Novel Flow Processes towards Water Soluble CdX Quantum Dots

The profound impact of Quantum Dots (QDs) on both the scientific community and high-tech daily applications echoes in the 2023 Nobel Prize. QDs represent a class of nanoscale semiconductors with applications deeply rooted in the digital era and in medical applications. Improving conventional preparations is therefore crucial for next-generation technologies. This thesis develops a new approach to synthesize chalcogenide precursors and their subsequent application in the continuous-flow production of CdX (X = S, Se, Te) QDs in water.

Tris(2-carboxyethyl)phosphine (TCEP) is identified as a novel water-soluble chalcogenide transfer agent, enabling the controlled formation of CdX QDs. A systematic study of TCEP=X derivatives, reaction kinetics and process parameters revealed the predominance of surface effects, consistent with a Langmuir-Hinshelwood mechanism, with surface degradation contributing to reaction slowdown, over time.

The in-situ generation of TCEP=X species is integrated into a continuous-flow platform to enhance productivity and limit precursor degradation. Reaction conditions of CdX QDs formation are studied to provide a comprehensive understanding of the reaction mechanism and high-quality QD synthesis under microfluidic regimes, then transposed under mesofluidic conditions. Furthermore, the in-depth mechanistic investigation into QD formation provided key indications on precursor complexation and nucleation-growth dynamics.

The thesis concludes with prospective efforts toward generalized nucleation-growth mechanisms and the biofunctionalization of aqueous QDs using modified biotin, highlighting their potential for biomedical applications.