Non-enzyme Electrochemical Sensor Based On Metal Oxide And Its Composite Nanomaterials

Nanomaterials,including metals,metal compounds and carbon nanomaterials,etc.,have been developed rapidly because of the large surface area,the catalytic performance,strong adsorption capacity,high electrical conduction ability,biological properties,good compatibility,and also made the development of technology and practical applications of nanomaterials..Moreover,the microscopic structure of nanomaterials,such as dimension,particle size and shape etc.,will affect their physical and chemical properties.The cuprous oxide（Cu₂O）,carbon quantum dots（CQDs）,metal-organic frameworks（MOFs）were the research object.The morphology of cuprous oxide based on its electrochemical properties have been investigated;then we chose the octahedral Cu₂O,which with better electrochemical performance and easy synthesis,to prepare the composites with carbon quantum dots and to study the electrochemical performance of the CQDs/octahedral Cu₂O.Morever,a new metal organic framework nanomaterial was synthesized and constructed a kind of hydrogen peroxide sensor,and achieved very good electrocatalytic effect.This result demonstrated that the new organic metal framework will be a promising material for non-enzymatic H₂O₂ sensor.The followings are our work:（1）Firstly,we synthesized four different morphologies of Cu₂O nanocrystals（cube,rhombic dodecahedra,octahedra,extended hexapod）by a hydrothermal method.And then,the four different morphologies of Cu₂O were immobilized separately on glassy carbon electrode（GCE）to construct non-enzymatic hydrogen peroxide（H₂O₂）sensor.We systematically explored the electrocatalytic activities of the four different Cu₂O nanocrystals towards H₂O₂,which is strongly dependent on the shape of the Cu₂O nanocrystals.It is showed that the modified electrodes exhibited excellent electrocatalysis to H₂O₂ reduction by the electrochemical experiments.Moreover,the{111}-bounded extended hexapod Cu₂O,{111}-bounded octahedral Cu₂O and the{110}-bounded rhombic dodecahedral Cu₂O nanocrystals are significantly active than the{100}-bounded cubic Cu₂O nanocrystals,as the{111}and{110}face contain copper atoms on the surface with dangling bonds,and then are expected to interact more strongly with negatively charged ions or molecules.（2）Non-enzymatic electrochemical sensors for the detection of glucose and hydrogen peroxide were designed based on novel nanostructure electrocatalyst of CQDs/octahedral Cu₂O nanocomposites.The CQDs/octahedral Cu₂O nanocomposites has been smoothly by a facile method with ultrasonic treatment and the morphologies of the synthesized materials were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）with Energy dispersive X-ray spectroscopy（EDS）and powder X-ray diffraction measurements（XRD）.Compared to octahedral Cu₂O,the CQDs/octahedral Cu₂O exhibited preferable electrocatalysis to the glucose oxidation and H₂O₂ reduction.Amperometric sensing of glucose was realized with a linear response range from 0.02 to 4.3m M,a detection limit of 8.4μM（S/N=3）.The interferents of ascorbic acid（AA）,uric acid（UA）,dopamine（DA）and sodium chloride（Na Cl）was also detected using the CQDs/octahedral Cu₂O modified electrode,the results showed good selectivity for glucose detection.Besides,the nonenzymatic sensor also has good performance to the electrocatalytic reduction of H₂O₂,with a linear response range from 5μM to 5.3 m M and a detection limit of2.8μM（S/N=3）.The CQDs/octahedral Cu₂O nanocomposites have good selectivity for the H₂O₂detection with the AA,Na Cl and UA.（3）A new lanthanum metal-organic framework,[La（BTC）（H₂O）（DMF）],was synthesized under mild hydrothermal conditions.The synthesized[La（BTC）（H₂O）（DMF）]was characterized by SEM/EDS,TEM,XRD and fourier transform infrared spectroscopy（FT-IR）.Its electrochemical properties and electrocatalytic activity towards H₂O₂ reduction in acidic media were studied by cyclic voltammetry（CV）and amperometric current-time response.The CVs of[La（BTC）（H₂O）（DMF）]modified electrode showed a pair of redox peaks at ca.-0.03 and 0.25 V in 0.1 M p H 5.0 PBS which correspond to the La^III（OH）-MOF/La^II（H₂O）-MOF couple.The[La（BTC）（H₂O）（DMF）]modified electrode showed high electrocatalytic activity towards H₂O₂ reduction at ca.-0.7V.The modified electrode displayed a linear range from 5μM to 2.665 m M and a limit of detection of 0.73μM to H₂O₂.The[La（BTC）（H₂O）（DMF）]modified electrode also possessed well selectivity and stability.Thus,the[La（BTC）（H₂O）（DMF）]will be a promising material for non-enzymatic H₂O₂ sensor.