Fabrication Of Gold Nanorods-porphyrin Core-shell Structure And Study Of Its Photocatalytic Properties Under Visible Light Irradiation

Plasmonic materials have attracted much attention owing to their unique surface plasmon effect（SPR）by photoluminescence.As a typical anisotropic plasmonic material,gold nanorods（GNRs）have advantages of good biocompatibility,adjustable light response between 550-1550 nm and high chemical stability.In recent years,studies show gold nanorods can enhance the photocatalytic activity of semiconductor materials,but most of the inorganic semiconductors are used for photocatalysis which absorb spectrum lies in ultraviolet region.In order to improve the utilization of visible light,efficient photocatalysts with visible light responsive need to be designed and prepared.Porphyrin assembly is an organic semiconductor material with excellent photoelectric properties.Compared with traditional inorganic semiconductor materials such as TiO₂,the absorption spectrum of the porphyrin is located in the visible light region,which can make use of solar energy more effectively,but Pt must be added as co-catalyst.Therefore,the paper chooses gold nanorods and porphyrin assemblies to make a composite,in order to obtain more efficient solar energy utilization materials.This paper mainly focuses on the following two aspects:1.The gold nanorods-porphyrin core-shell structure had been synthesized via a surfactant-assisted self-assembly induced acid-base neutralization micelle encapsulation method.The fabrication of composite was achieved by adjusting the length diameter ratio of GNRs,the type and concentration of surfactants,and pH.By regulating the reaction parameters,the composite structure with regular morphology,uniform size and good monodispersibility was prepared by using CTAB/NaOL coated GNRs with a length diameter ratio greater than 4.Combined with TEM and the dynamic tracking experiment indicated the composite structure was the core-shell structure of porphyrin assemblies covering GNRs.The XRD was employed to analyse the crystal structure,and the result showed the GNRs-ZnTPyP core-shell structure had good lattice structure.2.The UV-vis absorption,PL intensity,the time-resolved fluoresces decay and the i-t test indicated that the GNRs-ZnTPyP had a good light absorption in the visible light region.The photocurrent test showed that the photocurrent density of GNRs-ZnTPyPcore-shell structure and ZnTPyP self-assemblies was about2.0μA/cm² and 0.8μA/cm² respectively,and the core-shell structure was 2.5 times as high as that of self-assemblies.Using ascorbic acid（AA）as electron donor,the visible light photocatalytic hydrogen production without Pt of different catalyst systems were carried out under pH≈5.0.Under the same condition,the GNRs-ZnTPyP core-shell structure had a H₂ production rate of 37 mmol/g/h,which was 15times of the physical mixing.At different wavelengths,the photocatalytic hydrogen production of GNRs-ZnTPyP core-shell structures indicated that ZnTPyP was the main electron donor,the local electric field produced by GNRs and its coupling with ZnTPyP could increase the number of electron-hole pairs and promote the separation and transmission.The hot electrons produced by GNRs can also activate porphyrins and enhance the catalytic properties.The synergistic enhancement of these effects made the core-shell structure have a superior photocatalytic hydrogen production.