Synthetic Developments of Nontoxic Quantum Dots

Semiconductor nanocrystals, or quantum dots (QDs), are candidates for biological sensing, photovoltaics, and catalysis due to their unique photophysical properties. The most studied QDs are composed of heavy metals like cadmium and lead. However, this engenders concerns over heavy metal toxicity. To address this issue, numerous studies have explored the development of nontoxic (or more accurately less toxic) quantum dots. In this Review, we select three major classes of nontoxic quantum dots composed of carbon, silicon and Group I–III–VI elements and discuss the myriad of synthetic strategies and surface modification methods to synthesize quantum dots composed of these material systems. No heavy metal here: Semiconductor quantum dots devoid of heavy/toxic elements are attractive for use in a variety of applications. The synthetic details of three major groups of nontoxic quantum dots, namely carbon, silicon and the I–III–VI group semiconductor family are reviewed. The procedures are grouped by their common features, and how various physical properties result from the synthetic protocol is elucidated when possible. Applications for nontoxic quantum dots are also discussed.