Template-free synthesis of morphology- and size-controlled nano indium hydroxide

Morphology-and size-controlled In（OH）3 nanocrystals were synthesized via a novel, low-cost and low-temperature （70°C） route in the absence of any template and surfactant. The as-prepared products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and high-resolution transmission electron microscopy （HRTEM） with selected area electron diffraction （SAED）. The morphology and size of In（OH）3 nanostructures can be controlled by adjusting the reaction conditions such as the reaction time, the concen-tration of the alkali, and the alkaline source. A possible mechanism for the evolution of the morphology- and size-controlled In（OH）3 was proposed. In addition, the optical properties of the In（OH）3 prepared by this method were studied by diffuse reflection spectra （DRS） and photoluminescence （PL） spectroscopy, and the results exhibit an obvious change of adsorption edges. The thermal behaviors of the as-prepared products were also explored by thermo-gravimetric （TG） and differential scanning calorimetry （DSC） measurements. According to the results of TG-DSC, the pure phase and uniformity of the In2O3 nanocube and nanorod can be obtained by annealing In（OH）3 precur-sors directly at 300°C.

Preparation of large In(OH)3 and In2O3 particles through a seed-mediated growth method in a microreactor

Indium hydroxide(ln(OH)3)and indium oxide(ln2O3)particles are typically synthesized through chemical precipitation methods.In this study,we used a seed-mediated growth method and microreactor-based synthesis process.We synthesized cubic In(OH)3 particles with a crystal size of 172 nm from an 5%(w/v)indium chloride solution.The In2O3 particles synthesized through the thermal decomposition of In(OH)3 particles featured crystals up to 90 nm in size with an average size of 73 nm,which were much larger than the 20-30 nm In2O3 particles synthesized by a traditional precipitation method.The concentrations of the seed and growth solutions were varied from 1%to 7%(w/v).The crystal size of the particles increased with the concentration of the seed and growth solutions;this tendency was the opposite to that observed for the precipitation method.Through the use of a 5%(w/v)seed solution,the flow rate of the growth solution was varied from 1 to 10mL/min,and the resulting crystal size decreased as the flow rate was increased.To understand the reasons for this trend,the growth rate of the crystals was determined at different flow rates(i.e.,1,5,and 10 mL/min).A growth model consistent with the experimental results was established,which demonstrated that slow addition of the growth solution was beneficial for preparing large indium hydroxide particles.