As the fields of science and technology approach smaller and smaller size scales, it becomes increasingly vital to fully understand heat transfer at the nanoscale. For the continued construction and success of nanodevices and nanostructures, thermal transport and heat dissipation must be fully characterized. Classical theory and laws associated with heating are expected to be unable to accurately model the temperature behavior of the nanostructures and the surrounding medium.
The research conducted here is at a unique position to explore ways of overcoming some of the deficiencies of classical theory. Photothermal studies and nanocalorimetry measurements have already helped elucidate some exciting information. However, these studies have largely focused on aggregates of nanoparticles and nanostructures. Heat transfer studies were conducted on a single-particle level to better understand what is occurring on the nanoscale.
The specific aim of this research was to create a novel nanoscale temperature sensor using erbium ions in a III-V semiconductor thin-film host matrix on a silicon substrate, and use it and single-particle photothermal methods to characterize the heating effects of gold nanostructures on the surface. Combining the properties of gold with the properties of a rare-earth metal, in conjunction with a laser and a semiconducting thin film, the methods at the heart of this research will increase our current understanding of single particle heating on the nanoscale. This research will facilitate the measurement of heating effects at a scale previously unachieved.
Multiple objectives were met to realize the specific aim of this project. First, a repeatable protocol was developed for immobilizing the gold nanoparticles and nanostructures on the thin-film surface with reliable single particle dispersion and coverage density. Next, a procedure was devised for locating and differentiating single nanostructures on the surface of the thin film. A 532 nm continuous-wave laser was then be used to create a calibration curve to correlate the relative photoluminescence (PL) intensities of the erbium (Er3+) ions in the semiconductor thin film with local thermal effects. Next, an algorithm using the calibration curve was developed and employed to convert the Er3+ PL spectra to changes in temperature. These methods allowed the investigation of interfacial effects, nano-confined thermal effects (such as the superheating of water), and the remote determination of absorption cross section and temperature-dependent thermal conductivity.
|Commitee:||Govorov, Alexander, Rack, Jeffrey, Van Patten, P. Gregory|
|Department:||Chemistry and Biochemistry|
|School Location:||United States -- Ohio|
|Source:||DAI-B 78/11(E), Dissertation Abstracts International|
|Subjects:||Chemistry, Physical chemistry|
|Keywords:||Collective, Gold, Heating, Nanoparticle, Nanoparticles, Nanostructures, Novel, Optical, Photothermal, Sensor, Thermal|
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