Oriented thin films have been prepared using pulsed laser deposition technique on Si (001) and SrTiO3 (STO) (001) substrates. The surface morphologies of films grown on Si substrates are more uniform than STO substrate. Physical properties of BaBiO3 thin films have been studied using Raman and x-ray photoelectron spectroscopic (XPS) techniques. Room temperature Raman spectroscopy confirms the presence of charge-ordering both in bulk and thin films. Our XPS results however show that the charge-disproportionation of Bi oxidation state (4-delta) and (4-delta) with delta<1 bulk has been modified in thin films to delta=1.
In Si nanowire (SiNW) solar cells enhanced light confinement property in addition to decoupling of charge carrier collection and light absorption directions plays a significant role to resolve the draw backs of bulk Si solar cells. In this report we have studied the dependence of the phovoltaic properties of Si NW array solar cells on the SiNW length and enhanced surface defect states as a result of enhanced surface area of the NWs. The SiNW arrays have been fabricated using metal catalyzed electroless etching (MCEE) technique. p-n junction has been produced by spin-on-dopant technique followed by thermal diffusion process. Front and rear electrodes have been deposited by e-beam evaporation techniques. SiNW lengths have been controlled from ~ 320 nm to 6.4 micro meter by controlling the parameters of MCEE technique. Photovoltaic properties of the solar cells have been characterized by measuring quantum efficiency and photocurrent density vs. voltage characteristics. Morphological studies have been carried out by using scanning electron microscopy. Reduction in light trapping capability comes at the benefit of reduced surface defects. The reduction of surface defects has been proved to be more advantageous in comparison to the decrement of light trapping capability. The major contribution to the changes in cell efficiency comes from the enhancement of short circuit current density with a very weak dependence on open circuit voltage. This work is beneficial for the production commercial Si solar cell where SiNW arrays could be used as a antireflection coating instead of using separate antireflection layers and thus could reduced the production cost.
We present the synthesis of functionalized-silicon nanowire (f-SiNWs) array which is currently an intense subject of research due to a wide range of opportunities for new generations of nanoscale electronic and optical devices. SiNW arrays were fabricated by a metal-assisted electrodeless wet chemical etching (MEWCE) of highly doped silicon (100) wafers. SiNWs are fabricated at different parameters like etching times, the concentration of chemicals, type of Si wafer, etc. Analysis of various deposition parameters has been carried out to optimize the growth of SiNW. The surface morphology of the etched Si wafer has been carried by electron microscopy. The origin of photoluminescence (PL) in SiNWs has been studied. Phonon confinement effect of functionalization has been analyzed by Raman spectroscopy and PL spectra.
Zero dimensional graphene quantum dots (GQDs) exhibit interesting physical and chemical properties due to the edge effect and quantum confinement. As the number of carbon atoms in edge is more than on basal plane, GQDs are more reactive. Room temperature XRD pattern confirms the formation of the GQDs. UV-Visible spectra confirm that GQDs show optical absorption in the visible region. The emission peaks in the photoluminescence spectra are red shifted with the increase of excitation wavelength. Dynamic light scattering (DLS) analysis shows that the average size of the particles is found to be 65 nm. The frequency dependent electrical transport properties of the GQDs are investigated in a temperature range from 300 to 500 K. Most interestingly, for the first time, the insulator to semiconductor transition of GQD is observed near 400K. The transition mechanism of GQD is discussed with detailed dielectric analysis. The effects of intercalated water on temperature dependent conductivity are clearly discussed. The dielectric relaxation mechanism is explained in the framework of permittivity, conductivity and impedance formalisms. The frequency dependent ac conductivity spectra follows the Jonscher s universal power law. Cole-Cole model is used to investigate the dielectric relaxation mechanism in the sample.
The polycrystalline Fe2Te0.95Ta0.05O6 possessing tetragonal trirutile structure with P4(2)/mnm space group is synthesized via solid state reaction route. Phase confirmation and structural parameter calculation are done by the Rietveld refinement of XRD data. We demonstrate the temperature and magnetic field dependent magnetic property and room temperature magnetoelectric (ME) behavior of the material. The temperature dependent magnetic susceptibility confirms the antiferromagnetic transition at 210K along with a broad transition prior to it due to presence of short range magnetic ordering. The typical temperature response of magnetic susceptibility like Fe2TeO6 parent material differ at 18K as it shows a transitional anomaly due to Ta doping. MH hysteresis measured at 300K and 2K shows an apparent linear behavior. A hysteretic ferromagnetic induction in low field region at 300K is observed due to doping induced modification in exchange interaction mechanisms. Presence of linear ME effect is confirmed through ME voltage measurement wit ME coefficients a/d approximate to 0.23 mV cm(-1) Oe(-1), beta/d approximate to -3.47 x 10(-4) mV cm(-1) Oe(-2), obtained by linear fit to M. Ferroelectric hysteresis loop is obtained by PE loop measurement using remanent polarization measurement with value approximate to 2.5 nC/cm(2).
The This article is to report non toxic, green synthesis cerium oxide nanoparticles (CeO2 NPs) from ammonium ceric nitrate using Moringa oleifera leaf extract as reducing as well as stabilizing agent. The as prepared nanoparticles were characterised by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), UV-Visible diffuse reflectance spectroscopy (UV), and EDAX. The average crystallite size was estimated from the XRD pattern using Debye Scherrer equation as about 9-10 nm. XRD analysis revealed the cubic fluorite structure of the synthesized nanoparticles. FT-IR reflects stretching frequencies at 500 cm-1 which confirmed the Ce-O stretching bands and showing utilization of natural components for the production of nanoparticles. TGA predicts the successful capping of CeO2 NPs by bioactive molecules present in the plant extract. The SEM images reveal that the prepared ceria nanoparticles are composed of spherical nanoparticles in agglomerated form. The as-synthesized CeO2 nanoparticles have antibacterial activity. The desired structural and optical properties of CeO2 make it as promising material for photocatalytic and optoelectronic applications.
(Gd1-xPrx)(5)Si2.1Ge1.8Sn0.1 alloys with x = 0, 0.05, 0.1 and 0.15 have been prepared by arc-melting method, and the crystal structure and magnetic properties were investigated by XRD and VSM measurements respectively. All the alloys adopt an orthorhombic Gd5Si4-type crystal structure as the main phase and undergo ferromagnetic ordering below their respective transition temperatures. The magnetic phase transition is fully reversible in temperature and field indicating a nature of second order phase transition, further confirmed by the Arrott plot technique. The Curie temperature (Tc) and the magnetic entropy change (Delta Sm) were sensitive to the Pr content. A maximum magnetic entropy change of 2.45 J/kg K occur for x=0.1 alloy at 275 K for a low magnetic field change of 1.6 T.
Here we report on X-ray diffraction (XRD), temperature dependent resistivity and Raman measurements of pulsed laser deposition (PLD) grown thin films on Si substrate. XRD confirms coexistence of two, the VO2 M1 and the VO2 B, monoclinic phases at room temperature. Resistivity measurement exhibits a transition from low temperature insulating phase to high temperature metallic phase, indicating major contribution of the VO2 M1 phase. Insulator to metal transition (IMT) is found to occur at similar to 328 K which is similar to 12 K lower compared to bulk VO2. Raman measurements confirm the first order structural phase transition, from low temperature monoclinic to high temperature rutile, concomitant with the IMT. Lowering of the transition temperature in our thin film compared to bulk VO2 is due to strain in the thin film.
MoS2 nanostructure was successfully synthesized by employing one step solvothermal route for electrochemical water splitting applications. Generally, MoS2 nanostructures played a very important role in electrochemical energy field due to its unique physical and chemical properties [1]. In the present study, bare and Ni incorporated MoS2 nanostructures were synthesized via solvothermal route and the rhombohedral phase formation for bare and 5% Ni doped MoS2 was confirmed by X-ray diffraction (XRD) study. On further increasing the dopant concentration as 10%, the phase transformation was strongly influenced and thereby the rhombohedral phase was turned as monoclinic Mo2S3 phase and was evidenced by strong diffraction peak of plane (-101). The phase changing mechanism of Ni dopant on MoS2 nanostructures was also revealed. The luminescent nature of the synthesized nanostructures was studied by photoluminescence (PL) spectra. FTIR result clearly demonstrated the Mo-S vibration of two different phases. SEM images clearly revealed the clumsy growth of nanorods for both the phases of nanostructures. The electrochemical water splitting efficiency of different phase molybdenum sulfides have been explored by cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronoampherometry (CA) studies. The best efficient 10% Ni doped Mo2S3 electrode governed the specific capacitance of 1207 F/g at 10 mV/s scan rate with higher current density of 193 mA/g with good conductivity. Moreover, the very good electrochemical stability was reported for the efficient electrode for 18 h with zero percent decay of its activity even after 18 h of excellent electrochemical water oxidation process. Mechanism of dopant and phase nature on electrochemical performance of the electrode was revealed. Hence, the favorable phase, dopant and morphology of molybdenum sulfide nanostructures for electrochemical water splitting applications were explored in this study.
In this work, combined experimental and theoretical study on 2-methyl p-benzoquinone is reported. The DFT calculations are performed using Gaussian 09 W program for different basis sets. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are carried out with the aid of structural optimizations based on DFT method with B3LYP/6-311++G(d, p) as basis sets. The Non Linear Optical (NLO) parameters, third-order nonlinear optical properties, Natural Bond Orbital (NBO) analysis and Molecular Electrostatic Potential (MEP) of the title molecule is also calculated and interpreted. A study on electronic properties, such as HOMO and LUMO are calculated by time dependent quantum calculations. The present preliminary studies may further be extended both in physical and biological aspects in future for 2-methyl-p-benzoquinone and its analogues. In addition, Marvin Sketch, Swiss ADME, were used to compute physicochemical descriptors as well as to predict Molecular dynamics, ADME parameters, pharmacokinetic properties, log P, pH value, drug like nature and medicinal chemistry friendliness of small molecule. All these properties were analyzed by Computer Aided Drug Designing (CADD) approach to support drug discovery.
Copper tin sulphide (CTS) thin films have been prepared at room temperature on soda lime glass substrate by successive ionic layer adsorption and reaction (SILAR) method. In this work, cationic solution bath contains copper chloride, tin chloride, triethanolamine and anionic bath contains thioacetamide as precursors. Two sets of samples were prepared with 40 and 60 deposition cycles, keeping dipping and rinsing time constant at 10 and 2 seconds respectively. The as- prepared films were characterized by X-ray diffraction (XRD), UV-Vis-NIR spectroscopy, Scanning Electron Microscopy(SEM), Energy Dispersive analysis (EDS) and atomic force microscopy(AFM) analysis. The XRD showed that the film has a triclinic structure. The average crystallite size slightly increases from 21nm to 22.6 nm with increase in deposition cycles. The EDS analysis confirms the presence of Cu, Sn and S.AFM and SEM analysis reveals that the film has a compact structure without any visible cracks or pores. Both the samples have high absorbance in the visible region. The as-deposited CTS samples can be used as absorber layer for solar cell.
In the present study effect of Zn doping on the structural and optical properties of CuO nanoparticles has been investigated. The CuO nanoparticles doped with 0, 1 and 3 wt% Zinc oxide have been prepared by ball milling process for 24 hrs followed by heat treatment for 4 hrs at 500 degrees C. The structural properties have been investigated with the help of X-ray diffraction patterns, which reveals that all the samples contain monoclinic phase of the CuO along with hexagonal ZnO structure in case of doped samples. The lattice parameters and unit cell volume of the CuO nanoparticles show clear dependence on the dopant concentration. The crystallite size and micro-strain of the nanoparticle samples are evaluated using Williamson-Hall peak profile analysis. The Raman spectra are used to evaluate the vibrational properties of the CuO nanoparticles. The optical band energy of the samples has been evaluated from UV-Visible spectroscopy data and shows decreasing trend with increase of Zn doping concentration. The Urbach energy and Micro-strain values indicates that defect introduced by dopant into host matrix are responsible for observed band gap reduction. The presence of various types of defects and vacancies in our samples is confirmed from the Photoluminescence spectroscopy. It can be concluded that tuning of structural and optical properties is possible with the introduction of Zn into CuO lattice.
The Fe3O4 magnetite nanoparticles are the most promising materials in the medical applications because of their biocompatibility, stability and ease in synthesis. In the present study PVP capped iron oxide (Fe3O4) nanoparticles with a size range of 5-9nm were synthesised by the chemical co-precipitation method in an inert environment created by nitrogen gas flow. The PVP coating serves as the stabiliser and controls the crystal growth thereby the particle size. The diameter range of synthesised nanoparticles is preferred in the medical applications such as drug delivery system, MRI contrast agent and hyperthermia is in vicinity of 10nm. The Fe3O4 magnetic nanoparticles were prepared by the aqueous co-precipitation of FeCl3 center dot 6H(2)O and FeCl2 center dot 4H(2)O with addition of sodium hydroxide and PVP at room temperature. The nanoparticles of different diameters were obtained by varying the concentration of the precursors and keeping the other experimental parameters same. The formation of magnetite is confirmed by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The particle size and the morphology are characterized by scanning electron microscopy (SEM) and XRD. The hysteresis loop and the saturation magnetisation were measured by vibrating sample magnetometer (VSM). The results revealed that the magnetic nanoparticles are spherical in shape and with narrow size distribution with high magnetic saturation. With the increase in the concentration of precursors not only the diameter but also the crystallinity and saturation magnetisation increases. The synthesised nanoparticles are ideal candidate for the hyperthermia owing to the size, superparamagnetic nature and saturation magnetisation.
Powering of remotely placed sensors or health monitoring devices for bridges, large buildings or aircrafts, are more difficult. Here comes the need of an energy harvesting system that can scavenge energy from the vibrations produced by the wind or vibrations from the surroundings. Piezoelectric Energy Harvesting System (PEHS) is found suitable for these applications, since it is capable of converting the mechanical vibrations or pressure variations into electrical output. Piezoelectric materials are preferred due to the attractive features like high energy density, compactness and light weight. They are most suitable for powering Structural Health Monitoring (SHM) sensors of aircraft structures, bridges, buildings etc. For optimizing the PEHS, understanding and characterization of the sources of vibration/ stress and the displacement are helpful. Introduction of interdigitated electrodes in the PEHS ensure the uniform electric field along the piezoelectric fiber material and hence, enhance the actuation. This is really good news for the electronic designers that, the energy harvested from the Interdigitated PEHS can be used for providing power to many remote applications like structural health monitoring, wireless sensors and other such requirements.
Glass samples with composition (35- X) B2O3 - (40 +X) PbO - 25 TiO2 (where X= 0, 2.5,5, 7.5 and 10 mol %) were prepared using conventional quenching technique. It was observed that as Pb0 content increases the values glass transition temperature (T-g) and crystallization temperature (T-c) decreases. The replacement of boron by a bigger Pb ion expands the network there by reducing the glass transition temperature (T-g). These glass samples were converted to glass ceramics by following two stage heat treatment schedule. The density(rho) values of glass ceramic samples are higher than those of corresponding glass samples. It was observed that there was good correlation between the density and Coefficient of Thermal Expansion (CTE) results of the glass ceramics. The XRD results in the glass ceramics revealed the formation of tetragonal lead titanate (PbTiO3) as a major crystalline phase and lead borate (PbB2O4) as minor crystalline phase. The microstructure of glass ceramic samples contains nano crystallites of lead titanate embedded in a borate glass matrix. As the content of glass former (B2O3) is reduced, the PbTiO3 crystals precipitated in glass matrix are observed to increase. The dielectric constant values of glass ceramic samples are higher than those of corresponding glass samples.
Titanium dioxide (TiO2) is a widely used transparent conducting oxide which has found many applications in solar cell devices. In the present study we have synthesized 0.75 sulphur doped TiO2 (S-TiO2) by ball milling technique and investigated their structural, topological, optical and thermal properties. The crystallization, strain and particle size have been analyzed by X-ray diffraction and reveals the formation of single phase structure corresponding to anatase phase of TiO2. AFM investigations reveal a homogeneous surface morphology. FTIR spectroscopy confirms the presence of sulphur bonding in the TiO2 crystal structure. Band gap was calculated from the absorption spectrum of S-TiO2 obtained using UV-visible spectrophotometer. The value of 3.07 eV obtained as band gap for S-TiO2 is less than that of of anatase TiO2 (3.2 eV) thus shows shifting towards the longer wavelength on sulphur doping. DTA-TGA measurements also corroborate that S-TiO2 crystallizes in the anatase phase.
Iodine doped zinc oxide (I-ZnO) thin films were synthesized by microwave assisted successive ionic layer adsorption (mSILAR) method. The structural characteristics of pure ZnO and I-ZnO thin films were carried out by powder X-ray diffraction (PXRD) analysis. The potential toxicity of pure and I-ZnO films was examined against gram-positive species like Staphylococcus aureus, Streptococcus haemolyticus and Bacillus cereus as well as gram-negative species like Escherichia coli, Klebsiella pneumonia, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella typhi, Serratia marcescens, Proteus rettigiri and Vibrio cholera by employing disc diffusion method. All the samples exhibited antibacterial activity on the tested organisms. I-ZnO produced maximum activity against both gram-positive and gram-negative species compared with pure ZnO thin film. The gram-positive species were observed to be more resistant to pure and I-ZnO thin films than gram-negative species. The studies revealed an enhancement in antibacterial activity of the I-doped thin films as compared to pure ZnO thin films.
TiO2 is one of the widely used photocatalysts for dye degradation and doping it with metals has shown to enhance its photocatalytic activity. In this work, Radio Frequency (RF) sputtering was used to fabricate robust, transparent Cu- doped TiO2 thin films on glass and silicon substrates at 300 degrees C substrate temperature. Phase analysis, surface morphology and optical studies were carried out using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and UV-vis spectroscopy respectively. The XRD pattern of TiO2 films deposited at 300 degrees C substrate temperature shows that they are in the pure anatase phase. The low copper doped TiO2 films showed crystalline nature; whereas with an increase in dopant concentration, the films tend to be amorphous. Moreover, the optical band gap of TiO2 was found to decrease from similar to 3.5 to similar to 2.5 eV respectively upon Cu doping. The application potential of the Cu- doped TiO2 thin films was evaluated by monitoring the oxidative degradation of methylene blue (MB) dye under UV irradiation as a function of time. Here we could achieve the highest degradation rate of similar to 32% for 1Cu/TiO2 films (intermediate doping) exposed to 90 min irradiation.
