Solid-state silicon nanoparticles with color-tunable photoluminescence and multifunctional applications

In this paper, a facile hydrothermal route was proposed to synthesize a bright blue-emitting solution of silicon nanoparticles (s-Si NPs) with a high photoluminescence quantum yield (PLQY) of 66%. And a self-quenching-resistant solid-state fluorescent powder of Si NPs (p-Si NPs) was obtained by freeze drying, which exhibited dual wavelengths with blue and yellow emission peaks. In addition, the blue-band emission of p-Si NPs was ascribed to the graphitizing cores, while the yellow-band emission of p-Si NPs originated from the trapping surface state. Based on this finding, a high temperature calcining strategy was proposed to obtain multicolor Si NP powders by adjusting the surface defects of p-Si NPs for the first time. A series of multicolor Si NP powders with wavelengths from blue to red was obtained by adjusting the calcination time/temperature. Structural and spectroscopic characterizations also proved that the mechanism of their PL red shift was attributed to the oxygen-related surface state, rather than the size effect. Because of their unique multicolor emission, their related multicolor light-emitting diode (LED) devices were obtained to explore their possible application in the field of solid-state lighting. Moreover, SSF-2-based films were fabricated by combining carboxymethyl cellulose (CMC) and SSF-2 powder to explore their potential application as light conversion films (LCFs) in the field of agricultural planting.