Effect of hydrothermal growth temperature on structural and optical properties of TiO2 nanoparticles

TiO₂ nanoparticles have been prepared by hydrothermal method at different temperatures. The X-ray diffraction results showed that anatase TiO₂ nanoparticles with grain size in the range of 7–27 nm has been obtained. HRTEM images show the formation of TiO₂ nanoparticles with grain size ranging from 7 to 26 nm. The Raman spectra exhibited peaks corresponding to the anatase phase of TiO₂. Optical absorption studies reveal that the absorption edge shifts towards longer wavelength (red shift) with increasing hydrothermal temperature.     

Dye-sensitized ZnO nanorod based photoelectrochemical solar cells with natural dyes extracted from Ixora coccinea,Mulberry and Beetroot

ZnO nanorods have been prepared on indium tin oxide (ITO) glass substrates coated with sol–gel based ZnO seed layer through chemical method. Natural dyes (Ixora coccinea, Mulberry and Beetroot) have been used for the fabrication of dye sensitized solar cells. The surface morphology studied using scanning electron microscope shows that the vertically aligned ZnO nanorods are of hexagonal shape. The solar cell efficiency has been calculated and is found to be 0.33, 0.41 and 0.28% for Ixora coccinea, Mulberry and Beetroot extract dye sensitized solar cells.     

Enhanced photovoltaic performance of quantum dot sensitized solar cells with Ag-doped TiO2 nanocrystalline thin films

Ag-doped titanium dioxide (TiO₂) nanocrystalline thin films have been prepared by the sol–gel dip coating method and used as photoanode to fabricate quantum dot sensitized solar cells. The X-ray diffraction studies reveal the formation of anatase phase without any impurity phase. The surface morphology studied using scanning electron microscope shows uniform distribution of particles. The optical band gap was found to be 3.5 and 3.4 eV for CdS quantum dot sensitized TiO₂ and CdS quantum dot sensitized Ag-doped TiO₂ thin film respectively. The Ag-doped TiO₂ based solar cell exhibited a power conversion efficiency of 1.48 % which is higher than that of TiO₂ (0.9 %).     

Strong quantum confinement effect in nanocrystalline CdS

CdS quantum dots have been prepared by chemical method. The X-ray diffraction results indicated the formation of CdS nanoparticles with hexagonal phase and grain size 2.5 nm. The HRTEM analysis reveals the formation of CdS quantum dots with an average grain size of ~2.5 nm. The X-ray photoelectron spectroscopy spectra exhibit the 3d _5/2 and 3d _3/2 peaks corresponding to cadmium and the S2p _3/2 peak corresponding to sulphur. Optical studies by UV–vis spectroscopy show a blue shifted absorption at 471 nm because of the quantum confined excitonic absorption. The photoluminescence spectra of CdS exhibited a broad green emission band centred at around 494 nm.     

Natural dye (cyanidin 3-O-glucoside) sensitized nanocrystalline TiO2 solar cell fabricated using liquid electrolyte/quasi-solid-state polymer electrolyte

TiO₂ dye-sensitized solar cells (DSSCs) have been fabricated using TiO₂ photoelectrodes sensitized using the extracts of Delonix regia (May flower, locally called Vakai) and Eugenia Jambolana (Indian blackberry, locally called Naval) as natural sensitizers and their characteristics have been studied. Among them Eugenia Jambolana gave the best photosensitization effect and presents the prospect to be used as an environment-friendly, low-cost alternative system. The extracts having anthocyanin pigment (cyanidin 3-O-glucoside), which have carboxylic groups in the molecule can attach effectively to the surface of TiO₂ film. The solar cell constructed using the Eugenia Jambolana sensitized TiO₂ photo-electrode exhibited a short-circuit photocurrent of 1.49 mA and a power conversion efficiency of 0.5%.     

Studies on structural,morphological, electrical and electrochemical properties of activated carbon prepared from sugarcane bagasse

Activated carbon composite was prepared from sugarcane bagasse. The X-ray diffraction revealed the evolution of crystallites of carbon and silica during activation at higher temperature. FTIR spectrum shows the presence of functional groups and silica in the carbon composite. The morphology of the carbon sample was determined by SEM. The surface area, pore volume and pore size distribution of carbon composites were measured. The dc conductivity was determined and conductivity at room temperature was found to increase from 10.22 × 10^?3 to 25.131 × 10^?3 S cm^?1. The samples show good electrochemical property and the specific capacitance in the range of 92–340 F g^?1.     

Influence of the Cd/S Molar Ratio on the Optical and Structural Properties of Nanocrystalline CdS Thin Films

Nanocrystalline CdS thin films have been deposited using precursors with different thiourea concentrationonto glass substrates by sol-gel spin coating method.The crystalline nature of the films has been observedto be strongly dependent on thiourea concentration and annealing temperature.The CdS films are found tobe nanocrystalline in nature with hexagonal structure.The grain size is found to be in the range of 7.6 to11.5 nm depending on the thiourea concentration and annealing temperature.The high resolution transmissionelectron microscopy (HRTEM) results of the CdS films prepared using cadmium to thiourea molar ratio of0.3:0.3 indicate the formation of nanocrystalline CdS with grain size of 5 nm.Fourier transform infrared (FTIR)analysis shows the absorption bands corresponding to Cd and S.The optical study carried out to determinethe band gap of the nanostructured CdS thin films shows a strong blue shift.The band gap energy has beenobserved to lie in the range of 3.97 to 3.62 eV following closely the quantum confinement dependence ofenergy on crystallite radius.The dependence of band gap of the CdS films on the annealing temperature andthiourea concentration has also been studied.The photoluminescence (PL) spectra display two main emissionpeaks corresponding to the blue and green emissions of CdS.     

Immobilization of ZnO on Chitosan-Neem seed composite for enhanced thermal and antibacterial activity

Natural and inorganic materials of Chitosan-Zinc oxide-Neem seed (CS-ZnO-NS) hybrid composite were synthesized by chemical precipitation method. The obtained CS-ZnO-NS hybrid composites were characterized for functional group confirmation by Fourier transform infrared spectroscopy and UV–Visible spectroscopy. The ZnO particles connected to biopolymers exhibited small grains and rod, bullet like structure confirmed by scanning electron microscopy and transmission electron microscopy analysis. The size of the prepared CS-ZnO-NS hybrid composite was found to be 20–80?nm. The crystalline behaviors were determined by X-ray diffraction analysis. The surface area of the prepared hybrid composite was determined using BET analysis. The elemental composition was analyzed by energy dispersive X-ray spectroscopy and thermal behaviors by thermo gravimetric analysis. The obtained result shows that zinc oxide was well able to incorporate into chitosan-neem seed composite which enhances the thermal stability. Further, the antibacterial activity evaluated by agar well diffusion method against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria exhibits higher inhibition effect because of ZnO particles presence in the chitosan-neem seed. Hence the CS-ZnO-NS is a promising material for biomedical applications.     

CuS@β-SnS nanocomposite electrocatalysts for efficient electrochemical water oxidation

Oxygen evolution reaction (OER) is an important key factor in favor of spotless energy production and storage. High cost and toxic elements can threaten the energy production. Only way to tackle the problem is that by utilizing the cost effective, earth-abundant and non toxic elements. In the present study, CuS, β-SnS and CuS@β-SnS nanocomposite were synthesized via co-precipitation process. X-Ray diffraction (XRD) spectra identify crystalline phases of synthesized samples. Raman spectra confirm nanocomposite formation and determine vibrational modes of molecules. Photoluminescence (PL) spectra revealed optical and electronic properties of synthesized materials. Flower-like morphology of CuS@β-SnS nanocomposite was analyzed by scanning electron microscopy (SEM) images. In addition, CuS@β-SnS nanocomposite exhibits 1111 F/g specific capacitance and 224 mV low overpotential. Further study revealed that CuS@β-SnS nanocomposite electrocatalyst displays good stability and excellent OER activity even over a prolong time. Remarkably, CuS@β-SnS nanocomposite revealed a low price water oxidation electrocatalyst and it builds a new pathway for practical water splitting applications.