This document summarizes a seminar presentation about irradiation effects in high melting oxides and the synthesis of new luminescent composite materials. The presentation covered self-introduction of the speaker, introduction to the topic, purpose of the study which was to investigate irradiation effects in oxides like MgAl2O4 and α-Al2O3 as well as synthesize luminescent composites. Experimental methods used included irradiation of samples using neutrons and electrons followed by measurement techniques like photoluminescence spectroscopy. Results showed irradiation induced defects in oxides and conversion of Sm3+ to Sm2+ in Na2SO4 under irradiation. In conclusion, irradiation was found to modify optical and structural properties of materials.
Characterization of different dopants in TiO2 Structure by Pulsed Laser Dep...sarmad
Characterization of different dopants in TiO2 Structure by Pulsed Laser Deposition
A thesis submitted By: Khaled Z.Yahya
Supervised by: Prof.Dr. Adawiya J.Haider Prof.Dr. Raad M.S.Al-Haddad
This document discusses the effect of heating rate on the structural and optical properties of silicon and magnesium co-doped zirconia nanopowders prepared by a sol-gel method. X-ray diffraction analysis showed that different heating rates between 1-10°C/min affected the formation of tetragonal and cubic phases, crystallinity, and particle size. Ultraviolet-visible spectroscopy showed that the band gap energy of the doped zirconia crystals decreased depending on the heating rate, with a minimum band gap of around 3-3.2 eV.
This document summarizes research on using antimony-impregnated activated carbon as an electrode for detecting heavy metal ions like cadmium and lead using anodic stripping voltammetry. The researchers impregnated activated carbon with different amounts of antimony and found that electrodes with 5% antimony by weight produced the highest peak currents - 29.2 microamps for cadmium and 49.4 microamps for lead in a 100 microgram per liter solution, outperforming previous methods. The results indicate antimony-impregnated activated carbon is an effective working electrode for detecting heavy metals at low concentrations.
M.Sc. Chemical Engineering Thesis Defense (Omer Farooqi)Omer Farooqi
This is the presentation for my M.Sc. research thesis. I worked on a novel electrode preparation method to carry out voltammetry in order to detect heavy metals in water.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
final accept-Optical and structural properties of TiO2 nanopowders with Co-Ce...nasrollah najibi ilkhchy
This document discusses a study on the optical and structural properties of TiO2 nanopowders doped with 2 mol% cerium and 4 mol% cobalt. X-ray diffraction analysis showed that cerium doping inhibited the formation of the rutile phase of titanium dioxide and promoted retention of the anatase phase at higher calcination temperatures. Optical absorption spectroscopy indicated that doping reduced the band gap of titanium dioxide from 3.21 eV to 3.14-3.20 eV. The crystallite size decreased with doping while the surface area increased compared to undoped titanium dioxide.
This document summarizes the synthesis and characterization of copper-doped nickel oxide (NiO) nanoparticles. Nickel oxide nanoparticles were synthesized using a chemical precipitation method with varying concentrations of copper doping (0, 2, 4, and 6 atomic%). The nanoparticles were characterized using X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, photoluminescence, and Raman spectroscopy. X-ray diffraction confirmed the nanoparticles had a face-centered cubic structure. Energy dispersive X-ray spectroscopy showed effective doping of copper into the nickel oxide lattice. Photoluminescence intensity increased with higher copper doping concentrations up to 4 atomic% but decreased at 6 atomic% due to increased particle size.
Characterization of different dopants in TiO2 Structure by Pulsed Laser Dep...sarmad
Characterization of different dopants in TiO2 Structure by Pulsed Laser Deposition
A thesis submitted By: Khaled Z.Yahya
Supervised by: Prof.Dr. Adawiya J.Haider Prof.Dr. Raad M.S.Al-Haddad
This document discusses the effect of heating rate on the structural and optical properties of silicon and magnesium co-doped zirconia nanopowders prepared by a sol-gel method. X-ray diffraction analysis showed that different heating rates between 1-10°C/min affected the formation of tetragonal and cubic phases, crystallinity, and particle size. Ultraviolet-visible spectroscopy showed that the band gap energy of the doped zirconia crystals decreased depending on the heating rate, with a minimum band gap of around 3-3.2 eV.
This document summarizes research on using antimony-impregnated activated carbon as an electrode for detecting heavy metal ions like cadmium and lead using anodic stripping voltammetry. The researchers impregnated activated carbon with different amounts of antimony and found that electrodes with 5% antimony by weight produced the highest peak currents - 29.2 microamps for cadmium and 49.4 microamps for lead in a 100 microgram per liter solution, outperforming previous methods. The results indicate antimony-impregnated activated carbon is an effective working electrode for detecting heavy metals at low concentrations.
M.Sc. Chemical Engineering Thesis Defense (Omer Farooqi)Omer Farooqi
This is the presentation for my M.Sc. research thesis. I worked on a novel electrode preparation method to carry out voltammetry in order to detect heavy metals in water.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
final accept-Optical and structural properties of TiO2 nanopowders with Co-Ce...nasrollah najibi ilkhchy
This document discusses a study on the optical and structural properties of TiO2 nanopowders doped with 2 mol% cerium and 4 mol% cobalt. X-ray diffraction analysis showed that cerium doping inhibited the formation of the rutile phase of titanium dioxide and promoted retention of the anatase phase at higher calcination temperatures. Optical absorption spectroscopy indicated that doping reduced the band gap of titanium dioxide from 3.21 eV to 3.14-3.20 eV. The crystallite size decreased with doping while the surface area increased compared to undoped titanium dioxide.
This document summarizes the synthesis and characterization of copper-doped nickel oxide (NiO) nanoparticles. Nickel oxide nanoparticles were synthesized using a chemical precipitation method with varying concentrations of copper doping (0, 2, 4, and 6 atomic%). The nanoparticles were characterized using X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, photoluminescence, and Raman spectroscopy. X-ray diffraction confirmed the nanoparticles had a face-centered cubic structure. Energy dispersive X-ray spectroscopy showed effective doping of copper into the nickel oxide lattice. Photoluminescence intensity increased with higher copper doping concentrations up to 4 atomic% but decreased at 6 atomic% due to increased particle size.
Harvesting Hot Holes in Plasmon-Coupled Ultrathin Photoanodes for High-Perfor...Pawan Kumar
The harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO2 and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO2 (a-TiO2). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO2 (Au@a-TiO2) generated 2.5 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm–2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO2 photoelectrodes produced a small positive photocurrent of 0.1 mA cm–2 even at a bias of −0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO2 and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al2O3 (Au@Al2O3) generated 0.02 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO2 in the extraction of holes in Au@a-TiO2 photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...Pawan Kumar
Bulk g-C3N4 is an earth-abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P-doping and size quantization are combined to synthesize highly fluorescent P-doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase-phase and rutile-phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight-driven water-splitting and as photocatalysts for surface catalytic reactions. Square-shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD-STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD-STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light-driven transformation of 4-nitrobenzenethiol (4-NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.
The document provides an overview of X-ray Photoelectron Spectroscopy (XPS) as a surface analysis technique. It describes how XPS works based on the photoelectric effect, and how it can be used to identify elements, chemical states, and compounds present on material surfaces. The key components of an XPS instrument are also outlined.
1. TiO2 is an effective photocatalyst for water splitting under UV light through generating electron-hole pairs, but has a large bandgap only absorbing UV light.
2. Nitrogen doping of TiO2 has been explored as a way to narrow the bandgap and enable absorption of visible light, but the exact chemical nature of incorporated nitrogen is unclear from characterization techniques.
3. Preparation methods can result in substitutional or interstitial nitrogen in the TiO2 lattice, but there is no clear correlation between method used and nitrogen state incorporated.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Co...Pawan Kumar
We present a potential solution to the problem of extraction of photogenerated holes from CdS nanocrystals and nanowires. The nanosheet form of C3N5 is a low-band-gap (Eg = 2.03 eV), azo-linked graphenic carbon nitride framework formed by the polymerization of melem hydrazine (MHP). C3N5 nanosheets were either wrapped around CdS nanorods (NRs) following the synthesis of pristine chalcogenide or intercalated among them by an in situ synthesis protocol to form two kinds of heterostructures, CdS-MHP and CdS-MHPINS, respectively. CdS-MHP improved the photocatalytic degradation rate of 4-nitrophenol by nearly an order of magnitude in comparison to bare CdS NRs. CdS-MHP also enhanced the sunlight-driven photocatalytic activity of bare CdS NWs for the decolorization of rhodamine B (RhB) by a remarkable 300% through the improved extraction and utilization of photogenerated holes due to surface passivation. More interestingly, CdS-MHP provided reaction pathway control over RhB degradation. In the absence of scavengers, CdS-MHP degraded RhB through the N-deethylation pathway. When either hole scavenger or electron scavenger was added to the RhB solution, the photocatalytic activity of CdS-MHP remained mostly unchanged, while the degradation mechanism shifted to the chromophore cleavage (cycloreversion) pathway. We investigated the optoelectronic properties of CdS-C3N5 heterojunctions using density functional theory (DFT) simulations, finite difference time domain (FDTD) simulations, time-resolved terahertz spectroscopy (TRTS), and photoconductivity measurements. TRTS indicated high carrier mobilities >450 cm2 V–1 s–1 and carrier relaxation times >60 ps for CdS-MHP, while CdS-MHPINS exhibited much lower mobilities <150 cm2 V–1 s–1 and short carrier relaxation times <20 ps. Hysteresis in the photoconductive J–V characteristics of CdS NWs disappeared in CdS-MHP, confirming surface passivation. Dispersion-corrected DFT simulations indicated a delocalized HOMO and a LUMO localized on C3N5 in CdS-MHP. C3N5, with its extended π-conjugation and low band gap, can function as a shuttle to extract carriers and excitons in nanostructured heterojunctions, and enhance performance in optoelectronic devices. Our results demonstrate how carrier dynamics in core–shell heterostructures can be manipulated to achieve control over the reaction mechanism in photocatalysis.
Growth and Characterization of Barium doped Potassium Hydrogen Phthalate Sing...IJERA Editor
The Non Linear Optical materials have acquired new significance with the advent of a large number of devices
utilizing solid state Laser sources. Potassium Hydrogen Phthalate one of the Non Linear Optical material having
superior non linear optical properties has been exploited for variety of application. In the present work, KHP
single crystals were grown by slow evaporation technique with Barium metal ion as a dopant. The grown
crystals were subjected to powder XRD analysis and the result shows that the Ba2+ ions does not alter the crystal
structure, but it enter into the crystal lattice of pure KHP. The optical transparency of the grown crystal was
studied by UV-Visible spectroscopy, the molecular structure was confirmed by FTIR analysis and its thermal
stability by TG/DTA analysis. The improved SHG efficiency of barium doped Potassium Hydrogen Phthalate
crystal could enhance the nonlinearity behaviour. In addition to this, the electrical parameter such as dielectric
constant was studied in detail.
This document discusses a study that used Laser-Induced Breakdown Spectroscopy (LIBS) to identify atomic and molecular emissions from potassium-based energetic materials. Samples of these materials were prepared as bulk pellets and thin films deposited on substrates. LIBS was used to obtain spectra from the samples in the ultraviolet-visible and infrared regions. Spectral lines were identified and matched to known atomic and molecular signatures to allow identification of the energetic materials.
TechBoost 2015 - Ghent University - Phosphors for lightingPhilippe Smet
Presentation on the history of lighting and the role of phosphors (luminescent materials) in lighting. From fluorescence lamps to white light emitting diodes (LEDs) for displays and general lighting.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...Pawan Kumar
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
The document summarizes the synthesis and characterization of TiO2 and nitrogen-doped TiO2 nanostructures for application in dye-sensitized solar cells. Key points include:
1) TiO2 nanotube powders and arrays were synthesized using an electrochemical anodization technique and characterized using various methods.
2) Nitrogen doping was used to modify the bandgap of TiO2.
3) The synthesized materials were used to fabricate dye-sensitized solar cells and their performance was tested for potential application in solar energy conversion.
The document discusses recycling phosphorescent powder from cathode ray tubes (CRTs) and fluorescent tubes. It aims to determine optimal leaching conditions to maximize recovery of precious lanthanide metals. Experimental techniques used include X-ray powder diffraction (XRD) to analyze sample composition, ICP-OES for elemental analysis, and scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) analysis. Experiments involved leaching CRT and fluorescent tube powders using various acids like nitric acid, aqua regia, and citric acid to identify conditions giving highest lanthanide recovery.
EMRS 2018 Replacing rare earth ions in LEDs (?)Philippe Smet
Two decades after the development of the blue light-emitting diode (LED), LEDs have quickly established themselves as the lighting technology of the future. The high efficiency, spectral tunability, lack of toxic compounds and a small footprint makes them far more attractive than other lighting technologies. The high efficiency, now well exceeding 100 lum/W in commercial products, has still the margin to double, promising a strong reduction in electricity consumption.
White LEDs are commonly based on a blue LED, combined with luminescent materials, or phosphors, which convert part of the blue light to longer wavelengths, the mixture providing white light. Besides the workhorse Y3Al5O12:Ce (YAG:Ce, yielding yellow emission), europium doped phosphors are used to provide e.g. the red emission required for warm-white LEDs.
Six main requirements for LED phosphors are discussed and used to explain the discrepancy between the high number of compositions described in literature and the handful of actually used compounds, being almost uniquely based on rare earth ions as luminescent center [1]. Alternative materials avoiding the use of rare earth ions are discussed, including Mn4+ doped fluorides phosphors (e.g. K2SiF6:Mn4+ [2]) and quantum dots. Finally, the impact of phosphor geometries on phosphor use, including remote phosphor applications, are discussed.
[1] Smet PF and Joos JJ, Nat. Mater. 16 (2017) 500.
[2] Sijbom H et al, Opt. Mater. Exp. 7 (2017) 3332.
Photocatalytic degradation of some organic dyes under solar light irradiation...Iranian Chemical Society
Nanoparticles of the ZnO and TiO2 were synthesized and the physicochemical properties of the compounds were characterized by IR, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns of the ZnO and TiO2 nanoparticles could be indexed to hexagonal and rutile phase, respectively. Aggregated nanoparticles of ZnO and TiO2 with spherical-like shapes were observed with particle diameter in the range of 80-100 nm. These nanoparticles were used for photocatalytic degradation of various dyes, Rhodamine B (RhB), Methylene blue (MB) and Acridine orange (AO) under solar light irradiation at room temperature. Effect of the amount of catalyst on the rate of photodegradation was investigated. In general, because ZnO is unstable, due to incongruous dissolution to yield Zn(OH)2 on the ZnO particle surfaces and thus leading to catalyst inactivation,the catalytic activity of the system for photodegradation of dyes decreased dramatically when TiO2 was replaced by ZnO.
Sonia Katdare Research Presentation 2008soniakatdare
Sonia Katdare conducted research on the synthesis and characterization of gold nanoparticles. She used a bottom-up foam-based chemical synthesis method to produce gold nanoparticles by reducing gold ions trapped at the interface between gas bubbles and liquid in an aqueous foam. Characterization using UV-vis spectroscopy, XRD, and TEM showed that mono-dispersed spherical gold nanoparticles around 19nm in size were produced using this method. The foam-based synthesis provides control over nanoparticle size and morphology based on reaction conditions like gas pressure and drainage rate.
This document summarizes cerium oxide (CeO2) nanoparticles, including their structure, synthesis methods, and applications. CeO2 nanoparticles have a fluorite crystalline structure and adopt different shapes depending on their size. They can be synthesized via various methods like precipitation and have uses in diesel engines and medical treatments. Specifically, adding CeO2 nanoparticles to diesel fuel improves engine performance and reduces emissions by promoting more complete combustion. The nanoparticles also have potential applications in treating neurological diseases involving oxidative stress, like Parkinson's, due to their antioxidant properties.
Defects in energy storage phosphors: friends or enemies? (PRE19 workshop)Philippe Smet
Plenary talk presented at the PRE19 workshop (Photoluminescence in Rare Earths: Photonic Materials and Devices) in Nice, France, on September 4. Dealing with persistent luminescence, afterglow, mechanoluminescence, traps, defects and thermoluminescence. Overview of the activities of the LumiLab research in the past 10 years.
The document provides guidance on creating effective resumes and cover letters. It discusses researching the job description, knowing your skills and qualifications, and highlighting accomplishments. Resume sections should include contact information, skills, education, experience, and optionally interests. Accomplishment statements in the experience section should use action verbs and quantify results. Cover letters are meant to express interest in the company and position and summarize relevant strengths. Overall, the document offers tips for crafting resumes and cover letters that clearly communicate a candidate's qualifications for a given job.
The document provides guidance on developing accomplishment statements for a job search resume and interview preparation. It recommends having 20 or more accomplishment statements in an inventory. Each statement should include a benefit to the employer stated quantitatively, and the action taken to achieve that benefit. Examples of accomplishment statements are provided covering a wide range of benefits such as increased sales or profits, reduced costs or errors, and improved quality, customer satisfaction or processes.
Harvesting Hot Holes in Plasmon-Coupled Ultrathin Photoanodes for High-Perfor...Pawan Kumar
The harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO2 and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO2 (a-TiO2). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO2 (Au@a-TiO2) generated 2.5 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm–2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO2 photoelectrodes produced a small positive photocurrent of 0.1 mA cm–2 even at a bias of −0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO2 and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al2O3 (Au@Al2O3) generated 0.02 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO2 in the extraction of holes in Au@a-TiO2 photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...Pawan Kumar
Bulk g-C3N4 is an earth-abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P-doping and size quantization are combined to synthesize highly fluorescent P-doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase-phase and rutile-phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight-driven water-splitting and as photocatalysts for surface catalytic reactions. Square-shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD-STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD-STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light-driven transformation of 4-nitrobenzenethiol (4-NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.
The document provides an overview of X-ray Photoelectron Spectroscopy (XPS) as a surface analysis technique. It describes how XPS works based on the photoelectric effect, and how it can be used to identify elements, chemical states, and compounds present on material surfaces. The key components of an XPS instrument are also outlined.
1. TiO2 is an effective photocatalyst for water splitting under UV light through generating electron-hole pairs, but has a large bandgap only absorbing UV light.
2. Nitrogen doping of TiO2 has been explored as a way to narrow the bandgap and enable absorption of visible light, but the exact chemical nature of incorporated nitrogen is unclear from characterization techniques.
3. Preparation methods can result in substitutional or interstitial nitrogen in the TiO2 lattice, but there is no clear correlation between method used and nitrogen state incorporated.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Co...Pawan Kumar
We present a potential solution to the problem of extraction of photogenerated holes from CdS nanocrystals and nanowires. The nanosheet form of C3N5 is a low-band-gap (Eg = 2.03 eV), azo-linked graphenic carbon nitride framework formed by the polymerization of melem hydrazine (MHP). C3N5 nanosheets were either wrapped around CdS nanorods (NRs) following the synthesis of pristine chalcogenide or intercalated among them by an in situ synthesis protocol to form two kinds of heterostructures, CdS-MHP and CdS-MHPINS, respectively. CdS-MHP improved the photocatalytic degradation rate of 4-nitrophenol by nearly an order of magnitude in comparison to bare CdS NRs. CdS-MHP also enhanced the sunlight-driven photocatalytic activity of bare CdS NWs for the decolorization of rhodamine B (RhB) by a remarkable 300% through the improved extraction and utilization of photogenerated holes due to surface passivation. More interestingly, CdS-MHP provided reaction pathway control over RhB degradation. In the absence of scavengers, CdS-MHP degraded RhB through the N-deethylation pathway. When either hole scavenger or electron scavenger was added to the RhB solution, the photocatalytic activity of CdS-MHP remained mostly unchanged, while the degradation mechanism shifted to the chromophore cleavage (cycloreversion) pathway. We investigated the optoelectronic properties of CdS-C3N5 heterojunctions using density functional theory (DFT) simulations, finite difference time domain (FDTD) simulations, time-resolved terahertz spectroscopy (TRTS), and photoconductivity measurements. TRTS indicated high carrier mobilities >450 cm2 V–1 s–1 and carrier relaxation times >60 ps for CdS-MHP, while CdS-MHPINS exhibited much lower mobilities <150 cm2 V–1 s–1 and short carrier relaxation times <20 ps. Hysteresis in the photoconductive J–V characteristics of CdS NWs disappeared in CdS-MHP, confirming surface passivation. Dispersion-corrected DFT simulations indicated a delocalized HOMO and a LUMO localized on C3N5 in CdS-MHP. C3N5, with its extended π-conjugation and low band gap, can function as a shuttle to extract carriers and excitons in nanostructured heterojunctions, and enhance performance in optoelectronic devices. Our results demonstrate how carrier dynamics in core–shell heterostructures can be manipulated to achieve control over the reaction mechanism in photocatalysis.
Growth and Characterization of Barium doped Potassium Hydrogen Phthalate Sing...IJERA Editor
The Non Linear Optical materials have acquired new significance with the advent of a large number of devices
utilizing solid state Laser sources. Potassium Hydrogen Phthalate one of the Non Linear Optical material having
superior non linear optical properties has been exploited for variety of application. In the present work, KHP
single crystals were grown by slow evaporation technique with Barium metal ion as a dopant. The grown
crystals were subjected to powder XRD analysis and the result shows that the Ba2+ ions does not alter the crystal
structure, but it enter into the crystal lattice of pure KHP. The optical transparency of the grown crystal was
studied by UV-Visible spectroscopy, the molecular structure was confirmed by FTIR analysis and its thermal
stability by TG/DTA analysis. The improved SHG efficiency of barium doped Potassium Hydrogen Phthalate
crystal could enhance the nonlinearity behaviour. In addition to this, the electrical parameter such as dielectric
constant was studied in detail.
This document discusses a study that used Laser-Induced Breakdown Spectroscopy (LIBS) to identify atomic and molecular emissions from potassium-based energetic materials. Samples of these materials were prepared as bulk pellets and thin films deposited on substrates. LIBS was used to obtain spectra from the samples in the ultraviolet-visible and infrared regions. Spectral lines were identified and matched to known atomic and molecular signatures to allow identification of the energetic materials.
TechBoost 2015 - Ghent University - Phosphors for lightingPhilippe Smet
Presentation on the history of lighting and the role of phosphors (luminescent materials) in lighting. From fluorescence lamps to white light emitting diodes (LEDs) for displays and general lighting.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...Pawan Kumar
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
The document summarizes the synthesis and characterization of TiO2 and nitrogen-doped TiO2 nanostructures for application in dye-sensitized solar cells. Key points include:
1) TiO2 nanotube powders and arrays were synthesized using an electrochemical anodization technique and characterized using various methods.
2) Nitrogen doping was used to modify the bandgap of TiO2.
3) The synthesized materials were used to fabricate dye-sensitized solar cells and their performance was tested for potential application in solar energy conversion.
The document discusses recycling phosphorescent powder from cathode ray tubes (CRTs) and fluorescent tubes. It aims to determine optimal leaching conditions to maximize recovery of precious lanthanide metals. Experimental techniques used include X-ray powder diffraction (XRD) to analyze sample composition, ICP-OES for elemental analysis, and scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) analysis. Experiments involved leaching CRT and fluorescent tube powders using various acids like nitric acid, aqua regia, and citric acid to identify conditions giving highest lanthanide recovery.
EMRS 2018 Replacing rare earth ions in LEDs (?)Philippe Smet
Two decades after the development of the blue light-emitting diode (LED), LEDs have quickly established themselves as the lighting technology of the future. The high efficiency, spectral tunability, lack of toxic compounds and a small footprint makes them far more attractive than other lighting technologies. The high efficiency, now well exceeding 100 lum/W in commercial products, has still the margin to double, promising a strong reduction in electricity consumption.
White LEDs are commonly based on a blue LED, combined with luminescent materials, or phosphors, which convert part of the blue light to longer wavelengths, the mixture providing white light. Besides the workhorse Y3Al5O12:Ce (YAG:Ce, yielding yellow emission), europium doped phosphors are used to provide e.g. the red emission required for warm-white LEDs.
Six main requirements for LED phosphors are discussed and used to explain the discrepancy between the high number of compositions described in literature and the handful of actually used compounds, being almost uniquely based on rare earth ions as luminescent center [1]. Alternative materials avoiding the use of rare earth ions are discussed, including Mn4+ doped fluorides phosphors (e.g. K2SiF6:Mn4+ [2]) and quantum dots. Finally, the impact of phosphor geometries on phosphor use, including remote phosphor applications, are discussed.
[1] Smet PF and Joos JJ, Nat. Mater. 16 (2017) 500.
[2] Sijbom H et al, Opt. Mater. Exp. 7 (2017) 3332.
Photocatalytic degradation of some organic dyes under solar light irradiation...Iranian Chemical Society
Nanoparticles of the ZnO and TiO2 were synthesized and the physicochemical properties of the compounds were characterized by IR, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD patterns of the ZnO and TiO2 nanoparticles could be indexed to hexagonal and rutile phase, respectively. Aggregated nanoparticles of ZnO and TiO2 with spherical-like shapes were observed with particle diameter in the range of 80-100 nm. These nanoparticles were used for photocatalytic degradation of various dyes, Rhodamine B (RhB), Methylene blue (MB) and Acridine orange (AO) under solar light irradiation at room temperature. Effect of the amount of catalyst on the rate of photodegradation was investigated. In general, because ZnO is unstable, due to incongruous dissolution to yield Zn(OH)2 on the ZnO particle surfaces and thus leading to catalyst inactivation,the catalytic activity of the system for photodegradation of dyes decreased dramatically when TiO2 was replaced by ZnO.
Sonia Katdare Research Presentation 2008soniakatdare
Sonia Katdare conducted research on the synthesis and characterization of gold nanoparticles. She used a bottom-up foam-based chemical synthesis method to produce gold nanoparticles by reducing gold ions trapped at the interface between gas bubbles and liquid in an aqueous foam. Characterization using UV-vis spectroscopy, XRD, and TEM showed that mono-dispersed spherical gold nanoparticles around 19nm in size were produced using this method. The foam-based synthesis provides control over nanoparticle size and morphology based on reaction conditions like gas pressure and drainage rate.
This document summarizes cerium oxide (CeO2) nanoparticles, including their structure, synthesis methods, and applications. CeO2 nanoparticles have a fluorite crystalline structure and adopt different shapes depending on their size. They can be synthesized via various methods like precipitation and have uses in diesel engines and medical treatments. Specifically, adding CeO2 nanoparticles to diesel fuel improves engine performance and reduces emissions by promoting more complete combustion. The nanoparticles also have potential applications in treating neurological diseases involving oxidative stress, like Parkinson's, due to their antioxidant properties.
Defects in energy storage phosphors: friends or enemies? (PRE19 workshop)Philippe Smet
Plenary talk presented at the PRE19 workshop (Photoluminescence in Rare Earths: Photonic Materials and Devices) in Nice, France, on September 4. Dealing with persistent luminescence, afterglow, mechanoluminescence, traps, defects and thermoluminescence. Overview of the activities of the LumiLab research in the past 10 years.
The document provides guidance on creating effective resumes and cover letters. It discusses researching the job description, knowing your skills and qualifications, and highlighting accomplishments. Resume sections should include contact information, skills, education, experience, and optionally interests. Accomplishment statements in the experience section should use action verbs and quantify results. Cover letters are meant to express interest in the company and position and summarize relevant strengths. Overall, the document offers tips for crafting resumes and cover letters that clearly communicate a candidate's qualifications for a given job.
The document provides guidance on developing accomplishment statements for a job search resume and interview preparation. It recommends having 20 or more accomplishment statements in an inventory. Each statement should include a benefit to the employer stated quantitatively, and the action taken to achieve that benefit. Examples of accomplishment statements are provided covering a wide range of benefits such as increased sales or profits, reduced costs or errors, and improved quality, customer satisfaction or processes.
11 Stats You Didn’t Know About Employee RecognitionOfficevibe
Recognizing employees is one of the most overlooked facets of managements that even great leaders sometimes forget about. Without a good employee recognition strategy, people will feel unappreciated and build up stress.
In fact, the number 1 reason why most Americans leave their jobs is that they don’t feel appreciated . The last thing you want is to have high employee turnover because of poor employee recognition.
Officevibe put together some incredible statistics about employee recognition.
Read more on Officevibe blog:
https://www.officevibe.com/blog/employee-recognition-infographic
Learn more about Officevibe, the simplest tool for a greater workplace:
https://www.officevibe.com/
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The document provides 10 timeless productivity hacks that will make you more productive. Some of the key hacks include: defining your most important tasks each day; focusing on one task at a time instead of multitasking; creating a morning routine; limiting distractions like social media; prioritizing important work; batching similar tasks; eliminating unnecessary tasks; and doing the task you are most likely to procrastinate first. Following these simple habits can improve overall productivity without needing a complex system.
We held the largest ever Virtual SlideShare Summit a week back, if you missed it here's your chance to hear from the experts once more on some of the takeaways on presentation design and SlideShare Marketing
Leader's Guide to Motivate People at WorkWeekdone.com
To motivate employees, leaders should provide more praise, attention, responsibility, and incentives. Specifically, leaders should recognize employees' good work, keep employees informed about company goals and strategies, assign more challenging tasks with autonomy, establish incentive programs with realistic yet challenging goals, and provide pay raises correlated with employee performance and development. Leaders can use a performance management tool like Weekdone to understand employee status, provide transparent feedback, and align goals across different levels.
1) Laser operation was achieved in a neodymium-doped scandium silicate (Nd:SSO) crystal based on the 4F3/2→4I9/2 transition of Nd3+ ions. Pumped by an 808 nm laser diode, laser emission at 914 nm was obtained with an output power of 581 mW.
2) Spectroscopic measurements of the Nd:SSO crystal found absorption and emission cross sections of 1.69×10-20 cm2 and 1.13×10-20 cm2 respectively at relevant wavelengths. The gain cross section was estimated to allow lasing inversion at β=0.25.
3) Compared to other
Introduction to nanoscience and nanotechnologyaimanmukhtar1
Introduction of nanoscience/nanotechnology ,properties/potential applications of nanomaterials and electrodeposition of metal single component and alloy nanowires in AAO template
This presentation is about phtoocatalytic process and nanomaterials as photocatalyst. This is useful in the treatment of wastewater and environmental remediation applications.
Analysis Of Carbon Nanotubes And Quantum Dots In A Photovoltaic Device Slide ...M. Faisal Halim
Francis' presentation to Louis Stokes Association for Minority Participation. Since I co-authored this work I think I have the right to a copy. I was the graduate student Francis was working with.
Synthesis, characterization and electrocatalytic activity of silver nanorods ...tshankar20134
This document describes the synthesis of silver nanorods using a polyol process. Silver nitrate and polyvinylpyrrolidone (PVP) are reduced by propylene glycol at high temperature, allowing control over the diameter and length of the nanorods. Characterization with SEM, TEM, XRD and UV-vis spectroscopy confirms the formation of crystalline silver nanorods. Electrochemical testing shows that a glassy carbon electrode coated with silver nanorods exhibits high catalytic activity for the reduction of benzyl chloride, with a more positive reduction potential than bulk silver or plain glassy carbon electrodes. The extraordinary catalytic effect of the silver nanorods is likely due to their morphology and high affinity for chloride ions.
This document describes a passively Q-switched Nd:YAG ceramic laser using a single wall carbon nanotube saturable absorber. The laser generated pulses with a maximum duration of 1.2 ms, repetition rate varying from 14 to 95 kHz, and maximum pulse energy of 4.5 mJ at a repetition rate of 31.8 kHz. The laser achieved a maximum output power of 376 mW and optical-to-optical conversion efficiency of 4.3% at a pump power of 8.68 W. Characterization of the Nd:YAG ceramic gain medium showed scattering and absorption losses similar to a crystal, with the ceramic laser demonstrating output power only 6.3% lower than an equivalent
IRJET - Photoluminescence Study of Rare Earth Doped ZnO NanoparticlesIRJET Journal
This document reports on a study of photoluminescence properties of rare earth doped ZnO nanoparticles. ZnO nanoparticles were synthesized using a chemical method with thiourea as a capping agent. X-ray diffraction and scanning electron microscopy were used to characterize the structural and morphological properties. The particle sizes measured from XRD were 56nm for doped samples and 66nm for undoped. SEM images showed agglomerated nanoparticles without distinct structures. Absorption spectra showed band gaps of 4.32eV for undoped and 4.28eV for doped samples. Photoluminescence excitation and emission spectra of doped samples exhibited characteristic peaks of Eu3+ ions.
Electrochemical Synthesis of MoO3 Nanoparticles Effect of Temperature Convert...IJERA Editor
MoO3 nanorods were prepared by electrochemical reduction method using the tetra propyl ammonium bromide (TPAB) was structure directing agent in an organic medium viz. tetra hydro furan (THF) and acetonitrile (ACN) in 4:1 ratio and at current density 14mA &18 mA. The reduction process takes place under atmospheric condition over a period of 2 h. Dried sample was calcinated in muffle furnace at 500ºC. The parameters such as current density and concentration of stabilizers were used to control the size of nanorods. The synthesized MoO3 nanorods were characterized by using UV-Visible, FT-IR, XRD, SEM-EDS and TEM analysis techniques.
This document discusses the nonlinear optical properties of copper nanoparticles prepared by pulse laser ablation in different solutions. Copper nanoparticles were synthesized in distilled water, deionized water, and a mixture of ethylene glycol and deionized water using a nanosecond pulsed Nd:YAG laser. Characterization using UV-visible spectroscopy and SEM showed the nanoparticles had surface plasmon resonance peaks between 590-676 nm and diameters ranging from 13.16-21.25 nm depending on the solution. Z-scan measurements determined the nonlinear refractive index and nonlinear absorption coefficient of the copper nanoparticle suspensions.
Metal ion burst: Examining metal ion diffusion using ultrafast fluorescence s...Chelsey Crosse
Presentation to accompany my report for my oral examination. Details background of fluorescence upconversion techniques, development of measurement systems for release of a metal cation and minimization of diffusion distribution in solutions.
Study of highly broadening Photonic band gaps extension in one-dimensional Me...IOSR Journals
This document discusses the theoretical study of enhancing the reflectance spectra of one-dimensional metallo-organic multilayer photonic structures. It examines structures composed of alternating thin layers of silver and the organic material N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine. The transfer matrix method is used to calculate the reflectance spectra for different configurations of layer thicknesses and incident angles of light. Tuning of the photonic band gap is observed by varying the thickness of either the metal or organic layers. Broadening and shifting of the band edges from ultraviolet to visible and infrared regions occurs due to the optical absorption properties of both the
Dr. Charles Lee presents an overview of his program, Organic Materials Chemistry, at the AFOSR 2013 Spring Review. At this review, Program Officers from AFOSR Technical Divisions will present briefings that highlight basic research programs beneficial to the Air Force.
Synthesis, Characterization of ZnS nanoparticles by Coprecipitation method us...IOSR Journals
ZnS nanoparticles are prepared by coprecipitation method using various capping agents like PVP (polyvinylpyrrolidone), PVA (polyvinylalcohol) and PEG-4000 (polyethyleneglycol). These are characterized by UV-Visible spectra, X-ray diffraction (XRD) studies, Fourier Transform Infra-red spectra (FTIR) and Transmission electron microscopy (TEM). UV-Visible absorption spectra are used to find the optical band gap and the values obtained have been found to be in the range of 3.80-4.00eV. The particle size of nanoparticles calculated from XRD pattern has been in the range of 2-4 nm. It is also observed that the particle size of nanoparticle is affected by the nature of capping agent. Photo catalytic degradation of xylenol orange (XO) by the nanoparticles shows that these act as photo catalysts under sunlight irradiation. The XO dye was degraded more than 87.24, 83.42 and 73.05% in the presence of PEG-4000, PVA and PVP capped ZnS nanoparticles in 120, 150 and 180 min. respectively. The kinetics of catalyzed by synthesized ZnS nanoparticles with XO dye follows pseudo-first order kinetics with reasonable apparent rate constants.
Preparation, Structure, and Characterization of Nd2mo2o9 fast Oxide Ion Condu...IJARIIT
The structure and ion conductivity of Nd2Mo2O9powders were synthesized by using Nd(NO2)3, MoO3, and aspartic acid (fuel) in assisted combustion method with heating at 550˚C for 6 hours. The thermal decomposition, phase identification, morphology, ionic conductivity of the samples were studied by TGA/DTA, XRD and SEM four probe D.C. method respectively. The formation of Nd2Mo2O9 was confirmed by FTIR studies. The synthesis and crystallization were followed by thermochemical techniques (TGA/DTA) studies. The synthesized materials showed reasonable ionic conductivity. These results indicate that assisted combustion method is a promising method to prepare nanocrystalline Nd2Mo2O9 for solid oxide fuel cell.
Study of Microstructural, Electrical and Dielectric Properties of La0.9Pb0.1M...Scientific Review SR
The present work studies the microstructural and electrical properties of La0.9Pb0.1MnO3 and La0.8Y0.1Pb0.1MnO3 ceramics synthesized by solid-state route method. Microstructure and elemental analysis of both samples were carried out by field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) method, respectively. Phase analysis by X-ray diffraction (XRD) indicated formation of single phase distorted structure. The XRD data were further analyzed by Rietveld refinement technique. Raman analysis reveals that Y atom substitutes La site into the LPMO with shifting of phonon modes. The temperature variation of resistivity of undoped and Y-doped La0.9Pb0.1MnO3 samples have been investigated. The electrical resistivity as a function of temperature showed that all samples undergo an metal-insulator (M-I) transition having a peak at transition temperature TMI. Y-doping increases the resistivity and the metal-insulator transition temperature (TMI) shifts to lower temperature. The temperature-dependent resistivity for temperatures less than metal-insulator transition is explained in terms the quadratic temperature dependence and for T > TMI, thermally activated conduction (TAC) is appropriate. Variation of frequency dispersion in permittivity and loss pattern due to La-site substitution in LPMO was observed in the dielectric response curve.
ITO (indium tin Oxide) & FTO (fluorine doped tin oxide )Preeti Choudhary
Indium tin oxide (ITO) is a transparent conducting oxide used in applications such as touchscreens and solar cells. It is deposited as a thin film using methods like thermal evaporation or sputtering. ITO has high electrical conductivity and optical transparency due to its large band gap. It is studied using techniques like Kelvin probe force microscopy that measure electrical properties at the nanoscale. While ITO enables important technologies, its production requires significant energy and indium is a scarce resource.
A Simple Thermal Treatment Synthesis and Characterization of Ni-Zn Ferrite (N...IOSR Journals
Cubic structured nickel-zinc ferrite nanoparticles (Ni0.5Zn0.5Fe2O4) have been synthesized by thermal treatment method. This simple procedure employed an aqueous solution containing only metal nitrates as precursors, polyvinyl pyrrolidone as a capping agent, and deionized water as a solvent. The solution was thoroughly stirred for 2 hour, dried at 353 K for 3 hour, the dried material crushed into powder and calcined the powder at 873 K to remove organic substances and crystallize the particles. The microstructure properties of the prepared ferrite nanoparticles were measured using FTIR, XRD, TEM, and EDX and the magnetic properties were determined using VSM and EPR. The average particle size increased from 7 to 22 nm with the increase of calcination temperature from 723 to 873 K. The saturation magnetization, coercivity field, and g-factor increased respectively from 24 emu/g, 11 G, and 2.0673at 723 K to 38 emu/g, 60 G, and 2.1227 at 873 K. This method offers simplicity, a low cost, and an environmentally friendly operation since it produces no by-product effluents.
A Simple Thermal Treatment Synthesis and Characterization of Ni-Zn Ferrite (N...
Rahman-INFN-LNL
1. Irradiation effects in high melting oxides and
synthesis of new luminescent composite materials
Abu Zayed M. Saliqur Rahman, Dr. Sc.
Department of Mechanical Engineering
University of Malaya
Kuala Lumpur, Malaysia
Seminar at Laboratori Nazionali di Legnaro
Time and Date: 11.00 -12:00
28 June, 2016
Place: Rostagni meeting room
2. Outline of the talk
• Self-introduction
• Introduction
• Purpose of the study
• Experimental
• Results and discussion
• Conclusions
• Research accomplishment
11. Outline of the talk
• Self-introduction
• Introduction
• Purpose of the study
• Experimental
• Results and discussion
• Conclusions
• Research accomplishment
12. Introduction
• Irradiation effects in solids have been studied for quiet a long
period of time as it can modify optical, magnetic and structural
properties of the solid materials.
• Many works are still yet to be done within the field of irradiation
effects in solids compare to other fields in solid state due to
limitation of the experimental and irradiation facilities.
• In recent days, many new composite materials have been
discovered. Irradiation effects in these new composite materials
are unknown which also triggered much more investigation in
this interesting field of research.
13. Importance of irradiation effects in solids:
1) To know the behavior of candidate materials in
irradiating environment such as nuclear reactor, high
energy physics establishment, other irradiation
facilities
2) Irradiation-induced synthesis or fabrication of
nanomaterial or colloids
3) Application in aerospace technology
4) Radiation detection and measurement technology
(Scintillators)
14. • Irradiation effects in alkali halides and metals are
well understood comparing to oxides.
Reason:
Complex nature of oxide crystal structure
and lack of high purity crystal.
• In this study, irradiation effects in two oxides namely
α-Al2O3 and MgAl2O4 are investigated by using
various experimental methods.
• Another important part of this research is to synthesis
of new luminescent composite materials for various
application including radiation detector, outdoor
devices etc.
15. Outline of the report
• Acknowledgement
• Introduction
• Purpose of the study
• Experimental
• Results and discussion
• Conclusions
• Research accomplishment
16. Purpose of the study
• To investigate the anion vacancies in neutron- and electron-irradiated
MgO.nAl2O3 single crystals by using photoluminescence techniques.
• To investigate the cation vacancies in fast neutron-irradiated MgO.nAl2O3
single crystals by positron annihilation techniques.
• To investigate irradiation-induced formation of aggregate defects in neutron-
irradiated α-Al2O3 by using near-infrared (NIR) photoluminescence,
scanning electron microscopy (SEM) and optical microscopy(OM).
• To synthesize Sm-doped phosphors using pure Na2SO4 and investigate
irradiation-induced conversion of Sm3+ ions into Sm2+ within Na2SO4.
• To synthesize Sm-doped SiO2-Na2SO4 and LDPE-Na2SO4 luminescent
composite and investigate luminescence properties of these composites.
17. Outline of the report
• Acknowledgement
• Introduction
• Purpose of the study
• Experimental
• Results and discussion
• Conclusions
• Research accomplishment
18. Experimental
• Samples
single crystals of α-Al2O3 and MgAl2O4
• Origin
1) Kyoto ceramics (Japan)
2) Crystal Tech (German)
3) Furuuchi Chemical Co. Japan
• Production method
1) Edge-Defined Film-Fed Growth
2) Czochralski Method
19. Synthesis of samples:
• Sm-doped Na2SO4
(Melt-mixing at 950˚ C for 30 mins)
• Sm-doped SiO2-Na2SO4 composite
(Melt-mixing at 1050˚ C for 30 mins)
• Sm-doped LDPE-Na2SO4 composite
Two step synthesis:
1st step synthesis of Na2SO4:Sm phosphor by melt-
mixing at 940˚ C for 20 mins.
2nd step melt-mixing at 150˚ C followed by hot press.
20. Synthesis of phosphor samples at 1050˚C
Samples in crucible after synthesis
Red luminescence from phosphors under
365 nm UV light excitation
No luminescence from host matrix under
UV light
21. • Irradiation (Place)
1) Kyoto University Reactor Research Institute
Linear Accelerator (LINAC), Low temperature loop (LTL) ,
Hydro exposure tube (HET), Gamma ray irradiation facility
2) Japan material testing reactor (JMTR), JAEA
3) Institute of High Energy Physics (IHEP)
4) China Institute of Atomic Energy (CIAE)
• Irradiation (type)
1) Neutron
2) Electron
3) Gamma
29. Emission Spectra
Light Source
Sample
Excite with some
selected
wavelength
Reception of light signal by PMT in computer
Detecting wide
rang of visible
light from the
sample
Wavelength (nm)
P
L
I
N
T.
30.
31. Outline of the report
• Acknowledgement
• Introduction
• Purpose of the study
• Experimental
• Results and discussion
• Conclusions
• Research accomplishment
33. MgAl2O4 (VUV-UV spectroscopy)
Fig.1 VUV-UV photoexcitation (left) and photoluminescence
(right) spectra of irradiated and unirradiated MgO.nAl2O3 (n =
2). Electron- (a), neutron-irradiated (b) and unirradiated (c)
samples. Observation wavelength: 476 nm. Excitation
wavelength: 219 nm.
Fig. 2 Photoexcitation spectra of neutron-irradiated and unirradiated
spinel samples at room temperature. Observation wavelength: 476 nm.
Fig. 3 Vibronic photoexcitation (left) and emission spectra of electron-
(a), neutron-irradiated (b) and (c) unirradiated spinel samples at 13 K.
Observation wavelength : 380 nm. Excitation wavelength: 240 nm.
Fig. 4 Vibronic photoexcitation spectra of neutron-irradiated spinel at
13 K, monitored at (a) 380 (b) 400 (c) 430 and (d) 465 nm.
34. Fig. 5 Vibronic photoexcitation spectra of neutron-irradiated
sample at temperatures 13 to 120 K. Observation wavelength:
380 nm.
Band
(Excitation)
Line
no.
Wavelength
(nm)
Wavenumber
(cm-1)
Energy
separation
(cm-1)
Huang-
Rhys
factor
Debye
Temp.
(K)
230 nm
0
1
2
3
271.3
264.8
260.5
254.0
36,860
37,764
38,388
39,370
0
904
624
982
2.78 518
Table 1: Sharp lines associated with 230 nm photoexcitation band, estimated Huang–Rhys factor
and Debye temperature.
35. Fig. 6 Estimation of Debye temperature and Huang
Rhys factor S from temperature dependence of the
230 nm vibronic photoexcitation band by curve
fitting method.
Fig. 7 Schematic diagram of F-center transition in
irradiated MgO.nAl2O3 (n= 2)
Is/Ib=exp[-S{1+2π2/3×(T/ΘD)2}]
36. MgAl2O4 (Positron annihilation spectroscopy)
Fig. 8 Positron lifetimes and intensities of long lifetimes in
fast neutron-irradiated MgO .nAl2O3(n = 2)
Fig. 9 CDB ratio curves of fast neutron-irradiated and unirradiated
spinel to pure Al. Peak was found approximately at 11×10-3 m0c.
Fig. 10 Schematic diagram of positron trapped in vacancy
and vacancy-oxygen complex in spinel crystal structure.
38. Fig. 11 AFM (a,b) and SPM (c,d) 3-D images of
surface for unirradiated (a,c) and neutron-
irradiated (b,d) spinel single crystal. Scaling of
AFM and SPM images are 5×5 and 4 ×4 µm
respectively
Fig. 12 NIR photoluminescence spectra of
neutron-irradiated (JMTR) spinel single crystal
at temperatures ranging from 13.6 to 300 K.
The excitation wavelength was 532 nm.
39. Fig. 14 Temperature dependence of
photoluminescence intensity of the 1,685
nm band obtained from Fig. 3.
Experimental data points were fitted with
curves using Eqn. 1 and 2.
Fig. 13 NIR photoluminescence spectra of
neutron-irradiated (JMTR) spinel single
crystal at temperatures ranging from 13.6
to 300 K. The excitation wavelength was
532 nm
40. ɑ-Alumina (SEM & OM)
Fig. 15 Optical micrographs of unirradiated (a) and fast
neutron-irradiated (b-f) α-Al2O3 samples. Fast Neutron
fluence was 2.8 × 1018 n/cm2.
Fig. 16 SEM images of unirradiated (a) and fast neutron-
irradiated (b-c) α-Al2O3 samples to fluence of 2.8 × 1018
n/cm2 after annealing at 1100˚C.
41. Alumina (NIR PL and UV-Vis)
Fig. 17 NIR PL spectra of (a) unirradiated, fast neutron-
irradiated with fluence of (b) 1.3 ×1017 (c) 2.8 ×1018 (d) 9.8
×1018 (e) 1.2 × 1020 and (f) annealed α-Al2O3 samples.
Excitation source was fixed at 532 nm.
Fig. 18 NIR PL spectra of fast neutron-irradiated α-Al2O3
samples with Gaussian curve fitting. Fast Neutron fluence
was 2.8 × 1018 n/cm2.
42. Fig. 19 NIR PL spectra of neutron-irradiated α-Al2O3 at temperatures
ranging from 13.6 to 300 K. Excitation wavelength was 532 nm.
Fig. 21 Temperature dependence of PL peak energy (a), PL intensity and
FWHM (b) near 1,170 nm emission band in neutron-irradiated α-Al2O3.
Fig. 20 Optical absorption spectra of unirradiated and neutron-
irradiated α-Al2O3 at room temperature.
43. Na2SO4:Sm (SEM & XRD)
Fig. 22 3D crystal structure of Na2SO4.
Fig. 23 SEM image of the Na2SO4:SmF3 phosphor.
Fig. 24 XRD patterns of (a) undoped Na2SO4, (b) Na2SO4:SmF3
and (c) electron-irradiated Na2SO4:SmF3 at room temperature.
Particle size calculation d = 0.9λ/β cos θ
44. Fig. 25 PL spectra of (a) as-synthesized, (b-d) γ-ray-
irradiated (e) electron-irradiated Na2SO4:SmF3 at room
temperature, obtained under 375 nm excitation.
Fig. 26 PL spectra of (a) electron-irradiated, (b-f) γ-ray-
irradiated and (e) as-synthesized Na2SO4:SmF3 at room
temperature, obtained under 570 nm excitation.
45. Fig. 27 PE (left) and PL (right) spectra of -ray (44 kGy)
irradiated Na2SO4:SmF3 at 10 K. PE spectrum was obtained
by monitoring the luminescence at 728.4 nm, and PL
spectrum was obtained under 590 nm excitation.
Fig. 28 Schematic energy levels of (a) Sm2+ and (b) Sm3+
(4f5) in the Na2SO4 lattice. Arrows show the excitation and
emission transitions.
46. Fig. 29 Relative PL intensities of Sm2+ (●) and Sm3+ (o) of γ-ray-
irradiated Na2SO4:SmF3 at room temperature as a function of γ-ray
exposure. PL intensities of Sm2+ band and Sm3+ line at 598 nm were
plotted. Straight line (red) represents the linear t and curved line
(blue) was drawn as guide for an eye.
Fig. 30 PL spectra of electron-irradiated Na2SO4:SmF3 at room
temperature after annealing at various temperatures. These were
obtained under 570 nm excitation.
47. Sm-doped SiO2-Na2SO4 composite
(XRD & SEM)
Fig. 31 XRD spectra of (a) SiO2 (b)SiO2-20%Na2SO4:Sm and (c) Na2SO4.
Fig. 32 SEM images of (a) & (b) SiO2-20%Na2SO4:Sm
composite with scale bar of 50 and 2 μm, respectively. inset
(a): synthesized composite shows red emission under UV
light. SEM images of (c)& (d) SiO2, inset (c) : no emission
from host under UV light.
48. Fig 33 (a) PE (left) and PL spectra (right) of Na2SO4:Sm. (b) PE (left)
and PL (right) spectra of SiO2-20%Na2SO4:Sm. Excitation and
emission spectra (red line) for SiO2 was given for comparison.
Observation wavelength: 644 nm. Excitation wavelength: 375 nm.
Fig. 35 (a) PL spectra of SiO2-x%Na2SO4:Sm (x=0,5,10,20) under
excitation at 402 nm. (b) Schematic energy levels of Sm3+ (4f5) in
composite materials. Arrows show the excitation and emission
transitions.
Fig. 34 (a) PL spectra of 644 nm band
under 402 nm excitation for SiO2
and SiO2-x%Na2SO4:Sm (x=5,10,20).
(b) Relative PL intensities of the 644
nm band.
49. LDPE-Na2SO4:Sm composite (XRD, SEM & EDX)
Fig. 36 Photograph of synthesized Sm-doped LDPE-Na2SO4
composite, pure and commercial LDPE. .
Fig. 37 XRD patterns of LDPE- xwt%Na2SO4:Sm composites
(x =0, 5, 10, and 20) and pure Na2SO4:Sm.
Fig. 38 SEM images of a: Na2SO4:Sm3+ phosphor powders b: the pure
LDPE; c: LDPE-5% phosphor composite; d: LDPE-10% phosphor
composite; e: LDPE-20% phosphor composite; f: EDX of LDPE-20%
Na2SO4:Sm3+ composite.
50. Fig. 39 Excitation spectra (left) and emission spectra
(right) of a: pure LDPE; b: LDPE-5%Na2SO4:Sm
composite. c: LDPE-10%Na2SO4:Sm; d : LDPE-
20%Na2SO4:Sm composite.
Fig. 40 (a) PL spectra of the 644nm band for LDPE-
x%Na2SO4:Sm3+ composite (x =0, 5, 10, 20). (b) Relative
intensities of the 644 nm peak in the composites.
51. Outline of the report
• Acknowledgement
• Introduction
• Purposes of the study
• Experimental
• Results and discussion
• Conclusions
• Research accomplishment
52. Conclusions
Main Findings of this study are as follow:
• New vibronic photoexcitation band was observed in neutron- and electron-
irradiated MgO.nAl2O3 single crystals.
• New NIR emission band at a range of 0.8 to 3.0 μm was observed in neutron-
irradiated α-Al2O3 and MgAl2O4which was suggested as F aggregate centers.
The band appeared only after neutron-irradiation at a temperature above room
temperature.
• Anomalous temperature dependence was also observed for the new NIR
emission band in neutron-irradiated α -Al2O3.
• Synthesis of samarium-doped SiO2-Na2SO4 and LDPE-Na2SO4 luminescent
composite was done successfully. Luminescence properties of these new
luminescent composites were also investigated.
53. Outline of the report
• Acknowledgement
• Introduction
• Purposes of the study
• Experimental
• Results and discussion
• Conclusions
• Research accomplishment
54. Research Accomplishment
Publications in Refereed Journal:
10) A. Z. M. S. Rahman, A. S. M. A. Haseeb, Q. Xu, J. Evslin and M. Cinausero, Laser excited novel
near-infrared photoluminescence band in fast-neutron-irradiated MgO.nAl2O3, Radiation Physics
and Chemistry, Vol. 125, pp. 122-126. 2016. doi:10.1016/j.radphyschem.2016.04.001 .
9) A. Z. M. S. Rahman, X. Cao, B. Wang, J. Evslin, Q. Xu and K. Atobe, Synchrotron VUV-UV and
Positron Lifetime Study of Vacancy-Type Defects in Reactor Neutron-Irradiated MgOn Al2O3
(n=2), Cogent Physics, Vol. 3, 1133481, pp. 1-8. 2016. doi:10.1080/23311940.2015.1133481
8) J. Zhang, A. Z. M. S. Rahman, Y. Li, J. Yang, Y. Wu, D. Yuan, X. Cao, R. Yu and B. Wang.
Radiation induced modifications on structural and luminescence properties of LDPE-Na2SO4:Sm3+
composites by gamma-ray, Optical Materials, Vol. 42, pp. 251-255, 2015.
doi:10.1016/j.optmat.2014.12.041
7) A. Z. M. S. Rahman, L. Wei, T. Yang, Q. Xu and K. Atobe, Anomalous temperature dependence of
near infrared photoluminescence band in neutron-irradiated α-Al2O3. Physica Status Solidi A:
Applications and Materials Science, 2014, doi:10.1002/pssa.201330660
6) A. Z. M. S. Rahman, X. Cao, L. Wei, B. Wang, H. Ji, T. Yang, Q. Xu and K. Atobe, Neutron-
irradiation-induced near-infrared emission in ɑ-Al2O3. Philosophical Magazine Letters, Vol. 94,
No. 2, pp. 211-216, 2014. doi:10.1080/09500839.2014.885180.
5) A. Z. M. S. Rahman, Z. Li, X. Cao, B. Wang, W. Long, Q. Xu and K. Atobe, Positron annihilation
study of vacancy type defects in fast neutron-irradiated MgO.n Al2O3. Nuclear Inst. and Methods in
Physics Research B, Vol. 335, pp.70-73, 2014. doi:10.1016/j.nimb.2014.06.002
4) J. Zhang, A. Z. M. S. Rahman, Y. Li, J. Yang, B. Zhao, E. Lu, P. Zhang, X.Cao, R. Yu and B. Wang,
Synthesis and luminescence properties of Sm-doped LDPE-Na2SO4 composite material. Optical
Materials, Vol. 36, Issue 2, pp. 471-475, 2013. doi:10.1016/j.optmat.2013.10.011.
55. 3. A. Z. M. S. Rahman, X. Cao, L. Wei, B. Wang, Y. Tao, Q. Xu and K. Atobe. Vibronic
Photoexcitation Spectra of Irradiated Spinel MgO.nAl2O3 (n=2) at Low Temperatures. Nuclear
Inst. and Methods in Physics Research B, Vol. 305, pp. 33-36. 2013.
doi:10.1016/j.nimb.2013.03.057.
2. A. Z. M. S. Rahman, X. Cao, L.Wei, B.Wang and H.Wu. Luminescence properties of
samarium-doped SiO2-Na2SO4 composite. Materials Letters. Vol. 99, pp. 142-145, 2013.
doi:10.1016/j.matlet.2013.02.078
1. A. Z. M. S. Rahman, X. Cao, L. Wei, B. Wang, R. Yu, Z. Chen, G. An, A. Sidike. Irradiation-
induced valence conversion of samarium ions in Na2SO4. Applied Physics A: Materials Science &
Processing. Vol. 111, Num. 2, pp: 587-591. 2013. doi:10.1007/s00339-012-7266-y
Conference Publications:
2. A. Z. M. S. Rahman, X. Cao, Z. Li, R. Yu, B. Wang, L. Wei, Q. Xu and K. Atobe, VUV-UV
and positron annihilation spectroscopic study of the irradiation induced defects in MgO.nAl2O3
(n=2), 1st China-Japan Joint Workshop on Positron Science, Oral. pp.11-12, Wuhan, China,
October, 2012.
1. A. Z. M. S. Rahman, X. Cao, P. Zhang, Z. Li, R. Yu, B. Wang, L. Wei, T. Awata and Q. Xu.
Possibility of Irradiation induced microstructure formation in α-Al2O3 , 11th Conference of China
Positron Spectroscopy Society, Oral. pp. 72-74, Sichuan, China, September, 2012.
56. Acknowledgements
• Dr. Marco Cinausero, INFN-LNL
• Chinese Academy of Sciences Young
International Scientist Fellowship
• Natural Science Foundation of China
• High Impact research grant, University of
Malaya, Ministry of Higher Education,
Malaysia
• Ministry of Education MEXT, Japan