Shape-controlled Fabrication Of Metal Oxides/phosphates Based Hybrid Structures For Nonenzymatic Electrochemical Sensor Applications

This thesis explores the shape-controlled fabrication of hybrid structures composed of metal oxides/phosphates for nonenzymatic electrochemical sensor applications.The research focuses on developing the cost-effective and reliable methods for producing these hybrid structures with precisely controlled morphologies,which can improve their electrochemical properties and sensing performance.The study investigates the impact of various fabrication parameters on the final structure’s morphology and electrochemical behavior.The results of this research can contribute to the development of advanced nonenzymatic electrochemical sensors for various applications,including glucose and/or H₂O₂ sensor.The relevant research works are summarized as follows:（1）A novel Ni（OH）₂ three-dimensional nanosheets-coated marigold-like ZnO microflower（mg-ZnO@Ni（OH）₂ NSs）hybrid structure is designed for the nonenzymatic electrochemical sensing of glucose.The morphological evolution of mg-ZnO and mg-ZnO@Ni（OH）₂ NSs is achieved by a one-pot solvothermal strategy through control over the reaction conditions without any assistance of an external shape-controlling surfactant.Furthermore,the as-fabricated mg-ZnO and mg-ZnO@Ni（OH）₂ NSs are systematically evaluated by different spectroscopic and microscopic characterization tools,and then the tailor-made mg-ZnO@Ni（OH）₂ NSs are successfully used to launch a nonenzyme-based sensing avenue for real-time monitoring of glucose.Typically,highly exposed homogeneous nanocorners of mg-ZnO and the synergetic effect of Ni（OH）₂ coating,collectively improved the electrocatalytic efficacy of the designed catalyst,as revealed through electrochemical measurements.Moreover,the mg-ZnO@Ni（OH）₂NSs-modified glassy carbon electrode offered excellent amperometric performance for glucose monitoring,comprising high sensitivity 259.78μA m M^-1 cm^-2,wide linear range（0.084 m M to0.941 m M and from 0.941 m M to 6.50 m M）,low limit of detection（LOD）（0.06μM,S/N=3）,good stability and high analyte selectivity.Thus,the achieved distinctive morphological,chemical and electrochemical aspects raise the spirit for the potential applicability of mg-ZnO@Ni（OH）₂ NSs hybrid-based sensors in human serum samples for real-time glucose sensing.（2）The unique core-shell structure based on carbon-doped and Ni（OH）₂ nanofilms wrapped ZnO microballs（NFs-Ni（OH）₂/ZnO@C MBs）is synthesized for concurrent monitoring of glucose and hydrogen peroxide（H₂O₂）.The distinctive ball-like morphology of the designed structure is achieved through a facile solvothermal strategy by the control of reaction conditions and mixing of metal salts.Typically,ZnO@C MBs offer highly conductive core,and the shell of Ni（OH）₂ nanofilms increases the density of catalytic active sites in the designed structure.Notably,ethanol amine furnishes an essential medium for structural growth and a carbon source in coordination with ethylene glycol to boost the conductivity of the core-shell hybrid structure.Thanks to the novel hybrid,NFs-Ni（OH）₂/ZnO@C MBs offers multifunctional electrocatalytic activities for glucose oxidation and H₂O₂reduction,as revealed through cyclic voltametric outcomes.Thus,the interesting physical and chemical properties as well as the brilliant electrocatalytic efficacy of as-fabricated NFs-Ni（OH）₂/ZnO@C MBs core-shell hybrid structure,raise the spirit to design a multi-mode sensor for glucose and H₂O₂ screening.The NFs-Ni（OH）₂/ZnO@C MBs/GCE glucose sensor presented good sensitivities(647.899&161.550μA m M^-1 cm^-2),a quick response（<4 s）,lower LOD（0.04μM）,and wide detection range（0.004-1.13&1.13-5.02 m M）.Similarly,the same electrode revealed excellent H₂O₂ sensing features including good sensitivities,two linear parts of 3.5-452 and 452-1374μM,and LOD of 0.03μM as well as high selectivity.Thus,the development of novel hybrid core-shell structure is useful for potential applications in glucose and H₂O₂ screening from environmental and physiological samples.（3）We design for the first time,a binary metal phosphate（BMP）heteroarchitecture based on nickel phosphate nanodots supported on copper phosphate microflowers（NDTs Ni₃（PO₄）₂@Cu₃（PO₄）₂ MFs）.The surface characterizations reveal the interconnected cross-network of vertically oriented 3D nanosheets（NSs）which leads to the self-assembly of microflowers.In addition,the Ni₃（PO₄）₂ nanodots,with an average diameter of 2.6 nm,are uniformly distributed throughout the structure,providing greater number of active centers on the surface of the designed catalyst.Thus,the customized structure has the potential to function as an excellent electrocatalyst by providing sufficient reaction space through the highly exposed edges of 3D nanosheets,and high density active site owe to the presence of NDTs.Typically,the Cu₃（PO₄）₂ acts as an electron mediator by facilitating the Cu²⁺/Cu³⁺redox couple,while the Ni₃（PO₄）₂ enhances the electrocatalytic oxidation of glucose.Thus,owing to its unique physical and chemical aspects,the NDTs Ni₃（PO₄）₂@Cu₂（PO₄）₂ MFs demonstrate superior electrocatalytic efficacy for glucose sensing.Thanks to the novel NDTs Ni₃（PO₄）₂@Cu₂（PO₄）₂MFs BMP for offering exceptional sensitivities(2197.119 and 206.111μA m M^–1 cm^–2),a wide detection range（0.009-0.491 m M and 0.491-14.83 m M）,a short response time（<1 s）,and a low LOD（0.06μM,S/N=3）.Moreover,the designed sensor presents good reproducibility,admirable stability and excellent selectivity.Thus,the NDTs Ni₃（PO₄）₂@Cu₃（PO₄）₂ MFs are promising for the potential applications in glucose sensor,to monitor glucose in human serum and other body fluids.