The Research Of Electrochemical Biosensor Based On Ordered Mesoporous Carbons And Its Application On The Detection Of Organic Pollutants

Ordered mesoporous carbons (OMCs) are one kind of silicon-based mesoporousmaterial. OMCs have big surface area as large as to2500cm2/g, large pore-volume upto2.25cm3/g and ordered arrangement channel structure. Therein, it has been widelyused in adsorption, catalyst support, electrode modified material, energy storage andsome other fields. OMCs can obviously improve the biological compatibility andelectrochemical activity of the modified electrodes when used as electrode modifiedmaterial. In this paper, OMCs was modified on glass carbon electrode and applyingon the detection of nitrophenol isomers and p-nitrophenyl organophosphorus (OPs),and also used to detection coefficient of phenol. OPH-bacteria was modified on theelectrode and used to determination OPs pesticide. The work mainly included thefollowing four sections:First, an OMCs modified glass carbon electrode (OMCs/GCE) was developed tostudy the electrochemical behavior of nitrophenol isomers and their reactionmechanism. Compared with bare GCE, the OMCs/GCE exhibited enhancedelectrocatalytic activity towards nitrophenol isomers. At OMCs/GCE, the threenitrophenol isomers could be identified and separated successfully and thesimultaneous determination was realized by detecting the reduction peaks of theirintermediate products with differential pulse voltammetry (DPV), i.e. p-nitrophenol(p-NP) at0.209V, m-nitrophenol (m-NP) at0.020V and o-nitrophenol (o-NP)) at-0.201V. Under the optimized experimental conditions, the linear ranges of thecalibration curves were2-90μmol/L for p-NP,1-100μmol/L for m-NP and0.5-90μmol/L for o-NP. In addition, the limit of detections of p-NP, m-NP and o-NP were0.1,0.06and0.08μmol/L, respectively (S/N=3). After experimental verification, it turnout that this electrochemical sensor could be applicable for the determination of real samples, which holds great potential in the marine monitoring system and otherin-situ detection.Second, the p-NP and p-methylphenol were selected as two models ofelectron-withdrawing and electron-donating groups to investigate the electrochemicalbehavior of phenols and explore their electrooxidation mechanism at OMCs/GCE.The acidity coefficient (pKa) of phenols were collected from the related reports andthe oxidation potential (Epa) of phenols at OMCs/GCE were tested by DPV. Based onthe relationship between pKaand Epa, a simple and novel method was proposed for thefirst time to calculate the pKaprecisely of some uncommon p-substituted ando-substituted phenols on the basis of measured Epawith voltammetry at OMCs/GCE.Several common substituted phenols were tested to prove the feasibility of thismethod for the precise calculation of the pKa. In addition, utilizing the substituenteffect, the simultaneous detection of p-substituted phenols (or o-substituted phenols)in mixture can be realized at OMCs/GCE if the difference of the nearby Epavalueswere large enough.Third, an electrochemical sensor based on OMCs/GCE for the ultrasenstivedetermination of p-nitrophenyl OPs was developed. Take paraoxon as an example, theelectrochemical behavior and the reaction mechanism of p-nitrophenyl OPs atOMCs/GCE were discussed. The experimental conditions such as pH,preconcentration potential and preconcentration time were optimized. By using DPVtechnique, the OMCs/GCE can be used to detect trace p-nitrophenyl OPs includingparaoxon, parathion and methyl parathion without deoxygenization condition, whichwas convenient for the detection of real samples in-situ, such as sea water andsewage.Finally, the OPH-bacterium with high activity was modified on the surface ofOMCs/GCE directly without further time-consuming enzyme-extraction andpurification which greatly improved the stability of the enzyme. By detection theoxidation current of p-NP which was the hydrolysis product of p-nitrophenyl OPs, therapid monitoring of p-nitrophenyl OPs was realized. Under the optimizedexperimental condition, at OPH-bacteria/OMCs/GCE, the current response was linear with paraoxon concentration in0.05-25μmol/L, linear range of0.05-25μmol/L forparathion, and0.08-30μmol/L for methyl parathion. The low limits of detection wereevaluated to be9.0nmol/L for paraoxon,10nmol/L for parathion and15nmol/L formethyl parathion (S/N=3). The proposed microbial biosensor was well-suit formeeting the challenges of on-situ detection.