| The results show that the assembly of the new multifunctional composite nanomaterials can make up for the deficiency and defects of single functional nano materials, and is widely used in many fields such as biomedicine, sensing and imaging. Gold nanoparticles (AuNPs)are widely used in the field of Surface-Enhanced Raman spectroscopy (SERS) due to its unique optical properties, modification easily,good stability and biocompatibility. In addition,graphene quantum dots (GQDs) excellent properties such as high photo luminescence activity,biocompatibility and low toxicity as a rational material for fluorescent probes. Based on the excellent properties of AuNPs and GQDs,composite nanomaterials AuNPs/Gn/GQDs with bi-functionalities of fluorescence and SERS were successfully assembled by simple self-assembly method with the glycine derivatives (Gn, n = 0, 3, 4, 5, 6 and 9) as the spacer.The effects of the size of AuNPs and the surface oxidation degree of GQDs on the fluorescence properties and SERS responses of AuNPs/G6/GQDs composite nanomaterials were further investigated. The main results are summarized as follows:(1) The tunable bi-functionalities of fluorescence and SERS signals were collected by the assembled AuNPs/Gn/GQDs composites. The composition and structure of the AuNPs/Gn/GQDs composites were characterized by Fourier-transform infrared (FT-IR)spectroscopy and high resolution transmission electron microscope (HRTEM). Results indicated that the fluorescence and SERS response could be tuned effectively by changing the chain length of Gn. Also, the AuNPs/Gn/GQDs composites could be used in a wide pH range and exhibited good stability at room and physiological temperatures. Moreover, the AuNPs/Gn/GQDs composites displayed low cytotoxicity in A549 cells, and the cell viability was found to be above 90% at concentrations ranging from 6.42 to 200 ?g/mL, which made AuNPs/Gn/GQDs composites very attractive for biological imaging applications in vivo.(2) AuNPs with five sizes were synthesized by simple seed growth method, and then various Aux/G6/GQDs composites were successfully assembled with G6 as spacer. The interaction among components, structure and morphology of Aux/G6/GQDs composites were characterized by UV-Vis spectroscopy, FT-IR and TEM. The results show that the different sizes of AuNPs can effectively tune the fluorescence and SERS responses of Aux/G6/GQDs composites by the surface energy transfer between AuNPs and GQDs. In addition,AuNPs/Gn/GQDs composites show good time stability and can be used in a much wider pH range, indicating that this composite with potential application in the biological imaging and detection.(3) Three kinds of GQDs with different surface oxidation degree were prepared by simple one-step hydrothermal synthesis method. Various AuNPs/G6/GQDsx (x= 1, 2 and 3)composites were assembled successfully with G6 as spacer. The interaction among components, structure and morphology of AuNPs/Gn/GQDs composites were characterized by UV-Vis spectroscopy, FT-IR and TEM. The effects of different surface oxidation degree of GQDs on the fluorescence properties and SERS response of AuNPs/G6/GQDs composites were studied. It was found that the surface oxidation degree of GQDs could tune the fluorescence performance and SERS response of AuNPs/G6/GQDs composites to a certain extent. In addition, AuNPs/G6/GQDsx composites showed good time stability. |
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