Construction And Application Of New Electrochemical Sensor Based On Graphene-like Composites

Since the advent of graphene,it has received a lot of attention.Graphene has excellent electrochemical properties and widely used in the field of electrochemistry.In this paper,GO sponge structure and graphene-like structure of titanium carbide were used to modify the electrode respectively,to construct two electrochemical adapter sensor and an electrochemical DNA sensor for the detection of ochratoxin A,aflatoxin B1 and helicobacter pylori.The details are as follows:1.To enhance the sensitivity of an aptasensor,a novel strategy was designed to develop an electrochemical aptasensor based on poly?3,4-ethylenedioxy thiophene?–gold nanoflower?PEDOT–AuNFs?composites supported on a three-dimensional graphene oxide sponge?GOS?.GOS with a three-dimensional spongelike porous structure,exhibiting excellent electrical conductivity and a large surface area,provided the first amplification of the electrochemical signal for ochratoxin A?OTA?detection.PEDOT–AuNFs,synthesized by an ionic liquid-assisted one-pot method,presented a peculiar hierarchical flower-like structure,a high electroactive surface area,and more binding sites for immobilizing the aptamer molecules by the Au–S bonds.When PEDOT–AuNFs were supported on the surface of GOS by the interaction of the?–?packing between PEDOT and graphene oxide,a synergistic effect was produced to provide the second amplification for the aptasensor.PEDOT–AuNFs/GOS provided an ultrasensitive detection technique by multiple signal amplification for the electrochemical sensing of OTA.Consequently,this strategy not only endowed the aptasensor with high sensitivity but also needed no complicated signal amplification.The electrochemical sensor was fabricated successfully on a glassy carbon electrode to detect OTA with a linear response in the range of 0.01–20 ng/L and a limit of detection of 4.9 pg/L.Moreover,it displayed good specificity,reproducibility and stability.The utilization of the proposed aptasensor for the quantitative determination of OTA in wine indicates that it can find promising applications in detecting OTA and even other mycotoxins in foodstuffs.2.In this work,a simple and novel strategy is designed to develop a sensitive electrochemical aptasensor based on hydroxylated titanium carbide?HO-Ti₃C₂?being modified on the bare glassy carbon electrode?GCE?.The sheet-like structure and large surface area of HO-Ti₃C₂ provides a large number of active sites for aminated aptamer?NH₂-aptamers?.The strong hydrogen bonds between HO-Ti₃C₂ and?NH₂-aptamers?ensure the immobilization of aptamers on the surface of HO-Ti₃C₂.It is remarkable that the excellent electronic conductivity of HO-Ti₃C₂ enhances greatly the electron transfer which is crucial for the sensitivity of the sensor.Consequently,this system need not complex composites and complicated signal amplification process to improve the performance of the sensor,while it gives the aptasensor a high sensitivity.Herein,the as-designed aptamer/HO-Ti₃C₂/GCE aptasensor provides a sensitive detection technique for electrochemical sensing of Aflatoxin B1?AFB1?,with a liner response in the range of 0.01 to 90 ng/m L and a detection limit of 1.9 pg/m L.Also it displays good specificity,reproducibility and stability and is applied successfully to determine AFB1 in the real sample.The facile strategy may have great potential applications for designing other electrochemical aptasensors.3.In this work,an electrochemical DNA sensor with simple sandwich structure was designed to detect the oligonucleotide sequence associated with Helicobacter pylori based on Ti₃C₂T_x and AuNPs.The capture probe?cpDNA?modified by sulfhydryl group was covalently fixed on the Ti₃C₂Tx-Au electrode and hybridized with target DNA sequence?t DNA?and rpDNA to form sandwich structure.The sandwich structure can increase the amplitude of current signal effectively.In addition,the large specific surface area and extremely high conductivity of Ti₃C₂T_x after DMSO delamination could effectively promote electron transfer,thus greatly improving the sensitivity of the electrochemical DNA sensor.The AuNPs worked as an effective carrier to increase the amount and firmness of cpDNA through the firm binding of Au-SH bond.The electrochemical DNA sensor has the following advantages:1.Simple structure and easy operation.Only a sandwich structure is used for signal amplification.2.Rapid detection,high sensitivity,good selectivity,can achieve accurate detection of target DNA.Under optimal conditions,the developed electrochemical DNA sensor showed a wide linear range from 10^-11 M to 10^-14 M and a low detection limit of1.6×10^-1616 M and exhibited good sensitivity,reproducibility and stability.