MSE PhD Final Defense of Reyhaneh Toufanian

TITLE: SYNTHESIS AND CHARACTERIZATION OF INDIUM PHOSPHIDE-BASED QUANTUM DOT HETEROSTRUCTURES

ABSTRACT: Colloidal semiconductor nanocrystal quantum dots (QDs) have been extensively studied for applications in optoelectronic devices, biosensing, and imaging. Recent interest has turned to heavy metal-free compositions such as indium phosphide as an alternative to cadmium- and lead-based materials. Photoluminescence emission from InP QDs is size-tunable over a wide spectral range, providing superior color tuning compared to traditional CdSe QD but their optical properties and chemical synthesis is less well established. This study examines how InP-based heterostructures can be engineered to enhance their utility as heavy metal-free fluorophores emitting throughout the visible and near infrared (NIR) wavelength ranges by addressing three fundamental materials design and synthesis issues.

First, the bandgap engineering of InP-based QDs is achieved by varying the core size, shell composition, and shell thickness of a core/shell heterostructures, generating emitters spanning 500 – 1100 nm. Second, the brightness mismatch between small blue/green emitters and large red-emitting QDs is addressed by tuning the absorption cross-section and extinction coefficient by synthesizing a series of QDs with a combination of core sizes, shell thicknesses, and shell compositions, resulting in a rainbow of brightness-matched InP emitters. Finally, the synthesis of inverted InP heterostructures, producing the reddest-emitting InP QDs ever reported by generating photoluminescence from a quantum confined InP shell, was significantly improved. The non-toxic nature of InP in conjunction with its unique optical properties render it an excellent candidate for use in in vitro and in vivo clinical or commercial settings.

COMMITTEE: ADVISORAllison M. Dennis, MSE, BME; Malika Jeffries-EL, MSE, Chemistry; Tyrone Porter, UT Austin, BME; Sahar Sharifzadeh, ECE, MSE; CHAIR: Joerg Werner, MSE, SE

When 9:00 am on Thursday, December 17, 2020
Location Zoom