Functionalized Silicon Nanoparticles—Gram-scale Synthesis and Optical Properties

Silicon nanoparticles (Si NPs) are highly attractive materials for typical quantum dots functions, such as in light-emitting and bioimaging applications, owing to silicon’s intrinsic merits of minimal toxicity, low cost, high abundance, and easy and highly stable functionalization. Especially non-oxidized Si NPs with a covalently bound coating serve well in these respects, given the minimization of surface defects upon hydrosilylation of H-terminated Si NPs. However, to date, methods to obtain such H-terminated Si NPs is still not easy. Herein, we report a new synthetic method to produce size-tunable robust, highly crystalline H-terminated Si NPs (4 – 9 nm) using microwave irradiation within 5 min at temperatures between 25 – 200 degrees C, and their further covalent functionalization. The key step to obtain highly fluorescent (quantum yield of 7 – 16%) green-red Si NPs in one simple step is the reduction of triethoxysilane and (+)-sodium L-ascorbate, yielding routinely ∼1 g H-Si NPs via a highly scalable route in 5-15 min. Subsequent functionalization via hydrosilylation yielded Si NPs with an emission quantum yield of 12-14%. This approach can be used to easily produce high-quality H-Si NPs in gram-scale quantities, which brings the application of functionalized Si NPs significantly closer.