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: Excited state & Catalysis. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

Discriminative detection of nitro aromatic explosives by a luminescent metal–organic framework

Abstract: Nitro aromatics are the principal components of explosives used in acts of terrorism and within improvised explosive devices, among others. Although high sensitivity towards nitro aromatic explosives has been demonstrated, selective detection and discrimination are critical for practical applications. Fluorescence quenching of metal–organic frameworks (MOFs) is sufficiently sensitive to detect any nitro explosives, but discriminative detection with different numbers of –NO2 groups is rare. Here we report a stable fluorescent MOF, [Zn2(NDC)2(bpy)]·Gx, 1 (where NDC = 2,6-naphthalenedicarboxylic acid, bpy = 4,4′-bipyridine, and G = guest solvent molecules), whose fluorescence is quenched by trace amounts of nitro aromatics introduced from solution or in vapor phase. The steady-state and time-resolved experiments show that the quenching process is dynamic in nature and the interactions (dipole–dipole, π-stacking) between the MOF and nitro explosives play a crucial role in the discriminative detection of nitro aromatics with different numbers of –NO2 groups.

Graphene Oxide-Based Hydrogels to Make Metal Nanoparticle-Containing Reduced Graphene Oxide-Based Functional Hybrid Hydrogels

Abstract: In this study, stable supramolecular hydrogels have been obtained from the assembly of graphene oxide (GO) in presence of polyamines including tris(aminoethyl)amine, spermine, and spermidine [biologically active molecule]. One of these hydrogels has been well characterized by various techniques including field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD) study, and Raman spectroscopy. TEM and AFM studies of one of these hydrogels have revealed the presence of a network structure of cross-linked nanosheets. This suggests the supramolecular assembly of GO in the presence of polyamines using the acid-base type electrostatic interaction. In presence of a mild reducing agent (vitamin C), one of these GO hydrogels has been transformed into a reduced graphene oxide (RGO)-based hydrogel by a simple in situ reduction of GO sheets within the hydrogel matrix. Moreover, noble metal nanoparticle containing RGO based hybrid hydrogels have been obtained using in situ and simultaneous co-reduction of GO and noble metal precursors within the GO gel matrix. The elegance of this method is in situ, "green chemical" and simultaneous reduction of GO and metal salts within the hydrogel matrix to form RGO-based hybrid gel and concomitant stabilization of metal nanoparticles (MNPs) within the gel system. The nascently formed MNPs are homogeneously and uniformly distributed on the surface of the RGO nanosheets within the hybrid gel. Interestingly, this MNP containing RGO-based hybrid hydrogel matrix acts as a potential catalyst for the reduction of aromatic nitro to amino group. The catalyst (hybrid gel matrix) can be separated easily after the reaction and reused several times.

Organogelation and hydrogelation of low-molecular-weight amphiphilic dipeptides: pH responsiveness in phase-selective gelation and dye removal.

Abstract: The search for efficient low-molecular-weight gelators (LMWGs) with possible structure−activity correlation is on the rise The present work reports a novel set of amphiphilic dipeptide-based carboxylic acids capable of efficiently gelating organic solvents More interestingly, their sodium salts showed enhanced efficiency in organogelation with the additional ability to gelate water Electrostatic interactions present in the aggregation of the sodium carboxylates of amphiphilic dipeptides seem to be important because some of the nongelator carboxylic acids turned out to be excellent gelators upon salt formation The combinations and sequence of the amino acids in the dipeptide moiety were systematically altered to understand the collective importance of the nonpolar aliphatic/aromatic substitution in amino acids in the self-assembling behavior of amphiphiles Almost a 20-fold enhancement in the gelation ability was observed on reversing the sequence of the amino acid residues, and in some cases, nongelat