| As an advanced analytical technique, biosensor has caught widespread attentions and is applied in the field of biomedicine, environmental protection, food safety, and industrial production. Because it has many advantages such as strong specificity, high sensitivity, rapid detection, and easy operation. In the process of biosensor building, effective modification of active interface has been considered as a central part. It not only affects the main performance of the biosensor, but also determines its scientific value of research and application. Therefore, this dissertation has deveolped several biosensing active interface based on different surface modification techniques and multiple biomaterials, such as dendritic copper nanomaterials, silver nanoparticles, carbon nanotubes, graphene, dopamine and so on. The performance of prepared biosensor which can be used to detemine nitrite, dissolved oxygen and halide ion has also been researched and discussed. In addition, with the development of biosensor technology, miniaturization preparation of biosensor has become the main trend of future development. The micromachining process, such as photolithography and metal sputtering, has been introduced to prepare flexible micro-sensing electrodes which can work in non-traditional detection environment in this dissertation. This is an useful attempt in order to develop micro-biosensor for in vivo detection. The main contents of this dissertation are summarized as follows:(1) A novel non-enzymatic sensor for nitrite was prepared by an effective and simple strategy. A glassy carbon electrode was modified with reduced graphene oxide (RGO) and copper nanodendrites (Cu-NDs) successively via two-step electrodeposition method. The fabricated sensor displayed efficient electrocatalytic reduction of nitrite. In order to obtain the maximal sensitivity of detection, the effects of several experimental conditions on the current responses of sensor to nitrite were optimized, such as electrodeposition circles, Cu2+concentration, pH value, and detection potential. In the optimal situation, the sensitivity and the low detection limit of this non-enzymatic nitrite sensor were214μA mM-1cm-2and0.4μM (S/N=3) respectively. The wide linear range of the sensor was1.25×10-3～13mM. The sensor also showed excellent reproducibility, stability, and selectivity. These superior performances were attributed to the enlarged electro-active surface of nanomaterials and the synergistic effect of RGO and Cu-NDs.(2) A highly sensitive electrochemical sensor for dissolved oxygen was fabricated. Silver nanodendrites were successfully deposited on glassy carbon electrode (GCE) via a simple electrodeposition method. The electrode showed an excellent electrocatalytic activity for dissolved oxygen reduction to form hydroxy ions via a four-electron reduction pathway. And the respective overvoltage of sensor had a significant decrease at the same time. The sensor responded linearly to dissolved oxygen in the1.0～66.71μM concentration range, and had a high sensitivity (0.169μA μM-1) at an applied potential of-300mV vs. Ag/AgCl. The response time was less than5s, and the lower detection limit was0.043μM (at the signal-to-noise ratio of3). The superior response of the sensor was mainly attributed to the enlarged surface of the dendritic silver nanostructures with more electroactive sites and to the efficiency of electron transfer between the electrode and dissolved oxygen.(3) The amperometric non-enzymatic halide biosensor based on MWCNTs/Poly(dopamine)(PDA)/Silver nanoparticles (AgNPs) nanocomposite film was prepared. PDA was utilized here as a multifunctional intermediate for improving the dispersibility of hydrophobic MWCNTs, and reducing Ag+to Ag on the surface of MWCNTs. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) were employed to investigate the synthetic nanocomposite. The modified electrode exhibited remarkable electrocatalytic activity toward halide improved by the synergy effects of the intrinsic high surface area and the fast electron transfer rate of MWCNTs and AgNPs. Because of the well-separated oxidation potential, chloride, bromide and iodide could be simultaneously investigated by cyclic voltammetry in a mixture. The concentration range was linear from25μM～20.35mM for chloride,25μM～24.2mM for bromide and25μM～12.73mM for iodide. And the sensitivity was0.0205μAμM-1,0.0242μA μM-1and0.0182μA μM-1for chloride, bromide and iodide, respectively. (4) A flexible sensor based on SU-8photoresist was fabricated and its electrochemical performance was investigated using cyclic voltammetry. The device consisted of interdigitated array microelectrodes (IDAM) on an SU-8layer. It exhibited a clear electrochemical response during redox cycling of ferrocenemethanol at the IDAM. Since the device was flexible, it could be inserted into a narrow bent space to monitor electrochemical responses. |
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