Study On The Properties And Applications Of Fluorescent Silicon Nanoparticles

Recently, silicon nanoparticles (Si NPs) have been attracting increasingly intensive interest in many fields. This booming prospect arises from its intrinsic advantages such as high abundance, low cost, minimal toxicity, favorable biocompatibility and compatibility with silicon technologies. When desirable properties are obtained, Si NPs have been widely accepted as a potentially promising alternative material to the typical heavy-metal contained II-VI quantum dots (QDs) in various areas such as optoelectronic and biomedical applications. However, when it comes to the optical properties, Si NPs still fall behind the direct band gap based QDs (for example, relative lower photoluminescence efficiency). For Si NPs, therefore, the crucial issues remain to seek for effective ways to improve the optical properties and further tap the potential for valuable applications.In this work, we report fabrication of ultrabright water-dispersible silicon nanoparticles (Si NPs) with quantum yields up to 75% through a novel designed chemical surface modification. Unprecedented ultrabright fluorescence can be easily obtained through a simple one-pot surface modification, which improves the photoluminescent quantum yields of Si NPs from 8% to 75% and meanwhile makes Si NPs water-dispersible. Different organic molecules were used to surface modify the Si NPs and we further studied the impact of capping agents’ structure on Si NPs’ optical properties.Meanwhile, the underlying mechanisms of the modified Si NPs’ultrabright fluorescence was further investigated through time-correlated single photon counting (TCSPC) and femtosecond time-resolved PL and absorption techniques. An emergence of a single and uncommon highly emissive recombination channel across the entire NP ensemble was demonstrated, which is induced by such surface modification.In addition, the application of our surface-modified Si NPs was further broadened. First, the extended relative long fluorescent lifetime with a mono-exponential decay makes such surface-modified Si NPs a suitable material for applications involving lifetime measurements. Experimental results demonstrate that the surface-modified Si QDs can be utilized as an extraordinary nanothermometer through fluorescence lifetime imaging. On the other hand, a novel highly emissive, air stable and large scalable Si NPs based light emitting films were fabricated for the first time which has great potential for light-emitting and sensing applications.