Dimple Shah

Study of Photocatalytic activity and properties of Transition metal ions doped Nanocrystalline TiO2 prepared by Sol-Gel Method

T advances have been achieved over the past decade in the area of design and synthesis of novel conjugated polymers for bulk heterojunction (BHJ) solar cells and light emitting diodes (LEDs). With ingenious use of variety of synthetic techniques, researchers have synthesised copolymers with optimized physical properties. For instance, an organic photovoltaic (OPV) material showing record-breaking power conversion efficiency (PCE) of ca. 10% has been reported recently. In the design of semiconducting copolymers, the donor-acceptor (DA) approach has been found to afford low band gap (LBG) copolymers with broad absorption to efficiently harvest solar energy. Here we report the synthesis of two novel LBG copolymers (PFDEBT and PFDES) and studies of their photo-physical and electrochemical properties, for prospective use in organic electronics. PFDEBT with benzothiadiazole acceptor moiety demonstrated bathochromic shift of absorption from 578 nm in solution to 591 nm in the solid state with an optical band gap of 1.69 eV, while PFDES containing dibenzothiopheneS,S-dioxide unit showed absorption at 489 and 494 nm in both the liquid and solid states respectively with an optical band gap of 2.25 eV. Both polymers are highly emissive materials; with the former emitting in the red region of the emission spectrum attaining emission λmax of 709 nm and 28% photoluminescence quantum yield (PL Φ) in solution, while the later emits in the green region with an emission λ max of 517 nm and 55% PL Φ. The HOMO energy levels of the polymers estimated from cyclic voltammetry analysis are -4.9 and -5.1 respectively. Preliminary studies of BHJ solar devices ofthe blend of these copolymers with PC60BM showed PCE of 1.45% and 1.1% for PFDEBT and PFDES respectively for non-optimized devices.Transition metal (Mn, Fe, Co,) doped TiO2 nanoparticles were synthesized by the sol-gel method. All the prepared samples were calcined at different temperature like 200°C to 800°C and characterized by X-ray diffraction (XRD), Energy dispersive X-ray (EDX) analysis, The studies revealed that transition metal (TM) doped nanoparticles have smaller crystalline size and higher surface area than pure TiO2. Dopant ions in the TiO2 structure caused significant absorption shift into the visible region. The results of photodegradation of Formaldehyde in aqueous medium under UV light showed that Photocatalytic activity of TiO2 nanoparticles was significantly enhanced by the presence of some transition metal ions. Chemical Oxygen Demand (COD) of formaldehyde solutions were done at regular intervals gave a good idea about mineralization of formaldehyde.S of ferromagnetic shape memory alloys is of interest, because of their smart behaviour and these can be good candidates for the sensors and actuators applications. NiMnGa is considered a prototype of these materials, but being brittle practically using it is difficult. We have doped boron because it stabilizes the martensite also to enhance its ductility and studied their magnetic and transport properties. The thin film samples were deposited at a constant r. f. power of 60 W for 60 min duration, on glass substrates kept at room temperature at different partial pressures 0.06, 0.01, 0.2 mb. The films were subsequently annealed at 773 K for 30 min and were characterized by using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) and magnetization measurements. From the room temperature, XRD and SEM, EDAX of the thin films, the structure and composition of these samples were found to be preparation conditions dependant. From the SEM photographs, the thin films were found to be possessing fine grained microstructure on the glass and, grains were large in size at 0.06 mb partial pressure. The structural and magnetic transformation temperatures were determined using the magnetic and transport measurements for both bulk and thin film samples and the properties were compared. The results on such studies were presented in this paper.Si-Ge solid solutions (bulk polyand mono-crystalline samples, thin films) are characterized by high perspectives for application in semiconductor devices, in particular, optoelectronics and microelectronics. From this point of view, complex studying of structural state of the defects and structural-sensitive physical properties of Si-Ge solid solutions depending on the contents of Si and Ge components is very important. Present work deals with the investigations of microstructure, microhardness, internal friction and shear modulus of Si1-xGex(x≤0,02) bulk monocrystals conducted at room temperature. Si-Ge bulk crystals were obtained by Czochralski method in [111] crystallographic direction. Investigated monocrystalline Si-Ge samples are characterized by p-type conductivity and carriers’ concentration 510-1.10cm. Microhardness was studied on Dynamic Ultra Micro hardness Tester DUH-201S with Berkovich indenter. Investigate samples are characterized with 0,5x0,5x(10-15)mm3 sizes, oriented along [111] direction at torsion oscillations ≈1Hz, multistage changing of internal friction and shear modulus has been revealed in an interval of strain amplitude of 10-5-5.10-3. Critical values of strain amplitude have been determined at which hysteretic changes of inelastic characteristics and microplasticity are observed. The critical strain amplitude and elasticity limit values are also determined. Dynamic mechanical characteristics decreasing trend is shown with increasing Ge content in Si-Ge solid solutions. Observed changes are discussed from the point of view of interaction of various dislocations with point defects and their complexes in a real structure of Si-Ge solid solutions. Keywords—Internal friction, microhardness, relaxation processes, shear modulus, Si-Ge.(Deputy Director, Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Chinese Academy of Sciences, China) Nanotechnology is to utilize matter smaller than 100 nanometers and takes advantages of properties that are only presented at this nano level. Recent advances in nanotechnology have provided various new tools for biomedical research and clinical applications. Nanopharmaceutics is one of the disciplines that will benefit from this technology the most. Nanomaterials, with their unique size-dependent physical and chemical properties, have showed promising advantages as drug and gene delivery vehicles, ultra-sensitive and controllable intracellular payload release, and precisely silence of targeted genes. However, to develop nucleic acids、peptides or chemicals-based pharmaceuticals along with these promising progresses, the high transfection and low toxicology of engineered nanomaterials as carriers exist as a potential barrier and has caught much attention. Therefore, Designing nanopharmaceutics for effectively expected bioeffects without significant toxicity has become an important issue for clinical application of novel nanomaterials. Nanotechnology will have a revolutionary impact on clinically based therapy due to the exceptional characteristics of nanopharmaceutics. It is critical to screen and identify novel nanopharmaceutics with an exclusive biological function in vitro and in vivo. Recently, innovative nanomaterials for pharmaceutics have been discovered as a potential competent drug with negligible cytotoxicity in tissue culture and without detectable side effects in vivo. Nanostructures can specifically inhibit the growth of solid malignant tumors in nude mice by direct injection into the neoplasm. The mechanism of how these nanostructures seeking for and docking into tumor after i.v. injection in patient is unknown and still needs further study. This finding may inspire researchers to develop a new generation of nanomaterials with inventive non-traditional approach for disease treatement. The development of nanomaterials will allow for more precise efficiently targeted treatment with less toxicity of clinical therapy.T possibility of maintaining of quantum coherence of semiconductor quantum dots is one of the most important desires in quantum optics, quantum devices, and particularly quantum computers. The existing attempts include using very low temperatures to suppress the large polarization dephasing rates of the quantum dots and/or using ultrashort optical pulses. In this contribution, we discuss the prospect of generation and preservation of quantum coherence effects in hybrid quantum dotmetallic nanoparticle systems at elevated temperatures. It will be shown, via theoretical means, that even when the decoherence times of the quantum dots are of the order of several hundreds of femtoseconds, as observed at room temperature, the molecular resonances of such hybrid systems formed via coherent exciton-plasmon coupling can remain quite distinct and observable. The quantum optical properties of the quantum dots in such hybrid systems, including the possibility of generation of ultra-narrow gain features, will be discussed.R studies have shown the utility of copolymer sorbent materials based on cross-linked polysaccharide scaffolds. Polysaccharide scaffolds represent a versatile scaffold for the design of sorbent materials because of their interesting hostguest chemistry. Synthetic engineering through chemical cross-linking offers a modular strategy for copolymer sorbent materials with tunable structural and physiochemical properties. In this presentation, an overview of recent research concerning the sorption properties of synthetically engineered sorbent materials and waterborne contaminants will be reviewed. The results of this research are anticipated to contribute favourably to technology concerning sorptive based removal of water borne contaminants and chemical separations.T controlled design and synthesis of iron oxide nanocrystals have recently attracted much interest for both basic scientific research and practical technological applications. Hence, formulating simple and novel surfactant-free methods to synthesize different Fe3O4 particles with different magnetic properties is important. In this study, we investigate a simple hydrothermal method to synthesize magnetic and nonmagnetic Fe3O4 nanocrystals. All magnetic and non-magnetic iron oxide crystals were characterized by scanning electron microscopy (SEM), UV-vis, and X-ray diffraction.I the present studies composite films of polythiophene/ZnO (PTh/ZnO) has been prepared on ITO surface. The electrochemical deposition has been carried out using galvanostatic mode in electrolytic cell having single compartment with three electrodes namely ITO, platinum sheet and calomel as working, counter and reference electrode respectively. ZnO nanoparticles were synthesized by solvothermal method. In a typical procedure KOH solution was added dropwise to zinc acetate dihydrate in methanol solution under stirring. The solution was heated to 600C for 1.5 h for precipitation of ZnO nanoparticles. The TEM study revealed that the average particle size is ~6 nm with spherical shape particles. The crystallite size calculated from XRD data is found to be ~6.2 nm with hexagonal wurtzite structure. The composite film growth was carried out in a solution containing thiophene monomer, tetrabuytlammonium tetrafluoroborate as oxidant and ZnO nanoparticles all present together in nitrobenzene solvent. The shift in FTIR band positions corresponding to PTh indicates the interaction of PTh chain with ZnO nanoparticles. Presence of globulars in SEM image confirms presence of ZnO nanoparticles in the film. Using composite film based working electrode in cyclic voltammogram a redox pair at E1/2=-0.68V in citric acid solution in the potential range 0 and -1.2 V at scan rate of 50mVs -1 with detection level of 3 mM. Almost linear plot was observed for square root of scan rate versus current density indicating diffusion controlled process. The study shows that the composite film has a potential to act as a taste sensor for citric acid.L ion batteries are under intense, worldwide research for improvement in durability and energy density for a wide range of applications, including electric and hybrid electric vehicles. Clear understanding of the battery capacity fading can lead to precise cycle-life prediction of batteries. For advanced lithium ion batteries with high energy and power performance, different aspects of lithium ion batteries such as novel electrode materials, improved electrode designs, Stabilizing electrolyte additives etc. are under high attention. When lithium is inserted in either the positive or negative electrode, the electrode material experiences mechanical stresses. Diffusioninduced stresses (DISs) can therefore cause the nucleation and growth of cracks leading to mechanical degradation of electrodes. We develop several mathematical models to study the behavior of diffusion induces stresses and effects of electrode shape, size, concentration dependent material properties, pre-existing cracks, phase transformations, operating conditions etc. on the diffusion induced stresses. Instability of commonly used electrolytes at the operating potentials leads to chemical degradation at the electrode surface. We study coupled chemical-mechanical degradation of electrode materials to understand the capacity fading of the battery with cycling. Chemical degradation can be decreased using electrolyte additives. We study the effect of electrolyte additive VC on parasitic reactions in Graphite/Lithium Nickel Manganese Cobalt Oxide (NMC) cells. Mechanical degradation can be avoided by use of novel electrode material such as liquid metal electrodes. We demonstrate that liquid metal electrodes can act as self-healing electrodes.

Substrate temperature effect on structural and optical properties of Bi2Te3 thin films

Structural and optical properties of Bi2Te3 thin films, thermally evaporated on well-cleaned glass substrates at different substrate temperatures, are reported here. X-ray diffraction was carried out for the structural characterization. XRD patterns of the films exhibit preferential orientation along the [0 1 5] direction for the films deposited at all the substrate temperatures together with other supported planes [2 0 5] & [1 1 0]. All other deposition conditions like thickness, deposition rate and pressure were maintained same throughout the experiment. X-ray diffraction lines confirm that the grown films are polycrystalline in nature with hexagonal crystal structure. The effect of substrate temperature on lattice constants, grain size, micro strain, number of crystallites and dislocation density have been investigated and reported in this paper. Also the substrate temperature effect on the optical property has been also investigated using the FTIR spectroscopy.

Structural, optical, and photocatalytic properties of ZnS/α-Fe2O3 core shell nano particles

Core shell ZnS/α-Fe2O3 nanoparticles were produced by the two-step method. In the first step uniform α-Fe2O3 particles were synthesized by hydrolysis of ferric chloride at 80°C. In the second step ZnS particles were added to α-Fe2O3 particles via hydrothermal rout at ca 90°C. The α-Fe2O3 and ZnS phases were identified by XRD and energy dispersive X-ray analysis (EDX). Crystal structure and morphology were studied by high resolution TEM. Photoreactivity of ZnS/α-Fe2O3 core shell nanoparticles was quantified by degradation of formaldehyde under UV irradiation.

Structural and optical properties of copper zinc tin sulphide (CZTS) material synthesized using binary sulphide precursors

Copper Zinc Tin Sulphide (CZTS) is one of the most promising materials for absorber layer in thin film solar cells. However, the synthesis of CZTS requires careful optimization as it is a quaternary material with a high probability of formation of secondary phases during the synthesis. Here we report the synthesis of CZTS from its binary constituents i.e. CuS, SnS and ZnS at 1030 K in laboratory. The effects of excess sulphur in starting precursors on the chemical compositions of the compound are investigated. Structural and optical properties of synthesized compound are studied in context of its application as absorber material in thin film solar cells.

Structural, Optical and Magnetic Properties of Nanocrystalline Cobalt Doped TiO2 Prepared by Sol-Gel Route

Nanocrystalline Cobalt-doped TiO2 was prepared by Sol-Gel technique, followed by freeze-drying treatment at-30°C temperature for 12hrs. The obtained Gel was thermally treated at 200,400,600, 800°C. 1%, 2% and 4% Cobalt doped TiO2 nanopowder has been prepared X-ray Powder Diffraction (XRD), Scanning Electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), was used to study its structural properties. The XRD pattern shows the coexistence of anatase phase and rutile phase. Thermal gravimetric analysis shows Cobalt concentration affects thermal decomposition. UV-Vis Spectroscopy, Photo luminescence (PL), was used to study its Optical properties. Optical Bandgap were calculated with the incorporation of different concentration of cobalt. UV-Visible spectroscopy show variation in band gap for the sample treated at different temperature for same concentration. All Cobalt doped TiO2 nanostructures shows an appearance of Red shift relative to the bulk TiO2. The determination of magnetic properties was also carried out by Vibrating Sample Magnetometer.

Synthesis, Structural, Optical, and Magnetic Properties of Fe Doped TiO2 along with Different Concentration

Nanocrystalline Fe-doped TiO2 was prepared by Sol-Gel technique, which was followed by freeze at-30°C temperature for 12hrs. The obtained Gel was thermally treated at 200,400,600 and 800°C. X-ray Powder Diffraction (XRD), Scanning Electron microscopy (SEM), UV-Vis Spectroscopy, Photo luminescence (PL) and EDAX was used to study its Structural and Optical properties. All Fe-doped TiO2 nanostructures show an appearance of Red shift relative to the bulk TiO2. The XRD pattern show the coexistence of major anatase phase and minor brookite phase for samples treated up to 600°C. Whereas at 800°C rutile is the only phase observed. All Fe doped TiO2 nanostructures show an appearance of Red shift relative to bulk undoped TiO2. The magnetic property by Gouy Balance of Fe doped TiO2 exhibit Peramagnetism at room temperature.

Ac and Dielectric Behavior of Sb2Te3 Single Crystal

Sb2Te3 single crystals have been grown by Travelling Heater Method. EDAX was carried out for confirmation of constituent elements. By the measurements of Dielectric constant (k) and dielectric loss (tanδ), we are able to understand various polarization mechanism in the grown crystals such as space charge polarization, orientational polarization of dipoles and atomic polarization of lattice. AC conduction and Dielectric studies were performed at various frequencies ranging from 100 Hz–1 MHz and temperature 303 K–503 K. From, the AC conduction studies, it is confirmed that the mechanism responsible for the conduction process is hopping. The variations of the dielectric constant (k) and loss (tan δ) as a function of frequency at different temperature are observed and the results were discussed. The activation energy has been evaluated from the dependence of temperature on conductance. TCC and TCP are also calculated from the temperature dependence of capacitance