| Electrochemical sensors have become an important part of analytical methods due to their portability,low cost,high sensitivity,and fast response time.However,ordinary electrode materials cannot meet the ever-increasing detection requirements and complex detection environments,so there is an urgent need to develop electrode modification materials with excellent performance and sensitive electrochemical sensors.Among them,smart polymers with excellent thermosensitive performance and cyclodextrin and its derivative materials with excellent enrichment performance stand out and become one of the important materials for a new generation of functional electrochemical sensors.In this paper,a new type of sensitive electrochemical sensor was constructed based on two advanced nanomaterials and used for the detection of actual samples.These sensors have enriched the application of these two materials in the field of electrochemical sensing,developed a new electrochemical sensing system for phenolic compounds,and provided theoretical support for the electrochemical behavior of phenolic compounds.1.A novel self-protection sensor was successfully constructed based on an interesting thermosensitive triblock polymer poly(styrene-b-(N-isopropylacrylamide)-b-styrene)(PS-PNIPAm-PS).At low temperatures(<24?),the analyte was able to undergo the redox process at the modified electrode.However,the polymer shrunk and accumulated at high temperatures(>30?),which dramatically increased the electron transfer resistance(Rct)of the modified electrode and consequently blocked the occurrence of the redox reaction to protect the electrode from high temperatures and enhance its stability.Under optimized conditions,the proposed sensor showed a good detection range for hydroquinone(6×10-7-2.35×10-3 M)and a low limit of detection(LOD)(4.9×10-7 M).The sensor was also successfully applied for detecting hydroquinone in real samples.2.A temperature-controlled switchable electrochemical sensor was constructed based on a composite film consisting of thermosensitive block polymer PS-PNIPAm-PS,carboxylated multi-walled carbon nanotubes(MWCNTs-COOH)and amino-functionalized graphene quantum dots(N-GQDs).The prepared sensor showed good temperature sensitivity and reversibility in sensing paracetamol.In the low temperature environment,the polymer stretched to bury the electroactive sites of the carbon nanocomposite,and the paracetamol could not pass through the polymer to achieve electronic exchange,representing the"closed"state.Conversely,in the high temperature environment,the polymer shrank to expose the electroactive sites and enlarge background currents,the paracetamol was able to undergo the redox reaction normally and generate the response current,representing the"on"state.In addition,the sensor had a wide detection range(1×10-7-7.0×10-6 M and 7.0×10-6-1.03×10-4M)and a low LOD of 6.6×10-8 M for paracetamol.This switch-like sensor provided a novel idea for the application of thermosensitive polymers.3.An electrochemical dopamine sensor with a temperature-controlled switch was constructed by using a mixture of thermo-sensitive block copolymer poly(tert-butyl acrylate)-b-(N,N-diethylacrylamide)-b-(tert-butyl acrylate)(t BA-PDEA-t BA),graphene oxide(GO)and multi-walled carbon nanotubes(MWCNTs).If the temperature is below 26?,the polymer on the glassy carbon electrode(GCE)is stretched,the charge transfer resistance(Rct)of the composite is large.In the presence of dopamine,the electron transfer at electrode is strongly retarded and in the"off"state.At above 38?,the polymer is shrunk and the value for Rct is much smaller.The presence of dopamine results in a rapid electron transfer at the GCE,and this is referred to as the"on"state.At temperatures between 26?and 38?,the polymer shrinks slightly and has a"spring-like"state.There is a linear relationship between the response current and temperature.The response to dopamine is linear in the 6×10-8-4.2×10-6M and 4.2×10-6-1.82×10-5 M concentration range,and the LOD is 4.2×10-8 M.4.An electrochemical quercetin sensor was constructed based on molybdenum disulfide-carbon nanotube@graphene oxide nanoribbons(Mo S2-CNTs@GONRs)/thiol-?-cyclodextrin(HS-CD)/aminated graphene quantum dots(N-GQDs).Portions of MWCNTs were unzipped to form CNTs@GONRs,and Mo S2 was successfully grown on it to form composites Mo S2-CNTs@GONRs.Under optimized conditions,the proposed sensor had an excellent detection performance for quercetin with a wide linear range from 2×10-9-6×10-7 M and 6×10-7-1.6×10-6 M,and a lower LOD of8.2×10-10?M.The sensor also exhibited satisfactory stability and accuracy for Que detection in actual samples(juice and honey).5.A novel ultra-sensitive adsorption-type signal-amplified electrochemical sensing interface has been proposed and applied for the determination of baicalin which is a bioactive flavonoid wildly used in pharmaceuticals and cosmetics.The sensing interface is constructed by graphitized carbon nitride-single-wall carbon nanotube nanocomposite materials(C3N4-SWCNTs),reduced graphene oxide(r GO),and electrodeposited cyclodextrin-metal organic framework(CD-MOF).The redox process of baicalin on the sensor involves the transfer of two protons and two electrons,and reactive sites have been revealed by density functional theory calculation.Under the optimal conditions,the sensor had an excellent detection performance for baicalin with a wide linear range from 1×10-9-3×10-7 M and 3×10-7-5×10-7 M,LOD of 4.6×10-10 M and sensitivity of 220?A/?M.This sensing interface has been applied for monitoring Bn in real samples such as human serum and bear bile scutellaria eye drops. |
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