多极子局域表面等离子体共振吸收体的制备和光热性能研究

Synthesis and Photothermal Performances of Photoabsorbers with Multiple Plasmonic Resonance Peaks

贵金属纳米材料的局域表面等离子体共振(localized surface plasmon resonance,LSPR)在入射光辐照时,形成强大的高温热点(hot-spots),驱动周围介质快速发生汽化相变,快速产生高温光热蒸汽。LSPR吸收体的光学特性具有形貌依存性,其吸收光谱在紫外-可见-近红外光内可大范围调控,但单一形貌的LSPR吸收体的吸收光谱覆盖范围有限,影响其光热转换效率,改进和拓宽吸收体的吸收光谱一直是光热领域的难题。纳米簇、自组装等组合体和核壳等复合体形成的耦合增益效应,可以增强LSPR吸收强度或拓宽吸收范围。本文通过改进核壳的制备方法,首先在核表面负载Ag纳米晶作为壳层的生长基点,再通过外延生长形成非连续壳层,壳层的临近纳米晶产生耦合增益效应,形成多极子等离子体共振吸收峰,实现单个吸收体的多个吸收峰特性,拓宽吸收体的吸收光谱,为改进单个吸收体的光吸收体特性提供了一种可行策略。多极子共振吸收体的综合光热性能优异,室外光热实验表明,多极子共振吸收体可快速、高效产生高温过热蒸汽,同时宽吸收范围的多极子共振吸收体可高效俘获低能量密度的太阳光,日均综合光热性能优异,日均光热转换效率达65%以上。

The noble metallic nanomaterials form powerful hot-spots thanks to the localized surface plasmon resonance(LSPR)effect with irradiation,which drives the surrounding medium to vaporize rapidly,and generates high temperature steam in ultrafast timescale.The various noble metallic nanostructures based on LSPR are developed and are able to widely tune the peak position shift of LSPR in UV-vis-NIR due to the geometrically tunable optical properties,while the sole kind of geometric structure of metallic plasmon resonance peak is indeed narrow coverage spectrum.The narrow spectra of LSPR absorber seriously limit the performance of harvesting solar energy.Broadening the scope of plasmonic resonance absorbing spectra and improving the optical properties of the individual photoabsorber is a hard challenge.The coupling effect on localized plasmons resonance in the junctions and neighbouring interfaces between adjacent metallic nanostructures,coupled metallic nanoparticles,the clusters,assembly,and nanoshells,which engenders multiple plasmonic resonance peaks.Herein,by improving the preparation of nanoshell,the Ag nanocrystals were covered on the core to form seeds for the growth of the shell,these nanocrystals play a significant role in the subsequent epitaxial growth of shells,the neighboring Ag nanoparticles form integral shell appear coupling effect of collective plasmon resonance with multiple absorbing peaks.Thus the sort of photoabsorbers with multiple plasmonic resonance peaks(multiple-peaks plasmon resonance absorber)provided the method for broadening the scope of plasmonic resonance absorbing spectra and improving the optical properties.Photoabsorbers with multiple plasmonic resonance peaks display excellent overall performances of photothermal conversion,and enable to efficiently capture the weak sunlight irradiation.The daytime average efficiency of photothermal conversion was above 65%.