Browsing by Author "Corni, Stefano"

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    Chirality-Specific Unidirectional Rotation of Molecular Motors on Cu(111)
    (American Chemical Society, 2023) Schied, Monika; Prezzi, Deborah; Liu, Dongdong; Kowarik, Stefan; Jacobson, Peter A.; Corni, Stefano; Tour, James M.; Grill, Leonhard; Smalley Institute for Nanoscale Science and Technology; Welch Institute for Advanced Materials; NanoCarbon Laboratory
    Molecular motors have chemical properties that enable unidirectional motion, thus breaking microscopic reversibility. They are well studied in solution, but much less is known regarding their behavior on solid surfaces. Here, single motor molecules adsorbed on a Cu(111) surface are excited by voltages pulses from an STM tip, which leads to their rotation around a fixed pivot point. Comparison with calculations shows that this axis results from a chemical bond of a sulfur atom in the chemical structure and a metal atom of the surface. While statistics show approximately equal rotations in both directions, clockwise and anticlockwise, a detailed study reveals that these motions are enantiomer-specific. Hence, the rotation direction of each individual molecule depends on its chirality, which can be determined from STM images. At first glance, these dynamics could be assigned to the activation of the motor molecule, but our results show that this is unlikely as the molecule remains in the same conformation after rotation. Additionally, a control molecule, although it lacks unidirectional rotation in solution, also shows unidirectional rotation for each enantiomer. Hence, it seems that the unidirectional rotation is not specifically related to the motor property of the molecule. The calculated energy barriers for motion show that the propeller-like motor activity requires higher energy than the simple rotation of the molecule as a rigid object, which is therefore preferred.
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    Energy Transfer to Molecular Adsorbates by Transient Hot Electron Spillover
    (Amerian Chemical Society, 2023) Vanzan, Mirko; Gil, Gabriel; Castaldo, Davide; Nordlander, Peter; Corni, Stefano
    Hot electron (HE) photocatalysis is one of the most intriguing fields of nanoscience, with a clear potential for technological impact. Despite much effort, the mechanisms of HE photocatalysis are not fully understood. Here we investigate a mechanism based on transient electron spillover on a molecule and subsequent energy release into vibrational modes. We use state-of-the-art real-time Time Dependent Density Functional Theory (rt-TDDFT), simulating the dynamics of a HE moving within linear chains of Ag or Au atoms, on which CO, N2, or H2O are adsorbed. We estimate the energy a HE can release into adsorbate vibrational modes and show that certain modes are selectively activated. The energy transfer strongly depends on the adsorbate, the metal, and the HE energy. Considering a cumulative effect from multiple HEs, we estimate this mechanism can transfer tenths of an eV to molecular vibrations and could play an important role in HE photocatalysis.
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    Inverted Conformation Stability of a Motor Molecule on a Metal Surface
    (American Chemical Society, 2022) Schied, Monika; Prezzi, Deborah; Liu, Dongdong; Jacobson, Peter; Corni, Stefano; Tour, James M.; Grill, Leonhard; Smalley Institute for Nanoscale Science and Technology; Welch Institute for Advanced Materials
    Molecular motors have been intensely studied in solution, but less commonly on solid surfaces that offer fixed points of reference for their motion and allow high-resolution single-molecule imaging by scanning probe microscopy. Surface adsorption of molecules can also alter the potential energy surface and consequently preferred intramolecular conformations, but it is unknown how this affects motor molecules. Here, we show how the different conformations of motor molecules are modified by surface adsorption using a combination of scanning tunneling microscopy and density functional theory. These results demonstrate how the contact of a motor molecule with a solid can affect the energetics of the molecular conformations.