Temperature and Viscosity Effects on the Photoluminescence Properties of Alkyl-Capped Silicon Nanoparticles Dispersed in Nonpolar Liquids

Alkyl-capped silicon nanoparticles (Ac-Si NPs) with diameter size ranging from 4 to 10 nm were prepared by an anodic etching method followed by a surface hydrosililation reaction. Thanks to this surface functionalization, these Ac-Si NPs were homogeneously dispersed in nonpolar liquids (NPLs). They exhibit a visible photoluminescence (PL) as a result of the quantum confinement effect. An important red shift of the PL peak position with temperature of almost 1 meV/K was obtained between 303 and 390 K. This dependence is much higher than most of the literature results for Si NPs. The influence of the viscosity of the NPLs on the red shift value is discussed considering energy transfer between the nanoparticles, which is confirmed by the determination of their mean free path as a function of temperature and the viscosity of the liquids. The high PL thermal sensitivity of the Ac-Si NPs allows consideration of their application as nanothermometers.