Fluorescent nano materials and their sensing ability towards organic pollutants

Abstract

Synthesis of 1,3-bis(1-butylbenzimidazol-2-yl)benzene (L-2), 2,5-bis(1-butylbenzimidazol- 2-yl)thiophene(L-4), 2,5-bis(1-octylbenzimidazol-2-yl)thiophene (L-5), tetrarhenium metallacycles [{Re(CO)3}2(μ-dhaq)(μ-N–N)]2 (L-6) and [{Re(CO)3}2 (μ-thaq)(μ-N–N)]2 (L-7), (N–N= 2,5-bis(1-octylbenzimidazol-2-yl)thiophene, H2- dhaq= 1,4-dihydroxy-9,10-anthraquinone and H2-thaq= 1,2,4-tri hydroxy-9,10- anthraquinone) were described in the present study. Metallacycles L-6 and L-7 underwent aggregation in THF-water mixtures and the morphology of the aggregate depends on the fraction of water. Compounds L-6 and L-7 formed granular or spongy spheres in THF solution, while they formed micron size rods in a THF-water mixture containing 40% and 30% water respectively. Besides, higher water content of 80% afforded amorphous materials. The micron size rods of L-6, L-7 showed better photoluminescence (PL) over granular or spherical aggregates, while PL is totally quenched in case of amorphous aggregates. Synthesized compounds showed sensing ability towards picric acid (PA) and 1-chloro-4- nitrobenzene. The absorbance spectra showed significance changes and photoluminescence was quenched on addition of nitroaromatics to the solutions of the sensing compounds. Binding properties were studied by Beneshi-Hildebrand and Stern-Volmer plots and found that the compounds had significant binding with nitroaromatics. This class of compounds may be applied for developing sensors for nitroaromatic pollutants in aqueous system.