Spectroscopic Studies of Metals, Fluids, and Molecules on the Nanoscale Using Computational and Experimental Methods

Abstract

Light has the ability to relay information on the physical world to incredibly small scales. From the nanoscale to further below, many of the complex dynamics underpinning the behaviors of small particles, atoms, and molecules are not able to be ascertained using traditional measurement methods. In order to determine the physics at this scale, spectroscopic methods are used, exploiting light-matter interactions to extract information on the materials of interest. In the first section of the following dissertation, nanoscale fluid dynamics will be explored through spectroscopic measurements on vibrating metal nanoparticles. Transient absorption measurement analysis reveals information on the solid-liquid interface and nanoscale fluid-dynamics. The slip between the nanoparticle surface and fluid is shown to have a substantial dependence on the length of ligand molecules along the surface. This indicates one of the factors affecting nanoscale fluid flow, which is of vital importance to understanding the fundamental physics of this regime and to develop applications involving nanoscale objects in fluids. In the second portion, a comprehensive modeling procedure for transient absorption and Raman spectroscopy on noble metal nanoparticles is presented. Simulations of spectroscopic methods are able to aid in experimental data analysis as well as in the search for materials matching the specifications required for applications. The presented simulation method is accurate to real-world experiments as it includes realistic vibrational amplitudes and treats vibrational modes often considered to be non-contributing. Simulation outputs are shown for several geometries that have known spectra and geometries that have never-before been measured. In the final section, spectroscopic measurements on molecules are discussed. The measured samples, known as light-harvesting molecules, are synthetic versions of those vital for photosynthetic processes. The major interesting characteristic of these molecules are their ability to absorb incident sunlight and undergo an ultrafast transfer process to transmit the energy to another location. These molecules have a number of potential uses including solar energy conversion and in bio-compatible imaging. Transient absorption and time-resolved photoluminescence spectroscopy are used to characterize this energy transfer. In all measured samples, highly efficient energy transfer is observed, indicating that these molecules are good candidates for solar cell or imaging applications.