Synthesis Of Silver Nanosheet-assembled Micro/nanostructure As SERS Substrate For Detection Of Organic Pollutant

In recent years, the deteriorating enviromental problems have attracted much attention. Among them,the residual organic pollutants in water, such as pesticides, dyes and persistent pollutants, have threatenedecologial enviroment and human health seriously. These organic pollutants could accumulate in humanbody, which not only cause chronic toxicity （such as carcinogenic, teratogenic, mutagenic and so on）, butalso lead to endocrine disorders and reproductive and immunologic derangement. Therefore, the rapiddetection of these organic pollutants is extremely urgent at present. Surface enhanced Raman Spectrary（SERS） effect of noble metal nanostructures, with the great advantages of extremely high sensitivity andindentification of analytes, has been intensely focused in the field of organic pollutant analysis andrecongnized as a powerful and prospective tool in evrionmental analysis. In this dissertation, silvernanosheets assembled nanocubes and film as SERS substrates has been designed and synthesized, whichthen were studied systematically by usig R6G molecules as analyte. The main research results could beseen as follows:1. Based on the influence of citrate ions on the Ag nanosheets, nanosheet assembled Ag hollow cubeshave been fabricated by using Cu₂O microcubes as chemical template. In the reaction system, the Ag⁺ionswere reduced by Cu⁺ions released from Cu2O cubes in the presence of acid. It was found that theconcentrations of acid, citrate ions and AgNO3were critical to the formation of perfectnanosheet-assembled hollow microcubes. The relationship between the morphology structure and SERSperformence was studied through using rhodamine6G （R6G） as probing molecules and Ag hollow cubes asSERS substrats. The SERS experiments showed that the pack density and porous structure of the shell inthe final products strongly affected the SERS signals. The product with higher porous shell structureexhibited stronger SERS signals than others and the detection limit could reach to10^-14M for R6Gmolecular, indicating the rough Ag hollow microcubes could act as excellent substrates for ultrasensitivedetection.2. On the basis of the above research, the designed Ag hollow microcubes were used to detect organicpollutants in water successfully. However, it was time-consuming to separate from water. Thus based onthe above research, Cu₂O film was intentionally introduced as a buffer layer on Cu plate through in-situ redox reaction, which decreased the reactivity of Cu plate, and then silver nanosheet-assembled film wasobtained through using Cu₂O film as a chemical template reacted with AgNO₃. According to the previouswork, the morphology like pack density of the nanosheets could also be simply adjusted by changing theconcentration of Ag+ions. Surface enhanced Raman scattering （SERS） experiments using Rhodamine6G（R6G） as probing molecules shows that these rougher Ag film have high performance and goodreprodubility, and the detection limite could reach to10^-12M by using the convenient droplet method. Thusthese rougher Ag film could act as excellent substrate for ultrasensitive detecting.