Application Of MXene Or Carbon Nanotube-supported MOFs Composites In Electrochemical Sensing

Metal Organic Frameworks（MOFs）,a kind of porous materials,are usually composed of metal ions and organic ligands.MOFs have unsaturated metal sites,which make them have excellent catalytic ability.The high porosity and large surface area of MOFs are conducive to the adsorption of analytes,thus amplifying the detection signal.These excellent properties make them a good electrode modification materials in the field of electrochemical sensing.However,the large number of organic ligands in MOFs limit the electrical conductivity of materials.Assembling MOFs with carbon nanomaterials with good conductivity can compensate for this defect.MXene is a new type of two-dimensional nanomaterial,which is a general name of transition metal carbide,nitride and carbon nitride.It has outstanding electrical conductivity and hydrophilicity.MXene hybridize with other materials easily by adjusting surface functional groups.Carbon nanotubes（CNTs）are one-dimensional carbon nanomaterials with remarkable electrical conductivity.In this paper,MOFs were loaded on MXene or CNTs to prepare nanocomposites.Due to the synergistic effect,the prepared composites had excellent electrical conductivity and good electrocatalysis.These nanoprobes were applied to the field of electrochemical sensing.The main content of this paper were divided into the following three parts:Part one:In-situ growth of cerium-based metal organic framework on multi-walled carbon nanotubes for electrochemical detection of gallic acidGallic acid（GA）is a kind of polyphenol compound,which is beneficial to human body.GA has strong antioxidant effects and biological characteristics such as anti-inflammatory,antihistamine,anti-tumor,free radical scavenging,and cardiovascular disease protection.Therefore,accurate and rapid determination of GA is of great significance to human health.CeMOF/MWCNTs composite materials were prepared by in-situ growth of CeMOF on multi walled carbon nanotubes（MWCNTs）.Under optimized conditions,the linear range of the sensor for detecting GA was 1.5μM-200μM,the limit of detection was 0.14μM and the sensor had high reproducibility,stability and anti-interference.The sensor prepared in this work had been successfully applied to the detection of gallic acid in tea,and had great recovery.Part two:MXene/UiO-66-NH₂electrochemical sensor for detecting uric acidUric acid（UA）is the final product of purine nucleotide metabolism,and it is a biologically active compound in the human body.Gout,hyperuricemia,diabetes and other diseases can be diagnosed by the content of UA.In this experiment,MXene/UiO-66-NH₂nanocomposites were prepared and modified on a glassy carbon electrode for the detection of UA.MXene is a good platform for loading MOFs because of its large specific surface area and rich active sites.The electrochemical behavior of MXene/UiO-66-NH₂/GCE was studied.The linear range of the prepared sensor for detecting UA was 0.7μM-244.8μM.The detection limit was 0.53μM.In addition,MXene/UiO-66-NH₂/GCE detected UA in serum samples with good recovery rate,which verifies the practicality of the electrochemical sensor.Part three:MXene/CNTs/Cu-MOF electrochemical probe for detecting tyrosineTyrosine is a precursor of some neurotransmitters such as thyroxine and dopamine.It has the function of regulating emotions and stimulating the nervous system.The change of level of tyrosine in the human body is related to certain diseases.Thus,it is necessary to develop a new type of tyrosine sensor.This article inserts CNTs into MXene layers,which not only prevented layered MXene nanosheets from stacking again,but also linked individual MXene sheets to construct interconnected conductive channels.The loading of CuMOF on MXene/CNTs further improved the catalytic performance of the composite material and its ability to adsorb analytes.This study developed an enzyme free electrochemical sensor based on MXene/CNTs/CuMOF composite material for detecting tyrosine.Under the optimal detection conditions,the sensor had a good linear relationship for the detection of tyrosine in the concentration range of 0.53μM to 232.46μM and the limit of detection was 0.19μM.The sensor could be used to detect tyrosine in human serum samples.