Study On The Preparation Of Functionalized Graphene And MoS₂ Nanosheets With The Developments Of Electrochemical Sensors

Two-dimensional nanomaterials, particularly graphene and graphene-like MoS2 nanosheets, with their unique structures and properties, obtain an increasing number of interests. Significantly, Graphene and MoS2 nansheets exhibit potential applications in fabrication of biosensors based on electrochemical methods. In order to achieve a better electric conductivity and unique catalytic activity, the functionalizations of graphene and MoS2 nanosheets with other nanomaterials possessing great optical and catalytic abilities were carried out. Furthermore, functionalized nanomaterials, combining the owned character with other excellent properties of other nanomaterials, improve the sensitivity and selectivity of electrochemical sensors and further expand the relevant applications.Recently, electrochemical ensor used for the detection of molecules is a kind of approach using electrochemical signals to acquire the information of biological activities. On the basis of its excellent properties of easy operation, high senstivity, and selectivity, electrochemical sensor displays significant application in diagnose of illness and detection of biological area. Those developed sensors have been widely applied for the practical determination in various fields. In this paper, functionalized graphene and MoS2 nanosheets were used for the modification of electrodes, contributing to the detection of small molecules, such as ascorbic acid, dopamine, and uric acid. The main context was shown below:Part 1:A Novel Electrochemical Sensor Based on Hemin Functionalized Graphene Oxide Sheets for the Simultaneous Determination of Ascorbic Acid, Dopamine, and Uric Acid. Due to its great electrochemical activities, conductivity, and biological stability, graphene has been considered as an important platform in electroanalysis. However, due to the inertness of graphene to some special reactions, the wide applications of graphene were limited. In this paper, a simple, convenient, and easy method was developed to prepare hermin-functionalized graphene, which was successfully used to the modification of glassy carbon electrode. Furthermore, the modified electrode was used to development of biosensors related to small biomolecules, achieving the simultaneous determination of ascorbic acid, dopamine, and uric acid. Finally, the developed sensor exhibited great selectivity and high sensitivity in paractical determinations with satisfactory results.Part 2:The Preparation of Oxidized MoS2 Nanosheets and Their Application in Development of Nitrite Sensor. With the penetration of graphene-related research, graphene-like MoS2 nanosheets caused more and more attention. However, it was noticed that the research of MoS2 nanosheets was only related to the construction of electric device, hydrogen evolution catalysis, materials for Li-ion battery electrode and the relevant application of MoS2 nanosheets in analytical chemistry was limited. Due to the background of environmental issue, food security problem, an innovation in determination of pollutant was needed seriously. On the basis of mentioned issues, a proposed method that using electrochemical techniques to oxidise MoS2 nanosheets to obtain oxidised-MoS2 nanosheets was developed based on electroanalysis techniques. Given that the excellent catalytic activities of oxidised MoS2 nanosheets to the oxidation of nitrite, relevant research of determination of nitrite in practicle samples using oxide-MoS2 nanosheets modified electrode was conducted with a satisfactory result.Part 3:Au Nanoparticles Functionalized MoS2 Nanosheets Based Electrochemical Sensor for the Simultaneous Determination of Ascorbic Acid, Dopamine, Uric Acid, and Nitrite. Considering the wide application of Au nanoparticles and their preparing method is an easy process, a method of spontaneous reduction using MoS2 nanosheets was developed, leading to the formation of Au nanoparticles functionlized MoS2 nanosheets composites. In the whole process, the composites were obtained without the addition of any other reduction, which was considered as an environmental-friendly, and simple approach. Furthermore, the as-prepared composites were found to exhibit great catalytic activity to the oxidation of some small molecules. Due to the great catalytic activity of Au nanoparticles functionlized MoS2 nanosheets, a novel electrochemical sensor was developed and used for the simultaneous determination of ascorbic acid, dopamine, uric acid, and nitrite with satisfactory results.