Design Of Electrochemical Sensors Electrodes And Their Detection Of Small Biomolecules

Small biomolecules play an important role in human body.Their concentration variation can be regarded as a signal for certain health problems.Their accurate detection is thus of significance for body illness diagolosis.Among all kinds of detection techniques,electrochemical sensors with glassy carbon electrode(GCE)modified with various electroactive materials shows great potential in monitoring small biomolecules for its merits of simple operation,high sensitivity,rapid response and low cost.For the detection of different kinds of small biomolecules,including dopamine(DA),uric acid(UA),sugars and peroxide hydrogen(H2O2),this thesis focuses on the preparation of several electrochemical sensors electrodes.The main contents of this thesis is described as follows.1.For the simultaneous detection of DA and UA,poly-L-glutathione(P-L-GSH)film has been prepared directly on the GCE surface(P-L-GSH/GCE)through a facile electropolymerization.The modified electrode achieved simultaneous determination of DA and UA by cyclic voltammetry(CV)and differential pulse voltammetry(DPV).The positively charged P-L-GSH film contributes to the preconcentration of analytes by electrostatic interactions,and its porous structure increases the electro-active area.Compared with bare GCE,the P-L-GSH/GCE exhibits great electrocatalytic activities toward DA and UAby lowering the oxidation overpotential and magnifying the peak currents significantly.The optimal electropolymerization circle is found to be 12.The simultaneous determination of DA and UA with P-L-GSH/GCE features lower limits of detection(0.36 ?M for DA,3.45 ?M for UA)and wider linear ranges(2?300?M for DA,10-500 ?M for UA).In addition,the as-prepared sensor is also suitable for the detection of DA and UA in human urine samples.2.For the detection of glucose,NiMn-layered double hydroxide(LDH)has been prepared via a simple hydrothermal method.The electrode modified by directly applying NiMn-LDH dispersion(NiMn-LDH/GCE)exhibits good electrocatalytic activities toward the oxidation of glucose.The lamellar structure of NiMn-LDH increases electron and ion transfer channel.Ni3+ions act as oxidants for electrochemical oxidation of glucose.The linear range for the detection of glucose is 2?671 ?M,sensitivity is 97.31 ?A mM-1 cm-2 and detection limit is 2 ?M.3.For the detection of sugars(including glucose,sucrose,erythritol and mannitol)and H2O2,NiMn-layered double hydroxide coated graphene oxide nanosheets(NiMn-LDH@GO)have been prepared via one pot method on the basis of previous chapter.Their similar lamellar structures were conducive to the formation of the composites.GO not only impersonates the support for LDHs growth but also serves as electron transfer channel.Compared with NiMn-LDH,NiMn-LDH@GO shows higher sensitivity toward the dection of glucose.It was found that the optimal GO addition is 0.1 mg mL-1.In addition,the electrochemical behaviour of sugars(glucose,sucrose,erythritol and mannitol)and H2O2 on NiMn-LDH@GO/GCE has been systematically studied.NiMn-LDH@GO/GCE shows great catalytic activities toward sugars and H2O2,with sensitivities of 839.2,465.8,910.5,969.2 and 96.82 ?AmM-1cm-2,respectively,for glucose,sucrose,erythritol,mannitol and H2O2.The corresponding detection limits are found to be 1.2,2.1,1.0,1.4,4.4 ?M,respectively,for glucose,sucrose,erythritol,mannitol and H2O2.