Electrochemical Sensing Research Based On Several Metal/Carbon Nanocomposites

Advanced nanomaterials are used to establish new principles and methods of electrochemical sensing to significantly improve the analytical ability of multi-component samples and the analytical performance of sensors,and expanding the application fields of electrochemical sensing are still one of the fast-growing areas in electroanalysis.This dissertation prepared porous carbon materials,metal/oxide composites with different morphologies and noble metal nanomaterials with different crystal structures,and then various electrochemical sensors were fabricated based on these nanocomposites.The type,structure,morphology and its electrocatalytic properties of nanocomposites on the sensing interface,and their effect on regulating and improving the response of the sensor were investigated.This dissertation proposed some novel methods for detecting small molecules（e.g.DA）.The study provides useful reference information for constructing high-performance electrochemical sensing interfaces and the analyses of biological small molecules.The dissertation is divided into four chapters,the main research is as follows:1.Electrochemical sensors based on Ag/HCS,PtPd/POSS/HCS,Au/p-PDA/MWCNT/GO nanomaterials which were synthesized by template method and chemical etching method were fabricated.The composition,structure,morphologies and their electrocatalytic properties of nanomaterials on the sensing interface and the effect on regulating the response of the sensor were investigated,which established new methods for determination of DA,N2H4 and simultaneous determination DA,AA,UA.The experimental indicated that the BET specific surface area of the prepared HCS reached 568.6 m² g^-11 and a pore size of 4.8 nm,the linear range of DA based on Ag/HCS electrochemical sensor were3.0-2.0×10³mM and 2.0×10³-7.0×10³mM,with the detection limit was 0.6mM,and the sensitivity were 757.1μA mM^-11 cm^-22 and 315.2μA mM^-11 cm^-2,respectively.The linear range of simultaneous detection of AA,DA,UA based on Pt Pd/POSS/HCS electrochemical sensor were 50.0-3×10³mM,5.0-5.0×10²mM,1.0×10²-4.0×10³mM,with the detection limit were 8.7mM,1.7mM,24.8mM,and the sensitivity were 31.0mA mM^-1cm^-2,692.9mA mM^-11 cm^-22 and 71.4mA mM^-11 cm^-2,respectively.The BET specific surface area of the porous MWCNT/GO was increased to 289.8 m² g^-1,the pore volume was 0.97m³ g^-1.The linear range of N₂H₄ sensor were 1.0-3.0×10³mM and 3.0×10³-5.5×10⁴mM,with the detection limit was 0.3mM and the sensitivity were 524.3mA mM^-11 cm^-22 and 98.0mA mM^-11 cm^-2,respectively.Compared with the reported sensors,the porous structure of carbon materials were used to increase the mass transfer rate.The former sensor exhibited a lower detection limit and a higher sensitivity.The sensor for simultaneous detection DA,UA,AA exhibited a broad linear range.The latter N₂H₄ sensor exhibited a linear range that spans four orders of magnitude.Compare these two HCS-based electrochemical sensors,the oxidation potential of AA,DA and UA can be well separated after being modified by POSS.2.Electrochemical sensors based on different morphologies Au@Ni/rGO,sea urchin-shaped Pt@Cu/rGO and intertwined Pt@Co₃O₄ which were synthesized by hydrothermal method or sol-gel reaction were fabricated.The composition,structure,morphologies and their electrocatalytic properties of nanomaterials on the sensing interface,and the effect on regulating the response of the sensor were studied,which established new methods for determination of N₂H₄ and nitrite.The experimental results indicated that the Au@Ni nanoparticles were prepared with the morphologies of heterodimer or core-shell,the N₂H₄ sensors based on Au@Ni have lower peak potential at 0 V and 0.07 V,the linear range were 3.0-1.0×10³μM,1.0×10³-2.0×10⁴μM and 0.2-1.0×10³μM,1.0×10³-9.0×10³μM,with the detection limit were 0.9μM and 0.06μM,and the higher sensitivity were256.7μA mM^-11 cm^-22 and 133.4μA mM^-11 cm^-2.The linear range of N₂H₄ sensor based on sea urchin-shaped Pt@Cu/rGO was 0.4-1.2×10⁴μM,with the detection limit and sensitivity were 0.1μM and 54.8μA mM^-11 cm^-2,respectively.The linear range of nitrite sensor based on the intertwined Pt@Co₃O₄ nanocomposite was 3.0-7.0×10⁴μM,with the detection limit and sensitivity were 0.97μM,40.3μA mM^-11 cm^-2,respectively.Compared with the reported sensors,the synergistic effect between the components of the composite material enhanced the electrocatalytic activity and stability of the sensing materials,which made the former sensor has a lower oxidation peak potential of 0V and a lower detection limit,the other two sensors have a broader linear range.Compared with the two N₂H₄sensors,the detection limit of the electrochemical sensor based on Au@Ni-BHD/rGO is reduced by two times.3.Pt CNC nanoparticles grown on the surface of GO,MWCNT/GO were synthesized and the electrochemical sensors based on Pt/rGO,Pt CNC/rGO,Pt CNC/MWCNT/rGO nanocomposites were fabricated.The composition,structure,morphologies and their electrocatalytic properties of nanomaterials on the sensing interface and the effect on regulating the response of the sensor were studied,which established new methods for determination of DA,H₂O₂ and simultaneous detection DA,UA.The experiment results indicated that the electroactive surface area of Pt concave cubes was 0.73 cm²,the linear range of DA electrochemical sensor based on Pt/rGO were 3.0-7.0×10²μM,7.0×10²-4.0×10³μM,with the detection limit and sensitivity were 0.74μM and 205.7μA mM^-11 cm^-22 and 51.4μA mM^-11 cm^-2,respectively.The Pt CNC was mainly enclosed by{610}and{510}facets,the linear range of H₂O₂ electrochemical sensor was 3.0-1.0×10⁵μM,the detection limit and sensitivity were 0.7μM and 5.7μA mM^-11 cm^-2,respectively.The Pt CNC on the surface of MWCNT/rGO was mainly enclosed by{410}and{510}facets,the linear range of simultaneous detection DA,UA electrochemical sensor were0.8-3.0×10²μM,1.0-3.0×10²μM and 3.0×10²-1.0×10³μM,with the detection limit were 0.27μM and 0.35μM.Compared with the reported sensors,the high index facets Pt CNC was used as the sensing materials,which made the first sensor has a wider linear range,and the linear detection range of the middle sensor spans five orders of magnitude,and the latter sensor can completely separate the oxidation peaks of DA and UA,and has a lower detection limit and higher stability.Comparing the two DA sensors,the sensitivity of electrochemical sensors based on Pt CNC/MWCNT/rGO has been improved by at least four times.