One-Pot Gram-Scale Synthesis of Hydrogen-Terminated Silicon Nanoparticles

Abstract

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 nonoxidized 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 are 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 and 200 °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 of 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.

Fast room-temperature functionalization of silicon nanoparticles using alkyl silanols

“…S13 †), slightly ($1.5 nm) smaller than previously reported by Pujari et al for H-Si NPs synthesized using similar conditions. 34 High-resolution TEM of single Si NPs conrmed the crystallinity of the functionalized NPs, in line with data shown by Pujari et al 34 Additionally, the interplanar spacing of the crystalline particles was measured to be 0.31 nm in the (111) direction, and 0.19 nm in the (110) direction ( Fig. 2D and E).…”

“…Meanwhile, for a completely oxidized sample, the peak should be found at >103 eV. 34 For the silanol-coated particles, a clear peak was found at 101.8 eV, indicating that the Si NPs are partially oxidized (Fig. 5, wide scan in Fig.…”

“…† Synthesis of hydrogen-terminated silicon nanoparticles. H-Si NPs were prepared according to the protocol developed by Pujari et al 34 In brief: inside a glovebox (O 2 < 0.1 ppm, H 2 O < 0.1 ppm), 20 mg (0.10 mmol) of sodium ascorbate and 0.8 ml of DMSO were added to a microwave tube equipped with a stirrer bar. 0.2 ml (1.08 mmol) of triethoxysilane was added, aer which the tube was quickly sealed and transported to the microwave.…”

“…In this paper, we report the use of silanol compounds with a range of functional groups to passivate H-Si NPs (obtained via a microwave-based procedure developed in our group, 34 building upon earlier protocols from He's group for other types of Si NPs). 35,36 This silanol reaction showed promise due to the discovery that at Si surfaces could readily be functionalized in this manner, 37 yielding densely packed, hydrolytically stable monolayers in <1 h at room temperature.…”

Critical assessment of wet-chemical oxidation synthesis of silicon quantum dots

“…57 and 58)) and microwave-assisted Si QD syntheses (e.g. DMSO, DMF, acetonitrile at 160 C, 33 glycerol at 180 C 121 and DMF at 275 C (ref. 34)) are slightly lower.…”