The enhanced photocatalytic inactivation of marine microorganisms over ZnO supported Ag quantum dots by the synthesis of H2O2.

The production of hydroxyl radicals has been demonstrated to improve the antifouling of marine through a photocatalytic strategy. However, only relying on the valence band of the photocatalyst to generate hydroxyl radicals is inefficient and limits the application of photocatalytic technology in the field of marine-antifouling coatings. Herein, we reported a new strategy in which Ag quantum dots are used to synthesize hydrogen peroxide (H2O2) by photocatalysis in seawater. The decomposition of the generated H2O2 to hydroxyl radicals improves the antifouling ability. Interestingly, the prominent size effect of Ag quantum dots is closely related to the yield of H2O2. We synthesized Ag quantum dots supported on ZnO and found that Ag quantum dots approximately 4 nm in size have the highest activity for H2O2 generation and undergo a 1 h photocatalytic reaction in which the concentration of H2O2 can reach 124 µg/mL. The efficiency of ZnO in inactivating marine microorganisms increased from 72.3% to 99.4% in seawater. The synthesis of H2O2 through photocatalysis based on the medium of seawater can expand the application of photocatalytic technology in the field of marine antifouling.

Morphology modulation and performance optimization of nanopetal-based Ag-modified Bi2O2CO3 as an inactivating photocatalytic material.

The use of photocatalytic technology to kill bacteria on marine vessel surface coatings has been paid more attention by research scholars. In this paper, petal-like microspheres with Ag nanoparticles were prepared by a simple one-step process combining the hydrothermal method and photodeposition. The 0.7% Ag/Bi2O2CO3 composite photocatalyst exhibited the highest photocatalytic efficiency for bacterial removal under visible light irradiation and had the highest photogenerated carrier separation efficiency, and the sterilization rate was doubled compared with that of pure Bi2O2CO3, reaching 95%. Using X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy, the existence of Ag nanoparticles was confirmed, and their size was approximately 10 nm. The surface plasmon resonance (SPR) effect of Ag nanoparticles was investigated by ultraviolet-visible diffuse reflectance spectroscopy (DRS). It was shown that the surface plasmon resonance effect of Ag improved the spectral utilization of the Ag/Bi2O2CO3 composite photocatalyst and enhanced the stability of the catalyst. This caused the Ag/Bi2O2CO3 composite photocatalyst to have superior photocatalytic activity to pure Bi2O2CO3. The results of electrochemical impedance characterization and transient photocurrent response show that 0.7% Ag/Bi2O2CO3 has a high efficiency of photogenerated carrier separation. By the free radical capture test, hydroxyl radicals were the primary active substance, and Ag+ improved the photocatalytic sterilization activity.