Integration Of Modified Carbonaceous Electrodes With Silica Isoporous Membrane For The Preparation Of High-performance Electrochemical Sensors

Direct,rapid,and sensitive detection of drugs and biomarkers in complex biological samples is essential for clinical diagnosis,health monitoring and treatment assessment.The electrochemical detection method has become one of the important methods for analysis due to its easy operation,low cost,fast and high efficiency.However,sensing electrodes in complex matrices were susceptible to contamination by biomolecules and interference from coexisting electroactive substances.Recent studies have shown that electrochemical sensors based on silica isoporous membranes(also named vertically-ordered mesoporous silica-nanochannel film,VMSF)have excellent anti-fouling and anti-interference performance,which allowed direct analysis in complex samples.Carbonaceous electrodes are the basic electrodes widely used for electrochemical sensing due to high chemical stability,low cost,wide potential windows and large variety.This thesis explored three simple and effective methods to modify carbonaceous electrodes,which not only improved the electrochemical activity of carbonaceous electrodes,but also realized the stable integration of VMSF with modified carbonaceous electrodes.Based on the high electrochemical activity of the modified carbonaceous electrodes and the excellent anti-fouling and anti-interference properties of VMSF,the VMSF-based sensors were able to analyze drug molecules and biomarkers in complex samples directly with high sensitivity.(1)Reduced graphene oxide(rGO)sheets could be employed as the conductive adhesive and electroactive layer for the fabrication of stable and sensitive VMSF-based sensor(VMSF/rGO/GCE).rGO was prepared by chemical reduction method.The successful preparation of rGO was verified by UV-Vis absorption spectra and X-ray photoelectron spectroscopy(XPS).VMSF was prepared on the rGO/GCE by using the electrochemically assisted self-assembly(EASA)method.Transmission electron microscopy(TEM)proved that VMSF channels were highly ordered with a pore size of 2.7 nm.Electrochemical characterization showed that the as-prepared VMSF on the rGO/GCE was intact and nearly defect-free.rGO has affinity towards electroactive small organic molecules through ?-? interaction and exhibits electrocatalytic effects,which endowed VMSF/rGO/GCE with high electrochemical activity and good potential resolution.Combining the excellent anti-fouling and anti-interference capabilities of VMSF,the VMSF/rGO/GCE sensor was able to analyze acetaminophen(APAP),norepinephrine(NE),guanine(G)and tryptophan(Try)in serum directly with high sensitivity.(2)Through a simple electrochemical activation of GCE(p-GCE),VMSF could be prepared on p-GCE(VMSF/p-GCE)stably without introducing an adhesive layer.XPS and electrochemical characterization proved that electro-activation could introduce abundant oxygen-containing groups on the electrode surface.VMSF was stably prepared on p-GCE by EASA method.TEM showed that VMSF channels were highly ordered with a pore size of 2.7 nm and a thickness of about 110 nm.Based on the excellent electrochemical and electrocatalytic activity of p-GCE and the enrichment effect of nanochannels,VMSF/p-GCE showed significantly improved electrochemical performance and potential resolution on four typical electroactive small biomolecules(dopamine,uric acid,NE and Trp).Combining the anti-fouling and anti-interference capabilities of VMSF,VMSF/p-GCE could effectively reduce the effects of complex matrix and detect dopamine in serum with high sensitivity directly.(3)Three-dimensional graphene(3DG)was used as substrate electrode for the fabrication of stable and high-performance VMSF-based sensor(VMSF/pl-3DG).3DG electrode was treated by the simple and environmentally friendly air plasma to obtain the surface modified 3DG electrode(pl-3DG).The contact angle and electrochemical(CV)characterization confirmed that plasma treatment can improve the wettability of pl-3DG effectively,and then improve its electrochemical activity significantly.VMSF was stably prepared on pl-3DG electrode by EASA method.SEM showed that VMSF was modified on the surface of pl-3DG successfully.TEM proved that VMSF channels were highly ordered with a pore size of 2.7 nm.Electrochemical characterization verified that the as-prepared VMSF on pl-3DG electrode was intact.Based on the high electrochemical activity and large surface area of pl-3DG electrode,VMSF/pl-3DG electrode had high sensitivity for UA detection.Combining the anti-fouling and anti-interference properties of VMSF,VMSF/pl-3DG electrode could be used for the direct detection of UA in serum.