Study On Nanomaterials Based Electrochemical Sensors And Their Applications In Hydrazine Detection

Hydrazine is a kind of colorless fuming, corrosive, strong reducing and colorless oily liquid, and it is widely used in industrial, agricultural and aerospace fields. However, hydrazine is a hazardous substance. Exposure of it may lead to damage of the kidneys and central nervous system. Therefore, it is necessary to detect the hydrazine precisely and quickly. Among different approaches, the electrochemical detection method shows unique advantages of high sensitivity, fast response and simple to use. So, the electrochemical method has been received more and more attention and research. In order to improve the sensing performance of electrochemical detection method, the nanomaterials began to use for fabricating hydrazine electrochemical sensors. Nevertheless, problems such as, low sensitivity, high electrocatalytic potential and poor overall performances are still existd in hydrazine electrochemical sensors. Thus, studying the electrocatalytic properties of different nanomaterials, utilizing the morphology control, the optimization of modification and the noble metal doping to improve the performance of sensor is very important.The dissertation is aiming at a comprehensive study on ZnO nanomaterial, Cu/Cu₂O@carbon nanocomposite and noble metal（Au） modified rGO-CNTs composite film, and testing their electrocatalytic properties toward hydrazine. In the first, the mechanism of electrodeposition ZnO nanomaterials were explored, controllable preparation of ZnO nanomaterials by electrodeposition was achieved, and to determine the effects of Zn O morphology on hydrazine sensing. Then, mass preparation of Cu/Cu₂O@carbon and the effects of its modified quantity on hydrazine detection were studied. Finally, Au nanoparticles modified rGO-CNTs nanocomposite was synthesized, and on the basis we prepared Au modified graphene and graphene-CNTs micron fibers. And high sensitive measurement of hydrazine was achieved using them. The main conclusions of this dissertation are as followings:（1） Various parameters（such as, additive, potential, concentration of Zn2+, temperature and seed layer and so on） of electrochemical deposition ZnO were studied, and controllable preparation of ZnO nanomaterial was achieved. Three kind of ZnO nanorod structurals which possess different specific surface area were synthesized by electrodeposition. The expemental results show that the fabricated ZnO nanosturctures exhibited electrocatalytic properties toward hydrazine. Especially, the ZnO-3 with a multi-branch structure showed the best detection performance because of its biggest specific surface area. The sensitivity of the hydrazine electrochemical sensor which fabricated by ZnO-3 can reaches to 5.35 μA·μM-1·cm-2 in 0.8-101 μM with a detection limit of 0.08 μM, and exhibites good long-term stability and repeatability.（2） We have successfully synthesized Cu/Cu₂O@carbon nanocomposite by using the method of calcination in inert gas condition. The results indicate that the Cu/Cu2 O nanoparticles with a diameter of 60-100 nm are wrapped by carbon black, and exhibit excellent stability in various pH conditions（pH=4.0-9.0）. In addition, the fabricated Cu/Cu₂O@carbon can be uniformly dispersed in polar and non-polar solvent, which is due to that the functional groups of plant fibers are retained in preparation process. According to the electrochemical experiments, we can find that the fabricated Cu/Cu₂O@carbon nanocomposites exhibit a better electrocatalytic property towards hydrazine, and the modified quantity will affect the detection performance. The optimum modification is 510 μg/cm2 in our current conditions. The optimized hydrazine sensor possesses a linear range of 0.25-800 μM and a detection limit of 0.022 μM.（3） Based on the high specific surface area, high conductivity and excellent chemical stability of graphene and carbon nanotubes, we prepared rGO-CNTs nanocomposite material and test its electrocatalytic property for hydrazine. The results indicate that the rGO-CNTs can electrocatalytic oxidation of hydrazine, and the best catalytic effect could be obtained with the weight ratio of 2:1（CNTs: rGO）. In order to improve the electrocatalytic performance of rGO-CNTs, the Au nanoparticles were electrodeposited on the surface of rGO-CNTs. A kind of catalytic material which is known as Au/rGO-CNTs was obtained. The experimental results show that the fabricated catalytic materials exhibit excellent electrocatalytic properties. The Au/rGO-CNTs/GCE sensor possesses an ultro-high sensitivity of 9.73 μA·μM-1·cm-2 in 0.3-319 μM, and a low detect limit of 0.065 μM.（4） Based on the results of the previous studies, we prepared the micron fibers with a diameter of 200 μm using GO and GO-CNTs. The electrical characteristics test was conducted when the fibers were reduced, indicating that the density and conductivity of graphene-CNTs fiber are much higher than graphene fiber. The AuNPs/graphene fiber and AuNPs/graphene-CNTs fiber electrodes were used for hydrazine sensing when the Au nanoparticles were electrodeposied on the fiber surface. The experimental results show that the fabricated two kinds of fiber electrodes exhibit excellent properties, the sensitivity of AuNPs/graphene-CNTs fiber can reach to 7.32 μA·μM-1·cm-2 in the linear concentration of 0.5-968 μM, and its detection limint also can reach to 0.071 μM. The fiber electrode has the advantage of easy to use and low cost.The electrocatalytic properties toward hydrazine for the three different kinds of nanomaterials were studied in the dissertation, and the parameters of the fabricated hydrazine sensors were calculated. The experimental studies provide meaningful understanding for in-depth study of the hydrazine catalytic based on other nanomaterials. The obtained Au nanoparticles modified rGO-CNTs nanocomposite and its 1D fiber structure exhibit ultro-high detection sensitivity, and the fiber electrode can be used in microfluidic chip detection which could improve the detection efficiency and saving sample. These studies provide new strategy and method for fabricating high-performance hydrazine electrochemical sensor.