Photoluminescence behavior of silicon nanocrystals: Role of surface chemistry and size

In this communication, we demonstrate that photoluminescence (PL) emission of silicon nanoparticles is not only influenced by their size but also depends on their surface chemistry. The emission of silicon nanoparticles was finely tuned within the visible spectrum by etching them in a mixture of hydrofluoric acid (HF) and nitric acid (HNO₃) for different times. Our results indicate that red-to-green emissions of silicon nanoparticles are associated with the quantum size effects, while the blue emission originates from the defect states. Functionalization of etched silicon nanoparticles was achieved by a photoinitiated hydrosilylation process. This alters the surface chemistry of silicon nanoparticles, while maintaining their size. Despite having similar size, functionalized silicon nanoparticles show a shift in their emission spectrum with respect to freshly etched nanoparticles. Functionalization of silicon nanoparticles with different organic molecules indicates that the shift occurs irrespective of the type of organic ligands on silicon surface.