CREST-Postdoctoral Research Fellowship: The Effects of Strong Confinement in the Ultrasmall Nanoparticle Regime on the Mechanism and Charge Transfer Rates in CdSe QDs

Webster, Megan, New York NY

Investigators

Abstract

The Centers of Research Excellence in Science and Technology-Postdoctoral Research Fellowship (CREST-PRF) track within the CREST program supports beginning CREST Center investigators with significant potential and provides them with training and research experiences that will broaden perspectives, facilitate interdisciplinary interactions and establish them in positions of leadership within the scientific community. This CREST-PRF project is aligned with the research focus of the CREST Center for Interface Design and Engineered Assembly of Low Dimensional Structures (CREST-IDEALS) at the City College of New York. The goal of this research is understanding the optoelectronic properties of ultrasmall CdSe quantum dots (QDs). Quantum Dots are on the nano scale which results in optical and electronic properties that are different from larger particles. QDs have the potential to tap into the enormous potential of Solar Energy. The proposed work intends to investigate ultrasmall quantum dots synthesized by the researcher with x-ray spectroscopy and transmission electron microscopy techniques. These techniques will allow the researcher to more fully understand the ability of ultrasmall quantum dots to transfer charge and formulate a theoretical model to explain the behavior. This analysis will allow the incorporation of ultrasmall QDs into solar cell designs. Ultrasmall quantum dots display broad emission despite their monodispersity. Photoluminescence excitation (PLE) will allow for the investigation of which excitation wavelengths can cause the emission of a specified wavelength. Preliminary PLE data indicates that there are states within the bandgap to which direct absorption is possible. PLE data gathered from Qds will be compared to time resolved photoluminescence data (TRPL). The TRPL allows one to detect multiexponential decay systems, indicating that such systems have multiple lifetimes. Two acceptor species will be investigated with x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The acceptor species include a) molecules (ligands) of both e- donating and e- accepting character and b) carbon nanotubes (CNTs). The molecules will begin with investigating alkylthiols of varying chain length and benzene sulfonic monohydrate (BSAM). Qds will be embedded within CNTs as a means of not only charge transfer enhancement but also QD alignment for connectivity between QDs as well. 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.