Molecular Dynamics in Two-Dimensional Supramolecular Systems Observed by STM (original) (raw)
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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...
Complex Interplay and Hierarchy of Interactions in Two-Dimensional Supramolecular Assemblies
ACS Nano, 2011
In order to address the interplay of hydrogen bonding, dipolar interactions, and metal coordination, we have investigated the two-dimensional mono-and bicomponent self-assembly of three closely related diaminotriazine-based molecular building blocks and a complementary perylenetetracarboxylic diimide by means of scanning tunneling microscopy. The simplest molecular species, bis-diaminotriazine-benzene, only interacts via hydrogen bonds and forms a unique supramolecular pattern on the Au(111) surface. For the two related molecular species, which exhibit in addition to hydrogen bonding also dipolar interactions and metal coordination, the number of distinct supramolecular structures increases dramatically with the number of possible interaction channels. Deposition together with the complementary perylene species, however, always results in a single well-defined supramolecular arrangement of molecules. A detailed analysis of the observed mono-and bicomponent assemblies allows shedding light on the hierarchy of the competing interactions, with important implications for the fabrication of surface-supported supramolecular networks by design.
Supramolecular Chemistry at the Liquid/Solid Interface
MRS Proceedings, 2005
The liquid/solid interface provides an ideal environment to investigate self-assembly phenomena and scanning tunneling microscopy (STM) is the preferred methodology to probe the structure and the properties of physisorbed monolayers on the nanoscale. Physisorbed monolayers are of relevance in areas such as lubrication, patterning of surfaces on the nanoscale, and thin film based organic electronic devices, to name a few. It's important to gain insight in the factors which control the ordering of molecules at the liquid/solid interface in view of the targeted properties. STM provides detailed insight into the importance of molecule-substrate (epitaxy) and molecule-molecule interactions to direct the ordering of both achiral and chiral molecules on the atomically flat surface. The electronic properties of the self-assembled physisorbed molecules can be probed by taking advantage of the operation principle of STM, revealing spatially resolved intramolecular differences within these...
Bottom-Up Self-Assembled Supramolecular Structures Built by STM at Solid/Liquid Interface
The development of organic devices has been focused in their miniaturization in order to obtain denser and faster electronic circuits. The challenge is to build the devices adding atom by atom or molecule by molecule until the desired structure is achieved. To do this job, techniques able to see and manipulate matter at this scale are needed. Scanning tunneling microscopy has been the selected technique by scientists to develop smart and functional unimolecular devices. This review article compiles the latest developments in this field giving examples of supramolecular systems monitored and fabricated at molecular scale by bottom-up approaches using STM at solid/liquid interface.
Scanning tunneling microscope-induced molecular motion and its effect on the image formation
Surface Science, 1998
The effect of tip-induced molecular motion on the appearance of scanning tunneling microscope (STM ) images of anthracene on Ag(110) was investigated for various tunneling parameters and at various temperatures. At 50 K, isolated molecules can be imaged at a high tunneling resistance. For an increased tip-molecule interaction at a decreased resistance, apparent one-dimensional and two-dimensional molecular superstructures arise in the STM images that are due to an interplay between tip-induced motion, transient binding at specific substrate sites and repeated imaging of a molecule. At an even higher tip-molecule interaction strength, molecules can be dragged over the surface such that an atomically resolved substrate lattice is discernible. The slid molecule acts as an amplifier of the charge corrugation of the metallic surface.
Exploring the transferability of large supramolecular assemblies to the vacuum-solid interface
Nano Research, 2009
We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a goldfunctionalized rosette assembly and its building blocks on a Au(111) surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces. The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111) surface under ultra-high vacuum conditions; the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly, suggesting that the assembly itself can be transferred intact to the surface by in situ thermal sublimation. This unanticipated result will open up new perspectives for growth of complex 3-D supramolecular nanostructures at the vacuum-solid interface.
Moving Nanostructures: Pulse Induced Positioning of Supramolecular Assemblies
2012
For the development of nanoscale devices, the manipulation of single atoms and molecules by scanning tunneling microscopy is a well established experimental technique. However, for the construction of larger and higher order structures, it is important to move not only one adsorbate, but several at the same time. Additionally, a major issue in standard manipulation experiments is the strong mechanical interaction of the tip apex and the adsorbate, which can damage the system under investigation.
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.
Acs Nano, 2010
The two-dimensional (2D) crystal engineering of molecular architectures on surfaces requires controlling various parameters related respectively to the substrate, the chemical structure of the molecules, and the environmental conditions. We investigate here the influence of temperature on the selfassembly of hexakis(n-dodecyl)-peri-hexabenzocoronene (HBC-C 12 ) adsorbed on gold using scanning tunneling microscopy (STM) at the liquid/solid interface. We show that the packing density of 2D self-assembled HBC-C 12 can be precisely tuned by adjusting the substrate temperature. Increasing the temperature progressively over the 20؊50°C range induces three irreversible phase transitions and a 3-fold increase of the packing density from 0.111 to 0.356 molecule/nm 2 . High-resolution STM images reveal that this 2D packing density increase arises from the stepwise desorption of the n-dodecyl chains from the gold surface. Such temperature-controlled irreversible phase transitions are thus a versatile tool that can then be used to adjust the packing density of highly ordered functional materials in view of applications in organic electronic devices.