Enantiospecificity of Chiral Pt Nanostructures Grown on Chiral SrTiO3 Surfaces
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu14289477462021-08-03T06:30:02Z Enantiospecificity of Chiral Pt Nanostructures Grown on Chiral SrTiO3 Surfaces Yuk, Simuck Francis Chemical Engineering Chiral Surfaces Adsorption Density Functional Theory Enantiospecificity Often, obtaining an enantiopure form of drugs is important in pharmaceutical industry since the biomolecules exist strictly as homochiral. Drugs based on undesirable form of enantiomer could bring disastrous consequences to their users. Naturally chiral metal surfaces, obtained from cleaving bulk metals, have shown to possess enantiospecificity (i.e. ability to distinguish enantiomers). The source of enantiospecificity of such surfaces is the presence of under-coordinated kink sites along the step edges. However, there are two primary drawbacks to chiral metal surfaces: (1) they present a relatively homogenous environment of a single metal which reduces the observed enantiospecficity, and (2) are expensive to produce as single-crystal surfaces.To further optimize and tailor the enantiospecificity of chiral surfaces, we study the enantiospecificity of Pt nanostructures grown on the step-kink edges of chiral SrTiO3 surfaces. Density functional theory (DFT), a quantum mechanics-based modeling method, is our primary tool to characterize the enantiospecificity of oxide-supported metal structures. The heterogeneous electronic structure of underlying oxide substrate is expected to optimize the enantiospecificity of grown metal nanostructures. Pt was chosen to grow metal nanostructures because of its close lattice match with SrTiO3.As a first effort to understand the electronic effects of oxide substrate, we studied the CO adsorption on the Pt monolayers (MLs) supported on the SrTiO3(100). We found that the nature of deposited Pt is heavily dependent on its underlying oxide atoms at the 1 ML of Pt. The different hybridization between Pt d valence and CO orbitals is mainly responsible for these oxide-dependent behaviors of deposited Pt. Such oxide effects diminish after depositing more than 2 ML of Pt on the SrTiO3 support.Next, the enantiospecific adsorption of R- and S-methyl lactate was investigated on the chiral Cu(643) surface. DFT-derived pre-factors along with desorption energies predict peak temperatures that are in relatively good agreement with temperature programmed desorption (TPD) studies for molecular desorption of methyl lactate from Cu(643) surface. The global minimum of S-methyl lactate is more firmly bound by 9.5 kJ/mol over its enantiomer on the Cu(643) surface, with a peak temperature difference of 25 K versus an experimental value of 12 K.We also studied the enantiospecific adsorption of R- and S-fluoroaminomethoxy on the Cu, Pd, and Pt(874)S surfaces. The different geometry and enantiospecific energy difference of global minima were observed when varying the type of surface metal. To understand the variation in enantiospecificity, the local binding model was adopted to analyze the adsorption energetics of chiral molecule. The model shows that large enantiospecificity occurs when each local bonding of functional group is distinctive between R- and S-global minima.Finally, the enantiospecific adsorption of R- and S-methyl lactate was studied on Pt thin films supported on chiral SrTiO3(643). Distinctive degree of enantiospecificity was obtained due to the different arrangement of underlying oxide atoms at the 1 and 2 ML of Pt, indicating the possibility of tailoring the enantiospecificity of deposited Pt metal structures. Again, such oxide effects subside after depositing more than 2 ML of Pt on the oxide support. 2015-05-19 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1428947746 http://rave.ohiolink.edu/etdc/view?acc_num=osu1428947746 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
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language |
English |
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NDLTD |
topic |
Chemical Engineering Chiral Surfaces Adsorption Density Functional Theory Enantiospecificity |
spellingShingle |
Chemical Engineering Chiral Surfaces Adsorption Density Functional Theory Enantiospecificity Yuk, Simuck Francis Enantiospecificity of Chiral Pt Nanostructures Grown on Chiral SrTiO3 Surfaces |
author |
Yuk, Simuck Francis |
author_facet |
Yuk, Simuck Francis |
author_sort |
Yuk, Simuck Francis |
title |
Enantiospecificity of Chiral Pt Nanostructures Grown on Chiral SrTiO3 Surfaces |
title_short |
Enantiospecificity of Chiral Pt Nanostructures Grown on Chiral SrTiO3 Surfaces |
title_full |
Enantiospecificity of Chiral Pt Nanostructures Grown on Chiral SrTiO3 Surfaces |
title_fullStr |
Enantiospecificity of Chiral Pt Nanostructures Grown on Chiral SrTiO3 Surfaces |
title_full_unstemmed |
Enantiospecificity of Chiral Pt Nanostructures Grown on Chiral SrTiO3 Surfaces |
title_sort |
enantiospecificity of chiral pt nanostructures grown on chiral srtio3 surfaces |
publisher |
The Ohio State University / OhioLINK |
publishDate |
2015 |
url |
http://rave.ohiolink.edu/etdc/view?acc_num=osu1428947746 |
work_keys_str_mv |
AT yuksimuckfrancis enantiospecificityofchiralptnanostructuresgrownonchiralsrtio3surfaces |
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1719437907268206592 |