Dendrimer-Templated Synthesis and Characterization of Tin Oxide Quantum Dots Deposited on a Silica Glass Substrate
Dendrimer-Templated Synthesis and Characterization of Tin Oxide Quantum Dots Deposited on a Silica Glass Substrate
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DOI：
10.1021/acs.chemmater.9b01925
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发表时间：
2019-10-22
影响因子：
8.6
通讯作者：
Yamamoto, Kimihisa
中科院分区：
文献类型：
--
作者：
Inomata, Yusuke;Albrecht, Ken;Yamamoto, Kimihisa
氧化锡量子点因其低毒性和不含镉等有毒元素而受到广泛关注。本文报道了以树状大分子为模板合成可控尺寸氧化锡量子点的新方法，以及它们的电子和结构性质。采用枝状聚合物模板法在硅玻璃衬底上合成了尺寸小于2 nm、尺寸分布较小的半球形氧化锡量子点（Sn-12、Sn-28和Sn-60氧化物量子点）。由于配位环境对结构稳定性的限制，氧化锡量子点的结构不仅由Sn（IV）位组成，还由Sn（II）位组成。密度泛函理论计算表明，具有混合价态(Sn（II) + Sn(IV)）的裸氧化锡团簇比仅具有Sn（II）或Sn（IV）的团簇更稳定。合成的氧化锡量子点表现出由电子空间约束引起的量子约束效应。表示量子点无序性的Urbach尾参数随着量子点尺寸的减小而减小，尽管氧化锡的每个量子点的值都高于本体SnO2。将实验带隙能量与有效质量近似模型进行了比较，有效质量近似模型是量子约束效应的理论模型。我们发现Sn-28和Sn-60氧化物量子点的实验值与理论值一致，而Sn-12氧化物量子点的值与预测带隙能相比较低。这可能是由于Sn-12氧化物量子点的物理参数发生了变化，与Sn-28、Sn-60氧化物量子点或本体SnO2不同。这些结果表明，小型氧化锡量子点与大块或传统纳米粒子相比具有不同的结构和不同的电子性质，在催化和光学电子器件等领域具有潜在的应用前景。
Tin oxide quantum dots (QDs) have attracted much attention because of their low toxicity and the absence of cadmium and other poisonous elements. In this paper, we report the novel synthetic method for size-controlled tin oxide QDs using dendrimers as a template, and their electronic and structural properties. Hemispherical tin oxide QDs with a size below 2 nm and small size distribution were synthesized on silica glass substrates by the dendrimer-templated synthesis method (Sn-12, Sn-28 , and Sn-60 oxide QDs). The structures of the tin oxide QDs were composed not only of Sn(IV) sites, but also Sn(II) sites due to the restriction of the coordination environment to stabilize the structure. Density functional theory calculation showed that a bare tin oxide cluster with a mixed valence state (Sn(II) + Sn(IV)) is more stable than those only with Sn(II) or Sn(IV). The synthesized tin oxide QDs showed the quantum confinement effect caused by the spatial confinement of an electron. The Urbach tail parameter, expressing the disorderliness of the QDs, decreased with the reduced QD size, although the value of each tin oxide QD was higher than that of bulk SnO2. The experimental band gap energy was compared with the effective mass approximation models, which are theoretical models for the quantum confinement effect. We found that the experimental values of Sn-28 and Sn-60 oxide QDs were consistent with the theoretical values, while Sn-12 oxide QDs had a lower value compared to the predicted band gap energy. This could be attributed to the change in the physical parameters of Sn-12 oxide QDs, which are not the same as those of Sn-28, Sn-60 oxide QDs or the bulk SnO2. These results indicate that small tin oxide QDs have a different structure and different electronic properties compared to bulk or conventional nanoparticles and have potential applications in such fields as catalysis and optical and electronic devices.