Formation of (FeCl3)@phenylazomethine dendrimer (DPA): Fine control of the release and encapsulation of Fe ions in dendrimers

2009 ◽  
Vol 81 (12) ◽  
pp. 2253-2263
Author(s):  
Kimihisa Yamamoto ◽  
Reina Nakajima ◽  
Yousuke Ochi ◽  
Masanori Tsuruta ◽  
Masayoshi Higuchi ◽  
...  
Keyword(s):  
Metal Ion ◽  
Scanning Tunneling ◽  
Uniform Structure ◽  
Research Groups ◽  
Tunneling Microscopy ◽  
Precise Control ◽  
Oriented Film ◽  
Successful Attempt ◽  
Fine Control ◽  
Fe Ions

Phenylazomethine dendrimers (DPAs) act as a strong coordination site for metal ion assembly. DPA G4 is regarded as a molecular capsule having 30 metal-assembling sites with a 2.7 nm diameter. We have reported the radial stepwise complexation with Sn2+ ions in the dendrimers, which means the location and number of metal ions can be controlled. Therefore, DPA G4 should realize a ferritin-like redox nanocapsule with precise control of the number of Fe ions. On the other hand, the Fe ion is a typical paramagnetic molecule. For creating an advanced memory with a high density, ferritin is one of the candidates for use as a magnetic quantum dot. Many attempts to use biomaterials, for example, ferritins and chapero-nins, as metal storage capsules have been demonstrated. Some research groups fabricate a device by assembling ferritins on a plate using their rigid and uniform structure. The attempts to use dendrimers have also been demonstrated. We now describe the successful attempt to control the "encapsulation and release" of iron ions in a dendrimer in order to mimic a ferritin through the redox reaction. Furthermore, the assembling structures of (FeCl3)n@DPA on a plate were first observed by scanning tunneling microscopy (STM) as a dendrimer complex, which shows that a highly oriented film is formed on a plate only by solvent casting.

MODIFICATION OF NORMAL-STATE AND SUPERCONDUCTING PROPERTIES OF HIGH-Tc OXIDES VIA TREATMENT BY METAL-PHTHALOCYANINES

1994 ◽  
Vol 08 (05) ◽  
pp. 615-639 ◽  
Author(s):  
LEONID GRIGORYAN ◽  
KYUYA YAKUSHI ◽  
A. V. NARLIKAR ◽  
P. K. DUTTA ◽  
S. B. SAMANTHA
Keyword(s):  
Metal Ion ◽  
Scanning Tunneling ◽  
Zero Field ◽  
Central Metal ◽  
Tunneling Microscopy ◽  
Absorption Data ◽  
Metal Phthalocyanines ◽  
Oxide Powders ◽  
Lower Magnitude ◽  
New Compounds

Exposure of Bi- or Tl-based high-T c oxide powders to vapors of metal-phthalocyanines MPc (M is Zn or Ni) resulted in the formation of a family of new compounds with modified crystal lattice parameters, electronic structure, phonon spectrum and magnetic properties as compared to the starting materials. Based on the combined X ray diffraction, scanning tunneling microscopy, optical, FT–IR and microwave absorption data, a model of crystal structure is proposed where the key feature is intercalation of MPc molecules between the Bi-O (Tl-O) bilayers. Values of dc magnetization at 300 K varied over two orders of magnitude as a function of chemical composition and nature of the central metal ion in MPc. Measurements of temperature dependence of magnetization of the intercalated samples revealed a divergence at low temperatures between the zero-field and the field-cooled cycles, though of lower magnitude as compared to the starting high-T c oxides. The results of this study suggest that treatment by MPc offers a possibility of controllable variation of key properties of high-T c oxides.

The (001) Surface of Fe3O4 Grown Epitaxially on MgO and Characterized by Scanning Tunneling Microscopy.

1997 ◽  
Vol 474 ◽  
Author(s):  
J. M. Gaines ◽  
J. T. Kohlhepp ◽  
J.T.W.M. van Eemeren ◽  
R.J.G. Elfrink ◽  
F. Roozeboom ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Charge Density ◽  
Molecular Beam ◽  
Scanning Tunneling ◽  
High Electrical Conductivity ◽  
Tunneling Microscopy ◽  
Electron Charge Density ◽  
Octahedral Sites ◽  
Tetrahedral Sites ◽  
Fe Ions

AbstractSpinel Fe3O4 contains two sites for iron: tetrahedrally coordinated sites containing Fe3+ ions and octahedrally coordinated sites containing a mixture of Fe2+ and Fe3+ ions. Scanning tunneling microscopy performed on the (001) surface of Fe3O4, grown epitaxially on MgO, shows localized charge density at the tetrahedral sites. The images show that the p(1×1) surface reconstruction (also observed during molecular beam epitaxy of Fe3O4) is produced by a displacement of the two tetrahedrally coordinated Fe ions on the unit cell surface from their bulk positions toward each other. The octahedral Fe ions are imaged as extended rows of charge density, with no resolution of atom-size features along the rows. This slight corrugation of electron charge density along the octahedral sites is consistent with the original conjectures explaining the high electrical conductivity in bulk Fe3O4: electrons move by hopping between the Fe3+ and Fe2+ atoms along the octahedral rows of Fe ions.

Scanning Tunneling Microscopy and Spectroscopy of Y-Ba-Cu-O Thin Films Produced by Ion Beam Sputter-Deposition

1992 ◽  
Vol 275 ◽  
Author(s):  
R. C. Chapman ◽  
O. Aucffillo ◽  
D. J. LichtenWalner ◽  
R. P. Adu ◽  
C. N. SobleII ◽  
...  
Keyword(s):  
Thin Films ◽  
Scanning Tunneling Microscopy ◽  
Ion Beam ◽  
Sputter Deposition ◽  
Growth Mode ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Oriented Film ◽  
Oriented Films ◽  
Ion Beam Sputter Deposition

ABSTRACTIon beam sputter-deposition has been used to produce high temperature superconducting (HTSC) thin films with controlled orientation. Room temperature scanning tunneling microscopy (STM) studies of ion beam sputter-deposited Y-Ba-Cu-O thin films indicate that the growth mode depends on whether the films are a- or c-axis oriented. The c-axis oriented films appear to grow by a screw dislocation mechanism, producing layered spirals similar to those observed in films grown by plasma sputtering and laser ablation-deposition. STM images of the a-axis oriented films show a growth mode which appears to produce layered structures perpendicular to the substrate with no spirals. Scanning tunneling spectroscopy (STS) studies of the a- and c-axis oriented films tend to reflect the anisotropy of the Y-Ba-Cu-O structure. Both the c-axis and the a-axis oriented films have semiconducting characteristics, possibly due to a native oxide, with a band gap estimated to be 1.4 eV. The c-axis oriented film, however, exhibits more fine structure in its density of states. This apparent anisotropie band structure reflects the anisotropie Y-Ba-Cu-O microstructure and superconducting characteristics. Investigations with x-ray photcelectron spectroscopy (XPS) establish a substantial chemical difference between the two surfaces inferring more substantial native oxides and air-induced by-products on the a-axis oriented film.

scholarly journals Flat epitaxial quasi-1D phosphorene chains

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wei Zhang ◽  
Hanna Enriquez ◽  
Yongfeng Tong ◽  
Andrew J. Mayne ◽  
Azzedine Bendounan ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Photoemission Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Functional Theory ◽  
Precise Control ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Room Temperature Magnetism ◽  
Topological Phase Transitions

AbstractThe emergence of peculiar phenomena in 1D phosphorene chains (P chains) has been proposed in theoretical studies, notably the Stark and Seebeck effects, room temperature magnetism, and topological phase transitions. Attempts so far to fabricate P chains, using the top-down approach starting from a few layers of bulk black phosphorus, have failed to produce reliably precise control of P chains. We show that molecular beam epitaxy gives a controllable bottom-up approach to grow atomically thin, crystalline 1D flat P chains on a Ag(111) substrate. Scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and density functional theory calculations reveal that the armchair-shaped chains are semiconducting with an intrinsic 1.80 ± 0.20 eV band gap. This could make these P chains an ideal material for opto-electronic devices.

scholarly journals Topological phase transition in chiral graphene nanoribbons: from edge bands to end states

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jingcheng Li ◽  
Sofia Sanz ◽  
Nestor Merino-Díez ◽  
Manuel Vilas-Varela ◽  
Aran Garcia-Lekue ◽  
...  
Keyword(s):  
Phase Transition ◽  
Graphene Nanoribbons ◽  
Scanning Tunneling ◽  
Topological Phase ◽  
Tunneling Microscopy ◽  
Molecular Precursors ◽  
Precise Control ◽  
Band Engineering ◽  
Topological Phase Transition ◽  
Topological States

AbstractPrecise control over the size and shape of graphene nanostructures allows engineering spin-polarized edge and topological states, representing a novel source of non-conventional π-magnetism with promising applications in quantum spintronics. A prerequisite for their emergence is the existence of robust gapped phases, which are difficult to find in extended graphene systems. Here we show that semi-metallic chiral GNRs (chGNRs) narrowed down to nanometer widths undergo a topological phase transition. We fabricated atomically precise chGNRs of different chirality and size by on surface synthesis using predesigned molecular precursors. Combining scanning tunneling microscopy (STM) measurements and theory simulations, we follow the evolution of topological properties and bulk band gap depending on the width, length, and chirality of chGNRs. Our findings represent a new platform for producing topologically protected spin states and demonstrate the potential of connecting chiral edge and defect structure with band engineering.

Simulation and Analysis of Methods for Scanning Tunneling Microscopy Feedback Control

2019 ◽  
Vol 25 (2) ◽  
pp. 554-560
Author(s):  
Jeremy Wiedemeier ◽  
Greg Spencer ◽  
Mark J. Hagmann ◽  
Marwan S. Mousa
Keyword(s):  
Scanning Tunneling Microscope ◽  
Control Algorithm ◽  
Tunneling Current ◽  
Control Algorithms ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Set Point ◽  
Precise Control ◽  
And Performance ◽  
Sample Distance

AbstractA scanning tunneling microscope (STM) requires precise control of the tip–sample distance to maintain a constant set-point tunneling current. Typically, the tip–sample distance is controlled through the use of a control algorithm. The control algorithm takes in the measured tunneling current and returns a correction to the tip–sample distance in order to achieve and maintain the set-point value for tunneling current. We have developed an STM simulator to test the accuracy and performance of four control algorithms. The operation and effectiveness of these control algorithms are evaluated.

Fabrication of a Regular Array of Atomic Silicon Wires on Silicon

2004 ◽  
Vol 832 ◽  
Author(s):  
Takeharu Sekiguchi ◽  
Shunji Yoshida ◽  
Kohei M. Itoh
Keyword(s):  
Self Assembly ◽  
Quantum Computer ◽  
Scanning Tunneling ◽  
Uniform Structure ◽  
Specific Substrate ◽  
Nuclear Spins ◽  
Tunneling Microscopy ◽  
Experimental Realization ◽  
Atomic Wires ◽  
Si Isotopes

ABSTRACTWe report on the experimental realization of atomically straight, single wires of Si atoms on a Si surface. The Si wires were formed by solid-source molecular beam epitaxy (MBE) on a specific substrate prepared by a thermal treatment of a vicinal Si(111) wafer. The structures of the substrate and the atomic wire were investigated by scanning tunneling microscopy (STM). The substrate consists of an array of atomically straight step edges with a uniform structure serendipitously suitable for self-assembly of the atomic wires. The isotopic version of this structure —single lines of29Si on28Si— is expected to be the most basic building block for the all-silicon quantum computer [1], which utilizes the nuclear spins of individual29Si isotopes as quantum bits (qubits).

STM studies of crystal growth

1991 ◽  
Vol 49 ◽  
pp. 374-375
Author(s):  
M. G. Lagally
Keyword(s):  
Crystal Growth ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Sputter Deposition ◽  
Field Of View ◽  
Scanning Tunneling ◽  
Wide Field ◽  
Tunneling Microscopy ◽  
Wide Field Of View ◽  
The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

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