Design and Characterization of an Electrically Powered Single Molecule on Gold (original) (raw)
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Conformation Manipulation and Motion of a Double Paddle Molecule on an Au(111) Surface
ACS Nano
The molecular conformation of a bisbinaphthyldurene (BBD) molecule is manipulated using a lowtemperature ultrahigh-vacuum scanning tunneling microscope (LT-UHV STM) on an Au(111) surface. BBD has two binaphthyl groups at both ends connected to a central durene leading to anti/syn/flat conformers. In solution, dynamic nuclear magnetic resonance indicated the fast interexchange between the anti and syn conformers as confirmed by density functional theory calculations. After deposition in a submonolayer on an Au(111) surface, only the syn conformers were observed forming small islands of self-assembled syn dimers. The syn dimers can be separated into syn monomers by STM molecular manipulations. A flat conformer can also be prepared by using a peculiar mechanical unfolding of a syn monomer by STM manipulations. The experimental STM dI/dV and theoretical elastic scattering quantum chemistry maps of the low-lying tunneling resonances confirmed the flat conformer BBD molecule STM production. The key BBD electronic states for a step-by-step STM inelastic excitation lateral motion on the Au(111) are presented requiring no mechanical interactions between the STM tip apex and the BBD. On the BBD molecular board, selected STM tip apex positions for this inelastic tunneling excitation enable the flat BBD to move controllably on Au(111) by a step of 0.29 nm per bias voltage ramp.
Langmuir : the ACS journal of surfaces and colloids, 2018
We combine ambient (air) and ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) and spectroscopy (STS) investigations together with density functional theory (DFT) calculations to gain a subnanometer insight into the structure and dynamic of two-dimensional (2D) surface-supported molecular networks. The planar tetraferrocene-porphyrin molecules employed in this study undergo spontaneous self-assembly via the formation of hydrogen bonded networks at the gold substrate-solution interface. To mimic liquid phase ambient deposition conditions, film formation was accomplished in UHV by electro-spraying a solution of the molecule in chloroform onto an Au(111) substrate, thereby providing access to the full spectroscopic capabilities of STM that can be hardly attained under ambient conditions. We show that molecular assembly on Au (111) is identical in films prepared under the two different conditions, and in good agreement with the theoretical predictions. However, we observe the c...
Chinese Physics Letters, 2012
The adsorption and diffusion behaviors of benzene molecules on an Au(111) surface are investigated by lowtemperature scanning tunneling microscopy. A herringbone surface reconstruction of the Au(111) surface is imaged with atomic resolution, and significantly different behaviors are observed for benzene molecules adsorbed on step edges and terraces. The electric field induced modification in the molecular diffusion potential is revealed with a 2D molecular gas model, and a new method is developed to map the diffusion potential over the reconstructed Au(111) surface at the nanometer scale.
1992
Monolayer films of alkanethiolates CH3(CH2)nSH at Au(111) films on mica were examined by scanning tunneling microscopy (STM) (n equals 1,9,17) and AFM (n equals 1 - 17). The resulting atomically resolved images reveal the packing arrangement of the overlayer. Observed images correspond to a hexagonally packed array of adsorbates with respective nearest- and next-nearest-neighbor spacings of 0.50 +/- 0.02 nm and 0.87 +/- 0.04 nm with STM and 0.52 +/- 0.03 nm and 0.90 +/- 0.04 nm with the AFM. This packing agrees with the expected ((root)3 X (root)3)R30 degree(s) adlayer structure of the adsorbate. We believe the STM images reflect the arrangement near the gold-bound sulfur interface, whereas the AFM images reveal the arrangement of the alkyl chains.
Noncontact to contact tunneling microscopy in self-assembled monolayers of alkylthiols on gold
The Journal of Chemical Physics, 2008
The mechanical interaction between a scanning tunneling microscopy ͑STM͒ probe and hexadecane ͑C16͒ alkylthiol molecules in a self-assembled monolayer was investigated by sensing the force during constant current mode STM imaging. The force regime changed from attractive to repulsive over the insulating molecule islands under feedback control of the current. The repulsive force on the molecule was strongly dependent on the setpoint value of the current during STM operation. In our experiments, the threshold for contact was found at a tunneling current of 1 pA when the sample bias is 2 V. At higher current, the apparent height of molecular islands changed logarithmically with current. In addition, the current as a function of applied load revealed a stepwise increase, indicative of discrete molecular tilting events. A tunneling decay constant  of =0.53Ϯ 0.02 Å −1 was obtained based on the measurement of the height of molecules and the tunneling current.
Manipulating Surface Diffusion Ability of Single Molecules by Scanning Tunneling Microscopy
Nano Letters, 2009
The bonding of single diferrocene [Fc(CH 2) 14 Fc, Fc) ferrocenyl] molecules on a metal surface can be enhanced by partial decomposition of Fc groups induced by the tunneling current in scanning tunneling microscopy. Although the isolated intact molecule is mobile on the terrace of Cu(110) at 78 K, the modified molecule is immobilized on the terrace. Calculations based on density functional theory indicate that the hollow site of the Cu(110) surface is the energetically favorable adsorption site for both ferrocene and the Fe-cyclopentadienyl complex, but the latter one possesses a much higher binding energy with the substrate.
The Bulletin of the Korean Chemical Society , 2011
We investigated the effects of tunneling current on scanning tunneling microscopy (STM) images of 1-octanethiol (OT) and 1-decanethiol (DT) self-assembled monolayers (SAMs). At a low tunneling current, the domain boundaries and ordered alkanethiol molecules were clearly resolved. As the tunneling current was increased at a constant bias voltage, however, the STM images showed disordered structures of the OT and DT SAMs. As the tunneling current was reduced back to low values, the ordered structures of the alkanethiol molecules reappeared. The eversibility of the process suggests that the sulfur head groups did not rearrange under any of the tunneling current conditions. On the basis of our observations, which are inconsistent with the standard model for STM imaging of molecules on metal surfaces, we consider the STM imaging mechanism in terms of a two-region tunneling junction model.
Selective internal manipulation of a single molecule by scanning tunneling microscopy
We have studied the adsorption of the polyaromatic molecule 1,4Љ-paratriphenyldimethylacetone, which we have nicknamed Trima. The originality of this linear molecule is that it was designed and synthesized to have two functionalities. First, chemisorb itself to the surface by its two ends rather like a bridge. Second, the central part of the molecule could then be rotated by injecting electrons with the tip of the scanning tunneling microscope ͑STM͒. The length of the molecule corresponds exactly to the spacing between five dimers in a row on the Si͑100͒-2 ϫ 1 surface. We found that the molecule adsorbs as expected on the clean silicon surface by using complementary STM and synchrotron radiation studies. Manipulation of individual molecules with the STM tip showed selective internal modifications that were highly voltage dependent. These manipulations were found to be compatible with an electronic excitation of the -* transition of the molecule.
Bulletin of the Korean Chemical Society, 2011
We investigated the effects of tunneling current on scanning tunneling microscopy (STM) images of 1-octanethiol (OT) and 1-decanethiol (DT) self-assembled monolayers (SAMs). At a low tunneling current, the domain boundaries and ordered alkanethiol molecules were clearly resolved. As the tunneling current was increased at a constant bias voltage, however, the STM images showed disordered structures of the OT and DT SAMs. As the tunneling current was reduced back to low values, the ordered structures of the alkanethiol molecules reappeared. The reversibility of the process suggests that the sulfur head groups did not rearrange under any of the tunneling current conditions. On the basis of our observations, which are inconsistent with the standard model for STM imaging of molecules on metal surfaces, we consider the STM imaging mechanism in terms of a two-region tunneling junction model.
Langmuir
In situ scanning tunneling microscopy (STM) was employed to study the structure of adlayers of crystal violet (CV) and water-soluble porphyrin formed on a sulfur-modified Au(111) electrode in perchloric acid solution. It was confirmed that a well-defined sulfur adlayer with ( 3 × 3)R30°structure can be prepared on Au(111) under potential control. Highly ordered adlayers of the molecules were found to form on the sulfur-modified Au(111) surface. In situ STM revealed the characteristic shape, packing arrangement, and even internal structure of each molecule. It is demonstrated that the sulfur-modified Au(111) electrode can be used as a substrate suitable for the investigation of the adsorption of organic molecules in solution.