Are Fluorescent Silicon Nanoparticles Formed in a One-Pot Aqueous Synthesis?

Abstract

Critical analysis of the data reported by Zhong et al. (J. Am. Chem. Soc. 2013, 135 (22), 8350–8356) is carried out. In particular, one of the main results of Zhong et al. concerning the formation of photoluminescent silicon nanoparticles (Si NPs) in an aqueous solution of (3-aminopropyl)­trimethoxysilane (APTMS) and trisodium citrate dihydrate (Na3Cit) under microwave heating is impugned. These results are reconsidered here because of what appear to be significant inaccuracies and misinterpretations that have been spread through a wide number of other subsequent publications.

Ultralong lifetime and efficient room temperature phosphorescent carbon dots through multi-confinement structure design

“…The emission from CDs@SiO 2 phosphors is hypothesized to originate from carbon luminescence centers immobilized in the Si-O network, and the emission intensity also corresponds to the CDs content 46 . The carbonyl related groups on CDs can significantly improve the spin-orbit coupling to generate stable triplet excitons (unpaired electrons), thus resulting in phosphorescence emission.…”

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

“…Firstly, it should be shown convincingly that (crystalline) Si QDs have been synthesized successfully, preferably using an appropriate combination of methods discussed below. 26,76 Secondly, it should be conrmed that these Si QDs are indeed the true origin of displayed uorescence. Careful purication and characterization are therefore essential.…”

“…Straightforward control experiments (without a source of silicon, in the case of Si QDs) would help to conrm that the observed uorescence does not originate from by-products. 76,84…”

“…Interestingly, side reactions occurring during Si QD synthesis may also induce the (majority of) uorescence and obscure results. Recently, Oliinyk et al criticized 76 the preparation of Si QDs via a one-pot microwave synthesis employing 3aminopropyltrimethoxysilane (APTMS) as the silicon source, as reported earlier by He and coworkers. 32 Their criticism focused on discrepancies concerning the XRD data when comparing with other Si QD literature, 77 the absence of XPS data, TEM images showing crystalline material that is inconsistent with silicon, and most strikingly, very comparable optical properties for materials prepared in the presence, as well as in the absence of the silicon source.…”

Fast room-temperature functionalization of silicon nanoparticles using alkyl silanols

“…42 Recently, a paper by Oliinyk et al raised the question whether Si NPs could really be formed in a microwave reaction. 43 Even though they specically doubted their formation in an aqueous solution, and suggested the formation of uorescent NPs of a carbon or hybrid composition, their investigation is also relevant here. Based on the interplanar crystal spacing found, and the silicon signal observed using XPS (vide infra), we would argue that crystalline Si NPs were indeed formed in this reaction, rather than hybrid organo-silicon or carbon NPs.…”