Electroanalysis Studies Based On Several Thiol-modified Graphene Composites

Graphene is a two-dimensional honeycomb lattice packed by monolayer carbon atoms. It has attracted tremendous interest due to its large surface area, thermal and mechanical properties, high electrical conductivity and capability of chemical modification. The graphene-involved reseaches in the fields of electrochemistry and biosensors have thus become very active in recent years. The family of graphene composites can be expanded by thiolation reactions to endow graphene composites with additional coordination and electrostatic affinity functions for their enhanced application performance in electrochemistry and biosensing. However, the thiolation of graphene has been seldom studied to date.In this thesis, the recent progress of relevant research areas is briefly reviewed and several thiol-modified graphene composites were prepared for electroanalysis and biosensing applications. The main contents are as follows.1. A thiolated polymer-graphene nanocomposite film was prepared by cast-coating of graphene oxide (GO) on a glassy carbon electrode (GCE), reduction of GO by cyclic voltammetry to electrodeposit electroreduced graphene oxide (ERGO), electrosynthesis of polypyrrole (PPy), optically and electrochemically induced thiolation of PPy with meso-2,3-dimercaptosuccinic acid (DMSA). and then overoxidation of PPy (OPPy), Quartz crystal microbalance (QCM) was used to monitor the processes of electrode modification and intermolecular interactions. The application performance for electroanalysis of dopamine (DA) on the DMSA-OPPy/ERGO/GCE was examined. Under optimum conditions, the electrode responded linearly to DA concentration from5to2000nM with a limit of detection (LOD) of5nM (S/N=3).2. A DMSA-doxorubicin (DXR)/ERGO/GCE was fabricated by cast-coating of GO on a GCE, reduction of GO by cyclic voltammetry to electrodeposit ERGO, adsorption of DXR through π-π interaction, and then electrochemically induced thiolation of DXR with DMSA. Sensitive amperometric analysis of chicory acid was achieved on the DMSA-DXR/ERGO/GCE, giving a linear detection range of5-1500nM with a LOD of2nM (S/N=3) under optimum conditions.3. A DMSA-OPPy/ERGO/GCE was fabricated by electrodeposition of a PPy film on ERGO/GCE, thiolation of electro-oxidized PPy with DMSA, and then overoxidation of PPy. QCM was used to monitor the thiolation process. The DMSA-OPPy/ERGO/GCE after modification of Nafion and Bi films was used for sensitive electroanalysis of Cd2+and Pb2+by square wave anodic stripping voltammetry. Under optimal conditions, the linear detection ranges were from0.5to50μg L-1for both Cd2+and Pb2+, with LODs (S/N=3) of0.1μg L-1for Cd2+and0.05μg L-1for Pb2+, respectively. The sensor was applied to the simultaneous detection of Cd2+and Pb2+in water samples with satisfactory results.