Fabrication And Performances Of Photothermal Materials With Micro/Nano Bio-structures

Nowadays,the world is facing with severe problems of fossil fuel crisis and water shortage.It is expected to be an effective way to solve the shortage of fresh water resource and energy crisis via making full use of the widely available,clean and efficient solar energy and sea water resources.However,how to promote the energy conversion efficiency of the photothermal materials to meet the needs in applications is still recognized as an important topic in the fields of energy and materials.During the past decades,novel functional materials are greatly promoting the progress of science,technology and engineering because of their widely-spread applications in various fields.The properties and performances of the materials depend on various factors,including the intrinsic properties of components,and the micro/nano architectures as well.Hence,the proper design of fine micro/nano architectures can further promote the performances of functional materials.Now,some micro/nano hierarchical structures developed via artificial methods,could meet various application requirements in many fields,e.g.photothermal therapy,biological sensing and detection,photocatalysis,photothermal and photoelectricity conversion.However,there are still some difficulties to break through the designs and technologies during artificial fabrication.Most of the architectures are restricted to 1D,2D or simple 3D structures,which seriously restrict the investigation and development of optical functional devices.Therefore,it holds a key role in achieving the preparation of optical functional devices for superior performances by precisely exploiting novel hierarchical micro/nano-structures and importing into material devices.Thus,we modestly seek answers from nature.For the purpose of survival and propagation,creatures of animals and plants have already developed various multiscale,multidimensional and multilevel excellent micro/nano hierarchical structures,as the results of the evolutionary selection for billions of years,providing tremendous inspirations for scientific researches.Therefore,this work selects the biotemplates of butterflies and sunflower heads with different fine hierarchical micro/nano architectures,combined with three kinds of typical photothermal materials of different mechanisms,fabricates photothermal materials of noble metal(Au),noble metal-semiconductor(Au-Cu S)and porous carbon materials inheriting the pristine 3D fine micro/nano bio-structures,achieves effective broadband solar absorption and outstanding photothermal conversion efficiency for solar steam generation.What's more,the coupling effects of artificial textures with the fine hierarchical architectures and the mechanisms of promoting photothermal properties are also investigated.The main results are listed as follows:(1)The gold butterfly wings inheriting the pristine fine hierarchical bio-structures are fabricated by an electroless plating method by using C.rubi with gyroid structure and H.glaucippe with periodic lattice structure as bio-templates.Their microstructures,hydrophilicity and optical properties are investigated,and used in SERS detection and solar steam generation.The experiment results show that the SERS signal of Au gyroid is6.7-fold higher than Au lattice,demonstrating the excellent localized surface plasmon resonance(LSPR)enhancement owning to the 3D intensly distributed hotspots of gyroid structures and large scattering cross-section.The LSPR caused effective broadband light absorption enables Au gyroid a high evaporation efficiency of 74.0% under 1 sun.And the evaporation efficiency of Au lattice is 65.4%,lower than the former.The results demonstrate the superiority of gyroid structures over lattice structures in the field of plasmonic photothermal conversion.It is inspiring for the preparation of high performance photothermal materials with hierarchical architectures.(2)By templating from butterfly C.rubi with gyroid structures,T.helena with antireflection honeycomb structures and H.glaucippe with periodic lattice structures,Au-Cu S/GMs,Au-Cu S/TMs and Au-Cu S/LMs are fabricated and utilized for solar steam generation,respectively.Firstly,a series of Au-Cu S/GMs with different volume filling rate(FR?29-80%)are achieved by controlling Cu S NPs deposition time.Along with the FR increasing,the evaporation efficiency of Au-Cu S/GMs first increases and then decreases,Au-Cu S/GMs-80 with FR of 57% has the highest photothermal conversion efficiency(88.8%)under 1 sun,which realizes a dynamic balance of water absorption-evaporation of“localized evaporation effect”.FDTD simulation results demonstrates that gyroid structures possess full utilization of the space,large scattering cross-sections and effective couple with Au-Cu S plasmon components,leading to the significant enhancement of light absorption.Due to the synergistic LSPR caused by coupling effects of Au-Cu S NPs with gyroid structures,Au-Cu S/GMs possess superior light absorption capability.What's more,Au-Cu S/TMs,owning intrinsic light absorption characteristic of antireflection honeycomb structures,possess a relatively high evaporation efficiency(86.2%);The evaporation efficiency of Au-Cu S/LMs with only periodic lattice structures is the lowest(72.2%).The results provide new paths to select and regulate 3D fine hierarchical structures for improving the properties of photothermal materials.(3)Carbonized sunflower heads inheriting the fine structures with interconnected porous networks and 3D macro structures are prepared via carbonization process by using natural sunflower heads as bio-templates and utilized for photothermal water evaporation.The experimental results show that carbonized sunflower heads exhibit high evaporation efficiency of 93.7% without additional insulation devices under 1 sun irradiation.The five aspects for steam output are summarized below: efficient solar absorption and heat generation ability;continuous water absorption and transport;resistance of heat loss and thermal insulation property;good capability for reabsorbing diffuse reflection and thermal radiation;and enlarged water/air interface for steam escape.This research work develops novel utilization methods and promising applications for sunflower heads as wastes,and provides inspirations for the future design and fabrication of high-performance photothermal devices.Inspired by nature,this work achieves efficient photothermal materials via utilizing unique hierarchical micro/nano architectures of bio-templates,including butterflies,and sunflower heads.It demonstrates research methods and scientific basis for mechanism exploration and performance optimization in related fields.It also provides a reference for the design and preparation of optical functional materials with micro/nano fine hierarchical configurations,and promotes the further acquisition of efficient LSPR performance,improvement of photothermal conversion efficiency and desalination capacity.