The supramolecular structure and van der Waals interactions affect the electronic structure of ferrocenyl-alkanethiolate SAMs on gold and silver electrodes
journal contribution
posted on 2025-12-10, 05:39 authored by Liang Cao, Li Yuan, Ming Yang, Nisachol Nerngchamnong, Damien Thompson, Xiaojiang Yu, Dongchen QiDongchen Qi, Christian A NijhuisUnderstanding the influence of structural properties on the electronic structure will pave the way for optimization of charge transport properties of SAM devices. In this study, we systematically investigate the supramolecular and electronic structures of ferrocene (Fc) terminated alkanethiolate (SCnFc) SAMs on both Au and Ag substrates with n = 1-15 by using a combination of synchrotron based near edge X-ray absorption spectroscopy (NEXAFS), photoemission spectroscopy (PES), and density functional theory (DFT) calculations. Odd-even effects in the supramolecular structure persist over the entire range of n = 1-15, which, in turn, explain the odd-even effects in the onset energy of the highest occupied molecular (HOMO) orbital. The orientation of the Fc moieties and the strength of Fc-substrate coupling, which both depend on n, affects the work function (WF). The variation of WF shows an odd-even effect in the weak electrode-Fc coupling regime for n ≥ 8, whereas the odd-even effect diminishes for n < 8 due to hybridization between Fc and the electrode (n < 3) or van der Waals (vdW) interactions between Fc and the electrode (n = 3-7). These results confirm that subtle changes in the supramolecular structure of the SAMs cause significant electronic changes that have a large influence on device properties.<p></p>
Funding
LC acknowledges support from the National Key Research and Development Program of China (Grant No. 2017YFA0402900), the National Natural Science Foundation of China (Grant No. 11574317 and 21503233), and Anhui Provincial Natural Science Foundation (Grant No. 1608085MA07). We acknowledge the Minister of Education (MOE) for supporting this research under award no. MOE2015-T2-2-134. Prime Minister's Office, Singapore under its Medium sized centre program is also acknowledged for supporting this research. DQ acknowledges the support of the Australian Research Council (FT160100207). XY acknowledges NUS core support C-380-003-003-001. DT acknowledges Science Foundation Ireland (SFI) for support under Grant number 15/CDA/3491 and for computing resources at the SFI/Higher Education Authority Irish Center for High-End Computing (ICHEC). The authors acknowledge the Singapore Synchrotron Light Source, a National Research Infrastructure under the National Research Foundation Singapore, for providing the facility necessary for conducting the research.
National Key Research and Development Program of China | 2017YFA0402900
Anhui Provincial Natural Science Foundation | 1608085MA07
Minister of Education (MOE) | MOE2015-T2-2-134
Prime Minister's Office, Singapore under its Medium sized centre program
NUS | C-380-003-003-001
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