The document describes a method for synthesizing CdSe nanoparticles within polymer matrices using organometallic precursors. Specifically, it details:
1) CdSe nanoparticles were synthesized in situ within poly(vinyl alcohol) (PVA) and polymethylmethacrylate (PMMA) polymers by reacting cadmium acetate and 1,2,3-selenadiazole, which serves as the selenium source.
2) UV-vis spectroscopy showed blue shifts in the absorption spectra of the CdSe/polymer nanocomposites compared to bulk CdSe, indicating the formation of quantum-sized CdSe nanoparticles.
3) Photoluminescence spectroscopy showed an emission band at 530 nm
This document summarizes the chemical synthesis of 2-amino-4-heteroarylpyrimidines and related compounds for use as JNK1 inhibitors. Key steps include:
1) Microwave-induced SNAr reactions of primary amines with 2-methylsulfonylpyrimidines or 2-chloropyrimidines to access initial targets.
2) Elaboration of pendant piperidine functionality using silica-bound reagents in microwave reductive amination and amide bond formation.
3) Exploration of variations to the core pyrimidine scaffold and piperidine substitutions using efficient parallel synthesis methods.
The document summarizes the Chan-Lam coupling reaction, which is a copper-catalyzed coupling between an aryl boronic acid and an alcohol or amine to form secondary aryl ethers or aryl amines. It provides the history of the reaction and compares it to related palladium-catalyzed reactions. The document then discusses the proposed mechanism and provides several applications of the Chan-Lam coupling reaction in synthesizing drug molecules, heteroarenes, aminoesters, and other compounds. In conclusion, the author discusses developing an improved Chan-Lam protocol using a novel copper catalyst that is simple, rapid, and produces products at room temperature in a short time.
Three dimensional cubic ordered mesoporous carbon (cmk-8) as highly efficient...suresh800
This document describes a study comparing palladium (Pd) nanoparticles supported on two types of three-dimensional cubic ordered mesoporous carbon (CMK-8) as electrocatalysts for formic acid oxidation. The Pd/CMK-8 catalysts were synthesized using sodium borohydride reduction and characterized using techniques such as TEM, XRD, and cyclic voltammetry. Cyclic voltammetry results showed that Pd/CMK-8 with larger pores had the highest mass specific activity of 486.4 mA/mg Pd, exceeding the activities of commercial Pd/C and other recently reported Pd catalysts. Chronoamperometry testing also demonstrated this P
Highly stable pt ru nanoparticles supported on three-dimensional cubic ordere...suresh899
The cost of the catalysts used in the direct methanol fuel cell
poses a challenge to its widespread use as an energy efficient and environment
friendly fuel conversion technology. In this study, two types of highly ordered
mesoporous carbon CMK-8 (I and II) with high surface area and 3-D
bicontinuous interpenetrating channels were synthesized and deposited with
PtRu nanoparticles using the sodium borohydride reduction method. The
electrocatalytic capabilities for methanol oxidation were investigated using
cyclic voltammetry and chronoamperometry, and the results were compared
with that of PtRu deposited on Vulcan XC-72 using the same preparation
method as well as with commercial PtRu/C (E-TEK) catalyst. Pt Ru/CMK-8-I synthesized by the method developed in this work revealed an
outstanding specific mass activity (487.9 mA/mg) and superior stability
compared with the other supports, thus substantiating its potential to reduce
the costs of DMFC catalysts.
Graphene oxide immobilized copper phthalocyanine tetrasulphonamide: the first...Pawan Kumar
The first successful synthesis of DMC directly from methanol and carbon dioxide using a heterogenized
homogeneous graphene oxide immobilized copper phthalocyanine tetrasulphonamide catalyst in the
presence of N,N0-dicyclohexylcarbodiimide (DCC) as a dehydrating agent is described. The presence of a
dehydrating agent was found to be vital and in its absence the yield of DMC was found to be decreased
significantly. Under the optimized reaction conditions, the maximum yield of DMC reaches up to 13.3%.
Although the homogeneous copper phthalocyanine tetrasulphonamide catalyst provided a little higher
yield of DMC (14.2%), the facile recovery and recycling ability of the heterogeneous catalyst make the
developed method more attractive from environmental and economical viewpoints.
The document summarizes research on the stability of lead telluride (PbTe) quantum dots. PbTe QDs show promising properties for optoelectronic devices but are unstable when exposed to oxygen. The document studies the oxidation of various sized PbTe and lead selenide (PbSe) QDs over time when exposed to air and nitrogen. PbTe QDs oxidize much more rapidly than PbSe QDs when in solution. However, coating PbTe QD films with alumina provides effective long-term protection from oxidation.
Synthesis and optimisation of ir o2 electrocatalysts by adams fusion method f...sudesh789
This document discusses the synthesis and optimization of iridium dioxide (IrO2) electrocatalysts for use in solid polymer electrolyte electrolyzers through an adaptation of the Adams fusion method. The synthesis duration and temperature were varied to determine their effect on the physical and electrochemical properties of the IrO2 catalysts. X-ray diffraction analysis showed that increasing the synthesis duration and temperature increased the crystallinity and particle size of the IrO2. Chronoamperometry testing revealed that a synthesis of 2 hours at 350°C produced an IrO2 catalyst with better electrocatalytic activity for oxygen evolution than a commercial IrO2 catalyst.
This document summarizes the chemical synthesis of 2-amino-4-heteroarylpyrimidines and related compounds for use as JNK1 inhibitors. Key steps include:
1) Microwave-induced SNAr reactions of primary amines with 2-methylsulfonylpyrimidines or 2-chloropyrimidines to access initial targets.
2) Elaboration of pendant piperidine functionality using silica-bound reagents in microwave reductive amination and amide bond formation.
3) Exploration of variations to the core pyrimidine scaffold and piperidine substitutions using efficient parallel synthesis methods.
The document summarizes the Chan-Lam coupling reaction, which is a copper-catalyzed coupling between an aryl boronic acid and an alcohol or amine to form secondary aryl ethers or aryl amines. It provides the history of the reaction and compares it to related palladium-catalyzed reactions. The document then discusses the proposed mechanism and provides several applications of the Chan-Lam coupling reaction in synthesizing drug molecules, heteroarenes, aminoesters, and other compounds. In conclusion, the author discusses developing an improved Chan-Lam protocol using a novel copper catalyst that is simple, rapid, and produces products at room temperature in a short time.
Three dimensional cubic ordered mesoporous carbon (cmk-8) as highly efficient...suresh800
This document describes a study comparing palladium (Pd) nanoparticles supported on two types of three-dimensional cubic ordered mesoporous carbon (CMK-8) as electrocatalysts for formic acid oxidation. The Pd/CMK-8 catalysts were synthesized using sodium borohydride reduction and characterized using techniques such as TEM, XRD, and cyclic voltammetry. Cyclic voltammetry results showed that Pd/CMK-8 with larger pores had the highest mass specific activity of 486.4 mA/mg Pd, exceeding the activities of commercial Pd/C and other recently reported Pd catalysts. Chronoamperometry testing also demonstrated this P
Highly stable pt ru nanoparticles supported on three-dimensional cubic ordere...suresh899
The cost of the catalysts used in the direct methanol fuel cell
poses a challenge to its widespread use as an energy efficient and environment
friendly fuel conversion technology. In this study, two types of highly ordered
mesoporous carbon CMK-8 (I and II) with high surface area and 3-D
bicontinuous interpenetrating channels were synthesized and deposited with
PtRu nanoparticles using the sodium borohydride reduction method. The
electrocatalytic capabilities for methanol oxidation were investigated using
cyclic voltammetry and chronoamperometry, and the results were compared
with that of PtRu deposited on Vulcan XC-72 using the same preparation
method as well as with commercial PtRu/C (E-TEK) catalyst. Pt Ru/CMK-8-I synthesized by the method developed in this work revealed an
outstanding specific mass activity (487.9 mA/mg) and superior stability
compared with the other supports, thus substantiating its potential to reduce
the costs of DMFC catalysts.
Graphene oxide immobilized copper phthalocyanine tetrasulphonamide: the first...Pawan Kumar
The first successful synthesis of DMC directly from methanol and carbon dioxide using a heterogenized
homogeneous graphene oxide immobilized copper phthalocyanine tetrasulphonamide catalyst in the
presence of N,N0-dicyclohexylcarbodiimide (DCC) as a dehydrating agent is described. The presence of a
dehydrating agent was found to be vital and in its absence the yield of DMC was found to be decreased
significantly. Under the optimized reaction conditions, the maximum yield of DMC reaches up to 13.3%.
Although the homogeneous copper phthalocyanine tetrasulphonamide catalyst provided a little higher
yield of DMC (14.2%), the facile recovery and recycling ability of the heterogeneous catalyst make the
developed method more attractive from environmental and economical viewpoints.
The document summarizes research on the stability of lead telluride (PbTe) quantum dots. PbTe QDs show promising properties for optoelectronic devices but are unstable when exposed to oxygen. The document studies the oxidation of various sized PbTe and lead selenide (PbSe) QDs over time when exposed to air and nitrogen. PbTe QDs oxidize much more rapidly than PbSe QDs when in solution. However, coating PbTe QD films with alumina provides effective long-term protection from oxidation.
Synthesis and optimisation of ir o2 electrocatalysts by adams fusion method f...sudesh789
This document discusses the synthesis and optimization of iridium dioxide (IrO2) electrocatalysts for use in solid polymer electrolyte electrolyzers through an adaptation of the Adams fusion method. The synthesis duration and temperature were varied to determine their effect on the physical and electrochemical properties of the IrO2 catalysts. X-ray diffraction analysis showed that increasing the synthesis duration and temperature increased the crystallinity and particle size of the IrO2. Chronoamperometry testing revealed that a synthesis of 2 hours at 350°C produced an IrO2 catalyst with better electrocatalytic activity for oxygen evolution than a commercial IrO2 catalyst.
Synthesis and optimisation of ir o2 electrocatalysts by adams fusion method f...materials87
The document describes the synthesis and optimization of iridium dioxide (IrO2) electrocatalysts for oxygen evolution reaction (OER) in solid polymer electrolyte electrolyzers. IrO2 was synthesized using an Adams fusion method by varying synthesis duration (0.5-4 hours) and temperature (250-500°C). Characterization showed that increasing synthesis time and temperature improved crystallinity and increased particle size. Electrochemical testing revealed that IrO2 synthesized for 2 hours at 350°C exhibited the best electrocatalytic activity toward OER compared to a commercial IrO2 catalyst. Higher temperatures and longer times favored larger, more crystalline particles but decreased surface area and activity.
The document summarizes a study that used a palladium catalyst to synthesize benzofuran through a Sonogashira coupling reaction between 5-iodovanillin and 3-methyl-3-butyne-2-ol. The reaction was carried out using various amounts of palladium acetate, triphenylphosphine, and solvent. NMR spectroscopy showed the product formed, though it was impure likely due to side reactions promoted by the copper co-catalyst. While the reaction showed good atom economy, the yields were relatively low at 7.45% maximum. Further optimization is needed to improve purity and yields.
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
Benzoquinone Ketene intermediate in the synthesis of poly 2-HBAMatt Hettinger
This document summarizes a research article that investigated the role of a benzoquinoneketene intermediate in the base-catalyzed polymerization of poly-2-hydroxybenzoic acid (poly-2-HBA). The researchers synthesized a dimer of 2-hydroxybenzoic acid (2-HBA) and showed that it polymerizes to poly-2-HBA with a base, implicating the ketoketene intermediate. A control dimer that cannot form the ketoketene did not polymerize. Additionally, secondary amines trapped the ketoketene as monomeric amides, further supporting it as an intermediate. The results indicate that ketoketene formation and reaction plays a
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.
1) Self-assembled monolayer coated gold nanoparticles catalyze the aerobic oxidation of alpha-hydroxy ketones to aryl 1,2-diketones in water.
2) This provides an efficient one-pot synthesis of quinoxaline derivatives by in situ oxidation of alpha-hydroxy ketones and subsequent condensation with aryl 1,2-diamines in water.
3) 4-Aminothiophenol self-assembled monolayer coated gold nanoparticles were found to be an effective catalyst for these reactions, providing good to excellent yields of products under mild conditions in water.
The document describes the carbon nanotube-gold nanohybrid (AuCNT) catalyzed N-formylation of various primary and secondary amines using aqueous formaldehyde. Key findings include:
1) AuCNT catalyzes the room temperature N-formylation of various primary and secondary amines with aqueous formaldehyde, affording formamides in excellent yields.
2) The reaction proceeds with low catalyst loading (0.34 mol%), excellent chemoselectivity, and recyclability of the AuCNT catalyst.
3) Control experiments confirm the AuCNT nanohybrid is the active catalytic species, and the reaction proceeds through a hemiaminal intermediate that is oxidized to the
A graphene/hemin hybrid material as an efficient green catalyst for stereosel...Pawan Kumar
The document describes a study investigating a hemin/graphene composite catalyst for the stereoselective olefination of aldehydes using ethyl diazoacetate.
1) A hemin/graphene oxide composite was prepared and found to efficiently catalyze the olefination of aromatic aldehydes with high (E)-selectivity, showing its potential as a heterogeneous catalyst.
2) The catalyst could be easily recovered from the reaction mixture and reused several times without significant loss of activity or selectivity.
3) A variety of substituted aromatic and alicyclic aldehydes underwent olefination using this catalyst, providing moderate to high product yields and stereoselectivity.
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.
1) The document investigates the ability of polydiacetylene (PDA) compounds to change color irreversibly upon heating. It studies this property for eicosa-9,11-diyne and 10,12-pentacosadiynoic acid, finding color changes at 45°C and 70°C respectively.
2) A 50/50 mixture of the two compounds changes color between 50-60°C, indicating an intermediate transition temperature.
3) The PDA compounds only polymerize in the solid state on cellulose filter paper under UV light. Solvent effects and functionalization could allow polymerization into films for applications like intelligent labels.
Effects of heat treatment on the catalytic activity and methanol tolerance of...sunidevi
This document summarizes a study on the effects of heat treatment on the catalytic activity and methanol tolerance of carbon-supported platinum alloys. Carbon-supported platinum (Pt/C) and platinum alloy (Pt-Co/C, Pt-Cu/C, Pt-Fe/C, Pt-Ni/C) catalysts were subjected to heat treatments at different temperatures. X-ray diffraction, transmission electron microscopy, and electrochemical measurements were used to characterize the catalysts and evaluate their oxygen reduction reaction activity and methanol tolerance. The results showed that heat treatment improved catalytic activity by increasing particle size but the optimal temperature depended on the catalyst. Pt-Cu/C treated at 350°C showed the highest activity and
A powerful and convenient reaction procedure for the C-N coupling reaction (the Buchwald-Hartwig reaction), yielding products of N-arylanilines and N-arylamines in both conventional heating and microwave irradiation has been reported. The protocol utilizes a stable and new supper ferromagnetic nanoparticle chelating N-heterocyclic dicarbene palladium(II) complex (Pd-NHC) as catalyst which helps/allows us to complete the reaction with only 0.002 mol% Pd producing high yield products. We also examined the reusability of the catalyst. It was found that the catalyst could be recovered by external magnetic field and reused for seven times without obvious loss in catalytic activity.
The document describes a study of tetraphenylethene-triphenylamine (TPE-TPA) oligomers and a polymer. A series of oligomers (DATE, DTAE, DTDAE) and a polymer (PTAE) were synthesized using McMurry coupling and other reactions. All molecules showed aggregation-induced emission (AIE), emitting strongly in the solid state but very weakly in solution. Emission wavelengths and quantum yields varied with molecular structure, peaking for the largest oligomer DTDAE. The polymer had lower solubility and broader NMR peaks due to its large size. This work achieved both efficient solid-state emission and hole transport capability by combining TPE and TPA mo
A facile synthesis method produced highly active Pd nanoparticle catalysts for oxygen reduction reaction (ORR) in under 5 minutes. An electrode was dipped in separate solutions of reducing agent and Pd ions to deposit amorphous Pd nanoparticles. Repeatedly dipping the electrode increased catalytic activity, with the highest activity achieved after 12 cycles of 20 seconds each. The Pd nanoparticles produced using sodium hypophosphite as the reducing agent showed superior ORR activity compared to commercial Pt/C catalysts.
Electro catalytic performance of pt-supported poly (o-phenylenediamine) micro...sunitha81
Poly (o-phenylenediamine) (PoPD) microrods were obtained by interfacial
polymerization using ferric chloride as oxidant and without any template or
functional dopant. Pt/PoPD nanocatalysts were prepared by the reduction of chloroplatinic
acid with sodium borohydride, and the composite catalysts formed were
characterized by X-ray diffraction and electrochemical methods. The nanocomposite
of Pt/PoPD microrods has been explored for their electro-catalytic performance
towards oxidation of methanol. The electro-catalytic activity of Pt/PoPD was
found to be much higher (current density 1.96 mA/cm2 at 0.70 V) in comparison to
Pt/Vulcan electrodes (the current density values of 1.56 mA/cm2 at 0.71 V) which
may be attributed to the microrod morphology of PoPD that facilitate the effective
dispersion of Pt particles and easier access of methanol towards the catalytic sites.
One pot synthesis of chain-like palladium nanocubes and their enhanced electr...tshankar20134
This document describes a one-pot synthesis of chain-like palladium nanocubes and their enhanced electrocatalytic activity. A simple aqueous approach is used to produce anisotropic cubic chain-like Pd nanostructures using the neurotransmitter 5-hydroxytryptamine. Scanning electron microscopy images show the nanocubes have sizes between 140-210 nm and form chain-like branched structures. Testing shows the cubic chain-like nanostructures have over 11 times greater electrocatalytic activity for oxidizing formic acid, methanol, and ethanol compared to spherical nanoparticles and commercial Pd/C catalysts. The enhanced performance makes them promising multipurpose catalysts for direct fuel cells.
This document summarizes recent work on using metal-free catalysts for activating and converting carbon dioxide (CO2). It describes how certain organic molecules like porphyrins and carbon nitrides can catalyze the formation of carbamates from CO2, the first step in natural photosynthesis. The document outlines several studies showing how modified carbon nitrides can catalyze reactions like converting CO2 to cyclic carbonates and reducing it to methanol. It concludes that while carbon nitrides show promise as efficient metal-free CO2 capture and conversion catalysts, more research is still needed to fully understand and optimize their catalytic properties and activities.
This document discusses a study on the correlation between the annealing-induced growth of CdTe nanocrystals and the performance of PPV:CdTe hybrid solar cells. The key findings are:
1) Increasing the CdTe nanocrystal concentration or annealing temperature caused the CdTe nanocrystals to grow larger via dynamic coalescence.
2) Transmission electron microscopy and X-ray diffraction analysis showed that at higher annealing temperatures, the CdTe nanocrystals grew to around 26 nm in size with a spacing of 6-12 nm, forming a percolation network.
3) The best performing solar cells had a CdTe concentration of 30 mg/mL and were anne
Electrodeposited nanostructured a-Fe2O3 thin films for solar water splitting:...North Breeze
This document describes a study on the effects of platinum (Pt) doping on the photoelectrochemical performance of nanostructured alpha-iron oxide (α-Fe2O3) thin films deposited via electrodeposition. Un-doped and Pt-doped α-Fe2O3 thin films were characterized using various techniques. The results showed that Pt doping increased the density of small nanoparticles in the films and enhanced the photocurrent density for water splitting by up to a factor of 1.4 compared to un-doped films. The highest photocurrent density of 0.56 mA/cm2 was achieved for a 3% Pt-doped film. Electrochemical impedance analysis also revealed that Pt d
Synthesis and optimisation of ir o2 electrocatalysts by adams fusion method f...materials87
The document describes the synthesis and optimization of iridium dioxide (IrO2) electrocatalysts for oxygen evolution reaction (OER) in solid polymer electrolyte electrolyzers. IrO2 was synthesized using an Adams fusion method by varying synthesis duration (0.5-4 hours) and temperature (250-500°C). Characterization showed that increasing synthesis time and temperature improved crystallinity and increased particle size. Electrochemical testing revealed that IrO2 synthesized for 2 hours at 350°C exhibited the best electrocatalytic activity toward OER compared to a commercial IrO2 catalyst. Higher temperatures and longer times favored larger, more crystalline particles but decreased surface area and activity.
The document summarizes a study that used a palladium catalyst to synthesize benzofuran through a Sonogashira coupling reaction between 5-iodovanillin and 3-methyl-3-butyne-2-ol. The reaction was carried out using various amounts of palladium acetate, triphenylphosphine, and solvent. NMR spectroscopy showed the product formed, though it was impure likely due to side reactions promoted by the copper co-catalyst. While the reaction showed good atom economy, the yields were relatively low at 7.45% maximum. Further optimization is needed to improve purity and yields.
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
Benzoquinone Ketene intermediate in the synthesis of poly 2-HBAMatt Hettinger
This document summarizes a research article that investigated the role of a benzoquinoneketene intermediate in the base-catalyzed polymerization of poly-2-hydroxybenzoic acid (poly-2-HBA). The researchers synthesized a dimer of 2-hydroxybenzoic acid (2-HBA) and showed that it polymerizes to poly-2-HBA with a base, implicating the ketoketene intermediate. A control dimer that cannot form the ketoketene did not polymerize. Additionally, secondary amines trapped the ketoketene as monomeric amides, further supporting it as an intermediate. The results indicate that ketoketene formation and reaction plays a
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.
1) Self-assembled monolayer coated gold nanoparticles catalyze the aerobic oxidation of alpha-hydroxy ketones to aryl 1,2-diketones in water.
2) This provides an efficient one-pot synthesis of quinoxaline derivatives by in situ oxidation of alpha-hydroxy ketones and subsequent condensation with aryl 1,2-diamines in water.
3) 4-Aminothiophenol self-assembled monolayer coated gold nanoparticles were found to be an effective catalyst for these reactions, providing good to excellent yields of products under mild conditions in water.
The document describes the carbon nanotube-gold nanohybrid (AuCNT) catalyzed N-formylation of various primary and secondary amines using aqueous formaldehyde. Key findings include:
1) AuCNT catalyzes the room temperature N-formylation of various primary and secondary amines with aqueous formaldehyde, affording formamides in excellent yields.
2) The reaction proceeds with low catalyst loading (0.34 mol%), excellent chemoselectivity, and recyclability of the AuCNT catalyst.
3) Control experiments confirm the AuCNT nanohybrid is the active catalytic species, and the reaction proceeds through a hemiaminal intermediate that is oxidized to the
A graphene/hemin hybrid material as an efficient green catalyst for stereosel...Pawan Kumar
The document describes a study investigating a hemin/graphene composite catalyst for the stereoselective olefination of aldehydes using ethyl diazoacetate.
1) A hemin/graphene oxide composite was prepared and found to efficiently catalyze the olefination of aromatic aldehydes with high (E)-selectivity, showing its potential as a heterogeneous catalyst.
2) The catalyst could be easily recovered from the reaction mixture and reused several times without significant loss of activity or selectivity.
3) A variety of substituted aromatic and alicyclic aldehydes underwent olefination using this catalyst, providing moderate to high product yields and stereoselectivity.
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.
1) The document investigates the ability of polydiacetylene (PDA) compounds to change color irreversibly upon heating. It studies this property for eicosa-9,11-diyne and 10,12-pentacosadiynoic acid, finding color changes at 45°C and 70°C respectively.
2) A 50/50 mixture of the two compounds changes color between 50-60°C, indicating an intermediate transition temperature.
3) The PDA compounds only polymerize in the solid state on cellulose filter paper under UV light. Solvent effects and functionalization could allow polymerization into films for applications like intelligent labels.
Effects of heat treatment on the catalytic activity and methanol tolerance of...sunidevi
This document summarizes a study on the effects of heat treatment on the catalytic activity and methanol tolerance of carbon-supported platinum alloys. Carbon-supported platinum (Pt/C) and platinum alloy (Pt-Co/C, Pt-Cu/C, Pt-Fe/C, Pt-Ni/C) catalysts were subjected to heat treatments at different temperatures. X-ray diffraction, transmission electron microscopy, and electrochemical measurements were used to characterize the catalysts and evaluate their oxygen reduction reaction activity and methanol tolerance. The results showed that heat treatment improved catalytic activity by increasing particle size but the optimal temperature depended on the catalyst. Pt-Cu/C treated at 350°C showed the highest activity and
A powerful and convenient reaction procedure for the C-N coupling reaction (the Buchwald-Hartwig reaction), yielding products of N-arylanilines and N-arylamines in both conventional heating and microwave irradiation has been reported. The protocol utilizes a stable and new supper ferromagnetic nanoparticle chelating N-heterocyclic dicarbene palladium(II) complex (Pd-NHC) as catalyst which helps/allows us to complete the reaction with only 0.002 mol% Pd producing high yield products. We also examined the reusability of the catalyst. It was found that the catalyst could be recovered by external magnetic field and reused for seven times without obvious loss in catalytic activity.
The document describes a study of tetraphenylethene-triphenylamine (TPE-TPA) oligomers and a polymer. A series of oligomers (DATE, DTAE, DTDAE) and a polymer (PTAE) were synthesized using McMurry coupling and other reactions. All molecules showed aggregation-induced emission (AIE), emitting strongly in the solid state but very weakly in solution. Emission wavelengths and quantum yields varied with molecular structure, peaking for the largest oligomer DTDAE. The polymer had lower solubility and broader NMR peaks due to its large size. This work achieved both efficient solid-state emission and hole transport capability by combining TPE and TPA mo
A facile synthesis method produced highly active Pd nanoparticle catalysts for oxygen reduction reaction (ORR) in under 5 minutes. An electrode was dipped in separate solutions of reducing agent and Pd ions to deposit amorphous Pd nanoparticles. Repeatedly dipping the electrode increased catalytic activity, with the highest activity achieved after 12 cycles of 20 seconds each. The Pd nanoparticles produced using sodium hypophosphite as the reducing agent showed superior ORR activity compared to commercial Pt/C catalysts.
Electro catalytic performance of pt-supported poly (o-phenylenediamine) micro...sunitha81
Poly (o-phenylenediamine) (PoPD) microrods were obtained by interfacial
polymerization using ferric chloride as oxidant and without any template or
functional dopant. Pt/PoPD nanocatalysts were prepared by the reduction of chloroplatinic
acid with sodium borohydride, and the composite catalysts formed were
characterized by X-ray diffraction and electrochemical methods. The nanocomposite
of Pt/PoPD microrods has been explored for their electro-catalytic performance
towards oxidation of methanol. The electro-catalytic activity of Pt/PoPD was
found to be much higher (current density 1.96 mA/cm2 at 0.70 V) in comparison to
Pt/Vulcan electrodes (the current density values of 1.56 mA/cm2 at 0.71 V) which
may be attributed to the microrod morphology of PoPD that facilitate the effective
dispersion of Pt particles and easier access of methanol towards the catalytic sites.
One pot synthesis of chain-like palladium nanocubes and their enhanced electr...tshankar20134
This document describes a one-pot synthesis of chain-like palladium nanocubes and their enhanced electrocatalytic activity. A simple aqueous approach is used to produce anisotropic cubic chain-like Pd nanostructures using the neurotransmitter 5-hydroxytryptamine. Scanning electron microscopy images show the nanocubes have sizes between 140-210 nm and form chain-like branched structures. Testing shows the cubic chain-like nanostructures have over 11 times greater electrocatalytic activity for oxidizing formic acid, methanol, and ethanol compared to spherical nanoparticles and commercial Pd/C catalysts. The enhanced performance makes them promising multipurpose catalysts for direct fuel cells.
This document summarizes recent work on using metal-free catalysts for activating and converting carbon dioxide (CO2). It describes how certain organic molecules like porphyrins and carbon nitrides can catalyze the formation of carbamates from CO2, the first step in natural photosynthesis. The document outlines several studies showing how modified carbon nitrides can catalyze reactions like converting CO2 to cyclic carbonates and reducing it to methanol. It concludes that while carbon nitrides show promise as efficient metal-free CO2 capture and conversion catalysts, more research is still needed to fully understand and optimize their catalytic properties and activities.
This document discusses a study on the correlation between the annealing-induced growth of CdTe nanocrystals and the performance of PPV:CdTe hybrid solar cells. The key findings are:
1) Increasing the CdTe nanocrystal concentration or annealing temperature caused the CdTe nanocrystals to grow larger via dynamic coalescence.
2) Transmission electron microscopy and X-ray diffraction analysis showed that at higher annealing temperatures, the CdTe nanocrystals grew to around 26 nm in size with a spacing of 6-12 nm, forming a percolation network.
3) The best performing solar cells had a CdTe concentration of 30 mg/mL and were anne
Electrodeposited nanostructured a-Fe2O3 thin films for solar water splitting:...North Breeze
This document describes a study on the effects of platinum (Pt) doping on the photoelectrochemical performance of nanostructured alpha-iron oxide (α-Fe2O3) thin films deposited via electrodeposition. Un-doped and Pt-doped α-Fe2O3 thin films were characterized using various techniques. The results showed that Pt doping increased the density of small nanoparticles in the films and enhanced the photocurrent density for water splitting by up to a factor of 1.4 compared to un-doped films. The highest photocurrent density of 0.56 mA/cm2 was achieved for a 3% Pt-doped film. Electrochemical impedance analysis also revealed that Pt d
Maiyalagan,Electrochemical oxidation of methanol on pt v2 o5–c composite cata...kutty79
Platinum nanoparticles have been supported on V2O5–C composite through the reduction of chloroplatinic
acid with formaldehyde. The catalyst was characterized by X-ray diffraction and transmission electron
microscopy. Catalytic activity and stability for the oxidation of methanol were studied by using
cyclic voltammetry and chronoamperometry. Pt/V2O5–C composite anode catalyst on glassy carbon electrode
show higher electro-catalytic activity for the oxidation of methanol. High electro-catalytic activities
and good stabilities could be attributed to the synergistic effect between Pt and V2O5, avoiding the electrodes
being poisoned.
This document summarizes a study on the use of copper(I) oxide (Cu2O) nanoparticles to catalyze carbon-carbon (C-C) coupling reactions for the synthesis of polyphenylenediethynylenes. The study finds that under the reaction conditions, the Cu2O nanoparticles undergo substrate-induced leaching, forming homogeneous copper catalytic species in solution. This is evidenced by various characterization techniques and confirmed through a reactor study. The results show that the C-C coupling reactions proceed through both a heterogeneous pathway on the nanoparticle surface and a homogeneous pathway involving the leached copper species.
Heterostructured nanocomposite tin phthalocyanine@mesoporous ceria (SnPc@CeO2...Pawan Kumar
Heterostructured tin phthalocyanine supported to mesoporous ceria was synthesized and used a
photocatalyst for CO2 reduction under visible light. The photoreduction CO2 activities of the
heterostructures were investigated in the presence of triethylamine as sacrificial agent. The developed
photocatalyst exhibited high catalytic activity for photoreduction of CO2 and after 24 hours of visible
light irradiation 2342 mmol g1 cat of methanol (fMeOH ¼ 0.0223 or 2.23%) and 840 mmol g1 cat of CO
(fCO ¼ 0.0026 or 0.26%) were obtained as the major reaction products. The methanol formation rate
(RMeOH) and CO formation rate (RCO) was found to be 97.5 mmol h1 g1 cat and 35.0 mmol h1 g1 cat
respectively. While under the identical experimental conditions mesoporous ceria (meso-CeO2) gave
only 316 mmol g1 cat of methanol (fMeOH ¼ 0.003 or 0.30%) and 126 mmol g1 cat CO (fCO ¼ 0.0004
or 0.04%) with product formation rate RMeOH ¼ 13.2 mmol h1 g1 cat and RCO ¼ 5.3 mmol h1 g1 cat.
Furthermore, the recovered catalyst showed consistent catalytic activity for at least five runs without any
significant loss in product yields
Synthesis and optimisation of ir o2 electrocatalysts by adams fusion method f...tshankar20134
The document summarizes research into optimizing IrO2 as an electrocatalyst for oxygen evolution in solid polymer electrolyte electrolyzers. IrO2 was synthesized using the Adams fusion method, varying synthesis duration from 0.5-4 hours and temperature from 250-500°C. Characterization showed that increasing duration and temperature increased crystallinity and particle size. Electrochemical testing found that IrO2 synthesized for 2 hours at 350°C had the best catalytic activity for oxygen evolution, outperforming a commercial IrO2. Higher temperatures favored formation of the active IrO2 phase but also led to larger particle sizes which decreased activity. Lower than 350°C did not favor IrO2 formation.
This document summarizes research on developing Pt/V2O5-C composite catalysts for methanol oxidation in direct methanol fuel cells (DMFCs). Pt nanoparticles were dispersed on a V2O5-C composite support through chemical reduction. The catalyst was characterized using XRD and TEM, which showed the formation of small Pt nanoparticles (~3 nm) on the support. Electrochemical testing showed that the Pt/V2O5-C composite catalyst had higher catalytic activity for methanol oxidation compared to a commercial Pt/C catalyst, as indicated by a more positive onset potential and higher forward/reverse peak current ratios. The composite catalyst also demonstrated comparable stability during chronoamperometry testing. The improved performance is attributed to
This document summarizes research on developing Pt/V2O5-C composite catalysts for methanol oxidation in direct methanol fuel cells (DMFCs). Pt nanoparticles were dispersed on a V2O5-C composite support through chemical reduction. The catalyst was characterized using XRD and TEM, which showed the formation of small Pt nanoparticles on the support. Electrochemical testing showed that the Pt/V2O5-C composite catalyst had higher catalytic activity for methanol oxidation compared to a commercial Pt/C catalyst, as indicated by a more positive onset potential and higher forward/reverse peak current ratios. The composite catalyst also demonstrated comparable stability during chronoamperometry testing. The improved performance is attributed to a synergistic effect
This document discusses research on electrodepositing CdSe thin films from an acidic aqueous electrolytic bath containing organic additives, specifically monosodium L-glutamate and choline chloride. The films were characterized using XRD and SEM-EDAX. It was found that both additives led to more uniform and better crystallized deposits than without additives. Films with monosodium L-glutamate showed improved photoresponse in photoelectrochemical tests, while choline chloride led to decreased photoconductivity. The organic ions from the additives are potentially adsorbed on the CdSe, introducing defects that modify the electric properties.
A facile route for nitrogen doped hollow graphitic carbonumarkhalid532
1) A facile route is presented for synthesizing nitrogen-doped hollow graphitic carbon spheres (NHGCSs) through the direct pyrolysis of solid melamine–formaldehyde (MF) resin spheres.
2) The MF resin spheres are prepared via a hydrothermal method without templates or catalysts, and pyrolyzed at temperatures above 400°C to form hollow carbon spheres with graphitic carbon shells.
3) The NHGCSs exhibit excellent capacitive performance as electrode materials for supercapacitors, achieving a high specific capacitance of 306 Fg-1 at 0.1 A g-1.
The document discusses catalytic interfaces and techniques for probing their dynamics. It defines catalytic interfaces as boundaries between different phases, such as solid-gas or solid-liquid, where catalysis occurs. Dynamic processes at these interfaces include surface restructuring, oxidation/reduction, and atom migration. In situ techniques like environmental transmission electron microscopy (ETEM) and high pressure scanning tunneling microscopy allow observing these interface dynamics under reaction conditions. ETEM studies have visualized phenomena like carbon nanofiber growth, nanoparticle sintering, and surface reconstructions during catalysis. These techniques provide insights into catalyst deactivation mechanisms and ways to improve activity.
Synthesis, Characterization and Electro analytical Applications of Nitrogen D...IRJET Journal
This document summarizes research on synthesizing and characterizing nitrogen-doped ordered mesoporous carbon (CMK-3) for use as a modified electrode in electrochemical analysis. CMK-3 was synthesized using honey as a natural carbon source and SBA-15 mesoporous silica as a template. Characterization with XRD, BET, SEM and TEM showed the carbon replicated the hexagonal structure of SBA-15 and had a surface area of 587.8 m2/g. Cyclic voltammetry demonstrated the CMK-3 modified electrode could selectively determine dopamine, L-cysteine, ascorbic acid and paracetamol through well-defined oxidative/reductive peaks
This document characterizes cellulose nanocrystals grafted with organic acid chlorides of different sizes. The nanocrystals were obtained from ramie fibers through acid hydrolysis and then chemically modified through grafting with hexanoyl chloride, lauroyl chloride, and stearoyl chloride. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy were used to characterize the morphology, crystallinity, and occurrence of chemical modification. The objective of the surface chemical treatment was to enhance the nonpolar nature and improve dispersibility of the nanocrystals in nonpolar polymeric matrices.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
IrO2 as an anodic electrocatalyst for the oxygen evolution reaction (OER) in solid polymer electrolyte (SPE)
electrolysers was synthesised by adapting the Adams fusion method. Optimisation of the IrO2 electrocatalyst was achieved
by varying the synthesis duration (0.5 – 4 hours) and temperature (250 - 500°C). The physical properties of the
electrocatalysts were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and
x-ray diffraction (XRD). Electrochemical characterisation of the electrocatalysts toward the OER was evaluated by
chronoamperometry (CA). CA analysis revealed the best electrocatalytic activity towards the OER for IrO2 synthesised
for 2 hours at 350oC which displayed a better electrocatalytic activity than the commercial IrO2 electrocatalyst used in this
study. XRD and TEM analyses revealed an increase in crystallinity and average particle size with increasing synthesis
duration and temperature which accounted for the decreasing electrocatalytic activity. At 250°C the formation of an active
IrO2 electrocatalyst was not favoured.
Similar to The processing of cd se polymer nanocomposites (20)
This document provides a résumé for Dr. Yogesh P. Patil. It outlines his educational background, work experience, research interests, publications, projects, and administrative responsibilities. Some key details include:
- He holds a Ph.D. in Polymer Technology and works as an Associate Professor of Chemistry.
- His research interests include materials chemistry with a focus on polymers, fuels, and water treatment.
- He has over 20 years of experience in teaching, research, and administrative roles and has numerous publications, projects, and awards.
- His current responsibilities include teaching engineering chemistry, managing research projects, and administrative coordination as Head of the Department.
The document discusses the role of chemistry in engineering. It provides examples of how chemistry is used in various applications such as manufacturing fertilizers, pharmaceutical drugs, synthetic fibers, fuels, and metals. Chemistry is also used to understand biological processes. Quantum dots are discussed as a material with applications in bioimaging, drug delivery, and cancer therapies due to their optical and electrical properties. Carbon quantum dots and graphene quantum dots are also mentioned for their use in water treatment and membrane technologies due to properties like small size and functional groups. The document concludes by discussing how Samsung and LG are moving away from LCD screens in favor of quantum dot and OLED display technologies.
The document discusses the role of chemistry in various engineering applications. It provides examples of how chemistry is used in solar cells, magnetically elevated trains, and sensor technology. Quantum dots and their uses are also explained in detail. The document highlights how chemistry is essential to materials processing and manufacturing across many industries including energy, transportation, and electronics.
The document discusses biofuels, including their need, benefits, and analysis. It provides an introduction to biofuels and their role in reducing carbon emissions. It then discusses the need for biofuels in terms of their ease of use in vehicles, ability to provide energy security, potential for economic development, and ability to reduce greenhouse gas emissions. However, biofuels also face objections regarding their economic viability and environmental impacts. The document concludes by discussing life cycle analysis of biofuels and perspectives on biodiesel.
Electrical Measurements for Semiconducting DevicesYogesh Patil
The document discusses electrical measurements for semiconducting devices. It describes current-voltage (I-V) characteristics and capacitance-voltage (C-V) characteristics, which are important for understanding the performance of solar cells and other semiconductor applications. The I-V characteristics provide information about the ideality factor and barrier potential of devices like diodes and solar cells. C-V measurements allow determining parameters like doping concentration and flat band potential. Understanding these electrical measurements is key to improving the efficiency of devices using heterojunctions of wide bandgap semiconductors.
This document is a resume for Dr. Yogesh P. Patil summarizing his educational and professional experience. It lists his educational qualifications including a Ph.D. in Chemistry from North Maharashtra University. It details his work experience as a lecturer and research associate, and lists his areas of research interest and publications. The resume provides contact information and highlights his teaching experience, publications, grants received, and administrative roles held.
The document discusses the history and development of chemistry from ancient times to the modern era. It describes how early alchemists studied chemistry under the goals of discovering the philosopher's stone and divine solution. Several important 18th century scientists are highlighted for their contributions, including Cavendish who discovered the mass of the Earth, Lavoisier who established the modern system of chemical nomenclature, and Faraday who invented the electric motor. The development of technology during the Industrial Revolution and advances in fields like physics, medicine, and computers in the 20th century are also summarized.
1. The document discusses the chemistry behind feelings of love, lust, and attraction. Key chemicals involved include dopamine, norepinephrine, oxytocin, vasopressin, phenylethylamine, testosterone, and estrogen.
2. These chemicals help drive the three stages of love - lust, attraction, and attachment. Lust is driven by sex hormones, attraction by dopamine, norepinephrine and serotonin, and attachment by oxytocin and vasopressin which facilitate bonding.
3. Keeping love alive involves triggering these same chemical responses through novelty, touch, and intimacy to sustain romantic love over the long term.
This document compares the synthesis of oximes using traditional chemical methods versus ultrasonic irradiation. Oximes are important organic intermediates. The traditional method involves refluxing carbonyl compounds with hydroxylamine hydrochloride solution in ethanol as a solvent, taking 50-60 minutes and yielding 70-75%. Using ultrasonic irradiation, the same oximes were synthesized without solvent in 10-20 minutes, yielding 75-85%, which is higher than the traditional method. Yields were lowest for benzophenone oxime due to electron donation by phenyl groups decreasing carbonyl reactivity. Yields were highest for 4-chlorobenzaldehyde oxime due to electron withdrawal increasing reactivity. Thin layer chromatography confirmed the oximes produced
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
Walmart Business+ and Spark Good for Nonprofits.pdfTechSoup
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it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
What sets Denis apart is his comprehensive understanding of Business and Systems Analysis technologies, honed through involvement in all phases of the Software Development Lifecycle (SDLC). From meticulous requirements gathering to precise analysis, innovative design, rigorous development, thorough testing, and successful implementation, he has consistently delivered exceptional results.
Throughout his career, he has taken on multifaceted roles, from leading technical project management teams to owning solutions that drive operational excellence. His conscientious and proactive approach is unwavering, whether he is working independently or collaboratively within a team. His ability to connect with colleagues on a personal level underscores his commitment to fostering a harmonious and productive workplace environment.
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This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
How to Make a Field Mandatory in Odoo 17Celine George
In Odoo, making a field required can be done through both Python code and XML views. When you set the required attribute to True in Python code, it makes the field required across all views where it's used. Conversely, when you set the required attribute in XML views, it makes the field required only in the context of that particular view.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
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2. P.K. Khanna et al. / Materials Chemistry and Physics 97 (2006) 288–294 289
in optoelectronics, normally the polymeric matrices are the
most desirous as the film of the nano particles/polymer com-
posite can be cast easily and thus offer direct use in devices.
The re-dispersed nanoparticles when loaded in polymer by
dissolution of the as-synthesized particles because solubility
(in terms of re-dispersion) of nanoparticles can not be guar-
anteed. This thus leads to difficulties in knowing the concen-
tration of nanoparticles within the polymer. However, if the
nanoparticles are synthesized in polymeric reaction medium,
such issues can be tackled with much ease. In addition,
multi-stage loading of the particles can be avoided. The most
important requirement of course, is the use of suitable pre-
cursors, i.e. the precursors that can be easily converted to end
product during the reaction. Organometallic precursors are
known to offer these advantages. Release of selenium upon
thermolysis of 1,2,3-selenadiazoles has been well studied and
widely utilized in synthetic chemistry [13,14]. Recently, we
reported that the reaction of cycloalkeno-1,2,3-selendiazole
with metal salts, can lead to formation of fine powders of
CdSe and silver selenide [12,15–17]. Our initial efforts on
use of 1,2,3-selenadiazole as a source of selenium for semi-
conductor particles prompted us to test its suitability for
trappingtheseparticlesinpolymers.Inthepresentstudy,PVA
and PMMA is employed as surfactant-cum-stabilizer-cum-
matrix for CdSe nanoparticles after their in situ synthesis.
This, we believe, is a novel thought for generating nanopar-
ticles in polymer. Therefore, in the current work, reaction
of cadmium acetate with polymer followed by its reaction
with cycloocteno-1,2,3-selenadiazole has been successfully
attempted to generate a one-pot novel method for synthesis
of CdSe nanoparticles in the film and powder form trapped
in polymer.
2. Experimental
2.1. General
Cycloocteno-1,2,3-selenadiazole (4,5,6,7,8,9-hexahydro-
cycloocta-1,2,3-selenadiazole) was prepared by literature
method [13]. UV–vis spectra were recorded in DMF on a
Hitachi 3210 UV–vis spectrophotometer. Scanning electron
microscopy (SEM)/EDAX was done on a Philips XL-30
instrument. Powder X-ray diffraction patterns were mea-
sured using Cu K␣ radiation (λ = 1.5406 ˚A) on a Mini Flex
Rigaku Philips Model. The thermo gravimetric analysis of
the nanocomposite was carried out on a Perkin-Elmer Model
no. 7. The photoluminescence (PL) measurement were done
at Shimadzu centre at the University of Pune.
2.2. In situ synthesis of CdSe nanocrystals in poly(vinyl
alcohol)
PVA (1g) was taken in two-necked round bottom flask
in DMF and stirred at room temperature under nitrogen
atmosphere for 1 h. To it were added, cadmium acetate and
octeno-1,2,3-selenadiazole (in DMF) in 1:1 ratio at room
temperature. The reaction mixture was heated to 140 ± 5 ◦C.
The initial orange colloidal solution was obtained at about
80 ◦C, which indicated formation of nanosized CdSe by mon-
itoring the reaction by absorption spectroscopy. The reaction
was continued for a couple of hours. After cooling it down
to room temperature, it was centrifuged and washed with
toluene, methanol and finally with diethyl ether to obtain a
light brown powder.
2.3. In situ synthesis of CdSe nanoparticles in
polymethylmethacrylate [PMMA]
Polymethyl methacrylate (PMMA) 10 mL stock solution
(10 g/50 mL in DMF stored as stock solution under N2 atmo-
sphere) was taken in a round bottom Schlenk flask and the
volumewasincreasedtoabout30 mL.ThePMMAsolutionin
DMF was degassed and flushed with N2. To it, both cadmium
acetate (0.266 g, dissolved in 10 mL DMF) and cycloocteno-
1,2,3-selenadiazole (0.215 g dissolved in 10 mL DMF) were
added through a syringe. The reaction mixture was stirred
at 80–100 ◦C for 8 h under N2 atmosphere. The colour of
reaction mixture became slightly brown in about 2 h. The
reaction was continued for additional 5–6 h to obtain a sharp
absorption band. The heating was continued for another 2 h
to complete the reaction. Subsequently a brown transparent
film was cast by vacuum evaporation technique.
3. Results and discussion
Selenadiazole can be thermally converted to either (1)
cyclooctyne via extrusion of Se atom, or (2) 1,4-diselenin
due to dimerization of an intermediate [13]. The extrusion
lead to generation of highly reactive selenium, and this has
been exploited in the present work. In our earlier efforts, we
found that once the selenium is heated in any high boiling
solvent such as DMF and ethylene glycol, the released Se
immediately reacts with the metal ion present in the reac-
tion vessel producing bulk powders. In order to isolate CdSe
nanocrystals, we designed our experiments in such a way that
the released selenium should not react in the first place with
the metal ion.
Continued heating of selenadiazole in dipolar aprotic sol-
vent such as DMF containing PVA and cadmium salt resulted
in reddish colloidal solution, which by centrifugation, and
organic washings afforded brown colored powder of CdSe.
Schemes 1–3 shows a schematic mechanism of release of
selenium from selenadiazole and formation of CdSe/PVA
nanocomposite via reaction of either Cd-salt or Se with
hydrogen ions generated by the solvent. Similarly, the reac-
tion of Cd-salt with methylmethacrylate monomer in pres-
ence of a catalyst for polymerization, resulted in an orange
to red suspension. It is opined that the initial reaction of cad-
mium acetate with acrylate monomer may result in formation
of cadmium acrylate intermediate that subsequently polymer-
3. 290 P.K. Khanna et al. / Materials Chemistry and Physics 97 (2006) 288–294
Scheme 1. Mechanism for release of Se from selenadiazole.
Scheme 2. Proposed mechanism for formation of CdSe.
izes and reacts with the selenadiazole to generate polymer
embedded CdSe (Scheme 4).
UV–vis spectrum of CdSe/PVA and CdSe/PMMA reac-
tion solutions prepared following above methodology are
shown in Fig. 1(i) and (ii). The solution absorption spectrum
of CdSe/PVA nano-composite in DMF showed a sharp band
at about 550 nm (band gap 2.25 eV) suggesting a blue shift
in absorption wavelength with respect to bulk CdSe and the
pattern indicate that the particles have narrow size distribu-
tion in solution (Fig. 1(i)) however, the absorption spectrum
of CdSe/PMMA showed band at about 510 nm, indicating
that the PMMA is better than PVA for controlling particle
growth of CdSe (Fig. 1(ii)). The absorption bands of solution
and the film do not differ in their position thus indicating that
even after slight heating (for casting film) the particle size
distribution remain un-disturbed. This could be very useful
when considered for application of such composites in opto-
electronics. The band gap of bulk CdSe is reported to be
712 nm (1.74 eV) [18]. The present measurements show that
there is a blue shift of about 150–200 nm in comparison to the
band gap energy of bulk CdSe. The blue shifts in the absorp-
tion spectrum of semiconductors is observed due to quantum
confinement effect leading to increased energy-gap between
the highest occupied molecular orbitals (HOMO) and lowest
un-occupied molecular orbitals (LUMO) in semiconductors.
The absorption measurements thus show that octeno-1,2,3-
selenadiazole is a good source of selenium for preparation of
CdSe nanoparticles in PVA and PMMA.
The photoluminescence spectrum (Fig. 2) of
CdSe/PMMA film that was cast from the solution whose
UV–vis absorption spectrum is shown in Fig. 1(ii), gave a
peak at 530 nm at an excitation wavelength of 450 nm. The
absorption of this composite solution and film showed a band
at 510 nm thus a Stoke’s shift of about 25 nm is observed
in comparison to absorption band. Such Stokes shifting of
emission wavelength is a common feature of semiconductor
quantum dots. The bathochromic shift with reference to
UV–vis absorption value suggests that the emission arises
from re-combination from shallow trap states [11].
In the FTIR spectrum of pure PVA showed a band at
ν1375 cm−1 was normally observed due to the coupling
of O H vibrations at ν1420 cm−1 with the C H wagging
vibrations. The FTIR spectrum of CdSe/PVA nanocompos-
ite (Fig. 3(i)) show an increase in the transmittance and a
Scheme 3. Proposed mechanism of an in situ synthesis of CdSe nanoparticles in PVA.
4. P.K. Khanna et al. / Materials Chemistry and Physics 97 (2006) 288–294 291
Scheme 4. Proposed mechanism of an in situ synthesis of CdSe nanoparticles and polymerization of MMA monomer (represented in unit chain of polymer).
Fig. 1. UV–vis of (i) CdSe/PVA solution and (ii) CdSe/PMMA solution (a) and film (b).
Fig. 2. Photoluminescence spectrum of CdSe/PMMA film.
slight shift (about 20–25 cm−1) of the band at ν1375 cm−1,
whichindicatesthedecouplingbetweenO HandC Hvibra-
tions due to bonding interaction between O H and CdSe
nanoparticles. FTIR spectrum of PVA coated CdSe shows all
relevant peaks for PVA. The characterisitic peaks for –OH
is found to be at ν3375 cm−1 which is slightly shifted from
its original value of about ν3350 cm−1 in PVA alone. Similar
observation and findings have been reported for silver/PVA
nanocomposite and this could considered relevant to the IR
spectrum of CdSe/PVA [19]. Similarly, the IR measurement
of CdSe/PMMA (Fig. 3 (ii)) showed that the peaks have
become broad and these are shifted in their wave numbers
with respect to their original value in PMMA. The IR spec-
trum in transmission mode showed very broad peaks however
when the same was recorded in absorption mode, all peaks
due to PMMA were found to be present with slight broaden-
5. 292 P.K. Khanna et al. / Materials Chemistry and Physics 97 (2006) 288–294
Fig. 3. FTIR spectra (i) of CdSe/PVA powder (Transmittance mode) and (ii) of CdSe/PMMA film (absorbance mode).
Fig. 4. XRD of CdSe/PVA nanocomposite powder.
ing and the peak at ν1723 cm−1 is assigned to the ester group
of the PMMA. This peak is slightly shifted in the compos-
ite than the peak reported for PMMA alone at ν1728 cm−1
[20]. This indicate that the composite may have some chem-
ical bonding between the polymer and the surface of CdSe
particles.
Fig. 4 (XRD) shows peaks characteristic of cubic CdSe
[21]. All peaks of Bragg’s scattering in XRD of PVA/CdSe
nanocmposite are observed. The reflections at 1 1 1, 2 0 0,
2 2 0, 3 1 1, 2 2 2 are broad pattern due to size quantization
effect. It is well reported that a broad XRD pattern is sup-
portive of small particle size [21]. This is due to the fact
that during the reduction in particle size, the crystallinity of
the semiconductor particle is marginally lost and therefore
Bragg’s reflections are poor in such small particles. Calcula-
tion of particles size by use of Scherrer equation resulted in
a size of about <5 nm (Table 1a).
Table 1
Calculation of particle size and lattice spacing from XRD patterns of PVA/CdSe and PMMA/CdSe powders (from Figs. 4 and 5)
2θ (degrees) θ (degrees) Crystal planes Full width at half maximum (FWHM) aParticle size (nm) bLattice spacing ( ˚A)
(a) PVA/CdSe
25.66 12.80 1 1 1 3.118 2.6 3.476
42.08 21.04 2 2 0 2.203 3.8 2.144
49.67 24.80 3 1 1 1.734 5.0 1.835
(b) PMMA/CdSe
25.58 12.79 1 1 1 2.30 7.9 3.484
42.02 21.01 2 2 0 1.28 6.6 2.147
49.68 24.84 3 1 1 2.06 4.2 1.833
a Calculation done by Scherrer Equation, i.e. t = 0.9λ/β cos θ.
b Calculated by, i.e. d = n λ/(2sin θ) where n = 1.
Fig. 5. XRD of CdSe/PMMA nanocomposite powder.
Fig. 6. XRD of CdSe/PMMA nanocomposite film.
Figs. 5 and 6 show XRD pattern of the CdSe/PMMA pow-
der and film, respectively. It is seen from the figures that
in case of powder where the concentration of CdSe with
respect to polymer is about 20% (w/w), the XRD pattern
is very clear with peaks characteristic of cubic CdSe. All
peaks of Bragg’s scattering in CdSe/PMMA nanocmposite
6. P.K. Khanna et al. / Materials Chemistry and Physics 97 (2006) 288–294 293
are observed with broadening and the particles size calcu-
lation by Scherrer’s equation resulted in crystallite size of
about <10 nm (Table 1b). This is again due to size quantiza-
tion effect.
The reflections are further poorer in the XRD pattern of the
film that only gave a very broad pattern typically of amor-
phous characteristics (Fig. 6). As the peak at 2 theta at 42
could be seen in the figure, it suggested that the film has
some crytallinity.
TGA (Fig. 7) analysis showed a two-stage decomposi-
tion pattern for the CdSe/PVA nano-composite. Initial weight
loss at about 256 ◦C can be considered due to decomposi-
tion of PVA. The second-stage weight loss at about 820 ◦C
may be due to possible initial decomposition of CdSe. A
total of about 55% wt. loss was observed when the analy-
sis was done between room temperature to 900 ◦C at a rate
of 10 ◦C min−1 under nitrogen atmosphere. Similarly, TGA
(Fig. 8) of CdSe/PMMA analysis also showed a two-stage
decomposition pattern as against a three-step decomposition
pattern for PMMA alone. This indicated that the thermal sta-
bility of CdSe/PMMA nano-composite has been altered. The
analysis curve shows that the decomposition starts at about
200 ◦C and continues till 400 ◦C.
Fig. 7. TGA of PVA/CdSe film.
The CdSe/Polymer nanocomposites were analyzed by
scanning electron microscopy, which revealed that in case
of CdSe/PMMA film, tiny particles are spread across the
matrix (Fig. 9). There appears to be un-evenness in the film
morphology. This could be due to crystalline nature of the
particles present in the polymer. It was not possible to obtain
good quality SEM of CdSe/PVA due to charging of the
composite during analysis. Nonetheless, it is seen from the
picture (Fig. 9b) that the spherical particles are present in
Fig. 8. Thermogram of (a) PMMA and (b) CdSe/PMMA nanocomposite film.
Fig. 9. SEM pictures of (a) CdSe/PMMA and (b) CdSe/PVA nanocomposites.
7. 294 P.K. Khanna et al. / Materials Chemistry and Physics 97 (2006) 288–294
the matrix. The quality of the film that was obtained from
PMMA appears to be better than PVA and this further sug-
gests that PMMA is a better matrix in the present work than
PVA.
4. Conclusions
It is shown in the present work that cycloocteno-1,2,3-
seplenadiazolecanbesuccessfullyusedassourceofselenium
in synthesis of CdSe nanoparticles embedded in polymers.
The optical and other characterization shows that the band-
gap energy of CdSe is increased and that the final nanocom-
posite has cubic phase of CdSe. TGA suggest that the thermal
stability of the polymers has increased due to presence of
nanoparticles.
Acknowledgments
We thank Executive Director, C-MET for encouragement
and permission and DST (Govt. of India) for financial support
through grant no. SP/S1/H-34/99-Part-II. P.K.K. thanks, Mrs.
Rina Gorte, for initial experimental assistance.
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