The field emission properties of ion irradiated multiwalled carbon nanotubes (MWCNTs) and doublew... more The field emission properties of ion irradiated multiwalled carbon nanotubes (MWCNTs) and doublewalled carbon nanotubes (DWCNTs) have been studied. The carbon nanotubes synthesized by a chemical vapor deposition method were irradiated by high energy (90 MeV) Au ions with different ion fluence from 4x1011 to 1x1013 ions/cm2 . After ion irradiation, the field emission properties of MWCNTs and DWCNTs were greatly influenced. The change in the emission characteristics is due to structural defects caused by the high energy ion irradiation. The emission characteristic of MWCNTs was improved and turn-on field decreased from 5.43 to 3.10 V/m by ion irradiation. Noticeable improvement in emission characteristics of MWCNTs was observed at a fluence of 1x 10 13 ions/cm2. The emission characteristics of DWCNTs deteriorated and the turn-on field was increased from 2.44 to 7.76 V/m. This results show the distinctly different behavior of ion irradiated MWCNTs and DWCNTs.
Eu3+ doped polymer nanofibers were fabricated by electrospinning technique using various polymers... more Eu3+ doped polymer nanofibers were fabricated by electrospinning technique using various polymers such as poly(vinylidene fluoride) (PVDF), polyethylene oxide (PEO), poly(vinyl pyrrolidone) (PVP) to study the influence of polymer in their photoluminescence properties. As-fabricated nanofibers were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and photoluminescence (PL). Spectral analysis of Polymer/Eu3+ nanofibers was based on their emission spectra. The photoluminescence property shows superior bright red emission spectra from the Eu3+ and relatively stronger hypersensitive behavior of the 5D0 → 7F2 transition. Eu3+ doped polymeric nanofibers are very much suitable for photoluminescent fabric designing in smart textiles. The enhanced properties of this photoluminescence indicated a more polarized chemical environment for the Eu3+ ions and greater hypersensitivity for the 5D0 → 7F2 transition, which showed the potential for application in ...
In the present study, we report a simple method to prepare indium(III) selenide (In2Se3) nanocube... more In the present study, we report a simple method to prepare indium(III) selenide (In2Se3) nanocubes synthesized by laser ablation in aqueous medium. The morphological characterization carried out us...
In the present study, the field emission properties of multi-walled carbon nanotubes (MWCNTs) tre... more In the present study, the field emission properties of multi-walled carbon nanotubes (MWCNTs) treated with laser ablation have been investigated. The MWCNTs were synthesized by chemical vapor deposition method. The laser ablation treatment was performed in liquid medium for laser ablation time of 40 min and 60 min. The morphology of MWCNTs films was characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results exhibit that the field emission properties of MWCNTs are dependent on the laser ablation time. The Raman spectra of laser-ablated MWCNTs clearly showed disorder and increase in graphitic content. The SEM and TEM results clearly revealed the separation of MWCNTs after laser ablation treatment. The field emission characteristics of the MWCNTs showed that the turn-on fields and current density are improved for the nanotubes treated with laser ablation. The enhancement in the field emission characteristics of ...
A new class of emerging materials known as topological insulators (TIs), such as bismuth selenide... more A new class of emerging materials known as topological insulators (TIs), such as bismuth selenide [Formula: see text], has an insulating band gap in the bulk and gapless surface state protected by its intrinsic time-reversal symmetry. These TI materials have attracted great attention because of their possible prospects in electrical and optical applications. In this work, we have prepared the [Formula: see text] nanostructure using the nanosecond (ns) pulse laser ablation in liquid environment to study the field effect transistor behavior. After the laser ablation, [Formula: see text] nanostructures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy to reveal the surface morphology and structural information. The field effect transistor (FET) has been fabricated using [Formula: see text] nanostructure by drop casting [Formula: see text] suspension between two gold electrodes having a gap of 3 [Formula: see text]m on [Formula...
In this study, zinc sulfide (ZnS)/titanium oxide(TiO2) nanoparticles were prepared by a two-step ... more In this study, zinc sulfide (ZnS)/titanium oxide(TiO2) nanoparticles were prepared by a two-step facile hydrothermal method and then annealing at [Formula: see text] for 30 min. Also, the transient absorption measurement and photocatalytic activity of ZnS/TiO2 before and after annealing were investigated. The characterization technique such as the scanning electron microscopy (SEM) and X-ray diffraction (XRD) and UV–Visible spectroscopy have been employed to study the surface morphology and structural details. The SEM image shows the change in the surface morphology due to annealing. The change of the crystal structure of ZnS–TiO2 is revealed by XRD spectra. The femtosecond transient absorption measurement showed moderate decay over several hundred picoseconds for annealed ZnS/TiO2. Moreover, improved photocatalytic activity of annealed ZnS/TiO2 nanoparticles in visible light has been observed.
Novel unique fabrication of ZnO nanoparticles decorated graphene beaded carbon nanofibers (G-CNF)... more Novel unique fabrication of ZnO nanoparticles decorated graphene beaded carbon nanofibers (G-CNF) encapsulated by polyaniline (PANI) nanocomposites through three steps by electrospinning, hydrothermal and in-situ polymerization is reported. As-synthesized G-CNF/ZnO/PANI and CNF/ZnO/PANI nanocomposites were comparatively studied by scanning electron microscopy and electrochemical characterizations for supercapacitor application. Electrochemical measurements of G-CNF/ZnO/PANI electrode revealed the maximum specific capacitance, discharge time, energy density and power density as compared to that of CNF/ZnO/PANI indicating the increase in surface area due to graphene incorporation in electrospinning of carbon nanofibers. The combination of electric double layer charge (EDLC) capacitance from high surface area of G-CNF and pseudo-capacitance from PANI and ZnO nanoparticles facilitates the synergistic effect of ternary components to enhance the electrochemical performance of G-CNF/ZnO/PA...
Abstract Present work portrays the surface morphology dependent electrochemical behaviors tuned b... more Abstract Present work portrays the surface morphology dependent electrochemical behaviors tuned by annealing the chemical bath deposited (CBD) cerium oxide electrodes. The altered nanostructure properties are well-supported by in-depth structural and morphological analysis. Cerium oxide electrode annealed at 200 °C exhibits good surface properties enabling maximum electro-active porous cavities to penetrate electrolyte ions towards enhanced electron transfer. Consequently, the electrode exhibits maximum specific capacitance of 750 F/g with remarkably stable charge-discharge cycles. Fabricated symmetric solid-state supercapacitor device impressively expands potential window to 1.2 V with the aid of PVA-LiClO4 gel electrolyte with a peak specific capacitance of 321.3 F/g with top-up of 61.4 Wh/kg specific energy. The series combination of two devices confirms the strong energy storage ability by glowing ‘VNIT’ acronym designed through 21 red LEDs from the practical point of view.
Abstract We report an eco-friendly green synthesis of highly luminescent CuInS2/ZnS core-shell qu... more Abstract We report an eco-friendly green synthesis of highly luminescent CuInS2/ZnS core-shell quantum dots (QDs) with average particle size ∼ 3.9 nm via solvothermal process. The present study embodies the intensification of CuInS2/ZnS QDs properties by the shell growth on the CuInS2 QDs. The as-prepared CuInS2 core and CuInS2/ZnS core-shell QDs have been characterized using a range of optical and structural techniques. By adopting a low temperature growth of CuInS2 core and high temperature growth of CuInS2/ZnS core-shell growth, the tuning of absorption and photoluminescence emission spectra were observed. Optical absorption and photoluminescence spectroscopy probe the effect of ZnS passivation on the electronic structure of the CuInS2 dots. In addition, QDs have been scrutinized using ultra violet photoelectron spectroscopy (UPS) to explore their electronic band structure. The band level positions of CuInS2 and CuInS2/ZnS QDs suffices the demand of non-toxic acceptor material for electronic devices. The variation in electronic energy levels of CuInS2 core with the coating of wide band gap ZnS shell influence the removal of trap assisted recombination on the surface of the core. QDs exhibited tunable emission from red to orange region. These studies reveal the feasibility of QDs in photovoltaic and light emitting diodes.
Abstract Field emission (FE) properties of hydrothermally synthesized, SnO 2 -RGO nanocomposite h... more Abstract Field emission (FE) properties of hydrothermally synthesized, SnO 2 -RGO nanocomposite have been investigated at a base pressure of 1×10 −8 mbar. The results reveal that the SnO 2 -RGO nanocomposite emitter prevails over the pristine RGO emitter. The values of turn-on field, defined at emission current density of 1 μA/cm 2 , are found to be 1.8 and 2.2 V/μm for the SnO 2 -RGO and pristine RGO emitters, respectively. Furthermore, the SnO 2 -RGO emitter delivers maximum emission current density of ~800 µA/cm 2 at an applied field of 5 V/μm. The observed values of applied field corresponding to emission current densities of 1 μA/cm 2 and 10 µA/cm 2 are superior to those reported for various emitters due to SnO 2 nanostructures and their composites. The emission current at the pre-set value of 1 µA is found to be very stable over a period of 3hrs. The enhanced FE behaviour of SnO 2 -RGO nanocomposite emitter has been attributed to synergic effect due to its nanometric dimensions offering high aspect ratio and modulation of electronic properties via formation of heterostructure. The results obtained herein propose the SnO 2 -RGO nanocomposite as a prospective candidate for FE based vacuum microelectronic devices.
Copper phthalocyanine ( CuPc ) is synthesized chemically and used for making CuPc thin films usin... more Copper phthalocyanine ( CuPc ) is synthesized chemically and used for making CuPc thin films using spin coating technique. Films were prepared from trifluroacetic acid (TFA) and chlorobenzene mixed solution on the glass substrate. Spin coated films of unsubstituted CuPc films were heat annealed at 150°C for 2 h duration and were used to study NO 2 gas sensing characteristics. α-phase of CuPc is noted by UV-visible absorption spectra. IR spectra of undoped CuPc films and doped CuPc films with NO 2 revealed that, doping of nitrogen dioxide modifies and deletes some of the bands. The effect of NO 2 at various concentrations from 50 ppm to 500 ppm in atmospheric air at room temperature on the electrical conductivity of CuPc films was studied. Sensitivity, response time and repeatability of the CuPc sensor were discussed in this paper.
Polypyrrole (PPy) nanostructures have been synthesized on indium doped tin oxide (ITO) substrates... more Polypyrrole (PPy) nanostructures have been synthesized on indium doped tin oxide (ITO) substrates by a facile electrochemical route employing cyclic voltammetry (CV) mode. The morphology of the PPy thin films was observed to be influenced by the monomer concentration. Furthermore, FTIR revealed formation of electrically conducting state of PPy. Field emission investigations of the PPy nanostructures were carried out at base pressure of 1×10-8 mbar . The values of turn-on field, corresponding to emission current density of 1 μA/cm2 were observed to be 0.6, 1.0 and 1.2 V/μm for the PPy films characterized with rod-like, cauliflower and granular morphology, respectively. In case of PPy nanorods maximum current density of 1.2 mA/cm2 has been drawn at electric field of 1 V/μm. The low turn on field, extraction of very high emission current density at relatively lower applied field and good emission stability propose the PPy nanorods as a promising material for field emission based devices.
The field emission properties of ion irradiated multiwalled carbon nanotubes (MWCNTs) and doublew... more The field emission properties of ion irradiated multiwalled carbon nanotubes (MWCNTs) and doublewalled carbon nanotubes (DWCNTs) have been studied. The carbon nanotubes synthesized by a chemical vapor deposition method were irradiated by high energy (90 MeV) Au ions with different ion fluence from 4x1011 to 1x1013 ions/cm2 . After ion irradiation, the field emission properties of MWCNTs and DWCNTs were greatly influenced. The change in the emission characteristics is due to structural defects caused by the high energy ion irradiation. The emission characteristic of MWCNTs was improved and turn-on field decreased from 5.43 to 3.10 V/m by ion irradiation. Noticeable improvement in emission characteristics of MWCNTs was observed at a fluence of 1x 10 13 ions/cm2. The emission characteristics of DWCNTs deteriorated and the turn-on field was increased from 2.44 to 7.76 V/m. This results show the distinctly different behavior of ion irradiated MWCNTs and DWCNTs.
Eu3+ doped polymer nanofibers were fabricated by electrospinning technique using various polymers... more Eu3+ doped polymer nanofibers were fabricated by electrospinning technique using various polymers such as poly(vinylidene fluoride) (PVDF), polyethylene oxide (PEO), poly(vinyl pyrrolidone) (PVP) to study the influence of polymer in their photoluminescence properties. As-fabricated nanofibers were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and photoluminescence (PL). Spectral analysis of Polymer/Eu3+ nanofibers was based on their emission spectra. The photoluminescence property shows superior bright red emission spectra from the Eu3+ and relatively stronger hypersensitive behavior of the 5D0 → 7F2 transition. Eu3+ doped polymeric nanofibers are very much suitable for photoluminescent fabric designing in smart textiles. The enhanced properties of this photoluminescence indicated a more polarized chemical environment for the Eu3+ ions and greater hypersensitivity for the 5D0 → 7F2 transition, which showed the potential for application in ...
In the present study, we report a simple method to prepare indium(III) selenide (In2Se3) nanocube... more In the present study, we report a simple method to prepare indium(III) selenide (In2Se3) nanocubes synthesized by laser ablation in aqueous medium. The morphological characterization carried out us...
In the present study, the field emission properties of multi-walled carbon nanotubes (MWCNTs) tre... more In the present study, the field emission properties of multi-walled carbon nanotubes (MWCNTs) treated with laser ablation have been investigated. The MWCNTs were synthesized by chemical vapor deposition method. The laser ablation treatment was performed in liquid medium for laser ablation time of 40 min and 60 min. The morphology of MWCNTs films was characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results exhibit that the field emission properties of MWCNTs are dependent on the laser ablation time. The Raman spectra of laser-ablated MWCNTs clearly showed disorder and increase in graphitic content. The SEM and TEM results clearly revealed the separation of MWCNTs after laser ablation treatment. The field emission characteristics of the MWCNTs showed that the turn-on fields and current density are improved for the nanotubes treated with laser ablation. The enhancement in the field emission characteristics of ...
A new class of emerging materials known as topological insulators (TIs), such as bismuth selenide... more A new class of emerging materials known as topological insulators (TIs), such as bismuth selenide [Formula: see text], has an insulating band gap in the bulk and gapless surface state protected by its intrinsic time-reversal symmetry. These TI materials have attracted great attention because of their possible prospects in electrical and optical applications. In this work, we have prepared the [Formula: see text] nanostructure using the nanosecond (ns) pulse laser ablation in liquid environment to study the field effect transistor behavior. After the laser ablation, [Formula: see text] nanostructures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy to reveal the surface morphology and structural information. The field effect transistor (FET) has been fabricated using [Formula: see text] nanostructure by drop casting [Formula: see text] suspension between two gold electrodes having a gap of 3 [Formula: see text]m on [Formula...
In this study, zinc sulfide (ZnS)/titanium oxide(TiO2) nanoparticles were prepared by a two-step ... more In this study, zinc sulfide (ZnS)/titanium oxide(TiO2) nanoparticles were prepared by a two-step facile hydrothermal method and then annealing at [Formula: see text] for 30 min. Also, the transient absorption measurement and photocatalytic activity of ZnS/TiO2 before and after annealing were investigated. The characterization technique such as the scanning electron microscopy (SEM) and X-ray diffraction (XRD) and UV–Visible spectroscopy have been employed to study the surface morphology and structural details. The SEM image shows the change in the surface morphology due to annealing. The change of the crystal structure of ZnS–TiO2 is revealed by XRD spectra. The femtosecond transient absorption measurement showed moderate decay over several hundred picoseconds for annealed ZnS/TiO2. Moreover, improved photocatalytic activity of annealed ZnS/TiO2 nanoparticles in visible light has been observed.
Novel unique fabrication of ZnO nanoparticles decorated graphene beaded carbon nanofibers (G-CNF)... more Novel unique fabrication of ZnO nanoparticles decorated graphene beaded carbon nanofibers (G-CNF) encapsulated by polyaniline (PANI) nanocomposites through three steps by electrospinning, hydrothermal and in-situ polymerization is reported. As-synthesized G-CNF/ZnO/PANI and CNF/ZnO/PANI nanocomposites were comparatively studied by scanning electron microscopy and electrochemical characterizations for supercapacitor application. Electrochemical measurements of G-CNF/ZnO/PANI electrode revealed the maximum specific capacitance, discharge time, energy density and power density as compared to that of CNF/ZnO/PANI indicating the increase in surface area due to graphene incorporation in electrospinning of carbon nanofibers. The combination of electric double layer charge (EDLC) capacitance from high surface area of G-CNF and pseudo-capacitance from PANI and ZnO nanoparticles facilitates the synergistic effect of ternary components to enhance the electrochemical performance of G-CNF/ZnO/PA...
Abstract Present work portrays the surface morphology dependent electrochemical behaviors tuned b... more Abstract Present work portrays the surface morphology dependent electrochemical behaviors tuned by annealing the chemical bath deposited (CBD) cerium oxide electrodes. The altered nanostructure properties are well-supported by in-depth structural and morphological analysis. Cerium oxide electrode annealed at 200 °C exhibits good surface properties enabling maximum electro-active porous cavities to penetrate electrolyte ions towards enhanced electron transfer. Consequently, the electrode exhibits maximum specific capacitance of 750 F/g with remarkably stable charge-discharge cycles. Fabricated symmetric solid-state supercapacitor device impressively expands potential window to 1.2 V with the aid of PVA-LiClO4 gel electrolyte with a peak specific capacitance of 321.3 F/g with top-up of 61.4 Wh/kg specific energy. The series combination of two devices confirms the strong energy storage ability by glowing ‘VNIT’ acronym designed through 21 red LEDs from the practical point of view.
Abstract We report an eco-friendly green synthesis of highly luminescent CuInS2/ZnS core-shell qu... more Abstract We report an eco-friendly green synthesis of highly luminescent CuInS2/ZnS core-shell quantum dots (QDs) with average particle size ∼ 3.9 nm via solvothermal process. The present study embodies the intensification of CuInS2/ZnS QDs properties by the shell growth on the CuInS2 QDs. The as-prepared CuInS2 core and CuInS2/ZnS core-shell QDs have been characterized using a range of optical and structural techniques. By adopting a low temperature growth of CuInS2 core and high temperature growth of CuInS2/ZnS core-shell growth, the tuning of absorption and photoluminescence emission spectra were observed. Optical absorption and photoluminescence spectroscopy probe the effect of ZnS passivation on the electronic structure of the CuInS2 dots. In addition, QDs have been scrutinized using ultra violet photoelectron spectroscopy (UPS) to explore their electronic band structure. The band level positions of CuInS2 and CuInS2/ZnS QDs suffices the demand of non-toxic acceptor material for electronic devices. The variation in electronic energy levels of CuInS2 core with the coating of wide band gap ZnS shell influence the removal of trap assisted recombination on the surface of the core. QDs exhibited tunable emission from red to orange region. These studies reveal the feasibility of QDs in photovoltaic and light emitting diodes.
Abstract Field emission (FE) properties of hydrothermally synthesized, SnO 2 -RGO nanocomposite h... more Abstract Field emission (FE) properties of hydrothermally synthesized, SnO 2 -RGO nanocomposite have been investigated at a base pressure of 1×10 −8 mbar. The results reveal that the SnO 2 -RGO nanocomposite emitter prevails over the pristine RGO emitter. The values of turn-on field, defined at emission current density of 1 μA/cm 2 , are found to be 1.8 and 2.2 V/μm for the SnO 2 -RGO and pristine RGO emitters, respectively. Furthermore, the SnO 2 -RGO emitter delivers maximum emission current density of ~800 µA/cm 2 at an applied field of 5 V/μm. The observed values of applied field corresponding to emission current densities of 1 μA/cm 2 and 10 µA/cm 2 are superior to those reported for various emitters due to SnO 2 nanostructures and their composites. The emission current at the pre-set value of 1 µA is found to be very stable over a period of 3hrs. The enhanced FE behaviour of SnO 2 -RGO nanocomposite emitter has been attributed to synergic effect due to its nanometric dimensions offering high aspect ratio and modulation of electronic properties via formation of heterostructure. The results obtained herein propose the SnO 2 -RGO nanocomposite as a prospective candidate for FE based vacuum microelectronic devices.
Copper phthalocyanine ( CuPc ) is synthesized chemically and used for making CuPc thin films usin... more Copper phthalocyanine ( CuPc ) is synthesized chemically and used for making CuPc thin films using spin coating technique. Films were prepared from trifluroacetic acid (TFA) and chlorobenzene mixed solution on the glass substrate. Spin coated films of unsubstituted CuPc films were heat annealed at 150°C for 2 h duration and were used to study NO 2 gas sensing characteristics. α-phase of CuPc is noted by UV-visible absorption spectra. IR spectra of undoped CuPc films and doped CuPc films with NO 2 revealed that, doping of nitrogen dioxide modifies and deletes some of the bands. The effect of NO 2 at various concentrations from 50 ppm to 500 ppm in atmospheric air at room temperature on the electrical conductivity of CuPc films was studied. Sensitivity, response time and repeatability of the CuPc sensor were discussed in this paper.
Polypyrrole (PPy) nanostructures have been synthesized on indium doped tin oxide (ITO) substrates... more Polypyrrole (PPy) nanostructures have been synthesized on indium doped tin oxide (ITO) substrates by a facile electrochemical route employing cyclic voltammetry (CV) mode. The morphology of the PPy thin films was observed to be influenced by the monomer concentration. Furthermore, FTIR revealed formation of electrically conducting state of PPy. Field emission investigations of the PPy nanostructures were carried out at base pressure of 1×10-8 mbar . The values of turn-on field, corresponding to emission current density of 1 μA/cm2 were observed to be 0.6, 1.0 and 1.2 V/μm for the PPy films characterized with rod-like, cauliflower and granular morphology, respectively. In case of PPy nanorods maximum current density of 1.2 mA/cm2 has been drawn at electric field of 1 V/μm. The low turn on field, extraction of very high emission current density at relatively lower applied field and good emission stability propose the PPy nanorods as a promising material for field emission based devices.
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Papers by Pankaj Koinkar