| AVS 64th International Symposium & Exhibition | |
| Surface Science Division | Friday Sessions |
| Session SS+HC-FrM |
| Session: | Recent Advances in the Chemistry and Physics of Interfaces |
| Presenter: | Soham Dutta, Carnegie Mellon University |
| Authors: | S. Dutta, Carnegie Mellon University A. Gellman, Carnegie Mellon University, W.E. Scott Institute for Energy Innovation |
| Correspondent: | Click to Email |
Chirality is a geometric property and refers to existence of handedness in any system. While chirality is ubiquitous in nature across all spatial scales, chirality at the molecular level is of special interest given the homochirality of biomolecules such as DNA and the amino acids that are the molecular basis of life. Increasingly, fundamental research is focused on studying chiral molecules adsorbed on surfaces given their applications in enantioselective chemical phenomena such as heterogeneous catalysis. While many examples of 2D chiral assembly of molecules have been studied over the years, fundamental questions about chiral aggregation on surfaces remain unanswered. One such question is whether enantiomers deposited on a surface aggregate into domains containing enantiomers of the same chirality (homochiral) or domains containing both enantiomers (heterochiral).
In this study, we have used a combination of Temperature Programmed Reaction Spectroscopy (TPRS) and isotopic labelling to study the decomposition kinetics and aggregation behavior of aspartic acid (Asp) enantiomers on Cu surfaces. The ionization state of adsorbed Asp monolayer was determined to be anionic using X-ray photoelectron spectroscopy. Next, using isotopic labelling, we have identified Asp decomposition mechanism in greater detail than possible for any comparable size adsorbate on a metal surface. It was found that Asp follows a multi-step decomposition process to form CO2 and acetonitrile. Then, the first observed enantiospecific decomposition of Asp enantiomers is reported on naturally chiral Cu(643)R&S. Lastly, equilibrium adsorption experiments of Asp enantiomer mixtures on copper surfaces were performed and Asp enantiomers was found to aggregate on the surface. A cluster-adsorption model was developed to quantify the free energy change and equilibrium constants of enantiomer aggregation in 2D for the first time.
The combination of a surface explosion pathway with a naturally chiral catalytic surface leads to high enantiospecificity of Asp decomposition. This non-linear explosive decomposition pathway, coupled with the availability of multiple isotopomers is exploited to quantitatively probe aggregation behavior of aspartic acid with unprecedented detail.