| Graphene as a novel carbon material, with unique two-dimensional conjugating structure and outstanding optical electronic properties, has drawn world-wide attentions. Due to its special band-gap structure, huge specific surface area and stable chemical properties, graphene shows great potentials in the fields of energy materials, chemical sensing and environment management. To extend its applications, graphene has been functionalized to adjust its properties for the specific uses.The serious environment problem forces people to pursue a fast and convenient method for the on-site detection in emergent environmental accidents. Extraction-integrated surface enhanced Raman spectroscopy (SERS) detections have been developed to overcome this problem. Fast and sensitive detections of various pollutants have been accomplished via SPE-SERS and SPME-SERS. The very key to realize the integration of extraction and SERS is to find or prepare a functional material which has both the extraction ability and SERS activity. Functionalized graphene materials have been widely used in the fields of SPE, SPME and SERS sensing, which causes our great interests. Preparing a graphene material with enrichment and detection functions will benefit the extraction-integrated SERS detection methods. It will extend the applications of graphene materials in analysis chemistry and help the development of SERS based integrating detection techniques.In this dissertation, we focused on the preparation of functionalized graphene materials, and established a novel extraction-integrated SERS detection methods based on graphene materials. Finally, the non-destructive sampling and SPME-SERS detection were realized via functionalized graphene materials. The main content can be summarized as follows:1. Chemical reduction of graphene oxide (GO) is an important method to obtain graphene materials. Metal reductants have been developed to avoid the usage of hazardous reagents and attracted wide interests. Herein, copper powder and noble metal salt solution were used as inducing reagents to trigger the fast reduction of GO via Cu-Ag (or Au) galvanic displacement. Graphene/Ag (or Au) nanocomposite materials can be prepared via this reaction under room temperature. The characterization results show that the oxygen containing functional groups in GO have been removed during the reaction; at the same time; Ag (or Au) nanoparticles with diameters of 30-50 run have been deposited on graphene. Based on the experimental results, a GO mediated long range electron transfer process has been proposed to explain the reduction of GO. Graphene/Ag nanocomposite material obtained with this method shows good SERS activity, which can be used as a substrate to enhance the Raman signal of p-atp. The SERS detection of thiram was performed with this material. The SERS signals of thiram in its solution (1.0×10-6 g/mL) can be detected. This work could provide a fast and convenient synthesis strategy for the SERS-active graphene materials.2. The serious environment contamination nowadays forces people to pursue a fast detection technique integrated with sample preparing function, which will solve the problem of on-site detection in emergent environmental accidents. Based on the principle of galvanic displacement induced reduction of GO, we developed a novel extraction-integrated SERS detection technique, namely reaction induced extraction (RIE)-SERS detection method. This method can be accomplished with graphene/Au nanocomposite materials, while the extraction of analytes was induced by Cu-Au galvanic displacement reaction. The large specific area of GO resulted in the effective adsorption of analytes, meanwhile the good dispersive properties of GO was used to overcome the shortcomings of graphene. The RIE sediment shows good SERS activity, due to the deposition of Au nanoparticles on graphene. Direct SERS detection can be performed in the semi-micro quartz cuvette after RIE, which removed the desorption operation of traditional SPE and reduced the total analysis time consuming. The RIE-SERS detection of the dye pollutants in water such as methylene blue (MB) and crystal violet (CV) can be accomplished within 20 minutes, with the solution concentration of 1×10-8 M. RIE-SERS shows great potentials in the field of on-site fast detection due to its miniature device and simple operations. It will promote the applications of functionalized graphene materials in environmental analysis.3. Monitoring the chemical level in living system is crucial to the medical science and disease diagnosis. To obtain the accurate concentration of analytes in bio-tissues, a non-destructive sampling method is required. Solid phase microextraction (SPME), which combines the sampling and extraction functions, is a powerful tool for in-vivo detections. The development of SPME-SERS combines the advantages of sample preparation and spectroscopy detection, simplifying the analysis operation by removing desorption of analytes after extraction. The SPME device used in SPME-SERS must be SERS-active. Herein, we developed a layer-by-layer fabrication method to prepare graphene/Ag hybrid coatings on copper-silver alloy fibers. Graphene/Ag coating with good SERS activity and spatial uniformity was obtained by controlling the preparation cycles. The fibers were used in the non-destructive sampling and SPME-SERS detection of antibiotic molecules in the sulfadiazine containing mimic tissue samples, with the detection limit of 2.5×10-7 g/cm3. Control experiments and molecule dynamic (MD) simulation were both carried out to prove the interaction between graphene and sulfadiazine could increase the sensibility of SPME-SERS. A good linear relationship of the reference SERS peak (at 1150 cm-1) intensity versus the logarithm of the sample concentrations was obtained in range of 2.5×10-7 to1.25×10-4 g/cm3, indicating the quantitative ability of this method. This work could extend the application of functionalized graphene in the field of bio-analysis, and promote the development of SERS based integrated detection technique. |
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