Sensor Based On Nanomaterials/Polymer Film Material For Simultaneous Detection Of Small Biomolecules

Small bimoleculars play a very significant role in human metabolism, and is closely related to human health. Therefore. simultaneous detection of small bimoleculars is of critical importance not only in the field of biomedical chemistry and neurochemistry but also in diagnostic applications. Due to possessing low cost, high selectivity, simple operation, good sensitivity and stability, electrochemical sensors are considered as hot topic in Anal. Chem and have been widely used in clinical diagnostics, environmental monitoring and food industry. However, small biomolecules can not be recognized simultaneously at bare glassy carbon electrode owing to the fact that the oxidation potentials of these biomolecules are too close to be determined separately at bare glassy carbon electrode, thus resulting in poor selectivity. The construction of sensing interface is particularly important to achieve respective or simultaneous detection of small biomolecules. For the rapid, sensitive and accurate detection of biological small molecules. surface microstructure must be introduced on the bare electrode. This dissertation is devoted to the construction of sensing interface for simultaneous detection of small biomolecules using nanomaterials or polymer film material. The main work is described as follows:1. Graphene-multiwall carbon nanotubes-gold nanoclusters composites modified electrode for the simultaneous determination of ascorbic acid, dopamine and uric acidIn this work, graphene-multiwall carbon nanotube-gold nanoclusters (rGO-MWCNTs-AuNCs) composites were synthesized and used as modifier to fabricate a sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA). MWCNTs not only can accelerate the oxidation of AA, DA and UA because of the edge of plane graphite and/or defects but also can effectively inhibit the stacking of individual rGO and enhance the utilization of rGO based composites. AuNCs with excellent electronic conductivity can increase the effective surface area of the modified electrode, thus, enhancing the catalytic activity of MWCNTs-rGO/GCE. Based on the synergic effect of MWCNTs, rGO and AuNCs. the modified electrode displayed excellent catalytic activity and selectivity toward the oxidation of AA, DA and UA.The linear response range for simultaneous detection of AA, DA and UA at the sensor were 120-1701 μmol·L-1,2-213 μmol·L-1 and 0.7-88.3 μmol·L-1, respectively. Correspondingly, the detection limits were 40 μmol·L-1,0.67 μmol·L-1 and 0.23 μmol·L-1 (S/N=3). The proposed method offers a promise for simple, rapid, selective and cost-effective analysis of small biomolecules.2. Overoxidized polyimidazole/graphene oxide copolymer modified electrode for the simultaneous determination of ascorbic acid, dopamine, uric acid, guanine and adenineIn the present work, the PIm-GO composite film was fabricated on the electrode surface by cyclic voltammetry (CV) scanning, then transferred into 0.10 μmol·L-1 PBS (pH 3.0) for electrochemical oxidation at+1.8 V to achieve PImox-GO/GCE.The sensor was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), guanine (G) and adenine (A). The copolymer was characterized by the scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Due to the synergistic effects between PImox and GO, the proposed electrode exhibited excellent electrochemical catalytic activities and high selectivity and sensitivity toward the oxidation of A A, DA, UA, G and A. The peak separations between AA and DA, AA and UA, UA and G, G and A were 140 mV,200 mV,380 mV and 300 mV, respectively. The linear response ranges for AA, DA, UA, G and A were 75-2275 μmol·L-1,12-278 μmol·L-1,3.6-249.6 μmol·L-1,3.3-103.3 μmol·L-1 and 9.6-215 μmol·L-1, respectively, and corresponding detection limits were 18 μmol·L-1,0.63 μmol·L-1,0.59 μmol·L-1,0.48 μmol·L-1 and 1.28 μmol·L-1.3. Electrochemical sensor based on overoxidized dopamine polymer and 3,4,9,10-perylenetetracarboxylic acid for simultaneous determination of ascorbic acid, dopamine, uric acid, xanthine and hypoxanthineA novel electrode based on 3,4,9,10-perylenetetracarboxylic acid (PTCA) and overoxidized dopamine polymer (PDAox) was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), xanthine (XN) and hypoxanthine (HXN). The developed sensors exhibited an excellent catalytic activity, high sensitivity and good selectivity toward the oxidation of AA, DA, UA, XN and HXN. Scanning electron microscopy (SEM), cyclic voltammetry (CV), different pulse voltammetry (DPV) and electrochemical impedance spectroscopy (E1S) were employed to characterize the sensor. The peak separations between AA-DA, DA-UA, UA-XN and XN-HXN were large up to 0.15,0.18,0.37 and 0.40 V, respectively. The calibration curves for AA. DA, UA, XN and HXN were obtained in the ranges of 76-3900 μmol·L-1 ,0.60-253 μmol·L-1, 1.8-238 μmol·L-1,5.1-289 μmol·L-1 and 3.8-293 μmol·L-1 with detection limits (S/N=3) of 25.3 μmol·L-1,0.20 μmol·L-1,0.60 μmol·L-1,1.7 μmol·L-1 and 1.3 μmol·L-1, respectively. The integration of PDAox and PTCA in sensor opens up a facile and promising way for the simultaneous determination of above five substances.