Construction And Application Of Electrochemical Biosensors Based On Nanocomposites

Biosensor technology, as a multidisciplinary research direction involved biology,physics, chemistryand electronics has broad application prospects in scientificresearch, environmental monitoring, industrial and agricultural production and clinicalmedicine fields. Especially, electrochemical biosensor occupies an important positionamong all kinds of biosensors. With the development of nanotechnology, theemerging of the new nano materials provides new opportunities for the developmentof electrochemical biosensor. Based on the unique properties such as size effect andsurface effect of nanomaterials, the biological sensing electrode can be effectivelyimproved, and thus greatly improve the detection performance of biosensors. Andmore is worth noting that the nanocomposite materials not only combine theadvantages of individual material alone, but also has a coordinating effect betweenmaterials, which can obtain a greater improvement on various aspects of performance.Based on the above, this paper will develop a variety of nanocomposite electrodemodification system, construct electrochemical biosensors based on enzymes, redoxprotein and nonenzyme. The biosensors have been applied in medical, environmental,food and other fields, which obtained different degrees of improvement in terms ofdetection performance.The main works are included as follows:1. Glucose biosensor based on GR-CdS nanocomposites modified electrodeGraphene-CdS (GR-CdS) nanocomposites were synthesized via a simple andnondestructive process. First, due to the noncovalent functionalization of pristinegraphene by1-aminopyrene, the intrinsic electronic and mechanical properties ofgraphene could be effectively protected. The CdS nanocrystals were then in situsynthesized on the amino-graphene. Based on the synergistic effect of GR-CdSnanocomposites, a sensitive glucose biosensor was fabricated by immobilizingglucose oxidase (GOD) in thin flm of chitosan containing GR-CdS nanocompositeson a glassy carbon (GC) electrode. The glucose biosensor exhibited a wide linearrange from0.5to7.5mM with a high sensitivity of45.4μA mM1cm2underoptimized conditions. This work could provide a simple and nondestructivefunctionalization approach to fabricate graphene-based hybrid nanomaterials forvarious applications.2. Hydrogen peroxide biosensor based on GR-ZnS nanocomposites modified electrodeA novel electrochemical platform based on ZnS-doped graphene (GR-ZnS)nanocomposites was developed. ZnS nanostructure, as a good substitute of CdS, wasdoped on the surface of graphene, and the GR-ZnS nanocomposites modifiedelectrode was applied in electrochemical analysis of hydrogen peroxide. UV-Vis andFT-IR spectroscopic results confirmed that Hb remained its native structure in thenanocomposite material. The modified electrode was then used for the determinationof H2O2based on the electrocatalytic activity of Hb towards H2O2, which exhibited alinear range from10to250μM with a detection limit of1.12μM.3. Electrochemical determination of kojic acid in foodstuffs based onGR-Pt nanocomposites modified electrodeA differential pulse voltammetric (DPV) method for the determination of kojicacid was developed. The electrode was modifed with composite nanomaterials of GRsheets and Pt nanoparticles. The electrochemical behaviour of kojic acid on theelectrode was studied, which indicated that the nanocomposites modifed electrodecould efficiently promote electrocatalytic oxidation of kojic acid based on thesynergistic effect of the excellent electrical conductivity and high catalytic activity ofGR and Pt. A rapid, sensitive and simple electrochemical method was then developedfor the determination of kojic acid using the constructed electrode. Under theoptimized conditions, the oxidation peak current exhibited a wide linear range fromtowards the concentration of kojic acid with a sensitivity of139.3μA mM1, and thelimit of detection was as low as0.2μM. The modifed electrode was also used forquantitative analysis of kojic acid in food samples, and the recoveries were between97.5%and101.3%, indicating the feasibility of the electrochemical method for kojicacid analysis in routine detection.4. Electrochemical determination of nitrite based on PANI–TiCnanocomposites modified electrodeA novel nanocomposite PANI–TiC prepared from polyaniline (PANI) andtitanium carbide (TiC) was synthesized through a chemical oxidative polymerizationmethod. FT-IR、SEM、TEM、XRD was used to characterize the morphologies andcompositions of the nanocomposite. Experimental results of cyclic voltammetryindicated that PANI–TiC could efficiently promote electrocatalytic oxidation of nitrite.Electrocatalysis for nitrite revealed good catalytic performance with a sensitivity of116.0μA mM1, and the limit of detection was as low as0.4μM. 5. Electrochemical determination of tryptophan based on WO3-ILnanocomposites modified electrodeWO3nanostructure was synthesized by hydrothermal method. Detected by SEM,TEM, XRD, UV-Vis for the morphology and structural characterization, the asprepared WO3nanostructure have been proved to have crystal structure with highpurity and crystallinity. WO3nanostructure was then composited with roomtemperature ionic liquids (BMIMBF4) to modify electrode to test the tryptophan.Studies have shown that WO3-ionic liquid composite materials can effectivelyenhance tryptophan in oxidation reaction on the surface of the electrode under thecondition of pH3.0with a detection sensitivity of1.11μA μM1cm-2，the detectionlimit of0.5μM.