Preparation Of Highly Active Nanoporous Membrane Modified Electrode And Application Of Antifouling And Highly Sensitive Detection Of Complex Samples

Electrochemical sensor has been widely used in analysis and detection because of its high sensitivity,good portability and sensitive detection in complex environment.Among them,the accuracy,stability and high sensitivity of the sensor are the premise of obtaining satisfactory analytical performance.However,in the actual sample detection,the sensor electricity is easy to be contaminated by macromolecular substances or other interferences,thus reducing the detection sensitivity of the electrode.Therefore,the use of anti-fouling functional materials to modify the sensor electrode is a common strategy to improve its anti-fouling performance.For example,the electrode surface modified porous coating,zwitterionic polymer,self-assembly layer materials,etc.,to play the anti-fouling role while improving the sensor’s detection sensitivity,stability and a series of properties.As one of the porous coating materials,vertically-ordered mesoporous silica-nanochannel film（VMSF）have attracted extensive attention in recent years due to their remarkable antifouling ability.The charge-selective permeability of VMSF（there are a large number of silicon hydroxyl groups in the pore,and their p K_a～2 is electronegative in the solution with appropriate p H value,so it can enrich the active small molecules with positive electroegativity through electrostatic interaction,and reject the electronegative substances）,the size exclusion effect（the pore size is 2-3 nm,and the porosity is high,Therefore,macromolecular materials can be blocked out,and analyte smaller than the pore size can reach the electrode surface successfully）,hydrophilicity（the micellar template or hydrophobic group inside the pore can be hydrophobic,after removing the micellar template,a large amount of silicon hydroxyl group is exposed,and the pore is hydrophilic）,and a series of characteristics,such as large specific surface area and easy modification of the pore,make it a popular nanomaterials.In addition,VMSF can also be modified on different substrate electrodes,such as three-dimensional materials,carbon-based electrodes or noble metal electrodes.This paper introduces a method to construct a highly sensitive electrochemical sensor based on the integration of VMSF with high-active carbon-based electrode or modification of its nanocapsy-limited functional nanomaterials.By electrochemical pretreatment of the carbon-based electrode or modification of the nanocapsy-limited functional nanomaterials in the functional group modification of the VMSF nanocapsy-limited functional nanomaterials.A high performance VMSF-modified carbon-based electrode was constructed.Combined with the significant antifouling performance of VMSF and the enrichment of small active substances,the rapid and highly sensitive electrochemical detection of electroactive small molecule targets in environmental,food,biological and other complex samples was realized.The details are as follows:（1）A 3D electrochemical sensing platform based on pre-activated 3D graphene electrode（p-3DG）integrated with VMSF was established to sensitively detect 2,4,6-trichlorophenol TCP and prochloraz in food samples through the anti-fouling ability of VMSF and the enrichment of TCP.p-3DG electrode with high active area and excellent electrocatalytic performance was obtained by two-step electrochemical polarization（organic phase anodic oxidation and aqueous phase cathode reduction）.Electrochemically assisted self-assembly（EASA）method was used to rapidly grow VMSF on p-3DG surface and to stabilize adhesion.Based on the high electrocatalytic activity of p-3DG and the significant enrichment ability of VMSF channel through hydrogen bonding,the highly sensitive electrochemical detection of TCP was realized.Compared with 2D electrodes modified by p-3DG and VMSF,the sensor has a wider linear range and lower detection limit（LOD）.The electrochemical response of TCP is not affected by coexistence model interferors（protein,surfactant,humic acid）,which confirms that VMSF/p-3DG sensor has high anti-fouling detection ability.In addition,because TCP is a metabolite of the bactericidal pesticide imidamine,the sensor can also be used for indirect determination of prochloraz in vegetable and fruit samples with appropriate sample pretreatment methods.（2）An electrochemical sensor based on VMSF and nano-carbon composite modified glassy carbon electrode（GCE）was developed for the sensitive and rapid detection of pesticide paraquat（PQ）.The 3D structure reduced graphene oxide（GO）and carbon nanotube（3DG-CNT）composite films were prepared on the surface of GCE by electrochemical method,and then VMSF was prepared on the surface of 3DG-CNT/GCE by EASA method.The successful preparation of the composite was demonstrated by X-ray photoelectron spectroscopy（XPS）,and the electroactive area of VMSF/3DG-CNT/GCE was calculated by Randles-Sevcik formula.The integrity of the VMSF morphology was demonstrated by transmission electron microscopy（TEM）and electrochemical methods.The obtained 3DG-CNT nanocomposites have a three-dimensional network structure and a large electroactive area,which promotes the electron transfer between PQ and the bottom electrode,and the abundant oxygen-containing groups on the surface provide a suitable microenvironment for the stable growth of VMSF.The electrocatalytic ability of 3DG-CNT combined with the electrostatic enrichment ability of VMSF makes VMSF/3DG-CNT/GCE have higher analytical sensitivity.In addition,the excellent anti-fouling capability of the VMSF makes the prepared sensor show satisfactory performance in the direct analysis of PQ in environmental water samples.（3）An electrochemical method for the determination of norepinephrine（NE）was established by in situ deposition of gold nanoparticles（Au NPs）modified amino-functionalized VMSF（NH₂-VMSF）on a pre-activated glassy carbon electrode（p-GCE）.p-GCE was prepared by electrochemical pretreatment with two-step polarization method.NH₂-VMSF was grown on the p-GCE by EASA method.Au NPs were deposited in situ on NH₂-VMSF/GCE using amino group as anchor site in the nanochannel,and the target electrode Au NPs@NH₂-VMSF/GCE was obtained.The integrity of NH₂-VMSF films and the successful scoping of Au NPs in VMSF nanochannels were demonstrated by scanning electron microscopy（SEM）and electrochemical methods.Based on Au NPs and p-GCE substrates for NE electrocatalysis and NH₂-VMSF for NE enrichment,the sensor realizes highly sensitive detection of NE at n M level.In addition,the sensor has good potential resolution and is easy to regenerate and reuse.Combined with excellent anti-fouling ability of the NH₂-VMSF,the direct electrical analysis of NE in human whole blood samples was realized.