Research On Controllable Fabrication Of Plasmonic Nano-structures And Efficient Utilization Of Light

In recent years,efficient manipulation for photon and electron based on surface plasmon mechanism has attracted much attentions.The results show that the excitation of surface plasmon can not only be converted into photons by radiative transition,but also can be converted into chemical energy or heat by non-radiative transition.Therefore,plasmonic nanostructures have the capability for spectrum-selectiveabsorption and photon harvesting with high-efficiency in optics,and can also control the generation,separation,transport and injection of carriers in electrics,which is expected to break through the bottlenecks in light absorption efficiency and carrier directional transport of traditional materials.All these show great potential in the field of high-efficiency light utilization,including trace-detection based on SurfaceEnhanced Raman Scattering(SERS)effect,photocatalytic purification and new energy generation,broadband light absorption and photothermal conversion,etc.The purpose of thesis is to investigate the energy relaxation process of plasmonic nanostructures excited by light through designing and preparing plasmonic nanostructures,and to further explore the mechanism and methods of precise regulation processes of light to light,light to electrics and light to heat.Furthermore,based on the different physical models involving photon and electron behaviors regulated by plasmonic nanostructures,the optoelectronic devices with mechanism innovation and performance breakthrough are realized with the help of micro-nano scale surface manipulation technology.In this text,the basic principle of surface plasmons and the physical effects after excitation and control methods are firstly introduced,and the development status of optoelectronic devices based on plasmonic nanostructure in high-efficiency light utilization is summarized.Then,the scale-span design,optimization and characterization of methods for plasmonic nanostructures preparation and their applications in the field of high-efficiency light utilization are illustrated in details.The corresponding relationship between plasmonic nanostructures control and efficient regulation mechanism for behaviors of photon and electron is highlighted.The major achievements includes the following aspects:1.Plasmonic “hot spot” effects and their application in highly sensitive SERS dectections.A “paper based” SERS substrate with superwetting(superhydrophilicsuperhydrophobic)surface and rich “hot spots” was prepared by using electrospinning,and plasma treatment combined with surface modifications of molecular binding and magnetron sputtering coatings.The local field electromagnetic enhancement brought by the plasmonic alloy nanostructures with rough surface significantly improved SERS signal,and the surface with special wetting performance could realize higher enrichment of the detected molecules,which further achieving a breakthrough in the sensitivity of traditional molecule detection.At the same time,combined with the intrinsics of electrospinning method,including controlled large-area preparation,high repeatability and low-cost,all above show great potential for application in rapid and highly sensitive "paper based" SERS substrate.2.The research for the plasmonic "hot spots" effects and thermal effects,as well as their high-efficient conversion for steam generation.A physical model of the relationship between plasmonic "hot spots" and heat generation is established,and the clear contribution of "hot spots" to the temperature rise is verified experimentally.On this basis,combined with the surface modification,the controlled transformation of the wettability of front side and reverse side of the substrate is realized,which using hydrophilic properties of nanofibers as a water supply layer located at reverse side,thus the water could be rapidly and continuously transported to the surface of hydrophobic layer at front side.The heating process is effectively localized at the air-water interface to suppress the loss caused by direct contact between substrate and bulk water.Such results provide a reliable approach for the design and fabrication of photothermal devices with fast and efficient water-steam conversion.3.Scale-span design of hot-electrons transport channel for plasmonic metalsemiconductor heterostructures and the research for thier photocatalytic performance.At the nanoscale,a photochemical reduction strategy induced by anhydrous ethanol is proposed to realize the controllable preparation of Au-P25 heterostructures,and the relationships between the nanostructure design and the efficient photoelectric conversion is studied.At the micron scale,based on the key role of dissolved oxygen in the production of reactive oxygen species which affecting photocatalytic efficiency,a solid-liquid-gas triphase photocatalytic film based on superwetting(superhydrophilicsuperhydrophobic)surface is prepared by introducing surface modifications,and the hydrophilic-hydrophobic transformation enables the dissolved oxygen in water to be continuously and rapidly replenished from the outside air.Meanwhile,the dissolved oxygen could also serve as efficient electron trapping agents,which can also regulate hot-electrons transport and further inhibit the recombination of photogenerated electron-hole pairs,thus achieving an improvement in photocatalytic efficiency.Such combined with nanostructures optimization at nano-scale and surface engineering at micron scale provides a new idea for the design of high-performance optoelectronic devices with high-efficiency photon capture and controllable electrical channels.4.The research for regulation mechanism of hot-electron’s behavior at the interface of plasmonic metal-semiconductor heterostructures.Firstly,starting from the intrinsics of P25,combining the routes of photochemical reduction and molecular binding,Au nanoparticles are selectively deposited on two different crystal phases of P25(anatase phase and rutile phase).Combined with electrochemical mesurements and photoemission spectroscopy,it is found that the separation and transport of hotelectrons in heterostructures formed by Au-anatase phas-rutile phase are much efficient than another one,and the results are analyzed by considering their band diagrams.In addition,the quality of interface that makes influence on the injection of hot-electrons is studied.Such results provide theoretical support for revealing the efficient regulation mechanism between plasmonic nanostructures and semiconductor.