Construction of a direct Z-scheme ZnS quantum dot (QD)-Fe2O3 QD heterojunction/reduced graphene oxide nanocomposite with enhanced photocatalytic activity.

The novel magnetically recyclable direct Z-scheme GZxFy nanocomposites were synthesized by a simple hydrothermal method, which displayed the excellent photocatalytic activity under UV and visible light irradiation. • The GZxFy nanocomposites photocatalysts were successfully synthesized by a simple hydrothermal method. • The photocatalytic properties of the samples were investigated under UV and visible light irradiations. • The direct Z-scheme transfer of electron-hole pairs was confirmed in GZxFy nanocomposites. • An easy magnetically separable and recoverable process was achieved. A novel direct Z-scheme ZnS quantum dot (QD)-Fe 2 O 3 QD heterojunction/reduced graphene oxide (rGO) (GZxFy) nanocomposite was successfully synthesized by a simple hydrothermal method. The surface of ZnS and Fe 2 O 3 QDs was modified by COOH and OH groups, respectively. ZnS QDs can be covalently bonded with Fe 2 O 3 QDs by the dehydration reaction to form the ZnS QDs-Fe 2 O 3 QDs heterojunctions. The GZxFy nanocomposites displayed the highest photodegradation efficiency of 96.45% (40 min, UV light) and 90.17% (480 min, visible light) for methylene blue when the mass ratio of ZnS QDs to Fe 2 O 3 QDs was 1:3. The excellent photocatalytic activity could be attributed to the enhanced light-harvesting ability, high large specific surface area, efficient interfacial charge-carrier separation and transfer as well as the low charge transfer resistance. Ultraviolet photoelectron spectroscopy and radical trapping experiments were used to confirm the Z-scheme mechanism formed between ZnS QDs and Fe 2 O 3 QDs, and verify the electron transfer direction for UV or visible light-driven photocatalytic reactions. GZ1F3 nanocomposites showed the excellent superparamagnetic behavior, which enabled its rapid magnetic recycle from the solution within 95 s in a magnetic field. [ABSTRACT FROM AUTHOR]