Role of Dimensionality for Photocatalytic Water Splitting: CdS Nanotube versus Bulk Structure

Using state-of-the-art density functional theoretical calculations, we have modelled a facetted CdS nanotube (NT) catalyst for photocatalytic water splitting. The overall photocatalytic activity of the CdS photocatalyst has been predicted based on the electronic structures, band edge alignment, and overpotential calculations. For comparisons, we have also investigated the water splitting process over bulk CdS. The band edge alignment along with the oxygen evolution reaction/hydrogen evolution reaction (OER/HER) mechanism studies help us find out the effective overpotential for the overall water splitting on these surfaces. Our study shows that the CdS NT has a highly stabilized valence band edge compared to that of bulk CdS owing to strong p–d mixing. The highly stabilized valence band edge is important for the hole-transfer process and reduces the risk of electron-hole recombination. CdS nanotube requires less overpotential for water oxidation reaction than the bulk CdS. Our findings suggest that the efficiency of the water oxidation/reduction process further improves in CdS as we reduce its dimensionality, that is going from bulk CdS to one-dimensional nanotube. Furthermore, the stabilized valence band edge of CdS nanotube also improves the photostability of CdS, which is a problem for bulk CdS.     

A facile and efficient carbocatalytic route to quaternary C-bearing N-tosylaziridines from Morita-Baylis-Hillman adduct in water

Graphene oxide (GO)/GO-I₂ co-catalyzed green synthesis of tosylaziridine bearing keto and nitrile/ester functional groups is reported. The strategy involves sequential GO-catalyzed oxidation of benzylic alcohol and GO-I₂ catalyzed nitrene insertion into olefin of Morita-Baylis-Hillman adduct. Operational simplicity, use of water as solvent, ambient reaction conditions, excellent yield of products (88–96%) and recyclability of catalyst up to five times without any substantial change in morphology as well as catalytic efficiency are the salient features of the envisaged protocol.     

Investigation on pore structure and small-scale agglomeration behaviour in liquid phase sintered SiC using small angle neutron scattering

Mesoscopic density fluctuations in liquid phase sintered silicon carbide have been investigated using small angle neutron scattering (SANS). The increase in the additives results in the modification in the pore size distribution and to some extent the total porosity. SANS revealed a mass fractal nature of the agglomerated matrix microstructure. The fractal dimension of the matrix does not change appreciably with the additives although the upper cut-off value of the fractal decreases significantly with the increase in the additives. The liquid phase sintering due to the presence of additives helps to achieve higher level of densification. However, the agglomeration hinders achievement of the fully dense pellets.      

Light-charged-particle evaporation from hot 31P nucleus at E*∼ 60 MeV

The inclusive energy spectra of light charged particles, such as, α, p, d and t, evaporated from the hot ³¹P nucleus at an excitation energy E ^*∼ 60 MeV, have been measured at various angles. The compound nucleus ³¹P has been populated using two different entrance channel configurations; i.e., ⁷Li (47 MeV) + ²⁴Mg and ¹⁹F (96 MeV) + ¹²C reactions, leading to the same excitation energy of the compound system. It has been observed that the spectra obtained in the ⁷Li (47 MeV) + ²⁴Mg reaction follow the standard statistical-model prediction with a spherical configuration of the compound nucleus. But, the spectra obtained in the ¹⁹F (96 MeV) + ¹²C reaction deviate from similar predictions of the statistical model both on higher- as well as on lower-energy sides. Considerable deformation was required to be incorporated in the calculation in order to reproduce the measured-energy spectra in this case. Dynamical trajectory model calculations were not found to play any significant role in explaining the differences in behaviour between the two cases under study. The observed discrepancy has been attributed to the difference in the angular-momentum distributions of the compound nuclei formed in the two reactions.     

The use of hydrothermal methods in the synthesis of novel open-framework materials

The preparation of inorganic compounds, exhibiting open-framework structures, by hydrothermal methods has been presented. To illustrate the efficacy of this approach, few select examples encompassing a wide variety and diversity in the structures have been provided. In all the cases, good quality single crystals were obtained, which were used for the elucidation of the structure. In the first example, simple inorganic network compounds based on phosphite and arsenate are described. In the second example, inorganic-organic hybrid compounds involving phosphite/arsenate along with oxalate units are presented. In the third example, new coordination polymers with interesting structures are given. The examples presented are representative of the type and variety of compounds one can prepare by careful choice of the reaction conditions.     

Hydrogenation of Benzonitrile on Sn-Pt/SiO2 Catalysts Prepared by Introducing SnEt4 to Pt/SiO2: Role of Tin

Liquid phase hydrogenation of benzonitrile was studied over Sn-Pt/SiO₂ catalysts prepared by introducing tetraethyl tin onto the 3 wt.% Pt/SiO₂ catalyst. Tin content of the catalysts ranged from 0.05 to 0.63 wt.%, whereas Sn/Pt surface atomic ratios determined by chemisorption measurements were between 0.1 to 3.5. Dibenzylamine selectivity influenced to a small extent by the level of conversion and the Sn/Pt ratio wasca. 75 %. The addition of tin to Pt in the range of (Sn/Pt)_surface = 0.50–1.25 led to an increase in the turnover frequency (TOF) by a factor of 2. TOF showed a maximum at a surface atomic ratio of Sn/Pt = 1. The enhancement of catalyst activity upon the addition of tin is explained by the formation of Sn⁺-Pt ensemble sites on the surface of bimetallic nanoclusters. It is suggested that highly dispersed positively charged tin species, by polarizing the triple bond, enhance the reactivity of the -CN group. Calcination at 300°C followed by re-reduction of the catalysts resulted in a monotonic decrease of specific activity with increasing Sn/Pt ratio.     

Heteroannulation of nitroketene N,S-arylaminoacetals with POCl3: a novel highly regioselective synthesis of unsymmetrical 2,3-substituted quinoxalines

[reaction: see text]. A novel regioselective route for the synthesis of substituted and fused 3-chloro-2-(methylthio)quinoxalines through POCl3-mediated heteroannulation of a range of alpha-nitroketene N,S-anilinoacetals has been reported.     

Investigation of energy band gap and its correlation with vacancy defects in Pb1-xNixO nanoparticles synthesized through sol-gel method

Journal of Sol-Gel Science and Technology - Nickel doped lead oxide (Pb1-xNixO) nanoparticles with different concentration (x = 0.00, 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30) of...