Application Of Different Signal Response Strategies In Electrochemical Sensors

The identification,testing and analysis of specific targets play a vital role in the fields of agricultural production,food safety,environmental science and medical treatment.The development of new sensors with high sensitivity,good selectivity,simple preparation,convenient operation,low toxicity,and even non-toxicity has become a research hotspot in the research field.Up to now,the analytical tools commonly used in the field of analysis mainly depend on chromatographic analysis,such as P-GC-MS,LC-ESI-MS,UHPLC-MS/MS and SPE-UPLC-MS.Although these methods hold higher accuracy and sensitivity for quantifying target,they involve complex sample preparation,toxic organic agents,higher analytical costs,time-consuming and difficult to handle,which limits the widespread use of such technologies.In contrast,electrochemical sensors are widely studied for their simple operation,low cost and miniaturization.However,due to the complexity of electronic transmission path and the instability of electrode surface materials,the test data is not accurate and sensitive,which puts new requirements on electrochemical sensing technology.At present,aiming at the problems of electrochemical sensors,it is a good solution that choosing the components with high selectivity,conductivity and adsorption effect for the modification of the sensor or making use of its advantages in the field of life science to expand the application of the electrochemical sensor.At the same time,the development of nanotechnology and biotechnology provides a new perspective for the construction of new electrochemical sensors.Based on this,this paper designs two schemes:1.Experimental and theoretical studies of a novel electrochemical sensor based on molecularly imprinted polymer and B,N,F-CQDs/AgNPs in ultra-trace bisphenol S determinationIn this work,three doped carbon quantum dots(B,N,F-CQDs)and silver nanoparticles(AgNPs)with high conductivity and excellent catalytic performance were successfully synthesized by microwave pyrolysis method and electrodeposition method respectively,and they were used as electrode modification materials to improve the detection performance of the electrode.Then,the molecularly imprinted polymer(MIP)with high selectivity was coated on the composite modified electrode by electropolymerization,wherein bisphenol S(BPS)was utilized as the template molecule and pyrrole was applied as the functional monomer.The surface morphology of the MIP was characterized by means of calculation,scanning electron microscopy(SEM),atomic force microscopy(AFM).The thickness and roughness of MIP respectively was 136 nm and 4.89 nm.And it can be seen from the SEM spectrum that MIP contains many cavities with uniform pore size,which were beneficial to the recognition of BPS.And,the step-by-step fabrication process and the adsorption capacity of the modified electrode were evaluated by cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS)and chronocoulometry(CC).The results indicated that the synergy between B,N,F-CQDs and AgNPs dramatically improved the sensitivity of the electrode and achieved the amplification of the electrical signal.Meanwhile,the electrochemical activities of BPS were explored by CV and differential pulse voltammetry(DPV).And,the various parameters relating to the electrochemical kinetic properties of BPS were calculated.To the best of our knowledge,this was rarely reported in peer journals.The MIP remarkably improved the selectivity of the sensor owing to the specific recognition of the imprinted cavities.The linear response range of the new sensor was 0.1 to 0.01?M with a detection limit of 0.011?M and the electrode designed in this paper could meet the requirement of trace-level measurement of BPS in biological and environmental samples.Additionally,the sensor was used to determine BPS in plastic products with good anti-interference and acceptable recovery.2.Label-free electrochemical biosensor for ultrasensitive and selective DNA detection based on coupling exonuclease ?-assisted target recycling and hybridization chain reaction amplificationIn this work,a fast and sensitive electrochemical biosensor was developed for the detection of specific sequences of DNA by combining the amplification strategy of coupling exonuclease?-assisted target recycling and hybridization chain reaction(HCR).EIS and CV were employed to characterize the fixation of the capture probe(C-DNA),the capture of the target chain(T-DNA),the shear action of the exonuclease ?(EXO ?)and HCR.Experimental results showed that in the presence of the T-DNA,C-DNA can be paired with it to form rigid double-stranded DNA(dsDNA),and the process could trigger the catalytic hydrolysis of the EXO ?.Meanwhile,under the shearing action of EXO ?,dsDNA was continuously formed and destroyed resulting in the release of a large number of nucleic acid sequence fragments on the electrode surface,which can induce HCR.The occurrence of HCR process led to the formation of a plenty of double-stranded hybrid DNA polymers,which would adsorb more electroactive substances(methine blue)and thereby achieving double amplification of the detection signal,greatly improving the detection performance of the electrode.In addition,the feasibility of the designed scheme was characterized by DPV.The electrical signal of the electrode was 78 times of the background current,indicating that the signal amplification strategy envisaged in this work was feasible and the sensitivity of the electrode was greatly improved.Under the optimal conditions,the electrochemical biosensor constructed had a wider linear detection range,spanning five orders of magnitude,ranging from 20 nM to 1 pM and the lower detection limit as low as 3.8 pM.In addition,the anti-interference test showed that the sensor proposed in this experiment possessed excellent selectivity and could clearly distinguish among single-base mismatch sequences,double-base mismatch sequences,three-base mismatch sequences and full base mismatch sequences.