Sanju Gupta - Academia.edu (original) (raw)
Papers by Sanju Gupta
Bulletin of the American Physical Society, Nov 17, 2017
Submitted for the SES17 Meeting of The American Physical Society Salt-Assisted Ultrasonicated De-... more Submitted for the SES17 Meeting of The American Physical Society Salt-Assisted Ultrasonicated De-aggregation and Advanced Electrochemistry of Detonation Nanodiamond. 1 SANJU GUPTA, B. EVANS, A. HENSON, Western Kentucky University-Nanoparticles in dry powder state form agglomerates thus reducing surface energy and accessibility of diamond core impacting technological advancement. In this work, we investigated a facile, cost-effective and contaminant-free salt-assisted ultrasonic de-agglomeration method for detonation nanodiamond, NDs. Utilizing ultrasound energy to break apart two different sourced and thermally treated nanodiamond mesoscale aggregates in sodium chloride and sodium acetate salts, this technique produced aqueous slurry of isolated or single-digit (<10 nm) stable colloidal dispersions by virtue of ionic interactions and electrostatic destabilization. Moreover, the technique is well-suited for materials engineering (composites, lubricants) and biomedical (bio-labelling, biosensing) applications. We characterized microscopic structure and performed advanced electrochemistry by immobilizing processed NDs on boron-doped diamond to study surface redox chemistry, determine surface potential (or Fermi level), carrier density and to image electrocatalytic activity by scanning electrochemical microscopy and the results are compared to those untreated aggregated nanodiamond particles. The findings are discussed in terms of surface functionality and defect sites that give rise to surface states within bandgap. These surface states may serve as electron donors (or acceptors) depending upon bonding (or antibonding) character suitable for various electrocatalytic redox processes.
Bulletin of the American Physical Society, Nov 17, 2017
this work, we developed large-area nanofiltration membranes using 1) shear aligned discotic nemat... more this work, we developed large-area nanofiltration membranes using 1) shear aligned discotic nematic phase of graphene oxide and 2) holey graphenes with narrow hole size distribution via controlled catalytic oxidation. We also prepared interconnected network of mesoporous graphene-based electrodes to achieve optimal desalination during capacitive deionization (CDI) of brackish water, attributed to higher specific surface area, electrical conductivity, good wettability of water, environmentally safe, efficient pathways for ion and electron transportation, as potential successor of current filtration membranes. The pressure driven transport data on highly ordered, continuous, thin films of multi-layered graphene oxide and holey graphene is expected to demonstrate faster transport for salt water, higher retention for charged and uncharged organic probe molecules with hydrated radii above 5Å as well as modest retention of mono-and di-valent salts for˜150 nm thick membranes. The highly ordered graphene nanosheets and nanoscaled porous graphene in the plane of the membrane make organized, molecule-hugging cylindrical and spherical channels, respectively, thus enhance the permeability and hydrodynamic conductivity. The results illustrate that both the macro and nanoscale pores are favorable for enhancing CDI performance by buffering ions to reduce the diffusion distance from external electrolyte to the interior surfaces and enlarging surface area.
Bulletin of the American Physical Society, Mar 14, 2017
Background and Motivation Organic and inorganic nanoparticle reinforcements have garnered widespr... more Background and Motivation Organic and inorganic nanoparticle reinforcements have garnered widespread attention for polymer nanocomposites to yield properties enhancement useful for wide ranging modern technologies including photovoltaics, catalysis, optics, and renewable energy. Recent experiments and computational simulations revealed the macroscopic properties are governed by mesoscale structure and interfacial layer dynamics due to the interactions between the polymer matrix (host) and nanoparticle reinforcements (guest). However, a clear fundamental understanding of the role of size, shape, loading (volume fraction) in controlling the structure and dynamics of polymernanoparticle interfacial layer is limited. Moreover, 'forward' engineered polymer-nanoparticle composites targeting specific applications often require higher volumetric density and better dispersions remains a challenging task. We report on developing polymer nanocomposites engineered to minimize dielectric losses and investigating structure and dynamics of interfacial layer to predict macroscale properties. Approach We prepared a series of solution cast P2VP-based nanocomposites with (1) Graphene Nanoribbons (GNR), (2) organic/inorganic N-POSS caged molecule and (3) graphene oxide (GO) with various concentrations.
Chemical Physics, 2013
The profile structure of a hybrid lipid bilayer, tethered to the surface of an inorganic substrat... more The profile structure of a hybrid lipid bilayer, tethered to the surface of an inorganic substrate and fully hydrated with a bulk aqueous medium in an electrochemical cell, was investigated as a function of the applied transbilayer electric potential via time-resolved neutron reflectivity, enhanced by interferometry. Significant, and fully reversible structural changes were observed in the distal half (with respect to the substrate surface) of the hybrid bilayer comprised of a zwitterionic phospholipid in response to a +100mV potential with respect to 0mV. These arise presumably due to reorientation of the electric dipole present in the polar headgroup of the phospholipid and its resulting effect on the thickness of the phospholipid's hydrocarbon chain layer within the hybrid bilayer's profile structure. The profile structure of the voltage-sensor domain from a voltage-gated ion channel protein within a phospholipid bilayer membrane, tethered to the surface of an inorganic substrate and fully hydrated with a bulk aqueous medium in an electrochemical cell, was also investigated as a function of the applied transmembrane electric potential via time-resolved X-ray reflectivity, enhanced by interferometry. Significant, fullyreversible, and different structural changes in the protein were detected in response to ±100mV potentials with respect to 0mV. The approach employed is that typical of transient spectroscopy, shown here to be applicable to both neutron and X-ray reflectivity of thin films.
Biosensors
In order to ensure the health and welfare of livestock, there has been an emphasis on precision f... more In order to ensure the health and welfare of livestock, there has been an emphasis on precision farming of ruminant animals. Monitoring the life index of ruminant animals is of importance for intelligent farming. Here, a wearable sensor for monitoring ultraviolet (UV) radiation is demonstrated to understand the effect of primary and secondary photosensitization on dairy animals. Thin films of wide bandgap semiconductor zinc oxide (ZnO) comprising multilevel of nanostructures from microparticles (MP) to nanoparticles (NP), and tetrapod (T–ZnO), were prepared as the UV sensing active materials. The sensitivity was evaluated by exposing the films to various radiation sources, i.e., 365 nm (UV A), 302 nm (UV B), and 254 nm (UV C), and measuring the electrical resistance change. T–ZnO is found to exhibit higher sensitivity and stable response (on/off) upon exposure to UV A and UV B radiation, which is attributed to their higher surface area, aspect ratio, porosity, and interconnective ne...
Bulletin of the American Physical Society, 2017
Elucidation of microscopic properties of a synthetic diamond, such as formation and evolution of ... more Elucidation of microscopic properties of a synthetic diamond, such as formation and evolution of bulk and surface defects, chemistry of dopants, etc. is necessary for a reliable quality control and reproducibility in applications. Employing surface photovoltage (SPV) and photoluminescence (PL) spectroscopic probes we studied diamond thin films grown on silicon by microwave plasma-assisted chemical vapor deposition with different levels of boron doping in conjunction with gamma irradiation. SPV measurements showed that while the increase of boron concentration leads to a semiconductor-metal transition, subsequent intense gamma irradiation reverts back the quasi-metallic samples to semiconducting state via compensating electrical activity of boron by hydrogen. One of the most pronounced common transitions in the SPV spectra was observed at ∼3.1 eV, also present in most of the PL spectra. We argue that this is a signature of the sp 2-C clusters/layers in the vicinity of grain boundaries.
Journal of Electroanalytical Chemistry, 2020
In the following work we describe preparation and the electrochemical performance of thin and fre... more In the following work we describe preparation and the electrochemical performance of thin and free-standing heavy boron-doped diamond (BDD) nanosheets. The investigated foils were deposited on Ta substrate using microwave plasma-enhanced chemical vapor deposition technique (MPECVD). Foils of two B-dopant densities were investigated, obtained on the base of 10 k and 20 k ppm [B]/[C] ratio in the gas admixture. The obtained foils can be easily peeled from substrate in deionized water to be then attached to other material, in this case polydimethylsiloxane (PDMS). We have shown that the top surface and the bottom side of investigated boron-doped diamond nanosheet possess significantly altered morphology and physico-chemical properties, revealed by electron microscopy, Raman spectroscopy and electrochemistry. The voltammetric response of investigated BDD foils as working electrodes indicates the highest activity for the nanosheet with higher dopant concentration, in particular on its top surface. Furthermore, electrodes are characterized with altered kinetics, characteristic for partially blocked electrodes with quasi-reversible charge transfer.
Applied Physics Letters, 2008
Nanocrystal-assembled cubic boron nitride (cBN) islands are formed by using low-energy (∼20eV) io... more Nanocrystal-assembled cubic boron nitride (cBN) islands are formed by using low-energy (∼20eV) ion irradiation in an inductively coupled fluorine-containing plasma. The temporal evolution of surface morphology and roughness reveals three-dimensional island growth for initial sp2-bonded BN and subsequent cBN, accompanied by a high frequency of renucleation. The formation of cBN islands enhances the field emission and reduces the turn-on field down to around 9V∕μm due to an increase in the island-related field. The results demonstrate the high potential of cBN for field emitters, comparable to other wide band gap semiconductors.
Journal of Applied Physics, 2019
Electroactivity of graphene-family nanomaterials and three-dimensional porous architectures is ke... more Electroactivity of graphene-family nanomaterials and three-dimensional porous architectures is key for various applications at the grand challenges of “energy-water-sensing nexus.” It requires well-controlled morphology, manipulation of surface chemistry, interconnected topologic network, as well as electronic properties. Here, we demonstrate by taking advantage of hierarchical mesoporosity, optimized defects number density, nD (edges-plane and pore sites, oxygenated and nitrogenated functionalities), further invoked by synergistic coupling between one-dimensional single-walled carbon nanotube (SWCNT) as “nano” spacers and polymer linker with two-dimensional reduced graphene oxide derived three-dimensional scaffolds (known as aerogels) under hydrothermal conditions, and improved electrochemical (re)activity by enhancing the heterogeneous electron transfer rate (kET). We determined the correlation among nD, in-plane sp2C cluster, La and interdefect distance, LD (all via Raman spectro...
Journal of Materials Research, 2016
We report the development of hybrids consisting of supercapacitive graphene oxide (GO), reduced G... more We report the development of hybrids consisting of supercapacitive graphene oxide (GO), reduced GO (rGO), electrochemically reduced GO (ErGO), multilayer graphene (MLG) decorated with pseudocapacitive nanostructured cobalt oxides (CoO, Co 3 O 4 ) and nanoparticles (CoNP) via electrodeposition and hydrothermal synthesis facilitating chemically bridged (covalently and electrostatically anchored) interfaces with tunable properties. These hybrid samples showed heterogeneous transport behavior determining diffusion coefficient (4 × 10 −8 –6 × 10 −6 m 2 /s) following CoO/MLG 3 O 4 /MLG 3 O 4 /rGO HT 550 F/g for Co 3 O 4 /ErGO and Co 3 O 4 /MLG. We found an ultrahigh sensitivity of 4.57 mA/(mM cm 2 ) and excellent limit of glucose detection 3 O 4 /rGO HT 3 O 4 /MLG. These findings are due to open pore network and topologically multiplexed conductive pathways provided by graphene nanoscaffolds to ensure rapid charge transfer and ion conduction. Density functional theory determined density of states in the vicinity of Fermi level in-turn providing contribution toward electroactivity due to orbital re-hybridization.
Physical Review Letters, 2010
Quasistationary states are long-lived nonequilibrium states, observed in some systems with longra... more Quasistationary states are long-lived nonequilibrium states, observed in some systems with longrange interactions under deterministic Hamiltonian evolution. These intriguing non-Boltzmann states relax to equilibrium over times which diverge algebraically with the system size. To test the robustness of this phenomenon to nondeterministic dynamical processes, we have generalized the paradigmatic model exhibiting such a behavior, the Hamiltonian mean-field model, to include energy-conserving stochastic processes. Analysis, based on the Boltzmann equation, a scaling approach, and numerical studies, demonstrates that in the long time limit the system relaxes to the equilibrium state on time scales which do not diverge algebraically with the system size. Thus, quasistationarity takes place only as a crossover phenomenon on times determined by the strength of the stochastic process.
In this paper, we explain the concept, characteristics and need of big data and different offerin... more In this paper, we explain the concept, characteristics and need of big data and different offerings available in the market to explore unstructured large data. This paper covers big data adoption trends, entry and exit criteria for the vendor and product selection, best practices, customer success story, benefits of big data analytics, summary and conclusion. Our analysis illustrates that the big data analytics is a fast-growing, influential practice and a key enabler for the social business. The insights gained from the user generated online contents and collaboration with customers is critical for success in the age of social media.
Journal of Electronic Materials, 2020
Two-dimensional (2D) layered materials are studied in efforts to discover new compounds and for t... more Two-dimensional (2D) layered materials are studied in efforts to discover new compounds and for their fascinating properties engendered by their sheet-like structure and tunable surfaces. MXenes are an emergent class of layered, synthesized transition metal carbides and carbonitrides that are useful in addressing the formidable challenges of sensing at the energy-water nexus. This work reports systematic structural and electrochemical properties of titanium carbide (Ti 3 C 2 T x) MXenes revealed by varying interlayer spacing, flake thickness and lateral size under different electrolytes. In addition to traditional electrode kinetics, we utilized surface sensitive scanning electrochemical microscopy (SECM) to gain a more complete understanding of rich MXene surface chemistry and corresponding knowledge about the physicochemical processes, including inherent electrochemistry and heterogeneous charge transfer characteristics, at electrode/electrolyte (solid/liquid) interfaces. We employed electron microscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, x-ray diffraction, and Raman spectroscopy to determine surface morphology, microscopic and electronic structure and lattice vibrational properties. It is shown that Ti 3 C 2 T x or, specifically, transition metal Ti, undergoes irreversible oxidation and lithiation in a positive potential window, which strongly depends on the flake thickness and type (aqueous versus organic) of the electrolyte. Multi-layered and smaller Ti 3 C 2 T x flakes exhibit faster electron transfer kinetics (k ET = 1.2 cm s À1) with a potassium ferrocyanide [Fe(CN) 6 ] 4À/3À redox probe, compared to few-layered Ti 3 C 2 T x (k ET = 0.3 cm s À1) in aqueous and organic electrolyte (k ET = 4.9 cm s À1) with a [Fe(CN) 6 ] 4À/3À redox probe, and compared to a few-layered Ti 3 C 2 T x (k ET = 0.9 cm s À1). In addition, the few-layered free standing Ti 3 C 2 T x film electrode remains intact following irreversible oxidation. These properties help to establish structure-property-electroactivity relationships among different types of Ti 3 C 2 T x MXenes.
Nano-Structures & Nano-Objects, 2017
h i g h l i g h t s • FRET biosensor based on aptamer/functionalized graphene for ultrasensitive ... more h i g h l i g h t s • FRET biosensor based on aptamer/functionalized graphene for ultrasensitive detection of bisphenol A. • Qualitative and quantitative detection of BPA were successfully elucidated and realized with limit of detection <1 pg/mL by assessing the change followed by recovery of fluorescent intensity on BPA addition. • We applied the developed sensor for real water (river water, drinking mineral water and tap water) samples because of its facile preparation and manipulation, scalability and excellent performance with good recovery. • The specificity is evaluated by measuring the fluorescent intensity change with BPA analogs (BP, BPB, BPC and DES) for benchmarking this biosensor.
Symmetries and Quark Models, 1970
MRS Proceedings, 2006
ABSTRACTCarbon nanotubes (CNTs) are of great interest because of several unsurpassable physical (... more ABSTRACTCarbon nanotubes (CNTs) are of great interest because of several unsurpassable physical (mechanical, electrical, thermal, and chemical) properties. Especially their large elastic modulus and breaking strength make them highly attractive for their use as reinforced agents in forming a new class of multifunctional advanced materials - onanocomposites, in addition to high conductivity (either in semiconducting or metallic regimes) achieved through lower percolation thresholds for several electronic applications. Among the known conducting polymers, polyaniline (PANI) has a high potential due to its ease of synthesis, excellent environmental, and thermal stability and reversible control of its electrical/electronic properties. In this work, PANI-single-/multiwalled NTs composites films containing different nanotube content of both kinds were synthesized by spin-cast preceded by ultrasonic mixing of the constituents. They were characterized using complementary techniques includin...
MRS Proceedings, 2006
ABSTRACTRelaxors (PZN, in particular) is an important class of self-assembled nanostructure compo... more ABSTRACTRelaxors (PZN, in particular) is an important class of self-assembled nanostructure composite ferroelectric oxides (or perovskite) materials. The interesting features associated with the nanoregions/nanodomains required to describe these relaxors give rise to the most relevant device related characteristics and peculiar physical properties in these materials. In addition, they possess astronomical property coefficients by themselves or when modified with lead titanate (PT) forming solid solution. In the past, we conducted temperature dependent Raman scattering studies on solid solution (1−x)PZN−xPT relaxors single crystals with varying composition; x = 0.02, 0.085, and 0.11. These studies were performed to obtain relevant information about lattice/phonon dynamics for matching the application criteria such as electromechanical actuators. We showed that the sharp structural phase transition occurs at or near 460 K which is a first-order transition by fitting two spectroscopic ...
Bulletin of the American Physical Society, Nov 17, 2017
Submitted for the SES17 Meeting of The American Physical Society Salt-Assisted Ultrasonicated De-... more Submitted for the SES17 Meeting of The American Physical Society Salt-Assisted Ultrasonicated De-aggregation and Advanced Electrochemistry of Detonation Nanodiamond. 1 SANJU GUPTA, B. EVANS, A. HENSON, Western Kentucky University-Nanoparticles in dry powder state form agglomerates thus reducing surface energy and accessibility of diamond core impacting technological advancement. In this work, we investigated a facile, cost-effective and contaminant-free salt-assisted ultrasonic de-agglomeration method for detonation nanodiamond, NDs. Utilizing ultrasound energy to break apart two different sourced and thermally treated nanodiamond mesoscale aggregates in sodium chloride and sodium acetate salts, this technique produced aqueous slurry of isolated or single-digit (<10 nm) stable colloidal dispersions by virtue of ionic interactions and electrostatic destabilization. Moreover, the technique is well-suited for materials engineering (composites, lubricants) and biomedical (bio-labelling, biosensing) applications. We characterized microscopic structure and performed advanced electrochemistry by immobilizing processed NDs on boron-doped diamond to study surface redox chemistry, determine surface potential (or Fermi level), carrier density and to image electrocatalytic activity by scanning electrochemical microscopy and the results are compared to those untreated aggregated nanodiamond particles. The findings are discussed in terms of surface functionality and defect sites that give rise to surface states within bandgap. These surface states may serve as electron donors (or acceptors) depending upon bonding (or antibonding) character suitable for various electrocatalytic redox processes.
Bulletin of the American Physical Society, Nov 17, 2017
this work, we developed large-area nanofiltration membranes using 1) shear aligned discotic nemat... more this work, we developed large-area nanofiltration membranes using 1) shear aligned discotic nematic phase of graphene oxide and 2) holey graphenes with narrow hole size distribution via controlled catalytic oxidation. We also prepared interconnected network of mesoporous graphene-based electrodes to achieve optimal desalination during capacitive deionization (CDI) of brackish water, attributed to higher specific surface area, electrical conductivity, good wettability of water, environmentally safe, efficient pathways for ion and electron transportation, as potential successor of current filtration membranes. The pressure driven transport data on highly ordered, continuous, thin films of multi-layered graphene oxide and holey graphene is expected to demonstrate faster transport for salt water, higher retention for charged and uncharged organic probe molecules with hydrated radii above 5Å as well as modest retention of mono-and di-valent salts for˜150 nm thick membranes. The highly ordered graphene nanosheets and nanoscaled porous graphene in the plane of the membrane make organized, molecule-hugging cylindrical and spherical channels, respectively, thus enhance the permeability and hydrodynamic conductivity. The results illustrate that both the macro and nanoscale pores are favorable for enhancing CDI performance by buffering ions to reduce the diffusion distance from external electrolyte to the interior surfaces and enlarging surface area.
Bulletin of the American Physical Society, Mar 14, 2017
Background and Motivation Organic and inorganic nanoparticle reinforcements have garnered widespr... more Background and Motivation Organic and inorganic nanoparticle reinforcements have garnered widespread attention for polymer nanocomposites to yield properties enhancement useful for wide ranging modern technologies including photovoltaics, catalysis, optics, and renewable energy. Recent experiments and computational simulations revealed the macroscopic properties are governed by mesoscale structure and interfacial layer dynamics due to the interactions between the polymer matrix (host) and nanoparticle reinforcements (guest). However, a clear fundamental understanding of the role of size, shape, loading (volume fraction) in controlling the structure and dynamics of polymernanoparticle interfacial layer is limited. Moreover, 'forward' engineered polymer-nanoparticle composites targeting specific applications often require higher volumetric density and better dispersions remains a challenging task. We report on developing polymer nanocomposites engineered to minimize dielectric losses and investigating structure and dynamics of interfacial layer to predict macroscale properties. Approach We prepared a series of solution cast P2VP-based nanocomposites with (1) Graphene Nanoribbons (GNR), (2) organic/inorganic N-POSS caged molecule and (3) graphene oxide (GO) with various concentrations.
Chemical Physics, 2013
The profile structure of a hybrid lipid bilayer, tethered to the surface of an inorganic substrat... more The profile structure of a hybrid lipid bilayer, tethered to the surface of an inorganic substrate and fully hydrated with a bulk aqueous medium in an electrochemical cell, was investigated as a function of the applied transbilayer electric potential via time-resolved neutron reflectivity, enhanced by interferometry. Significant, and fully reversible structural changes were observed in the distal half (with respect to the substrate surface) of the hybrid bilayer comprised of a zwitterionic phospholipid in response to a +100mV potential with respect to 0mV. These arise presumably due to reorientation of the electric dipole present in the polar headgroup of the phospholipid and its resulting effect on the thickness of the phospholipid's hydrocarbon chain layer within the hybrid bilayer's profile structure. The profile structure of the voltage-sensor domain from a voltage-gated ion channel protein within a phospholipid bilayer membrane, tethered to the surface of an inorganic substrate and fully hydrated with a bulk aqueous medium in an electrochemical cell, was also investigated as a function of the applied transmembrane electric potential via time-resolved X-ray reflectivity, enhanced by interferometry. Significant, fullyreversible, and different structural changes in the protein were detected in response to ±100mV potentials with respect to 0mV. The approach employed is that typical of transient spectroscopy, shown here to be applicable to both neutron and X-ray reflectivity of thin films.
Biosensors
In order to ensure the health and welfare of livestock, there has been an emphasis on precision f... more In order to ensure the health and welfare of livestock, there has been an emphasis on precision farming of ruminant animals. Monitoring the life index of ruminant animals is of importance for intelligent farming. Here, a wearable sensor for monitoring ultraviolet (UV) radiation is demonstrated to understand the effect of primary and secondary photosensitization on dairy animals. Thin films of wide bandgap semiconductor zinc oxide (ZnO) comprising multilevel of nanostructures from microparticles (MP) to nanoparticles (NP), and tetrapod (T–ZnO), were prepared as the UV sensing active materials. The sensitivity was evaluated by exposing the films to various radiation sources, i.e., 365 nm (UV A), 302 nm (UV B), and 254 nm (UV C), and measuring the electrical resistance change. T–ZnO is found to exhibit higher sensitivity and stable response (on/off) upon exposure to UV A and UV B radiation, which is attributed to their higher surface area, aspect ratio, porosity, and interconnective ne...
Bulletin of the American Physical Society, 2017
Elucidation of microscopic properties of a synthetic diamond, such as formation and evolution of ... more Elucidation of microscopic properties of a synthetic diamond, such as formation and evolution of bulk and surface defects, chemistry of dopants, etc. is necessary for a reliable quality control and reproducibility in applications. Employing surface photovoltage (SPV) and photoluminescence (PL) spectroscopic probes we studied diamond thin films grown on silicon by microwave plasma-assisted chemical vapor deposition with different levels of boron doping in conjunction with gamma irradiation. SPV measurements showed that while the increase of boron concentration leads to a semiconductor-metal transition, subsequent intense gamma irradiation reverts back the quasi-metallic samples to semiconducting state via compensating electrical activity of boron by hydrogen. One of the most pronounced common transitions in the SPV spectra was observed at ∼3.1 eV, also present in most of the PL spectra. We argue that this is a signature of the sp 2-C clusters/layers in the vicinity of grain boundaries.
Journal of Electroanalytical Chemistry, 2020
In the following work we describe preparation and the electrochemical performance of thin and fre... more In the following work we describe preparation and the electrochemical performance of thin and free-standing heavy boron-doped diamond (BDD) nanosheets. The investigated foils were deposited on Ta substrate using microwave plasma-enhanced chemical vapor deposition technique (MPECVD). Foils of two B-dopant densities were investigated, obtained on the base of 10 k and 20 k ppm [B]/[C] ratio in the gas admixture. The obtained foils can be easily peeled from substrate in deionized water to be then attached to other material, in this case polydimethylsiloxane (PDMS). We have shown that the top surface and the bottom side of investigated boron-doped diamond nanosheet possess significantly altered morphology and physico-chemical properties, revealed by electron microscopy, Raman spectroscopy and electrochemistry. The voltammetric response of investigated BDD foils as working electrodes indicates the highest activity for the nanosheet with higher dopant concentration, in particular on its top surface. Furthermore, electrodes are characterized with altered kinetics, characteristic for partially blocked electrodes with quasi-reversible charge transfer.
Applied Physics Letters, 2008
Nanocrystal-assembled cubic boron nitride (cBN) islands are formed by using low-energy (∼20eV) io... more Nanocrystal-assembled cubic boron nitride (cBN) islands are formed by using low-energy (∼20eV) ion irradiation in an inductively coupled fluorine-containing plasma. The temporal evolution of surface morphology and roughness reveals three-dimensional island growth for initial sp2-bonded BN and subsequent cBN, accompanied by a high frequency of renucleation. The formation of cBN islands enhances the field emission and reduces the turn-on field down to around 9V∕μm due to an increase in the island-related field. The results demonstrate the high potential of cBN for field emitters, comparable to other wide band gap semiconductors.
Journal of Applied Physics, 2019
Electroactivity of graphene-family nanomaterials and three-dimensional porous architectures is ke... more Electroactivity of graphene-family nanomaterials and three-dimensional porous architectures is key for various applications at the grand challenges of “energy-water-sensing nexus.” It requires well-controlled morphology, manipulation of surface chemistry, interconnected topologic network, as well as electronic properties. Here, we demonstrate by taking advantage of hierarchical mesoporosity, optimized defects number density, nD (edges-plane and pore sites, oxygenated and nitrogenated functionalities), further invoked by synergistic coupling between one-dimensional single-walled carbon nanotube (SWCNT) as “nano” spacers and polymer linker with two-dimensional reduced graphene oxide derived three-dimensional scaffolds (known as aerogels) under hydrothermal conditions, and improved electrochemical (re)activity by enhancing the heterogeneous electron transfer rate (kET). We determined the correlation among nD, in-plane sp2C cluster, La and interdefect distance, LD (all via Raman spectro...
Journal of Materials Research, 2016
We report the development of hybrids consisting of supercapacitive graphene oxide (GO), reduced G... more We report the development of hybrids consisting of supercapacitive graphene oxide (GO), reduced GO (rGO), electrochemically reduced GO (ErGO), multilayer graphene (MLG) decorated with pseudocapacitive nanostructured cobalt oxides (CoO, Co 3 O 4 ) and nanoparticles (CoNP) via electrodeposition and hydrothermal synthesis facilitating chemically bridged (covalently and electrostatically anchored) interfaces with tunable properties. These hybrid samples showed heterogeneous transport behavior determining diffusion coefficient (4 × 10 −8 –6 × 10 −6 m 2 /s) following CoO/MLG 3 O 4 /MLG 3 O 4 /rGO HT 550 F/g for Co 3 O 4 /ErGO and Co 3 O 4 /MLG. We found an ultrahigh sensitivity of 4.57 mA/(mM cm 2 ) and excellent limit of glucose detection 3 O 4 /rGO HT 3 O 4 /MLG. These findings are due to open pore network and topologically multiplexed conductive pathways provided by graphene nanoscaffolds to ensure rapid charge transfer and ion conduction. Density functional theory determined density of states in the vicinity of Fermi level in-turn providing contribution toward electroactivity due to orbital re-hybridization.
Physical Review Letters, 2010
Quasistationary states are long-lived nonequilibrium states, observed in some systems with longra... more Quasistationary states are long-lived nonequilibrium states, observed in some systems with longrange interactions under deterministic Hamiltonian evolution. These intriguing non-Boltzmann states relax to equilibrium over times which diverge algebraically with the system size. To test the robustness of this phenomenon to nondeterministic dynamical processes, we have generalized the paradigmatic model exhibiting such a behavior, the Hamiltonian mean-field model, to include energy-conserving stochastic processes. Analysis, based on the Boltzmann equation, a scaling approach, and numerical studies, demonstrates that in the long time limit the system relaxes to the equilibrium state on time scales which do not diverge algebraically with the system size. Thus, quasistationarity takes place only as a crossover phenomenon on times determined by the strength of the stochastic process.
In this paper, we explain the concept, characteristics and need of big data and different offerin... more In this paper, we explain the concept, characteristics and need of big data and different offerings available in the market to explore unstructured large data. This paper covers big data adoption trends, entry and exit criteria for the vendor and product selection, best practices, customer success story, benefits of big data analytics, summary and conclusion. Our analysis illustrates that the big data analytics is a fast-growing, influential practice and a key enabler for the social business. The insights gained from the user generated online contents and collaboration with customers is critical for success in the age of social media.
Journal of Electronic Materials, 2020
Two-dimensional (2D) layered materials are studied in efforts to discover new compounds and for t... more Two-dimensional (2D) layered materials are studied in efforts to discover new compounds and for their fascinating properties engendered by their sheet-like structure and tunable surfaces. MXenes are an emergent class of layered, synthesized transition metal carbides and carbonitrides that are useful in addressing the formidable challenges of sensing at the energy-water nexus. This work reports systematic structural and electrochemical properties of titanium carbide (Ti 3 C 2 T x) MXenes revealed by varying interlayer spacing, flake thickness and lateral size under different electrolytes. In addition to traditional electrode kinetics, we utilized surface sensitive scanning electrochemical microscopy (SECM) to gain a more complete understanding of rich MXene surface chemistry and corresponding knowledge about the physicochemical processes, including inherent electrochemistry and heterogeneous charge transfer characteristics, at electrode/electrolyte (solid/liquid) interfaces. We employed electron microscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, x-ray diffraction, and Raman spectroscopy to determine surface morphology, microscopic and electronic structure and lattice vibrational properties. It is shown that Ti 3 C 2 T x or, specifically, transition metal Ti, undergoes irreversible oxidation and lithiation in a positive potential window, which strongly depends on the flake thickness and type (aqueous versus organic) of the electrolyte. Multi-layered and smaller Ti 3 C 2 T x flakes exhibit faster electron transfer kinetics (k ET = 1.2 cm s À1) with a potassium ferrocyanide [Fe(CN) 6 ] 4À/3À redox probe, compared to few-layered Ti 3 C 2 T x (k ET = 0.3 cm s À1) in aqueous and organic electrolyte (k ET = 4.9 cm s À1) with a [Fe(CN) 6 ] 4À/3À redox probe, and compared to a few-layered Ti 3 C 2 T x (k ET = 0.9 cm s À1). In addition, the few-layered free standing Ti 3 C 2 T x film electrode remains intact following irreversible oxidation. These properties help to establish structure-property-electroactivity relationships among different types of Ti 3 C 2 T x MXenes.
Nano-Structures & Nano-Objects, 2017
h i g h l i g h t s • FRET biosensor based on aptamer/functionalized graphene for ultrasensitive ... more h i g h l i g h t s • FRET biosensor based on aptamer/functionalized graphene for ultrasensitive detection of bisphenol A. • Qualitative and quantitative detection of BPA were successfully elucidated and realized with limit of detection <1 pg/mL by assessing the change followed by recovery of fluorescent intensity on BPA addition. • We applied the developed sensor for real water (river water, drinking mineral water and tap water) samples because of its facile preparation and manipulation, scalability and excellent performance with good recovery. • The specificity is evaluated by measuring the fluorescent intensity change with BPA analogs (BP, BPB, BPC and DES) for benchmarking this biosensor.
Symmetries and Quark Models, 1970
MRS Proceedings, 2006
ABSTRACTCarbon nanotubes (CNTs) are of great interest because of several unsurpassable physical (... more ABSTRACTCarbon nanotubes (CNTs) are of great interest because of several unsurpassable physical (mechanical, electrical, thermal, and chemical) properties. Especially their large elastic modulus and breaking strength make them highly attractive for their use as reinforced agents in forming a new class of multifunctional advanced materials - onanocomposites, in addition to high conductivity (either in semiconducting or metallic regimes) achieved through lower percolation thresholds for several electronic applications. Among the known conducting polymers, polyaniline (PANI) has a high potential due to its ease of synthesis, excellent environmental, and thermal stability and reversible control of its electrical/electronic properties. In this work, PANI-single-/multiwalled NTs composites films containing different nanotube content of both kinds were synthesized by spin-cast preceded by ultrasonic mixing of the constituents. They were characterized using complementary techniques includin...
MRS Proceedings, 2006
ABSTRACTRelaxors (PZN, in particular) is an important class of self-assembled nanostructure compo... more ABSTRACTRelaxors (PZN, in particular) is an important class of self-assembled nanostructure composite ferroelectric oxides (or perovskite) materials. The interesting features associated with the nanoregions/nanodomains required to describe these relaxors give rise to the most relevant device related characteristics and peculiar physical properties in these materials. In addition, they possess astronomical property coefficients by themselves or when modified with lead titanate (PT) forming solid solution. In the past, we conducted temperature dependent Raman scattering studies on solid solution (1−x)PZN−xPT relaxors single crystals with varying composition; x = 0.02, 0.085, and 0.11. These studies were performed to obtain relevant information about lattice/phonon dynamics for matching the application criteria such as electromechanical actuators. We showed that the sharp structural phase transition occurs at or near 460 K which is a first-order transition by fitting two spectroscopic ...