Zwitterion-derived ligand-coated ZnO quantum dots engineered via an organometallic approach

Abstract

Wet-organometallic approaches offer a versatile platform for the synthesis of high-quality zinc oxide quantum dots (ZnO QDs), yet remain underutilised compared with conventional sol–gel approaches. In this work, we develop an organometallic strategy based on zwitterionic ligands to expand the library of surface chemistries available for ZnO nanostructures with tailored optical and colloidal properties. By employing a classical one-pot, self-supporting organometallic method with controlled variation of the oxygen source (air or water), a series of ZnO QDs stabilised with short- and long-chain betaines is obtained. The zwitterionic ligands provide enhanced solubility and excellent colloidal stability across a broad range of solvents, enabling a systematic investigation of ligand–nanocrystal interactions. We demonstrate that both the ligand structure and the synthetic pathway, namely air exposure versus controlled water addition, significantly influence particle size, surface passivation, and photoluminescence quantum yield, which reaches up to 41.8%. These results establish zwitterion-derived ligands as an effective tool for engineering highly luminescent and processable ZnO QDs, offering new opportunities for next-generation ZnO-based technologies.