Department of Physics and Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, USA.
ACS Nano. 2012 Aug 28;6(8):7389-96. doi: 10.1021/nn302524k. Epub 2012 Jul 25.
We report on the quantum yield, photoluminescence (PL) lifetime, and ensemble photoluminescent stability of highly monodisperse plasma-synthesized silicon nanocrystals (SiNCs) prepared though density-gradient ultracentrifugation in mixed organic solvents. Improved size uniformity leads to a reduction in PL line width and the emergence of entropic order in dry nanocrystal films. We find excellent agreement with the anticipated trends of quantum confinement in nanocrystalline silicon, with a solution quantum yield that is independent of nanocrystal size for the larger fractions but decreases dramatically with size for the smaller fractions. We also find a significant PL enhancement in films assembled from the fractions, and we use a combination of measurement, simulation, and modeling to link this "brightening" to a temporally enhanced quantum yield arising from SiNC interactions in ordered ensembles of monodisperse nanocrystals. Using an appropriate excitation scheme, we exploit this enhancement to achieve photostable emission.
我们报告了通过在混合有机溶剂中通过密度梯度超速离心制备的高度单分散等离子体合成硅纳米晶体（SiNC）的量子产率、光致发光（PL）寿命和整体 PL 稳定性。尺寸均匀性的提高导致 PL 线宽减小，并且在干燥纳米晶体薄膜中出现熵序。我们发现与纳米晶硅中量子限制的预期趋势非常吻合，对于较大的分数，溶液量子产率与纳米晶尺寸无关，但对于较小的分数，量子产率随尺寸急剧下降。我们还发现从这些分数中组装的薄膜的 PL 显著增强，我们使用测量、模拟和建模的组合将这种“增亮”与有序单分散纳米晶体的纳米晶体相互作用引起的暂时增强的量子产率联系起来。通过使用适当的激发方案，我们利用这种增强来实现稳定的光致发光。
