One-pot synthesis of fluorescent hybrid nanoparticles and their assembly into transparent and multi-coloured nanofilms

We developed a route for one-pot synthesis of fluorescent hybrid nanoparticles and their assembly into a nanofilm by utilizing a fusion and fission-triggered nanoreactor system based on water-in-oil “mini-emulsion”. A fluorescent nanocrystal, ZnS:Mn2+, was produced in a confined system via fusion and fission of nanodroplets induced by ultrasonication and the amount of nanocrystals formed in each nanoreactor was easily controlled. Then, in situ polymerisation allowed for encapsulation of nanocrystals inside polymer nanoparticles, leading to an efficient surface capping of nanocrystals with polymers and hence a strong light emission under UV irradiation. Also, hybrid nanoparticles with different colours could be created by tuning of Mn2+ doping into ZnS nanocrystals, which can give rise to an energy transfer from carboxylic groups of surface capping polymers to the Mn2+. These hybrid nanoparticles were then spin-coated to form hybrid nanofilms where nanocrystals were uniformly distributed. The multicolour tuning of nanofilms was achieved simply by mixing nanoparticles with ZnS-derived blue emission and those with ZnS:Mn2+-derived orange emission. We believe that our nanoreactor system would offer a viable way in creating fluorescent nanomaterials.