Papers by Dr. Aayush Gupta
SN Applied Sciences
Carbon nanospheres (CNSs) couple large surface area, high electrical conductivity, thermal stabil... more Carbon nanospheres (CNSs) couple large surface area, high electrical conductivity, thermal stability and variable surface functionalities with controllable size, band gap and chemical properties. In the present study, mono-dispersed CNSs were synthesized by hydrothermal process from three saccharides-glucose, xylose (monosaccharides) and sucrose (disaccharide). The synthesized CNSs were characterized using XRD, FTIR, SEM, TEM and UV-visible spectroscopy. Xylose gives the smallest CNSs for the same solution concentration. The CNSs obtained are amorphous in nature and show direct bandgap ranging between 2.2 eV and 3.4 eV. The application of the synthesized CNSs as photo catalyst for organic waste degradation has been confirmed by comparative degradation of methylene blue dye in the presence of UV and visible light. The synthesized CNSs exhibited higher photodegradation efficiency under visible light illumination.
Physica B: Condensed Matter
In this reported work, the potential application of MnO 2 nanopowder for photocatalytic and the e... more In this reported work, the potential application of MnO 2 nanopowder for photocatalytic and the electrocatalytic applications is explored. The MnO 2 nanopowder has been synthesized through sonochemical route using KMnO 4 and poly-ethylene glycol as the reducing agent. Structural and optical analysis (XRD, TEM, FTIR, XPS and UV-visible) confirmed the formation of nanocrystalline MnO 2 network. The adsorption and photocatalytic performance of synthesized MnO 2 was tested for degradation of methylene blue dye and p-nitrophenol (2 mg/L) under dark chamber and household CFL lamp exposure, respectively. The electrochemical studies in alkaline (0.5 M KOH) medium shows the electric double layer capacitance of 7.4 mFcm −2 suggesting its potential application for energy storage devices. The synthesized compound exhibited excellent stability after 1000 CV cycles (∼4% current loss) where Volmer reaction was observed as the rate determining step for the electro-catalytic hydrogen evolution reaction.
Journal of Materials Chemistry C
The rapid urbanisation, high population density in all the nations requires sustainable security ... more The rapid urbanisation, high population density in all the nations requires sustainable security systems at all the times which can protect their people and the belongings against burglaries. A zero-power...
Solar Energy
In a view to the treatment required to degrade organic effluents and also waste utilization, a no... more In a view to the treatment required to degrade organic effluents and also waste utilization, a non-treditional photocatalyst (NbC/C nanocomposite) has been synthesized by using Nb 2 O 5 and cigarette litter (filter) at relatively low temperature 800 °C. With the help of XRD diffraction technique, the synthesis parameters have been optimized to get NbC/C nanocomposite and studied their morphology by transmission electron microscopy (TEM). The synthesized nanocomposite NbC/C was used to study the photocatalytic degradation of methylene blue (MB) dye under visible light illumination. Further, the effect of concentration of dye and photocatalyst has been studied under same conditions. With the help of BET, UV–visible absorbance, XPS, mass spectrometry and total organic carbon analysis, degradation mechanism has been established for the optimized nanocomposite sample.
Scientific Reports
A facile carbothermal route was adopted to obtain niobium carbide nanoparticles (NPs) embedded in... more A facile carbothermal route was adopted to obtain niobium carbide nanoparticles (NPs) embedded in carbon network from Nb 2 O 5 to study photocatalytic behavior. Optimization of synthesis parameters to obtain single phase NbC NPs has been successfully done. The phase identification, morphology and nature of carbon were determined with the help of X-ray diffraction, transmission electron microscopy (TEM) and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) suggested the presence of multiple oxidation states of Nb associated to NbC and NbC x O y centers on the surface of NPs. Due to the presence of NbC x O y on the surface of NPs, absorption under visible region of EM spectrum has been observed by UV-visible spectroscopy. Different organic dyes (RhB, MB and MO) were used to study the effect of holding time on the photocatalytic performance of as-synthesized samples. RhB dye was found to be the most sensitive organic molecule among all the considered dyes and degraded 78% in 120 min.
A facile single step chemical method is reported for the synthesis of Zr doped ZnS nanopowder and... more A facile single step chemical method is reported for the synthesis of Zr doped ZnS nanopowder and its photocatalytic performance has been studied. The average crystallite size of the synthesized powder estimated from Xray diffraction (XRD) is nearly 1.1 nm. Transmission electron microscopy (TEM) study shows that nanoparticles are agglomerated having a particle size of nearly 10 nm. The optical band gap of ZnS and Zr-doped ZnS, estimated with the help of UV-visible spectroscopy, is 3.7 and 2.9 eV, respectively. Photoluminescence (PL) spectroscopy indicated the role of lattice defects (vacancy, interstitial defects) on optical emission characteristics of doped ZnS samples. The photocatalytic activity of synthesized samples has also been investigated by degrading methylene blue (MB) dye under UV-visible illumination. The degradation quenching has been observed beyond 0.4 mol% doping of Zr in ZnS with maximum efficiency i.e. 80% in 4 h. Thereafter, the effect of aging is monitored for 1.5 months in which the modified emission properties of defect sites modulated the photocatalytic performance of Zr-doped ZnS sample. Further, with the help of various spectroscopic techniques (absorbance, PL and XPS), a mechanism for the photodegradation of MB dye by using Zr-doped ZnS nanopowder has been proposed.
Efficiency of oxide semiconductors for photocatalytic degradation of organic pollutants is highly... more Efficiency of oxide semiconductors for photocatalytic degradation of organic pollutants is highly dependent on their morphology, particle size, electron-hole recombination and oxygen vacancies. Doping of cations modifies the phase composition and induces oxygen vacancies needed for faster photocatalytic degradation of organic contaminants. Here, thioglycerol capped undoped and noble metal (Ag and Au) doped sub-10 nm sized CeO 2 nanoparticles (NPs) have been successfully synthesized at natural pH by co-precipitation method and were used as photocatalyst for degradation of rhodamine blue dye (RhB) in an aqueous medium under UV-Visible (UV-Vis.) irradiations without the addition of any external reagent. Photocatalytic studies revealed that among undoped and doped (Ag/Au) CeO 2 NPs, 2.0 at% Ag and 0.4 at% Au doping concentrations are optimum to demonstrate superior degradation efficiency. Degradation time was reduced further when RhB dye has been degraded with optimum doped NPs synthesized at higher pH. Moreover, gold doped NPs have shown better photocatalytic efficacy as compared to silver doped NPs. With the help of various characterizations, a possible degradation mechanism has been proposed which shows the effect of generation of oxygen vacancies owing to the doping of Ag and Au on photodegradation process.
A B S T R A C T Nanocomposites (NCs) of different band gap semiconductors provide better photocat... more A B S T R A C T Nanocomposites (NCs) of different band gap semiconductors provide better photocatalytic activity as compared to that of monolithic semiconductor nanoparticles (NPs). With the aim to investigate the effect of organic capping agent (thioglycerol; TG in the present study) on photocatalytic activity, ZnS-Ag 2 S NCs have been synthesized in the presence of TG using simple chemical precipitation route. For comparative studies, NCs have been synthesized under same synthesis conditions without TG. Structural studies were done using X-Ray diffraction (XRD) technique. Morphological features of as prepared samples were recorded by high resolution transmission electron microscopy (HRTEM). UV-Vis and photoluminescence studies were carried out to study the optical properties of synthesized samples. Photocatalytic studies of as-synthesized NCs have been carried out by selecting crystal violet (CV) as a model organic pollutant. It is observed that NCs (synthesized in absence of TG) exhibit better photocatalytic activity as compared to the TG capped NCs. The results of the present study may helpful in practical application of these composites in the area of photocatalysis and other related optical applications.
Due to increase in water pollution, there is a need to dwindle this problem for a clean and green... more Due to increase in water pollution, there is a need to dwindle this problem for a clean and green future. Photocatalysts like ZnO, CaO and TiO 2 have proved to be triumphant in removal of environmental contaminants. In this present work, ZrC nanopowder has been synthesized using a single-step reduction technique by heating zirconium oxide (ZrO 2 ) and hexane (C 6 H 14 ) in metallic Mg powder and is used as a photocatalyst for the degradation of methylene blue (MB) dye under solar radiation. Optimization of synthesis parameters (temperature, holding time and carbon content) has been done to obtain single phase ZrC. Various characterization techniques like X-ray diffraction (XRD), transmission electron microscope (TEM), differential scanning calorimetry/thermal gravimetric analysis (DSC/TGA) and X-ray photoelectron spectroscopy (XPS) were studied for various structural, thermal and surface characteristics of as-synthesized samples. The effect of synthesis parameters on crystal distortion of ZrC particles was studied with the help of Double Voigt analysis. Further, the comparative catalytic activity as photodegradation of MB dye with the help of optimized sample was studied under UV and solar radiations. As an effect of illumination source with the same concentration of catalyst and dye, 80% degradation was observed under solar radiations which is quite higher than that observed under UV in 5 h.
Nanoparticles of Z-type hexaferrites, Ba 3 Cu 2 Al x=2 Cr x=2 Fe 24Àx O 41 (x = 0.0, 0.5, 1.0), h... more Nanoparticles of Z-type hexaferrites, Ba 3 Cu 2 Al x=2 Cr x=2 Fe 24Àx O 41 (x = 0.0, 0.5, 1.0), have been prepared using sol-gel auto combustion method. The XRD patterns for these compositions show the formation of Ztype hexaferrite. The bands near 415-480 and 550-590 cm −1 in FTIR attribute to the bending and stretching of Fe-O bond vibration at octahedral and tetrahedral site of hexaferrite. VSM study shows the highest values of coercivity (911.11 Oe), retentivity (41.5 emu/g), and saturation magnetization (17.5 emu/g) for x = 1. Radiation absorbance investigation in the microwave X-band (8-12.5 GHz) region shows the maximum radiation loss of −31.19 dB (99.99% loss) at frequency 11.14 GHz for x = 0.5 and hence can be used commercially for microwave as well as antenna applications.
In this reported work, the potential application of MnO 2 nanopowder for photocatalytic and the e... more In this reported work, the potential application of MnO 2 nanopowder for photocatalytic and the electrocatalytic applications is explored. The MnO 2 nanopowder has been synthesized through sonochemical route using KMnO 4 and poly-ethylene glycol as the reducing agent. Structural and optical analysis (XRD, TEM, FTIR, XPS and UV-visible) confirmed the formation of nanocrystalline MnO 2 network. The adsorption and photocatalytic performance of synthesized MnO 2 was tested for degradation of methylene blue dye and p-nitrophenol (2 mg/L) under dark chamber and household CFL lamp exposure, respectively. The electrochemical studies in alkaline (0.5 M KOH) medium shows the electric double layer capacitance of 7.4 mFcm −2 suggesting its potential application for energy storage devices. The synthesized compound exhibited excellent stability after 1000 CV cycles (∼4% current loss) where Volmer reaction was observed as the rate determining step for the electro-catalytic hydrogen evolution reaction.
Undoped, Ca-doped NaNbO 3 and its heterostructure with g-C 3 N 4 have been successfully prepared ... more Undoped, Ca-doped NaNbO 3 and its heterostructure with g-C 3 N 4 have been successfully prepared through chemical route followed by heat treatment. All the prepared samples were analysed using XRD, FESEM, TEM and XPS spectroscopy for various structural and surface features. Further, absorbance (UV-visible) and photo-luminescence (PL) spectroscopy revealed the bandgap narrowing and emission quenching, respectively as a result of doping and formation of heterojunction. Ca doped NaNbO 3-C 3 N 4 sample exhibited almost 100% photodegradation of methylene blue (MB) dye in 4 h. Here, the superoxide anion radical has been found as the active reactive oxidative species (ROS). Further, being a visible active catalyst, photocatalytic H 2 evolution has also been studied through water splitting under solar irradiations in which H 2 yield of 0.01, 0.03, 0.09 and 0.29 mmol (in 1 h) was observed using bare NaNbO 3 , Ca-NaNbO 3 , and their respective heterostructures, respectively. Modified oxygen vacancies and synergistic interracial interaction have induced such a noteworthy photocatalytic H 2 evolution ability of as-prepared heterostructure with 3.45 mmol H 2 yield 4 h of exposure.
Niobium diboride (NbB 2) nanoparticles have been successfully synthesized at 800 C in a single st... more Niobium diboride (NbB 2) nanoparticles have been successfully synthesized at 800 C in a single step from niobium penta-oxide (Nb 2 O 5), magnesium (Mg) and borax (Na 2 B 4 O 7 $10H 2 O) in an autoclave. The synthesis temperature and holding time have been optimized to obtain single phase NbB 2. The phase determination, thermal stability and morphological features of synthesized samples have been analyzed by X-ray diffraction (XRD), thermal gravimetric-differential scanning calorimetry (TG-DSC) and electron microscopic technique respectively. Williamson-Hall (W-H) analysis has also been done to observe the effects of synthesis parameters (temperature and holding time) on crystal distortion. With the help of XRD, microstructural features and thermodynamic calculations, formation mechanism for the synthesized samples has been predicted.
In a view to the treatment required to degrade organic effluents and also waste utilization, a no... more In a view to the treatment required to degrade organic effluents and also waste utilization, a non-treditional photocatalyst (NbC/C nanocomposite) has been synthesized by using Nb 2 O 5 and cigarette litter (filter) at relatively low temperature 800 °C. With the help of XRD diffraction technique, the synthesis parameters have been optimized to get NbC/C nanocomposite and studied their morphology by transmission electron microscopy (TEM). The synthesized nanocomposite NbC/C was used to study the photocatalytic degradation of methylene blue (MB) dye under visible light illumination. Further, the effect of concentration of dye and photocatalyst has been studied under same conditions. With the help of BET, UV–visible absorbance, XPS, mass spectrometry and total organic carbon analysis, degradation mechanism has been established for the optimized nanocomposite sample.
Core-shell NbC/C nano composite has been synthesized by reacting niobium pentaoxide (Nb 2 O 5) wi... more Core-shell NbC/C nano composite has been synthesized by reacting niobium pentaoxide (Nb 2 O 5) with metallic magnesium and acetone (C 3 H 6 O). The ensued powder samples are characterized by X-ray dif-fraction (XRD), differential scanning calorimetry/thermal gravimetric analysis (DSC/TGA), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis. The synthesis temperature, holding time and heating rate has been optimized to facilitate the in-situ reduction-carburization of Nb 2 O 5. The broadening of XRD diffraction peaks corresponding to NbC is analyzed using Williamson-Hall (W-H) analysis by calculating various parameters such as strain, stress, strain energy density for all the samples. The mean particle size of nano NbC is estimated by Scherrer's criterion which is highly correlated with W-H analysis in less stressed system. The electron microscopy analysis showed that particles have a partial faceted morphology along with carbon layer and having wide particle size distribution. BET analysis depicted large surface area having a combination of micropores and mesopores. All the results of various characterizations have been used to predict the mechanism of formation of core-shell NbC/C nano composite.
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Papers by Dr. Aayush Gupta