Synthesis And Electrochemical Biosensing Applications Of Several Heteroatomic-rich COFs

Covalent organic frameworks（COFs）,a new class of porous crystalline materials,have wide applications in the many areas including gas adsorption and separation,energy storage,drug delivery,catalysis,and electrochemistry.Electrochemical sensing has received particular interest in biological analysis owing to its benefits,such as quick analysis speed,high accuracy and sensitivity,portaility,and economy.Based on the good crystallization,high stability,big specific surface area,and excellent electrochemical characteristics of COFs,some COFs with different heteroatoms were successfully synthesized in this thesis,and their applications in bioelectrochemical analysis were investigated.The addition of heteroatoms enhances electrochemical activities of the COFs and strengthens the interaction between the COFs and the target molecules,which remarkably boosts the specific identification and detection sensitivity of the resulted sensors toward the target molecule.The addition of heteroatoms improves the electrochemical activity of COFs,encourages contact between COFs and target molecules,and increases the particular identification ability and detection sensitivity of target molecules.The thesis consists of three parts as follows:（1）An imide Br-COF material containing Br atoms was synthesized by condensing the monomers 2,5-dibromobenzen-1,4-diformaldehyde（DBTA）and 2,4,6-tri（4-aminophenyl）-1,3,5-triazine（TAPT）.By combining it with carboxylated multi-walled carbon nanotubes（MWCNTs）and lanthanum oxide（La₂O₃）,a highly sensitive electrochemical sensor for the simultaneous detection of dopamine（DA）and uric acid（UA）was constructed with wide linear ranges（0.8～450μM）and low detection limits（0.050μM and 0.091μM）.The constructed sensor has been successfully used to determine quickly DA and UA in human urine and dopamine injection samples.（2）An O atom-rich COF,TFAB-COF,was in situ grown on polyaniline（PANI）by using 2,4,6-tri-（4-formylphenoxy）-1,3,5-triazine（TFPOT）and p-aminobenzoyl hydrazide（ABH）as monomers and the obtained hybrid was used to construct a sensitive electrochemical sensor for sulfamethoxazole（SMX）detection.Synergistic effect between highly conductive PANI and large surface area of TFAB-COF significantly amplifies electrochemical response signal of SMX.As a result,the constructed sensor was successfully employed for sensitive sulfamethoxazole analysis in environmental water samples with a wide linear range of 1～450μM and low detection limit of 0.107μM（S/N=3）.（3）A nitrogen-rich and conductive semiconductor-type COF,TQBQ-COF,was produced by a one-pot reaction between tetraaminobenzoquinone（TABQ）and cyclohexanone（TQ）.And then,without additional conductive additives,a sensitive electrochemical sensor was prepared for simultaneous determination of guanine（G）and adenine（A）.TQBQ-COF was anticipated to be employed in electrochemical applications of COFs because of its excellent conductivity and uniform pore structure.The sensor had not only low detection limits（0.061μM and 0.088μM）but also wide linear ranges（0.9～120μM）for G and A besides outstanding repeatability,reproducibility,and stability.In addition,it has been successfully applied to determine contents of guanine and adenine in herring sperm DNA samples.Due to good electric conductivity and regular pore structure,the synthesized TQBQ-COF has an important application protential in electrochemistry.