Preparation And Analytical Application Of Biosensor Based On Graphene Nanocomposite Film

Organic molecules such as amino acid, protein, nucleotide and others required in the process of metabolism, have been proven to play crucial roles throughout the body. The abnormal level of these molecules can not only affects the body’s normal operation, but also correlates with many diseases. Therefore, designing simple and fast methods for the detection of organic molecules is necessary. Building chemical modified electrodes and applying to the determination of concentration in real samples is of great significance. Based on the above, we developed biosensors for the determination of calcium folinate (CF) and L-cysteine (L-CySH). The works were as follows:1. The bare copper electrode was firstly anodic polarized in NaOH solution, then the carboxyl graphene (CG) was electrodeposited on the CuXo/Cu electrode by cyclic potential sweeping, thus the carboxyl graphene modified CuxO/Cu electrode was fabricated for the determination of CF. XPS and Raman indicated the formation of CuxO nanoparticles and CG. The CuxO nanoparticles was of high electrocatalytic activity towards CF oxidation in alkaline solutions, and the electrodeposited of CG can ensure the stability and repeatability. The electrocatalytic oxidation behaviors of CF at the graphene modified CuxO/Cu electrode were investigated by cyclic voltammetry. A new method, the positive scan polarization reverse catalytic voltammetry (PSPRCV) was used to obtain the pure catalytic oxidation current and quantitaive detection. This method can reduce the background current and improve the sensitivity. A highly sensitivity of 22.0 μA·μM-1·cm-2 was achieved, and the current response was linear with increasing CF concentration in the range of 2.0×10-7 to 2.0×10-5M, which crossed three orders of magnitude, and the detection limit was found 7.6×10-8M (S/N=3). In addition, the proposed sensor was successfully applied in the determination of CF in drug sample.2. Potentiostatic was used for the electrodeposited of CuNPs on bare glass carbon electrode, then the carboxyl graphene (CG) was electrodeposited on the CuNPs/GCE electrode by cyclic potential sweeping and CuO was formed by CuNPs, then the CuO-CG/GCE modified electrode was fabricated for the determination of CF. The characterization results of SEM and XPS indicated the theoretical feasibility. The formation of CuO and CG changed the morphology, and increased the surface area. The electrocatalytic oxidation behaviors of CF at the CuO-CG/GCE electrode were investigated by cyclic voltammetry. And the positive scan polarization reverse catalytic voltammetry (PSPRCV) was used for the quantitaive detection. The sensor had better electrocatalysis than the graphene modified CuxO/Cu electrode. The current response was linear with increasing CF concentration in the range of 1.0×10-7 to 3.0×10-5M, and the detection limit was found 6.8×10-8M (S/N=3). In addition, the proposed sensor was successfully applied in determination of CF in drug sample.3. Potentiostatic was used for the anodic polarization of GCE in alkaline solution, AuNPs and carboxyl graphene (CG) was one step electrodeposited by CV on the polarized GCE and DPV was used for the determination of L-CySH. The anodic polarization of GCE can generate a lot of oxygen functional groups which had high electrocatalysis activity for L-CySH oxidation. The formation of AuNPs and CG composite film combined with the advantages of both of them. It can not only promote the electron-transfer processes, increase the surface area, but also prevent the irreversible agglomerates phenomenon of CG. Under the optimal experimental conditions, the calibration curve range from 5.0×10-6 to 5.0×10-7M, the detection limit was found 1.96×10-6M (S/N=3).