Synthesis of Monodisperse Silicon Quantum Dots Through a K-Naphthalide Reduction Route

Abstract

Si quantum dots (Si q-dots) with a size below ~5 nm have great potential in electronics and photovoltaics and are candidate materials for down conversion of light due to their strong photoluminescence (PL) properties. Proper control of size and size distribution as well as the surface characteristics of the Si q-dots are critical for applications in order to control the PL response. Here we report on the synthesis of Si q-dots by a chemical route using potassium-naphthalide as a reducing agent. A narrow size distribution of the Si q-dots, with size in the range from 3 to 30 nm, was achieved by controlling the concentration of the reduction agent, the concentration of silicon tetrachloride (SiCl₄) precursor, temperature and the reaction time. The crystallinity and the narrow size distribution of Si q-dots were demonstrated by electron microscopy and electron diffraction. The optical absorption and PL response in the blue region of the visible spectrum is reported for 3.1 ± 0.6 nm octanoxy capped Si q-dots and 4.2 ± 1.4 nm methoxy capped Si q-dots in 1,2-dimethoxyethane solution. A quantum efficiency of (1.63 ± 0.16) × 10⁻³% was detected for the octanoxy terminated Si q-dots.