Prathap Haridoss

Effect of the organic solvent on the formation and stabilization of CdS and PbS nanoclusters

Nanoclusters of CdS and PbS were prepared using two different organic solvents as stabilizers in order to understand the factors affecting their formation and stabilization. Growth of the nanoclusters was monitored by optical absorption spectroscopy at regular intervals of time. Mean cluster size was characterized by X-ray diffraction (XRD). The surface structure of nanoclusters was analyzed using infrared (IR) spectroscopy. Spectroscopic studies under identical experimental conditions reveal interesting correlations between the stability of the nanoclusters formed, the nature of the solvent and the size of metal ion involved, leading to a better understanding of nanocluster formation.

Structural modifications of disordered mesocarbon microbeads with lower temperatures of heat treatment

We describe the variation of structural and physical properties of mesocarbon microbeads, a potential anode material for rechargeable lithium batteries, as a function of heat-treatment temperature in the range 400{endash}1100thinsp{degree}C. Scanning electron microscope (SEM) studies indicated changes in the morphology of the mesocarbons with heat treatment. X-ray studies show that average crystallite size varies considerably with heat treatment. The d{sub 002} spacing decreases with increasing heat treatment temperatures. The electronic conductivity of the mesocarbon microbeads also increases substantially with increasing heat-treatment temperature. Based on thermogravimetrical analysis (TGA) and other measurements, we find that organic fractions volatilizes out of these carbons in two distinct stages. The observed weight loss correlates with the structural changes observed. We suggest that these observations are consistent with two types of hydrogenated fractions present in the {open_quotes}green{close_quotes} mesocarbons. {copyright} {ital 1998 Materials Research Society.}

Benefits of tubular morphologies on electron transfer properties in CNT/TiNT nanohybrid photocatalyst for enhanced H2 production

In order to study the influence of one dimensional tubular structures for effective electron and hole transportation onto the surface of a photocatalyst leading to efficient solar photocatalytic hydrogen production, functionalized carbon nanotube (FCNT)/TiO2 nanotube nanohybrids were prepared. TiO2 nanotubes (TiNTs) were prepared by hydrothermal method. A series of novel functionalized carbon nanotube/TiO2 nanotube nanohybrids (CTT) were prepared for different wt% (1–20) of FCNTs by wet impregnation method to extend absorption in the visible region and also to retard the electron–hole pair recombination and thereby to enhance the H2 production capability under solar light irradiation. The functionalized carbon nanotube/TiO2 nanotube nanohybrids (CTT) were characterized with XRD, TEM, DRS-UV-Vis, Raman spectroscopy and XPS for crystal structure, morphology, optical properties and chemical composition. Addition of FCNTs to the TiNTs in CTT nanohybrids extended the absorption to the visible region. Relative electron–hole recombination times were measured with photoluminescence spectra. The highest H2 generation of 29 904 μmol g−1 was observed after 4 h under optimal conditions due to better separation of electron–hole pairs and electron conducting properties.

Nanoscratch technique for aligning multiwalled carbon nanotubes synthesized by the arc discharge method in open air

Horizontally aligned and densely packed multiwalled carbon nanotubes (MWCNTs) were synthesized in an open air, without the need for a controlled atmosphere, using a rotating cathode arc discharge method with the help of a metal scraper. The physical force exerted by the scraper results in in-situ alignment of MWCNTs along the direction of scrape marks. This strategy, which enables the alignment of nanotubes in a controlled fashion to any length and direction of interest, was examined to determine the force required to align a nanotube. A model is developed to understand the alignment process. Using the nanoscratch technique to mimic this strategy, and incorporating the data obtained from the nanoscratch technique into the model developed, the minimum force required to align a MWCNT, as well as the energy required to align a gram of nanotubes, has been estimated. The method demonstrated represents an economical approach for large-scale synthesis of aligned MWCNTs at low costs.