Recent years have seen significant advancement in the development of Group IV semiconductor nanocrystals (NCs). Specifically, our group is interested in Ge1-xSnx alloy NCs, which display unique properties such as composition-based bandgap tunability, low-visible/near infrared luminescence, and facile solution processability. Previous studies have reported the synthesis of Ge1-xSnx alloy NCs with sizes of 1.4-23 nm, Sn compositions from 1% to 95%, and photoluminescence in the range 1.31-2.05 eV. One important application for semiconductor NCs is as bioimaging agents. Currently, the most popular bioimaging agents are organic molecular fluorophores (OMFs). However, many OMFs have problems with photodegradation and low signal-to-background ratio. Fortunately, NC-based bioimaging agents are consistently brighter and more stable than their organic counterparts. The only drawback is that many NC bioimaging agents contain highly toxic elements (Cd, Pb, etc.). Ge1-xSnx alloy NCs, then, offer improved optical properties without the threat of toxic heavy metal poisoning. An obstacle to the applicability of Ge1-xSnx alloy NCs in bioimaging is the surface functionality. As-synthesized Ge1-xSnx alloy NCs are full of surface cations and defects, which limit their optical properties. The aim of this project is to coat the NC surface with an inorganic silica shell, which will passivate defects and cations while also offering dispersibility in a polar solvent. This is accomplished through a one-pot synthesis, where TMOS, a silicate precursor, is hydrolyzed and condenses onto the surface of the core particles, which are then recovered as core-shell products in the polar DMSO phase. We characterize the properties and morphology of the product using X-ray diffraction, Raman spectroscopy, solid-state absorption, X-ray photoelectron spectroscopy, and electron microscopy to prove the stability of the product and retention of core properties.

Surface passivation of Ge1-xSnx nanocrystals by silica coating

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.