Nanooxides Sensitized Electrochemical Sensors For Tryptophan And Tyrosine

Amino acids are the basic elements for the synthesis of proteins and peptides,as well as important biologically active molecules,which play a key role in signaling pathways and metabolic regulation.Tryptophan is an essential amino acid for normal growth of infants and young children and nitrogen balance for adults.Excessive tryptophan in the human body can cause restlessness,confusion,diarrhea,fever,nausea,etc.,and the level of tryptophan in the blood is closely related to liver disease.Tyrosine is an important precursor of biosignal molecules such as epinephrine,norepinephrine and dopamine.Tyrosine deficiency is associated with depression.Therefore,the determination of amino acid content has important practical significance in food and clinical applications.Metal oxides are used as important electrode materials in various electrochemical applications.Compared with other functional electrode materials,metal oxides have the characteristics of uniform size,consistent shape,and clear crystallinity.Different preparation methods can obtain metal oxides of different shapes,such as tubular,cubic,linear and spindle-shaped,which can be adjusted to the desired application.Graphene and modified graphene are suitable nanomaterials for constructing energy sensors due to their large specific surface area,high conductivity and excellent electrochemical activity.Therefore,this thesis looks for a suitable nano-metal oxide nanocomposite modified graphene modified electrode for the determination of tryptophan and tyrosine,and designs three metal oxide-modified graphene nanocomposite materials modified glassy carbon electrode for the determination of tryptophan and tyrosine.Tyrosine is tested,the main research contents of this subject are as follows:（1）Constructing an electrochemical sensor of tryptophan using Cu₂O-electrochemically reduced graphene（Cu₂O-ERGO）composite materialAn electrochemical method for the determination of tryptophan based on Cu₂O-electrochemically reduced graphene modified glassy carbon electrode（Cu₂O-ERGO/GCE）was established.The electrochemical behavior of tryptophan on Cu₂O-ERGO/GCE was studied.The results show that the oxidation peak current of tryptophan at the Cu₂O-ERGO/GCE is much higher than the oxidation peak current at the bare GCE.Optimized the measurement conditions of supporting electrolyte,p H,scanning rate,deposition potential and time.When the concentration of the tryptophan solution is 0.02–20μM,the oxidation peak current has a linear relationship with the concentration of tryptophan.The detection limit is0.01μM（S/N=3）.The method is sensitive and simple.Successfully applied to the determination of tryptophan in medicine and human samples（2）Constructing tryptophan electrochemical sensor using Co₃O₄-nitrogen-doped graphene（Co₃O₄-NRGO）composite materialCo₃O₄-NRGO composite material were prepared by a one-step hydrothermal method and modified on a glassy carbon electrode to determine tryptophan.The prepared materials were characterized by scanning electron microscopy,energy dispersive spectroscopy,and X-ray diffraction.The effects of enrichment potential,enrichment time and Co₃O₄-NRGO loading on the glassy carbon electrode on the determination of tryptophan on the modified electrode are discussed.The optimal p H of the buffer solution=2.52.In the range of tryptophan concentration of0.007-10μM,the oxidation peak current of tryptophan is proportional to its concentration.The detection limit is 3 n M（S/N=3）.（3）Constructing a tyrosine electrochemical sensor usingα-Fe₂O₃@Co₃O₄-nitrogen-doped graphene（α-Fe₂O₃@Co₃O₄-NRGO）composite materialThe application of a novel composite modified electrode based onα-Fe₂O₃@Co₃O₄-NRGO for the determination of tyrosine was studied.The prepared materials were characterized by scanning electron microscopy,energy dispersive spectroscopy,and X-ray diffraction.The effects of enrichment potential and enrichment time on the determination of tyrosine onα-Fe₂O₃@Co₃O₄-NRGO modified electrode are discussed.The optimal p H of the buffer solution=2.00.In the range of tyrosine concentration of0.01–10μM,the oxidation peak current of tyrosine is proportional to its concentration.The detection limit is 8.0 n M（S/N=3）.