Preparation Of Metalnanowires And Their Applications For The Construction Of Electrochemical Biosensors

In recent years, nanomaterials as new material have been widely researched and used including the biosensing filed. With the introduction of nanaomaterials, the performance of biosensor has a greatly improvement. In the paper, we synthesized some one-dimensional material nanomaterials, taking advantage of the good physical, chemical, electrocatalytic and biocompatibility of these nanomaterials and applying them in the fabrication of biosensors. The modified electrodes can be used to determine hydrogen peroxide in low potential with high sensitivity, ideal for the construction of biosensing platform. Immobilizing glucose oxidase onto the platform with different method, the resulting biosensors have high sensitivity, low detection limit and fast response time. The details are summarized as follows:1. Prepared nanowire using template method and successfully applied to modify the interface of the electrode and to fabricate the glucose biosensor.(1). Platinum nanowires (PtNW) were prepared by an electrodeposition strategy using nanopore alumina template. The nanowires prepared were dispersed in chitosan (CHIT) solution and stably immobilized onto the surface of glassy carbon electrode (GCE). The electrochemical behavior of PtNW modified electrode and its application to the electrocatalytic reduction of hydrogen peroxide (H2O2) is investigated. The modified electrode allows low potential detection of hydrogen peroxide with high sensitivity and fast response time. As an application example, the glucose oxidase was immobilized onto the surface of PtNW modified electrode through cross-linking by glutaric diadehyde. The detection of glucose was performed in phosphate buffer at -0.2V. The resulting glucose biosensor exhibited a short response time (<8 s), with a linear range of 10-5-10-2 M and detection limit of 5×10-6 M (in chapter 2).(2). In previous study, we immobilized glucose oxidase onto the surface of electrode using the cross-linking with glutaraldehyde, and it can lead to denature of enzyme. The performance of biosensor needed to be improved.In next chapter, we prepared gold nanowires by electrodeposition strategy in polycarbonate (PC) membrane with the average diameter of the nanowires about 250 nm and length about 10μm. Next, we fabricated enzyme functionalized gold nanowire materials using the good biocompatibility of metal gold toward biomolecules and directly immobilized on glassy carbon electrode surface. The nanowires prepared were dispersed into chitosan (CHIT) solution and stably immobilized onto glassy carbon electrode (GCE) surface. The electrochemical behavior of gold nanowire modified electrode and its application to the electrocatalytic reduction of hydrogen peroxide (H2O2) were investigated. The modified electrode allows low potential detection of hydrogen peroxide with high sensitivity and fast response time. Moreover, the good biocompatibility of nanometer-sized gold, the vast surface area of the nanowire-structure make it ideal for adsorption of enzymes for the fabrication of biosensors. Glucose oxidase was adsorbed onto the nanowire surface to fabricate glucose biosensor as an application example. The detection of glucose was performed in phosphate buffer (pH 6.98) at -0.2V. The resulting glucose biosensor exhibited sensitive response, with a short response time (<8 s), a linear range of 10-5-2×10-2 M and detection limit of 5×10-6 M (in chapter 3).2. Preparation of nanowire array modified electrode. Synthesized nanowires using template method and fabricated uniform and orderly nanowire modified film through careful immobilization on electrode surface. The orderly nanowire modified film provided the large surface area and the lower determine limit.(1). Platinum nanowire array was prepared using similar method in polycarbonate membrane and the electrocatalytic activity of the platinum nanowire array toward hydrogen peroxide was investigated. The nanowire array can direct response to hydrogen peroxide at low potential of 0 V with high sensitivity and wide linear range. While the nanowire array can improve the signal-to-noise ratio and reduce the detection limit, the high surface area of the nanowire array increased the amount of electroactive sites and increased the upper detection limit. With the absorption of glucose oxidase onto the ordered nanowire array, the spatially patterned glucose oxidase improves greatly the performance of resulting biosensor. The biosensor can achieve interference free determination of glucose with wide linear range(5×10-6-2×10-3 M) and low detection limit of 1μM. (in chapter 4).(2). Gold nanoparticles modified nickel nanowire array has been prepared using electrodeposition and self-assembly technique and used for the fabrication of glucose biosensors. First, polycarbonate membrane was immobilized onto glassy carbon electrode surface for the preparation of nickel nanowire array, and then the nanowire array was immersed into histidine and gold nanoparticle solution. Gold nanoparticles can be adsorbed onto nanowire surface through self-assembly process. The gold nanoparticle modified nickel nanowire array can direct response to hydrogen peroxide at low potential of 0 V with high sensitivity, indicating excellent electrocatalytic activity of the modified electrode. With the immobilization of glucose oxidase onto the electrode surface through gold nanoparticles, a new glucose biosensor has been constructed. Interference free determination of glucose has been realized with a linear range from 10-5 to 10-2 M and the detection limit was 5μM glucose (S/N=3) The bioactivity of the enzymes can be well protected due to favorable microenvironment provided by histidine and gold nanoparticle and the biosensor has good stability (in chapter 5).