SnO2 nanoparticles are regarded as attractive, functional materials because of their versatile applications. SnO2 nanoaggregates with single-nanometer-scale lumpy surfaces provide opportunities to enhance hetero-material interfacial areas, leading to the performance improvement of materials and devices. For the first time, we demonstrate that SnO2 nanoaggregates with oxygen vacancies can be produced by a simple, low-temperature sol-gel approach combined with freeze-drying. We characterize the initiation of the low-temperature crystal growth of the obtained SnO2 nanoaggregates using high-resolution transmission electron microscopy (HRTEM). The results indicate that Sn (II) hydroxide precursors are converted into submicrometer-scale nanoaggregates consisting of uniform SnO2 spherical nanocrystals (2~5 nm in size). As the sol-gel reaction time increases, further crystallization is observed through the neighboring particles in a confined part of the aggregates, while the specific surface areas of the SnO2 samples increase concomitantly. In addition, X-ray photoelectron spectroscopy (XPS) measurements suggest that Sn (II) ions exist in the SnO2 samples when the reactions are stopped after a short time or when a relatively high concentration of Sn (II) is involved in the corresponding sol-gel reactions. Understanding this low-temperature growth of 3D SnO2 will provide new avenues for developing and producing high-performance, photofunctional nanomaterials via a cost-effective and scalable method.

Perovskite solar cells, specifically using SnO2 nanoparticles, have been extensively researched and are proving to be extremely promising in the field of renewable energy by increasing a solar cell's overall efficiency and lowering the cost of production. In this study, an experiment was performed to synthesize SnO2 nanoparticles over 8 days. Day 1 was the synthesis which included the mixing of water, tin (II) chloride, methanol, sodium carbonate and dimethylformamide and then heated in a water bath at 28 . Sampling of this solution started on day 4 of the experiment when sufficient particle growth was observed and stopped at day 8. Centrifuging, freezing, and freezedrying were used for each sample to isolate the solid product. Transmission electron microscopy and X-ray powder diffraction was used to characterize the isolated nanoparticle. The results from the X-ray powder diffraction showed that each sample consisted of SnO2 nanoparticles of different sizes. From the transmission electron microscopy on the samples showed that the overall size of the nanoparticles gradually increased during each additional synthesis day.

No abstract