Department of Physics, North Dakota State University, Fargo, North Dakota 58108, United States.
ACS Appl Mater Interfaces. 2013 May 22;5(10):4233-8. doi: 10.1021/am400411a. Epub 2013 May 13.
The photoluminescence (PL) of size-purified silicon nanocrystals is measured as a function of temperature and nanoparticle size for pure nanocrystal films and polydimethylsiloxane (PDMS) nanocomposites. The temperature dependence of the bandgap is the same for both sample types, being measurably different from that of bulk silicon because of quantum confinement. Our results also suggest weaker interparticle and environmental coupling in the nanocomposites, with enhanced PL and an unexpected dependence of lifetime on size for the pure nanocrystal films at low temperatures. We interpret these results through differences in the low-temperature size dependence of the ensemble nonradiative equilibrium constants. The response of the PDMS nanocomposites provides a consistent measure of local temperature through intensity, lifetime, and wavelength in a polymer-dispersed morphology suitable for biomedical applications, and we exploit this to fabricate a small-footprint fiber-optic cryothermometer. A comparison of the two sample types offers fundamental insight into the photoluminescent behavior of silicon nanocrystal ensembles.
我们测量了经尺寸纯化的硅纳米晶的光致发光（PL），并研究了其在纯纳米晶薄膜和聚二甲基硅氧烷（PDMS）纳米复合材料中随温度和纳米颗粒尺寸的变化。两种样品类型的带隙温度依赖性相同，由于量子限制，与体硅明显不同。我们的结果还表明，纳米复合材料中颗粒间和环境间的耦合较弱，在低温下，纯纳米晶薄膜的 PL 增强，寿命对尺寸的依赖性出乎意料。我们通过低温下的非辐射平衡常数的整体尺寸依赖性的差异来解释这些结果。PDMS 纳米复合材料的响应通过强度、寿命和波长在聚合物分散形态中提供了局部温度的一致测量，适用于生物医学应用，我们利用这一点来制造小尺寸的光纤低温计。两种样品类型的比较为硅纳米晶系的发光行为提供了基本的见解。
