Surface Modification Of Carbon Nanotube For Designing Polymer Brush-type Composite Materials And Applications In Analysis And Detection

Electrochemical sensor is a detection strategy that combines electrochemical technology and sensor technology.It has received widespread attention because of its advantages such as high specificity,high sensitivity,low cost and short time-consuming.However,the low content of the target substance in the sample leads to the urgent need to expand the detection signal to improve the sensitivity of detection.With the gradual development of the field of analysis and detection,the construction of electrochemical sensors with high selectivity,high sensitivity and high stability has gradually become the research goal of researchers.Currently,the application of carbon nanomaterials to the construction of electrochemical sensors has been widely reported.Among them,multi-walled carbon nanotubes（MWCNTs）can effectively improve the conductivity,specific surface area and catalytic activity of the electrode.However,using MWCNTs alone as a carrier may be difficult to achieve the expected purpose of amplifying the detection signal.If MWCNTs are surface modified to design different composite materials,it provides an unexceptionable method for constructing ultra-sensitive electrochemical sensors.In this paper,based on polymer brush-based nanocomposites and molecularly imprinted hydrogels（MIHs）,three excellent sensors have been constructed for the detection of tumor markers,antibiotics and melamine.The content of the thesis is mainly divided into three parts.1.A new strategy that combines bioinspired polydopamine（PDA）chemistry and metal-free photoinduced electron transfer-atom transfer radical polymerization（PET-ATRP）was used to modify MWCNTs to design polymer brush-based nanocomposites.It is used to construct an electrochemical immunosensor（EI）for the high-sensitivity detection of carcinoembryonic antigen（CEA）and alpha-fetoprotein（AFP）.Firstly,the surface of MWCNTs was modified by PDA,which also provides an ideal platform for the high-efficiency initiatorɑ-bromophenylacetic acid（BPA）for bolting.Then,the organic dye eosin Y（EY）was used as a photoredox catalyst to form a controllable structure of polyglycidyl methacrylate（PGMA）around MWCNTs by using PET-ATRP technology.The epoxy group in PGMA and ethylenediamine（EDA）were covalently combined through a nucleophilic ring-opening reaction to obtain polymer brush-based nanocomposites EDA/PGMA-g-MWCNTs.Finally,signal molecules（anthraquinone-2-carboxylic acid（Aq）,ferrocene formate（Fc））and detection antibody（Ab2）are loaded on the surface to prepare an immunoprobe with signal amplification function.It is worth noting that the EI performed a wide detection range and a low detection limit of CEA（163 fg/m L-163 ng/m L,56.1 fg/m L）and AFP（100 fg/m L-100 ng/m L,32.8 fg/m L）,respectively.2.MIHs was constructed by using MWCNTs/polymer brush-based composite materials and molecular imprinting technology（MIT）,and used as the sensitive layer of electrochemical sensors to achieve highly sensitive detection of antibiotic cefixime（CEF）.Specifically,polymer brush based nanocomposites EDA/PGMA-g-MWCNTs acted as an enhanced conductive substrate.Au nanoparticles（Au NPs）and reduced graphene oxide（r GO）were modified on the surface of the glassy carbon electrode（GCE）by electrochemical deposition method to enhance the catalytic activity of the electrode against CEF.In order to improve the selectivity of the sensor,acrylic acid（AA）is used as the monomer,CEF is given as the template,and the in-situ polymerization method is used to polymerize around EDA/PGMA-g-MWCNTs.The MIHs film was prepared by drip coating method on the pretreated electrode surface,and the electrochemical sensor MIHs/r GO-Au NPs/GCE was obtained after template elution.Under the optimal experimental conditions,the CEF concentration has a good linear relationship in the range of 0.05μmol/L-600.0μmol/L,and the detection limit is 0.007μmol/L.This result implies that the sensor has good selectivity,stability and practicality.3.MIHs was constructed by using MWCNTs/polymer brush-based composites and MIT technology,and was used as the sensitive layer of the electrochemical sensor to realize the highly sensitive and specific detection of melamine（MA）.First,PDA encapsulation layer is formed on the surface of MWCNTs,which provides an ideal platform for the bolting of the high-efficiency initiator 2-bromoisobutyryl bromide（Bi BB）.Then,the organic dye rhodamine B was used as a photoredox catalyst to form a controlled structure of poly 4-vinylpyridine（P4VP）around MWCNTs by using PET-ATRP technology,which was used as the conductive substrate and reinforcement MWCNTs@PDA@P4VP.Meanwhile,in order to enhance the selectivity of the electrode,AA was used as the monomer and MA as the template,and the in-situ polymerization method was used to polymerize around MWCNTs@PDA@P4VP.Finally,an electrochemical sensor was prepared by dropping the polymer onto the surface of the pre-treated electrode by the drip coating method.Compared with other analogs,the sensor exhibits a higher affinity for MA,with a detection range of 1×10^-10mol/L-1×10^-6 mol/L and a detection limit of 5.72×10^-11 mol/L.