Publications

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The magnetic field alters the rate of photochemical hydrogen evolution in Weyl semimetals by influencing its electronic properties.

Using high-resolution neutron powder diffraction we have determined the average and local structure of YCrO3 in order to explain the recently reported properties of YCrO3.

Carbon nanotubes (CNTs) and N-doped CNTs with Y-junctions have been prepared by the pyrolysis of nickelocene–thiophene and nickel phthalocyanine–thiophene mixtures, respectively, the latter being reported for the first time. The junctions are free from the presence of sulfur and contain only carbon or carbon and nitrogen. The electronic properties of the junction nanotubes have been investigated by scanning tunneling microscopy. Tunneling conductance measurements reveal rectifying behavior with regions of coulomb blockade, the effect being much larger in the N-doped junction nanotubes.

Investigations on the fluorescence quenching of graphene have been carried out with two organic donor molecules, pyrene butanaoic acid succinimidyl ester (PyBS, I) and oligo(p-phenylenevinylene) methyl ester (OPV-ester, II). Absorption and photoluminescence spectra of I and II recorded in mixture with increasing the concentrations of graphene showed no change in the former, but remarkable quenching of fluorescence. The property of graphene to quench fluorescence of these aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements.

In the light of the recent discovery that carbon-rich borocarbonitrides show electrocatalytic activity for generating hydrogen from water, we have synthesized nanocomposites by covalently cross-linking BC7N with MoS2 sheets to explore whether the HER activity can be significantly enhanced. In order to cross-link BC7N and MoS2 sheets, we have exploited the presence of different functional groups on the surfaces of BN (NH2) and graphene (COOH) domains of the borocarbonitride, as quantitatively determined by FLOSS. We have thus obtained two nanocomposites differing in the location of the cross-linking and these are designated as BN/BCN–MoS2 and G/BCN–MoS2, depending on which domains in the borocarbonitride participate in cross-linking. These nanocomposites were characterized by various spectroscopic methods including fluorescence labeling and their electrochemical and photochemical HER activity investigated. The composite where the graphene domains are cross-linked to MoS2 nanosheets, G/BCN–MoS2 (1:2), exhibits outstanding electrochemical HER activity with an onset potential of −30 mV (vs RHE) and a current density of 10 mA cm–2 at an overpotential of −35 mV. This performance is closely comparable to that of Pt. The composite where the BN domains were cross-linked show somewhat lower activity. The physical mixture of BCN and MoS2, on the other hand, does not display any notable HER activity. The BCN–MoS2 composites also exhibit good photochemical activity. It is noteworthy that 2H-MoS2, which does not exhibit significant catalytic activity, can be rendered highly active by cross-linking with BCN.