Surface Enhanced Raman Scattering and Spectroscopy Advancements
Delve into the world of Surface Enhanced Raman Scattering (SERS) and spectroscopy advancements, revolutionizing research in physics, chemistry, biology, and medicine. Explore the discovery of SERS, enhancement techniques, and the significant role of quadrupole interactions in improving sensitivity and accuracy. Uncover the complexities of light-molecule interactions, electric field enhancements, and the power of spectroscopic investigations in various scientific fields.
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1 2 V.P. Chelibanov and A.M. Polubotko 1 State University of Information Technologies, Mechanics and Optics Kronverkskii 49, Saint Petersburg 197101, Russia 2 A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, Politechnicheskaya 26, 194021, Saint Petersburg Russia Spectroscopy is a powerful tool for investigation of molecules and can be very useful in physics chemistry, biology and medicine
d surf 6 = 10 G ~ d vol Molecules Metal-(silver, copper, gold)
Discovery of Surface Enhanced Raman Scattering, SERS, is a great achievement, because it allows to rise the sensitivity of this method There are another Surface Enhanced optical processes Surface Enhanced Infrared Absorption (SEIRA) d G = surf 2 ~ 10 SEIRA d vol Surface Enhanced Hyper Raman Scattering (SEHRS) d surf 12 = ~ 10 G SEHRS d vol
For more real model of the roughness there is the enhancement both the component of the electric field, which is perpendicular to the surface and the enhancement of its derivatives l 1 ~ E E C inc 0 r r 1 E r ~ E r r r This results in the necessity to take into account not only the dipole but the quadrupole light-molecule interaction, because of the increase of the electric field derivatives.
* * e i t i t + ( ) ( ) e f e e f e inc inc inc e inc inc = e H E inc r 2 * * e i t i t + ( ) ( ) e f e e f e scat scat scat e scat scat = e H E scat r 2 E 1 = + f d Q e e e 2 E x , , Q Q Q xx yy zz The second factor is that the quadrupole interaction with a constant sign are responsible for the strong additional enhancement, while the moments are not essential , , Q Q Q xy xz yz Q , , Q Q Q The moments, are designated as main xx yy zz
f = ( , ) d Q f = ( , ) d Q 1 1 f = ( , ) d Q f = ( , ) d Q 2 2 In SERS it takes place via various combinations of the dipole and quadrupole moments, for example ( ) Q d ( ) Q Q main z main main
It can be demonstrated that the quadrupole interaction with the moments z d Q can be more than the dipole interaction with the moment main The quadrupole interaction and the increase of the number of moments, responsible for the scattering results in the change of the SERS, SEHRS and SEIRA spectra of molecules of symmetrical molecules and appearance of forbidden lines. , , Q Q Q The most enhanced scattering arise from the scattering via the moments xx yy zz z d and ( ) Q Q In SERS the most enhanced scattering occur via main main ( ) Q d main z
The quadrupole interaction changes main regularities of thesespectra and results in appearance of strong forbidden lines The SERS spectrum of ethylene A g Ag A B1 g u allowe d allowed A 1 1595 cm g ( ) Q Q main main A B1 1 1331 cm g ( ) Q d 1 forbidden 971 cm main z u
The SEHRS spectrum of pyrazine with D2h symmetry group Wu-Hu Li, Xiao-Yuan Li, Nai-Teng Yu // Chem. Phys. Lett. 1999, V. 305, P. 303.
The SEHRS spectrum of phenazine with D2h symmetry group Wu-Hu Li, Xiao-Yuan Li, Nai-Teng Yu, Chem. Phys. Lett. 327, 153, (2000)
+ 2 2 BiPyH Yu-Xia Diao, Mei-Juan Han, Li-Jun Wan, Kingo Itaya, Taro Uchida, Hiroto Miyake, Akira Yamakata and Masatoshi Osawa, Langmuir 22, 3640, (2006).
CONCLUSION Thus the theory, which is based on the conception of the strong quadrupole light-molecule interaction successfully explains all features of the spectra of Surface Enhanced Optical processes. It can be demonstrated that it explains all accompanying phenomena.
