Size-tunable UV Luminescence from Organic-capped Si Nanoparticles-Developed Heterogeneous Interface for Precise Light Emission Control

本研究首次证明了以有机单层（即Si/有机核/壳纳米颗粒）为末端的纳米晶体的尺寸依赖性紫外PL特征。观察这种独特的PL特征需要满足两个参数；(1)芯的尺寸被控制在直径小于2.5 nm的范围内，(2)晶体芯的表面被高密度的单层覆盖，以获得未氧化的Si纳米颗粒。可以清楚地看到，芯的尺寸控制可以在300 ~ 400 nm范围内实现波长可调的光发射。虽然由于低单分子覆盖率导致氧化表面区域的存在导致了剧烈的红移PL特征，但单分子层头基团（即碳硅和氧硅）的差异并不影响光吸收和发射性能，这表明我们有很多选择的优势，可以选择合成各种有机修饰纳米颗粒的反应路线。这些结果将为硅作为环保发光材料开辟一个新的前沿。

The present study demonstrated the size-dependent UV PL features from the nanocrystals terminated with organic monolayers (i.e., Si/organic core/shell nanoparticles) for the first time. Two parameters should be satisfied to observe such unique PL features ; (i) the size of cores is controlled in diameter range less than 2.5 nm, and (ii) surface of the crystalline cores is covered with high density of monolayers to give nonoxidized Si nanoparticles. It can be clearly seen that the size control of cores allows the wavelength-tunable light emission in the range from 300 to 400 nm. Although the presence of oxidized surface region due to lower monomolecular coverage causes the drastic redshifted PL features, the difference in head group of monolayers, i.e., carbon-silicon and oxygen-silicon, does not influence on light absorption and emission properties, suggesting an advantage that we have many options for choosing a reaction route to synthesize a variety of organic-modified nanoparticles. These results would be open a new frontier for silicon as environmentally-friendly light emitters.