| Recently, surface enhanced Raman scattering (SERS) was universally applied in the areas of single molecules detection, biological analysis and so on. However, construction of stable and uniform substrates is still a problem in SERS measurements. Therefore, in this paper, we focus on the construction of new. stable and uniform graphene oxide (GO)/gold or silver nanoparticles assemblies through the in situ and self-assembly methods. The synthesized graphene/gold or silver nanoparticles assemblies can be used as SERS substrates, and has been successfully applied in malachite green (MG). anti-cancer drug of6-mercaptopurine (6MP) and Ag+detection. Moreover, we further study the enhancement mechanism of SERS of GO/gold or silver nanoparticles assemblies. The main contents are as follows:(1) By introduce the tyrosine as an environmental friendly and biocompatible reducing agents, GO/AuNPs hybrids were fabricated through a green in situ procedure. This new type of hybrids can be used as highly efficient SERS substrates for dye of MG detection. It was found that no dispersed gold nanoparticles can be synthesized without GO. which is attributed to the nucleation function of the groups on GO sheets. Using GO/AuNPs as SERS substrates and Rhodamine6G (R6G) as Raman reporter, enhancement factor (EF) was measured as about103. Taking advantage of the high affinity of GO and AuNPs with MG, a sensitive, selective and label-free MG detection method was demonstrated. The SERS results showed that the linear response ranged from2.5to100μmol L-1. This method can be applied to detect MG in fishery water with satisfactory results.(2) The assembly of GO and metal nanoparticles (MNPs) was prepared effectively through the mediation of polyethylenimine (PEI) molecules. By using the hybrids as SERS substrates, label free determination of6MP was performed. PEI is a cationic polymers that could effectively attach on the surface of GO to change the charge of GO for further negative MNPs adsorption. PEI is commercial available without further chemical modification, which can assemble with GO and MNPs directly. By the process, AuNPs and AgNPs were assembled on GO successfully. Moreover, it also applied to assemble CNTs with MNPs, indicating this assembly method is general. Utilizing GO/AgNPs as SERS substrates for MBA measurements, EF was calculated as105,and it is high enough for utrasensive detection. Lastly, we constructed a label free, sensitive and selective method for6MP detection in pharmaceutical tablets.(3) Taking advantage of mercaptobenzoic acid (pMBA) as ligand, GO and gold nanowires hybrids was sythesised and used as SERS substrate for Ag+detection sccesfully. pMBA is a strong binding ligand that can connect on AuNPs through Au-S chemical bands rapidly. According to the mechanism, we introduce pMBA molecules to GO/PEI/AuNPs solution to grow AuNWs between GO and AuNPs in the presence of chlorauric acid and L-ascorbic acid. We report a new type of AuNWs growth occurred on the GO surface. The new formed Au continuously deposited at the GO-Au interface due to the little amount of pMBA bind there. AuNWs were formed. The prepared GO/AuNWs are good SERS tags because lots of pMBA attached on their surface, which is a normal Raman reporter. Ag+reduced to AgNPs on the AuNWs will further enhance the signal of pMBA, which can be used for Ag+detection. |
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