One-step solvothermal synthesis of Ni2+ doped indium oxide nanocrystals and evidences of their in situgrowth mechanism

Abstract

Ni²⁺ doped In₂O₃ has the potential use in transparent spintronic devices as a kind of dilute magnetic semiconductor. In this paper, Ni²⁺ doped In₂O₃ nanocrystals with cube shapes (about 18 nm) are directly synthesized by a simple one-step solvothermal method, free of any dispersants, surfactants, templates and postannealing treatment. The influences of reaction solvents, solvothermal time, reaction temperatures and alkaline concentrations on phase transitions and morphological evolutions are systematically investigated. The concrete formation mechanisms for the Ni²⁺ doped In₂O₃ phase are suggested based on stepwise dehydrations of Ni²⁺ doped In(OH)₃ precursors while the appearance of a metastable Ni²⁺ doped InOOH intermediate phase plays an important role in this conversion and is also supported by thermodynamic data. The in situgrowth mechanisms for the formation of regular nanocubes are proposed based on detailed evidences of morphological evolutions with reaction time. In addition, the infrared and magnetic properties of Ni²⁺ doped In₂O₃ nanocrystals are also characterized. Our studies provide a time-saving and easy way to synthesize other transition-metal ion doped In₂O₃ nanomaterials by the one-step solvothermal route.