2012 한국바이오칩학회 추계학술대회 Active Plasmonic Hydrogel for Highly Intense Surface-enhanced Raman Scattering Min-Hee Kang, Kyung-Min Hwang and Ki-Hun Jeong Department of Bio and Brain Engineering, KAIST Abstract Metal nanostructures incorporated in a polymeric material can be used to tune the nano gap spacing and expected to serve as a means to enhance surface-enhanced Raman scattering (SERS) signal. This work combines the interesting thermo-responsive behavior of poly n-isopropylacrylamid (pNIPAAm) with the huge SERS enhancement effects of metal nanostructures. pNIPAAm can swell or collapse as a function of temperature and reduce the gap of metal nanostructures bring to highly intense SERS signal. The unique thermo-sensitive properties of pNIPAAm may be applicable for a variety of biomedical applications. Mechanisms of Active Plasmonics Active Plasmonic Platform using Thermo- Responsive Hydrogel for SERS Mechanical G Active Plasmonics Optical Thermal Electric/ Ferro-electric LFO (LuFe2O4) PZT PDMS VO2 LCs(Liquid crystal) pump Light on off Liquid crystal Azobenzene trans-cis photoisomerization drive phase transition of the LCs Nano Lett., 2009, 9 (2), 819-825 Change in dielectric properties Nano Lett., 2011, 8, 281 + - tensile compress metal PZT film Change in period of the textured PZT/metal/PZT structure Nanotechnology, 2008, 19, 435304 Nano-void stretching Stretchable metal-elastomer nano-void Appl. Phys. Lett., 2009, 95, 154103 Increase temperature Heat up Cool down Volume transition of thermo-sensitive hydrogel pNIPAm depend on temperature J. Phys. Chem. B, 2006, 110, 2051 Change in an orientaion of the LCs in the layer adjacent to the nanostructured metallic film Nano Lett., 2008, 8, 281 poly n-isopropylacrylamid (pNIPAAm) Figure 2. Schematic showing an active plasmonic hydrogel platform composed of gold nanoparticles(AuNPs) and metal nanoislands for highly intense surface-enhanced Raman scattering. Combining the interersting thermo-responsive behavior of poly n-isopropylacrylamid (pNIPAAm) with the huge SERS enhancement effects of metal nanostructures. pNIPAAm can swell or collapse as a function of temperature and reduce the gap of metal nanostructures bring to highly intense SERS signal. Figure 1. Various active plasmonics. Active manipulation of the plasmonic properties utilized by optical, electronic, ferroelectric, or thermal method. Characterization of pNIPAAm : Thermo-responsive Behavior SERS Experiments of Active Plasmonic Hydrogel 0 10 20 30 40 50 0.0 1 20 28 33 40 -0.1 pNIPAAm /AuNPs Au /pNIPAAm (a) (b) DSC (mW/mg) -0.2 32.4 ℃ * -0.3 * @ 40 ℃ Time (sec) Temperature (℃) Figure 3. Aqueous polymer solution of pNIPAAm undergoes a phase transition from soluble to an insoluble state. DSC(differential scanning calorimeter) thermogram of a pNIPAAm. The temperature scanning rate is 1 ℃/min. Characterization of pNIPAAm : Optical Properties (a) AuNPs (b) pNIPAAm /AuNPs @ 25℃ (c) pNIPAAm /AuNPs @ 40℃ (d) pNIPAAm 360sec 60sec Figure 5. SERS comparison of R6G 100μM between pNIPAAm/AuNPs and Au/pNIPAAm/AuNPs platform at 25 and 40 ℃, respectively (vertically offset for clarity). Furthermore, in the case of Au/pNIPAAm/AuNPs platform, it can be seen that the intensity of R6G Raman signal at 1348cm-1 (* indicates 1348cm-1 band) increases when the temperature is increased. The SERS intensity at 40℃ for the same band at 1348cm-1 is about 1.5 times of that at 25℃. Figure 4. Dark field images and extinction spectra of (a) AuNPs, (b) pNIPAAm/AuNPs @ 25℃,(c) pNIPAAm/AuNPs @40 ℃ for 1min and (d) 10min, respectively. Conclusion Acknowledgement pNIPAAM can swell or collapse as a function of temperature. (Thermo-responsive). This change is expected to serve as a means to reduce the gap of metal nanostructures and enhance the SERS signal. We have designed, characterized, and applied an advanced platform for SERS Signal enhancement using pNIPAm. The unique thermo-responsive properties of pNIPAAm may be applicable for a variety of biomedical applications. This work was supported by the National Research Foundation of Korea (NRF)(No. 2011-0016481, No. 2011-0020186, No. 2011-0031868 ) grant funded by the Korea government, IT R&D program(No. KI 001889) and (No.10041120) of MKE/KEIT. 2012 한국바이오칩학회 추계학술대회 JIST, Korea