Surface Enhanced Raman Spectroscopy

Jim Krier

Raman scattering

commons.wikimedia.org; “Physical Chemistry” by Mortimer, 2000.

Scattering is typically 10-6 lower in intensity than Rayleigh intensity (signal enhancement needed!)

Difficult to differentiate among small molecules with similar covalent bonds

Raman used as a complement to IR spectroscopy

SERS enhancement

First reported by Martin Fleishman in 1974

Electric field enhancement from plasmon excitation

Directionality of adsorbates/phonons is a critical element of enhancement factor (EF)

In effect, plasmons convert the Rayleigh signal to a Stokes shift

Prokes, S.M.; Glembocki, O.J.; Rendell, R.W. NRL Review 2007, 175.

Orientation issues

Visible laser

Pyridine

Fleischmann, M.; Hendra, P. J.; McQuillan, A. J., Chem. Phys. Lett .1974, 26,163.

Rhodamine 6G

Hildebrandt, P.; Stockburger, M. J. Phys. Chem. 1984, 88, 5935.

Tao, T.; Kim, F.; Hess, C.; Goldberger, J.; He, R.; Yugang, S.; Younan, X.; Yang, P. Nano Lett. 2003, 3, 1229.

Langmuir-Blodgett trough

Tao, T.; Kim, F.; Hess, C.; Goldberger, J.; He, R.; Yugang, S.; Younan, X.; Yang, P. Nano Lett. 2003, 3, 1229.

“Logs-on-a-river”

Tao, T.; Kim, F.; Hess, C.; Goldberger, J.; He, R.; Yugang, S.; Younan, X.; Yang, P. Nano Lett. 2003, 3, 1229.

R6G detection

EF ~ 2 x 109

Tao, T.; Kim, F.; Hess, C.; Goldberger, J.; He, R.; Yugang, S.; Younan, X.; Yang, P. Nano Lett. 2003, 3, 1229.

2,4-Dinitrotoluene detection

EF ~ 2 x 105

~ 0.7 picogram sensitivity

NO2 stretching mode

Tao, T.; Kim, F.; Hess, C.; Goldberger, J.; He, R.; Yugang, S.; Younan, X.; Yang, P. Nano Lett. 2003, 3, 1229.

Well defined, reproducible media that can be put atop a variety of solid materials

Geometric structure allows larger electric field enhancement compared to nanospheres

Can be used to detect analytes which are air-bourne or in solution

Advantages of nanowire monolayers

Prokes, S.M.; Glembocki, O.J.; Rendell, R.W. NRL Review 2007, 175.

Cao, Y.C.; Jin, R.; Mirkin, C.A. Science 2002, 297, 1536.

Dye tagging

Cao, Y.C.; Jin, R.; Mirkin, C.A. Science 2002, 297, 1536.

Cao, Y.C.; Jin, R.; Mirkin, C.A. Science 2002, 297, 1536.

Further reading …

Tao, T.; Kim, F.; Hess, C.; Goldberger, J.; He, R.; Yugang, S.; Younan, X.; Yang, P. Nano Lett. 2003, 3, 1229.

Cao, Y.C.; Jin, R.; Mirkin, C.A. Science 2002, 297, 1536.

SERS review article:

Kneipp, K.; Kneipp, H.; Itzkan, I.; Dasari, R. R.; Feld, M. S. J. Phys.: Condens. Matter 2002, 14, R597.