Modified Cellulose Nanofibers And Their Study In Catechol Biosensor

In recent years, catechol has aroused great attention due to their toxicities. Compared with the traditional detecting methods, biosensors have received increasing attention because of their high selectivity, high sensitivity, simplicity, reliability and rapid online monitoring character. Electrospun nanofibrous mats with three dimensional structure not only possessed high specific surface area, high porosity, the low hindrance of mass transfer and flexibility, also could be functionalized through the surface modification. Therefore, electrospun nanofibers could significantly improve the biosensing performance of biosensors and have a great potential application in biosensors. The study managed to fabricate laccase (Lac) biosensors based on modified cellulose nanofibers for the detection of catechol, did researches on the electrochemical properties of biosenosrs based on hierarchical composite mats, analyzed and compared their biosensing performance through amperometric methods. The main contents of the thesis are as follows:(1) Cellulose nanofibers were surface functionalized by Ag nanoparticles (AgNPs). We fabricated Lac biosensors based on AgNPs-Carboxymethyl cellulose (CMC)/cellulose composite nanofibrous mats. Cellulose nanofibers were obtained by electrospinning and deacetyltation. CMC was adsorbed onto cellulose nanofibers to complex silver ions through the chemical binding with the free carboxyl groups of CMC for subsequent reductive formation of AgNPs. Then Lac-modified mats were attached to the surface of glassy carbon electrode (GCE), and the as-prepared Lac/AgNPs-CMC/cellulose/GCE showed an excellent electrochemical catalysis for catechol. Under the optimized condition, Lac/AgNPs-CMC/cellulose/GCE exhibited a detection limit of 1.64 μM (S/N=3), and a wide linear range from 4.98 μM to 3.65 mM, good repeatability, reproducibility, stability, and selectivity.(2) We fabricated a novel hierarchical composite mat composed of electrospun cellulose nanofibers decorated with Ag-doped ZnO (Ag-ZnO) nanoparticles via electrospinning and hydrothermal growth. We further demonstrated its potential application as the efficient Lac biosensor substrate material. Ag-ZnO/cellulose nanofibrous mat provided an excellent microenvironment for Lac immobilization and benefited direct electron transfer of Lac. The fabricated Lac/Ag-ZnO/cellulose/GCE exhibited a highly sensitive detection of catechol with a wide linear range from 0.995 μM to 811 μM and a low detection limit of 0.205 μM (S/N= 3). Meanwhile, it had other performance such as good repeatability and reproducibility.(3) In order to further improve the biosensing performance, polyaniline nanorods were synthesized and immobilized onto the surface of carboxymethylcellulose (CMC)-modified cellulose nanofibers via in situ polymerization. Although highly dense PANI nanorods were grown onto the surface of CMC/cellulose nanofibers, the three-dimensional structure of fibrous mats were preserved, which could be beneficial for the enzyme immobilization. Under optimum conditions, the Lac/PANI/CMC/cellulose/GCE exhibited a fast response time (within 8 s),a linear response range from 0.497 μM to 2277.8 mM with a high sensitivity and low detection limit of 0.374 μM (S/N=3). The developed biosensor also displayed good repeatability, reproducibility as well as selectivity.The thesis combined electrospun nanofibers with nanoparticles to fabricate the flexible biosensing materials; it could provide experimental basis for improving the performance of biosensors. Besides, it has importance scientific significance and practical value in environmental monitoring.