Structural modification and band-gap crossover in indium selenide nanosheets

Abstract

Herein, we report on the synthesis of InSe nanosheets. We further report on the interdependency of concentration and time on the evolution of the nanosheets as well as the role of the capping agents on the crystal phase and morphology of the resultant particles. Our results show that hexagonal-like InSe nanosheets were synthesized at different optimum times depending on the amount of indium precursor. Regardless of the amount of indium precursor used, the product remained unchanged, i.e. InSe. This was attributed to the nature of the oleylamine capping agent. Oleylamine is known to be a reducing agent and in this case resulted in the reduction of In³⁺ to In²⁻ and elemental selenium to Se²⁻, thus always resulting in the formation of rhombohedral InSe nanosheets. A non-reducing 1-dodecanthiol co-surfactant was thus used. Dodecanthiol was thought to stabilize the In³⁺ ions by coordinating and forming a complex, thus preserving the 3+ oxidation state of indium, resulting in the formation of the final product of In₂Se₃ nanocrystals. The morphology of In₂Se₃ changed depending on the amount of oleylamine used. The optical properties of the InSe were further evidence that nanosheets had been synthesized due to the band gap crossover.