| Graphitic carbon nitride?g-C3N4?,as a two-dimensional material,has attracted a great deal of attention due to its excellent physical and chemical properties such as unique optoelectronic characteristics,thermal and chemical stability.Owing to its rich nitrogen,g-C3N4 has great potential in the application of electrochemical sensing.However,the pristine g-C3N4 presents low specific surface area,poor conductivity and chemical inertness,which restricts applications of g-C3N4 in many fields,especially in the field of electrochemical sensor.Therefore,a growing number of research works have been dedicated to functionalization of g-C3N4 including texture and property modification.The modified g-C3N4 and its composites,with improved functionality,have broadened their applications in the field of sensor.In this dissertation,functionalized graphitic carbon nitride and its composites were prepared and used as electrode modifier material or electrode materials for electrochemical sensing.The main research content can be depicted in the below:?1?Graphitic carbon nitride?g-C3N4?is synthesized through direct pyrolysis of the melamine,and the pristine g-C3N4 is further treated by sufficient protonation and ultrasonication.The resultant g-C3N4 nanosheets,with two-dimensional thin nature,exhibit enhanced ionic conductivity and large specific surface area.Density function theory?DFT?calculations of the electrical properties of the protonated g-C3N4 nanosheets demonstrate that the higher level of protonation enables g-C3N4 to have better conductivity.In addition,the protonated g-C3N4 nanosheets?g-C3N4 NS?also show excellent electro-catalytic activity and have been employed as electrochemical sensing platforms for non-enzymatic electrochemical detecting hydrogen peroxide?H2O2?.The results demonstrate that the modified electrode based on the g-C3N4 NS,can detect H2O2 in the linear range of 1.60×10-6-3.72×10-3 mol/L,the detection limit is 4.00×10-7 mol/L.The g-C3N4 NS have great potential for application in future sensor development and biomedical analysis.?2?The modified electrode based on g-C3N4 NS has been successfully used for highly selective determination of paracetamol?PCM?.Owing to rich nitrogen-containing active groups,the g-C3N4 NS can provide a lot of anchoring sites for PCM molecule.Under the optimal conditions,the linear relationship was found between the peak current of the stripping voltammetry of paracetamol and the concentration of PCM in the range of 1.70×10-6-2.02×10-3 mol/L with a correlation coefficient R2 = 0.996,and the detection limit can be down to 1.50 x 10-7 mol/L?S/N=3?.The electrodes based on the g-C3N4 NS for PCM detection demonstrated good stability and high selectivity.?3?Graphitic carbon nitride nanosheets?g-C3N4 NS?were prepared and used for self-templated electrodeposition of copper and copper oxide nanostructures.The as-prepared g-C3N4 NS can provide a lot of anchoring sites for copper ions in the process of electrodeposition.The electrodeposited CuO@Cu demonstrates high density and good uniformity.During the electrodeposition,the addition of nickel ions had enabled to entrap Ni ions in the lattice of CuO.The CeO2-CuO@Cu/g-C3N4 NS composites have been prepared by the addition of Ce ions in the process of electrodepositing CuO@Cu onto g-C3N4 NS.The cerium and nickel ions,as the additives,can effectively improve the density and uniformity of the electrodeposited CuO@Cu.Furthermore,the successful entrapment of CeO2 and Ni ions greatly improve electrochemical performance of CuO@Cu/g-C3N4 NS/ITO in the non-enzymatic detection of glucose.The Ce and Ni ion additives showed a synergistic effect on improving uniformity and density of the electrodeposited CuO@Cu and electro-catalytic properties of as-prepared composites.The as-prepared CuO@Cu/g-C3N4 NS/ITO,CeO2-CuO@Cu/g-C3N4 NS/ITO and Ni-doped CuO@Cu/g-C3N4 NS/ITO have been respectively used for non-enzymatic detection of glucose.These three proposed electrodes all demonstrate good electrochemical performance in the non-enzymatic detection of glucose.The CeO2-CuO@Cu/g-C3N4 NS/ITO and Ni-doped CuO@Cu/g-C3N4 NS/ITO appear to greatly improve the electro-catalytic activity toward the oxidation of glucose.Among these three electrodes,the Ni-doped CuO@Cu/g-C3N4 NS/ITO demonstrated the best electrochemical performance in the detection of glucose.These three proposed electrodes all demonstrated good stability and anti-interference performance.?4?The graphitic carbon nitride?g-C3N4?/iron oxide?a-Fe2O3?composites have been prepared by a one-step pyrolysis of Prussian blue?PB?and melamine.The Fe2O3 nanoparticles derived from PB effectively protect the thin layers of g-C3N4 from restacking and expanding.The as-prepared g-C3N4/a-Fe2O3 composites exhibit large specific surface area and excellent electrochemical performance in the non-enzymatic detection of glucose.The modified electrodes based on the g-C3N4/a-Fe2O3 hybrids are also used for the non-enzymatic detection of glucose.The as-fabricated modified electrode exhibits good electrochemical performance towards the oxidation of glucose with a response time<3 s and a linear range of 2.00×10-6-2.40×10-3 mol/L.The electrodes modified by the g-C3N4/a-Fe2O3 composites demonstrated good anti-interference performance and stability.?5?A simple method was proposed for the synthesis of graphitic carbon nitride?g-C3N4?/iron oxide-copper nanostructures through a one-step pyrolysis of Cu3[Fe?CN?6]2 and melamine.The iron oxide and copper nanostructures,derived from Cu3[Fe?CN?6]2,were decorated onto g-C3N4 nanosheets,which can effectively protect the resultant g-C3N4 NS from restacking.The derived Fe2O3 and Cu nanostructures greatly enhance the electro-catalytic property of as-prepared composites.Three components including g-C3N4 NS,Fe2O3 and Cu cooperatively enhance the electrochemical performance of non-enzymatic glucose detection.Modified electrodes based on g-C3N4/Fe2O3-Cu composites could detect glucose in the range of 6.00 x 10-7-2.00×10-3 mol/L with a detection limit of 3.00×10-7 mol/L.The as-fabricated modified electrodes also demonstrated good stability and anti-interference performance. |
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