Showing papers by "Shivaji University published in 2018"

Sensitivity enhancement of ammonia gas sensor based on Ag/ZnO flower and nanoellipsoids at low temperature

Abstract: High sensitivity ammonia gas sensor based on Ag/ZnO composite (SZO) nanostructures and their structural, optical, morphological and gas sensing properties were investigated. Field- emission scanning electron microscopy and high- resolution transmission electron microscopy revealed that pure ZnO flower-like nanorods transformed into nanoellipsoids upon adding of silver (Ag). Scanning transmission electron microscopy (STEM) analysis showed clear flower-like morphology of Ag/ZnO composite. STEM-mapping measurement showed that Zn, Ag and O were homogeneously distributed. The ammonia gas sensing analysis revealed that the Ag/ZnO (6 wt%) showed higher gas response compared with other content of Ag wt%. Ag/ZnO (6 wt%) exhibited the highest response of 29.5 when exposed to 100 ppm ammonia gas. Interestingly, Ag/ZnO (6 wt%) possessed good response and recovery property of 13 and 20 s at low concentration of ammonia at 10 ppm, respectively. The mechanism of gas sensing and enhanced gas response of pure ZnO and Ag/ZnO composite was discussed.

Nanoarchitectures in dye-sensitized solar cells: metal oxides, oxide perovskites and carbon-based materials

Abstract: Dye-sensitized solar cells (DSSCs) have aroused great interest and been regarded as a potential renewable energy resource among the third-generation solar cell technologies to fulfill the 21st century global energy demand. DSSCs have notable advantages such as low cost, easy fabrication process and being eco-friendly in nature. The progress of DSSCs over the last 20 years has been nearly constant due to some limitations, like poor long-term stability, narrow absorption spectrum, charge carrier transportation and collection losses and poor charge transfer mechanism for regeneration of dye molecules. The main challenge for the scientific community is to improve the performance of DSSCs by using different approaches, like finding new electrode materials with suitable nanoarchitectures, dyes in composition with promising semiconductors and metal quantum dot fluorescent dyes, and cost-effective hole transporting materials (HTMs). This review focuses on DSSC photo-physics, which includes charge separation, effective transportation, collection and recombination processes. Different nanostructured materials, including metal oxides, oxide perovskites and carbon-based composites, have been studied for photoanodes, and counter electrodes, which are crucial to achieve DSSC devices with higher efficiency and better stability.

Tuning the selectivity of NH 3 gas sensing response using Cu-doped ZnO nanostructures

Abstract: Copper-doped ZnO (CZO) nanoflower and nanoellipsoids were synthesized by hydrothermal method. Field emission electron microscopy and transmission electron microscopy revealed that the flower-like morphology of undoped ZnO transformed into nanoellipsoids upon incorporation of copper (Cu) in ZnO. Raman spectra of copper- doped ZnO showed E2L peak shift compared with undoped ZnO nanoflower which indicated enhanced oxygen or zinc vacancy in copper-doped ZnO. Low-temperature ammonia gas sensing properties based on copper-doped ZnO were systematically studied. Cu-doped ZnO (6 wt%) showed enhanced selectivity compared with other copper doping (wt%). Furthermore, the Cu-doped ZnO showed an excellent response and recovery time at a low concentration of ammonia (10 ppm). Cu-doped ZnO showed better long-term stability and reproducibility towards ammonia gas.

Metal Precursor Dependent Synthesis of NiFe2O4 Thin Films for High-Performance Flexible Symmetric Supercapacitor

Abstract: Herein, we report the chemical synthesis of NiFe2O4 thin films forming nanosheet-, nanoflower-, and nanofeather-like morphologies using NiCl2·6H2O, Ni(NO3)2·6H2O, and NiSO4·6H2O nickel salt precursors, respectively, while using the same iron salt precursor. A nanostructure formation mechanism is proposed in detail using coordination chemistry theory. Interestingly, nanostructures of NiFe2O4 nanosheets revealed a maximum surface area of 47 m2 g–1, which was higher than those of nanoflowers and nanofeathers (25 and 11 m2 g–1). Similarly, the supercapacitive properties of the individual NiFe2O4 nanosheet-based electrode demonstrated maximum specific capacitance of 1139 F g–1, which is found to be better than that of NiFe2O4 nanoflowers (677 F g–1) and nanofeathers (435 F g–1) in 6 M KOH electrolyte. Furthermore, the symmetric device fabricated using NiFe2O4 nanosheet electrodes and PVA-KOH solid gel electrolyte shows higher specific capacitance of 236 F g–1 with 98% retention after 7000 cycles and higher spe...

Biosynthesis of ZrO 2 nanoparticles from Ficus benghalensis leaf extract for photocatalytic activity

Abstract: The biosynthesis of metal oxide nanoparticles (NPs) using plant extract is green, rapid, attractive and cost-effective approach. In the present study, we are reporting biosynthesis of ZrO2 NPs as an efficient photocatalyst by using Ficus benghalensis (F.B.) leaf extract as a capping agent for the first time. To determine its optical, structural and morphological properties, the obtained ZrO2 NPs were characterized by using UV–Vis, DRS, XRD, FT-IR, HR-TEM, FT-Raman and BET-surface area. XRD pattern confirms that biosynthesized ZrO2 NPs are crystalline in nature with monoclinic and tetragonal structure. TEM images show that the obtained ZrO2 NPs has spherical morphology with 15 nm in size which is good agreement with XRD results. A decrease in the band gap of bulk ZrO2 from 5.3 to 4.9 eV is observed due to the quantum size effect. The as-synthesized ZrO2 NPs have high specific surface area of 88 m2/g was obtained by BET analysis. The photocatalytic efficiency of ZrO2 NPs is evaluated for the photodegradation of methylene blue and methyl orange dyes as the target pollutants under UV light irradiation. The different parameters like catalyst loading amount and pH have also been studied. It is observed that photodegradation of methylene blue and methyl orange up to 91 and 69% within 240 min by using ZrO2 catalyst. Moreover, this green synthesis process provides a valuable alternative to orthodox multistep processes for the preparation of ZrO2 NPs.

Symmetric supercapacitor: Sulphurized graphene and ionic liquid

Abstract: Symmetric supercapacitor is advanced over simple supercapacitor device due to their stability over a large potential window and high energy density. Graphene is a desired candidate for supercapacitor application since it has a high surface area, good electronic conductivity and high electro chemical stability. There is a pragmatic use of ionic liquid electrolyte for supercapacitor due to its stability over a large potential window, good ionic conductivity and eco-friendly nature. For high performance supercapacitor, the interaction between ionic liquid electrolyte and graphene are crucial for better charge transportation. In respect of this, a three-dimensional (3D) nanoporous honeycomb shaped sulfur embedded graphene (S-graphene) has been synthesized by simple chemical method. Here, the fabrication of high performance symmetric supercapacitor is done by using S-graphene as an electrode and [BMIM-PF6] as an electrolyte. The particular architecture of S-graphene benefited to reduce the ion diffusion resistance, providing the large surface area for charge transportation and efficient charge storage. The S-graphene and ionic liquid-based symmetric supercapacitor device showed the large potential window of 3.2 V with high energy density 124 Wh kg−1 at 0.2 A g−1 constant applied current density. Furthermore, this device shows good cycling performance (stability) with a capacitive retention of 95% over 20,000 cycles at a higher current density of 2 A g−1.

Structural and Optical Properties of Nanocrystalline TiO2 with Multiwalled Carbon Nanotubes and Its Photovoltaic Studies Using Ru(II) Sensitizers.

Abstract: In this study, the in situ sol–gel method has been deployed to prepare the titanium dioxide/multiwalled carbon nanotubes (TiO2/MWCNTs) nanocomposite (NCs) powders with varying content of MWCNTs (0....

Collagen and collagenolytic proteases: A review

Abstract: Despite of having enormous applications, the use of collagen is predominantly limited because of its high cost. Most of the mammalian sources used for its production have major drawbacks. However, compared to mammalian sources, fish waste can be utilized as cost-effective alternative to produce collagen. Around 75% part of fish is discarded as a waste which contains high concentration of collagen. Fish collagen has multiple advantages over mammalian collagen and hence can be a promising alternative for it. Proteases with collagenolytic activities are also of immense importance because of their industrial as well as biological applications. Microbial collagenolytic proteases are gaining huge attention in these days because of their lower requirements and higher productivity. They perform important role in global recycling of collagenous waste. This review gives recent information on collagen and collagenolytic proteases. Here, utilization of seafood by-products is discussed to recover the collagen and its recent applications are summarized. In addition to this, current review also highlights the recent status of collagenases in which present strategies and new technology used for the isolation, screening, production optimization, purification, characterization and applications of microbial collagenases are discussed.

A highly efficient visible-light responsive sprayed WO3/FTO photoanode for photoelectrocatalytic degradation of brilliant blue

Abstract: In present article, WO3 thin films have been successfully synthesized by chemical spray pyrolysis approach. The effect of spraying quantity of solution onto the photoelectrochemical (PEC), structural, morphological, and optical properties has been studied. Film prepared at 40 ml solution quantity shows the excellent photoelectrochemical performance (Isc= 0.69 mA/cm2 and Voc = 0.64 V) in 0.05 M concentrated H2SO4 electrolyte. X-ray diffraction studies reveal that the synthesized WO3 thin films are polycrystalline with monoclinic crystal structure. The chief vibrational modes of the WO3 sample, located at 712.64 and 804.28 cm−1 corresponding to the stretching and the bending of O W O bond respectively and are consistent with a monoclinic structure. The estimated band gap energy of WO3 thin films varies from 2.37 to 2.45 eV with respect to quantities of spraying solution and it exhibits absorption in visible region. Film shows a maximum specific surface area of 31.63 m2/g. Photoelectrocatalytic degradation of brilliant blue dye in aqueous solutions is studied. The end result shows that the degradation percentage of brilliant blue using WO3 photoelectrode has reached 92% under visible light illumination after 240 min. The enhancement in photoelectrocatalytic activity of optimized 40 ml WO3 sample is mainly due to the suppressed the recombination rate of photogenerated electron–hole pairs. This study provides an effective WO3 photoelectrode for removing of organic pollutants present in the water.

Photoelectrocatalytic degradation of sugarcane factory wastewater using WO3/ZnO thin films

Abstract: In the present work, layered WO3/ZnO thin films have been prepared by simple chemical spray pyrolysis method. As prepared films are characterized by photoelectrochemical (PEC) solar cell, X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM), Brunauer–Emmer–Teller (BET) and energy dispersive X-ray spectroscopy techniques. XRD analysis reveals the formation of hexagonal and monoclinic phases of ZnO and WO3 respectively. Raman analysis confirms the formation of layered WO3/ZnO thin films. FE-SEM images demonstrate that the surface morphology of layered WO3/ZnO consists of nano balls like morphology. The specific surface area of the layered WO3/ZnO thin film is found to be 65.12 m2 g−1. The photoelectrocatalytic degradation properties of layered WO3/ZnO thin films were investigated by studying degradation of sugarcane factory wastewater. The end result shows that the degradation percentage of sugarcane factory wastewater using layered WO3/ZnO photo electrode has reached 94.44% after 100 min. under sunlight illumination.

Biosynthesis of SnO2 nanoparticles by aqueous leaf extract of Calotropis gigantea for photocatalytic applications

Abstract: Here we developed biogenic route for the synthesis of SnO2 NPs by using aqueous leaf extract of Calotropis gigantea which acts as reducing and stabilizing agent. The biosynthesized SnO2 NPs were characterized by different characterization techniques such as UV–visible diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis and high resolution transmission electron microscope. XRD pattern shows tetragonal structure of SnO2 NPs with 35 nm size. The FT-IR spectra of aqueous leaf extract shows the presence of hydroxyl group, aldehydes, amines and aromatic rings which are responsible for biochemical transformation. The FE-SEM analysis suggests mixed morphology with slight agglomeration. DRS absorption spectrum indicates the band gap is about 3.1 eV. The photocatalytic activity of the synthesized SnO2 NPs checked for the degradation of Methyl Orange and found up to 80% degradation within 3 h under UV–visible light.