Search

Electroactive tetrathaifulvalene (TTF)-containing alkanethiol self-assembled monolayers (SAMs) are designed and synthesized to elucidate the relationship between electrochemical responses and film structures. Results reveal that TTF-based SAMs exhibited collective electrochemical responses induced by dynamic structural changes, depending on the degree of freedom for the component molecules in the SAMs.

A description is provided on the pressure dependence of the magnetic properties of weak ferromagnetics (BDH-TTP)(M(isoq)2(NCS)4)(BDH-TTP) = 2,5-bis(1',3'-dithiolan-2'-ylidene)-1,3,4,6-tetrathiapentalene, M = Cr, Fe, isoq=isquinoline). The pressure dependence of the remanent magnetization suggests that for the Cr salt, single-ion anisotropy mainly governs the spin canting, whereas the D-M interaction does so for the Fe salt.

Electroactive tetrathiafulvalene thiol islands embedded in an n-alkanethiol self assembled monolayer (SAM) matrix are studied under potential control using in situ scanning tunneling microscopy. Results indicate that not only the oxidation state but also the orientation of the electroactive moiety responds to the electrochemical potential and that orientational change is also a key factor in designing molecular devices under potential control.

An analogous phenomenon for the azide complexes for nickel (II) is described. The thermodynamic and kinetic parameters of the studied redox system are determined by a comparison of the experimental and theoretical dependencies.

The relationship between the polymer conformation and fluorescence is discussed and a new method for aligning poly[2-methoxy-5-(2'-ethylexyloxy)-1,4-phenylevinylene] (MEH-PPV) is presented. A general procedure and solvent-induced homogeneous dispersion (SIHD) is presented to align conjugated polymers.

An all electrochemical deposition process is developed to prepare the polypyrrole nanocomposite films containing multiple layers of CdSe and CdTe. A top covering layer of polypyrrole not only further smoothed the surface but also further boosted the photoluminescence intensity of the nanocomposite film because of the enhanced radiative electron-hole recombination.

Cerium endohedral metallofullerene (Ce@C82) is a pi-f composite nanomagnet, where anisotropic f-electron spin is expected to couple with the rotational motion of the fullerene cage that has pi-electron spin. The magnetic properties of Ce@C82 using the field-induced change in the magnetic susceptibility of organic solutions of Ce@C82 and the temperature dependence of the magnetic susceptibility and magnetization of Ce@C82 solid films are investigated.

Research has been conducted on the isostructural charge transfer salts. The preparation, magnetic properties and X-ray crystal structures of these compounds have been examined and the results indicate that compounds' ferrimagnetic interactions occur between anion spins and nonequivalent donor.

Research has been conducted on the charge-transfer salts. The preparation, optical and magnetic properties and the crystal structure of these salts have been investigated and the vibrational and electronic features of these powdered crystals are described.

A novel technique devised to fabricate self-assembled monolayers (SAMs) of 2D charge-transfer complexes by coadsorption of thiol-funtionalized tethrathiafulvalene derivatives (TTF-CH2SH) with 7,7,8,8-tetracyanoquinodimethane (TCNQ) on a gold substrate is discussed. Using the conventional layer-by-layer adsorption method the TTF-CH2SH/TCNQ SAMs are prepared to compare the film properties with those of the coadsorbed SAMs.

The scanning and tunneling microscope images clarify the substitution of boron atoms in the basal plane of highly oriented pyrolytic graphite (HOPG). The STM measurements indicate that the substitution of boron atoms enlarges some defects or introduces disorder into the graphite layers.

The synthesis, crystal and network structures and the magnetic properties of the hybrid-layered compound [{K(18-cr)(2-PrOH)2}-{Mn(acacen)}2{Fe(CN)}] are described. The compound was prepared by reacting tK3[Fe(CN)6] and 18-crown-6-ether in methanol. A two-dimensional layer consisting of the cyclic octamer [-Mn-NC-Fe-CN-]4 having the Fe ions at the corners and the Mn ions on the edges of a deformed square. It was also observed that the cationic layer is composed of a two-dimensional arrangement of [K(18-cr)(2-PrOH)2]+.

The electronic and magnetic structures of diamond nanoparticles with a hydrogenated surface are investigated as a function of annealing temperature under vacuum annealing up to 800–1000 °C. Near edge X-ray absorption fine structure (NEXAFS) spectra together with elemental analysis show successive creation of defect-induced nonbonding surface states at the expense of surface-hydrogen atoms as the annealing temperature is increased above 800 °C. Magnetization and ESR spectra confirm the increase in the concentration of localized spins assigned to the nonbonding surface states upon the increase of the annealing temperature. Around 800 °C, surface defects collectively created upon the annealing result in the formation of graphene nano-islands which possess magnetic nonbonding edge states of π-electron origin. Interestingly, extremely slow spin relaxation is observed in the magnetization of the edge state spins at low temperatures. The relaxation time is well explained in terms of a lognormal distribution of magnetic anisotropy energies instead of the classical Néel relaxation mechanism with a unique magnetic anisotropy energy, in addition to the contribution of the quantum mechanical tunnelling mechanism. The spin–orbit interaction enhanced by the electrostatic potential gradient created at the interface between the core diamond particle and surface graphene nano-islands is responsible for the slow spin relaxation. [ABSTRACT FROM AUTHOR]

The electronic structure of massless Dirac fermion in the graphene hexagonal bipartite is seriously modified by the presence of edges depending on the edge chirality. In the zigzag edge, strongly spin polarized nonbonding edge state is created as a consequence of broken symmetry of pseudo-spin. In the scattering at armchair edges, the K-K’ intervalley transition gives rise to electron wave interference. The presence of edge state in zigzag edges is observed in ultra-high vacuum STM/STS observations. The electron wave interference phenomenon in the armchair edge is observed in the Raman G-band and the honeycomb superlattice pattern with its fine structure in STM images.

Electron donor–acceptor–donor (D–A–D) π-conjugated molecules based on dipyrido[3,2-a:2′,3′-c]phenazine (dppz) were developed as photosensitizers for singlet oxygen generation. These dppz derivatives showed electronic absorption assigned to an intramolecular charge transfer transition in the red region at a wavelength of around 600 nm. Evaluation of singlet oxygen generation quantum yield (ΦΔ) using the trapping agent 1,3-diphenylisobenzofuran showed relatively efficient singlet oxygen generation (ΦΔ; 0.173–0.255) for the dppz derivatives with selenophene-containing π-conjugated side-arms. On the other hand, 2,7-dibromo substitution and Pt(II)Cl2 complexation of the dppz derivative with thiophene-containing side-arms did not facilitate photosensitized singlet oxygen generation. Density functional theory (DFT) and time-dependent DFT calculations, as well as evaluation of the kinetics of the photophysical processes, revealed that appropriate placement of heavy atoms on the frontier orbitals facilitates intersystem crossing from the lowest singlet excited state to the triplet excited state, thus improving ΦΔ. [ABSTRACT FROM AUTHOR]

The electron transport was investigated at different temperatures and voltages for Fe-doped diamond-like carbon (DLC) thin films on Si substrate. The I-t curves show saturation at a low bias voltage, where the increasing rate and time needed for the saturation increase with the elevation of temperature. When the bias voltage exceeds a threshold voltage, the I-t curves show a three-stage process: the current increases, takes a plateau, and finally increases divergently in the last stage. These phenomena, which are not observed in the nondoped DLC/Si system, can be explained in terms of the electric-field-induced sp3-to-sp2 conversion, in which embedded Fe works as catalyst. [ABSTRACT FROM AUTHOR]

A simple approach is described for producing nanosized graphene based on the chemical oxidation of a graphene sheet followed by cutting of the sheet by using a scanning probe microscopic (SPM) manipulation method. The cutting procedure of the graphene sheet is a useful method for producing nanosized graphene with well-defined edges.

The electron transport for Fe-doped diamond-like carbon (DLC) thin films on Si substrate was studied at different temperatures and voltages. The three-stage I-t curve process not observed in the nondoped DLC/Si system could be elucidated in terms of the electric-field-induced [sp.sup.3]-to-[sp.sup.2] conversion, in which embedded Fe works as catalyst.