Fabrication Nano-structrued Silver Surface-enhanced Raman Substrates And Application To Trace Polychlorinated Biphenyls Detection

Persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) areterribly harmful to human beings, and surface-enhanced Raman scattering (SERS) is apotential method to detect those pollutants rapidly and sensitively. The mostfundamental technique of SERS method is fabricating sensitive SERS substrates. In thisdissertation, we fabricated several kinds of sensitive silver nano-structured SERSsubstrates via glancing angle deposition (GLAD) method under liquid nitrogen coolingcondition, and detected polychlorinated biphenyls and recognized isomers ofmonochlorobiphenyls at trace levels using these SERS substrates.Firstly, a single model which is called hemisphere growth model was built to studythe rule of glancing angle deposition, and liquid nitrogen cooling was added into GLADprocess. Cooling by liquid nitrogen, more materials such as some low melting pointmaterials can be used in GLAD, and more complex morphology can be prepared byGLAD. We improved the tilted silver nanorod arrays, and fabricated columnar, helicaland zigzag silver nanostructures via liquid nitrogen cooling GLAD.Secondly, highly separated silver nanorod arrays fabricated by GLAD method withappropriate length and porosity was proved to be extremely SERS sensitive by usingRhodamine6G (R6G) as measuring molecules, and10-14mol/L Rhodamine6Gsolutions were detected via silver nanorods based SERS substrates.Thirdly, we built a PCBs Raman spectra database using both experimentalmeasuring and density functional theory (DFT) simulation results. The characteristicpeaks of PCBs and the vibrational modes corresponding to these characteristic peakswere confirmed by measurement and DFT simulation, and used to support PCBsdetection.Fourthly, trace amount of pentachlorinated biphenyls were detected and isomers ofmonochlorobiphenyls at trace levels were recognized via silver nanorods based SERSsubstrates. To apply SERS method to nonaqueous system, we used acetone as solvent toprepare PCBs solutions at trace level, and blew acetone away by soft nitrogen fluxbefore SERS detection. In addition,10-6mol/L PCBs in practical earth samples weredetected by silver nanorods based SERS substrates, which indicates SERS method canbe applied to detect POPs practically. Finally, we fabricated helical and zigzag silver nanostructures to further improvethe sensibility of silver nanorods based SERS substrates. We have proved that theincreasing of "hot spots" amount in silver nanostructures brings the increasing of SERSsensibility; and the increasing of underlay reflectance can also make the silver SERSsubstrates deposited on them more sensitive.