The Research Of Electrochemical Sensing Based On Carbon-based Composites To Detect Small Biological Molecules

The level of small biomolecules plays a vital role in controlling and early diagnosis of some diseases and genetic problems.Therefore,rapid and accurate detection of the small biomolecules is great significance for human health and clinical diagnosis.Compared with other detection methods,electrochemical method has some advantages such as high sensitivity,low detection limit,simple operation,miniaturization and low cost,etc..Therefore it has been widely developed and used to detect small biological molecules.In this work,two kinds of carbon-based materials were successfully designed and prepared,which3D-Ni@AC and MnO2-MWCNTs composites were used as modified electrode materials for construction novel electrochemical sensor.And it achieved the analysis toward small biological molecules about cysteine?CySH?,guanine?G?and adenine?A?.The main contents of this paper are as follows:1.Using NaCl as a template,firstly through one-step simple low-temperature drying process and calcination reaction,and then removing the template with deionized water,the three-dimensional porous and hierarchical3D-Ni@AC composites were successfully synthesized,which were used as the modified electrode material with a highly sensitive electrochemical catalytic activity for cysteine.The reason was that the 3D-Ni@AC composites were provided with the three-dimensional layer-by-layer interlaced interconnected porous carbon network by template method.This interconnected layered carbon structure could effectively increase stability,and the porous structure also provided the large specific surface areas,which could effectively penetrate the electrolyte and provide more active sites for electrochemical reactions.At the same time,Ni nanoparticles with uniform size and evenly dispersion on the carbon network enhanced conductivity and catalytic activity of the composites.The synergistic effects between rich-porous carbon network and Ni NPs exhibited excellent electrocatalytic ability for oxidation CySH and greatly improved the electrochemical response signal of CySH.In this paper,the electrode materials were optimized and selected.Under the optimal conditions,the electrochemical behavior and oxidation mechanism of CySH on 3D-Ni@AC/GCE were studied in alkaline environment by the cyclic voltammetry?CV?.It was shown that Ni NPs on the electrode surface were transformed Ni²⁺/Ni³⁺redox pairs under alkaline conditions and involved in the process of oxidation CySH,thereby indirectly promoting the oxidation of CySH and greatly improving the current response to CySH.Therefore,the electrochemical detection method for CySH was established.In 0.1 mol/L NaOH,the linear concentration range of CySH was 0.8-85?mol/L,and the detection limit?LOD?was 0.15?mol/L?S/N=3?.The sensor was successfully applied for detection CySH in urine and blood samples,and satisfactory recovery was obtained.It has been proved that it had good stability,reproducibility and anti-interference ability by a series of experiments,which demonstrated the sensor had a potential practical applications.2.By one-pot hydrothermal method the three-dimensional flower-like MnO2/MWCNTs composites were synthesized,which the two-dimensional MnO2nanosheets self-assembled to form three-dimensional nano-flowers and the one-dimensional carbon tube was evenly interspersed into the middle of the petals to form a unique three-dimensional layered flower-like hybrid materials.It achieved highly sensitive simultaneous electrochemical detection of guanine and adenine.Based on the unique three-dimensional flower-like structure of MnO2,there was more open space and larger specific surface area on the surface that was beneficial to increase electrolyte penetration and the contact area with the analytes.At the same time,the strong conductivity of MWCNTs was evenly interspersed in MnO2 nano-flowers.On the one hand,it prevented the carbon tube from self-aggregating,which effectively improved the material utilization rate.On the other hand,it accelerated the electron transfer,increasing the diffusion channels,and effectively improving the electron transfer capabilities between two analytes and the electrode.Therefore,the electrochemical response signals of the two targets were greatly improved,and the modified electrode exhibited excellent electrocatalytic ability.In the work,the electrochemical behavior of G and A was studied by differential pulse voltammetry?DPV?on MnO₂-MWCNTs/GCE.The effects of experimental conditions on the electrochemical signals and the mechanisms of G and A were investigated.The electrochemical reactions of G and A were irreversible oxidation process involving two electrons and two protons transfer,and were the adsorption-controlled process.The electrochemical detection method for G and A was established.In pH 5.0 PBS,the good linear concentration ranges was 0.02-155.0 and 0.02-162.0?mol/L for G and A,respectively.The LOD?S/N=3?was 0.016 and 0.011?mol/L,respectively.MnO2-MWCNTs/GCE had good reproducibility,stability and anti-interference.In addition,the prepared electrochemical sensor was successfully applied to detect the levels of G and A in blood and urine with a satisfactory result,indicating that the sensor could be applied in practical detection.