Nickel selenide is an emerging electrode material for high‐performance hybrid supercapacitors; ho... more Nickel selenide is an emerging electrode material for high‐performance hybrid supercapacitors; however, poor electrical conductivity and sluggish ion kinetics limit its application. Herein, a unique architecture by decorating NiSe nanoparticles on reduced graphene oxides (rGO) is developed. The synergistic effect of NiSe and rGO facilitated by the optimized addition of rGO results in significant improvement in the electrochemical performance. The physicochemical characterizations suggest that the enhancement can be attributed to increased interfacial interaction and access to the electrochemically active sites. The NiSe/rGO hybrid delivers a specific capacity of 351 mAh g−1 at 1 A g−1, which is significantly higher than that for bare NiSe. Later, the hybrid supercapacitor based on NiSe/rGO hybrid as positive and activated carbon as negative electrode delivers a maximum energy density of 49.6 Wh kg−1 at a power density of 748.37 W kg−1. In addition, the device shows good cyclic stabi...
In this contemporary world of human – computer interaction, where abatement of efforts is eulogiz... more In this contemporary world of human – computer interaction, where abatement of efforts is eulogized, „Face Enabled Mouse using Motion Detection and Speech Recognition‟ provides a brilliant asset for an advanced interaction with the modern day computers. This system, in its‟ real world scenario, is capable of tracking the human head with the assistance of a simple yet an operative Face Tracking Algorithm. The objective of this project is to make the real time computing uncomplicated and more facile. Not only, will the computer conduct the actions as per the head movements but also correspond to the speech as input commands. This makes the system more versatile and easy to use through all the sections of the society.
Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materia... more Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materials for energy conversion and storage systems. Interest in these materials is due to their good electrochemical stability, eco‐friendly nature, and low cost. The present review compiles recent progress in the area of nickel‐(S and Se)‐based materials by providing a comprehensive summary of their structural and chemical features and performance. Improving properties of the materials, such as electrical conductivity and surface characteristics (surface area and morphology), through strategies like nano‐structuring and hybridization, are systematically discussed. The interaction of the materials with electrolytes, other electro‐active materials, and inactive components are analyzed to understand their effects on the performance of energy conversion and storage devices. Finally, outstanding challenges and possible solutions are briefly presented with some perspectives toward the future develo...
Significant difference in the nanoscale magnetism of nanoparticles and nanofibres of biphasic LuF... more Significant difference in the nanoscale magnetism of nanoparticles and nanofibres of biphasic LuFeO3.
We report on the realization of particle size, morphology, and chemical composition controlled co... more We report on the realization of particle size, morphology, and chemical composition controlled cobalt ferrite nanoparticles (CFO NPs) with tunable magnetic properties for application in electronic and electromagnetic devices. The effect of oleic acid concentration (0.0–0.1 M) on the structural, physical, chemical, electronic, and magnetic properties of solvothermally synthesized CFO NPs is investigated in detail by using the oleic acid (OA) based chemical method for synthesis. Crystalline, cubic, and chemically homogeneous CFO NPs (5–15 nm) can be obtained by controlling the OA concentration. Spectroscopic analyses revealed that the OA molecules form covalent bonds with CFO NPs. The particle-size control was achieved by bridging bidentate interactions between the OA molecules and CFO NPs. Detailed magnetic measurements revealed that the OA concentration helps to effectively control the magnetic behavior of particle-size-controlled CFO NPs. The interfacing between OA molecules and CFO surface atoms leads t...
We report the experimental observation of variable range hopping conduction in focused-ion-beam (... more We report the experimental observation of variable range hopping conduction in focused-ion-beam (FIB) fabricated ultra-narrow nanowires of topological insulator (Bi2Se3). The value of the exponent (d + 1)−1 in the hopping equation was extracted as $$ \sim \frac{1}{2}\,\,$$ ~ 1 2 for different widths of nanowires, which is the proof of the presence of Efros-Shklovskii hopping transport mechanism in a strongly disordered system. High localization lengths (0.5 nm, 20 nm) were calculated for the devices. A careful analysis of the temperature dependent fluctuations present in the magnetoresistance curves, using the standard Universal Conductance Fluctuation theory, indicates the presence of 2D topological surface states. Also, the surface state contribution to the conductance was found very close to one conductance quantum. We believe that our experimental findings shed light on the understanding of quantum transport in disordered topological insulator based nanostructures.
We report the fabrication of high-performance MgB 2 bulk superconductors doped with amorphous car... more We report the fabrication of high-performance MgB 2 bulk superconductors doped with amorphous carbon (aC), derived from PMMA polymer, a safe and cost effective carbon source as compared to explosive gaseous and expensive C-containing nanoadditives. The commonly used C-containing nanoadditives and boron (B) precursor nanopowders are usually prone to agglomeration in solid state mixing which causes poor reactivity and non-uniform distribution that leads to deterioration of critical current properties of MgB 2. We have overcome this problem by achieving uniform 3e4 nm thin coating of aC on B nanopowders by pyrolysis of PMMA through solution process. Compared to undoped MgB 2 , significantly high current-carrying capability (J c (5 K, 8 T)~3.1 Â 10 4 A/cm 2 and J c (20 K, 6 T) > 10 3 A/cm 2) was obtained for aC-doped MgB 2 , which is comparable to the record high in-field J c reported for SiC-doped MgB 2 and much better than those reported in literature with other C sources. Furthermore, significant improvement in H irr and H c2 were also observed for aC-doped MgB 2. The improved high-field properties in PMMA-derived aC-doped MgB 2 bulk suggest that the solution process could be a powerful technique to obtain uniform mixture of C-coated B to develop high-performance Mg(B 1Àx C x) 2 wires for practical applications.
Progress in Superconductivity and Cryogenics, 2012
MgB 2 superconductor is highly sensitive to the Mg content. Even if the samples are synthesized w... more MgB 2 superconductor is highly sensitive to the Mg content. Even if the samples are synthesized with the appropriate looking stoichiometric ratio, the heat treatment leads to the loss of Mg either to ambiance or to MgO. To avoid it, either excess Mg is added in the starting powder or sealed ampoule annealing is employed. In this paper the effect of open Mg sintering ambiance on the ex-situ MgB 2 was studied to enhance its superconducting properties. The open Mg ambiance was created to avoid any overpressure of Mg by providing a hole in Fe tube used as sample holder. The decrease in resistivity of the synthesized sample was observed through the increased temperature dependence of electron-phonon interactions. A clear enhancement in the superconducting cross-sectional area and hence the in-field critical current density is obtained.
abstract ZnO (002) films of thickness 0.5 μm were grown on c-plane sapphire substrates by Pulsed ... more abstract ZnO (002) films of thickness 0.5 μm were grown on c-plane sapphire substrates by Pulsed Laser Deposition technique at 400 C in oxygen ambient of 75 mTorr and implanted with 8x10 14 cm-2 dose of phosphorus ions of energy 50 keV (Sample A) followed by Rapid Thermal Annealing in Ar (Sample B) and oxygen atmospheres (Sample C) at 750 C (30 seconds). AFM images depicted root-mean-square roughness for Sample A (10.072 nm), B (9.314 nm) and C (4.9 nm). Room-temperature Hall study revealed n-type conductivity ...
The modulation of CdS nanostructures from spherical nanoparticles to 2-D nanoflake arrays through... more The modulation of CdS nanostructures from spherical nanoparticles to 2-D nanoflake arrays through Cd : S precursor ratio variation for photo-electrochemical applications.
Wurtzite Cu2SnS3 (CTS) nanocrystals with an average size 8.5 nm were prepared for the first time ... more Wurtzite Cu2SnS3 (CTS) nanocrystals with an average size 8.5 nm were prepared for the first time by a phosphine and oleylamine free facile one-step thermolysis method. The as-prepared nanocrystals were investigated for structural, morphological and compositional properties. The advantages of the heat-up technique for a swift synthesis of gram scale, phase pure CTS nanocrystals; applicable for various energy devices like solar cell, batteries etc., are discussed. Nanocrystals were synthesized at different reaction times viz. 10, 20 and 30 minutes. The possible growth mechanism for colloidal CTS nanocrystals has been investigated. Herein we observed that CTS nanocrystals growth starts with the formation of copper sulphide nanoparticles, acting as nuclei for the subsequent growth of CTS nanocrystals. X-ray diffraction analysis revealed the formation of phase pure wurtzite CTS nanocrystals which is further supported by high resolution transmission electron microscopy, selected area electron diffraction and energy dispersive X-ray analysis. To the best of our knowledge colloidal wurtzite CTS nanocrystals synthesis has been reported with the use of strongly co-ordinating, highly toxic oleylamine (OLA) solvent, herein stepping towards a green synthesis we report for the first time on the synthesis of sub 10 nm wurtzite CTS nanocrystals using neutral, less toxic and less expensive octadecene (ODE) solvent.
Abstract Holmium nitride (HoN) nanocrystallites were synthesized by a plasma arc discharge techni... more Abstract Holmium nitride (HoN) nanocrystallites were synthesized by a plasma arc discharge technique and characterized to study their magnetocaloric properties. HoN was formed under the influence of nitrogen–argon mixed gas. N2 gas was used as an active element for arc discharge between two electrodes maintained at a constant current. In addition, N2 gas played an important role not only as a reducing agent but also as an inevitable source of excited nitrogen molecules and nitrogen ions for the formation of HoN phase. The ratio of partial pressure between Ar and N2 was systematically varied to obtain single phase HoN with minimal impurities. Magnetocaloric properties were measured by applying fields up to 50 kOe in the temperature range from 6 K to 60 K. The as-synthesized HoN nanoparticles have shown a change in magnetic entropy of 27.5 J/kgK with a transition temperature at 14.2 K thereby demonstrating their ability to be applied as an effective low temperature magnetic refrigerant material towards the re-liquefaction of H2.
ZnO has been a subject of intense research in the optoelectronics community owing to its wide ban... more ZnO has been a subject of intense research in the optoelectronics community owing to its wide bandgap (3.3eV) and large exciton binding energy (60meV). However, difficulty in doping it p-type posts a hindrance in fabricating ZnObased devices. In an attempt to make it p-type we have studied Li-implanted (Energy=40keV, dose=5x1013cm-2) ZnO films grown over sapphire substrates by Pulsed Laser Deposition
Nickel selenide is an emerging electrode material for high‐performance hybrid supercapacitors; ho... more Nickel selenide is an emerging electrode material for high‐performance hybrid supercapacitors; however, poor electrical conductivity and sluggish ion kinetics limit its application. Herein, a unique architecture by decorating NiSe nanoparticles on reduced graphene oxides (rGO) is developed. The synergistic effect of NiSe and rGO facilitated by the optimized addition of rGO results in significant improvement in the electrochemical performance. The physicochemical characterizations suggest that the enhancement can be attributed to increased interfacial interaction and access to the electrochemically active sites. The NiSe/rGO hybrid delivers a specific capacity of 351 mAh g−1 at 1 A g−1, which is significantly higher than that for bare NiSe. Later, the hybrid supercapacitor based on NiSe/rGO hybrid as positive and activated carbon as negative electrode delivers a maximum energy density of 49.6 Wh kg−1 at a power density of 748.37 W kg−1. In addition, the device shows good cyclic stabi...
In this contemporary world of human – computer interaction, where abatement of efforts is eulogiz... more In this contemporary world of human – computer interaction, where abatement of efforts is eulogized, „Face Enabled Mouse using Motion Detection and Speech Recognition‟ provides a brilliant asset for an advanced interaction with the modern day computers. This system, in its‟ real world scenario, is capable of tracking the human head with the assistance of a simple yet an operative Face Tracking Algorithm. The objective of this project is to make the real time computing uncomplicated and more facile. Not only, will the computer conduct the actions as per the head movements but also correspond to the speech as input commands. This makes the system more versatile and easy to use through all the sections of the society.
Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materia... more Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materials for energy conversion and storage systems. Interest in these materials is due to their good electrochemical stability, eco‐friendly nature, and low cost. The present review compiles recent progress in the area of nickel‐(S and Se)‐based materials by providing a comprehensive summary of their structural and chemical features and performance. Improving properties of the materials, such as electrical conductivity and surface characteristics (surface area and morphology), through strategies like nano‐structuring and hybridization, are systematically discussed. The interaction of the materials with electrolytes, other electro‐active materials, and inactive components are analyzed to understand their effects on the performance of energy conversion and storage devices. Finally, outstanding challenges and possible solutions are briefly presented with some perspectives toward the future develo...
Significant difference in the nanoscale magnetism of nanoparticles and nanofibres of biphasic LuF... more Significant difference in the nanoscale magnetism of nanoparticles and nanofibres of biphasic LuFeO3.
We report on the realization of particle size, morphology, and chemical composition controlled co... more We report on the realization of particle size, morphology, and chemical composition controlled cobalt ferrite nanoparticles (CFO NPs) with tunable magnetic properties for application in electronic and electromagnetic devices. The effect of oleic acid concentration (0.0–0.1 M) on the structural, physical, chemical, electronic, and magnetic properties of solvothermally synthesized CFO NPs is investigated in detail by using the oleic acid (OA) based chemical method for synthesis. Crystalline, cubic, and chemically homogeneous CFO NPs (5–15 nm) can be obtained by controlling the OA concentration. Spectroscopic analyses revealed that the OA molecules form covalent bonds with CFO NPs. The particle-size control was achieved by bridging bidentate interactions between the OA molecules and CFO NPs. Detailed magnetic measurements revealed that the OA concentration helps to effectively control the magnetic behavior of particle-size-controlled CFO NPs. The interfacing between OA molecules and CFO surface atoms leads t...
We report the experimental observation of variable range hopping conduction in focused-ion-beam (... more We report the experimental observation of variable range hopping conduction in focused-ion-beam (FIB) fabricated ultra-narrow nanowires of topological insulator (Bi2Se3). The value of the exponent (d + 1)−1 in the hopping equation was extracted as $$ \sim \frac{1}{2}\,\,$$ ~ 1 2 for different widths of nanowires, which is the proof of the presence of Efros-Shklovskii hopping transport mechanism in a strongly disordered system. High localization lengths (0.5 nm, 20 nm) were calculated for the devices. A careful analysis of the temperature dependent fluctuations present in the magnetoresistance curves, using the standard Universal Conductance Fluctuation theory, indicates the presence of 2D topological surface states. Also, the surface state contribution to the conductance was found very close to one conductance quantum. We believe that our experimental findings shed light on the understanding of quantum transport in disordered topological insulator based nanostructures.
We report the fabrication of high-performance MgB 2 bulk superconductors doped with amorphous car... more We report the fabrication of high-performance MgB 2 bulk superconductors doped with amorphous carbon (aC), derived from PMMA polymer, a safe and cost effective carbon source as compared to explosive gaseous and expensive C-containing nanoadditives. The commonly used C-containing nanoadditives and boron (B) precursor nanopowders are usually prone to agglomeration in solid state mixing which causes poor reactivity and non-uniform distribution that leads to deterioration of critical current properties of MgB 2. We have overcome this problem by achieving uniform 3e4 nm thin coating of aC on B nanopowders by pyrolysis of PMMA through solution process. Compared to undoped MgB 2 , significantly high current-carrying capability (J c (5 K, 8 T)~3.1 Â 10 4 A/cm 2 and J c (20 K, 6 T) > 10 3 A/cm 2) was obtained for aC-doped MgB 2 , which is comparable to the record high in-field J c reported for SiC-doped MgB 2 and much better than those reported in literature with other C sources. Furthermore, significant improvement in H irr and H c2 were also observed for aC-doped MgB 2. The improved high-field properties in PMMA-derived aC-doped MgB 2 bulk suggest that the solution process could be a powerful technique to obtain uniform mixture of C-coated B to develop high-performance Mg(B 1Àx C x) 2 wires for practical applications.
Progress in Superconductivity and Cryogenics, 2012
MgB 2 superconductor is highly sensitive to the Mg content. Even if the samples are synthesized w... more MgB 2 superconductor is highly sensitive to the Mg content. Even if the samples are synthesized with the appropriate looking stoichiometric ratio, the heat treatment leads to the loss of Mg either to ambiance or to MgO. To avoid it, either excess Mg is added in the starting powder or sealed ampoule annealing is employed. In this paper the effect of open Mg sintering ambiance on the ex-situ MgB 2 was studied to enhance its superconducting properties. The open Mg ambiance was created to avoid any overpressure of Mg by providing a hole in Fe tube used as sample holder. The decrease in resistivity of the synthesized sample was observed through the increased temperature dependence of electron-phonon interactions. A clear enhancement in the superconducting cross-sectional area and hence the in-field critical current density is obtained.
abstract ZnO (002) films of thickness 0.5 μm were grown on c-plane sapphire substrates by Pulsed ... more abstract ZnO (002) films of thickness 0.5 μm were grown on c-plane sapphire substrates by Pulsed Laser Deposition technique at 400 C in oxygen ambient of 75 mTorr and implanted with 8x10 14 cm-2 dose of phosphorus ions of energy 50 keV (Sample A) followed by Rapid Thermal Annealing in Ar (Sample B) and oxygen atmospheres (Sample C) at 750 C (30 seconds). AFM images depicted root-mean-square roughness for Sample A (10.072 nm), B (9.314 nm) and C (4.9 nm). Room-temperature Hall study revealed n-type conductivity ...
The modulation of CdS nanostructures from spherical nanoparticles to 2-D nanoflake arrays through... more The modulation of CdS nanostructures from spherical nanoparticles to 2-D nanoflake arrays through Cd : S precursor ratio variation for photo-electrochemical applications.
Wurtzite Cu2SnS3 (CTS) nanocrystals with an average size 8.5 nm were prepared for the first time ... more Wurtzite Cu2SnS3 (CTS) nanocrystals with an average size 8.5 nm were prepared for the first time by a phosphine and oleylamine free facile one-step thermolysis method. The as-prepared nanocrystals were investigated for structural, morphological and compositional properties. The advantages of the heat-up technique for a swift synthesis of gram scale, phase pure CTS nanocrystals; applicable for various energy devices like solar cell, batteries etc., are discussed. Nanocrystals were synthesized at different reaction times viz. 10, 20 and 30 minutes. The possible growth mechanism for colloidal CTS nanocrystals has been investigated. Herein we observed that CTS nanocrystals growth starts with the formation of copper sulphide nanoparticles, acting as nuclei for the subsequent growth of CTS nanocrystals. X-ray diffraction analysis revealed the formation of phase pure wurtzite CTS nanocrystals which is further supported by high resolution transmission electron microscopy, selected area electron diffraction and energy dispersive X-ray analysis. To the best of our knowledge colloidal wurtzite CTS nanocrystals synthesis has been reported with the use of strongly co-ordinating, highly toxic oleylamine (OLA) solvent, herein stepping towards a green synthesis we report for the first time on the synthesis of sub 10 nm wurtzite CTS nanocrystals using neutral, less toxic and less expensive octadecene (ODE) solvent.
Abstract Holmium nitride (HoN) nanocrystallites were synthesized by a plasma arc discharge techni... more Abstract Holmium nitride (HoN) nanocrystallites were synthesized by a plasma arc discharge technique and characterized to study their magnetocaloric properties. HoN was formed under the influence of nitrogen–argon mixed gas. N2 gas was used as an active element for arc discharge between two electrodes maintained at a constant current. In addition, N2 gas played an important role not only as a reducing agent but also as an inevitable source of excited nitrogen molecules and nitrogen ions for the formation of HoN phase. The ratio of partial pressure between Ar and N2 was systematically varied to obtain single phase HoN with minimal impurities. Magnetocaloric properties were measured by applying fields up to 50 kOe in the temperature range from 6 K to 60 K. The as-synthesized HoN nanoparticles have shown a change in magnetic entropy of 27.5 J/kgK with a transition temperature at 14.2 K thereby demonstrating their ability to be applied as an effective low temperature magnetic refrigerant material towards the re-liquefaction of H2.
ZnO has been a subject of intense research in the optoelectronics community owing to its wide ban... more ZnO has been a subject of intense research in the optoelectronics community owing to its wide bandgap (3.3eV) and large exciton binding energy (60meV). However, difficulty in doping it p-type posts a hindrance in fabricating ZnObased devices. In an attempt to make it p-type we have studied Li-implanted (Energy=40keV, dose=5x1013cm-2) ZnO films grown over sapphire substrates by Pulsed Laser Deposition
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Papers by Bhavesh Sinha