Higher Wavelength Side Research Articles

Influence of Nano Filler (ZrO2) on Optical and Thermal Studies of Potassium Doped Polyethylene Oxide Solid Polymer Electrolytes

Solid polymer electrolyte films made with potassium doped Polyethylene oxide using ZrO2 as nanofiller (70PEO-30KBF4-x ZrO2 where x = 1, 2.5, 5, 7.5, & 10 wt% ­­) were prepared by solution casting technique. Optical and thermal properties of polymer electrolyte films were studied by using Optical absorption and DSC techniques. From Optical absorption spectra, it is observed that fundamental absorption edge is shifted towards the higher wavelength side (range 259- 297 nm) with increase of nano filler (ZrO­2) concentration (1-10 wt %). Optical band gap for all electronic transitions (p=1/2, 2, 2/3 and 1/3) are found to be increased as incorporation of nano filler (ZrO2) which confirms the structural rearrangements takes place in polymer electrolyte films. Optical band gap for indirect allowed transitions (p=1/2) are found to be in the range of 1.93-3.34eV. Decrease in Urbach energy (4.8eV- 1.4eV) is associated with decrease in defect formation in host polymeric matrix (PEO-KBF4) as a result of embedded nano filler (ZrO2). DSC spectra analysis of polymer electrolytes has showed melting temperatures in the range 63.63-73.71°C and highest crystallinity is found to be 85 % (10 wt % ZrO­2). Enthalpy values are elevated with increase in nanofiller composition (ZrO2) in the present polymer electrolyte films.Keywords: PEO based polymer electrolytes, Solid polymer electrolytes, Optical and Thermal studies.

Rare earth metals (Ce and Nd) induced modifications on structural, morphological, and photoluminescence properties of CuO nanoparticles and antibacterial application

The undoped and rare earth metals (Ce and Nd) doped CuO nanoparticles were prepared by the co-precipitation method. The synthesized NPs exhibited a monoclinic structure and the secondary phase corresponding to dopants was traced in XRD spectra. A strong correlation was noticed between calculated average crystallite size from XRD and FESEM images. The Ce dopant enhanced agglomeration of NPs and Nd turned the particle morphology into a nano-spam like structure. Elemental compositions were obtained from EDAX spectra. The rare-earth dopant produced a blue shift in the bandgap of NPs, hence the absorption edge was shifted towards the higher wavelength side. The NBE emission in the UV region and defects related to violet, blue and green emissions were noticed in the PL spectra of NPs. The antibacterial activity of NPs was studied against gram-negative bacteria (E. aerogenes) and gram-positive bacteria(B. subtilis). The average crystallite size, chemical composition, and cell wall membrane of bacteria were influenced by the antibacterial activity of NPs.

Role of Bi3+ ions on structural, optical, photoluminescence and electrical performance of Cd0.9-xZn0.1BixS QDs

In this work, the Cd0.9-xZn0.1BixS QDs with different compositions of Bi3+ ions (0 ≤ x ≤ 0.05) were synthesized using a facile chemical route. The prepared QDs were characterized for analyzing the structural, morphological, elemental, optical, band gap, photoluminescence and electrochemical properties. XRD results confirmed that the Cd0.9-xZn0.1BixS QDs have a cubic structure. The mean crystallite size was increased from ~ 2 to ~ 5 nm for the increase of Bi3+ ions concentration. The optical transmittance behavior was decreased with increasing Bi3+ ions. The scanning electron microscope images showed that the prepared QDs possessed agglomerated morphology and the EDAX confirmed the presence of doped elements as per stoichiometry ratio. The optical band gap was slightly blue-shifted for initial substitution (Bi3+ = 1%) of Bi3+ ions and red-shifted for further increase of Bi3+ compositions. The optical band gap was ranged between 3.76 and 4.0 eV. High intense red emission was received for Bi3+ (1%) doped Zn:CdS QDs. The red emission peaks were shifted to a higher wavelength side due to the addition of Bi3+ ions. The PL emission on UV-region was raised for Bi3+ (1%) and it was diminished. Further, a violet (422 nm) and blue (460 nm) emission were received for Bi3+ ions doping. The cyclic voltammetry analysis showed that Bi3+ (0%) possessed better electrical properties than other compositions of Bi3+ ions.

Effect of Cu doping on the structural, optical and electrical properties of ZnO thin films grown by RF magnetron sputtering: application to solar photocatalysis

RF sputtered undoped and Cu doped ZnO (CZO) thin films were deposited on unheated glass substrates using a mixed Cu2O and ZnO powders target at different Cu concentrations of 0, 1, 2, 3 and 4 wt%. The effects of copper concentration on the structural, electrical, optical and photocatalytic properties of CZO films have been studied. From XRD and Raman spectroscopy studies, it was found that the deposited films were polycrystalline with a predominant hexagonal wurtzite structure along the c-axis perpendicular to the substrate surface. The presence of multiple interference fringes in the transmittance and reflectance spectra shows the good homogeneity of the films. All the films are highly transparent with transparency reaching 80% indicating the possibility to use these films as an optical window. The absorption tail gradually shifted towards a higher wavelength side, which resulted in the decrease of bandgap energy from 3.35 to 3.26 eV. All the sputtered films are highly conductive with a conductivity reaching 104 S.cm−1.The effect of Cu-doping on the photocatalytic activity of ZnO thin films for the degradation of methylene blue (MB) dye was studied under sunlight irradiation and the results showed that the Cudoping provokes appreciable degradation of MB and reached a maximum for the 1 wt% Cu doped ZnO film.

Influence of defects on the structural, optical, photoluminescence and magnetic properties of Cr/Mn dual doped ZnO nanostructures

Cr (2%) doped ZnO and Cr, Mn (Cr = 2% and Mn = 2–4%) dual doped ZnO nanostructures were synthesized by chemical co-precipitation route. The hexagonal structure of Cr/Mn doped ZnO was not distorted by Mn doping and no secondary/impurity phases of Cr/Mn were detected in the XRD pattern. The reduced crystallite size at Mn = 2% is due to depression of growth rate and the dissimilarities between dopant and host ions and elevated crystallite size at 4% is accountable for the more defect sites in Zn-Cr-O lattice. The stable c/a ratio (~ 1.603) indicates that the hexagonal ZnO wurtzite structure of the synthesized composite is not affected by Mn substitution. The reduced crystallite size and the elevated UV–visible absorption at the higher wavelength side i.e., visible range at Mn = 2% recommended it for improved photocatalytic and efficient for solar cell applications. The broadening of energy gap at Mn = 2% is explained by Burstein-Moss (BM) band filling effect through energy level diagram. The presence of Zn-O-Cr/Mn bonding is confirmed by Fourier transform infra-red (FTIR) studies. The elevated PL emission and the intensity ratio between the green and blue emissions revealed the existence of more oxygen vacancies and oxygen related defect sites in Zn-Mn-Cr-O lattice. The exhibited room temperature ferromagnetism (RTFM) with strong magnetization in Cr, Mn doped ZnO is induced by both the oxygen vacancy mediated bound magnetic polarons (BMP) and the enhanced exchange coupling among the free electrons and local spin polarized electrons.

Comparison of I–V Characteristics of the Fabricated SnS/Si and SnS:Ag/Si Heterojunction Solar Cell Under Dark and Illumination

SnS and SnS-Ag nanocomposite were synthesized by a cost-effective solvothermal technique. Structural properties were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Elemental composition was confirmed by electron diffraction x-ray analysis (EDAX). The optical properties were characterized by UV–Vis absorption spectra, photoluminescence spectra (PL) and time-correlated single-photon counting (TCSPC). XRD results suggest that the samples are in an orthorhombic structural phase. TEM results indicate that quantum dot-like particles (5 nm to 8 nm) are observed in both SnS and SnS-Ag nanostructures. The crystalline nature of the samples was confirmed by selected-area electron diffraction (SAED). EDAX analysis confirmed that Ag is present in SnS-Ag nanocomposite. From optical absorption study, it is clear that SnS-Ag nanocomposite is a better absorber in sunlight than SnS nanocrystal. A decrease in the band gap of SnS-Ag nanocomposite was observed compared to SnS. The PL study indicates that a peak shift of SnS-Ag nanocomposite was observed towards the higher wavelength side. Our aim is to grow cost-effective heterojunction solar cells with good efficiency. J–V characteristics of the fabricated SnS/Si and SnS:Ag/Si heterojunction solar cells have been studied under dark as well as under illumination. Open-circuit voltage (Voc), short-circuit current (Jsc), fill factor (FF) as well as efficiency (η) were determined.

Application of a calcined animal bone to synthesis of graphitic carbon nitride composite

ABSTRACT Graphitic carbon nitride (g-C3N4) is a polymeric organic semiconductor that has been extensively developed for various applications. In this study, composites of g-C3N4 and calcined animal bone (CAB) were facilely synthesized by calcining a mixture of urea and CAB at different temperatures. The results revealed that the calcination temperature influenced yield, crystallinity, and band gap of g-C3N4. In addition, ultraviolet–visible diffuse reflectance spectroscopy indicated a shift in absorption edge to the high wavelength side in the presence of CAB, implying that CAB promoted thermal condensation of urea. However, thermogravimetric measurements revealed that g-C3N4 yield decreased as the calcination temperature increased in the presence of CAB. This is because the amount of g-C3N4 was scarce when the mixture was calcined at 823 K. Furthermore, the results of differential thermal analysis indicated that g-C3N4 and its intermediates were oxidatively decomposed by CAB at 823 K.

Thin film characterization of Ce and Sn co-doped CdZnS by chemical bath deposition

Abstract Cerium and tin co-doped cadmium zinc sulfide nanoparticles (CdZnS:Ce)Sn were synthesized by chemical bath deposition method with a fixed concentration of Ce (3.84 mol%) and three different concentrations of Sn (2 mol % and 4 mol% and 6 mol%). They showed broad photoluminescence spectra in the visible region under the ultraviolet excitation with a wavelength of 325 nm. The photoluminescence emission peaks were obtained at 540 nm, 560 nm and 570 nm for CdZnS, CdZnS:Ce and (CdZnS:Ce)Sn thin films, respectively having different concentrations of Sn. It has been observed that the photoluminescence emission peak shifted to higher wavelength region with an increase in intensity by Ce doping and Ce–Sn co-doping. Further enhancement in luminescence peak intensity has been observed by increasing concentration of Sn in (CdZnS:Ce)Sn films. Average crystallite size, measured from XRD data, was found to be increased with increasing concentration of Sn. An increase in the concentration of Sn shifted the UV-Vis absorption edge toward the higher wavelength side. Energy band gap for undoped CdZnS and Ce–Sn co-doped CdZnS varied from 2.608 eV to 2.405 eV. The SEM micrographs of CdZnS and (CdZnS:Ce)Sn films showed the leafy-like and ball-like structures. The presence of Sn and Ce was confirmed by EDAX analysis.

Effect of electrolyte concentration on morphological and photoluminescence properties of free standing porous anodic alumina membranes formed in oxalic acid

The free-standing porous anodic alumina membranes (AAM) were prepared in oxalic acid by varying electrolyte concentration from 0.1 to 0.9 M with a constant potential of 40 V at 8 °C. The influence of electrolyte concentration on the morphological and optical features of AAM has been studied. Regularity ratio (RR) of AAM was measured using WSxM software, highest RR obtained for AAM formed in 0.3 M. From X-ray diffraction (XRD) analysis, it was found that prepared AAM were amorphous in nature. UV–Vis absorbance spectra reveal that absorbance bands slightly moves towards the higher wavelength side with increasing electrolyte concentration. Photoluminescence (PL) of AAM has been studied and related with RR of AAM. PL measurements of AAM exhibit strong PL peak in blue region, having a slight change with increasing electrolyte concentration. PL bands were originating from two kinds of oxygen-deficient defects (F and F+), their distributions were discussed on the basis of PL spectrum.

Intensity dependent spectral properties of long-period fiber grating for applications in lightwave communication

Using nonlinear coupled mode equations, the spectral properties of long-period fiber grating are studied analytically taking into account the Kerr type optical nonlinearity in the medium. The nonlinear coupled-mode equations were solved for co-propagating core and cladding mode amplitudes and expressions for transmittivity and phase factor at high excitation intensity are obtained. It is observed that the resonance wavelength of grating shifts towards higher wavelength side with increasing excitation intensity. Also, the minimum transmittivity of the grating shows oscillating behavior with increasing grating length, whereas the phase of the transmitted wave increases monotonically with length at high input intensities.

Investigation of modifier effect on the spectroscopic properties of Sm3+ ions in binary boro‑bismuth glasses

Trivalent samarium (Sm3+)-doped boro‑bismuth glass systems are prepared using the well-known melt quenching technique and studied their physical and spectroscopic properties. Theoretical optical basicity of the glasses are evaluated using the glass compositions. The optical absorption spectra are used to predict the optical band gap and bonding parameters of glasses. The ultra violet (UV) cutoff wavelength is increasing towards the higher wavelength side with increase in bismuth concentration. Judd-Ofelt parameters are obtained from absorption spectrum and are inturn used to estimate radiative properties for various excited states of the Sm3+ ions in boro‑bismuth glasses. Luminescence decay curves of the 4G5/2 level in the Sm3+-doped boro‑bismuth glasses are measured under 402 nm excitation. The decay times exhibit single exponential nature for lower concentrations (≤0.1 mol%) and tends towards non-exponential with increase in Sm3+ concentrations (≥0.5 mol%). The non-exponential decay curves of higher Sm3+-doped glasses are fitted to the Inokuti-Hiriyama model to know the nature of interaction for energy transfer between the Sm3+ ions. The chromaticity color coordinates for present glass systems are also evaluated and found that the luminescence color falls in the reddish-orange region.

Shifting of the absorption edge in TiB2/TiB(N)/Si3N4 solar selective coating for enhanced photothermal conversion

The concentrated solar power systems for solar energy applications demand the development of solar absorber coatings with high spectral selectivity. This is possible by careful compositional selection of absorber thin films with an aim to shift the optical absorption edge towards higher wavelength side. In this context, the present work aims at developing such a coating, based on TiB2/TiB(N)/Si3N4 by tailoring magnetron sputtering parameters. This multilayer exhibits a high absorptance of 0.964 and a moderately low emittance of 0.18 at 82 °C. The attainment of excellent spectral selectivity has been explained in terms of systematic variation or gradient in refractive index and extinction co-efficient throughout the multilayer stack.

Low-cost wavelength-selective evanescent fiber optic temperature and refractive index sensor

We report here a low-cost evanescent field wave fiber optic temperature sensor. The amount of rays guided along the fiber probe is the result of the absorption of evanescent waves produced at the core-cladding interface. We systematically investigate the wavelength dependence of this sensor during the measurement of the temperature. The degree of variation with respect to the temperature is also determined by alteration of measuring liquid. We observe an enhanced responsivity of the fiber sensor towards a higher wavelength side. The sensor set-up offers simultaneous detection of refractive indices when correlated with temperature variation. All the results reported here bear a good repeatability.

Synthesis and characterization of Sn-doped CdZnS nanoparticles

Tin (Sn)-doped cadmium zinc sulphide nanoparticles (CdZnS: Sn) were synthesized by the chemical bath deposition method with two different concentrations of Sn (2 and 4 mol%). X-ray diffraction (XRD) pattern reveals the formation of CdZnS nanoparticles with cubic and hexagonal structure. It was observed that the presence of Sn does not alter the structure of CdZnS. Average crystallite size was measured from XRD data by using Scherrer’s formula. From the study of absorption spectra, band-to-band absorption was obtained at 460 and 490 nm, respectively, for the Sn-doped (2 and 4 mol%) CdZnS nanoparticles. Energy bandgap for undoped and Sn-doped CdZnS varies from 3.5 to 2.9 eV with error ±0.05 eV. The presence of Sn was confirmed by energy-dispersive X-ray analysis. The effect of dopant concentration on the photoluminescence (PL) intensity has also been studied. The PL emission peak has been observed at 540, 550 and 560 nm for the Sn-doped (CdZnS, CdZnS 2 mol% and CdZnS 4 mol%), respectively, nanoparticles. XRD and PL analyses demonstrate that the Sn2+ ions uniformly substitute Cd2+ sites or interstitial sites in CdZnS lattice, which influence the optical properties. Increase in the concentration of Sn shifts the UV–vis absorption spectra and PL emission spectra towards higher wavelength side. Particle size and the crystallinity of CdZnS : Sn nanoparticles were confirmed through atomic force microscopy.

The physical and chemical properties of gamma ray irradiated polymer electrolyte films

The physical and chemical properties of Gamma ray irradiated polymer electrolyte (PEO-CdCl2) films have been investigated. The FT-IR result evidenced the degradation due to chain scission/cross linking in the irradiated films. The DSC and TGA results show that thermal stability and crystallinity are significantly decreased in irradiated films. The optical micrograph image shows the size of spherulite structure and surface roughness found to be decreased with increasing the irradiation dose. The increase in the optical absorption and shifts toward higher wavelength side was observed in the irradiated film. Also optical band gaps (Eg), Urbach energy is estimated and found to be decreased, meanwhile the number of carbon atoms in cluster increased with the dose. The changes of dielectric permittivity, AC conductivity and optical band gap after irradiation were attributed due to degradation. The high conductivity of 1.156×10−4Scm−1 observed in the 150kGy irradiated film; it was about to order magnitudes higher than that of non-irradiated film. The electric modulus results were depicts the relaxation time (τ) found decreased and broadening of peaks signifies it is the Non-Debye relaxation behavior. These obtained results reveal that there is a possibility of improving physical properties polymer electrolyte and it may open up various opportunities to use these materials in different applications.

Localized surface plasmon resonance and refractive index sensitivity of vacuum-evaporated nanostructured gold thin films

Plasmonic properties of vacuum-evaporated nanostructured gold thin films having different types of nanoparticles are presented. The films with thickness ≥6 nm show the presence of nanorods having non-cylindrical shape with triangular base. Two characteristic plasmon bands have been recorded in absorption spectra. First one occurs below 500 nm and the other one at higher wavelength side. Both the peaks show dependence on the dielectric property of surroundings. The higher wavelength localized surface plasmon resonance peak shifts to higher wavelength with an increase in the nanoparticle size, surface roughness and refractive index of the surrounding (methylene blue dye coating). This shows that such thin films can be used as sensor for organic molecules with a refractive index sensitivity ranging from 250 to 305 nm/RIU (refractive index unit).

PVA assisted low temperature anatase to rutile phase transformation (ART) and properties of titania nanoparticles

Anatase to rutile phase transformation (ART) of titania nanoparticles is observed at very low temperature (180 °C) just by introducing polyvinyl alcohol (PVA) during co-precipitation followed by hydrothermal synthesis. The detailed investigations pertaining to the structural, optical and electrochemical properties of the nanosized titania and titania/PVA nanohybrid has been carried out. The crystallite size and crystal structure is confirmed using X-ray diffraction (XRD). Transmission electron microscopic (TEM) image reveals formation of spherical NPs in both the cases. Identification of functional groups is done using Fourier transform infrared spectroscopy (FTIR). The photoluminescence studies showed that emission slightly shifts towards higher wavelength side with remarkable decrease in intensity for TiO2/PVA nanocomposite (rutile samples). The remarkable decrease in PL intensity in TiO2/PVA nanocomposite (rutile samples) is explained considering the surface passivation during growth process. Ion transportation is monitored via Cyclic voltammetric (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. A significant enhancement of peak cathodic current in case of nanocomposite modified electrode is observed. It is assumed that TiO2/PVA (rutile) nanoparticles provided the conducting path for the electrons and hence enhanced the electrochemical reaction.

Structural, Optical And Electrical Properties Of Cu(InGa)SeTe Device With The Varying Laser Pulses

Next generation high performance heterojunction photovoltaic (PV) modules can be fabricated with an appropriate active layer material. Therefore, it is worth to examine physical properties of the recent developed Cu25(In16Ga9)Se40Te10 (CIGST) material for the potential photovoltaic application. This, report demonstrates the structural, optical and electrical properties of the 8000 and 16000 pulses deposited CIGST films on top of the ITO coated soda lime substrate (CIGST/ITO/substrate); whereas, the substrate temperature was 550 0 C. The 16000 pulses deposited thin film surface roughness (45 nm) and thickness (~1.4 μm) are obtained lower and higher than the 8000 pulses thin film. The cross sectional EDS elemental mapping also gives the fewer interlayer inclusions for the 8000 pulses deposited thin film. With the increasing thin films thicknesses a distinguishable UV/Visible peak shift toward the high wave length side and enhance in optical energy band gap (1.13 and 1.2 eV) are noticed. Device fabricated (CIGST/ITO/substrate) with the 16000 pulses have a sharp current growth upto 2.0 × 10 -2 amp with a lower resistance under the applied voltage range 0-20V. The internal (IQE) and external (EQE) quantum efficiencies charge carriers transport for the fabricated devices are also discussed. Copyright © 2015 VBRI Press.

Synthesis and characterization of cerium-doped CdZnS nanoparticles

Cerium-doped cadmium zinc sulfide nanoparticles (CdZnS:Ce) were synthesized by chemical bath deposition method with three different concentrations of cerium (1.2, 2.5 and 3.84 mol%). X-ray diffraction pattern revealed the formation of cadmium zinc sulfide nanoparticles with cubic and hexagonal structure. It was observed that the presence of ceria did not alter the structure of CdZnS. Average crystallite size was measured from X-ray diffraction data by using Scherrer’s formula. From the study of absorption spectra, band-to-band absorption was obtained at 455 and 470 nm, respectively, for the Ce-doped (2.5 and 3.84 mol%) CdZnS nanoparticles. Energy band gap for undoped and Ce-doped CdZnS varied from 3.45 to 3.15 eV with error ±0.05 eV. The presence of cerium was confirmed by energy-dispersive analysis of X-rays. The effect of dopant concentration on the photoluminescence intensity was also studied. The photoluminescence emission peak was observed at 520, 540 and 560 nm, respectively, for the Ce-doped (1.2, 2.5 and 3.84 mol%) CdZnS nanoparticles. X-ray diffraction and photoluminescence analysis demonstrated that the Ce3+ ions uniformly substituted Cd2+ sites or interstitial sites in CdZnS lattice, which influenced the optical properties. An increase in the concentration of cerium shifted the UV–Vis absorption spectra and photoluminescence emission spectra toward the higher wavelength side. Particle size and the crystallinity of CdZnS:Ce nanoparticles were confirmed through transmission electron microscopy and selected area electron diffraction patterns.

Gd2O3:SiO2 Nanocomposite: Study on Structural and Optical Behavior

Gd(NO3)3·6H2O and TEOS were used as precursors and obtained powdered form of Gd2O3:SiO2 nanocomposite. The as‐prepared sample was annealed at 773 K and 1173 K and characterized by XRD, TEM, UV–Vis spectra, and PL. The average nanocrystallite size was found of the order of ~27 nm using well‐known Debye–Scherer's equation. From the UV–Vis spectra, it was shown that the position of absorption peak has been shifted toward the higher wavelength side with temperature. In the PL spectra, the broad emission band has been observed at 583 nm along with weak bands at 516, 526, and 556 nm.