Incorporation of gold nanocages into electrospun nanofibers for efficient water evaporation through photothermal heating

Conventional techniques for water desalination and purification are relatively low in efficiency because they typically involve the placement of a heating unit at the bottom of the container to boil the entire liquid volume. Herein we report the incorporation of Au nanocages (AuNCs) into electrospun nanofibers of poly(vinylidene fluoride) (PVDF) for efficient water evaporation via photothermal heating. Because PVDF is highly hydrophobic, its nonwoven mat naturally floats on the surface of water. Upon irradiation with a near-infrared (NIR) laser at 808 nm, the water at the surface is heated to evaporate while the bulk remains at the ambient temperature. As such, the efficiency for water evaporation is greatly increased. To further demonstrate the potential of AuNC/PVDF nanofiber mats for solar water evaporation, we prepare AuNCs with a broad absorption peak covering the visible and NIR regions. Under natural solar irradiation (1000 W m(-2)), water evaporation efficiencies as high as 67.0% and 79.8% are achieved when using the AuNC/PVDF nanofiber mats containing AuNCs at weight percentages of 0.05% and 0.10%, respectively. The performance is comparable or even greater than most of the reported floating devices under the illumination of sun concentration systems. This new system paves the way to the design and fabrication of sustainable and scalable floating membranes for water desalination and purification. (C) 2018 Published by Elsevier Ltd.