Several None-enzymatic Electrochemical Sensors Based On Three-Dimensional Graphene

In recent years, zero-dimensional and one-dimensional(1D) nanomaterials have attracted a lot of attention for novel sensor developments. Graphene, a one-atom-thick two-dimensional(2D) carbon material, is composed of sp2 hybridized carbon atoms. Graphene has been hotspot mainly due to its admirable thermal conductivities and large specific surface area. Particularly, graphene and graphene-based composites have been widely used as promising electrode materials in electrochemical devices, such as supercapacitors, rechargeable lithium-ion batteries, lithium–O2 batteries, fuel cells, and electrochemical sensors. Except 2D graphene, sheets of three-dimensional(3D) graphene have been synthesized via CVD on nickel films using large scale and high quality graphene. At the same time, this 3D graphene material has perfect replication throughout nickel foam pore structure. Compared with traditional two-dimensional plane electrode, 3D Graphene also exhibits larger surface area, fast mass transfer ability and lower charge transfer resistance. Therefore, this kind of 3D graphene electrode shows an increase advantage in the development of new type electrochemical sensor with high sensitivity.The dissertation focused on the fabrication of two kinds of none-enzymatic sensors based on 3D graphene which used to detect glucose and hydrogen peroxide. The detailed steps were summarized as follows:1. Based on three-dimensional graphene(3D-G) electrode, a non-enzyme sensor was established for monitoring glucose. Specifically as follows: Based on three-dimensional graphene(3D-G) electrode, Prussian blue(PB) acted as electrochemical indicator which co-deposit with gold nanoparticles(Au NPs) to form Au–PB nanocomposite. To further improve the performance of the sensor, a second Au NPs layer was assembled onto the Au–PB nanocomposite surface via reduction of polydopamine. Then the in situ synthesised Au NPs afford binding sites for 4-mercaptophenylboronic acid(MPBA) self-assembly via Au–S interaction. MPBA reacted with the 1,2-diol of glucose to form a stable five-membered ring structure and the substrate was monitored by the current signal change of PB. The signal changes are linear with the glucose concentration in a certain range which can realize monitoring glucose. The fabricated sensor exhibited excellent performance such as good sensitivity, high selectivity, and wide linear range from 5.0x10-6 mol/L to 65.0x10-6 mol/L, also a low detection limit of 1.5x10-6 mol/L towards glucose.2. A novel three-dimensional(3D) electrochemical none-enzymatic sensor based on 3D-G electrode was developed for detection of hydrogen peroxide(H2O2). Specifically as follows: Using electrodepositing HAuCl4 solution to form gold nanoparticles(Au NPs) linker, and the 3D electrode was functionalized with thionine molecules which can efficiently reduce H2O2 at the electrode surface. Scanning electron microscopy(SEM) and electrochemical assays were used to investigate the preparation process and the detection mechanism. Th as electrochemical active component can be directly electro-catalyze the reduction of hydrogen peroxide. The peroxide hydrogen was educed to water and Th itself was oxidized into oxidation state. Then the oxidation state of Th get electronics from electrode. Therefore Th modified 3D-G electrochemical sensor can be directly used to detect hydrogen peroxide. Such excellent non-enzymatic sensor is able to detect H2O2 with a wide linear range from 0.2x10-6 mol/L to 1.1x10-3 mol/L, high sensitivity of227.8x10-6 A /(mmol/L cm2) and low detection limit of 58x10-9 mol/L.