Nanoparticles,Mesoporous Carbon Composites Electrochemical Biosensor For Determination Of Catecholamine Neurotransmitters

Catecholamine（CATs）,a class of significant material in the organism,including dopamine（DA）,adrenaline（EP）,norepinephrine（NE）mainly,which plays roles as both hormone and neuro-transmitter,regulates emotional activities and body operating.Dopamine impacts on nerve processes or phenomena such as sensation,nerve impulse transmission and addiction,existing in central nervous system of human and mammalian.And it correlates directly and strongly with people’s learning and cognitive ability.The abnormality of dopamine concentration in the human body can cause dysfunction of the central nervous system,so as to result in Parkinson’s disease,Huntington’s disease and so on.Epinephrine（EP）is converted from dopamine and secreted by adrenal that responds to stress,which controls the contraction and relaxation of smooth muscle,and then regulates the skin,blood vessel and the visceral function.The abnormal content of epinephrine is related to hypertension and thyroid disease.Therefore,it is of great theoretical and practical value for medical research and clinical diagnosis to study the methods of rapid,accurate and sensitive determination of catecholamine.The main research of this paper are divided into two aspects:the analytical application of electrodes modified with carbon molybdenum composites or mesoporous carbon materials for the determination of dopamine and its bio-coexisting,and the selective analysis of epinephrine by electrode modified with 2-mercaptoethane sulfonic acid bonded to gold nanoparticles monolayer,which are as follows:1.Electrochemical Determination of Dopamine with a Glassy Carbon Electrode Modified with Mo2C Nanoparticle.In the first part,ammonium molybdate and phenol,respectively as a molybdenum and a carbon source,were employed to form a layered MoO_x/C hybrid in moderate temperature by hydrothermal method.And the as-prepared layered MoO_X/C hybrid was annealed at higher temperature in a quartz boat under the protection of nitrogen flow to facilitate carburation to generate Mo₂C.By using ultrasonic auxiliary exfoliation method,molybdenum carbide was ultrasonicated in aqua to form its nanoparticle dispersion,taking advantage of the intercalating effect of the solvent and the huge energy from the ultrasound.Molybdenum carbide nanoparticles and Nafion were utilized to build an electrochemical biosensor on glassy carbon electrode,namely MNP-Nafion/GCE,and the test results indicated that the electrochemical response of dopamine was favorable,which is to say electrochemical behavior of dopamine had been catalyzed by MNP-Nafion/GCE.In a concentration range of 50?mol/L to 400?mol/L,electrochemical response of dopamine correlated linearly with the concentration of dopamine,and limit of detection（LOD）was 21?mol/L.Selectivity of the electrochemical biosensor for dopamine was also favorable.And the biosensor kept high activity after a week,which imply the material was stable.Finally an electrochemical biosensor was successfully built for the electrochemical determination of dopamine.2.Simultaneous Determination of Dopamine and Ascorbic Acid by Using Glassy Carbon Electrode Modified with Functionalized N-doped Ordered Mesoporous Carbon.In the second experiment,a glassy carbon electrode（GCE）modified with N-doped ordered mesoporous carbon,which had been functionalized with（NH₄）₂S₂O₈ in H₂SO₄solution,was fabricated to determine dopamine（DA）and ascorbic acid（AA）in a phosphate buffer simultaneously.In cyclic voltammetric measurements,the modified GCE showed fast response,amplified sensitivity,and high selectivity,so as to be exploited to determination of DA and AA samples successfully.The peak currents varied linearly with the concentrations of DA or AA,with linear ranges of 5.0 to 40?mol/Land40 to 200?mol/L for DA,and 0.25 to 5.0 mmol/L for AA.And the detection limit was2.6?mol/L for DA and 0.19 mmol/L for AA,respectively.3.A 2-mercaptoethane sulfonic acid bonded gold nanoparticle monolayer biosensor for determination of epinephrine.In the last part,gold nanoparticle colloid was prepared by add citrate to boiled HAuCl₄ solution quickly.And the gold nanoparticle was electrochemically deposited to a polished glassy carbon electrode to form a gold nanoparticles monolayer potentialstatically,followed with self-assembling of 2-mercaptoethane sulfonic acid（MES）by Au-S covalent bond between Au atom and mercapto group.And square wave voltammetry was used to investigate the performance of the modified electrode in the adrenaline determination:in the optimized condition of MES assembly time,pH,etc.,epinephrine concentrations was in a excellent linear correlation with its oxidation peak currents in the range of 0.5⁴0?mol/L,detection limit of 0.13?mol/L.The sensor has a low limit of detection and wide linear range,with simple preparation,successfully applied to the determination of epinephrine samples.