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Laser-driven structural transformations in dextran- <i>graft</i> -PNIPAM copolymer/Au nanoparticles hybrid nanosystem: the role of plasmon heating and attractive optical forces
摘要： Laser induced structural transformations in a dextran grafted-poly(N-isopropylacrylamide) copolymer/Au nanoparticles (D-g-PNIPAM/AuNPs) hybrid nanosystem in water have been observed. The laser induced local plasmonic heating of Au NPs leads to Lower Critical Solution Temperature (LCST) phase transition in D-g-PNIPAM/AuNPs macromolecules accompanied by their shrinking and aggregation. The hysteresis non-reversible character of the structural transformation in D-g-PNIPAM/AuNPs system has been observed at the decrease of laser intensity, i.e. the aggregates remains in solution after the turn-off the laser illumination. This is an essential difference comparing to the case of usual heating–cooling cycles when there is no formation of aggregates and structural transformations are reversible. Such a fundamental difference has been rationalized as the result of action of attractive optical forces arising due to the excitation of surface plasmons in Au NPs. The attractive plasmonic forces facilitate the formation of the aggregates and counteract their destruction. The laser induced structural transformations have been found to be very sensitive to matching conditions of the resonance of the laser light with surface plasmon resonance proving the plasmonic nature of observed phenomena.
关键词： Plasmon heating,Attractive optical forces,LCST phase transition,Au nanoparticles,Laser induced structural transformations,Dextran-graft-PNIPAM copolymer
更新于2025-11-19 16:56:42
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Solar steam generation enabled by bubbly flow nanofluids
摘要： Plasmonic nanofluids are recently explored to promote steam generation, showing great promise of such fluids for solar thermal applications. However, plasmonic nanoparticles are opaque and the nanofluids require high mass concentration to achieve efficient evaporation, which in turn leads to parasitic light absorption for the underlying particles. In this work, we introduce bubbles into dilute plasmonic nanofluids to enhance solar water evaporation. The dynamic bubbles not only act as light scattering centers to extend the incident light pathway and amplify solar flux, but also provide large gas-liquid interfaces for moisture capture as well as kinetic energy from bubble bursting to improve vapor diffusion. The coupling effect between plasmonic heating and bubbly-flow humidification results in a steam generation rate of 0.72 kg m?2 h?1 under two-sun, which is about three-time higher than that of the pure water. A series of experiments under different light intensities, concentration of nanofluids, gas flow rates as well as photothermal materials such as carbon nanotubes (CNTs) and magnetic Fe3O4 nanoparticles are also conducted to verify the concept. It is concluded that all the nanofluids enhance the steam generation process, and the bubbly flow nanofluids can be further improved the performance. This work provides an original insight on the bubbly flow nanofluids for solar vapor generation, and stands for a basis to design scalable solar evaporators from accessible raw materials.
关键词： Solar energy,Bubbly flow,Plasmon heating,Steam generation,Nanofluids
更新于2025-09-11 14:15:04