1105185 Li

1. Colloidal Graphene Quantum Dots for Energy ApplicationsLiang-shi Li, Indiana University, DMR 1105185 We have studied the charge transfer involving the colloidal graphene quantum dots (GQDs) for solar cell applications, and have investigated the effects of metal nanoparticle attachment as well as heteroatom doping on the energy relaxation dynamics of the GQDs. The most exciting results we obtained in 2012 are the observation of hot electron transfer from the GQDs and the synthetic method to dope the GQDs with nitrogen atoms. The former, achieved in collaboration with Prof. Xiaoyang Zhu’s lab at Univ. of Texas, has important implications in making solar cells to overcome the ~ 31% limit imposed on single-junction solar cells. The latter opens varieties of possibilities to tune the electronic properties of the GQDs. Presence of the N atoms in GQD 1 significantly alters its energy relaxation pathways. 1 and 2 have similar absorption spectra, but 2 is highly fluorescent whereas 1 doesn’t have any detectable emission.

2. Colloidal Graphene Quantum Dots for Energy ApplicationsLiang-shi Li, Indiana University, DMR 1105185 Broader impacts An overall goal of our research is to develop new ways for renewable use of carbon for energy. The N-doped GQDs (1), for example, are interesting for energy relaxation studies. We also found that they could catalyze the oxygen reduction reaction (ORR), a key reactions in fuels cells. Its well-defined structure provides a unique model system to understand ORR catalyzed by carbon as a replacement for commonly use Pt. Meanwhile, we have hosted a female high-school student to participate in our interdisciplinary research. In the past Summer, we also hosted Prof. Huajun Fan from Texas Prairie View A&M University, a historically black college, to stay with us for collaborative research. The goal is to develop common research interest and to open channels to recruit minority students into our PhD program. Cyclovoltammetry curves of 1 on a glassy-carbon electrode measured in a N2- and an O2-saturated 0.1 M KOH solution. The peak at -0.3 corresponds to the reduction of oxygen catalyzed by the N-doped GQDs. The onset potential is approximately the same as that with Pt/C, demonstrating the excellent activity of the GQDs as an ORR catalyst. This work was done in collaboration with Prof. Liming Dai at Case Western Reserve University.