Preparation Of Poly (N - Isopropylacrylamide) (PNIPAAm) / Silver Nanoparticle Complex And Its Dynamic SERS Study

Comparing to the Raman spectra, surface-enhanced raman scattering(SERS) spectra are sensitive for the detection of signal molecule. SERS substrates are essential in the SERS detection. However, in most cases, once the SERSsubstrates are formed, the spatial distribution of AgNPs is fixed which lead to the limitation of dynamic SERS detection. In ordor to get a dynamic SERS substarte, intelligent polymer Poly(N-isopropylacrylamide)(PNIPAAm) was induced for the fabrication of intelligent SERS substrates. Using the extra-stimulus responsibility of PNIPAAm, these composite material can be used as dynamic SERS substrate that have potential application. In this paper, three methods were used for fabrication of PNIPAAm / AgNPs composite material, and these composite metarial served as dynamic SERS substrates for the SERS detection. Detail as following:An intelligent PNIPAAm/AgNP composite film was fabricated by the simple assembly of silver nanoparticles on the surface of photo-polymerized PNIPAAm film via electrostatic interaction. Surface enhanced Raman scattering study and finite-difference time-domain simulation demonstrated that the local electric field intensity and the SERS intensity of this resultant composite film can be easily tuned by changing the interparticle distance triggered by temperature or solvent variations. The composite film showed a high stability in a polar organic solvent and concentrated saline solution. The smart composite film might find applications as a SERS sensor for temperature/solvent variation detection as well as a versatile SERS substrate for the detection of analyte in sea water and organic solventSilver nanoparticles(AgNPs) / Poly(N-isopropylacrylamide)(PNIPAAm) composite solution were electrospun followed by crosslinking to fabricate AgNPs / PNIPAAm composite nanofiber mats. Embedded AgNPs were found to align along the PNIPAAm nanofibers, which generate more hot-spots upon temperature increases or laser induced plasmonic heating. This kind of AgNPs / PNIPAAm composite nanofiber mats show enhanced SERS effect upon continuous pulsed laser irradiation, showing a “laser sensitive” SERS effect. Laser induced plasmonic heating can also tune the temperature-responsive interaction between PNIPAAm and analytes and have been utilized in the on-site “laser sensitive” separation and SERS detection of analytes. The composite nanofiber mats also showed good reproducibility and stability. What’s more, the strong interaction between PNIPAAm and urea was applied in the direct SERS detection of adenosine in urea solution without urea interferance. Together with the advantages of ease of large-scale fabrication, inexpensive, stable and ‘laser sensitivity”, AgNPs/PNIPAAm composite nanofiber mats might find application in sensitive multicomponent biosensing.By using RAFT polymerization and the reduction of NaBH4, PNIPAAm-SH was obtained, and AgNPs@PNIPAAm were fabricated by mixing AgNPs and PNIPAAm-SH to form the chemical bond between Ag and S atoms. AgNPs@PNIPAAm served as SERS substrate can be used for the detection of PAHs, which have a good SERS sensitivity. This can be contributed to the hydrophobic property of PNIPAAm with the evaporation of solvent. And the AgNPs@PNIPAAm have a salt tolerance. These founding provide new insight into an attractive of AgNPs and polymer composite nanomaterials that can find application in the SERS detection of organic pollutant in river and sea.