raj solanki - Academia.edu (original) (raw)
Papers by raj solanki
Materials Research Express, 2015
ABSTRACT
Journal of Power Sources, 2015
ABSTRACT Potassium barium hexacyanoferrate (K2BaFe(CN)6) was investigated as a cathode material f... more ABSTRACT Potassium barium hexacyanoferrate (K2BaFe(CN)6) was investigated as a cathode material for reversible Ca2+ ion insertion/extraction type rechargeable battery using non-aqueous electrolytes. The electrochemical performance of K2BaFe(CN)6was evaluated using cyclic voltammetry and galvanic cycling at ambient temperature. It is shown that addition of water led to significant enhancement in intercalation and de-intercalation of Ca2+ ions, leading to improved charge/discharge capacity. The enhancement in performance is attributed to formation of solvation spheres around the intercalating Ca2+ ions which provide screening from the electrostatic charges of the BaFe(CN)6 lattice. A reversible capacity of 55.8 mA hr g-1 and a coulombic efficiency of 93.8% was demonstrated at the end of 30 charge/discharge cycles.
Solid-State Electronics, 2013
Chemical modification of graphene by covalently functionalizing its surface potentially allows a ... more Chemical modification of graphene by covalently functionalizing its surface potentially allows a wider flexibility in engineering electronic structure, in particular the local density of states of the carbon atoms bound to the modifier that can result in opening of the band gap. Such binding can involve covalent hydrogenation of graphene to modify hybridization of carbon atoms from sp 2 to sp 3 geometry [1-3]. Methods have also been developed to functionalize graphene covalently with molecular species [4-8]. Among these, perfluorophenylazide (PFPA) functionalization of graphene is well-developed using a nitrene intermediate. Films of this molecule also act as adhesion layers that allow production of long ribbons of exfoliated graphene [7-9]. We have developed a theory to predict electrical properties of PFPA functionalized graphene and compared it to experimental results. Conductivity of these PFPA functionalized ribbons of exfoliated graphene show good agreement with our theory.
Nucleic Acids Research, 2008
The temperature induced melting transition of a selfcomplementary DNA strand covalently attached ... more The temperature induced melting transition of a selfcomplementary DNA strand covalently attached at the 5' end to the surface of a gold interdigitated microelectrode (GIME) was monitored in a novel, label-free, manner. The structural state of the hairpin was assessed by measuring four different electronic properties of the GIME (capacitance, impedance, dissipation factor and phase angle) as a function of temperature from 258C to 808C. Consistent changes in all four electronic properties of the GIME were observed over this temperature range, and attributed to the transition of the attached single-stranded DNA (ssDNA) from an intramolecular, folded hairpin structure to a melted ssDNA. The melting curve of the self-complementary single strand was also measured in solution using differential scanning calorimetry (DSC) and UV absorbance spectroscopy. Temperature dependent electronic measurements on the surface and absorbance versus temperature values measured in solution experiments were analyzed assuming a two-state process. The model analysis provided estimates of the thermodynamic transition parameters of the hairpin on the surface. Two-state analyses of optical melting data and DSC measurements provided evaluations of the thermodynamic transition parameters of the hairpin in solution. Comparison of surface and solution measurements provided quantitative evaluation of the effect of the surface on the thermodynamics of the melting transition of the DNA hairpin.
Journal of Nanoscience and Nanotechnology, 2008
Si0.5Ge0.5 nanowires have been utilized to fabricate source-drain channels of p-type field effect... more Si0.5Ge0.5 nanowires have been utilized to fabricate source-drain channels of p-type field effect transistors (p-FETs). These transistors were fabricated using two methods, focused ion beam (FIB) and electron beam lithography (EBL). The electrical analyses of these devices show field effect transistor characteristics. The boron-doped SiGe p-FETs with a high-k (HfO2) insulator and Pt electrodes, made via FIB produced devices with effective hole mobilities of about 50 cm2V−1s−1. Similar transistors with Ti/Au electrodes made via EBL had effective hole mobilities of about 350 cm2V−1s−1.
Journal of Nanoscience and Nanotechnology, 2008
Diodes within individual silicon nanowires were fabricated by doping them during growth to produc... more Diodes within individual silicon nanowires were fabricated by doping them during growth to produce p–n junctions. Electron beam lithography was then employed to contact p- and n-doped ends of these nanowires. The current–voltage (I–V) measurements showed diode-like characteristics with a typical threshold voltage (Vt) of about 1 V and an ideality factor (n) of about 3.6 in the quasi-neutral region. The reverse bias I–V measurement showed an exponential behavior, indicating tunneling as the current leakage mechanism.
Journal of Experimental Nanoscience, 2008
Heterojunction photovoltaic devices were fabricated using single crystal silicon nanowires and th... more Heterojunction photovoltaic devices were fabricated using single crystal silicon nanowires and the organic semiconductor regioregular poly-(3-hexyl thiophene) (RR-P3HT). N-type nanowires were first grown on an nþ silicon substrate by the vapor-liquid-solid (VLS) method. Devices were then fabricated by filling the gap between the nanowires and a transparent indium tin oxide (ITO) glass electrode with a polymer. For initial devices the gap was filled with P3HT deposited from chlorobenzene solution. Device performance indicates that both silicon and P3HT act as absorbers for photovoltaic response, but that photocurrents were very low due to high series resistance in the cell. A second type of device was fabricated by depositing a thin layer of P3HT on the grown nanowires by dip coating from a dilute solution, and then filling the voids between nanowires and the transparent electrode with the conductive polymer poly-[3,4-(ethylenedioxy)thiophene]: poly-(styrene sulfonate) (PEDOT:PSS). The relatively high mobility of this organic conductor results in much higher photocurrents in photovoltaic cells, but results in a dip in the spectral response of the cells in the blue-green region due to light absorption in the conducting polymer. These materials show promise for efficient low-cost photovoltaic devices, but the cell geometry and materials interfaces will need to be optimized to reach their potential.
Materials Research Express, 2015
ABSTRACT
Journal of Power Sources, 2015
ABSTRACT Potassium barium hexacyanoferrate (K2BaFe(CN)6) was investigated as a cathode material f... more ABSTRACT Potassium barium hexacyanoferrate (K2BaFe(CN)6) was investigated as a cathode material for reversible Ca2+ ion insertion/extraction type rechargeable battery using non-aqueous electrolytes. The electrochemical performance of K2BaFe(CN)6was evaluated using cyclic voltammetry and galvanic cycling at ambient temperature. It is shown that addition of water led to significant enhancement in intercalation and de-intercalation of Ca2+ ions, leading to improved charge/discharge capacity. The enhancement in performance is attributed to formation of solvation spheres around the intercalating Ca2+ ions which provide screening from the electrostatic charges of the BaFe(CN)6 lattice. A reversible capacity of 55.8 mA hr g-1 and a coulombic efficiency of 93.8% was demonstrated at the end of 30 charge/discharge cycles.
Solid-State Electronics, 2013
Chemical modification of graphene by covalently functionalizing its surface potentially allows a ... more Chemical modification of graphene by covalently functionalizing its surface potentially allows a wider flexibility in engineering electronic structure, in particular the local density of states of the carbon atoms bound to the modifier that can result in opening of the band gap. Such binding can involve covalent hydrogenation of graphene to modify hybridization of carbon atoms from sp 2 to sp 3 geometry [1-3]. Methods have also been developed to functionalize graphene covalently with molecular species [4-8]. Among these, perfluorophenylazide (PFPA) functionalization of graphene is well-developed using a nitrene intermediate. Films of this molecule also act as adhesion layers that allow production of long ribbons of exfoliated graphene [7-9]. We have developed a theory to predict electrical properties of PFPA functionalized graphene and compared it to experimental results. Conductivity of these PFPA functionalized ribbons of exfoliated graphene show good agreement with our theory.
Nucleic Acids Research, 2008
The temperature induced melting transition of a selfcomplementary DNA strand covalently attached ... more The temperature induced melting transition of a selfcomplementary DNA strand covalently attached at the 5' end to the surface of a gold interdigitated microelectrode (GIME) was monitored in a novel, label-free, manner. The structural state of the hairpin was assessed by measuring four different electronic properties of the GIME (capacitance, impedance, dissipation factor and phase angle) as a function of temperature from 258C to 808C. Consistent changes in all four electronic properties of the GIME were observed over this temperature range, and attributed to the transition of the attached single-stranded DNA (ssDNA) from an intramolecular, folded hairpin structure to a melted ssDNA. The melting curve of the self-complementary single strand was also measured in solution using differential scanning calorimetry (DSC) and UV absorbance spectroscopy. Temperature dependent electronic measurements on the surface and absorbance versus temperature values measured in solution experiments were analyzed assuming a two-state process. The model analysis provided estimates of the thermodynamic transition parameters of the hairpin on the surface. Two-state analyses of optical melting data and DSC measurements provided evaluations of the thermodynamic transition parameters of the hairpin in solution. Comparison of surface and solution measurements provided quantitative evaluation of the effect of the surface on the thermodynamics of the melting transition of the DNA hairpin.
Journal of Nanoscience and Nanotechnology, 2008
Si0.5Ge0.5 nanowires have been utilized to fabricate source-drain channels of p-type field effect... more Si0.5Ge0.5 nanowires have been utilized to fabricate source-drain channels of p-type field effect transistors (p-FETs). These transistors were fabricated using two methods, focused ion beam (FIB) and electron beam lithography (EBL). The electrical analyses of these devices show field effect transistor characteristics. The boron-doped SiGe p-FETs with a high-k (HfO2) insulator and Pt electrodes, made via FIB produced devices with effective hole mobilities of about 50 cm2V−1s−1. Similar transistors with Ti/Au electrodes made via EBL had effective hole mobilities of about 350 cm2V−1s−1.
Journal of Nanoscience and Nanotechnology, 2008
Diodes within individual silicon nanowires were fabricated by doping them during growth to produc... more Diodes within individual silicon nanowires were fabricated by doping them during growth to produce p–n junctions. Electron beam lithography was then employed to contact p- and n-doped ends of these nanowires. The current–voltage (I–V) measurements showed diode-like characteristics with a typical threshold voltage (Vt) of about 1 V and an ideality factor (n) of about 3.6 in the quasi-neutral region. The reverse bias I–V measurement showed an exponential behavior, indicating tunneling as the current leakage mechanism.
Journal of Experimental Nanoscience, 2008
Heterojunction photovoltaic devices were fabricated using single crystal silicon nanowires and th... more Heterojunction photovoltaic devices were fabricated using single crystal silicon nanowires and the organic semiconductor regioregular poly-(3-hexyl thiophene) (RR-P3HT). N-type nanowires were first grown on an nþ silicon substrate by the vapor-liquid-solid (VLS) method. Devices were then fabricated by filling the gap between the nanowires and a transparent indium tin oxide (ITO) glass electrode with a polymer. For initial devices the gap was filled with P3HT deposited from chlorobenzene solution. Device performance indicates that both silicon and P3HT act as absorbers for photovoltaic response, but that photocurrents were very low due to high series resistance in the cell. A second type of device was fabricated by depositing a thin layer of P3HT on the grown nanowires by dip coating from a dilute solution, and then filling the voids between nanowires and the transparent electrode with the conductive polymer poly-[3,4-(ethylenedioxy)thiophene]: poly-(styrene sulfonate) (PEDOT:PSS). The relatively high mobility of this organic conductor results in much higher photocurrents in photovoltaic cells, but results in a dip in the spectral response of the cells in the blue-green region due to light absorption in the conducting polymer. These materials show promise for efficient low-cost photovoltaic devices, but the cell geometry and materials interfaces will need to be optimized to reach their potential.