Growth of silver nanoparticles within the tellurovanadate amorphous matrix: Optical band gap and band tailing properties, beside the Williamson-Hall estimation of crystallite size and lattice strain

2019 ◽  
Vol 45 (6) ◽  
pp. 7857-7864 ◽  
Author(s):  
Yazdan Shahmoradi ◽  
Dariush Souri
Keyword(s):  
Silver Nanoparticles ◽  
Band Gap ◽  
Crystallite Size ◽  
Optical Band Gap ◽  
Lattice Strain ◽  
Amorphous Matrix ◽  
Band Tailing

Effect of Tin Composition on Cu2ZnSnS4 Photovoltaic Absorbers

2012 ◽  
Vol 534 ◽  
pp. 156-159 ◽  
Author(s):  
Dong Hua Fan ◽  
Rong Zhang ◽  
Hui Ren Peng
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Band Gap ◽  
Crystallite Size ◽  
Optical Band Gap ◽  
Diffraction Peak ◽  
X Ray Diffraction ◽  
X Ray ◽  
Poor Condition ◽  
Czts Thin Films

Cu2ZnSnS4 (CZTS) thin films are prepared by sulfurizing the precursors deposited by vacuum evaporation methods. The samples sulfurized at 500°C for 3h shows the strong (112) diffraction peak at 28.45˚, suggesting the successful synthesis of CZTS thin films. The X-ray diffraction shows that CZTS thin film prepared in Sn-poor condition have the best crystallinity. The Sn-dependent crystallite size was calculated to be 19.53-21.03 nm. In addition, we found that the optical band gap with various Sn contents can be modulated at 1.48-1.85 eV

scholarly journals Enhancement of Fluorescence and Photostability Based on Interaction of Fluorescent Dyes with Silver Nanoparticles for Luminescent Solar Concentrators

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Sara El-Molla ◽  
A. F. Mansour ◽  
A. E. Hammad
Keyword(s):  
Silver Nanoparticles ◽  
Band Gap ◽  
Optical Band Gap ◽  
Fluorescent Dyes ◽  
Organic Dyes ◽  
X Ray Diffraction ◽  
Absorption Bands ◽  
Solar Concentrators ◽  
Luminescent Solar Concentrators ◽  
Silver Nps

For luminescent solar concentrators (LSCs), it is important to enhance the fluorescence quantum yield (FQY) and photostability. Our measurements have demonstrated that the addition of silver nanoparticles to dye solution causes broadening of absorption bands, so the spectral range of sunlight absorbed by LSC has increased. Silver nanoparticles (NPs) were characterized by X-ray diffraction (XRD) and UV-Vis absorption spectra. UV-Vis spectrum showed a single peak at 442 nm due to the surface plasmon resonance (SPR). The position of SPR peak exhibited a red shift after the sample was exposed to UV irradiation (unfiltered light). The optical band gap values have a reduction from 2.46 to 2.37 eV after irradiation for 960 minutes. Such reduction in optical band gap may be due to change in particle size calculated using Mie theory. The photostability of organic dyes used was improved after adding silver nanoparticles. The area under fluorescence spectra of dyes with silver NPs increased by 41–31% when compared with identical dye concentrations without silver nanoparticles as a result of interaction of the species with silver NPs.

STRUCTURAL PARAMETERS AND OPTICAL CONSTANTS OF CdS NANOCRYSTALLINE THIN FILMS

NANO ◽  
2011 ◽  
Vol 06 (03) ◽  
pp. 251-258 ◽  
Author(s):  
B. VISWANATHAN ◽  
J. DHARMARAJA ◽  
J. BALAMURUGAN
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Band Gap ◽  
Crystallite Size ◽  
Optical Conductivity ◽  
Optical Constants ◽  
Optical Band Gap ◽  
Structural Parameters ◽  
Stoichiometric Composition ◽  
Bath Temperature

Optical constants of cadmium sulfide (CdS) thin films were determined in the spectral range of 400–1200 nm from optical absorption and transmittance measurements for different bath temperatures. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) were the techniques used to determine the crystallite structure and morphology of the films. EDX images showed that a sample had a stoichiometric composition. The crystallite size and microstrain were calculated using the Williamson–Hall method. The optical band gap values of the films varied from 2.35 eV to 2.5 eV, depending on the bath temperature. Optical study was performed to calculate the refractive index (n), extinction coefficient (k), optical conductivity (σ), dielectric constant (real and imaginary), and optical band gap using transmission spectra. It has been observed that the conductivity of the synthesized films has a close relationship with the size of the crystallites. The optical conductivity and the crystallite size increase at a temperature of up to 70°C and then start decreasing when the temperature is still increased due to the change in phase from hexagonal to cubic in nature. Moreover, we observed that beyond this temperature the XRD peak shifts toward the nanoregion. The values of microstructure parameters change drastically, whereas the trend of optical constants remains the same.

Influence of different materials on the microstructure and optical band gap of α-Fe2O3 nanoparticles

2014 ◽  
Vol 32 (2) ◽  
pp. 193-197 ◽  
Author(s):  
P. Mallick
Keyword(s):  
Band Gap ◽  
Crystallite Size ◽  
Optical Band Gap ◽  
Strain Analysis ◽  
The Other ◽  
Fe2o3 Nanoparticles ◽  
Direct Band Gap ◽  
Direct Band ◽  
Indirect Band Gap ◽  
Composite Samples

AbstractComposites of hematite (α-Fe2O3) nanoparticles with different materials (NiO, TiO2, MnO2 and Bi2O3) were synthesized. Effects of different materials on the microstructure and optical band gap of α-Fe2O3 nanoparticles were studied. Crystallite size and strain analysis indicated that the pure α-Fe2O3 nanoparticles were influenced by the presence of different materials in the composite sample. Crystallite size and strain estimated for all the samples followed opposite trends. However, the value of direct band gap decreased from ∼2.67 eV for the pure α-Fe2O3 nanoparticles to ∼2.5 eV for α-Fe2O3 composites with different materials. The value of indirect band gap, on the other hand, increased for all composite samples except for α-Fe2O3/Bi2O3.

Effect of Mineralizer (KNO3) on the Structural and Optical Properties of h-MoO3 Nanocrystals

2012 ◽  
Vol 585 ◽  
pp. 110-114
Author(s):  
A. Chithambararaj ◽  
Arumugam Chandra Bose
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Crystallite Size ◽  
Optical Band Gap ◽  
Diffuse Reflectance Spectroscopy ◽  
Hexagonal Phase ◽  
Thermo Gravimetric Analysis ◽  
Average Crystallite Size ◽  
Precipitation Method ◽  
Gravimetric Analysis

Single phase hexagonal molybdenum oxide (h-MoO3) nanocrystals were successfully synthesized by solution based chemical precipitation method. The effect of mineralizer (KNO3 salt) on hexagonal phase, crystallite size, and surface morphologies of MoO3 was investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analysis. The XRD result indicates that the diffractograms exhibit characteristic hexagonal phase of MoO3. From the line broadening analysis, the average crystallite size was calculated and estimated. A less crystallite size of 34 nm was obtained in the presence of mineralizing agent KNO3 in comparison to without mineralizer (46 nm). The particle exhibits rod like morphology with perfect hexagonal cross-section and well faceted top and side surfaces. Further, the thermal and optical properties were studied by thermo gravimetric analysis (TGA) and diffuse reflectance spectroscopy (DRS) measurements. The weight loss due to decomposition of intercalated water and ammonia were observed. By TGA analysis, the mineralizer assisted sample shows higher phase stability with the phase transition temperature of 520 °C due to the incorporation of K+ in MoO3 structure. The optical band gap energy was calculated using Kubelka-Muck function and the values were found to be 3.11 eV and 2.97 eV for KNO3 assisted and non-assisted MoO3 samples respectively. The observed increase in optical band gap (Eg) for h-MoO3 synthesized in the presence of KNO3 was attributed to the size dependent optical properties.

scholarly journals Preparation and characterization of nano-sized magnesium ferrite powders by a starch-gel process and corresponding ceramics

2019 ◽  
Author(s):  
Roberto Köferstein
Keyword(s):  
Band Gap ◽  
Crystallite Size ◽  
Optical Band Gap ◽  
Hysteresis Loops ◽  
Blocking Temperature ◽  
Zero Field ◽  
Superparamagnetic Behaviour ◽  
Starch Gel ◽  
Sintering Behaviour

The synthesis and characterization of nano-sized MgFe2O4 by a starch-gel methodis described herein. A phase-pure nano-sized MgFe2O4 powder (1a) was obtained aftercalcining a (MgFe)-starch gel at 550 °C. The powder has a specific surface area of 60.6 m2/gand a crystallite size of 9 nm. TEM investigations reveal particles in the range of 7 to 15 nm.The activation energy of the crystallite growth process was calculated as 89 ± 14 kJ/mol. Theshrinkage and sintering behaviour of resulting compacts were studied. UV−VIS investigationsof the nano-sized powder 1a reveal an optical band gap of 2.38 eV, whereas calcination at1100 °C (powder 1g) leads to a crystallite size of 129 nm and a band gap of 2.16 eV.Magnetization loops at 300 K and the temperature dependence of both the field-cooled (FC) and the zero-field-cooled (ZFC) magnetization indicate a superparamagnetic behaviour. The blocking temperature for powder 1a was determined as 140 K at a field of H = 500 Oe. Wefound different saturation magnetizations (Ms) depending on the calcination temperature. Calcination at 550 °C (1a) results in Ms = 20.0 emu/g which increases with calcinationtemperature to a maximum of 37.7 emu/g for powder 1e calcined at 900 °C. Ceramic bodiessintered between 1450 and 1600 °C exhibit Ms values of 25−28 emu/g. Magnetic investigations at 10 K on powders 1a−1g show hysteresis loops with coercivities up to 950Oe, remanences to 10 emu/g and Ms values to 50.4 emu/g. Additionally, the nano-scaled powders show a shift of the hysteresis loops.

EFFECT OF B2O3 ON PHYSICAL AND OPTICAL PROPERTIES OF ZINC PHOSPHATE GLASSES

2006 ◽  
Vol 20 (26) ◽  
pp. 1637-1643
Author(s):  
M. ALTAF ◽  
M. A. CHAUDHRY ◽  
M. TARIQ BHATTI
Keyword(s):  
Band Gap ◽  
Optical Band Gap ◽  
Zinc Phosphate ◽  
Mass Density ◽  
Band Gap Energy ◽  
Phosphate Glasses ◽  
Exponential Dependence ◽  
Amorphous Nature ◽  
Sharp Edges ◽  
Band Tailing

Zinc-phosphate glasses with the addition of B 2 O 3 were prepared by using the melt quench technique. These glasses had a mol% composition of 30 ZnO -x B 2 O 3 - (70-x) P 2 O 5. The quantity x had values of 10–40 mol%. The mass density of these glasses was found to be in the range of 2.4912–3.0142 g/cm3. The oxygen packing density and molar volume were estimated to lie in the range 192.385–286.026 g-atom/liter and 46.78–31.46 cm3 respectively. The absorption spectra of these glasses were recorded in the range of 190 to 1100 nm. No sharp edges were found in the optical spectra, which confirms the amorphous nature of these glasses. The optical band gap energies were determined to be in the range of 2.40–3.00 eV. A decreasing behavior in optical band gap energy was seen due to the increasing concentration of B 2 O 3. The extent of band tailing was worked out from the Urbach plots, which showed an exponential dependence of absorption coefficients on photon energies.

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