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Singly vibrationally enhanced infrared four wave mixing spectroscopy (1998)

LaBuda, Mitchell J. ; Wright, John C.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 108 (1998), S. 4112-4122

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: We describe a new nonlinear, nonparametric process that provides a direct measure of vibrational enhancement in four wave mixing. This process has 14 coherent pathways that create the final coherence. In the limit of no pure dephasing and a single vibrational resonance, the 14 pathways combine into a single process that is vibrationally enhanced. The frequency and concentration dependence expected for this process matches that observed in experiments with the methyl- and methylene C–H stretch vibrations in hexane samples. The third-order nonlinear susceptibility for the C–H vibrations was measured by the interferometric method of Levenson and Bloembergen. The vibrational nonlinearity was observed as a difference between the nonresonant electronic contributions and the contribution that depended on resonance with the vibrational absorption transition. The measurements show that the vibrational enhancement is 50 times larger than the nonresonant electronic contribution and it shows that spectroscopic methods based on resonant nuclear nonlinear polarizations are observable above the electronic nonlinear polarization background. © 1998 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.475809

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Matrix Effects on Selective Chemical Sensing by Sol-Gel Entrapped Complexing Agents (1998)

Sommerdijk, Nico A.J.M. ; Wright, John D.

Springer

Journal of sol gel science and technology 13 (1998), S. 565-568

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ISSN: 1573-4846

Keywords: composites ; chemical sensing ; spectrophotometry ; surface plasmon resonance

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Changes in the selectivity of molecular recognition systems on sol-gel entrapment are reported. Thermodynamic effects are exemplified by studies of the metal-ion complexing agent Eriochrome Cyanine R (ECR). In aqueous solution this binds strongly and selectively to Al3+, whereas in a TMOS-based sol-gel matrix it is selective for Cu3+. Thermodynamic effects, due to restricted translational freedom of water molecules or different solvent structure and isolation of ligands, can explain these observations. Effects of entrapment on molecular recognition by a large conformationally flexible molecule have been studied using a tris-terminated PAMAM dendrimer. The dendrimer conformation and its complexation with Cu2+ changes on entrapment, and binding of aromatic carboxylic acids such as ibuprofen can be detected by changes in visible absorption and surface plasmon resonance using spun films of the sol-gel composite. These effects show that in addition to providing a porous entrapment matrix of good optical quality, sol-gels may be used to alter the binding characteristics of the entrapped receptors.