Naughty Paul

Recent progress in facet-controlled syntheses has started to produce nanocrystals with great promise as the next-generation catalysts for a variety of applications. To move from academic studies to industrial applications, however, one has to address the issue of scaling up a synthesis that has been commonly conducted in a batch format. There are two opposite approaches to scaling up the production of colloidal nanocrystals: increasing and decreasing the reaction volume. Contrary to conventional wisdom, continuous flow synthesis based on droplets is expected to provide a more practical platform for scaling up the synthesis. Here we highlight recent progress in using droplet reactors for the synthesis of colloidal noble-metal nanocrystals with controlled sizes and shapes, with an aim towards high-volume production.

Most people probably would scale up the production of colloidal nanocrystals by increasing the reaction volume. Here we demonstrate that decreasing the reaction volume with the use of a continuous flow of droplet reactors will be a more practical approach.

A gas sensor based on PbS colloidal quantum dots (CQDs) is constructed on a paper substrate, yielding flexible, rapid-response NO₂ gas sensors, fabricated from the solution phase. The devices are highly sensitive and fully recoverable at room temperature, which is attributed to the excellent access of gas molecules to the CQD surface, realized by surface ligand removal, combined with the desirable binding energy of NO₂ with the PbS CQDs.