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

Abstract

Phase tuned quantum confined InS 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 InS 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, [Cmim]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-InS appears however in the presence of [Cmim]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 (C), octyl (C) or decyl (C), 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 InS nanocrystals using tetramethylammonium bromide (TMAB) ionic liquid.

Tuning the Crystal Phase and Morphology of the Photoluminescent Indium Sulphide Nanocrystals and Their Adsorption‐Based Catalytic and Photocatalytic Applications

“…Recently, it is noticed that adsorption has significant effect on enhancing the photocatalytic activity of the semiconducting nanomaterials and nanocomposite materials. Adsorption process depends on the many factors mainly morphology, high surface area, pore volume, intra‐particles mesoporosity etc …”

“…Therefore, recently non‐toxic element containing semiconducting nanomaterials are being explored for photo‐catalytically degradation of organic pollutants in the presence of visible or sunlight. Amongst them, indium sulphide (In 2 S 3 ) is a non‐toxic, n‐type semiconducting nanomaterial of III–VI group and exists in three polymorphic forms at ambient conditions . A cubic, defective structure which is stable up to 693 K is called α‐In 2 S 3 .…”

“…A cubic, defective structure which is stable up to 693 K is called α‐In 2 S 3 . β‐In 2 S 3 is a defective spinel structure and stable up to 1027 K where as γ‐ In 2 S 3 is a hexagonal layered structure and stable above 1027 K . Now‐a‐days it is used as a promising alternative of cadmium sulphide (CdS) and cadmium selenide (CdSe) semiconducting nanomaterials in Cu(In, Ga)Se 2 (CIGS) based solar cells .…”

“…Consequently, there are several synthesis methods of In 2 S 3 nanomaterials such as hydrothermal, chemical bath deposition, solution phase synthesis, solvothermal,, ionic liquid assisted solvothermal, glancing angle deposition, chemical spray pyrolysis, etc. As a result, various types of morphology have been noticed for In 2 S 3 for instances nanorods, nanobelt, microspheres, floriated, walnut, stacked superstructures, nanosheets etc. On the other hand, ionic liquids (ILs) which are also known as green and designer solvent, usually consist of organic cations and large anions; exist in liquid state at ambient conditions.…”

“…Synthesis parameters like source of precursors, capping agent, reaction time, solvent and temperature not only govern the tuning of phase but also impose significant impact on size, morphology and optical property of the as‐synthesized nanomaterials ,. For examples, Zou et al.…”