Columbia University

Battelle Memorial Institute

Northwestern University

Kenneth B Eisenthal

Franz M Geiger

Paul E Ohno

Hong-fei Wang

Joshua S Salafsky

An apparatus for probing an interface via second harmonic generation (SHG) spectroscopy is provided. The apparatus comprises a sample cell comprising a noncentrosymmetric material having a selected orientation angle with respect to a reference axis; optics configured to illuminate an interface formed between the noncentrosymmetric material and a different material, or formed between two different materials and disposed over the noncentrosymmetric material, with light having a frequency &#x3c9; under conditions to generate a second harmonic generation (SHG) signal having frequency 2&#x3c9;; a detector configured to detect the SHG signal, the SHG signal comprising a bulk second harmonic signal from the noncentrosymmetric material and an interfacial second harmonic signal from the interface; and a device comprising a processor and a computer-readable medium operably coupled to the processor, the computer-readable medium having computer-readable instructions stored thereon that, when executed by the processor, cause the apparatus to: illuminate the interface to generate the SHG signal and detect the SHG signal.

Optical quantification of interfacial charge states

Methods of generating second harmonic generation (SHG) signals from interfaces formed with, or formed over, a noncentrosymmetric material, e.g., &#x3b1;-quartz, are provided. The methods make use of the noncentrosymmetric material as an internal phase reference for the determination of a variety of interfacial electrostatic parameters, including interfacial potential, interfacial charge density, and the sign of the interfacial charge (i.e., net positive or net negative).

This invention provides methods of detecting molecules at an interface, which comprise labeling the molecules with a second harmonic-active moiety and detecting the labeled molecules at the interface using a surface selective technique. The invention also provides methods for detecting a molecule in a medium and for determining the orientation of a molecular species within a planar surface using a second harmonic-active moiety and a surface selective technique.

Attachment of second harmonic-active moiety to molecules for detection of molecules at interfaces

Second harmonic generation (SHG), sum frequency generation (SFG) and difference frequency generation (DFG) can be used for surface analysis or characterization of microparticles having a non-metallic surface feature. The microparticles can be centrosymmetric or such that non-metallic molecules of interest are centrosymmetrically distributed inside and outside the microparticles but not at the surface of the microparticles where the asymmetry aligns the molecules. The signal is quadratic in incident laser intensity or proportional to the product of two incident laser intensities for SFG, it is sharply peaked at the second harmonic wavelength, quadratic in the density of molecules adsorbed onto the microparticle surface, and linear in microparticles density. In medical or pharmacological applications, molecules of interest may be of drugs or toxins, for example.

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New York, NY, United States of America

Kenneth B Eisenthal