Laser-Engineered Graphene on Wood Enables Efficient Antibacterial, Anti-Salt-Fouling, and Lipophilic-Matter-Rejection Solar Evaporation

Advances in solar steam generation have made a promise in mitigating the water scarcity problem. However, their practical use could be curtailed by the vaporized pollutants and the longevity limited by biofouling and salt-fouling that are often overlooked. Here, a flake of wood is reported to be engineered into a miniaturized solar water treatment device by a laser engraving process and demonstrates advantages over common solar systems. The device is structured to mimic the centralized water treatment plants, which contains a superhydrophilic graphene bottom layer for lipophilic organic matter rejection and antifouling, an intrinsic wood microchannels layer for water transport and thermal management, and a hydrophobic graphene top layer for solar-driven desalination while inhibiting salt deposition. The pore size of wood differentiates the water flux and hence the evaporation performance, and the balsa wood with a larger pore size possesses a higher evaporation rate of 1.6 ± 0.02 kg m^-2 h^-1 compared with pine wood. The hierarchical design achieves a solar energy conversion efficiency of 110% and a lipophilic organic matter removal efficiency of >90% and significantly improves longevity even at high salinity. This work illuminates a sustainable and cost-effective pathway for water treatment and shows potential for wastewater reuse.

Plasmon-enabled degradation of organic micropollutants in water by visible-light illumination of Janus gold nanorods

The development of sustainable methods for the degradation of pollutants in water is an ongoing critical challenge. Anthropogenic organic micropollutants such as pharmaceuticals, present in our water supplies in trace quantities, are currently not remediated by conventional treatment processes. Here, we report an initial demonstration of the oxidative degradation of organic micropollutants using specially designed nanoparticles and visible-wavelength sunlight. Gold "Janus" nanorods (Au JNRs), partially coated with silica to enhance their colloidal stability in aqueous solutions while also maintaining a partially uncoated Au surface to facilitate photocatalysis, were synthesized. Au JNRs were dispersed in an aqueous solution containing peroxydisulfate (PDS), where oxidative degradation of both simulant and actual organic micropollutants was observed. Photothermal heating, light-induced hot electron-driven charge transfer, and direct electron shuttling under dark conditions all contribute to the observed oxidation chemistry. This work not only provides an ideal platform for studying plasmonic photochemistry in aqueous medium but also opens the door for nanoengineered, solar-based methods to remediate recalcitrant micropollutants in water supplies.