Showing papers by "Shivaji University published in 2017"

Sensitive and selective NO2 gas sensor based on WO3 nanoplates

Abstract: Gas sensors based on a chemiresistive metal oxide semiconductor are widely used including nitrogen dioxide (NO 2 ) at a moderate temperature. In this work efforts are taken to fabricate NO 2 gas sensor using thin films of tungsten oxide (WO 3 ) grown directly on to a soda-lime glass substrate without assistance of any seed layer by a simple and a facile hydrothermal technique. As per our knowledge, the deposition of nanostructured WO 3 thin films without assistance of any seed layer on the glass substrate was rarely reported. The WO 3 thin film samples were synthesized at various deposition times ranging from 3 h to 7 h and were characterized by X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, UV–vis spectroscopy and Brunauer-Emmett-Teller techniques. The surface morphological and structural characterization showed the two dimensional (2D) nanoplate-like structure of as synthesized WO 3 thin films with plate thickness ranging from 90 to 150 nm and had an orthorhombic structure, respectively. Moreover, the 2D nanoplates of WO 3 exhibited a gas response ∼10 for 5 ppm for toxic NO 2 gas at relatively low operating temperature. The new synthesis route and sensing behavior of as synthesized WO 3 nanoplates revealed a promising candidate for the fabrication of the cost effective gas sensors.

Fabrication of nanostructured ZnO thin films based NO2 gas sensor via SILAR technique

Abstract: Zinc oxide (ZnO) thin films have been widely used as an effective gas sensor element. In the present study, nanostructured thin films of ZnO were prepared by using the simplistic and economical successive ion layer adsorption and reaction (SILAR) technique. The effects of SILAR cycles on the structural, optical, surface morphological and electrical properties of nanostructured ZnO thin films were investigated. Characterization techniques such as XRD, UV-vis, PL, FESEM, and Hall measurement were utilized to study the physical and chemical properties of the synthesized films. XRD confirms the formation of hexagonal phase structural ZnO thin films. FE-SEM analysis reveals the formation of well-dispersed ZnO nanoparticles having sizes of ∼18–40 nm. The SILAR cycles play a key role in the synthesis of nanostructured ZnO thin films and it is found that, with increasing SILAR cycles, the grain size continues increasing. Optical studies confirm the presence of oxygen vacancies in synthesized ZnO thin films. Finally, the ZnO thin films were exposed to NO 2 gas with a concentration of 100 ppb–200 ppm and the resulting resistance transient was recorded. The nanostructured ZnO thin films synthesized at 30 SILAR cycles displays an enhancement of gas sensing performance and exhibit significantly higher responses (∼5% per ppm). Moreover, our ZnO thin-film-based gas sensor is sensitive to very low concentrations of dangerous NO 2 (100 ppb). The sensitive gas sensor used to trace level NO 2 detection, synthesized via simple SILAR route proves the novelty of our work. The present report provides a new direction in fabricating nanostructured ZnO thin films for low-cost and efficient gas sensing applications.

Green synthesis of ZnO nanoparticles by using Calotropis procera leaves for the photodegradation of methyl orange

Abstract: A facile, innovative and inexpensive green route has been demonstrated for the formation of ZnO nanoparticles by biogenic method using aqueous leaf extract of Calotropis procera which acts as a reducing and stabilizing agent. The as prepared ZnO nanoparticles were characterized by a host of different techniques such as X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FT-IR). The XRD pattern confesses that ZnO nanoparticles associate to hexagonal wurtzite structure. The DRS absorption spectrum shows an absorption edge at 397 nm corresponds to the ground excitonic peak of ZnO nanoparticles and the band gap is found to be 3.1 eV. The FT-IR spectra indicate the presence of hydroxyl groups, aldehydes, amines, ketones, and carboxylic acids which are responsible for biochemical reaction. TEM images shows that the particles of ZnO have spherical shape with size ranging from 15 to 25 nm. ZnO nanoparticles were subjected to photocatalytic application for the degradation of methyl orange under UV light. The photodegradation efficiency of MO was found to be 81% within 100 min under UV light, such an excellent activity is obtained by biogenic ZnO NPs.

Mucuna pruriens Protects against MPTP Intoxicated Neuroinflammation in Parkinson's Disease through NF-κB/pAKT Signaling Pathways.

Abstract: Till date, drugs that have been used to manage Parkinson's disease (PD) have only shown symptomatic relief with several adverse effects besides their inability to prevent neurodegeneration. Neuroinflammation plays an important role in the advancement of PD and can be targeted for its effective treatment. Researchers have suggested that herbal plants exhibiting the anti-inflammatory and anti-oxidant properties are therefore beneficial to human health. Conventionally, Mucuna pruriens (Mp) seeds are used for maintaining male virility in India. Reportedly, Mp is used as a rejuvenator drug having neuroprotective property. Our study aimed to investigate effects of aqueous extract of Mp (100 mg/kgbwt) on neuroinflammation, orally administered to mice intoxicated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as well as the molecular mechanism involved in the progression of PD. In this study, we have observed significant behavioral abnormalities beside decreased antioxidant defense in MPTP intoxicated mice. We have also observed significant increase in inflammatory parameters like Glial Fibrillary Acidic Protein, Inducible Nitric Oxide Synthase, Intercellular Cell Adhesion Molecule, and Tumor Necrosis Factor alpha in substantia nigra pars compacta (SNpc) of parkinsonian mice, while Mp treatment has notably reduced these inflammatory parameters. Mp also inhibited the MPTP induced activation of NF-κB and promoted pAkt1 activity which further prevented the apoptosis of the dopaminergic neurons. Moreover, Mp exhibited significant antioxidant defense by inhibiting the lipid peroxidation and nitrite level, and by improving catalase activity and enhancing GSH level in nigrostriatal region of mouse brain. Mp also recovered the behavioral abnormalities in MPTP treated mice. Additionally, Mp treatment considerably increased the immunoreactivity of Tyrosine Hydroxylase and Dopamine Transporter in SNpc of parkinsonian mice. Our high performance liquid chromatography analysis of the Mp seed extract have shown L-DOPA, gallic acid, phytic acid, quercetin, and catechin equivalents as the major components which might cause neuroprotection in PD mice. Our result suggested that Mp extract treatment containing L-DOPA and a mixture of rich novel phytochemicals significantly alleviates the MPTP induced neurotoxicity by NF-κB and pAkt pathway. The findings observed thereby indicate that Mp extract have suggestively ameliorated MPTP induced neuroinflammation, restored the biochemical and behavioral abnormalities in PD mouse and thus provided a scientific basis for its traditional claim.

One-Pot in Situ Hydrothermal Growth of BiVO 4 /Ag/rGO Hybrid Architectures for Solar Water Splitting and Environmental Remediation

Abstract: BiVO4 is ubiquitously known for its potential use as photoanode for PEC-WS due to its well-suited band structure; nevertheless, it suffers from the major drawback of a slow electron hole separation and transportation. We have demonstrated the one-pot synthesis of BiVO4/Ag/rGO hybrid photoanodes on a fluorine-doped tin oxide (FTO)-coated glass substrate using a facile and cost-effective hydrothermal method. The structural, morphological, and optical properties were extensively examined, confirming the formation of hybrid heterostructures. Ternary BiVO4/Ag/rGO hybrid photoanode electrode showed enhanced PEC performance with photocurrent densities (J ph ) of ~2.25 and 5 mA/cm2 for the water and sulfate oxidation, respectively. In addition, the BiVO4/Ag/rGO hybrid photoanode can convert up to 3.5% of the illuminating light into photocurrent, and exhibits a 0.9% solar-to-hydrogen conversion efficiency. Similarly, the photocatalytic methylene blue (MB) degradation afforded the highest degradation rate constant value (k = 1.03 × 10-2 min-1) for the BiVO4/Ag/rGO hybrid sample. It is noteworthy that the PEC/photocatalytic performance of BiVO4/Ag/rGO hybrid architectures is markedly more significant than that of the pristine BiVO4 sample. The enhanced PEC/photocatalytic performance of the synthesized BiVO4/Ag/rGO hybrid sample can be attributed to the combined effects of strong visible light absorption, improved charge separation-transportation and excellent surface properties.

Functionalized fluorescent nanomaterials for sensing pollutants in the environment: A critical review

Abstract: Quantitation of environmental pollutants has gained momentum due to its widespread requirement in the fields of clinical research, occupational hygiene, public health, and societal welfare. The use of functionalized fluorescent nanomaterials (FFNMs: e.g., metal nanoparticles, semiconductor quantum dots, carbon dots, nanotubes, and nanocrystals) has opened a new avenue for creating simple, selective, and non-invasive real-time analysis, as they can satisfy the growing demand for rapid and cost-effective quantitation. Here, we discuss novel strategies for the qualitative and quantitative analysis of a variety of organic and inorganic environmental pollutants by detecting changes in photo-physical or optical properties (e.g., fluorescence, absorbance, and color) of FFNMs used as probes. Particularly, we emphasize potential approaches for the synthesis and characterization of FFNMs and their underlying interactions with environmental pollutants. The simplification of design and enhancement of specificity towards target analytes should be pursued further to upgrade their real-world applicability in diverse fields.

Photocatalytic degradation of methylene blue by hydrothermally synthesized CZTS nanoparticles

Abstract: Due to the toxic effect of Methylene blue (MB) dye, its removal from water and water waste has gained significant attention in concern with green environment. In present work, a simple and low cost hydrothermal method has been used for the synthesis of copper zinc tin sulfide (CZTS) nanoparticles. Structural, morphological and optical properties of CZTS nanoparticles were characterized and it reveals that the synthesized powder has kesterite crystal structure with agglomerated morphology and shows a band gap of 1.53 eV leading to good potential to degrade methylene blue dye. When CZTS was introduced in aqueous MB solution as a catalyst and exposed to visible light for 45 min, about 50% degradation of MB was observed.

Honeycomb-layer structured Na3Ni2BiO6 as a high voltage and long life cathode material for sodium-ion batteries

Abstract: The need to find sodium ion battery (SIB) cathodes with high voltage, capacity and improved cycle life has stimulated research on sodium containing layered transition metal oxides. With this perspective, the electrochemical properties of highly ordered, honeycomb layered Na3Ni2BiO6 with a monoclinic superstructure are explored as a cathode material in SIBs. It has been demonstrated that Na3Ni2BiO6 delivers a discharge capacity of 106 mA h g−1, having high voltage plateaus at 3.50 and 3.25 V, with marginal capacity fading after 50 cycles. Operando X-ray diffraction studies during charging/discharging reveal two reversible two-phase transition mechanisms (initial O3 phase → P3 intermediate phase → O1 final phase) during sodium extraction. Ex situ X-ray absorption spectroscopy reveals the charge compensation mechanism for the reversible Ni3+/Ni2+ as an active redox couple while Bi5+ being inactive during cycling. Extended X-ray absorption fine structure analysis shows highly reversible local structural changes around both Ni and Bi atoms occurring during electrochemical cycling. In addition, unique local structure changes especially around Ni atoms due to the honeycomb ordering and size mismatch between Ni2+ and Bi5+ ions are revealed by EXAFS analysis during charging and discharging, which is quite different from the local structure changes in regular layer structured NaMO2 (M = transition metals) cathode materials. The present results suggest that honeycomb layered metal oxides with the general formula, Na3M(II)2M(V)O6, can be considered as candidates for high voltage and long life cathode materials for SIBs.

Nanostructured N-doped orthorhombic Nb2O5 as an efficient stable photocatalyst for hydrogen generation under visible light

Abstract: The synthesis of orthorhombic nitrogen-doped niobium oxide (Nb2O5-xNx) nanostructures was performed and a photocatalytic study carried out in their use in the conversion of toxic H2S and water into hydrogen under UV-Visible light. Nanostructured orthorhombic Nb2O5-xNx was synthesized by a simple solid-state combustion reaction (SSCR). The nanostructural features of Nb2O5-xNx were examined by FESEM and HRTEM, which showed they had a porous chain-like structure, with chains interlocked with each other and with nanoparticles sized less than 10 nm. Diffuse reflectance spectra depicted their extended absorbance in the visible region with a band gap of 2.4 eV. The substitution of nitrogen in place of oxygen atoms as well as Nb-N bond formation were confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. A computational study (DFT) of Nb2O5-xNx was also performed for investigation and conformation of the crystal and electronic structure. N-Substitution clearly showed a narrowing of the band gap due to N 2p bands cascading above the O 2p band. Considering the band gap in the visible region, Nb2O5-xNx exhibited enhanced photocatalytic activity toward hydrogen evolution (3010 μmol h-1 g-1) for water splitting and (9358 μmol h-1 g-1) for H2S splitting under visible light. The enhanced photocatalytic activity of Nb2O5-xNx was attributed to its extended absorbance in the visible region due to its electronic structure being modified upon doping, which in turn generates more electron-hole pairs, which are responsible for higher H2 generation. More significantly, the mesoporous nanostructure accelerated the supression of electron and hole recombination, which also contributed to the enhancement of its activity.

Facile synthesis of hierarchical mesoporous weirds-like morphological MnO2 thin films on carbon cloth for high performance supercapacitor application.

Abstract: The mesoporous nanostructured metal oxides have a lot of capabilities to upsurge the energy storing capacity of the supercapacitor. In present work, different nanostructured morphologies of MnO2 have been successfully fabricated on flexible carbon cloth by simple but capable hydrothermal method at different deposition temperatures. The deposition temperature has strong influence on reaction kinetics, which subsequently alters the morphology and electrochemical performance. Among different nanostructured MnO2 thin films, the mesoporous weirds composed thin film obtained at temperature of 453 K exhibits excellent physical and electrochemical features for supercapacitor application. The weirds composed MnO2 thin film exhibits specific surface area of 109 m2 g−1, high specific capacitance of 595 F g−1 with areal capacitance of 4.16 F cm−2 at a scan rate of 5 mV s−1 and high specific energy of 56.32 W h kg−1. In addition to this, MnO2 weirds attain capacity retention of 87 % over 2000 CV cycles, representing better cycling stability. The enhanced electrochemical performance could be ascribed to direct growth of highly porous MnO2 weirds on carbon cloth which provide more pathways for easy diffusion of electrolyte into the interior of electroactive material. The as-fabricated electrode with improved performance could be ascribed as a potential electrode material for energy storage devices.

In situ sol-gel synthesis of anatase TiO2-MWCNTs nanocomposites and their photocatalytic applications

Abstract: Visible light photoactive titania-multiwalled carbon nanotubes (TiO 2 -MWCNTs) nanocomposites were synthesized by in situ sol-gel method, in this TiO 2 nanoparticles were decorated on the surface of MWCNTs. The XRD analysis shows good crystalline nature of synthesized nanocomposite. UV–vis DRS study confirms the red shift of nanocmposites with respect to the increasing content of MWCNTs. The photocatalytic activity has investigated by degradation of methyl orange dye under ultraviolet as well as sunlight irradiation and photo-inactivation of Bacillus subtilis under visible light irradiation. The MWCNTs exist in the nanocomposite was able to absorb a high amount of photon energy in the sunlight, driving effectively photochemical degradation reactions. In the photodegradation of methyl orange dye under sunlight as well as photo-inactivation of Bacillus substilis under visible light, significant enhancement in the degradation/inactivation reaction rate was observed with the TiO 2 -MWCNTs (0.5 wt.%), nanocomposite as compared to TiO 2 NPs. The COD study confirms the environmentally benign nature of photodegraded dye solution. This work provides new insight for the fabrication of sunlight/visible active TiO 2 -MWCNTs nanocomposite photocatalyst for degradation of organic compounds and photo-inactivation of bacteria.

Chemical synthesis of hierarchical NiCo2S4 nanosheets like nanostructure on flexible foil for a high performance supercapacitor

Abstract: In this study, hierarchical interconnected nickel cobalt sulfide (NiCo2S4) nanosheets were effectively deposited on a flexible stainless steel foil by the chemical bath deposition method (CBD) for high-performance supercapacitor applications. The resulting NiCo2S4 sample was characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and electrochemical measurements. XRD and X-ray photoelectron spectroscopy (XPS) results confirmed the formation of the ternary NiCo2S4 sample with a pure cubic phase. FE-SEM and HR-TEM revealed that the entire foil surface was fully covered with the interconnected nanosheets like surface morphology. The NiCo2S4 nanosheets demonstrated impressive electrochemical characteristics with a specific capacitance of 1155 F g−1 at 10 mV s−1 and superior cycling stability (95% capacity after 2000 cycles). These electrochemical characteristics could be attributed to the higher active area and higher conductivity of the sample. The results demonstrated that the interconnected NiCo2S4 nanosheets are promising as electrodes for supercapacitor and energy storage applications.

Sunlight-assisted photocatalytic degradation of textile effluent and Rhodamine B by using iodine doped TiO2 nanoparticles

Abstract: Iodine-doped TiO2 nanoparticles (I@TiO2 NPs), in different mol percentage (mol%) of iodine with anatase phase only, have been prepared by using simple sol-gel method. Samples were characterized by various physico-chemical techniques. Physico-chemical characterization revealed that crystallite size, surface hydroxylation, and tuning of optical band gap towards visible region of composites increases with increase in dopant concentration upto 7.0 mol% in TiO2 host lattice. Thereafter, the samples were used to photocatalytic degradation of textile effluent (TE) as well as Rhodamine B (RhB) under sunlight irradiation directly. The progress of photodegradation reaction was monitored by UV–visible spectroscopy. The chemical oxygen demand (COD) of TE samples was evaluated before and after photocatalytic studies. During photocatalytic reaction, the effect of pH and amount of catalyst on the rate of degradation reaction was also studied. It is clearly shown that I@TiO2 particles result in the enhancement of the degradation ability of RhB as well as TE in sunlight.