V. Vasu

Investigation of Hydrogen Desorption From Hydrogenated Single-Walled Carbon Nanotubes Functionalized With Borane

The present experimental study reports on hydrogen desorption behavior of hydrogenated single-walled carbon nanotubes (SWCNTs), functionalized with borane (BH3). Desorption is carried out using a thermal annealing technique. The hydrogenated samples are annealed at 200 °C for 30 min and characterized using Fourier transform infrared (FTIR) and Raman spectroscopy studies. The amount of released hydrogen is measured by thermogravimetric/thermal desorption spectroscopy (TG/TDS) studies. FTIR and Raman studies confirm the desorption of hydrogen. The TG/TDS results reveal that 100% of stored hydrogen is released in approximately 1.5 min in the temperature range 100-150°C.

Copper nanoparticles entrapped in SWCNT-PPy nanocomposite on Pt electrode as NOx electrochemical sensor

A highly sensitive NO(x) sensor was designed and developed by electrochemical incorporation of copper nanoparticles (CuNP) on single-walled carbon nanotubes (SWCNT)-polypyrrole (PPy) nanocomposite modified Pt electrode. The modified electrodes were characterized by scanning electron microscopy and energy dispersive X-ray analysis. Further, the electrochemical behavior of the CuNP-SWCNT-PPy-Pt electrode was investigated by cyclic voltammetry. It exhibited the characteristic CuNP reversible redox peaks at -0.15 V and -0.3 V vs. Ag/AgCl respectively. The electrocatalytic activity of the CuNP-SWCNT-PPy-Pt electrode towards NO(x) is four-fold than the CuNP-PPy-Pt electrode. These results clearly revealed that the SWCNT-PPy nanocomposite facilitated the electron transfer from CuNP to Pt electrode and provided an electrochemical approach for the determination of NO(x). A linear dependence (r(2)=0.9946) on the NO(x) concentrations ranging from 0.7 to 2000 μM, with a sensitivity of 0.22 ± 0.002 μA μM(-1)cm(-2) and detection limit of 0.7 μM was observed for the CuNP-SWCNT-PPy-Pt electrode. In addition, the sensor exhibited good reproducibility and retained stability over a period of one month.

Conformational flexibility decreased due to Y67F and F82H mutations in cytochrome c: Molecular dynamics simulation studies

Cytochrome c (cyt c), a mitochondrial protein, has dual functions in controlling both cellular energetic metabolism and apoptosis (programmed cell death). During apoptosis, cyt c (Fe(3+)) released into the cytosol initiates caspase activation leading to apoptosis. Since, X-ray crystallography gives only the static structure, we report here the dynamic behavior of holo and apo wild type (WT), Y67F and F82H mutant cyt cs (Fe(3+)) in their apoptotic states. Four nanosecond MD simulations were run for holo WT, Y67F and F82H cyt cs with and without Fe...S (Met-80) bond and also for apo WT and mutated cyt cs (Y67F and F82H) in water using GROMOS96 force field. Mutations of Y67F and F82H resulted in the decrease of backbone and Calpha RMSDs, and radii of gyration (backbone and protein) in both the holo and apo forms. MD and ED results revealed that the flexibility of mutated holo cyt cs decreased perhaps affecting their ability to take part in mitochondrial electron/proton transfer process. Without Fe...S bond, the backbone and Calpha RMSD increased in holo cyt cs perhaps resulting in enhanced peroxidase activity. ED revealed that four to six eigenvectors involved in over all motions of holo cyt cs without Fe...S bond, and six to eight eigenvectors in apo cyt cs in comparison to three to four eigenvectors for holo cyt cs with Fe...S bond.

Preparation and Characterization of Tungsten Trioxide (WO3) Thin Films

The thin films of WO3 were prepared on cleaned microscopic glass substrates by the electron beam evaporation technique. The films were coated at room temperature using pure WO3 pellets as source. The prepared films were further post heat treated at different temperatures (100°C to 350°C) for about 1hr in air. The optical properties of WO3 thin films were studied in detail. The increase in the density of the film as the annealing temperature increases have been confirmed by the transmittance spectra. The film annealed at 250°C shows a strong photoluminescence peak. The peak intensity is found to be less for all other temperature. The observed results were discussed in terms of crystalline nature of WO3.

Molecular dynamics simulation studies on structural and conformational changes in tyrosine-67 nitrated cytochrome c

Protein tyrosine nitration is well-established post-translational modification occurring in a number of diseases, viz. neurodegenerative, cardiovascular diseases, ageing, etc. Tyrosine-67 (Tyr-67) nitration of cytochrome c (cyt c) was observed under oxidative stress affecting its structure and electron transfer properties. Hence, in this study, molecular dynamics (MD) simulations were carried out at room temperature to investigate the structural and conformational changes in the nitrated cyt cs. MD results revealed that the bond between FE (Heme-105) and S (Met-80) considerably weakened, radius of gyration, backbone and Cα root-mean-square deviations decreased and hydrogen bonding increased in the nitrated cyt cs relative to wild type (WT) cyt c. Ramachandran plot analysis revealed that N- and C-terminal helices also affected by nitration at CE2 carbon atom. Furthermore, essential dynamics analysis showed that amplitude of concerted motion decreased in the nitrated cyt cs, perhaps due to the increase in the hydrogen bonding interaction. Taken together, the structural and conformational changes in the active site Tyr-67 nitrated cyt c may have implications in the loss of electron/proton transfer and gain of apoptotic properties.

Desorption Studies on Hydrogenated Single Walled Carbon Nanotubes Functionalized with Borane (BH3)

In this work, desorption of hydrogen from hydrogenated single walled carbon nanotubes (SWCNTs) functionalized with borane is discussed. A hydrogen storage medium based on SWCNTs functionalized with borane is designed. The SWCNTs are functionalized with borane (BH3) using LiBH4 as the precursor by solution cast method. The functionalized samples are hydrogenated. A storage capacity of 1.5 wt.% is obtained just above room temperature (50°C). The hydrogenated and dehydrogenated samples are characterized using FTIR and Raman studies. The thermogravimetry/differential thermal analysis (TG/DTA) results reveal that the entire amount of (1.5 wt.%) stored hydrogen is released in the temperature range 100 - 150°C. This temperature range is suitable for hydrogen fuel cells used for vehicular applications.

Hydrogenation in SWCNTs Functionalized with Borane

We have done the experimental investigation of hydrogen storage in functionalized single‐walled carbon nanotubes (SWCNTs). The SWCNTs having the average diameter of 22 nm are deposited on alumina substrates by drop casting method. The functionalization of SWCNTs with BH3 using LiBH4 as the precursor, over the surface of SWCNTs is done by the same chemical method. Further, the functionalized samples are hydrogenated in the hydrogenation chamber. The samples are characterized through FTIR, XPS and CHNS studies. A hydrogen storage capacity of 0.87 wt % at 100 °C is observed.