Gas–liquid flow synthesis of Zn3N2-quantum dots

Abstract

Continuous process engineering leads production of fine chemicals to a new level of industrialisation. This study elaborates specifications, benefits and pitfalls for the biphasic, high-temperature synthesis of Zn₃N₂ quantum dots, which are made from inexpensive and earth-abundant starting materials. A micro-flow tubular reactor equipped with inline/online process sensors and a product analysis device is used. All technical requirements are fulfilled for the corrosive gas and air-sensitive starting and product materials to create a safe pilot plant for reproducible nanoparticle synthesis. The process parameter window yields tunable fluorescent nanocrystals (506–710 nm, 4–10 nm) which broadly match in quality (FWHM: 99–186 nm, QY: 15–56%) with those made in a batch approach. The transfer to a continuous synthesis practice greatly improves throughput because time is reduced as the reaction scheme can be realised in a single process step. In addition, handling effort is minimised with inline reagent dilution and optical spectroscopy which allows product adaptation by tuning of the process parameters in real-time.