Plasmonic Nanostructure And Nanochemistry

In recent years,photochemistry driven by visible light has attracted extensive attention due to its great potential in solving global energy crisis.Due to the widely tunable optical properties in the range of visible light,plasmonic nanostructures have been widely utilized in the field of photochemistry.Under the excitation of visible light,surface plasmon resonance(SPR)occurs on plasmonic nanostructures of noble metals.Valuable physical effects generated by SPR,such as thermal effect,field effect and hot carriers,can be applied to the chemical reaction process to catalyze and confine the space of the reactions,which is called plasmonic nanochemistry.However,this field of research is still in its infancy.Most studies still focus on the exploration of catalytic mechanisms and new applications using isolated plasmonic nanostructures with relatively simple resonance modes.One of the reasons is the cost and fabrication area limitations of traditional nanofabrication techniques for plasmonic nanostructures.Colloidal lithography,as an emerging nanofabrication technology,can realize large-area fabrication of various nanostructures with low cost and high efficiency.The plasmonic films constructed based on colloidal lithography technology have rich and tunable morphologies and resonance hybridization modes,which are ideal carriers for plasmonic nanochemistry and are expected to bring new opportunities and more possibilities to this field.Based on the background,we prepared a variety of large-area plasmonic nanostructure array films based on polymer colloidal lithography technology,which were applied to the research of plasmonic nanochemistry,aiming to explore the reaction mechanism of plasmonic nanochemistry and broaden the application field.In Chapter 2,“hedgehog-like” hierarchical nanocone structure arrays were fabricated by colloidal lithography technology and applied to in-situ SERS study of plasmonic nanochemistry.Silver nanocones are designed on a three-dimensional polystyrene microsphere array,forming a hierarchical nanocone array.And the structure can form plasmonic hot spots with high density in the laser irradiation area.Based on the tip enhancement effect of the nanocone array and the high utilization of light in three-dimensional space,the hierarchical nanocone structure exhibited strong surface-enhanced Raman scattering(SERS)effect and plasmonic catalytic performance.Further combining the ultrasensitive detection properties and catalytic performance,the structure enabled an in-situ SERS study of a plasmon-induced photocatalytic degradation reaction.In this chapter,not only the degradation process of methylene blue molecule was observed,but also the detailed mechanism of the reaction was revealed.Therefore,based on the bifunctional properties,hierarchical nanocone arrays have great potential for application in SERS and in situ SERS study.In Chapter 3,we utilized the nanochemical reaction confined by SPR effect to precisely induce the localization and growth of plasmonic nanoparticles,and established a novel in-situ chemical patterning technique that can construct multiscale ordered nanoparticle assembly arrays in large areas.Using the gold nanohole array as a carrier of plasmonic nanochemistry,silver nanoparticles grew completely following the maximum plasmonic field region,forming a silver nanoparticle assembly array with controllable morphology.Combined with conventional photolithography technique to control the reaction sites,multiscale patterns from macroscopic to submicron scales can be accurately obtained.The regiospecifically generated silver nanoparticle assemblies can be used as excellent SERS substrates to realize quantitative detection of analytes and Raman imaging functions,which were further applied as multilevel encrypted labels.Meanwhile,the patterning technique shows good versatility,which can realize the construction of gold nanoparticle assembly arrays and polypyrrole nanodisk arrays,and can be applied to flexible and curved substrates to realize the patterning process.In general,a low-cost,high-throughput,and facile in-situ chemical patterning technique was developed which could be an ideal candidate for the fabrication of next-generation anti-counterfeiting labels,sensors,and flexible electronic devices.In Chapter 4,two kinds of novel chiral plasmonic metamaterials were fabricated and introduced into the study of plasmonic nanochemistry.By combining colloidal lithography and glancing angle deposition techniques,we simultaneously fabricated chiral hollow nanovolcano arrays and chiral hollow nanoshells with chiroptical properties.The chirality of both originates from the asymmetric charge oscillation and electric field distribution.And the chiral response can be regulated by adjusting the morphology of the microstructure.At the same time,the chiral plasmonic cavity provided by the two chiral nanostructures shows important application value for chiral sensing.In addition,the chiral nanovolcano array film can be detached from the original substrate,and prepared into flexible chiral metamaterials through further transfer operations.The chiral hollow nanoshells can be integrated into hydrogel to form a reconfigurable flexible chiral material,which lays the foundation for its practical application.Further,we studied the photodegradation reactions catalyzed by hollow nanovolcano arrays with opposite chirality under the same circularly polarized light.It can be found that in the catalytic reaction based on a circularly polarized light,the reaction rate is selective to the handedness of the chiral metamaterial.In this chapter,two kinds of novel chiral plasmonic metamaterials were constructed,which have great potential in chiral sensing and realization of the controllability in plasmonic nanochemistry.