Surface-Enhanced Raman Scattering Of Metal-Zinc Oxide Nanorod Heterostructures

Surface enhanced Raman scattering(SERS)has very important applications in life sciences,disease diagnosis,medical treatment,food safety,environmental monitoring and other fields.In recent years,preparation of novel SERS substrates has been remarkably improved by the development of nanoscience and nanotechnology.The noble metals including Au,Ag and Cu have been confirmed to have excellent SERS properties based on their surface plasmon resonance effect,stimulating intense research enthusiasm on metal-based SERS substrates.Meanwhile,ZnO nanomaterial-based SERS substrates have also attracted extensive attention due to numerous advantages of ZnO nanomaterials,such as excellent SERS properties,photocatalytic properties and sensing properties,as well as low cost,variable and feasible sample preparation methods,and high morphology controllability,which could impact on applications,especially multi-functional applications,of the ZnO nanomaterial-based SERS substrate.Nowadays,fabrication and applications of heterostructured SERS substrates combining ZnO nanomaterials and noble metals have become considerably appealing.It is highly demanded to reveal the metal-ZnO synergistic effects on their SERS properties and to optimize the SERS performance and applications of the metal-ZnO heterostructured substrates.In this dissertation,SERS properties of pristine ZnO nanorods and ZnO nanorod-Au nanoparticles were studied based on precise morphology control of the samples.More importantly,two novel SERS substrates,Ag film-ZnO nanorods and Ag film-ZnO nanorod-Au nanoparticles,were fabricated by employing highly reflective Ag films.SERS properties of these two novel SERS substrates were then investigated in-depth;and the related mechanisms were discussed accordingly.The main contents of this thesis are summarized as follows:(1)Arrays of ZnO nanorods with different diameters were produced in a controllable manner.Surface decoration of these nanorods by Au nanoparticles was then applied.SERS properties of the resulted ZnO nanorod substrate and ZnO nanorod-Au nanoparticle substrate were studied extensively.By detecting R6 G and methylene blue molecules,effects of different excitation light wavelengths,substrate morphologies and structures on the SERS properties were investigated;(2)Novel SERS substrate of Ag film-ZnO nanorods were prepared.It was revealed that the Ag film-ZnO nanorod substrate is three times the SERS performance of the ZnO nanorod substrate.The underlying mechanisms of the Ag film-induced SERS enhancement are discussed accordingly;(3)Well-controlled Ag film-ZnO nanorod-Au nanoparticle samples were produced as novel SERS substrates.The SERS properties were studied systematically.A detection limit for R6 G of 10-16 M was achieved,much higher than the reported results in the literatures.In addition,SERS detection of gram-negative bacterium Escherichia coli was performed to confirm the promising application potential of the Ag film-ZnO nanorod-Au nanoparticle substrate.