Dual emissive and stable surface-capped silica based nanoparticles for white light emission

Abstract

There is an emerging thrust to develop intrinsic white light emitting materials that surpass critical issues of color balance, low color-rendering index, thermal stability, and a bluish tinge displayed by conventional multi-phosphor composite materials. In particular, the luminescent Silica-based nanoparticles (NPs) have drawn attention owing to their abundance and potential applications, such as in optoelectronic devices, solar cells, and batteries. In this work, stable phenothiazine capped-SiO2 nanoparticles (PTZ capped-SiO2 NPs) with an average size of 24 ± 2 nm have been synthesized that exhibit intrinsic white light emission and have comprehensively investigated interactions of ligands on Silica core and underlying charge transfer mechanism. The dual emission has been observed, spanning over 400 to beyond 800 nm (visible to the NIR region). The emission measured at different excitation wavelengths reveals enhancement of red emission, indicating efficient CT emission, which is facilitated by strong electron donor and conformational changes capability of the phenothiazine ligand. Taking into account the excellent photo/thermal stability of PTZ capped-SiO2 NPs (up to 30 days) observed, a white LED prototype was successfully fabricated that exhibits cool white light (CIE: 0.31, 0.32) with excellent CRI (Ra) 91 and CCT 7029 K.