Vivek Pachauri | RWTH Aachen University (original) (raw)
Papers by Vivek Pachauri
We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron struc... more We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron structures of ZnO, over gold and silver nanoparticle assemblies, respectively. The structures were grown by a convenient chemical bath deposition method in a nutrient solution made of zinc nitrate (Zn(NO 3 ) 2 AE 6H 2 O) and methyl amine (CH 3 NH 2 ) at low temperature. SEM, XRD, Raman, UV-Vis and fluorescence spectra were used to study the morphology, crystallinity and phase purity of the structures. The ZnO submicron structures were found to be in the hexagonal wurtzite phase.
Chemical Physics Letters, 2006
We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron struc... more We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron structures of ZnO, over gold and silver nanoparticle assemblies, respectively. The structures were grown by a convenient chemical bath deposition method in a nutrient solution made of zinc nitrate (Zn(NO 3 ) 2 AE 6H 2 O) and methyl amine (CH 3 NH 2 ) at low temperature. SEM, XRD, Raman, UV-Vis and fluorescence spectra were used to study the morphology, crystallinity and phase purity of the structures. The ZnO submicron structures were found to be in the hexagonal wurtzite phase.
physica status solidi (a), 2015
In this paper, the use of graphite oxide multilayers as a transducer material for the fabrication... more In this paper, the use of graphite oxide multilayers as a transducer material for the fabrication of electronic devices is outlined. Graphite oxide flakes were produced in a solutionbased exfoliation method optimized for large area thin layers with narrow size distribution. A dielectrophoretic technique was used for scalable trapping of the graphite oxide onto the microelectrode pairs patterned over glass chips. The graphite oxide trapped in between microelectrode gaps was subjected to a very rapid thermal annealing step in ambient in order to make good electrical contacts with source and drain electrodes. After this, the graphite oxide devices were characterized for their electrical transport using impedance spectroscopy and field-effect measurements in an electrochemical gate configuration. The conductivities of the graphite oxide devices were tested against the thermal treatment in air in order to determine a nominal burn-out as well as the optimal parameters for device characteristics. The devices were surface modified with glucose oxidase and deployed for sensor operation. This work suggests for the use of graphite oxide thin-layers as an easy and suitable alternative for the fabrication of electronic sensor platforms circumventing the dependence over tedious chemical and physical graphene oxide reduction methods.
physica status solidi (a), 2015
In this paper, the use of graphite oxide multilayers as a transducer material for the fabrication... more In this paper, the use of graphite oxide multilayers as a transducer material for the fabrication of electronic devices is outlined. Graphite oxide flakes were produced in a solutionbased exfoliation method optimized for large area thin layers with narrow size distribution. A dielectrophoretic technique was used for scalable trapping of the graphite oxide onto the microelectrode pairs patterned over glass chips. The graphite oxide trapped in between microelectrode gaps was subjected to a very rapid thermal annealing step in ambient in order to make good electrical contacts with source and drain electrodes. After this, the graphite oxide devices were characterized for their electrical transport using impedance spectroscopy and field-effect measurements in an electrochemical gate configuration. The conductivities of the graphite oxide devices were tested against the thermal treatment in air in order to determine a nominal burn-out as well as the optimal parameters for device characteristics. The devices were surface modified with glucose oxidase and deployed for sensor operation. This work suggests for the use of graphite oxide thin-layers as an easy and suitable alternative for the fabrication of electronic sensor platforms circumventing the dependence over tedious chemical and physical graphene oxide reduction methods.
Chemical Physics Letters, 2011
We study chemical bath deposition method for synthesizing large variety constructions of ZnO nano... more We study chemical bath deposition method for synthesizing large variety constructions of ZnO nanostructures. By varying reaction kinetics we control the shape, size and morphology to yield flower-like, rolling-pin-like, viscous-fingers-like and antenna-like structures. In solution-based methods, factors responsible for crystal growth are largely affected by slight changes in the reaction processes/conditions and cause different hierarchical architectures when very low concentrations of precursor material used. The ability to grow different morphologies just by controlling solution growth parameters may open up new avenues to solution growth and provide systems to study natural growth behavior of materials as well as their novel applications.
Small, 2010
A scalable bottom-up solution-based approach for the site-specific realization of ZnO nanowire (Z... more A scalable bottom-up solution-based approach for the site-specific realization of ZnO nanowire (ZnO-NW)-based field-effect transistors for sensing applications in liquids is reported. The nanowires are grown across predefined electrodes patterned by photolithography. Site specificity is attained by the use of nanoparticles acting as seeds. Using integrated on-chip microchannels and microfabricated gate electrodes, electrochemically gated ZnO-NW network transistors functioning in liquids are demonstrated. The optimized devices are rendered sensitive to pH through chemical functionalization. The unique combination of the sensitivity, site specificity, scalability, and cost effectiveness of the technique opens up avenues for the routine realization of one-dimensional nanostructure-based chemical and biosensors for analytical and diagnostic applications.
physica status solidi (a), 2014
ABSTRACT Graphene, with its unique electrical properties and biocompatibility, has become a mater... more ABSTRACT Graphene, with its unique electrical properties and biocompatibility, has become a material of choice for the development of biosensor platforms. In this study, a microelectrode array based on reduced graphene oxide (rGO) was constructed and used as a platform for electrical monitoring of cell–substrate adhesion. The rGO-based sensor arrays were designed in order to facilitate sensor pads comparable to the size of individual cells. The sensor chips were fabricated in a scalable manner via site-specific immobilization of graphene oxide flakes onto microelectrode pairs followed by reduction to rGO. The sensor chips were mounted on a measurement platform equipped with a fluidic cell. Electrical characteristics were recorded and field-effect behavior was confirmed. Sensors reacted to changes of pH value in the solution. Finally, as a proof-of-concept, the graphene oxide-based sensing platform was used for electrical cell–substrate impedance sensing of individual HEK293 cells in culture. Schematic view of the rGO-based sensor chip for electrical cell–substrate adhesion assays.
Chemical Physics Letters, 2010
We study chemical bath deposition method for synthesizing large variety constructions of ZnO nano... more We study chemical bath deposition method for synthesizing large variety constructions of ZnO nanostructures. By varying reaction kinetics we control the shape, size and morphology to yield flower-like, rolling-pin-like, viscous-fingers-like and antenna-like structures. In solution-based methods, factors responsible for crystal growth are largely affected by slight changes in the reaction processes/conditions and cause different hierarchical architectures when very low concentrations of precursor material used. The ability to grow different morphologies just by controlling solution growth parameters may open up new avenues to solution growth and provide systems to study natural growth behavior of materials as well as their novel applications.
Applied Physics Letters, 2013
ABSTRACT A new class of nanoscale devices called ion-sensitive metal-semiconductor field-effect t... more ABSTRACT A new class of nanoscale devices called ion-sensitive metal-semiconductor field-effect transistors (nano-IS-MESFET) for sensing applications is reported. Nanoparticle-nanowire hybrids with active metal-semiconductor regions are operated as ion-sensitive field-effect transistors (ISFETs) in liquids, where 0D metal gates induce quasi-spherical charge depletion regions in 1D transport channel producing stronger field-effects. As a proof-of-concept, we present ZnO nanowire-Pd/Au nanoparticle IS-MESFETs that show increased transconductance in comparison to ZnO nanowire ISFETs. As demonstrated further, ISMESFETs may also provide strategies for site-specific immobilization of receptor molecules paving way towards a novel electrical biosensing platform operable at low voltages with improved selectivity and sensitivity.
physica status solidi (a), 2013
We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron struc... more We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron structures of ZnO, over gold and silver nanoparticle assemblies, respectively. The structures were grown by a convenient chemical bath deposition method in a nutrient solution made of zinc nitrate (Zn(NO 3 ) 2 AE 6H 2 O) and methyl amine (CH 3 NH 2 ) at low temperature. SEM, XRD, Raman, UV-Vis and fluorescence spectra were used to study the morphology, crystallinity and phase purity of the structures. The ZnO submicron structures were found to be in the hexagonal wurtzite phase.
Chemical Physics Letters, 2006
We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron struc... more We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron structures of ZnO, over gold and silver nanoparticle assemblies, respectively. The structures were grown by a convenient chemical bath deposition method in a nutrient solution made of zinc nitrate (Zn(NO 3 ) 2 AE 6H 2 O) and methyl amine (CH 3 NH 2 ) at low temperature. SEM, XRD, Raman, UV-Vis and fluorescence spectra were used to study the morphology, crystallinity and phase purity of the structures. The ZnO submicron structures were found to be in the hexagonal wurtzite phase.
physica status solidi (a), 2015
In this paper, the use of graphite oxide multilayers as a transducer material for the fabrication... more In this paper, the use of graphite oxide multilayers as a transducer material for the fabrication of electronic devices is outlined. Graphite oxide flakes were produced in a solutionbased exfoliation method optimized for large area thin layers with narrow size distribution. A dielectrophoretic technique was used for scalable trapping of the graphite oxide onto the microelectrode pairs patterned over glass chips. The graphite oxide trapped in between microelectrode gaps was subjected to a very rapid thermal annealing step in ambient in order to make good electrical contacts with source and drain electrodes. After this, the graphite oxide devices were characterized for their electrical transport using impedance spectroscopy and field-effect measurements in an electrochemical gate configuration. The conductivities of the graphite oxide devices were tested against the thermal treatment in air in order to determine a nominal burn-out as well as the optimal parameters for device characteristics. The devices were surface modified with glucose oxidase and deployed for sensor operation. This work suggests for the use of graphite oxide thin-layers as an easy and suitable alternative for the fabrication of electronic sensor platforms circumventing the dependence over tedious chemical and physical graphene oxide reduction methods.
physica status solidi (a), 2015
In this paper, the use of graphite oxide multilayers as a transducer material for the fabrication... more In this paper, the use of graphite oxide multilayers as a transducer material for the fabrication of electronic devices is outlined. Graphite oxide flakes were produced in a solutionbased exfoliation method optimized for large area thin layers with narrow size distribution. A dielectrophoretic technique was used for scalable trapping of the graphite oxide onto the microelectrode pairs patterned over glass chips. The graphite oxide trapped in between microelectrode gaps was subjected to a very rapid thermal annealing step in ambient in order to make good electrical contacts with source and drain electrodes. After this, the graphite oxide devices were characterized for their electrical transport using impedance spectroscopy and field-effect measurements in an electrochemical gate configuration. The conductivities of the graphite oxide devices were tested against the thermal treatment in air in order to determine a nominal burn-out as well as the optimal parameters for device characteristics. The devices were surface modified with glucose oxidase and deployed for sensor operation. This work suggests for the use of graphite oxide thin-layers as an easy and suitable alternative for the fabrication of electronic sensor platforms circumventing the dependence over tedious chemical and physical graphene oxide reduction methods.
Chemical Physics Letters, 2011
We study chemical bath deposition method for synthesizing large variety constructions of ZnO nano... more We study chemical bath deposition method for synthesizing large variety constructions of ZnO nanostructures. By varying reaction kinetics we control the shape, size and morphology to yield flower-like, rolling-pin-like, viscous-fingers-like and antenna-like structures. In solution-based methods, factors responsible for crystal growth are largely affected by slight changes in the reaction processes/conditions and cause different hierarchical architectures when very low concentrations of precursor material used. The ability to grow different morphologies just by controlling solution growth parameters may open up new avenues to solution growth and provide systems to study natural growth behavior of materials as well as their novel applications.
Small, 2010
A scalable bottom-up solution-based approach for the site-specific realization of ZnO nanowire (Z... more A scalable bottom-up solution-based approach for the site-specific realization of ZnO nanowire (ZnO-NW)-based field-effect transistors for sensing applications in liquids is reported. The nanowires are grown across predefined electrodes patterned by photolithography. Site specificity is attained by the use of nanoparticles acting as seeds. Using integrated on-chip microchannels and microfabricated gate electrodes, electrochemically gated ZnO-NW network transistors functioning in liquids are demonstrated. The optimized devices are rendered sensitive to pH through chemical functionalization. The unique combination of the sensitivity, site specificity, scalability, and cost effectiveness of the technique opens up avenues for the routine realization of one-dimensional nanostructure-based chemical and biosensors for analytical and diagnostic applications.
physica status solidi (a), 2014
ABSTRACT Graphene, with its unique electrical properties and biocompatibility, has become a mater... more ABSTRACT Graphene, with its unique electrical properties and biocompatibility, has become a material of choice for the development of biosensor platforms. In this study, a microelectrode array based on reduced graphene oxide (rGO) was constructed and used as a platform for electrical monitoring of cell–substrate adhesion. The rGO-based sensor arrays were designed in order to facilitate sensor pads comparable to the size of individual cells. The sensor chips were fabricated in a scalable manner via site-specific immobilization of graphene oxide flakes onto microelectrode pairs followed by reduction to rGO. The sensor chips were mounted on a measurement platform equipped with a fluidic cell. Electrical characteristics were recorded and field-effect behavior was confirmed. Sensors reacted to changes of pH value in the solution. Finally, as a proof-of-concept, the graphene oxide-based sensing platform was used for electrical cell–substrate impedance sensing of individual HEK293 cells in culture. Schematic view of the rGO-based sensor chip for electrical cell–substrate adhesion assays.
Chemical Physics Letters, 2010
We study chemical bath deposition method for synthesizing large variety constructions of ZnO nano... more We study chemical bath deposition method for synthesizing large variety constructions of ZnO nanostructures. By varying reaction kinetics we control the shape, size and morphology to yield flower-like, rolling-pin-like, viscous-fingers-like and antenna-like structures. In solution-based methods, factors responsible for crystal growth are largely affected by slight changes in the reaction processes/conditions and cause different hierarchical architectures when very low concentrations of precursor material used. The ability to grow different morphologies just by controlling solution growth parameters may open up new avenues to solution growth and provide systems to study natural growth behavior of materials as well as their novel applications.
Applied Physics Letters, 2013
ABSTRACT A new class of nanoscale devices called ion-sensitive metal-semiconductor field-effect t... more ABSTRACT A new class of nanoscale devices called ion-sensitive metal-semiconductor field-effect transistors (nano-IS-MESFET) for sensing applications is reported. Nanoparticle-nanowire hybrids with active metal-semiconductor regions are operated as ion-sensitive field-effect transistors (ISFETs) in liquids, where 0D metal gates induce quasi-spherical charge depletion regions in 1D transport channel producing stronger field-effects. As a proof-of-concept, we present ZnO nanowire-Pd/Au nanoparticle IS-MESFETs that show increased transconductance in comparison to ZnO nanowire ISFETs. As demonstrated further, ISMESFETs may also provide strategies for site-specific immobilization of receptor molecules paving way towards a novel electrical biosensing platform operable at low voltages with improved selectivity and sensitivity.
physica status solidi (a), 2013