Synthesis of Silicon Nanoparticles from Rice Husk and their Use as Sustainable Fluorophores for White Light Emission

Silicon nanoparticles (Si NPs) exhibiting observable luminescence have many electronic, optical, and biological applications. Owing to reduced toxicity, they can be used as cheap and environmentally friendly alternatives for cadmium containing quantum dots, organic dyes, and rare earth-based expensive phosphors. Here, we report an inexpensive silicon precursor, namely rice husk, which has been employed for the synthesis of Si NPs by rapid microwave heating. The Si NPs of similar to 4.9 nm diameter exhibit observable green luminescence with a quantum yield of similar to 60%. They show robust storage stability and photostability and have constant luminescence during long-term UV irradiation extending over 48 h, in contrast to other luminescent materials such as quantum dots and organic dyes which quenched their emission over this time window. Green luminescent Si NPs upon mixing with synthesized red and blue luminescent Si NP species are shown to be useful for energy-efficient white light production. The resulting white light has a color coordinate of (0.31, 0.27) which is close to that of pure white light (0.33, 0.33). The performance of our white light emitting material is comparable to that of a commercial white light emitting diode (WLED) bulb and is shown to be better than that of a commercial compact fluorescent lamp (CFL).