Electrochemical Sensors Based On Dawson-type Polyoxometalates And Their Applications For The Determination Of L-tyrosine

The use of electrochemical sensors is of critical importance not only in obvious medical applications,but also in environmental monitoring,water remediation,molecular imaging,and noxious gas sensing among other applications because of their simple preparation,good selectivity,and high stability.The high redox activity,excellent chemical stability and adjustable dimensions of polyoxometallates correspond to the miniaturization and speeding up of electrochemical biosensors.In this paper,polyoxometalates(POMs)were used as an active component combined with other active nano materials,including carbon nanotubes,ionic liquid,chitosan and copper nanoparticles.Two novel modified electrodes were successfully prepared by Lb L and their electrocatalytic activities toward L-tyrosine(Tyr)was studied.The surface morphology and elemental composition of the modified electrodes were detailed analyzed by scanning electron microscopy,energy dispersive X-ray spectroscopy,mapping,and X-ray photoelectron spectroscopy.The electrocatalytic properties of the two novel modified electrodes for the oxidation of Tyr were detailed analyzed by cyclic voltammetry,electrochemical impedance spectroscopy and ampere-hour current technique and so on.Besides,the feasibility of the modified electrodes for testing Tyr in real samples were further explored.The specific details are as follows:1.The Dawson-type POMs(P2Mo16V2)and ionic liquids(1-butyl-3-methylimidazolium bromide,BMIMBr)functionalized carbon nanotubes(CNTs)were modified on the indium tin oxide(ITO)glass electrode to construct a modified electrode ITO/(P2Mo16V2/BMIMBr-CNTs)8 for the catalytic oxidation of Tyr.The results of electrocatalytic tests showed that the catalytic oxidation of Tyr was significantly enhanced because of the good synergistic effect of P2Mo16V2 and BMIMBr-CNTs.The linear range and the detection limit to Tyr of ITO/(P2Mo16V2/BMIMBr-CNTs)8 electrochemical sensor were 1.795 × 10-7 M ~ 1.244 × 10-4 M and 1.0 × 10-7 M(signal to noise ratio of 3,S/N=3)in 0.1 M PBS(pH 6.8)with a sensitivity of 0.462 ?A/?M.In addition,the sensor had good selectivity for several common interfering substances in the potential of 0.48 V ~ 0.88 V.Preliminary real sample testing was studied using the proposed sensor,the recovery rates were within the error allowable range.2.The electrodes modified by PEI/(P2Mo16V2-CNTs/Cs-Cu)2 nanocomposite films were prepared by compounding Cu nanoparticles polymerized by Chitosan(Cs),carboxylated carbon nanotubes(CNTs)and Dawson-type POMs(P2Mo16V2)by Lb L method for detecting Tyr.Cyclic voltammetries showed that the double-layered composite film modified electrode had higher electrocatalytic efficiency for the oxidation of Tyr compared with the single-component electrode in 0.1M PBS(pH = 6.5).The experimental conditions were optimized including the pH of the buffer solution and the number of layers of the composite film.The electrocatalytic and sensitization performance of PEI/(P2Mo16V2-CNTs/Cs-Cu)2 were investigated under optimal experimental conditions.The results show that the linear range and the limit of detection of the modified electrode were 4.99 × 10-8 M ~ 6.88 × 10-5 M and 2.53 × 10-9 M(S/N=3),respectively.The reproducibility,selectivity and stability of the modified electrode were further investigated.The obtained electrode had good selectivity,reproducibility,stability,and excellent operation stability and service life.In addition,ITO/(P2Mo16V2-CNTs/Cs-Cu)2 was used to detect Tyr in human urine samples and the better recovery rate was obtained.