Dinesh Deva

Adsorbents based on carbon microfibers and carbon nanofibers for the removal of phenol and lead from water

This paper describes the production, characteristics, and efficacy of carbon microfibers and carbon nanofibers for the removal of phenol and Pb(2+) from water by adsorption. The first adsorbent produced in the current investigation contained the ammonia (NH(3)) functionalized micron-sized activated carbon fibers (ACF). Alternatively, the second adsorbent consisted of a multiscale web of ACF/CNF, which was prepared by growing carbon nanofibers (CNFs) on activated ACFs via catalytic chemical vapor deposition (CVD) and sonication, which was conducted to remove catalytic particles from the CNF tips and open the pores of the CNFs. The two adsorbents prepared in the present study, ACF and ACF/CNF, were characterized by several analytical techniques, including SEM-EDX and FT-IR. Moreover, the chemical composition, BET surface area, and pore-size distribution of the materials were determined. The hierarchal web of carbon microfibers and nanofibers displayed a greater adsorption capacity for Pb(2+) than ACF. Interestingly, the adsorption capacity of ammonia (NH(3)) functionalized ACFs for phenol was somewhat larger than that of the multiscale ACF/CNF web. Difference in the adsorption capacity of the adsorbents was attributed to differences in the size of the solutes and their reactivity towards ACF and ACF/CNF. The results indicated that ACF-based materials were efficient adsorbents for the removal of inorganic and organic solutes from wastewater.

Development of bimetal-grown multi-scale carbon micro-nanofibers as an immobilizing matrix for enzymes in biosensor applications.

This study describes the development of a novel bimetal (Fe and Cu)-grown hierarchical web of carbon micro-nanofiber-based electrode for biosensor applications, in particular to detect glucose in liquids. Carbon nanofibers (CNFs) are grown on activated carbon microfibers (ACFs) by chemical vapor deposition (CVD) using Cu and Fe as the metal catalysts. The transition metal-fiber composite is used as the working electrode of a biosensor applied to detect glucose in liquids. In such a bi-nanometal-grown multi-scale web of ACF/CNF, Cu nanoparticles adhere to the ACF-surface, whereas Fe nanoparticles used to catalyze the growth of nanofibers attach to the CNF tips. By ultrasonication, Fe nanoparticles are dislodged from the tips of the CNFs. Glucose oxidase (GOx) is subsequently immobilized on the tips by adsorption. The dispersion of Cu nanoparticles at the substrate surface results in increased conductivity, facilitating electron transfer from the glucose solution to the ACF surface during the enzymatic reaction with glucose. The prepared Cu-ACF/CNF/GOx electrode is characterized for various surface and physicochemical properties by different analytical techniques, including scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), BET surface area analysis, and transmission electron microscopy (TEM). The electrochemical tests show that the prepared electrode has fast response current, electrochemical stability, and high electron transfer rate, corroborated by CV and calibration curves. The prepared transition metal-based carbon electrode in this study is cost-effective, simple to develop, and has a stable immobilization matrix for enzymes.

Changes in surface topography of amorphous silicon germanium films after light soaking

Light-induced metastable degradation of hydrogenated amorphous silicon and silicon germanium thin films (a-SiGe:H) is conjectured to be accompanied by structural changes but there has not been a direct measurement of the same. We measure the surface topography of these films in the annealed and the light soaked state using atomic force microscopy. We quantified the surface topography in terms of surface roughness and find that the surface roughness increases after light soaking. Our results provide direct evidence of the light-induced structural changes in these films.

Nanocrystalline cubic Silicon Carbide thin films for the window layer of solar cells deposited by Hot Wire CVD

Nanocrystalline cubic silicon carbide (nc-3C-SiC) films are deposited using hot wire chemical vapour deposition technique at ~350 °C on glass substrates using SiH4 /CH4/H2 as precursor gases. We investigated the influence of total gas pressure on the structural, optical and transport properties of nc-3C-SiC films. Raman scattering spectra and X-ray diffraction patterns revealed that the film prepared below 2 mbar is nanocrustalline silicon (nc-Si), while at ≥ 2 mbar films are nc-3C-SiC. We achieved high deposition rate (≥ 14-20 nm/min), high optical band gap (3.2-3.4 eV) and high conductivity (~ 10-4 -10-2 Ω-1cm-1) suitable for window layer for Solar cells.

Fabrication of two dimensional carbon nanostructures using hotwire chemical vapor deposition technique

Two dimensional carbon nanostructures (carbon nanosheets) are fabricated using Hot Wire Chemical Vapor Deposition (HWCVD) technique assisted by H radical injection, using CH4 as source gas. Carbon nanosheets are grown on crystalline Si(100) wafer as well as on corning glass substrate without using catalyst. The grown carbon nanosheets are aligned vertically on the substrate with thickness in the range of 10-20 nm and about 60-80 nm in height.