Random lasing enhancement effect on SiO2 anchored CdSe/ZnS quantum dots

Abstract

This article explores the characteristics of random laser emission in CdSe/ZnS quantum dots (QDs) anchored by SiO₂, demonstrating the achievement of low thresholds and high stability random laser. The incorporation of CdSe/ZnS QDs onto the SiO₂ surface builds SiO₂-QDs (SQ). SQ promotes the dispersion of quantum dots, effectively reducing Förster resonance energy transfer (FRET) and fluorescence quenching. In this system, SiO₂ acts as a scattering particle, providing multiple scattering events for random laser generation, and consequently achieving a low threshold for random laser emission. Various SiO₂ nanoparticles with average sizes of 120 nm, 200 nm, 300 nm, 450 nm, and 600 nm are synthesized, and corresponding SQ are prepared. The random laser thresholds exhibit a gradual decrease with increasing SiO₂ particle size, measuring 2.3 mJ/cm² (120 nm SiO₂) to 1.4 mJ/cm² (600 nm SiO₂). The above trend can be attributed to the concurrent increase in the scattering cross-section of SiO₂ particles, leading to enhanced multiple scattering intensities within the random laser system. Furthermore, a SiO₂-QDs-SiO₂ (SQS) is developed by encapsulating SQ with a silicon shell, offering protection against environmental factors such as water and oxygen. The additional out layer improves the stability of SQS, resulting in a random laser with both low threshold and high stability.