Seminar Series Spring 2018
Hybrid plasmonic colloidal nanoparticles and their interactions with biological molecules, dye molecules, and light are investigated using nonlinear and ultrafast spectroscopy. The photocleaving dynamics of microRNA-functionalized plasmonic nanoparticles in colloidal suspension in water are monitored using time-dependent second harmonic generation (SHG) measurements. MicroRNA is functionalized to spherical colloidal gold and silver nanoparticles using molecular linkers that cleaves upon ultraviolet irradiation or increased local temperature. The real-time SHG measurements determine the photocleaving rates under varying laser irradiation wavelengths and powers. Additionally, molecular adsorption and resonant coupling are studied for dye molecules interacting with colloidal gold nanoparticles in water. SHG is used to measure adsorption isotherms of several dyes such as malachite green and brilliant green to the colloidal nanoparticle surface and the results are fit using the modified Langmuir model to determine the free energies of adsorption and the adsorbate site densities. Complementary measurements of the extinction spectra of the combined dye and nanoparticle solutions reveal strong polaritonic states from resonant coupling that depend on the dye-plasmonic nanoparticle interactions. The resonant coupling spectroscopy agrees with computational simulations using a multiscale hybrid/classical approach, showing polariton peaks that overlap with a Fano-type profile. Lastly, ultrafast energy transfer and heating dynamics are studied in colloidal gold-silver-gold core-shell-shell nanoparticles using transient absorption spectroscopy. The plasmon resonance of these core-shell-shell nanoparticles can be controlled by varying the core and shell dimensions for enhanced photothermal effects in the near infrared. These nonlinear and ultrafast spectroscopic investigations provide important information on the surface chemistry, photocleaving rates, optical interactions, and enhanced heating dynamics of plasmonic nanoparticles for potential applications in drug delivery, molecular sensing, and photothermal cancer therapy.
Professor Louis H. Haber studied chemistry at the University of California, Berkeley, where he received his B.S. and Ph.D. degrees in 2002 and 2009, respectively. He worked for 3 years as a postdoctoral researcher in the Department of Chemistry at Columbia University from 2009 to 2012. In 2012, he accepted a position as Assistant Professor in the Department of Chemistry at Louisiana State University. His current research interests include fundamental investigations of nanoparticles and nanomaterials and their interactions with molecules and light using ultrafast spectroscopy and nonlinear spectroscopy. Additionally, his research focuses on potential applications in molecular sensing, nanomedicine, catalysis, nanoengineering, solar energy, and optoelectronics.
Thursday, February 1 2018 @ 3:30 PM in Burson 115 Refreshments served at 3:15 PM