Preparation And Detection-Catalytic Properties Of Nanofiber SERS Substrates

This thesis coupled electrostatic spinning technology,surface plasmon resonance effect,hydrothermal method,and photoreduction method to organically combine organic conjugated polymer polyimide（PI）,inorganic semiconductor titanium dioxide（TiO₂）,and precious metal silver（Ag）to successfully construct a recyclable flexible organic-inorganic nanocomposite surface enhanced Raman scattering（SERS）that combines high sensitivity SERS detection and efficient photocatalytic degradation substrate.The main research contents and related conclusions are as follows:1.Polyamide acid（PAA）nanofibers with uniform size and smooth surface were successfully prepared by electrostatic spinning technique,and Ag nanoparticles were attached on their surface by in situ reduction method,followed by calcination to produce PI/Ag nanocomposite fibers.The structure,morphology and SERS properties of the five PI/Ag nanocomposite fibers were systematically investigated by adjusting the reductant type and concentration.The SERS activity of the five samples was compared using 4-aminothiophenol（4-ATP）as the SERS activity probe molecule.It was shown that the introduction of Ag nanoparticles could significantly improve the SERS activity of the material with an enhancement factor of up to 1.17×10⁷ and a detection limit as low as 1×10^-10 M for 2,4-D pesticides,and the SERS enhancement mechanism of PI/Ag nanocomposite fibers was investigated in depth.In addition,this flexible nanofiber SERS substrate material with high SERS activity exhibits excellent SERS signal homogeneity and does not require complicated steps for recovery.2.TiO₂ nanorods were grown on the surface of conjugated polymer PI nanofibers using in situ growth method,and the structure,morphology and photocatalytic performance of seven PI/TiO₂ nanocomposite fibers were systematically investigated by adjusting the reactant concentration,reaction temperature and reaction time.It was found that the PI/TiO₂-3-160-14 sample had the best photocatalytic activity under simulated sunlight irradiation,and it could completely degrade 5 mg/L rhodamine B（Rh B）within 2 hours.Moreover,excellent photocatalytic activities were also obtained for methylene blue（MB）,methyl orange（MO）and malachite green（MG）,and this result proved the general applicability of PI/TiO₂photocatalyst for dye degradation.In addition,the photocatalyst has good reusability and the recovery of samples does not require complicated operations such as centrifugation and filtration.3.Ag nanoparticles were deposited on the surface of PI/TiO₂ nanofibers using photoreduction method,and three PI/TiO₂/Ag nanocomposite fibers were produced by adjusting the concentration of silver nitrate.The results showed that the PI/TiO₂/Ag nanocomposite fibers SERS substrate could produce good SERS signals for 4-ATP and tetracycline（TC）with an enhancement factor of 1.42×10⁶ and a detection limit as low as 1×10^-10 M.More importantly,under simulated sunlight irradiation,the PI/TiO₂/Ag nanocomposite fibers showed excellent photocatalytic activity for Rh B,MB,MO and TC,and the best effect was achieved for TC degradation,with the degradation efficiency up to3.6 times of PI/TiO₂.In addition,the photocatalytic mechanism of PI/TiO₂/Ag nanocomposite fibers has been thoroughly investigated,the main active substances in the photocatalytic process have been clarified,and the transport mechanism of photogenerated carriers in semiconductor/noble metal Schottky junctions has been elaborated.PI/TiO₂/Ag nanocomposite fibers have successfully realized the integration of pollutant detection and catalysis.