Preparation Of Flexible SERS Substrate And Its Application In Biological Detection

Because of its relatively simple preparation conditions and its unique response to external environments(such as pH,temperature,mechanical pressure,and metal chelating agents),supramolecular hydrogels have been developed in biomedical and antibacterial materials.The supramolecular metallogels with metallic nanostructures not only has the multiple stimulus response characteristics of the supramolecular hydrogel,but also imparts some unique properties to the material due to the introduction of metal ions.These characteristics have all contributed to the emergence of supramolecular metallogels with metal nanostructures as one of the hot spots in the field of supramolecular gels.In this thesis,we report a solution of chitosan(CS)or carboxymethyl chitosan(CMCh)solution as a polymer matrix material,silver ion salt solution as a physical cross-linking agent,the hydroxyl group on the chain complexes with the amino group to form a supramolecular metal gel based on silver nanoparticles at room temperature.Since no other reducing agent is used during the formation of silver nano-particles in situ,only the functional groups on the polymer chain are used.Therefore,this is a simple and environmentally friendly method for preparing supramolecular hydrogels.In addition,CS/AgNP supramolecular Hydrogels were characterized by Fourier transform infrared(FT-IR)spectroscopy,X-ray diffractometry(XRD),UV-Vis spectrophotometry,field emission scanning electron microscopy(FE-SEM)and Raman spectroscopy.FE-SEM and Raman results clearly indicate that both the diameter and the amount of the AgNPs within the chitosan/AgNP nanocomposite hydrogel are tunable by simply adjusting either the reaction time or the pH value of the chitosan solution.In this study,the chitosan/AgNP nanocomposite hydrogel is employed as 3-dimensional flexible SERS substrate for the detection of pyocyanin(i.e.,a typical quorum sensing signal molecule).Raman data suggest that the limit of detection for pyocyanin in aqueous solution could be as low as 5 ?M.