Assembly-promoted photocatalysis: Three-dimensional assembly of CdS_xSe_1−x (x = 0–1) quantum dots into nanospheres with enhanced photocatalytic performance

In this paper, through an emulsion-based bottom-up self-assembly method, monodisperse CdS_xSe_1−x (x = 0–1) quantum dots (QDs) with tailoring compositions have been three-dimensionally assembled into spherical architectures in sub-micrometer sizes. UV–Vis absorption measurements revealed the enhanced light harvesting abilities of the assembled CdS_xSe_1−x spheres relative to their constituting QDs. HRTEM characterizations over the CdS_xSe_1−x assemblies suggested the existence of localized oriented adjoining of the CdS_xSe_1−x QDs and the resulting nano-twin structures that are favorable for photogenerated electron-hole separation. The quenching of photoluminescence and the improvement in IPCE after the assembly of CdS_xSe_1−x QDs provided a clue to the likely suppressed electron-hole recombination brought about by the unique architectures and interfaces derived from self-assembly. The above findings were coincided with the remarkably improved H₂ evolution activities observed for the well-assembled CdS_xSe_1−x nanospheres in photocatalytic water splitting, underpinning the importance of the alternative strategy to design advanced semiconductor photocatalysts based on architectural engineering.