Construction And Application Of Novel Raman Detection System Based On Gold Graphitic Nanocapsules

Metal-graphene nanocomposites combine the electromagnetic enhancement effect of precious metals with the molecular enrichment and fluorescence quenching performance of graphene,thus making it has been widely used in Raman detection and imaging analysis.Actual samples are mixtures dispersed in various phases,both aqueous and organic,making accurate and sensitive detection of specific analytes challenging.Because SERS possesses single-molecule sensitivity,narrow peak widths and abundant molecular fingerprint information,make SERS a suitable technique for sensitive multiplexed detection in complex systems.Compared to a fixed nanoarray substrate,the SERS platform at the liquid-liquid interface has a major advantage.For example,the substrate at the interface can contact and then adsorb analytes from two phases,thereby realizing simultaneous analysis of multiple analytes in two phases.However,the uniformity of the SERS substrate,the distribution of target molecules and various factors in the microenvironment will fluctuate the SERS signal thus affect the accuracy of quantitative analysis.Although,the internal standard(IS)method has been proposed to solve this issue,there are still many problems,such as instability of IS molecules,competitive adsorption of IS molecules and analytes.In view of the above problems,we designed and synthesized a gold graphitic nanocomposite,and then self-assembled it at the immiscible liquid-liquid interface to form a interfacial SERS substrate for simultaneous enrichment and detection of two-phase multianalytes.Moreover,the interfacial SERS substrate is utilized for mimicking the drug molecules analysis in the blood samples.The details are as follows:(1)In Chapter 2,the preparation and characterization of graphene-isolated-Au nanocrystal(GIAN)were studied.At the same time,the stability,the enrichment performance and Raman enhancement effect of GIAN were investigated.The GIAN prepared by chemical vapor deposition(CVD)has a core-shell structure.The gold core provide signal enhancement for SERS analysis,the graphene shell ensures the stability of the material and enables GIAN to have a good molecular enrichment ability which further improving the sensitivity of SERS analysis.(2)In Chapter 3,based on the wettability of the GIAN's graphene shell,we assembled the GIAN at the immiscible liquid-liquid interface to form the interfacial SERS substrate.The graphite shells of GIAN enrich BPEA and CV from two phases through ?-? interactions,thereby enabling simultaneous SERS detection for two-phase analytes.Quantitative analysis of two-phase analytes showed that using 2D peaks of GIAN as IS can eliminate interference factors and improve the quantitative accuracy.In addition,the SERS analysis of two drug model analytes in serum and mouse blood was carried out by using the interfacial GIAN substrate,indicating that it has superior multiplex detection capability.(3)In Chapter 4,we fabricated a gold graphitic nanocomposite(Au@G)with smaller size by CVD.A mesoporous silica layer was coated on the synthesized AuNP core to avoid fusion of AuNP and infiltrate carbon source in CVD process,the size of the resulting Au@G is approximately 17 nm.The concentration of ethyl orthosilicate during the reaction was optimized,and Au@G was used as the SERS substrate to detect crystal violet,indicating that Au@G has a good enhancement effect and great potential in molecular detection and intracellular imaging analysis.