Interfacial SHG


Second Harmonic Generation at the air/liquid and liquid-liquid interface

Using this technique my group has looked, for example, at the way the orientation of adsorbed species such as dyes, peptides and complexes, depend on the polarity of the solvent at how adsorbed species can be influenced by applied fields and, by using a flow cell, at the temporal evolution of liquid-liquid interfaces.  The results of my research have demonstrated that it is essential to record the full polarisation behaviour of the SHG fields, which led me to develop an ellipsometric technique as an efficient and effective way of obtaining this information.  In order to interpret the SHG data we carry out high level ab initio calculations on frequency-dependent molecular hyperpolarisibilities. We combine the ab initio calculations with orientation and conformations from molecular simulations at the air/liquid interface to predict the SHG results.  I have also made significant contributions to the understanding of non-linear chiral effects and our study of small peptides at liquid interfaces has shown the importance of the large circular differential scattering in the optical response of such systems.  These studies have opened the way to the investigation of the secondary and tertiary structure of proteins within a membrane by spectroscopic techniques.

Sono, T.J., Scott, J.G., Sones, C.L., Valdivia, C.E., Mailis, S., Eason, R.W., Frey, J.G. and Danos, L., Reflection second harmonic generation on a z-cut congruent lithium niobate crystal. Phys Rev B, accepted 2006.

Frey, J.G., Second Harmonic Generation at Liquid-Liquid Interface, In: Waterai, H. ed. Interfacial Nano-chemistry, Kluwer Academic, 2005, Chapter 1.

Rousay, E.R., Fu, H.C., Robinson, J.M., Essex, J.W. and Frey, J.G., Grid-based dynamic electronic publication: A case study using combined experiment and simulation studies of crown ethers at the air/water interface. Philos. Trans. R. Soc. London, A, 363 (1833), 2005, 2075-2095.

Fordyce, A.J., Bullock, W.J., Spencer-Smith, R.D. and Frey, J.G., Probing possible structural models at the air/H2SO4(aq) interface: a second harmonic generation study. Physical Chemistry Chemical Physics, 6 (9), 2004, 2415-2419.

Timson, A.J., Spencer-Smith, R.D., Alexander, A.K., Greef, R. and Frey, J.G., Second Harmonic ellipsometry. Meas. Sci. Technol., 14 (4), 2003, 508-515.

Fordyce, A.J., Bullock, W.J., Timson, A.J., Haslam, S., Spencer-Smith, R.D., Alexander, A. and Frey, J.G., The temperature dependence of surface second- harmonic generation from the air-water interface. Mol. Phys., 99 (8), 2001, 677-687.

Haslam, S., Croucher, S.G., Hickman, C.G. and Frey, J.G., Surface second harmonic generation studies of the dodecane/water interface: the equilibrium and kinetic behaviour of p-nitrophenol and tri-n-butyl phosphate. Physical Chemistry Chemical Physics, 2 (14), 2000, 3235-3245.

Frey, J.G., Interfacial second harmonic generation in the limit of weak orientational order: determining interfacial refractive index. Chem. Phys. Lett., 323 (5-6), 2000, 454-459.

Crawford, M.J., Frey, J.G., VanderNoot, T.J. and Zhao, Y.G., The Investigation of Transport across an Immiscible Liquid-Liquid Interface: Electrochemical and Second Harmonic Generation Studies. J. Chem. Soc. Faraday Trans., 92 (8), 1996, 1369-1373.

Crawford, M.J., Haslam, S., Probert, J.M., Gruzdkov, Y.A. and Frey, J.G., Second Harmonic Generation from the air/water interface of an aqueous solution of the dipeptide Boc-Trp-Trp. Chem. Phys. Lett., 230 (3), 1994, 260-264.