Controllable synthesis and characterization of In2O3 nanopowder in the NH4Ac-HCl buffer system

Abstract

In response to the severe agglomeration and poor dispersibility of indium oxide prepared by the chemical precipitation method, this study investigates the synthesis of In₂O₃ within the NH₄Ac-HCl buffer solution system. SEM, XRD, and other characterization techniques were employed to study the effects of buffer solution pH and feeding method on the morphology and particle size of the indium oxide powder, as well as to characterize their physical and chemical properties. The results indicated that the introduction of the NH₄Ac-HCl buffer system into the reaction solution effectively inhibits nucleation and promotes the growth of crystal nuclei, thereby reducing particle agglomeration. By maintaining the buffer system's pH within a narrow range of 3.5–4.5, we achieved the synthesis of spherical indium oxide particles with an average diameter of 60 nm. These particles demonstrate high crystallinity and are devoid of agglomeration. Moreover, the buffer system alters the optical characteristics of In₂O₃, narrowing its direct band gap from 3.20 eV to 2.95 eV. Notably, In₂O₃ synthesized at a pH of 4.5 exhibits the lowest intensity of photoluminescence (PL) emission peaks, suggesting a higher level of crystalline integrity and a lower incidence of defects. Photocatalytic degradation studies provide further validation of our findings. At a pH of 4.5 within the buffer system, the degradation rate of indium oxide for methylene blue (MB) is measured to be 55 ± 1 %, which is significantly lower than the degradation rate of 93 ± 1 % observed in the control system.