One of Joseph’s last submitted papers, “Tunable Mid-Gap Excitations in Co²⁺-doped ZnO Quantum Dots: Effect of Excited State Structural Relaxation” has been accepted to the Journal of Physical Chemistry C. The paper studies midgap excitations within Co²⁺-doped ZnO quantum dots using Density Functional Theory.

Ongoing collaborative work with Professors Daniel R. Gamelin and David S. Ginger at the University of Washington have resulted in two new publications: “Direct Measurement of Acceptor Group Localization on Donor–Acceptor Polymers Using Resonant Auger Spectroscopy” and “Ferromagnetic excited-state Mn²⁺ dimers in Zn_1−xMn_xSe quantum dots observed by time-resolved magnetophotoluminescence“.

In the first publication, Phu Nguyen performed density functional calculations to investigate the electronic structure of the LUMO of PCPDTBT and PCDTBT, two similar donor/acceptor-type polymers. These materials are of interest for application in organic photovoltaic devices.

In the second publication, Joseph May performed density functional calculations on ZnSe nanocrystals doped with Mn²⁺ ions to elucidated the microscopic orbital exchange interactions that give rise to ferromagnetic coupling within photoexcited Mn²⁺—Mn²⁺ dimers.

Bo Peng’s paper titled “Effects of Crystallographic and Shape Anisotropies on Dopant-Carrier Exchange Interactions in Magnetic Semiconductor Quantum Dots” is now available online in The Journal of Physical Chemistry C. This paper examines the role of nanocrystal shape and crystalline anisotropy on carrier-mediated magnetism in diluted magnetic semiconductor nanocrystals using density functional theory and analytical perturbation theory.

David Lingerfelt’s paper titled “Dynamical Investigations of Inhomogenous Vibrational Broadening in Diluted Magnetic Semiconductor Nanocrystals” was just accepted for publication in the Journal of Physical Chemistry C. This is David’s first publication in the Li group and his first-ever publication in a peer-reviewed journal. Congratulations David! The paper presents a method for simulating finite-temperature, inhomogenously broadened electronic absorption spectra of large systems with high densities of states and applies the method to the problem of peak broadening in dilute magnetic semiconductor nanocrystals. The approach accurately captures the temperature-dependent inhomogeneous broadening of the charge transfer transitions and resolves previous inconsistencies between theory and experiment. The paper is now available online.

Congratulations, Joseph! Joseph is one of five recipients of the Chemical Computing Group (CCG) and the American Chemical Society’s (ACS) Division of Computers in Chemistry (COMP) Excellence Award for the Fall 2013 ACS National Meeting in Indiana. Joseph will receive financial support to present his poster titled, Theoretical investigation of ion diffusion pathways in II-VI semiconductor nanocrystals, during the COMP poster session at the ACS meeting.

Congratulations to Bo Peng and Jeremy Lehner for passing the departmental second-year exam. Bo presented his work on anisotropic exchange splittings in transition-metal-doped II-VI semiconducting nanocrystals. Jeremy presented his work on geometry optimization, discussing a modification to the rational function optimization for transition state optimizations.

The Li group welcomes Sara Tweedy, an undergraduate from Harvey Mudd College, to the group. Sara joins the group as part of the Amgen Scholars Summer Research Program in Science and Biotechnology. The program “provides hundreds of selected undergraduate students with the opportunity to engage in hands-on research experience at some of the nation’s leading educational institutions.” During the 9-week program, Sara will study the effects of charging and counterions on the electronic structure of CdSe and ZnO quantum dots.

Congratulations to Joseph May for passing his third-year general examination. Joseph presented his work “Manipulating the Optical and Magnetic Properties of Zinc Oxide Quantum Dots”. Joseph is now a doctoral candidate and is free from worrying about exams until he defends his dissertation in a couple of years.

Joseph May and Ryan McMorris’ paper, “Ferromagnetism in p-Type Manganese-Doped ZnO Quantum Dots”, which describes how nitrogen dopants affect the magnetic ordering of manganese unpaired spins in zinc oxide quantum dots, was just accepted into the Journal of Physical Chemistry Letters. The “Just Accepted Manuscript” is available here.

Bo Peng’s paper, “Theoretical Evaluation of Spin-Dependent Auger De-Excitation in Mn2+-Doped Semiconductor Nanocrystals,” which describes Auger de-excitation process in Mn2+-doped CdS quantum dots, was just accepted into the Journal of Physical Chemistry C. The “Just Accepted Manuscript” is available here.