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 silver nanoparticles in colloidal suspension in water are monitored using time-dependent second harmonic generation (SHG) measurements. MicroRNA is functionalized to 65 nm spherical colloidal silver nanoparticles using a nitrobenyzl linker that cleaves upon ultraviolet irradiation. The real-time SHG measurements determine the photocleaving rates under varying laser irradiation wavelengths and powers. The results are compared to corresponding SHG measurements in microRNA-functionalized polystyrene nanoparticles, showing that the silver nanoparticles display a six-fold plasmon enhancement in photocleaving with a maximum efficiency at 365 nm. Additionally, molecular adsorption, resonant coupling, fluorescence enhancement and quenching, and altered ultrafast excited-state dynamics are studied for dye molecules interacting with colloidal gold-silver-gold core-shell-shell nanoparticles. SHG is used to determine the adsorbate site density and free energy of adsorption for brilliant green and rhodamine 110 adsorbing to plasmonic nanoparticles in water. Significant energy transfer and faster excited-state lifetimes are observed for rhodamine 110 while negligible energy transfer is observed for brilliant green from transient absorption spectroscopy measurements. Finally, photothermal cleaving dynamics are determined using time-dependent SHG measurements under near-infrared irradiation in microRNA-functionalized gold-silver-gold core-shell-shell nanoparticles using a thermally-activated linker. These nonlinear and ultrafast spectroscopic investigations provide important information on the surface chemistry, photocleaving rates, and enhanced molecular sensing in hybrid plasmonic nanoparticles for potential biological applications.<br/>

Nonlinear and ultrafast spectroscopy of gold-silver-gold core-shell-shell nanoparticles

253rd National Meeting (2017)

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