Date of Award
Doctor of Philosophy
Tessa R. Calhoun
Bin Hu, Sharani Roy, Michael J. Sepaniak
Since the inception and the development of high power lasers, nonlinear spectroscopy and microscopy have been pushing the boundaries for optical techniques. These techniques have changed how we understand emerging materials and revolutionized imaging capabilities. Herein is presented work which aimed to produce electronic sum frequency generation (eSFG) using a photonic crystal fiber (PCF) and Ti:Sapphire femtosecond laser as the light sources while using objective-based total internal reflectance within a microscope apparatus. The large aim of this work was to apply this instrument to study the surfaces of cadmium selenide (CdSe) quantum dots (QDs). Quantum dots have emerged as a flexible and useful material for light harvesting and light emitting applications, including television screens, lighting diodes, biomedical imaging probes, catalytic substrates, and solar panel application. Despite the current applications of these QDs, the material still exhibits deleterious flaws mostly due to the lack of control over their surface properties. While there are continuous strides in this field of research, the work here aimed to provide a better understanding of these surfaces in order to incubate further advances. The instrument described above observed electronic structure within the mid-band gap region which has previously proven difficult to study. Since the electronic properties of CdSe QDs are so intricately connected to the ligand or shell attached to the nanocrystal surface, the study the CdSe QD surfaces was furthered by vibrational sum frequency generation spectroscopy (vSFG) to better understand the ordering and presence of ligands at the QD interface. This instrument has not only been applied to CdSe QDs but other light harvesting materials, specifically inorganic-organic lead based perovskite films. A two-photon total internal reflectance based microscopy was able to reveal dipole orientations of the perovskite film and shows sensitivity to the films topography. Together these studies show the flexibility of this instrument to study important electronic properties effecting the application of light sensitive materials.
Watson, Brianna Renee, "Probing the Interfaces of Semiconducting Nanoparticles using Sum Frequency Generation: Instrumentation Development and Design. " PhD diss., University of Tennessee, 2018.