Intensifying solar-thermal harvest of low-dimension biologic nanostructures for electric power and solar desalination

High-efficiency solar harvest and solar-thermal conversion have been targeted in modern sustainable energy science for diverse potential applications. However, broad applications with inorganic nanomaterials as solar-nanoheaters have suffered from low conversion efficiency, potential noxiousness and complicated synthesis procedures. Meanwhile, living organisms rely on delicate bio-synthesis of bio-macromolecules to produce organic bio-melanins with optimal nanostructures and solar-thermal properties for survival from harsh environments. Followed by this inspiration, alginate, one marine polysaccharide, is used to alter the polydopamine nanostructures, one artificial bio-melanin, from nanoparticles to high-aspect-ratio nanofibrils (diameter similar to 40 nm and aspect ratio up to 120 nm). During polymerization, alginate not only increases structural order (e.g. pi-pi conjugation) of polydopamine oligomers within their protoparticles, but also leads to linear consolidation of protoparticles. Polydopamine nanofibrils are found to exhibit super absorbance and high solar-thermal conversion efficiency (similar to 86%) in full-range solar spectrum, being superior to conventional polydopamine nano-particles and comparable to graphene and carbon nanotubes. Thus these biological nanofibrils may offer a promising platform for high-efficiency solar-energy harvest applicable in solar evaporative desalination, solar electric power etc.