On the formation of nanocrystalline bimodal mesoporous In 2O 3 prepared by surfactant-assisted templating sol–gel process

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Nanocrystalline mesoporous In 2O 3 with bimodal pore size distribution was successfully synthesized for the first time by a combined sol–gel process with surfactant-assisted templating mechanism under mild conditions. Controlled hydrolysis and condensation of indium methoxypropylate modified with acetylacetone in the presence of laurylamine hydrochloride surfactant aqueous solution eventually produced nanocrystalline In 2O 3 with bimodal mesoporous characteristic. The synthesized material was analytically characterized by thermogravimetry and differential thermal analysis (TG–DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), N 2 adsorption–desorption, and Barrett–Joyner–Halenda (BJH) pore size distribution analyses. XRD analysis revealed that the synthesized In 2O 3 possessed high crystallinity of cubic phase, which was in very good accordance with SAED analysis. The particle size of the synthesized In 2O 3 from SEM and TEM analyses was also well agreed with the crystallite size estimated from XRD analysis, suggesting the single crystal. N 2 adsorption–desorption analysis exhibited hysteresis pattern with two successive loops, indicating the existence of two types of mesopore. Narrow bimodal pore size distribution with maximum pore diameters in the mesopore region was substantiated by BJH analysis and supposed to be generated from the intra- and inter-aggregation of In 2O 3 nanoparticles. Besides, the effects of metal precursor to surfactant molar ratio and calcination condition on the bimodal mesoporous characteristic were also investigated.