Indian Association for the Cultivation of Science

About: Indian Association for the Cultivation of Science is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Catalysis & Excited state. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

ac conduction in iron bismuthate glassy semiconductors.

Abstract: The first measurements are reported for the frequency-dependent ac conductivity for the iron bismuthate glassy semiconductors in the frequency range ${10}^{2}$--${10}^{5}$ Hz and in the temperature range 80--450 K. The experimental data have been analyzed with reference to various theoretical models based on quantum-mechanical tunneling through the barrier and classical hopping over the barrier. The analysis shows that the correlated-barrier-hopping model is the most appropriate for the material under consideration. This model predicts quantitatively the temperature dependence of both the ac conductivity and its frequency exponent. However, other models, such as the quantum-mechanical tunneling model, are consistent with the low-temperature ac conductivity, but completely fail to interpret the observed temperature dependence of the frequency exponent. Similarly, the overlapping-large-polaron tunneling model can explain the temperature dependence of the frequency exponent at low temperature, although this model predicts the temperature dependence of the ac conductivity to be much higher than what the experimental data show.

Monolayer Group IV–VI Monochalcogenides: Low-Dimensional Materials for Photocatalytic Water Splitting

Abstract: Harvesting solar energy for artificial photosynthesis is an emerging area in alternative energy research. In the present article, we have investigated the photocatalytic properties of single-layer group IV–VI monochalcogenides, MXs (M = Ge, Si, Sn and X = S, Se) based on first-principles electronic structure calculations. Our dispersion corrected DFT calculations show that these materials have moderate cohesive energies (<120 meV/atom), which are indicative of favorable isolation of MX monolayers by mechanical, sonicated, or liquid-phase exfoliation. The calculated band gaps using hybrid density functional method (HSE06) reveal that all of the MXs show larger band gaps than the minimum energy required for the water splitting reaction (1.23 eV). Considering band edge alignments, all the MXs other than SiS have an acceptable alignment of conduction band minima but not the valence band maxima. We have evaluated the overpotentials for both oxygen and hydrogen evolution reactions. Interestingly, considering co...

Dipeptide-Based Low-Molecular-Weight Efficient Organogelators and Their Application in Water Purification

Abstract: The development of new low-molecular-weight gelators for organic solvents is motivated by several potential applications of gels as advanced functional materials. In the present study, we developed simple dipeptide-based organogelators with a minimum gelation concentration (MGC) of 6-0.15 %, w/v in aromatic solvents. The organogelators were synthesized using different L-amino acids with nonpolar aliphatic/aromatic residues and by varying alkyl-chain length (C-12 to C-16). The self-aggregation behavior of these thermoreversible organogels was investigated through several spectroscopic and microscopic techniques. A balanced participation of the hydrogen bonding and van der Waals interactions is crucial for efficient organogelation, which can be largely modulated by the structural modification at the hydrogen-bonding unit as well as by varying the alkyl-chain length in both sides of the hydrophilic residue. Interestingly, these organogelators could selectively gelate aromatic solvents from their mixtures with water. Furthermore, the xerogels prepared from the organogels showed a striking property of adsorbing dyes such as crystal violet, rhodamine 6G from water. This dye-adsorption ability of gelators can be utilized in water purification by removing toxic dyes from wastewater.

Short peptide based hydrogels: incorporation of graphene into the hydrogel

Abstract: Stable supramolecular hydrogels were obtained from Fmoc (N-fluorenyl-9-methoxycarbonyl) protected synthetic dipeptides, Fmoc-Xaa-Asp-OH (Xaa = Tyr, Phe). These hydrogels were characterized by various methods including transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), fluorescence spectroscopy and rheology. Different microscopic studies showed the presence of an entangled uniform nanofibrillar network structure in the gel state. These gelator molecules containing aromatic moieties in the side chain (Tyr/Phe) and in the N-terminus (fluorenyl group) can be useful in interacting with graphene sheets using π–π stacking interactions. One of these peptide based hydrogels (Fmoc-Tyr-Asp-OH) was utilized for the successful incorporation of reduced graphene oxide (RGO) into the hydrogel to make a well-dispersed RGO containing stable hybrid hydrogel. This study demonstrates that RGO is stabilized within the peptide based hydrogel system without the help of any external stabilizing agent. The RGO containing hybrid hydrogel was characterized using transmission electron microscopy, selected area electron diffraction, atomic force microscopy, Raman spectroscopy, and rheology. Morphological studies reveal the presence of a nano-hybrid system containing graphene (RGO) sheets and gel nanofibrils. The morphology of the peptide hydrogel does not change significantly even after the incorporation of RGO as it is evident from TEM and AFM studies. Rheological studies suggest the formation of a more rigid and ‘solid-like’ hybrid hydrogel after the incorporation of RGO into the native hydrogel.