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Author ORCID Identifier
AccessType
Open Access Dissertation
Document Type
dissertation
Degree Name
Doctor of Philosophy (PhD)
Degree Program
Chemistry
Year Degree Awarded
2019
Month Degree Awarded
May
First Advisor
Kevin R. Kittilstved
Subject Categories
Inorganic Chemistry | Materials Chemistry | Physical Chemistry
Abstract
Perovskites such as strontium titanate, a wide band gap semiconductor have been widely studied due to the multitude of potential applications in photocatalysis, multiferroics, sensing, and microelectronics. Various novel optical, electrical and magnetic properties can be imparted through the introduction of different transition metal dopant ions. The introduction of these impurities has been shown to impart functionality for various applications. The use of Cr3+has been shown to introduce defect levels into the band structure of SrTiO3and increase visible light utilization for photocatalysis. Transition metal doped highly crystalline colloidal SrTiO3nanocrystals (NC) were synthesized using two modified hydrothermal (HT) synthesis methods and subsequently characterized. Structural characterization techniques such as powder X-ray diffraction (XRD), tunneling electron microscopy (TEM) and high-resolution tunneling electron microscopy (HR-TEM) proved vital in confirming the successful synthesis of highly crystalline sub-10 nm nanocubes. The use of transition metal doped colloidal nanocrystals will look to better understand dopant incorporation and subsequent defect formation and their interactions on the nm scale.
The use of dopant specific spectroscopies such as electron paramagnetic resonance (EPR) spectroscopy was crucial in determining both the transition metal dopant oxidation state and dopant position in the colloidal NCs. Through the use of EPR spectroscopy the dopants and defects were unambiguously identified and characterized. Various surface related oxygen defects were identified and correlated to emerge under specific synthetic conditions. Site-selective internal doping of Cr or Mn was achieved through either modified HT methods.
The extent of the dopant-defect interactions was studied using a photodoping technique. Under anaerobic conditions and in the presence of a hole quencher, the interactions of the photoinduced electron with SrTiO3were monitored. The photoinduced changes were tracked using electronic absorption spectroscopy and EPR spectroscopy. An in-depth EPR analysis showed the photoinduced electron localizes on titanium atoms and undergoes cross relaxation with neighboring Cr ions.
DOI
https://doi.org/10.7275/14207495
Recommended Citation
Harrigan, William, "Modulating Dopant-Defect Interactions in Transition Metal Doped Colloidal Strontium Titanate Nanocrystals" (2019). Doctoral Dissertations. 1623.
https://doi.org/10.7275/14207495
https://scholarworks.umass.edu/dissertations_2/1623