Charge-Transfer-Tuned Optical Properties Of Plasmonic Hetero-Nanostructures And Their Applications

The collective oscillations of free charges in meteal nanocrystal will generate localized surface plasmon resonance（LSPR）with very stong light-harvesting capacity,the local field enhancement effect and hot electron injection effect of plasmon have been widely applied in many fields.By combining meteal and semiconductor to form hetero-nanostrcture,they can get more excellent properties.Charge transfer effect has a very important influence in the hetero-nantructure,by controlling the component,morphology and size,more charge transfer channels can be obtained and the light induced electron hole pair can be separated efficiently.Moreover,when the size of metel decreases to quantum size,charge transfer plays a decisive role in the controlling of quantum plasmon.This paper focous on the charge transfer process in the complex meteal-semiconductor heteronanostrcture,by controlling the component,morphology and size of heteronanostrcture,we study the enhancement mechanism of photocatalytic activity by charge transfer and chage transfer controlling effect in the size dependences of LSPR.The main research contents are as follows:First,we report a method combining cation exchange and stepwise growth to grow Cd S-Cu_2-xS lateral heteroshells on Au nanoparticles.Ag₂S semi shells are initially grown on the Au nanoparticles as an interim layer,Cu_2-xS semi shells are then grown on the uncovered surface of the Au nanoparticles,and Cd S is generated by replacing Ag₂S and the Au core complex with Cd S-Cu_2-xS PN lateral heteroshells Au/Cd S-Cu_2-xS is finally obtained.These complexes integrate the plasmon resonances of Au in the visible region and that of Cu_2-xS in the near-infrared region,and all the components directly contact with each other,this structure can effectively separate electrons and holes,inhibit the carrier recombination,therefore show improved photocatalytic activity and high photothermal efficiency.This study offers a synthetic approach to grow metal sulfides on Au nanostructures which have diverse applications in photocatalysis and photothermal therapy.Next,we experimentally observe that the nonmonotonic blueshift of LSPRs with size for Au nanoparticles is turned into an approximately monotonic blueshift by increasing the electron donor concentration in the reduction solution,and it can also be transformed to an approximately monotonic redshift after surface passivation by ligand molecules.Moreover,we demonstrate controlled blueshift and redshift for the electron and hole plasmons in Cu_2-xS@Au core-shell nanoparticles by injecting electrons.In theory,we propose an improved semiclassical model for modifying the dielectric function of metal nanospheres by combining the intrinsic quantized electron transitions and surface electron injection or extraction to investigate the plasmon shift and LSPR size dependence of the charged Au nanoparticles.The experimental observations and the theoretical calculations clarify the controversial size dependences of LSPR reported in the literature,reveal the critical role of surface electron injection or extraction in the transformation between the different size dependences of LSPRs,and are helpful for understanding the nature of surface plasmons in the quantum size regime.Finally,we grow uniformly coated platinum selenide on the Au nanorods and more tightly bound platinum selenide was controlled grown on heads or the sides of the Au nanorod.Through studying the photocatalytic performance,Au nanorods with platinum selenide on one side have the strongest catalytic performance due to its larger contact surface with the Au nanorods and the useful transverse plasmon resonance peak in visible band.This study provides a new method for controllable anisotropic semiconductor growth on Au nanorods.