Designed And Synthesis Of Transition Metal Oxides And Construction Of Small Molecule Sensing Platform

Electrochemical sensor is an analytical method,which detected the substanceby selectively chemically interaction,and convert it into an electrical signal.Especially,the electrochemical sensor based on materials has been applied in the detection of small molecule due to its low cost,easy preparation,high sensitivity,good selectivity and fast response,and it has been applied in the detection of small molecule.The performances of electrochemical sensors are related to the kind and structure of electrode materials,so it is very important to choose suitable electrode materials.Transitional metal oxides（such as Co₃O₄,CuO and so on）have been the focus of research because of their low cost,high electrocatalytic property,good conductivity and stability.On the other hand,carbonaceous materials have excellent electrical conductivity and large specific surface area.Both of them have great application prospects in the field of electrochemical sensors.In this study,metal oxides and metal oxides/carbon materials were used to construct electrochemical sensors to detect small molecules.The main work is summarized as follows:（1）The synthesis of Co₃O₄/biomass-derived carbon composites and their applications in H₂O₂detectionFirstly,three kinds of biomass-derived carbon（CLC,LSC,PNC）were prepared by calcining three kinds of raw materials（cypress leaves,loofah sponge and pine needle）.Then Co₃O₄was synthesized by hydrothermal and calcination process.Co₃O₄/biomass-derived carbon composites were prepared by adding different amounts of various carbon during the preparation of Co₃O₄.X-ray diffraction,scanning electron microscopy,Raman analysis were used to characterize the samples.The electrochemical performances of the materials were tested by cyclic voltammetry,chronoamperometry,and electrochemical impedance spectroscopy.The results displayed that the electrocatalytic properties of all the composites had improved.Especially,the electrocatalytic performance of Co₃O₄/LSC is higher than that of other two composites,and when the mass fraction of LSC is 2%,it exhibites the highest electrochemical activity towards H₂O₂.Under the optimal condition,the sensor based on Co₃O₄/LSC-2 exhibited a broad linear range from 5.00μM to 11.40 m M,with a detection limit of 0.15μM（S/N=3）and a high sensitivity of 47.83μA m M^-1cm^-2.The sensor also exhibited good selectivity,reproducibility and stability.（2）The synthesis of CuO/carbonaceous materials and their applications in glucose and dopamine（DA）detectionFirstly,Porous carbons（PC）,carbon sphere（CS）and g-C₃N₄（CN）were successfully synthesized.CuO/carbon composites were prepared by adding different amounts of these carbon materials during the synthesis of CuO.Compared with pure CuO,the electrocatalytic abilities of the composites were improved.When CuO is combined with g-C₃N₄and the mass fraction of g-C₃N₄is 5%,the material（CuO/CN-5）has better electrocatalytic activity.In 0.1 M Na OH solution,the linear response range for the detection of glucose was from 0.5μM to 8.5m M,a detection limit of 0.150μM,and a sensitivity of 0.274μA·μM^-1·cm^-2.In p H 7.0phosphate buffer solution,the two linear response ranges for the detection of DA were0.2-16.0μM and 16.0-78.7μM,a detection limit of 0.06μM.The better electrocatalytic properties of CuO/CN-5 are attributable to the synergistic effects between CuO and g-C₃N₄,the specific sheet structure of g-C₃N₄and the active sites provided by N atoms in g-C₃N₄.（3）The synthesis of Cu_xCo_3-xO₄and their applications in glucose and H₂O₂detectionCu_xCo_3-XO₄（x=0.5,1,1.5,2）were prepared by a two-step hydrothermal and calcination process by changing the amounts of Cu（NO₃）₂·3H₂O and Co（NO₃）₂·6H₂O.The results of electrochemical tests suggested that when x=1,the corresponding product CuCo₂O₄exhibited better electrocatalytic activity.The sensor based on CuCo₂O₄had a linear range from 2.5μM to 7.9 m M,with a sensitivity of 386.5μA m M^-1cm^-2for the detection of glucose.And it had a linear range from 10.0μM to 8.9 m M,with a sensitivity of 94.1μA m M^-1cm^-2for H₂O₂.The sensor also exhibited good selectivity and long-term stability.CuCo₂O₄exhibits good catalytic activity can be attributable to the synergistic effect between metal ions,it provides more active sites and improves the conductivity.Also,its unique hollow core-shell structure increases contact areas of material and electrolyte,which provide the ion transport path.Therefore,CuCo₂O₄has better electrocatalytic activity towards glucose.