Investigation On The Preparation Of Electrospun Composite Nanofibers And Their Applications In Environmental Analysis

Nanofibers are linear materials with nanometer-scale diameters and greater lengths.At present,many methods have been developed for preparing nanofibers.As one of the few methods that can incessantly prepare polymer nanofibers,electrospinning technology has unique advantages.Electrospinning is a universal and feasible ultrathin fiber preparation technology.Electrospinning nanofiber membranes are usually used as chemical sensors due to their large specific surface area,high porosity,easy preparation and functionalization,controllable capability,low cost,convenient detection,no obvious contamination of the detection liquid,and easy post-processing after detection.Based on excellent performances,electrospinning nanofibers and their composite materials have been widely used in various fields,such as the removal of organic compounds,dye adsorption,filtration and separation in the environment;supercapacitors,hydrogen storage,batteries in energy;pressure sensors in electronic devices;high-efficiency air and liquid filters,catalyst carriers,thermal insulation materials,conductive materials,dielectric materials and Joule heaters in chemical engineering;biodegradable polymer fibers,tissue engineering scaffolds,hydrogels,drug delivery and release in biomedical engineering.At present,the research of electrospinning composite materials is mainly focused on the research and development of preparation methods,and then applied to filtration,carbon dioxide capture,supercapacitors,etc.In analysis applications,it is mainly used for the development of sensors,but the application research of electrospinning composite materials is not deep enough.In view of this,this paper based on the advantages of easy functionalization of electrospun nanofibers membranes,combined with cadmium telluride quantum dots(Cd Te QDs)of high fluorescence quantum yield and good stability,designed and established a point-of-care testing(POCT)method for the detection of Cu²⁺in the environment.Then based on the advantages of high porosity,electrospun nanofibers which incorporated in metal-organic frameworks(MOFs)and two-step high-temperature calcinations obtained carbon materials with strong adsorption capacity and improve the ability to adsorb dyes.The specific research content includes the following two aspects:1.Electrospun nanofibers are used for the visual and portable detection of Cu²⁺.In this work,electrospun nanofibers(NFs)with good moisture-resistance were prepared by electrospinning technology,and further assembled with Cd Te QDs.The results of infrared spectroscopy,transmission electron microscopy and confocal fluorescence microscopy showed that the Cd Te QDs with strong fluorescence were uniformly assembled on the surface of electrospun NFs after the electrostatic adsorption for 90 min at p H 7.2.Under 365 nm excitation,the Cd Te QDs-NFs assembly presented red fluorescence,which could be significantly quenched by Cu²⁺,and the fluorescence quenching degree of Cd Te QDs-NFs assembly showed a good linear relationship with Cu²⁺concentration in the range of 0.08-800?mol/L,and the detection limit was 11.1nmol/L.This method had advantages of simplicity and high selectivity,and was successfully applied to the visualization and portable detection of Cu²⁺in environmental water samples.2.Super adsorption of composite electrospun nanofibers to methyl blue.As one of the newly developing porous crystalline materials,the metal-organic framework is composed of metal ions(or clusters)and organic linkers.In this work,2-methylimidazole zinc salt(ZIF-8)particles were prepared by a single-step preparation in the water phase,which were embedded in electrospun polyacrylonitrile fibers through the doping method and the electrospinning technology.They were then calcined with argon and air at high temperature in two steps to obtain light carbon material.This kind of composite material presented strong adsorption capacity for organic dyes,especially for methyl blue the maximum adsorption capacity was as high as 2998.18 mg/g..It was proposed that.the calcination enlarged the inner pores,thereby further improving the adsorption capacity.The characterization result found that,the main mechanism of adsorption was the synergism of three effects which are the pore-making effect,electrostatic adsorption and ionic bond formation to improve the adsorption capacity.In summary,in this thesis we used electrospinning technology to prepare two electrospun nanocomposites with different excellent properties,and established a solid-phase visualized detection method of heavy metal ions in environmental water samples,and developed a method for removing pollutants by efficiently adsorbing organic dyes.This thesis aims to provide ideas for the development of POCT detection and test strips,and to broaden new thoughts for pollutant removal.