solid-state nuclear magnetic resonance study of molecular dynamics in the polymer MEH-PPV. The main findings are:
1) Slow motions (1 Hz-1 kHz) in the polymer backbone involve small angle librations over a temperature range of 213-323 K.
2) Two motional regimes were identified in the side chains: intermediate motions (1-50 kHz) for all chemical groups, and additional fast rotation (100 MHz) for terminal CH3 groups.
3) A correlation was observed between motional parameters determined from NMR and changes in photoluminescence behavior with temperature.
Brief view: Reaction Control by Electron Spin Manipulation & other worksMasaharu Okazaki
Main works of Masaharu Okazaki are presented briefly. 1) Reaction of radical-pair intermediates produced in a nano-cage (mainly as the photo-reaction intermediates) can be controlled by manipulating the spin state. 2) Alcohol molecules flow collectively in the nanochannel of MCM-41. Evidences are given by the spin probe and radical-pair probe techniques.
Para-Chlorophenoxyacetic Acid Lab ReportErika Nelson
Paragraph 1: The goal of this experiment was to study the SN1 reaction mechanism using 2-bromo-2-methylpropane and sodium iodide in acetone. An SN1 reaction involves the formation of a carbocation intermediate. 2-bromo-2-methylpropane was used as the substrate since the tertiary carbocation formed would be stable. Sodium iodide served as the nucleophile and acetone was used as the solvent to stabilize the carbocation.
Paragraph 2: The reaction was monitored over several time intervals by removing aliquots and analyzing by gas chromatography. The
NMR spectroscopy is a technique used to determine the structure of organic molecules. It works by applying a strong magnetic field to atomic nuclei, causing them to absorb radio frequencies that are dependent on their chemical environment. This allows differentiation of chemically distinct hydrogen atoms. The frequency of absorption is measured in parts per million relative to a standard, and is influenced by factors like neighboring bonds, substituents, and spin-spin coupling between nuclei. NMR can be used to determine a compound's empirical formula, identify different types of protons, count the number of protons in each type, and elucidate relative stereochemistry and conformations.
On the-mechanism-of-proton-conductivity-in-h-sub3sub o-sbteo-sub6sub_2012_jou...Javier Lemus Godoy
This document summarizes a study investigating the proton conductivity mechanism in H3OSbTeO6 using neutron diffraction, quasielastic neutron scattering, and NMR experiments at various temperatures. H3OSbTeO6 has an outstanding proton conductivity even at room temperature. It consists of a three-dimensional framework of corner-sharing SbO6 and TeO6 octahedra forming cages where H3O+ ions are located. Three types of ion motion were observed: rotations of the H3O group, jumps between equivalent positions within cages, and long-range translational diffusion between cages. Structural changes reflected the onset of ionic conductivity. Details of the complex diffusion mechanism are provided.
The document discusses the detection of the oxyl radical (Ti-O•) catalytic intermediate in water oxidation at an n-SrTiO3/aqueous interface using theoretical calculations and ultrafast infrared spectroscopy. It finds that the oxyl radical causes the oxygen atom directly below it to decouple from the substrate, creating a localized subsurface Ti-O stretch vibration that is detected. This vibration couples to both solvent water librations and electron dynamics in the solid, allowing it to track the catalytic cycle at the molecular level. The identification of this subsurface vibration provides direct evidence for the transformation of charge into a nascent catalytic intermediate and a new approach for studying catalytic cycles dynamically at solid-liquid interfaces.
1. 1H NMR spectroscopy is a technique used to analyze compounds by detecting hydrogen nuclei in a magnetic field. It provides information about functional groups, number of nuclei, and structure of compounds.
2. The principle involves hydrogen nuclei absorbing radio frequencies matching their Larmor frequency in an applied magnetic field. This absorption is measured to produce an NMR spectrum.
3. Factors like electronegativity, magnetic anisotropy, and spin-spin coupling influence the chemical shifts observed on the NMR spectrum, allowing identification of functional groups and structure elucidation.
Molecular dynamics-of-ions-in-two-forms-of-an-electroactive-polymerDarren Martin Leith
This document summarizes molecular dynamics simulations of two forms of an electroactive polymer interacting with ions. In one simulation, an amphiphilic polymer forms a charged monolayer interface between a vacuum and an aqueous layer containing ions. The stability of the monolayer under hydrostatic pressure and charge imbalance is investigated. In another simulation, a polythiophene oligomer is twisted into a helix serving as an ion channel between two aqueous regions separated by a phospholipid bilayer membrane.
CHE-504 Lecture 3 Basics of NMR Spectroscopy by Dr. Charu C. Pant.pdfTahreemFatima43565
This document provides an introduction to NMR spectroscopy. It discusses key concepts such as NMR active nuclei, resonance and relaxation phenomena, nuclear shielding and deshielding, chemically equivalent and non-equivalent protons, chemical shift, spin-spin splitting and coupling constants. It also outlines some applications of NMR spectroscopy such as distinguishing structural isomers and detecting hydrogen bonding. The document concludes by discussing factors that are important for interpreting 1H NMR spectra such as chemical shift, spin multiplicity, coupling constants and integration.
Examination of methods to determine free-ion diffusivity and number density f...Weston Bell
This document summarizes a study that critically examines methods for determining free ion diffusivity and number density from analysis of electrode polarization. It shows that the commonly used Macdonald-Trukhan model of electrode polarization analysis fails to provide reasonable values at high salt concentrations. An empirical correction is proposed but caution is warranted as there is no solid theoretical justification. A variety of electrolyte materials, including polymer electrolytes, aqueous and nonaqueous solutions, and ionic liquids, were examined using dielectric spectroscopy and the results were compared to pulsed-field gradient NMR measurements.
Fluorescence quenching of 5-methyl-2-phenylindole (MPI) by carbon tetrachlori...IOSR Journals
The fluorescence quenching of 5-methyl-2-phenylindole (MPI) by carbon tetrachloride by steady state in different solvents, and by transient method in benzene has been carried out at room temperature. The Stern–Volmer (SV) plot has been found to be non-linear with a positive deviation for all the solvents studied. In order to interpret these results we have invoked the ground state complex and sphere of action static quenching models. Using these models various rate parameters have been determined. The magnitudes of these parameters imply that sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation in the SV plots is attributed to the static and dynamic quenching. Further, from the studies of temperature dependence of rate parameters and lifetime measurements, it could be explained that the positive deviation is due to the presence of a small static quenching component in the overall dynamic quenching. With the use of finite sink approximation model, it was possible to check whether these bimolecular reactions as diffusion limited and to estimate independently distance parameter R′ and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R′ and D with the values of the encounter distance R and the mutual diffusion coefficient D determined using the Edward's empirical relation and Stokes–Einstein relation.
The document summarizes a study that investigated how the photoluminescence quantum yield of lead selenide quantum dots is affected by increasing excitation energy. Three samples of PbSe quantum dots were synthesized with different diameters and characterized. It was found that the quantum yield decreased as the excitation energy increased, likely due to the formation of multi-exciton states within single quantum dots that lead to non-radiative Auger processes. The quantum yield was measured using an integrating sphere method and by analyzing absorption and emission spectra of the samples excited at different wavelengths. The results supported the expectation that higher excitation energies reduce quantum yield.
This document summarizes a study of the magnetic properties of the sodium iron phosphite compound NaFe3(HPO3)2(H2PO3)6. Key findings include:
1) The compound develops ferrimagnetic order below 9.5 K and exhibits a 1/3 magnetization plateau that extends to 8T, with linear increase in magnetization above this field until saturation at 27T.
2) There are two nonequivalent iron sites revealed by Mossbauer spectroscopy with a 2:1 ratio.
3) High-frequency ESR and other measurements indicate weak magnetic anisotropy and short-range spin order above the ordering temperature.
4) DFT calculations show the
Chromatography is a separation technique that separates components of a mixture based on their interactions with two phases - a stationary phase and a mobile phase. There are various types of chromatography depending on the nature of the stationary and mobile phases used, including gas chromatography, liquid chromatography, and supercritical fluid chromatography. Chromatography has a long history dating back to 1906 and has become an essential analytical technique used across various fields like chemistry and biochemistry.
The document discusses perovskite solar cells. It begins by defining perovskites and their crystal structure. It then discusses several important studies on perovskite solar cells that improved their efficiency over time, including studies published in 2012, 2013, 2014 and 2015 that achieved efficiencies up to 19.3%. It also reviews factors that affect the performance and stability of perovskite solar cells, such as humidity, UV light, annealing temperature, and the choice of electron transport material. In conclusion, it summarizes that perovskite solar cells have advantages over traditional silicon solar cells like easier processing, higher efficiency potential, flexibility and lower cost.
1) The document describes research into a light-responsive azobenzene compound (compound 4) that can disrupt phospholipid membranes.
2) Compound 4 undergoes reversible trans-cis isomerization when exposed to UV or visible light. Testing showed the cis isomer is more membrane-interactive than the trans isomer.
3) Interactions between the cis/trans isomers and liposomes of different phospholipids were examined. The cis isomer caused more lysis than the trans isomer in all cases. This suggests compound 4 could be optimized for photodynamic therapy applications.
48 Measurement of the Σ beam asymmetry for the ω photo-production off the pro...Cristian Randieri PhD
Measurement of the Σ beam asymmetry for the ω photo-production off the proton and the neutron at GRAAL - June 2013
di V. Vegna, A. D'Angelo, O. Bartalini, V. Bellini, J. P. Boquet, M. Capogni, L. E. Casano, M. Castoldi, F. Curciarello, V. De Leo, J. P. Didelez, R. Di Salvo, A. Fantini, D. Franco, G. Gervino, F. Ghio, G. Giardina, B. Girolami, A. Giusa, A. Lapik, P. Levi Sandri, A. Lleres, F. Mammoliti, G. Mandaglio, M. Manganaro, D. Moricciani, A. Mushkarenkov, V. Nedorezov, C. Randieri, D. Rebreyend, N. Rudnev, G. Russo, C. Schaerf, M. L. Sperduto, M. C. Sutera, A. Turinge, I. Zonta (2013)
Abstract
We report on new measurements of the beam asymmetry for ω photo-production on proton and neutron in Hydrogen and Deuterium targets from the GRAAL collaboration. The beam asymmetry values are extracted from the reaction threshold (E = 1.1 GeV in the free nucleon kinematics) up to 1.5 GeV of incoming photon energy. For the first time both the radiative and the three- pion decay channels are simultaneously investigated on the free proton. Results from the two decay channels are in agreement and provide important constraints for the determination of resonant state contributions to the ω production mechanism. First experimental results on the deuteron allow the extraction of the _ beam asymmetry on quasi-free nucleons. Comparison of the results for free and quasi-free kinematics on the proton shows a generally reasonable agreement, similar to the findings in pseudo-scalar meson photo-production reactions. For the first time measurements on quasi-free neutrons are available, showing that both the strength and the angular distributions of the beam asymmetry are sensibly different from the results on the proton target.
This document summarizes a study investigating the kinetics of the first hole transfer step in the photocatalytic water oxidation reaction at the interface between n-type strontium titanate (n-SrTiO3) and hydroxyl ions (OH-) in water. Using transient optical spectroscopy of a photoelectrochemical cell, the researchers were able to determine the kinetics as a function of the surface hole potential and separate the first hole transfer step from subsequent steps. They found the kinetics followed a single exponential dependence on surface hole potential, with time constants ranging from 3 ns to 8 ps over a 1 V change in potential. This allowed them to quantify the activation barrier for the first hole transfer step and extrapolate the rate constant when
This document reports on a study investigating the free radical reaction between alkanes and carbon tetrachloride in solution. Product studies and kinetic electron paramagnetic resonance methods were used. The following key points are made:
1) Trichloromethyl radicals abstracted hydrogen from simple alkanes like cyclopentane and cyclohexane with rate constants of around 60 M-1s-1 in solution, in good agreement with gas phase data.
2) However, rate constants for chlorine abstraction by alkyl radicals from carbon tetrachloride were around 104 M-1s-1 in solution, around two orders of magnitude higher than in the gas phase.
3) Possibilities for this effect
Similar to Revised primary photochemistry9na_fin (20)
"Frontline Battles with DDoS: Best practices and Lessons Learned", Igor IvaniukFwdays
At this talk we will discuss DDoS protection tools and best practices, discuss network architectures and what AWS has to offer. Also, we will look into one of the largest DDoS attacks on Ukrainian infrastructure that happened in February 2022. We'll see, what techniques helped to keep the web resources available for Ukrainians and how AWS improved DDoS protection for all customers based on Ukraine experience
Conversational agents, or chatbots, are increasingly used to access all sorts of services using natural language. While open-domain chatbots - like ChatGPT - can converse on any topic, task-oriented chatbots - the focus of this paper - are designed for specific tasks, like booking a flight, obtaining customer support, or setting an appointment. Like any other software, task-oriented chatbots need to be properly tested, usually by defining and executing test scenarios (i.e., sequences of user-chatbot interactions). However, there is currently a lack of methods to quantify the completeness and strength of such test scenarios, which can lead to low-quality tests, and hence to buggy chatbots.
To fill this gap, we propose adapting mutation testing (MuT) for task-oriented chatbots. To this end, we introduce a set of mutation operators that emulate faults in chatbot designs, an architecture that enables MuT on chatbots built using heterogeneous technologies, and a practical realisation as an Eclipse plugin. Moreover, we evaluate the applicability, effectiveness and efficiency of our approach on open-source chatbots, with promising results.
[OReilly Superstream] Occupy the Space: A grassroots guide to engineering (an...Jason Yip
The typical problem in product engineering is not bad strategy, so much as “no strategy”. This leads to confusion, lack of motivation, and incoherent action. The next time you look for a strategy and find an empty space, instead of waiting for it to be filled, I will show you how to fill it in yourself. If you’re wrong, it forces a correction. If you’re right, it helps create focus. I’ll share how I’ve approached this in the past, both what works and lessons for what didn’t work so well.
HCL Notes and Domino License Cost Reduction in the World of DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-and-domino-license-cost-reduction-in-the-world-of-dlau/
The introduction of DLAU and the CCB & CCX licensing model caused quite a stir in the HCL community. As a Notes and Domino customer, you may have faced challenges with unexpected user counts and license costs. You probably have questions on how this new licensing approach works and how to benefit from it. Most importantly, you likely have budget constraints and want to save money where possible. Don’t worry, we can help with all of this!
We’ll show you how to fix common misconfigurations that cause higher-than-expected user counts, and how to identify accounts which you can deactivate to save money. There are also frequent patterns that can cause unnecessary cost, like using a person document instead of a mail-in for shared mailboxes. We’ll provide examples and solutions for those as well. And naturally we’ll explain the new licensing model.
Join HCL Ambassador Marc Thomas in this webinar with a special guest appearance from Franz Walder. It will give you the tools and know-how to stay on top of what is going on with Domino licensing. You will be able lower your cost through an optimized configuration and keep it low going forward.
These topics will be covered
- Reducing license cost by finding and fixing misconfigurations and superfluous accounts
- How do CCB and CCX licenses really work?
- Understanding the DLAU tool and how to best utilize it
- Tips for common problem areas, like team mailboxes, functional/test users, etc
- Practical examples and best practices to implement right away
Programming Foundation Models with DSPy - Meetup SlidesZilliz
Prompting language models is hard, while programming language models is easy. In this talk, I will discuss the state-of-the-art framework DSPy for programming foundation models with its powerful optimizers and runtime constraint system.
zkStudyClub - LatticeFold: A Lattice-based Folding Scheme and its Application...Alex Pruden
Folding is a recent technique for building efficient recursive SNARKs. Several elegant folding protocols have been proposed, such as Nova, Supernova, Hypernova, Protostar, and others. However, all of them rely on an additively homomorphic commitment scheme based on discrete log, and are therefore not post-quantum secure. In this work we present LatticeFold, the first lattice-based folding protocol based on the Module SIS problem. This folding protocol naturally leads to an efficient recursive lattice-based SNARK and an efficient PCD scheme. LatticeFold supports folding low-degree relations, such as R1CS, as well as high-degree relations, such as CCS. The key challenge is to construct a secure folding protocol that works with the Ajtai commitment scheme. The difficulty, is ensuring that extracted witnesses are low norm through many rounds of folding. We present a novel technique using the sumcheck protocol to ensure that extracted witnesses are always low norm no matter how many rounds of folding are used. Our evaluation of the final proof system suggests that it is as performant as Hypernova, while providing post-quantum security.
Paper Link: https://eprint.iacr.org/2024/257
For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2024/06/how-axelera-ai-uses-digital-compute-in-memory-to-deliver-fast-and-energy-efficient-computer-vision-a-presentation-from-axelera-ai/
Bram Verhoef, Head of Machine Learning at Axelera AI, presents the “How Axelera AI Uses Digital Compute-in-memory to Deliver Fast and Energy-efficient Computer Vision” tutorial at the May 2024 Embedded Vision Summit.
As artificial intelligence inference transitions from cloud environments to edge locations, computer vision applications achieve heightened responsiveness, reliability and privacy. This migration, however, introduces the challenge of operating within the stringent confines of resource constraints typical at the edge, including small form factors, low energy budgets and diminished memory and computational capacities. Axelera AI addresses these challenges through an innovative approach of performing digital computations within memory itself. This technique facilitates the realization of high-performance, energy-efficient and cost-effective computer vision capabilities at the thin and thick edge, extending the frontier of what is achievable with current technologies.
In this presentation, Verhoef unveils his company’s pioneering chip technology and demonstrates its capacity to deliver exceptional frames-per-second performance across a range of standard computer vision networks typical of applications in security, surveillance and the industrial sector. This shows that advanced computer vision can be accessible and efficient, even at the very edge of our technological ecosystem.
Main news related to the CCS TSI 2023 (2023/1695)Jakub Marek
An English 🇬🇧 translation of a presentation to the speech I gave about the main changes brought by CCS TSI 2023 at the biggest Czech conference on Communications and signalling systems on Railways, which was held in Clarion Hotel Olomouc from 7th to 9th November 2023 (konferenceszt.cz). Attended by around 500 participants and 200 on-line followers.
The original Czech 🇨🇿 version of the presentation can be found here: https://www.slideshare.net/slideshow/hlavni-novinky-souvisejici-s-ccs-tsi-2023-2023-1695/269688092 .
The videorecording (in Czech) from the presentation is available here: https://youtu.be/WzjJWm4IyPk?si=SImb06tuXGb30BEH .
Generating privacy-protected synthetic data using Secludy and MilvusZilliz
During this demo, the founders of Secludy will demonstrate how their system utilizes Milvus to store and manipulate embeddings for generating privacy-protected synthetic data. Their approach not only maintains the confidentiality of the original data but also enhances the utility and scalability of LLMs under privacy constraints. Attendees, including machine learning engineers, data scientists, and data managers, will witness first-hand how Secludy's integration with Milvus empowers organizations to harness the power of LLMs securely and efficiently.
Northern Engraving | Nameplate Manufacturing Process - 2024Northern Engraving
Manufacturing custom quality metal nameplates and badges involves several standard operations. Processes include sheet prep, lithography, screening, coating, punch press and inspection. All decoration is completed in the flat sheet with adhesive and tooling operations following. The possibilities for creating unique durable nameplates are endless. How will you create your brand identity? We can help!
5th LF Energy Power Grid Model Meet-up SlidesDanBrown980551
5th Power Grid Model Meet-up
It is with great pleasure that we extend to you an invitation to the 5th Power Grid Model Meet-up, scheduled for 6th June 2024. This event will adopt a hybrid format, allowing participants to join us either through an online Mircosoft Teams session or in person at TU/e located at Den Dolech 2, Eindhoven, Netherlands. The meet-up will be hosted by Eindhoven University of Technology (TU/e), a research university specializing in engineering science & technology.
Power Grid Model
The global energy transition is placing new and unprecedented demands on Distribution System Operators (DSOs). Alongside upgrades to grid capacity, processes such as digitization, capacity optimization, and congestion management are becoming vital for delivering reliable services.
Power Grid Model is an open source project from Linux Foundation Energy and provides a calculation engine that is increasingly essential for DSOs. It offers a standards-based foundation enabling real-time power systems analysis, simulations of electrical power grids, and sophisticated what-if analysis. In addition, it enables in-depth studies and analysis of the electrical power grid’s behavior and performance. This comprehensive model incorporates essential factors such as power generation capacity, electrical losses, voltage levels, power flows, and system stability.
Power Grid Model is currently being applied in a wide variety of use cases, including grid planning, expansion, reliability, and congestion studies. It can also help in analyzing the impact of renewable energy integration, assessing the effects of disturbances or faults, and developing strategies for grid control and optimization.
What to expect
For the upcoming meetup we are organizing, we have an exciting lineup of activities planned:
-Insightful presentations covering two practical applications of the Power Grid Model.
-An update on the latest advancements in Power Grid -Model technology during the first and second quarters of 2024.
-An interactive brainstorming session to discuss and propose new feature requests.
-An opportunity to connect with fellow Power Grid Model enthusiasts and users.
Monitoring and Managing Anomaly Detection on OpenShift.pdfTosin Akinosho
Monitoring and Managing Anomaly Detection on OpenShift
Overview
Dive into the world of anomaly detection on edge devices with our comprehensive hands-on tutorial. This SlideShare presentation will guide you through the entire process, from data collection and model training to edge deployment and real-time monitoring. Perfect for those looking to implement robust anomaly detection systems on resource-constrained IoT/edge devices.
Key Topics Covered
1. Introduction to Anomaly Detection
- Understand the fundamentals of anomaly detection and its importance in identifying unusual behavior or failures in systems.
2. Understanding Edge (IoT)
- Learn about edge computing and IoT, and how they enable real-time data processing and decision-making at the source.
3. What is ArgoCD?
- Discover ArgoCD, a declarative, GitOps continuous delivery tool for Kubernetes, and its role in deploying applications on edge devices.
4. Deployment Using ArgoCD for Edge Devices
- Step-by-step guide on deploying anomaly detection models on edge devices using ArgoCD.
5. Introduction to Apache Kafka and S3
- Explore Apache Kafka for real-time data streaming and Amazon S3 for scalable storage solutions.
6. Viewing Kafka Messages in the Data Lake
- Learn how to view and analyze Kafka messages stored in a data lake for better insights.
7. What is Prometheus?
- Get to know Prometheus, an open-source monitoring and alerting toolkit, and its application in monitoring edge devices.
8. Monitoring Application Metrics with Prometheus
- Detailed instructions on setting up Prometheus to monitor the performance and health of your anomaly detection system.
9. What is Camel K?
- Introduction to Camel K, a lightweight integration framework built on Apache Camel, designed for Kubernetes.
10. Configuring Camel K Integrations for Data Pipelines
- Learn how to configure Camel K for seamless data pipeline integrations in your anomaly detection workflow.
11. What is a Jupyter Notebook?
- Overview of Jupyter Notebooks, an open-source web application for creating and sharing documents with live code, equations, visualizations, and narrative text.
12. Jupyter Notebooks with Code Examples
- Hands-on examples and code snippets in Jupyter Notebooks to help you implement and test anomaly detection models.
Skybuffer SAM4U tool for SAP license adoptionTatiana Kojar
Manage and optimize your license adoption and consumption with SAM4U, an SAP free customer software asset management tool.
SAM4U, an SAP complimentary software asset management tool for customers, delivers a detailed and well-structured overview of license inventory and usage with a user-friendly interface. We offer a hosted, cost-effective, and performance-optimized SAM4U setup in the Skybuffer Cloud environment. You retain ownership of the system and data, while we manage the ABAP 7.58 infrastructure, ensuring fixed Total Cost of Ownership (TCO) and exceptional services through the SAP Fiori interface.
1. Primary Photochemistry of Nitrated Aromatic Compounds:
Excited State Dynamics and NO· Dissociation from 9-
Nitroanthracene
Eddy F. Plaza-Medina, William Rodríguez-Córdoba, Rodrigo Morales-Cueto and Jorge
Peon*
Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior,
Ciudad Universitaria, México, 04510, D.F., México.
jpeon@servidor.unam.mx
1
2. ABSTRACT
We report results of femtosecond-resolved experiments which elucidate the time-scale for
the primary photoinduced events in the model nitroaromatic compound 9-nitroanthracene.
Through time-resolved fluorescence measurements, we observed the ultrafast decay of the
initially excited singlet state and through transient absorption experiments, we observed the
spectral evolution associated with the formation of the relaxed phosphorescent T1 state.
Additionally, we have detected for the first time, the accumulation of the anthryloxy radical
which results from the nitro-group rearrangement and NO· dissociation from photoexcited
9-nitroanthracene, a photochemical channel which occurs in parallel with the formation of
the phosphorescent state. The spectral evolution in this molecule is highly complex since
both channels take place in similar time-ranges of up to a few picoseconds. Despite this
complexity, our experiments provide the general time-scales in which the primary products
are formed. In addition, we include calculations at the time-dependent density functional
level of theory which distinguish the molecular orbitals responsible for the n−π∗ character
of the “receiver” vibronic triplet states that couple with the first singlet state and promote
the ultrafast transfer of population between the two manifolds. Comparisons with the
isoelectronic compounds anthracene-9-carboxylic acid and its conjugated base, which are
highly fluorescent, show that in these two compounds the near isoenergeticity of the S1
with an appropriate “receiver” triplet state is disrupted, providing support to the idea that a
specific energy coincidence is important for the ultrafast population of the triplet manifold,
prevalent in polycyclic nitrated aromatic compounds.
2
3. INTRODUCTION
Understanding the photochemistry and photophysics of nitroaromatic molecules is of great
importance since these compounds are significantly mutagenic and carcinogenic
environmental pollutants which’s natural decay from the atmosphere occurs through light-
induced reactions.1-6 NPAHs (nitrated polycyclic aromatic hydrocarbons) can appear in the
urban environment at concentrations as high as several ng/g.7-8 Such high levels of
accumulation are due to their formation pathways, which include both direct creation from
inefficient combustion,9-10 and from nitration reactions of polyaromatics with nitrite
radicals.11-12 Nitrated polyaromatics like 9-nitroanthracene (9-NA) are also interesting from
an applications point of view. Due to their capacity to photo-detach nitrogen oxide (NO·),
and form other highly bio-reactive intermediaries as aryloxy radicals (ArO·) or long-lived
triplet states (see below), these molecules have been suggested and tested as agents for
photodynamic therapies.13-15 Lastly, the high triplet yield of several of the NPAHs has been
used to develop polymerization schemes where the T1 state of nitroaromatics like p-
nitronaphthylaniline can act as a co-initiator in the photosensitized generation of free
radicals through reactions with a reducing agent.16-17
The photochemical reactivity of NPAHs is quite interesting and may involve both
direct channels (NO· release) or bimolecular reactions of their triplet states.18-20 The
primary photoinduced process with the highest yield in nitroaromatics is precisely the
formation of their phosphorescent triplet state. This pathway was identified from the early
experiments on 9-NA and some derivatives by the group of Hammanoue, who detected the
phosphorescent state emission, absorption and excitation spectra, as well as its population
3
4. decay kinetics in a series of experiments with nanosecond and picoseconds time resolution.
These characterizations were made both in low temperature matrices and in solution.21-24
The femtosecond and picosecond details of the singlet to triplet transition of nitroaromatics
have been studied in our research group, focusing in 1-nitronaphthalene as a case-study.25-26
From femtosecond-resolved emission and absorption experiments, it was directly
confirmed that the first singlet excited state of nitroaromatics of π−π∗ nature undergoes an
ultrafast intersystem crossing to the triplet manifold through the coupling to a “receiver”
triplet state which has contributions from n−π* transitions, making it an allowed transition
by El-Sayed’s rules.27-29 This upper triplet state then relaxes to the long lived
phosphorescent triplet state through internal conversion within the triplet manifold,
followed by vibrational relaxation and solvation.26,30 The efficiency of this photophysical
pathway, prevalent in most nitroaromatics, implies that they show no detectable
fluorescence in steady-state measurements, and therefore, femtosecond fluorescence up-
conversion experiments are required to detect and follow their singlet emission which has
decay components as short as a few tens of femtoseconds. In fact, the ability to couple to
nearly isoenergetic vibroelectronic states in the triplet manifold makes NPAHs, the organic
molecules with the highest intersystem crossing rates measured to date.25,31
The rapid manifold crossing of several of these compounds is, however, not the only
primary photochemical channel. From the early experiments by Chapman and later by
Hammanoue et al., it was recognized that in parallel with the aforementioned T1 formation,
some nitroaromatics like 9-NA,21-23,32-33 and 1-nitropyrene,34-35 undergo a nitro-group
rearrangement which leads to the release of NO· and the formation of an aryloxy radical
4
5. (Ar-O·). In the experiments on 9-NA by Chapmann et al., this minor channel was identified
as responsible for the formation of photoproducts like 10,10’-bianthrone, anthraquinone
and anthraquinone monoxime in acetone solution,32 and in experiments in alcohols, for
products like 9-anthrol. The same type of result has been confirmed for 1-nitropyrene in
recent studies by the groups of Arce and Crespo-Hernandez.34-35
In this contribution we explored the early photochemistry of 9-NA in ethanol
solution through direct measurements of the population evolution of the excited states and
the ArO· specie. This was accomplished through the combination of ultrafast fluorescence
measurements and transient absorption spectroscopy. As we will show, the spectral
evolution in this system is highly complex since the excited states and the NO· release
channel intermediaries undergo relaxation in multiple time-scales. Our experiments
however, do provide direct measurements of the overall time-scale for the accumulation of
the primary products: the ArO· radical and the first triplet state T1. In addition to our
experimental work, we include theoretical calculations at the Time-Dependent Density
Functional level of theory (TD−DFT) in order to understand how the state ordering (first
excited singlet relative to triplet states) may be related to the observed ultrafast manifold
crossing. We are particularly interested in the role of molecular orbitals with a partial non-
bonding character that confer the appropriate n-π* character to “receiver” vibronic triplet
states which mediate the singlet-triplet population transfer. In order to get further insights
into the importance of specific states in the photophysical channel, we also studied two 9-
substituted anthracenes which have the same electronic configuration as 9-NA: anthracene-
9-carboxylic acid (9-ACA) and the respective deprotonated specie (9-ACOO-) in the form
5
6. of the sodium salt. Comparisons with these two molecules reaffirm and clarify the effect of
the nitro group on the photophysics in relation with the existence of a specific “receiver”
state in the triplet manifold.
EXPERIMENTAL
Optical Spectroscopy
Our transient absorption setup has been described in detail elsewhere.26 It is based on an
amplified 1 kHz, 150 fs Ti:Sapphire laser system. The pulse train was frequency doubled in
a 0.5 mm β−BBO crystal to produce the 400 nm excitation pulses. 1 % of the fundamental
light was separated with a dicroic mirror (CVI) to generate a continuum in a 1 mm Z-cut
sapphire disk. The excitation beam polarization was adjusted with a half wave plate to
magic angle conditions and focused into the cell sample with a 15 cm fused silica lens. The
excitation intensity was minimized placing the sample 6 cm from the focal point to
decrease the laser intensity, keeping a beam diameter of 0.8 mm as measured by the knife-
edge method. Probe pulses at wavelengths below 400 nm pulses were obtained through
second harmonic generation (SHG) from the continuum in the 760 to 780 nm range. The
probe beam was focused at the sample to a 20 to 200 µm radius after traversing a time
delay stage. The sample was flowed either inside a 1 mm path length quartz closed loop
flow cell or through a free flowing jet with an optical path of 0.45 ± 0.05 mm. Both of these
methods to handle the sample presented consistent results. After the sample, the probe
beam was focused into a 10 cm double monochromator and detected either with a silicon
photodiode or a photomultiplier tube connected to a lock-in amplifier (Stanford Research
Systems). For the lock-in detection, two of every three excitation pulses were
6
7. synchronously blocked with a phase-locked optical chopper (New Focus). The pump pulse
energy for all experiments was kept approximately at 50 µJ to avoid the two-photon
excitation of the solvent. At some wavelengths, the signal around t = 0 was superimposed
by a coherent interaction between the pump and probe pulses (coherent spike). Replacing
the sample by the plain solvent to perform back to back experiments for every single
wavelength, confirmed that this effect arises from the cross phase modulation in both the
solvent and the flow cell walls. In these cases, the modulations were subtracted from the
raw traces according to the procedure available in the literature.36-37
Femtosecond fluorescence up-conversion experiments were made in order to follow
the short lived emissive S1 state of 9-NA. Spontaneous emission was collected using a 1 cm
focal length parabolic mirror and then refocused it with a second 10 cm focal length
parabolic mirror. Residual excitation light was eliminated using a long wavelength pass
filter between the two parabolic mirrors. A temporally delayed gate pulse was focused into
a 0.5 mm β−BBO crystal (θcut = 44°) making a small angle with the focused fluorescence.
Vertical polarization of the gate pulse was adjusted with a half wave plate to coincide with
the up-conversion crystal’s acceptance axis (ordinary axis) for the type I wave mixing.
Sum-frequency mixing the gate pulse with the fluorescence resulted in an up-conversion
signal in the UV which was focused to a 10 cm entrance slit of a double monochromator
(Oriel), and detected with a photomultiplier tube which was connected to a Lock-in
amplifier referenced to a 1/3 kHz chopper modulating the pump pulse. The Instrument
Response Function (IRF) was gaussian 400 ± 50 fs Full Width at Half Maximum (FWHM)
as determined using a cross correlation measurement in the crystal between the
7
8. fundamental pulse and the Raman scattering from the second harmonic pulse when crossing
the 1 mm cell filled with pure ethanol. Fluorescence anisotropies r(t) = (I║-I┴)/(I║+2·I┴)
were determined by rotating the polarization of the pump beam to measure respectively,
parallel (I║) and perpendicular (I┴) components of the spontaneous emission.
All UV-Vis absorption spectra were taken in a 1 cm quartz cell with a Cary-50
spectrophotometer (Varian). Steady state emission spectra were obtained with a Cary-
Eclipse fluorimeter (Varian). 9-NA, 9-ACA and the solvents were purchased from Aldrich.
9-NA and 9-ACA were re-crystallized twice from HPLC grade ethanol and isolated from
light. The sodium salt of 9-ACA was formed by dissolving the acid in methanol solution
and then precipitating the salt by addition of a concentrated methanolic solution of NaOH.
All experiments were made at room temperature (20 ± 1 °C) under aerated conditions.
Computational Methods
The electronic properties of the ground and excited states of 9-NA and the two isoelectronic
compounds 9-ACA and 9-ACOO- were calculated considering the hybrid functional of
Perdew, Burke and Ernzerhof (PBE0). The use of this functional for DFT and TD−DFT
calculations seems adequate from previous studies, where it was demonstrated that the
excited states calculations in the singlet manifold of several polyaromatic systems present
the correct distribution of the energy levels.38-42 Also, this method has been used to predict
the efficiency of different photophysical channels in terms of the energetic coincidence of
different electronic states.35,43-48 All calculations were performed with the Gaussian 09 suite
of programs.49 The ground state geometry of the model compound was optimized using the
PBE0/6-311++G(d,p) gradient procedure. Furthermore, the Polarized Continuum Model
8
9. (PCM) with the integral equation formalism (IEFPCM) developed by Tomasi and
coworkers was used to study the influence of ethanol in the electronic properties of the
excited aromatic system.50-55 Vertical electronic transitions in the singlet and triplet
manifolds of 9-NA were calculated at the ground state geometry with the (PCM)TD-
PBE0/6-311++G(d,p) level of theory.
RESULTS AND DISCUSSION
Solution steady state spectroscopy
Figure 1 shows the structure and the UV-visible absorption spectrum of 9-NA. As can be
seen, the vibronic structure of the first electronic transition is retained from that of
anthracene, however, the band is significantly shifted towards longer wavelengths in
comparison with the polyaromatic parent compound. Such effect already speaks about
some effect of the –NO2 group in the S1←S0 transition. From inspection of the vibronic
structure and the behavior in different solvents, it has been concluded that the first
electronically excited state in this compound has still a dominant anthracenic π−π*
character; this will be elaborated in more detail in the computational section. Here, we
would like to point out that the equilibrium ground-state C9a-C9-N-O dihedral angles in 9-
NA are approximately 56° (see Figure 1). This value comes from a balance between a steric
repulsion with the two peri-hydrogens, and the tendency towards planarity which would
extend the conjugation into the NO2 group.56 As will be shown, the twisting of the NO2
group is related to the fact that the first transition retains a significant anthracenic character
since the aromatic system and the nitro group are not fully aligned. Despite several attempts
to obtain reliable emission spectra from 9-NA in different solvents, this was not possible
9
10. with which the fluorescence quantum yield was determined to be well below 10-3. This
contradicts a very early report by Jain et al. who detected an emission band from a 9-NA
cyclohexane solution.57 After performing careful unsuccessful attempts to detect
fluorescence in this solvent, we conclude that the emission in that report is due to the
formation of photoproducts in their solution, consistently with the known photochemistry
of this molecule and the current report (see ultrafast fluorescence experiments).21,32
Time resolved fluorescence measurements
The results of femtosecond fluorescence up-conversion experiments on ethanol
solutions of 9-NA are shown in Figure 2. These measurements complement our previously
published results by considering an expanded spectral region for the detection of the
spontaneous singlet emission, including now much longer wavelengths where the signal is
considerably smaller.58 Such measurements are significant since they indicate the complete
time-range in which at least a fraction of the population of the emissive S1 state persists. It
should be remarked that this technique is specific to emissive singlet states and that it does
not suffer from the spectral crowding of the transient absorption experiments (see below).
As can be seen, the emission can only be detected within the first couple of picoseconds,
consistently with the broadly held idea that nitroaromatics are non-fluorescent.59-60
Although several attempts were made, it was not possible to acquire reliable steady state
fluorescence emission spectra from 9-NA solutions in ethanol, implying a quantum yield
value of less than 10-4.
Across the spectrum (495 nm to 610 nm), the up-conversion traces are clearly
biexponential. Results of non-linear least square fits to convoluted double exponential
10
11. functions are included in Table 1. The first decay has time constants from less than 150 fs
to about 280 fs, and account for more than 70 % of the total signal amplitude. The ultrafast
component is followed by a slower one which is wavelength-dependent and that becomes
slower going to longer wavelengths with values from 0.68 ps (495 nm), to 1.4 ps (610 nm).
As we have noted in previous publications, the biexponential decay of the singlet
emission for nitroaromatics appears to be related either to a fast component of the solvent
response, or to a structural relaxation of the orientation of the nitro group, whereby, after
the molecule has been vertically excited to the first singlet excited state, it relaxes within
the S1 potential energy surface towards a structure where the plane of the NO2 triad defines
a different angle with the aromatic system plane.35,43,58 This proposal is supported by
calculations from Crespo-Hernandez et al., which indicate the equilibrium geometry of the
S1 state of 1-nitropyrene corresponds to much more coplanar structures than the ground
states (S1 optimizations through the Configuration Interaction Singles methodology).35 The
double exponential form of the fluorescence traces is indeed predicted by a simplified
ini
kinetic scheme where the vertically excited geometry ( S1 ) produces, in one step, the
relaxed first singlet excited state ( S1 ) in a unimolecular process with rate constant k ini ,
rel
rel
ini rel
and where both S1 and S1 have additional depletion channels with total rate constants:
k ini and k depl . These two depletion channels include the decay of both the S1 forms to the
depl
rel
triplet manifold (see transient absorption results). The scheme is summarized in the
population decay equations 1 and 2.43,58
ini ini − ( k ini + k ini ) t
depl rel
S1 ( t ) = S1 ( t 0 ) e (1)
11
12. rel S1 ( t 0 ) k ini
ini
rel −( k ini + k ini ) t − k rel ⋅ t
S1 ( t ) = e depl rel − e depl (2)
k depl − k ini − k ini
rel
depl rel
The fact that both the ultrafast (τ1: sub 150 fs to 280 fs) and the “slow” (τ2: 0.68 ps to 1.4
ps) components of the emission are detected at all wavelengths implies that the spectral
ini rel
region for the emission of both S1 and S1 states overlap, so that at any time, the sum of
ini rel
the populations S1 plus S1 is being detected through their spontaneous emission channel.
That different time constants are measured across the spectrum is most likely related to the
fact that the solvent response (which redounds in a dynamic red shifting of the emission) is
superimposed with the excited state population decay. Considering our scheme, the
ultrafast and “slow” components in the up-conversion results are assigned as follows: τ1 =
( k ini + k ini )-1 and τ2 = ( k depl )-1. The products of the decay or depletion channels should in
depl rel
rel
general be considered to be precursors of the “final” species; dissociation product: ArO·,
and ISC product: T1 (see transient absorption results). This is indicated in Scheme 1 which
summarizes the times observed in our experiments.
An alternative explanation for the double exponential nature of the fluorescence
decay would require the existence of two different emissive singlets states, where the
excited state population would undergo internal conversion S2→S1 after the initial
photoexcitation. Such a scheme produces an analogous set of population kinetics as those in
equations 1 and 2, but where the fast decay corresponds to photons emitted from the
originally excited state, and the “slow” one (~1 ps), to photons emitted from the lowest
energy singlet S1. We note that such alternative scheme would imply that our excitation at
12
13. 385 nm forms not exclusively the lowest excited singlet, but to some extent, a superposition
with a second upper singlet S2. In order to test whether this is a reasonable explanation for
the double exponential form of the decays, we performed detailed anisotropy measurements
on the emission at a couple of wavelengths: 495 nm and 540 nm with an improved signal to
noise ratio in comparison with our previous report.58 Since 9-substituted derivatives tend to
have the first and second electronic transitions with perpendicular transition dipole
moments (where the first transition is anthracenic :1La type),61-63measurements of r(t) would
indicate whether there is a change in the transition moment direction as the signal evolves
from the fast to the slower components in the traces of Figure 2. The results are shown in
Figure 3. The r(t) measurements show that, although the decay of the emission has a rate
change (main plots, going from fast to slow components), the anisotropies only undergo a
much slower monotonous decay due to the diffusional rotation of the photoexcited
molecules (insets). This result disproves the aforesaid singlet-singlet sequence through
internal conversion, but is still consistent with the idea that the same electronic state
produces both the fast and the “slow” components of the emission.
In order to better understand how the orbital properties and the excited-state
ordering (see computational results) relate to the rapid emission decay, we studied two
other systems which are isoelectronic to 9-NA: anthracene-9-carboxylic acid (9-ACA), and
sodium anthracene-9-carboxylate (sodium salt of 9-ACOO-). This 9-carboxy substituted
anthracene shares the electronic configuration of 9-NA (see below), but shows completely
different fluorescent state dynamics. In the computational section this comparison will be
used to illustrate how peculiarities in the electronic structure of the triplet manifold of 9-NA
are responsible for the ultrafast decay of its S1 state. Figure 4 shows the absorption and
13
14. emission spectra of 9-ACA and its sodium salt in acetone solution. This solvent was used in
order to produce a molecular population without mixtures of protonated (neutral acid) and
deprotonated species in the respective solutions, according to inspections of the emission
spectra.64-65 It should be noted that for the acid, the emission spectrum is considerably red
shifted and that the vibrational structure is completely absent, while for the salt, the
emission spectrum retains the anthracenic properties with respect to the characteristic
vibronic structure and band position.
As can be seen in the main plots, the fluorescence lifetimes of both these
compounds are drastically longer than that of 9-NA. For the acid, we measured an S1
lifetime of 2.3 ns, and for the salt, 0.7 ns. Clearly, the highly efficient pathways responsible
for the ultrafast emission decay of 9-NA are not operating in the two isoelectronic
compounds. Insights into this observed phenomenon will be discussed in the computational
section.
Transient absorption results
The highly phosphorescent nature of 9-NA implies that the main decay pathway for
the S1 state of 9-NA is through ISC to a vibronic level in the triplet manifold. As
mentioned, a NO· photodissociation also takes place in parallel with the T1 channel, but is
considered to be a minor channel from the ~7% photoreaction yield in ethanol.21 The time-
scales for the accumulation of the phosphorescent state and the anthryloxy radical fragment
were characterized through the transient absorption measurements shown in Figures 5 to 7.
Although the absorbance signals evolve in several time scales, and despite there being
several coexisting species, the results from the previous fluorescence measurements allows
14
15. some discernment of the contributions of the different populations to the transient signals.
In the first place, the spectral evolution has ceased completely by approximately 30 ps,
where the transient spectrum observed in the visible region corresponds to optical
absorption by the first triplet state of 9-NA (see last spectrum of Figure 5). Such
assignment can be made from comparisons with the T1 spectrum determined previously in
nanosecond flash photolysis experiments.21 The T1 spectrum is characterized by a single
peak at 425 nm, with small amplitudes in the rest of the visible region. Since the absorption
coefficients of this specie have not been measured, the yield for triplet formation cannot be
estimated from this spectrum, however, since the photoreaction yield is small (~ 7%),21 it
can be safely assumed that this is the most prominent channel for 9-NA.
The evolution leading to the T1 state will be described by referring to different
spectral zones which are represented in the traces of Figure 6. It should be mentioned that
global analysis of the data failed due to the spectral shifting and/or band narrowing that
take place from vibrational relaxation and solvation in the triplet manifold (see below),
inducing spectral reshaping in a multitude of time scales in this kind of systems.26,30 For
wavelengths from 490 nm to 680 nm, the transient absorption signals show an
instantaneous appearance that is followed by an ultrafast decay of less than 150 fs. This
early feature is followed by a second decay with a time constant of 2.1 ps (decay of the
broad band around 625 nm in Figure 5). After these decays, the signal remains at a constant
level, which is consistent with the fact that the T1 state is a persistent specie in the time
scale of our experiment (reported T1 decay rate: 9.62 x 104 s-1 at room temperature in
ethanol).21
15
16. In the region a few tens of nanometers from the 425 nm T1 peak on the red side of
the spectrum (440 nm to 480 nm), the signals have exponentially decaying terms of about
10 ps besides the ultrafast (< 150 fs) and a ~2 ps component. This is represented by the 480
nm trace of Figure 6. At wavelengths near the maximum of the T1 absorbance (420 nm and
430 nm), a small instantaneous negative signal due to the ground state depletion is followed
by an ultrafast absorbance rise (τ < 150 fs), which is then followed by a decay to a constant
level (the T1 absorbance) with a time constant of 3.5 ps. The fact that even at the peak of
the T1 absorption (~425 nm) the signal becomes smaller after the ultrafast rise, indicates
that the T1 species has a smaller absorption coefficient than its precursor at all the
wavelengths of our study. Finally, on the blue side from the T1 peak (380 nm), the
absorption signal shows an instantaneous bleach due to the ground state depletion, which
then partially recovers to the base line in two time scales: 2.8 ps and a much slower one of
23 ps. The first time constant is consistent with the accumulation of the phosphorescent
state considering that this species still shows significant absorbance at this wavelength.21
The 23 ps component is associated to relaxation within this state (see below).
From our time resolved fluorescence measurements, we interpret the sub-150 fs
transient absorption components seen across most of the spectrum to the ultrafast part of the
decay isolated in the up-conversion experiments, that is, the early and prominent decay of
the S1 state. Our results indicate that in general, this decay gives rise to an intermediary
excited state which in turn will produce the T1 state. More explicitly, our results clearly
show that the appearance of the T1 state and the decay of the singlet population do not show
simple one to a one kinetics. The transients that decay in the 2 to 3.5 ps time scale must
then be assigned to evolution of T1 from a “receiver” or intemediary upper triplet
16
17. vibroelectronic state which is the state that actually couples to the S1 singlet. The 10 to 23
ps components which are present only on the red and blue side of the T1 peak respectively
are assigned to the vibrational relaxation and solvation steps which must accompany the
accumulation of population in the long-lived fully relaxed T1 state (see Scheme 1). Previous
investigations have actually shown that solvation and the elimination of vibrational energy
are related to such kind of a reshaping of the principal bands of the fully relaxed triplet state
in similar systems.26, Reichardt, 2009 #265
Even though the NO· dissociation is a minor channel, the accumulation of the
aryloxy radical ArO· can be followed specifically at the wavelength of 350 nm where this
species shows a sharp and intense peak.21 The transient absorption trace for this wavelength
is depicted in Figure 7. As can be seen, the signal shows a fast feature again with a time
constant less than 200 fs. From the previously established time scales, such fast decay must
correspond to the detection of the first singlet excited state through a Sn←S1 absorbance.
This fast feature is followed by the growth of a transient absorption signal from the ArO·
specie, which then persists for more than several hundreds of picoseconds. Inspection of
this absorbance increment reveals that the trace follows a sigmoid type rise which is typical
of the indirect accumulation of the absorbing specie (ArO·) through an intermediary
stage.66 This is actually consistent with the notion that the NO· + ArO· fragments are
formed through a molecular rearrangement which precedes the formation of a new C-O
bond in the oxy radical. The ArO· precursor (“Intermediary” in Scheme 1, see below), has
been proposed to have a nitrite geometry (Ar-O-N=O) which in turn may be formed
through an oxaziridine type geometry (C-N-O cycle).32
17
18. The best fit parameters of the sigmoid-type evolution of the 350 nm trace provided
the time-scale for the accumulation of the ArO· population as elaborated next: The
simplified kinetic model for this process includes an initial excited state ArNO2*, an
intermediary Int and the final specie ArO· detected at 350 nm. For the most general
consideration, the ArNO2* state could correspond either to the S1 state, or the rapidly
formed upper triplet state Tn (“receiver state”) formed previous to the phosphorescent
triplet (as indicated, the aryloxy specie does not accumulate from T1 since both signals at
425 nm and at 350 nm persist after the first few picoseconds). The kinetic scheme must also
consider the fact that the ArNO2* form has at least two decay channels, only one of which
redounds in the ArO· product (namely, S1 also would undergo intersystem crossing, and Tn,
internal conversion to T1). Once this detail is taken into consideration, the kinetic scheme
is similar to the case of consecutive reactions ArNO2* →Int → ArO·, except that the initial
reactant has an “additional” channel (ArNO2* → internal conversion or ISC products). The
respective kinetic formulas for the intermediary (Int) and ArO· correspond to equations 3
and 4 (see also Scheme 2).
ArNO* ( t 0 ) ⋅ k1
Int( t ) = 2
k 2 − k1 − k '
(e −( k1+k ') t
− e −k 2 ⋅t )
(3)
k ' k1 k1 − ( k1 + k ' ) t k1
ArO ⋅ ( t ) = ArNO* ( t 0 ) 1 −
2 −
+ e
+ e− k 2 ⋅ t
k1 + k ' k1 + k ' k 2 − k1 − k ' k 2 − k1 − k '
(4)
18
19. Where ArNO2* is the population of the electronically excited precursor (S1 or Tn state), k1 is
the unimolecular rate constant for the formation of the Intermediary, k2 is the rate constant
for the ArO· formation (unimolecular, from Int), and k' is the rate constant for the
“additional” decay channel of the electronically excited precursor state ArNO2*.
The signal accumulation at 350 nm follows remarkably well the description of the
sigmoid-shaped accumulation from equation 4 which predicts a short “lag” or induction
period. From a non-linear least squares fit, the time constants for equation 4 were
determined to be: (k1+k’)-1 = 3.25 ps, and (k2)-1 = 8.7 ps.
Although our kinetic scheme is highly simplified, the transient absorption
measurement of Figure 7 establishes, for the first time, the time-scale for the events that
lead to the NO· + ArO· dissociation, showing that the photochemical steps take place
within the first few picoseconds, after which, the population of both the photophysical (T1)
and photochemical (ArO·) channels for photoexcited 9-NA have accumulated completely.
It should be remarked that the evolution of the intermediary Int of the photochemical
channel cannot be assigned with any certainty in the transient absorption evolution in the
visible region. This is due to the fact that there are multiple species coexisting in the 1-10
ps time range, that it is not an intermediary that accumulates significantly, and that it is
formed in a low yield. Investigation of the chemical structure of the photochemical
intermediary will require time resolved experiments in the mid-infrared region which
19
20. should be able to follow the appearance and decay of signals specific to the bonding in the
intermediary (for example, oxaziridine-type ring, or nitrite compound). Our experiment of
Figure 7 does however provide a road map to the time-scales where the rearrangement-
dissociation events take place, particularly, we directly measured the accumulation of the
ArO· population.
Computational results
Next, we make a correspondence analysis between the excited state kinetics and the
calculations of the low lying excited states through the TD−DFT formalism. In the first
place, the ground state of the molecule as optimized at the DFT/6-311++G(d,p) level with
the PCM model to account for solvation effects in ethanol, shows that the nitro group is not
coplanar with the aromatic rings, with a C9a-C9-N-O dihedral angle of 56°. As already
mentioned, this is consistent with previous studies and indicates a balance between
delocalization and peri-hydrogen repulsions.56 The vertically accessed excited state
energies are included in Figure 8 for the calculation in the gas phase and in ethanol. The
first singlet excited state is formed mostly from HOMO-LUMO single excitations
(considers the coefficients of the TD−DFT method, taken directly from the calculation
output, see Supporting Information). Inspection of these orbitals confirms that the short-
lived fluorescent state of 9-NA has a predominant π−π* character. Similar considerations
indicate that the lowest energy triplet state T1 is also dominated by the HOMO-LUMO
π−π* type transition. This is consistent with the analysis of the phosphorescent spectra of
this molecule made by Hammanoue et al. who on the basis of the behavior in different
20
21. solvents and its vibronic structure, concluded it to have a π−π* nature.21-22 Inspection of the
HOMO and LUMO Kohn-Sham orbitals of Figure 9 revealed that at the aromatic system,
the frontier orbitals retain respectively the nodal structure of the anthracenic b2g and b3u
orbitals, additionally somewhat extending into the NO2 substituent.
Most interesting of the computational results, it appears that there are low-lying
states in the triplet manifold slightly below the S1 level as shown in Figure 8. For the case
of the gas phase calculations, there are two triplet states above T1 and below the S1 energy.
On the other hand, for the ethanol case, only the T2 state exists at a lower energy than S1.
Despite the fact that in gas phase versus in ethanol, different triplet states are near-S1
isoenergetic, the gas-T3 state and the ethanol-T2 state, both have significant contributions
from the HOMO-3 to LUMO excitations (see excitation coefficients in supporting
information). From examination of the HOMO-3 orbital included in Figure 9, it is clear that
this orbital is formed in part by an anthracenic b2g orbital, and from a non-bonding type
orbital (n- combination67) at the nitro–group. From the El-Sayed propensity rules for
intersystem crossing and within the TD-DFT theory, this orbital can be regarded as
responsible for the observed ultrafast singlet-triplet transition, which is several orders of
magnitude faster than ordinary thanks to the fact that a π−π* singlet couples to a “receiver”
triplet state described by excitations from orbitals with a partial n character.29
When the DFT-calculated ground state geometry of 9-NA is compared with that of
the isoelectronic molecule 9-ACA, it is clear that in the acid, the carboxylic group also
shows a deviation from coplanarity with the anthracenic ring, by an angle of 50° and 57° in
gas and condensed phase, respectively. Importantly and related to the structural similarities,
21
22. these two molecules share the ordering and aspect of their frontier orbitals (depictions for
9-ACA are included in the Supporting Information). When the excited state description at
the TD−DFT level of theory is examined however, 9-NA and anthracene-9-ACA show two
interesting differences which we would like to emphasize, are crucial for their drastically
different photophysics. For the acid, the second triplet state T2 appears to be destabilized
with respect to the S1 state so that it is actually above the S1 state by a fraction of an eV.
More importantly, the second triplet state in the acid has, in any case, a much reduced
contribution from the HOMO-3 to LUMO excitation, which is assumed to be responsible
for the partial n-π∗ character of the T2 state of 9-NA in ethanol. An even more obvious
difference appears when 9-NA is compared with the unprotonated form of 9ACA: 9ACOO-
(also isoelectronic to 9-NA). The anthracenic carboxylate shows a ground-state optimized
structure where the COO- triad is now nearly perpendicular to the aromatic system. Such
structural difference results in a completely different orbital (and excited state) ordering for
the carboxylate in comparison with 9-NA. In particular, the Kohn-Sham orbital with a
partial n- composition now appears as the HOMO-6 orbital, and therefore, transitions
involving such orbital make a negligible contribution to the low-lying triplet-states. The
computational description of the excited state ordering of 9-ACA and its salt have
therefore, differences with respect to 9-NA which are apparently critical in determining the
rate of non-radiative channels (in particular, intersystem crossing involving a particular
“receiver” triplet state in 9-NA), so that 9-ACA and 9-ACOO- show a common behavior of
a nanoseconds-lived fluorescent state shown in Figure 4 instead of the ultrafast manifold
crossing observed for 9-NA.
22
23. CONCLUSIONS
We have described the excited state dynamics of 9-NA through a series of different
approaches which include the tracking of the emissive singlet states through up-conversion
experiments and the characterization of the time-scale in which the products of its primary
photochemistry are formed (ArO· and T1 state). We also present a computational
description of the low-lying excited states of 9-NA, including comparisons with two
isoelectronic model systems, 9-ACA and its deprotonated form. Put together, these results
give the following depiction: The S1 state emission decays in two different time scales, of
~150 fs, and up to 1.4 ps. The double exponential nature of the fluorescence decay was
interpreted in terms of a discrete relaxation event after which, the S1 decay rate becomes
slower. Signals with lifetimes of 2 to 3.5 ps in the transient absorption experiments were
ascribed to a particular “receiver state” in the triplet manifold. Most important, it is clear
that the T1 state is not formed directly from the S1 state, but instead, crucial intermediate
steps take place, including coupling with an upper state in the triplet manifold as well as
internal conversion, solvation and vibrational relaxation (up to about 23 ps). We also
provide the first direct measurement ever made of the accumulation of the product of the
photochemical channel (Ar-O·) where it was observed that it involves the kinetics of the
product of a sequential reaction with a formation time constant of 8.7 ps. The
computational results at the TD−DFT level confirm and clarify the experimental results. In
particular, they identify the most likely receiver state in ethanol as the second state in the
triplet manifold which is nearly isoenergetic to the S1 state. The excited state description of
two isoelectronic but highly fluorescent systems (9-ACA and 9-ACOO-) further support
this idea since in these two molecules, the n-π∗ state nature of an isoenergetic triplet state,
23
24. or the S1 energy coincidence is disturbed, thereby allowing the molecules to have a
fluorescent state lifetimes several orders of magnitude longer than 9-NA.
ACKNOWLEDGEMENT
For financial support, we thank Consejo Nacional de Ciencia y Tecnología (CONACyT,
Grant 79494), and to Universidad Nacional Autónoma de México (PAPIIT, Grant
IN204211). The authors thank DGSCA-UNAM for computational resources.
SUPPORTING INFORMATION AVAILABLE
Curve fitting parameters for transient absorption fits, results of excited state calculations at
the TD-DFT level of theory including excited state descriptions and frontier Kohn-Sham
orbital isosurfaces, ground state optimized geometries of the molecules of this study. This
material is available free of charge via the Internet at http://pubs.acs.org.
24
25. REFERENCES
(1) Cvrckova, O.; Ciganek, M. Polycyclic Aromat. Compd. 2005, 25, 141.
(2) Fan, Z.; Kamens, R. M.; Hu, J.; Zhang, J.; McDow, S. Environ. Sci. Technol. 1996,
30, 1358.
(3) Gerasimov, G. Y. High Energy Chemistry (Translation of Khimiya Vysokikh
Energii) 2004, 38, 161.
(4) Kamens, R. M.; Zhi-Hua, F.; Yao, Y.; Chen, D.; Chen, S.; Vartiainen, M.
Chemosphere 1994, 28, 1623.
(5) Warner, S. D.; Farant, J.-P.; Butler, I. S. Chemosphere 2004, 54, 1207.
(6) Kim, Y. D.; Ko, Y. J.; Kawamoto, T.; Kim, H. Journal of Occupational Health
2005, 47, 261.
(7) Bamford, H. A.; Bezabeh, D. Z.; Schantz, M. M.; Wise, S. A.; Baker, J. E.
Chemosphere 2003, 50, 575.
(8) Hayakawa, K.; Tang, N.; Akutsu, K.; Murahashi, T.; Kakimoto, H.; Kizu, R.;
Toriba, A. Atmos. Environ. 2002, 36, 5535.
(9) Heeb, N. V.; Schmid, P.; Kohler, M.; Gujer, E.; Zennegg, M.; Wenger, D.;
Wichser, A.; Ulrich, A.; Gfeller, U.; Honegger, P.; Zeyer, K.; Emmenegger, L.; Petermann, J. L.;
Czerwinski, J.; Mosimann, T.; Kasper, M.; Mayer, A. Environmental Science & Technology 2008,
42, 3773.
(10) Srogi, K. Environmental Chemistry Letters 2007, 5, 169.
(11) Arey, J.; Zielinska, B.; Atkinson, R.; Winer, A. M.; Ramdahl, T.; Pitts, J. N. Atmos.
Environ. 1986, 20, 2339.
(12) FinlaysonPitts, B. J.; Pitts, J. N. Science 1997, 276, 1045.
(13) Fukuhara, K.; Kurihara, M.; Miyata, N. J. Am. Chem. Soc. 2001, 123, 8662.
25
26. (14) Fukuhara, K.; Oikawa, S.; Hakoda, N.; Sakai, Y.; Hiraku, Y.; Shoda, T.; Saito, S.;
Miyata, N.; Kawanishi, S.; Okuda, H. Bioorg. Med. Chem. 2007, 15, 3869.
(15) Suzuki, T.; Nagae, O.; Kato, Y.; Nakagawa, H.; Fukuhara, K.; Miyata, N. J. Am.
Chem. Soc. 2005, 127, 11720.
(16) Costela, A.; Garcia-Moreno, I.; Garcia, O.; Sastre, R. Journal of Photochemistry
and Photobiology, A: Chemistry 2000, 131, 133.
(17) Costela, A.; Garcia-Moreno, I.; Garcia, O.; Sastre, R. Chem. Phys. Lett. 2000, 322,
267.
(18) Fournier, T.; Tavender, S. M.; Parker, A. W.; Scholes, G. D.; Phillips, D. J. Phys.
Chem. A 1997, 101, 5320.
(19) Goerner, H. J. Chem. Soc., Perkin Trans. 2 2002, 1778.
(20) Hurley, R.; Testa, A. C. J. Am. Chem. Soc. 1968, 90, 1949.
(21) Hamanoue, K.; Nakayama, T.; Kajiwara, K.; Yamanaka, S.; Ushida, K. J. Chem.
Soc., Faraday Trans. 1992, 88, 3145.
(22) Hamanoue, K.; Nakayama, T.; Ushida, K.; Kajiwara, K.; Yamanaka, S. J. Chem.
Soc., Faraday Trans. 1991, 87, 3365.
(23) Hamanoue, K.; Nakayama, T.; Amijima, Y.; Ibuki, K. Chem. Phys. Lett. 1997, 267,
165.
(24) Nakayama, T.; Amijima, Y.; Ibuki, K.; Hamanoue, K. Rev. Sci. Instrum. 1997, 68,
4364.
(25) Zugazagoitia, J. S.; Almora-Diaz, C. X.; Peon, J. J. Phys. Chem. A 2008, 112, 358.
(26) Zugazagoitia, J. S.; Collado-Fregoso, E.; Plaza-Medina, E. F.; Peon, J. J. Phys.
Chem. A 2009, 113, 805.
(27) El-Sayed, M. A. J. Chem. Phys. 1963, 38, 2834.
(28) Lower, S. K.; El-Sayed, M. A. Chem. Rev. 1966, 66, 199.
26
27. (29) Mikula, J. J.; Anderson, R. W.; Harris, L. E.; Stuebing, E. W. J. Mol. Spectrosc.
1972, 42, 350.
(30) Reichardt, C.; Vogt, R. A.; Crespo-Hernandez, E. J. Chem. Phys. 2009, 131.
(31) Mohammed, O. F.; Vauthey, E. J. Phys. Chem. A 2008, 112, 3823.
(32) Chapman, O. L.; Heckert, D. C.; Reasoner, J. W.; Thackaberry, S. P. J. Am. Chem.
Soc. 1966, 88, 5550.
(33) Hamanoue, K.; Amano, M.; Kimoto, M.; Kajiwara, Y.; Nakayama, T.; Teranishi,
H. J. Am. Chem. Soc. 1984, 106, 5993.
(34) Arce, R.; Pino, E. F.; Valle, C.; Agreda, J. J. Phys. Chem. A 2008, 112, 10294.
(35) Crespo-Hernandez, C. E.; Burdzinski, G.; Arce, R. J. Phys. Chem. A 2008, 112,
6313.
(36) Ekvall, K.; Meulen, P. v. d. M.; Dhollande, C.; Berg, L.-E.; Pommeret, S.;
Naskrecki, R.; Mialocq, J.-C. J. Appl. Phys. 2000, 87, 2340.
(37) Lorenc, M.; Ziolek, M.; Naskrecki, R.; Karolczak, J.; Kubicki, J.; Maciejewski, A.
Appl. Phys. B: Lasers Opt. 2002, 74, 19.
(38) Adamo, C.; Barone, V. J. Chem. Phys. 1998, 108, 664.
(39) Adamo, C.; Barone, V. J. Chem. Phys. 1999, 110, 6158.
(40) Adamo, C.; Barone, V. Chem. Phys. Lett. 1999, 314, 152.
(41) Adamo, C.; Barone, V. Chem. Phys. Lett. 2000, 330, 152.
(42) Adamo, C.; Scuseria, G. E.; Barone, V. J. Chem. Phys. 1999, 111, 2889.
(43) Collado-Fregoso, E.; Zugazagoitia, J. S.; Plaza-Medina, E. F.; Peon, J. J. Phys.
Chem. A 2009, 113, 13498.
(44) Karunakaran, V.; Kleinermanns, K.; Improta, R.; Kovalenko, S. A. Journal of the
American Chemical Society 2009, 131, 5839.
27
28. (45) Kobayashi, T.; Kuramochi, H.; Harada, Y.; Suzuki, T.; Ichimura, T. J. Phys. Chem.
A 2009, 113, 12088.
(46) Gustavsson, T.; Banyasz, A.; Lazzarotto, E.; Markovitsi, D.; Scalmani, G.; Frisch
Michael, J.; Barone, V.; Improta, R. J Am Chem Soc 2006, 128, 607.
(47) Liu, T.; Xia, B.-H.; Zheng, Q.-C.; Zhou, X.; Pan, Q.-J.; Zhang, H.-X. Journal of
Computational Chemistry 2010, 31, 628.
(48) Gabrielsson, A.; Matousek, P.; Towrie, M.; Hartl, F.; Zalis, S.; Vlcek, A., Jr. J.
Phys. Chem. A 2005, 109, 6147.
(49) Gaussian 09, R. A. M. J. F., G. W. T., H. B. Schlegel, G. E. Scuseria, ; M. A. Robb,
J. R. C., G. Scalmani, V. Barone, B. Mennucci, ; G. A. Petersson, H. N., M. Caricato, X. Li, H. P.
Hratchian, ; A. F. Izmaylov, J. B., G. Zheng, J. L. Sonnenberg, M. Hada, ; M. Ehara, K. T., R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, ; Y. Honda, O. K., H. Nakai, T. Vreven, J. A.
Montgomery, Jr., ; J. E. Peralta, F. O., M. Bearpark, J. J. Heyd, E. Brothers, ; K. N. Kudin, V. N. S.,
R. Kobayashi, J. Normand, ; K. Raghavachari, A. R., J. C. Burant, S. S. Iyengar, J. Tomasi, ; M.
Cossi, N. R., J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, ; V. Bakken, C. A., J. Jaramillo, R.
Gomperts, R. E. Stratmann, ; O. Yazyev, A. J. A., R. Cammi, C. Pomelli, J. W. Ochterski, ; R. L.
Martin, K. M., V. G. Zakrzewski, G. A. Voth, ; P. Salvador, J. J. D., S. Dapprich, A. D. Daniels, ;
O. Farkas, J. B. F., J. V. Ortiz, J. Cioslowski, ; and D. J. Fox, G., Inc., Wallingford CT, 2009.
(50) Cances, E.; Mennucci, B.; Tomasi, J. J. Chem. Phys. 1997, 107, 3032.
(51) Mennucci, B.; Cances, E.; Tomasi, J. Journal of Physical Chemistry B 1997, 101,
10506.
(52) Mennucci, B.; Tomasi, J. J. Chem. Phys. 1997, 106, 5151.
(53) Miertus, S.; Scrocco, E.; Tomasi, J. Chem. Phys. 1981, 55, 117.
(54) Miertus, S.; Tomasi, J. Chem. Phys. 1982, 65, 239.
28
29. (55) Tomasi, J.; Mennucci, B.; Cammi, R. Chemical Reviews (Washington, DC, United
States) 2005, 105, 2999.
(56) Onchoke, K. K.; Hadad, C. M.; Dutta, P. K. Polycyclic Aromat. Compd. 2004, 24,
37.
(57) Jain, K. M.; Mallik, B.; Misra, T. N. Indian J. Pure Appl. Phys. 1976, 14, 53.
(58) Morales-Cueto, R.; Esquivelzeta-Rabell, M.; Saucedo-Zugazagoitia, J.; Peon, J. J.
Phys. Chem. A 2007, 111, 552.
(59) Rusakowicz, R.; Testa, A. C. Spectrochim. Acta, Part A 1971, 27, 787.
(60) Wolfbeis, O. S.; Posch, W.; Guebitz, G.; Tritthart, P. Anal. Chim. Acta 1983, 147,
405.
(61) Klessinger, M.; Michl, J. Excited states and photochemistry of organic molecules;
VCH: New York, 1995.
(62) Jaffe, H. H.; Orchin, M. Theory and Applications of UltraViolet Spectroscopy; John
Wiley and Sons, Inc.: New York, 1962.
(63) Jones, R. N. Chem. Rev. 1947, 41, 353.
(64) Cowan, D. O.; Schmiegel, W. W. J. Amer. Chem. Soc. 1972, 94, 6779.
(65) Werner, T. C.; Hercules, D. M. J. Phys. Chem. 1969, 73, 2005.
(66) Steinfeld, J. I.; Francisco, J. S.; Hase, W. L. Chemical kinetics and dynamics;
Prentice-Hall, Inc.: New Jersey, 1998.
(67) Jorgensen, W. L.; Salem, L. The Organic chemist's book of orbitals; Academic
Press: New York 1973.
29
30. TABLE 1: Curve Fitting Parameters for Up-conversion Traces of 9-Nitroantracene in
Ethanola
λfluo[nm] a1 τ1 [ps] a2 τ2 [ps]
495 0.81 < 150 fs 0.19 0.68
520 0.80 0.17 0.20 0.85
540 0.77 0.21 0.23 0.93
575 0.77 0.28 0.23 1.4
610 0.72 0.19 0.28 1.4
a
Data is described by double-exponential functions, I (t ) = a1 ⋅ exp(− t τ 1 ) + a2 ⋅ exp(− t τ 2 ) convoluted
with the instrument response function. The sum of parameters a1 and a2 is normalized to one.
30
31. Figure 1.
Figure 1. Molecular structure and steady state absorption spectrum of 9-nitroanthracene in
ethanol.
31
32. Figure 2.
Figure 2. Fluorescence up-conversion measurements of 9-nitroanthracene in ethanol for a
series of detection wavelengths. The excitation wavelength was 385 nm. The solid lines are
non-linear least squares fits to double exponential decays convoluted with the instrument
response function.
32
33. Figure 3.
Figure 3. Fluorescence up-conversion measurements of 9-nitroanthracene in ethanol at 495
nm (top graph) or 540 nm (bottom graph), with the polarization of the excitation beam
parallel (circles) or perpendicular (squares) with respect to the detection axis. The insets
show the time resolved anisotropy calculated from the experimental traces.
33
34. Figure 4.
Figure 4. Time resolved fluorescence decays and molecular structures of anthracene-9
carboxylic acid (top), and the respective sodium carboxylate salt (bottom), both in acetone
solutions. The insets show the respective steady state absorption and emission spectra.
34
35. Figure 5.
Figure 5. Transient absorption spectra in the visible region for ethanol solutions of 9-
nitroanthracene excited at 385 nm.
35
36. Figure 6.
Figure 6. Single wavelength transient absorption traces at representative wavelengths for 9-
nitroanthracene in ethanol. The excitation wavelength was 385 nm. The solid lines
correspond to multiexponential functions plus a constant, convoluted with a gaussian
instrument response function.
36
37. Figure 7.
Figure 7. Single wavelength transient absorption traces at 350 nm for 9-nitroanthracene in
ethanol. The excitation wavelength was 385 nm. The solid line corresponds to a
triexponential function plus a constant, convoluted with the instrument response function.
37
38. Figure 8.
Figure 8. Excitation energy diagram of 9-nitroanthracene at the (PCM)TD-PBE0/6-
311G++(d,p) level of theory in gas phase (left) and in ethanol (right). The excitation
energies (eV) are indicated in parenthesis. The geometries correspond to ground-state
optimized structures and were calculated at the same level of theory.
38
39. Figure 9.
Figure 9. Isosurfaces of the frontier Kohn-Sham orbitals of 9-nitroanthracene through the
PBE0 functional with the 6-311G++(d,p) basis set considered in ethanol with the PCM
solvation model (isosurface value: 0.03).
39
40. Scheme 1.
SCHEME 1: Time scales for the primary photoprocesses in 9-nitroanthracenea
a
The Intermediary indicated in this scheme corresponds to the molecular structure formed previous
to the NO· dissociation. As described in the text, this Intermediary could correspond to an
oxaziridine-type structure. The two arrows that point towards “Intermediary” refer to the
possibilities that its precursor may be the S1 or the Tn state.
40
41. Scheme 2.
SCHEME 2: Kinetic scheme for the accumulation of the anthryloxy radical ArO·
upon 9-nitroanthracene photoexcitation.
41