1. 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),
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,
Nano-void
stretching
Stretchable metal-elastomer
nano-void
Appl. Phys. Lett., 2009, 95,
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
0.0 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
25℃
(c) pNIPAAm
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) 25℃,(c) ℃ 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 , No , No ) grant funded by the Korea government, IT R&D program(No. KI ) and (No ) of MKE/KEIT.
2012 한국바이오칩학회 추계학술대회
JIST, Korea