Structure-Optoelectronic Property Relationships in Homogeneous and Heterogeneous/Gradient Alloyed Colloidal I-(II)-III-VI Quantum Dots

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With support from the Macromolecular, Supramolecular and Nanochemistry Program (MSN) in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), Colin Heyes and Robert Coridan of the University of Arkansas are combining advanced chemical synthesis and analysis tools to characterize the structural, optical and electronic properties of semiconducting nanoparticles (2 – 10 nanometers in diameter) composed of three or more elements. These elements replace toxic elements that are commonly used in semiconducting nanoparticles, such as cadmium, with more benign ones, such as copper, indium and zinc. However, much less is known about how to control the optical and electronic properties of nanoparticles incorporating these elements. Heyes, Coridan and their students are addressing this lack of knowledge by systematically varying the chemical synthesis of the nanoparticles and analyzing how this affects the resulting atomic structure and, in turn, the optical and electronic properties. These discoveries could lead to new materials for use in light emitting diodes, lasers, solar energy conversion, catalysis, chemical/biochemical sensors, and biomedical imaging. This support will also be used to help recruit and train underrepresented and first generation undergraduate students through summer workshops to be held at the University of Arkansas.Under this award, Drs. Heyes, Coridan and their students will study copper-(zinc)-indium chalcogenide and silver-(zinc)-indium chalcogenide nanoparticle quantum dots (QDs) in which the distribution and local environment of the CuInE2 or AgInE2 (E = S, Se, Te) emitting sites is varied by the synthesis conditions. Zinc is known to ion exchange with copper and indium in the CuInE2 lattice to form alloyed Cu(Zn)InE2 QDs or with silver and indium in the AgInE2 lattice to form alloyed Ag(Zn)InE2 QDs. Two important gaps in our understanding of these types of QDs are (i) What is the mechanism underlying this ion-exchange/alloying and (ii) what is the relationship between the structure resulting from the specific reaction conditions and the electronic structure/exciton decay pathways. This research will set out to examine these knowledge gaps by systematically synthesizing homogeneously alloyed and heterogeneous/gradient alloyed QDs. Particular attention will be paid to the heterogeneity in optical emission properties at the single nanoparticle level and in correlating these properties to atomic level structural information obtained using X-ray diffraction and spectroscopy techniques.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.