Adsorption of Benzene on Coinage Metals: A Theoretical Analysis Using Wavefunction-Based Methods

Spin- and angle-resolved photoemission spectroscopy study of heptahelicene layers on Cu(111) surfaces

It has been demonstrated previously that electrons interact differently with chiral molecules depending on their polarization. For enantiomeric pure monolayers of heptahelicene, opposite asymmetries in spin polarization were reported and attributed to the so-called chirality-induced spin selectivity effect. However, these promising proof-of-concept photoemission experiments lack the angular and energy resolution that could provide the necessary insights into the mechanism of this phenomenon. In order to fill in the missing gaps, we provide a detailed spin- and angle-resolved photoemission spectroscopy study of heptahelicene layers on a Cu(111) substrate. Throughout the large accessible energy and angle range, no chirality induced spin asymmetry in photoemission could be observed. Possible reasons for the absence of signatures of the spin-dependent electron transmission through the chiral molecular layer are briefly discussed.

Interactions between glucosides of the tip of the S1 subunit of SARS-CoV-2 spike protein and dry and wet surfaces of CuO and Cu-A model for the surfaces of coinage metals

Despite their importance there is little knowledge at the atomic scale on the interactions between fragments of SARS-CoV-2 and inorganic materials. Such knowledge is important to understand the survival of the virus at surfaces and for the development of antiviral materials. Here is reported a study of the interactions between glucoside monomers of the tip of the S1 subunit of SARS-CoV-2 spike protein with dry and wet surfaces of CuO and Cu, performed with dispersion corrected density functional theory—DFT. The three glucoside monomers that constitute the tip of S1: 6VSB, 6VXX and 6X6P, were adsorbed onto dry and wet CuO(111) and Cu(110) with different orientations and surface alignments.

There are large differences—of up to 1.3 eV—in binding energies between these monomers and the surfaces. These differences depend on: the type of surface; if the surface is wet or dry; if the glucosidic O-atom points towards or away from the surfaces; and to a smaller extent on the surface alignment of the monomers. All monomers bind strongly to the surfaces via molecular adsorption that does not involve bond breaking in the monomers at this stage. 6VSB has the larger adsorption energies—that reach 2.2 eV—due to its larger dipole moment. Both materials bind the monomers more strongly when their surfaces are dry. At Cu(110) the bonds are on average 1 eV stronger when the surface is dry when compared to wet. The difference between dry and wet CuO(111) is smaller, in the order of 0.2 eV. Overall, it is here shown that the stability of the monomers of the tip of the spike protein of the virus is very different at different surfaces. For a given surface the larger binding energies in dry conditions could explain the differences in the surface stability of the spike protein depending on the presence of moisture.

Density functional theory with modified dispersion correction for metals applied to molecular adsorption on Pt(111)

We have performed density functional theory calculations using our modified DFT-D2 dispersion correction for metals to investigate adsorption of a range of molecules on Pt(111).

Theoretical study of the adsorption of benzene on coinage metals

The adsorption of benzene on the M(111), M(100) and M(110) surfaces of the coinage metals copper (M = Cu), silver (M = Ag) and gold (M = Au) is studied on the basis of density functional theory (DFT) calculations with an empirical dispersion correction (D3). Variants of the Perdew–Burke–Ernzerhof functionals (PBE, RPBE and RevPBE) in combination with different versions of the dispersion correction (D3 and D3(BJ)) are compared. PBE-D3, PBE-D3(BJ) and RPBE-D3 give similar results which exhibit a good agreement with experimental data. RevPBE-D3 and RevPBE-D3(BJ) tend to overestimate adsorption energies. The inclusion of three-center terms (PBE-D3(ABC)) leads to a slightly better agreement with the experiment in most cases. Vertical adsorbate–substrate distances are calculated and compared to previous theoretical results. The observed trends for the surfaces and metals are consistent with the calculated adsorption energies.

Silver nanoprism arrays coupled to functional hybrid films for localized surface plasmon resonance-based detection of aromatic hydrocarbons

We report the achievement of sensitive gas detection using periodic silver nanoprisms fabricated by a simple and low-cost lithographic technique. The presence of sharp tips combined with the periodic arrangement of the nanoprisms allowed the excitement of isolated and interacting localized surface plasmon resonances. Specific sensing capabilities with respect to aromatic hydrocarbons were achieved when the metal nanoprism arrays were coupled in the near field with functional hybrid films, providing a real-time, label-free, and reversible methodology. Ultra-high-vacuum temperature-programmed desorption measurements demonstrated an interaction energy between the sensitive film and analytes in the range of 55-71 kJ/mol. The far-field optical properties and the detection sensitivity of the sensors, modeled using a finite element method, were correlated to experimental data from gas sensing tests. An absorbance variation of 1.2% could be observed and associated with a theoretical increase in the functional film refractive index of ∼0.001, as a consequence to the interaction with 30 ppm xylene. The possibility of detecting such a small variation in the refractive index suggests the highly promising sensing capabilities of the presented technique.

Density Functional Theory with Modified Dispersion Correction for Metals Applied to Self-Assembled Monolayers of Thiols on Au(111)

Using sound physical principles we modify the DFT-D2 atom pairwise semiempirical dispersion correction to density functional theory to work for metallic systems and in particular self-assembled monolayers of thiols on gold surfaces. We test our approximation for two functionals PBE-D and revPBE-D for lattice parameters and cohesive energies for Ni, Pd, Pt, Cu, Ag, and Au, adsorption energies of CO on (111) surfaces of Pd, Pt, Cu, Ag, and Au, and adsorption energy of benzene on Ag(111) and Au(111). Agreement with experimental data is substantially improved. We apply the method to self-assembled monolayers of alkanethiols on Au(111) and find reasonable agreement for PBE-D and revPBE-D for both physisorption of n-alkanethiols as well as dissociative chemisorption of dimethyl disulfide as an Au-adatom-dithiolate complex. By modifying the C6 coefficient for Au, we obtain quantitative agreement for physisorption and chemisorption for both PBE-D and revPBE-D using the same set of parameters. Our results confirm that inclusion of dispersion forces is crucial for any quantitative analysis of the thiol and thiolate bonds to the gold surface using quantum chemical calculations.

Dehydrogenation of benzene on liquid Al100(+)

The reactions of benzene on Al100(+) have been investigated as a function of cluster temperature (300-1100 K) and relative kinetic energy (1-14 eV) by low-energy ion-beam methods and mass spectrometry. Benzene chemisorbs on both solid and liquid aluminum clusters to generate Al100C6D6(+). A series of Al(100-n)(+) (n = 1, 2, 3, ...) products was also observed. As the cluster temperature was raised above the melting temperature of Al100(+), the Al100C6D6(+) product dehydrogenates to form Al100C6D4(+), Al100C6D2(+), and Al100C6(+). The degree of dehydrogenation was measured as a function of temperature. Very little Al100C6D2(+) was observed, suggesting that the losses of the second and third D2 molecules are coordinated.

Cooperative modulation of electronic structures of aromatic molecules coupled to multiple metal contacts

We use cryogenic scanning tunneling microscopy and spectroscopy and density-functional theory calculations to inspect the modulation of electronic states of aromatic molecules. The molecules are self-assembled on a Cu(111) surface forming molecular networks in which the molecules are in different contact configurations, including laterally coupled to different numbers of coordination bonds and vertically adsorbed at different heights above the substrate. We quantitatively analyze the molecular states and find that a delocalized empty molecular state is modulated by these multiple contacts in a cooperative manner: its energy is down shifted by ∼ 0.16 eV for each additional lateral contact and by ∼ 0.1 eV as the vertical molecule-surface distance is reduced by 0.1 Å in the physisorption regime. We also report that in a molecule-metal-molecule system the bridging metal can mediate the electronic states of the two molecules.

Density-functional theory with screened van der Waals interactions for the modeling of hybrid inorganic-organic systems

The electronic properties and the function of hybrid inorganic-organic systems (HIOS) are intimately linked to their interface geometry. Here we show that the inclusion of the many-body collective response of the substrate electrons inside the inorganic bulk enables us to reliably predict the HIOS geometries and energies. This is achieved by the combination of dispersion-corrected density-functional theory (the DFT+ van der Waals approach) [Phys. Rev. Lett. 102, 073005 (2009)], with the Lifshitz-Zaremba-Kohn theory for the nonlocal Coulomb screening within the bulk. Our method yields geometries in remarkable agreement (≈0.1 Å) with normal incidence x-ray standing wave measurements for the 3, 4, 9, 10-perylene-tetracarboxylic acid dianhydride (C(24)O(6)H(8), PTCDA) molecule on Cu(111), Ag(111), and Au(111) surfaces. Similarly accurate results are obtained for xenon and benzene adsorbed on metal surfaces.