Adsorption-Driven Catalytic and Photocatalytic Activity of Phase Tuned In2S3 Nanocrystals Synthesized via Ionic Liquids

Phase tuned quantum confined In2S3 nanocrystals are accessible solvothermally using task-specific ionic liquids (ILs) as structure directing agents. Selective tuning of size, shape, morphology, and, most importantly, crystal phase of In2S3 is achieved by changing the alkyl side chain length, the H-bonding, and aromatic π-stacking ability of the 1-alkyl-3- methylimidazolium bromide ILs, [C n mim]Br (n = 2, 4, 6, 8, and 10). It is observed that crystallite size is significantly less when ILs are used compared to the synthesis without ILs keeping the other reaction parameters the same. At 150 °C, when no IL is used, pure tetragonal form of β-In2S3 appears however in the presence of [Cnmim]Br [n = 2,4], at the same reaction condition, a pure cubic phase crystallizes. However, in case of methylimidazolium bromides with longer pendant alkyl chains such as hexyl (C6), octyl (C8) or decyl (C10), nanoparticles of the tetragonal polymorph form. Likewise, judicious choice of reaction temperature and precursors has a profound effect to obtain phase pure and morphology controlled nanocrystals. Furthermore, the adsorption driven catalytic and photocatalytic activity of as-prepared nanosized indium sulfide is confirmed by studying the degradation of crystal violet (CV) dye in the presence of dark and visible light. A maximum of 94.8% catalytic efficiency is obtained for the In2S3 nanocrystals using tetramethylammonium bromide (TMAB) ionic liquid.