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

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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.