Laser Spectroscopy for Chemical Imaging

The objective of our program is to advance the state of the art of high sensitivity and high specificity laser-based chemical measurements to further our understanding of chemical systems at the molecular level. We are exploring linear and nonlinear optical spectroscopy as a means to probe molecules at chemically important surfaces and interfaces. We are integrating these methods with both fine spatial resolution for creation of chemically-informative images and with time resolved measurements to yield dynamic information. Spectroscopic measurements of individual particles, as opposed to ensembles of particles, provides specific information relative to size and morphology effects; results are shown for highly nonlinear organic crystals, semiconductor dots, and metal nanoparticles. The tools at hand include ultrafast pulse lasers, 150 fs to 15 ps, spanning the ultraviolet to the mid-infrared spectral regions and an atomic force microscope in registration with our optical methods. Advances in this area will have a profound influence on surface chemical analysis. Confined geometries offer new and interesting possibilities for molecular orientation and manipulation, as well as for forced interactions between small groups of molecules.

 Oriented Emission from 2 nm indium phosphide  nanoparticles

Optical Anisotropy in InP Semiconductor Quantum Dots

Spatially Imaged 2-Photon excited NPP Luminescence

Apertureless NSOM of a Gold Nano-Octahedron Apex

Gold Nano-octrahedra imaging and spectra

Femtosecond Electronic Spectroscopy of Nanostructures