Gold–thiol contacts are ubiquitous across the physical and biological sciences in connecting organic molecules to surfaces. When thiols bind to gold in self-assembled monolayers (SAMs) the fate of the hydrogen remains a subject of profound debate—with implications for our understanding of their physical properties, spectroscopic features and formation mechanism(s). Exploiting measurements of the transmission through a molecular junction, which is highly sensitive to the nature of the molecule–electrode contact, we demonstrate here that the nature of the gold–sulfur bond in SAMs can be probed via single-molecule conductance measurements. Critically, we find that SAM measurements of dithiol-terminated molecular junctions yield a significantly lower conductance than solution measurements of the same molecule. Through numerous control experiments, conductance noise analysis and transport calculations based on density functional theory, we show that the gold–sulfur bond in SAMs prepared from the solution deposition of dithiols does not have chemisorbed character, which strongly suggests that under these widely used preparation conditions the hydrogen is retained.
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The data that support the findings were acquired using a custom instrument controlled by custom software (Igor Pro, Wavemetrics). The software is available from the corresponding author upon reasonable request.
The data that support the findings of this study not included in the Supplementary Information are available from the corresponding author upon reasonable request.
Nuzzo, R. G. & Allara, D. L. Adsorption of bifunctional organic disulfides on gold surfaces. J. Am. Chem. Soc. 105, 4481–4483 (1983).
Bain, C. D. & Whitesides, G. M. Molecular-level control over surface order in self-assembled monolayer films of thiols on gold. Science 240, 62–63 (1988).
Love, J. C., Estroff, L. A., Kriebel, J. K., Nuzzo, R. G. & Whitesides, G. M. Self-assembled monolayers of thiolates on metals as a form of nanotechnology. Chem. Rev. 105, 1103–1170 (2005).
Hakkinen, H. The gold–sulfur interface at the nanoscale. Nat. Chem. 4, 443–455 (2012).
Bain, C. D., Biebuyck, H. A. & Whitesides, G. M. Comparison of self-assembled monolayers on gold: coadsorption of thiols and disulfides. Langmuir 5, 723–727 (1989).
Cossaro, A. et al. X-ray diffraction and computation yield the structure of alkanethiols on gold(111). Science 321, 943–946 (2008).
Walczak, M. M., Alves, C. A., Lamp, B. D. & Porter, M. D. Electrochemical and X-ray photoelectron spectroscopic evidence for differences in the binding sites of alkanethiolate monolayers chemisorbed at gold. J. Electroanal. Chem. 396, 103–114 (1995).
Poirier, G. E. & Pylant, E. D. The self-assembly mechanism of alkanethiols on Au(111). Science 272, 1145–1148 (1996).
Nuzzo, R. G., Zegarski, B. R. & Dubois, L. H. Fundamental studies of the chemisorption of organosulfur compounds on gold(111). Implications for molecular self-assembly on gold surfaces. J. Am. Chem. Soc. 109, 733–740 (1987).
Vericat, C., Vela, M. E., Benitez, G., Carro, P. & Salvarezza, R. C. Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system. Chem. Soc. Rev. 39, 1805–1834 (2010).
Pensa, E. et al. The chemistry of the sulfur–gold interface: in search of a unified model. Acc. Chem. Res. 45, 1183–1192 (2012).
Reimers, J. R., Ford, M. J., Marcuccio, S. M., Ulstrup, J. & Hush, N. S. Competition of van der Waals and chemical forces on gold–sulfur surfaces and nanoparticles. Nat. Rev. Chem. 1, 0017 (2017).
Jadzinsky, P. D., Calero, G., Ackerson, C. J., Bushnell, D. A. & Kornberg, R. D. Structure of a thiol monolayer-protected gold nanoparticle at 1.1 Å resolution. Science 318, 430–433 (2007).
Xu, B. & Tao, N. J. Measurement of single-molecule resistance by repeated formation of molecular junctions. Science 301, 1221–1223 (2003).
Zhou, C., Muller, C., Burgin, T., Tour, J. & Reed, M. Conductance of a molecular junction. Science 278, 252–254 (1997).
Haiss, W. et al. Redox state dependence of single molecule conductivity. J. Am. Chem. Soc. 125, 15294–15295 (2003).
Li, C. et al. Charge transport in single Au | alkanedithiol | Au junctions: coordination geometries and conformational degrees of freedom. J. Am. Chem. Soc. 130, 318–326 (2008).
Inkpen, M. S. et al. New insights into single-molecule junctions using a robust, unsupervised approach to data collection and analysis. J. Am. Chem. Soc. 137, 9971–9981 (2015).
Haiss, W. et al. Anomalous length and voltage dependence of single molecule conductance. Phys. Chem. Chem. Phys. 11, 10831–10838 (2009).
Venkataraman, L., Klare, J. E., Nuckolls, C., Hybertsen, M. S. & Steigerwald, M. L. Dependence of single-molecule junction conductance on molecular conformation. Nature 442, 904–907 (2006).
Inkpen, M. S., Leroux, Y. R., Hapiot, P., Campos, L. M. & Venkataraman, L. Reversible on-surface wiring of resistive circuits. Chem. Sci. 8, 4340–4346 (2017).
Everret, D. H. Definitions, terminology and symbols in colloid and surface chemistry. Pure Appl. Chem. 31, 579–638 (1972).
Zang, Y. et al. Electronically transparent Au–N bonds for molecular junctions. J. Am. Chem. Soc. 139, 14845–14848 (2017).
Park, Y. S. et al. Contact chemistry and single-molecule conductance: a comparison of phosphines, methyl sulfides, and amines. J. Am. Chem. Soc. 129, 15768–15769 (2007).
Cheng, Z. L. et al. In situ formation of highly conducting covalent Au–C contacts for single-molecule junctions. Nat. Nanotechnol. 6, 353–357 (2011).
Hybertsen, M. S. & Venkataraman, L. Structure–property relationships in atomic-scale junctions: histograms and beyond. Acc. Chem. Res. 49, 452–460 (2016).
Quek, S. Y. et al. Amine−gold linked single-molecule circuits: experiment and theory. Nano Lett. 7, 3477–3482 (2007).
Paulsson, M., Krag, C., Frederiksen, T. & Brandbyge, M. Conductance of alkanedithiol single-molecule junctions: a molecular dynamics study. Nano Lett. 9, 117–121 (2009).
Kim, Y.-H., Kim, H. S., Lee, J., Tsutsui, M. & Kawai, T. Stretching-induced conductance variations as fingerprints of contact configurations in single-molecule junctions. J. Am. Chem. Soc. 139, 8286–8294 (2017).
Rascón-Ramos, H., Artés, J. M., Li, Y. & Hihath, J. Binding configurations and intramolecular strain in single-molecule devices. Nat. Mater. 14, 517–522 (2015).
Adak, O. et al. Flicker noise as a probe of electronic interaction at metal–single molecule interfaces. Nano Lett. 15, 4143–4149 (2015).
Brandbyge, M., Mozos, J.-L., Ordejón, P., Taylor, J. & Stokbro, K. Density-functional method for nonequilibrium electron transport. Phys. Rev. B 65, 165401 (2002).
Koentopp, M., Burke, K. & Evers, F. Zero-bias molecular electronics: exchange-correlation corrections to Landauer’s formula. Phys. Rev. B 73, 121403 (2006).
Quek, S. Y. et al. Amine–gold linked single-molecule circuits: experiment and theory. Nano Lett. 7, 3477–3482 (2007).
Quek, S. Y., Choi, H. J., Louie, S. G. & Neaton, J. B. Length dependence of conductance in aromatic single-molecule junctions. Nano Lett. 9, 3949–3953 (2009).
Hybertsen, M. S. et al. Amine-linked single-molecule circuits: systematic trends across molecular families. J. Phys. Condens. Matter 20, 374115 (2008).
Widrig, C. A., Chung, C. & Porter, M. D. The electrochemical desorption of n-alkanethiol monolayers from polycrystalline Au and Ag electrodes. J. Electroanal. Chem. Interfacial Electrochem. 310, 335–359 (1991).
Angelova, P. et al. Chemisorbed monolayers of corannulene penta-thioethers on gold. Langmuir 29, 2217–2223 (2013).
Piotrowski, P. et al. Self-assembly of thioether functionalized fullerenes on gold and their activity in electropolymerization of styrene. RSC Adv. 5, 86771–86778 (2015).
Noh, J. et al. High-resolution STM and XPS studies of thiophene self-assembled monolayers on Au(111). J. Phys. Chem. B 106, 7139–7141 (2002).
Zhong, C.-J., Brush, R. C., Anderegg, J. & Porter, M. D. Organosulfur monolayers at gold surfaces: reexamination of the case for sulfide adsorption and implications to the formation of monolayers from thiols and disulfides. Langmuir 15, 518–525 (1998).
He, J. et al. Measuring single molecule conductance with break junctions. Faraday Discuss. 131, 145–154 (2006).
Haiss, W. et al. Impact of junction formation method and surface roughness on single molecule conductance. J. Phys. Chem. C 113, 5823–5833 (2009).
Li, X. et al. Conductance of single alkanedithiols: conduction mechanism and effect of molecule−electrode contacts. J. Am. Chem. Soc. 128, 2135–2141 (2006).
Burgi, T. Properties of the gold–sulphur interface: from self-assembled monolayers to clusters. Nanoscale 7, 15553–15567 (2015).
Hasan, M., Bethell, D. & Brust, M. The fate of sulfur-bound hydrogen on formation of self-assembled thiol monolayers on gold: 1H NMR spectroscopic evidence from solutions of gold clusters. J. Am. Chem. Soc. 124, 1132–1133 (2002).
Crudden, C. M. et al. Ultra stable self-assembled monolayers of N-heterocyclic carbenes on gold. Nat. Chem. 6, 409–414 (2014).
Lavrich, D. J., Wetterer, S. M., Bernasek, S. L. & Scoles, G. Physisorption and chemisorption of alkanethiols and alkyl sulfides on Au(111). J. Phys. Chem. B 102, 3456–3465 (1998).
Xie, Z., Bâldea, I., Smith, C. E., Wu, Y. & Frisbie, C. D. Experimental and theoretical analysis of nanotransport in oligophenylene dithiol junctions as a function of molecular length and contact work function. ACS Nano 9, 8022–8036 (2015).
Li, H. et al. Extreme conductance suppression in molecular siloxanes. J. Am. Chem. Soc. 139, 10212–10215 (2017).
Li, H. et al. Electric field breakdown in single molecule junctions. J. Am. Chem. Soc. 137, 5028–5033 (2015).
Kirihara, M. et al. A mild and environmentally benign oxidation of thiols to disulfides. Synthesis 2007, 3286–3289 (2007).
Forward, J. M., Bohmann, D., Fackler, J. P. & Staples, R. J. Luminescence studies of gold(i) thiolate complexes. Inorg. Chem. 34, 6330–6336 (1995).
Monzittu, F. M. et al. Different emissive properties in dithiolate gold(i) complexes as a function of the presence of phenylene spacers. Dalton. Trans. 43, 6212–6220 (2014).
Atsushi, S. et al. Solvent diversity in the preparation of alkanethiol-capped gold nanoparticles. An approach with a gold(i) thiolate complex. Chem. Lett. 39, 319319–319321 (2010).
Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 78, 1396–1396 (1997).
José, M. S. et al. The SIESTA method for ab initio order-N materials simulation. J. Phys. Condens. Matter 14, 2745–2779 (2002).
We acknowledge discussions with M. L. Steigerwald, G. Lovat, T. Albrecht, Y. R. Leroux and P. Hapiot, and thank M. C. Buzzeo for the use of electrochemical equipment. This research was supported primarily by a Marie Skłodowska Curie Global Fellowship (M.S.I., MOLCLICK: 657247) within the Horizon 2020 Programme. This work was supported in part by the National Science Foundation grants DMR-1507440 and DMR-1807580. The computational work was supported by the US Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under contract no. DE–AC02–05CH11231, within the Theory FWP. This work was also supported by the Molecular Foundry through the US Department of Energy, Office of Basic Energy Sciences, under the same contract number. Portions of the computational work were performed at the National Energy Research Scientific Computing Center.
The authors declare no competing interests.
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Inkpen, M.S., Liu, Z., Li, H. et al. Non-chemisorbed gold–sulfur binding prevails in self-assembled monolayers. Nat. Chem. 11, 351–358 (2019). https://doi.org/10.1038/s41557-019-0216-y
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