Chiral Molecular Cavities of Calix[4]Crown on Au(111)

2008 ◽  
Vol 8 (11) ◽  
pp. 5702-5707 ◽  
Author(s):  
Ge-Bo Pan ◽  
Jun Luo ◽  
Qi-Yu Zheng ◽  
Li-Jun Wan
Keyword(s):  
Self Assembly ◽  
Chiral Recognition ◽  
Scanning Tunneling ◽  
Racemic Mixture ◽  
Tunneling Microscopy ◽  
Geometrical Structures ◽  
Simple Method ◽  
Ordered Structures ◽  
Ordered Arrays ◽  
Stm Images

Well-ordered arrays of chiral molecular cavities have been constructed by self-assembly of inherently chiral calix[4]crown on Au(111) in 0.1 M HClO4 solution and investigated by scanning tunneling microscopy (STM). The chiral features are clearly observed in high resolution STM images. It is found that the adsorption of the two enantiomers results in the same ordered structures with upright orientation on Au(111). Moreover, only phase separation has been observed for the racemic mixture of the two enantiomers in the experiment. This is mainly due to the weak molecule-substrate interaction as well as asymmetric geometrical structures of the two enantiomers. The present study provides a simple method for construction of ordered arrays of chiral molecular cavities, which are of potential in chemical sensors, chiral recognition, and nonlinear optics.

Self-Assembly of a Novel Cationic Porphyrin-Anthraquione Hybrid Investigated by Scanning Tunneling Microscopy

2010 ◽  
Vol 148-149 ◽  
pp. 1273-1276 ◽  
Author(s):  
Ai Mei Gao ◽  
Wen Li Deng ◽  
Hong Yu Chen
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Self Assembly ◽  
Large Scale ◽  
Room Temperature ◽  
Pyrolytic Graphite ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Hybrid Compound ◽  
Cationic Porphyrin ◽  
Stm Images

The self-assembly behaviour of a novel cationic porphyrin-anthraquione (Por-AQ) hybrid ([AQATMPyP]I3) on highly oriented pyrolytic graphite (HOPG) was studied at room temperature in air by scanning tunneling microscopy(STM). According to theoretical calculation, it is testified that [AQATMPyP]I3 molecule mainly exists in the closed structure. The STM results reveal the presence of large-scale domains of ordered adlayer of this hybrid compound on HOPG. The STM images show a structure constituted by parallel rows. The width of each row is approximately 2.5nm.

Scanning Tunneling Microscopy Imaging and Spectroscopy of a Single Viologen Molecule

2008 ◽  
Vol 8 (9) ◽  
pp. 4621-4625
Author(s):  
Nam-Suk Lee ◽  
Chang-Heon Yang ◽  
Won-Suk Choi ◽  
Young-Soo Kwon
Keyword(s):  
Self Assembly ◽  
Current Mode ◽  
Scanning Tunneling Spectroscopy ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Microscopy Imaging ◽  
Current Voltage ◽  
Imaging And Spectroscopy ◽  
Stm Images

A low-temperature ultrahigh-vacuum scanning tunneling microscope (UHV-STM) was used to image viologen (N-methyl-N′-di (8-mercaptooctyl)-4,4′-bipyridinium; HSC8VC8SH) molecules and to perform local spectroscopic measurements on these molecules. Self-assembly of viologen molecules was conducted on Au (111), which had been thermally deposited onto freshly cleaved, heated mica. Here, we demonstrate a novel SAM matrix appropriate for the isolation of viologen molecules composed of octanethiol (C8) in which HSC8VC8SH was inserted at defects in the molecular lattice. The isolated single molecules of viologen inserted in the SAM matrix were observed as protrusions in STM topography using a constant current mode. STM images at 298 K showed protrusions with a topographic height of about 2.71 nm (HSC8VC8SH) with viologen molecules that self-assembled on the substrate. The current–voltage (I–V) characteristics were measured while the electrical properties of the formed monolayer were scanned using scanning tunneling spectroscopy (STS). We found the high peak current-like rectification at +1.14 V (HSC8VC8SH). The rectification ratios, RR = J (at +2.5 V)/J (at −2.5 V), are in the range of 4.47.

scholarly journals Chiral Recognition of Hexahelicene on a Surface via the Forming of Asymmetric Heterochiral Trimers

2019 ◽  
Vol 20 (8) ◽  
pp. 2018
Author(s):  
Hong Zhang ◽  
Hong Liu ◽  
Chengshuo Shen ◽  
Fuwei Gan ◽  
Xuelei Su ◽  
...  
Keyword(s):  
Self Assembly ◽  
Chiral Recognition ◽  
Theoretical Calculations ◽  
Strong Stability ◽  
Model Systems ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Helical Molecules ◽  
Intermolecular Recognition

Chiral recognition among helical molecules is of essential importance in many chemical and biochemical processes. The complexity necessitates investigating manageable model systems for unveiling the fundamental principles of chiral recognition at the molecular level. Here, we reported chiral recognition in the self-assembly of enantiopure and racemic hexahelicene on a Au(111) surface. Combing scanning tunneling microscopy (STM) and atomic force microscopy (AFM) measurements, the asymmetric heterochiral trimers were observed as a new type of building block in racemic helicene self-assembly on Au(111). The intermolecular recognition of the heterochiral trimer was investigated upon manual separation so that the absolute configuration of each helicene molecule was unambiguously determined one by one, thus confirming that the trimer was “2+1” in handedness. These heterochiral trimers showed strong stability upon different coverages, which was also supported by theoretical calculations. Our results provide valuable insights for understanding the intermolecular recognition of helical molecules.

Scanning Tunneling Microscopy of Amorphous Carbon Films

1990 ◽  
Vol 48 (1) ◽  
pp. 318-319
Author(s):  
Mircea Fotino ◽  
D.C. Parks
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Amorphous Carbon ◽  
Carbon Films ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Amorphous Carbon Films ◽  
Image Optimization ◽  
Step Procedure ◽  
Stm Images

In the last few years scanning tunneling microscopy (STM) has made it possible and easily accessible to visualize surfaces of conducting specimens at the atomic scale. Such performance allows the detailed characterization of surface morphology in an increasing spectrum of applications in a wide variety of fields. Because the basic imaging process in STM differs fundamentally from its equivalent in other well-established microscopies, good understanding of the imaging mechanism in STM enables one to grasp the correct information content in STM images. It thus appears appropriate to explore by STM the structure of amorphous carbon films because they are used in many applications, in particular in the investigation of delicate biological specimens that may be altered through the preparation procedures.All STM images in the present study were obtained with the commercial instrument Nanoscope II (Digital Instruments, Inc., Santa Barbara, California). Since the importance of the scanning tip for image optimization and artifact reduction cannot be sufficiently emphasized, as stressed by early analyses of STM image formation, great attention has been directed toward adopting the most satisfactory tip geometry. The tips used here consisted either of mechanically sheared Pt/Ir wire (90:10, 0.010" diameter) or of etched W wire (0.030" diameter). The latter were eventually preferred after a two-step procedure for etching in NaOH was found to produce routinely tips with one or more short whiskers that are essentially rigid, uniform and sharp (Fig. 1) . Under these circumstances, atomic-resolution images of cleaved highly-ordered pyro-lytic graphite (HOPG) were reproducibly and readily attained as a standard criterion for easily recognizable and satisfactory performance (Fig. 2).

scholarly journals Strain-Relief Patterns and Kagome Lattice in Self-Assembled C60 Thin Films Grown on Cd(0001)

2021 ◽  
Vol 22 (13) ◽  
pp. 6880
Author(s):  
Zilong Wang ◽  
Minlong Tao ◽  
Daxiao Yang ◽  
Zuo Li ◽  
Mingxia Shi ◽  
...  
Keyword(s):  
Thin Films ◽  
Self Assembly ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Kagome Lattice ◽  
Tunneling Microscopy ◽  
Kagomé Lattice ◽  
Temperature Scanning ◽  
C60 Films

We report an ultra-high vacuum low-temperature scanning tunneling microscopy (STM) study of the C60 monolayer grown on Cd(0001). Individual C60 molecules adsorbed on Cd(0001) may exhibit a bright or dim contrast in STM images. When deposited at low temperatures close to 100 K, C60 thin films present a curved structure to release strain due to dominant molecule–substrate interactions. Moreover, edge dislocation appears when two different wavy structures encounter each other, which has seldomly been observed in molecular self-assembly. When growth temperature rose, we found two forms of symmetric kagome lattice superstructures, 2 × 2 and 4 × 4, at room temperature (RT) and 310 K, respectively. The results provide new insight into the growth behavior of C60 films.

scholarly journals Au(100) as a Template for Pentacene Monolayer

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2393
Author(s):  
Artur Trembułowicz ◽  
Agata Sabik ◽  
Miłosz Grodzicki
Keyword(s):  
Self Assembly ◽  
Molecular Layer ◽  
High Vacuum ◽  
Gold Surface ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Height Difference ◽  
Characteristic Features ◽  
Reconstructed Surface

The surface of quasi-hexagonal reconstructed Au(100) is used as the template for monolayer pentacene (PEN) self-assembly. The system is characterized by means of scanning tunneling microscopy at room temperature and under an ultra-high vacuum. A new modulated pattern of molecules with long molecular axes (MA) arranged along hex stripes is found. The characteristic features of the hex reconstruction are preserved herein. The assembly with MA across the hex rows leads to an unmodulated structure, where the molecular layer does not recreate the buckled hex phase. The presence of the molecules partly lifts the reconstruction—i.e., the gold hex phase is transformed into a (1×1) phase. The arrangement of PEN on the gold (1×1) structure is the same as that of the surrounding molecular domain on the reconstructed surface. The apparent height difference between phases allows for the distinction of the state of the underlying gold surface.

scholarly journals Self-assembly of N-heterocyclic carbenes on Au(111)

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alex Inayeh ◽  
Ryan R. K. Groome ◽  
Ishwar Singh ◽  
Alex J. Veinot ◽  
Felipe Crasto de Lima ◽  
...  
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Surface Coverage ◽  
High Mobility ◽  
Heterocyclic Carbenes ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Surface Geometry ◽  
Functional Theory ◽  
Interesting Alternative

AbstractAlthough the self-assembly of organic ligands on gold has been dominated by sulfur-based ligands for decades, a new ligand class, N-heterocyclic carbenes (NHCs), has appeared as an interesting alternative. However, fundamental questions surrounding self-assembly of this new ligand remain unanswered. Herein, we describe the effect of NHC structure, surface coverage, and substrate temperature on mobility, thermal stability, NHC surface geometry, and self-assembly. Analysis of NHC adsorption and self-assembly by scanning tunneling microscopy and density functional theory have revealed the importance of NHC-surface interactions and attractive NHC-NHC interactions on NHC monolayer structures. A remarkable way these interactions manifest is the need for a threshold NHC surface coverage to produce upright, adatom-mediated adsorption motifs with low surface diffusion. NHC wingtip structure is also critical, with primary substituents leading to the formation of flat-lying NHC2Au complexes, which have high mobility when isolated, but self-assemble into stable ordered lattices at higher surface concentrations. These and other studies of NHC surface chemistry will be crucial for the success of these next-generation monolayers.

Surface Structures of Phosphorus and Indium on Si(111)

1998 ◽  
Vol 05 (01) ◽  
pp. 69-76
Author(s):  
F. P. Netzer ◽  
L. Vitali ◽  
J. Kraft ◽  
M. G. Ramesy
Keyword(s):  
Elevated Temperature ◽  
Room Temperature ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Low Energy Electron Diffraction ◽  
Diffusion Limited ◽  
Lower Terrace ◽  
Surface Reconstructions ◽  
Low Energy Electron ◽  
Stm Images

The interaction of vapor phase P2 with the [Formula: see text] monolayer surface at room temperature and elevated temperature has been monitored by scanning tunneling microscopy (STM) and spectroscopy (STS) in conjunction with Auger electron spectroscopy and low-energy electron diffraction (LEED). The surface rection can be readily followed by STM because of the very different contrast of the reacted areas in the STM images. The reaction develops around overlayer defects at room temperature and appears to be diffusion-limited, whereas at 300°C the reaction is initiated at the step edges, from which the reaction front progresses onto the lower terrace areas. At elevated temperature several ordered surface reconstructions, showing different STS fingerprints, are detected on the P–In/Si(111) surfaces, which are associated tentatively with P- and Si-terminated structures and an ordered InP phase.

scholarly journals Mono- and multilayers of molecular spoked carbazole wheels on graphite

2014 ◽  
Vol 10 ◽  
pp. 2783-2788 ◽  
Author(s):  
Stefan-S Jester ◽  
A Vikas Aggarwal ◽  
Daniel Kalle ◽  
Sigurd Höger
Keyword(s):  
Octanoic Acid ◽  
Pyrolytic Graphite ◽  
Self Assembled Monolayers ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Chemical Structures ◽  
Rigid Objects ◽  
Assembled Monolayers ◽  
Stm Images ◽  
Insight Into

Self-assembled monolayers of a molecular spoked wheel (a shape-persistent macrocycle with an intraannular spoke/hub system) and its synthetic precursor are investigated by scanning tunneling microscopy (STM) at the liquid/solid interface of 1-octanoic acid and highly oriented pyrolytic graphite. The submolecularly resolved STM images reveal that the molecules indeed behave as more or less rigid objects of certain sizes and shapes – depending on their chemical structures. In addition, the images provide insight into the multilayer growth of the molecular spoked wheels (MSWs), where the first adlayer acts as a template for the commensurate adsorption of molecules in the second layer.

Sign in / Sign up

Export Citation Format

Share Document