Sequential coating upconversion NaYF₄:Yb,Tm nanocrystals with SiO₂ and ZnO layers for NIR-driven photocatalytic and antibacterial applications

ZnO is one of the most promising materials for both photocatalytic and antibacterial applications, but its wide bandgap requires the excitation of UV light which limits their applications under visible and NIR bands. Herein, we demonstrate a facile approach to synthesize core-shell-shell hybrid nanoparticles consisting of hexagonal NaYF₄:Yb,Tm, amorphous SiO₂ and wurtzite ZnO. The upconversion nanocrystals are used as the core seeds and sequentially coated with an insulting shell and a semiconductor layer. Such hybrid nanoparticles can efficiently utilize the NIR light through the upconverting process, and display notable photocatalytic performance and antibacterial activity under NIR irradiation. The developed NaYF₄:Yb,Tm@SiO₂@ZnO nanoparticles are characterized with TEM, XRD, EDS, XPS and PL spectra, and their working mechanism is also elucidated. - Highlights: • Core-shell NaYF₄:Yb,Tm@SiO₂@TiO₂ NPs were synthesized via a sequential coating method. • Hybrid NaYF₄:Yb,Tm@SiO₂@TiO₂ NPs show NIR-light enhanced photocatalytic activity. • NIR-driven antibacterial performance has been realized with NaYF₄:Yb,Tm@SiO₂@TiO₂ NPs. • Working mechanism of the hybrid photocatalysts as antibacterial agents was proposed.