New TTF and bis-TTF containing thiophene units: Electrical properties of the resulting salts

Series of new TTF and bis-TTF containing a thiophene ring as a substituent or as a spacer group were prepared by using a palladium-catalyzed cross-coupling reaction from tributylstannyl–trimethyltetrathiafulvalene (tMeTTF–SnBu₃) and different halogeno and dihalogenothiophene derivatives. The reducing power of each new precursor was determined by cyclic voltammetry. Radical cations salts and charge transfer complexes of the donors with TCNQ were prepared and characterized. The electrical conductivity of these materials was measured and discussed in terms of (electronic) structure.     

Organic single crystalline micro- and nanowires field-effect transistors of a tetrathiafulvalene (TTF) derivative with strong π–π orbits and S⋯S interactions

Tetrathiafulvalene (TTF) was one of the most widely studied heterocyclic systems. However, TTF itself was easily oxidized, which induced the low stability and limited its potential applications. Here, a TTF derivative, 2,3,6,7-tetrakis(2-cyanoethylthio)tetrathiafulvalene (TCE-TTF), was synthesized. It was found that single crystalline micro- and nanowires of TCE-TTF were easily obtained by simple casting due to the enhanced π–π overlapping and S?S interaction. The thermal and vacuum stability analyses revealed TCE-TTF was much better than TTF. Single crystalline micro- and nanowires field-effect transistors were also fabricated by in situ dropping method. The typical mobility and on/off ratio were ～0.02 cm²/V s and ～10³, which predicted great potential applications of organic nanowires electronics.     

In the search of an electron transfer between π-donors and C60: the bis-linking of tetrathiafulvalene (TTF) to C60

In order to realize the bis-linking of tetrathiafulvalene (TTF) to one or two C₆₀, and to reach the dyad compounds 1 and 2, the [4 + 2] Diels-Alder reactions of C₆₀ with orthoquinodimethanic derivatives of 1,3-dithioles 5a,b or TTF 9 are studied.     

A series of stable salts of the oxidized donors TTF, o-Me2TTF,TMTTF, and TTF(SCH2CH2CN)4

Reactions of the organic donors tetrathiafulvalene (TTF), o-dimethyltetrathiafulvalene (o-Me₂TTF), tetramethyltetrathiafulvalene (TMTTF), and tetrathiafulvalene tetrathiolate [TTF(SCH₂CH₂CN)₄] with oxidizing agents of suitable potential resulted in the formation of stable salts in which the donors are present in their monocationic radical forms. The salts presented herein represent a series of reagents containing oxidized chalcofulvalene donors that can be used as starting materials for metathesis reactions with other cations. All of the salts were characterized by X-ray crystallography and UV–vis–NIR spectroscopy.     

Synthesis and properties of a series of new asymmetrical tetrathiafulvalene derivatives

A series of new asymmetrically substituted tetrathiafulvalene (TTF) derivatives, a charge transfer (CT) complex, and several related symmetrical TTF derivatives were synthesized. The compounds were characterized by elemental analysis, ¹H NMR spectra, IR spectra, and electron ionization (EI) or negative-ion fast atom bombardment (FAB) mass spectral analysis. UV-Vis spectra of the new asymmetrical TTF derivatives and the CT complex in solution were investigated. In addition, mixed conducting Langmuir-Blodgett (LB) films were constructed from the asymmetrical TTF derivatives by admixing with an equimolar arachidic acid.     

Residual protective effect of <Emphasis Type="Italic">o</Emphasis>-oxyazomethine derivatives against iron corrosion in 1 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

The residual protective effect of n-component mixtures of o-oxyazomethine derivatives at the corrosion of iron in 1 M H₂SO₄ decreases with time and an increase in temperature of the environment and increases with an increase in the polarity of substituent groups in the molecules and the inhibitor concentration in the solution. These regularities are interpreted based on the principle of the linear free-energy relation.     

Doped and de-doped polypyrrole nanowires by using a BMIMPF6 ionic liquid

We electrochemically synthesized π-conjugated polypyrrole (PPy) nanowires by using an environmentally stable and recyclable ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆), as a dopant, based on an anodic alumina oxide (Al₂O₃) nanoporous template. The de-doped states of the PPy nanowires were obtained from doped PPy nanowires through cyclic voltammetry (CV) using a solution of the catalyst in the BMIMPF₆ ionic liquid. We confirmed the de-doped states of PPy nanowires based on a decrease of the bipolaron peak of the ultraviolet and visible (UV–vis) absorbance spectra. The formation of PPy nanowires was visualized by using scanning electron microscopy and transmission electron microscopy. We studied the optical and structural properties of the doped and de-doped PPy nanowires by UV–vis absorbance and Fourier transform-infrared spectra. Our work included obtaining a laser confocal microscope Raman spectra for a single strand of the PPy nanowires.     

Tris-fused tetrathiafulvalenes (TTF): highly conducting single-component organics and metallic charge-transfer salt

Tris-fused tetrathiafulvalene (TTF) derivatives, TTC_n-TTPY, 2,2′-bis[4,5-alkylthio-(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalenylidene] with four alkylthio chains [C_nH_2n+1S: n=3–5] are prepared and the structural and conducting properties are investigated. Crystals of the neutral molecules show very low electrical resistivity (400 Ω cm) as single-component pure organic materials. Irrespective of the alkylthio chain length, the crystal structures are so-called β″-type consisting of uniform stacks of the tris-fused TTF parts. Iodine-doped TTC₃-TTPY exhibits metallic conductivity down to liquid helium temperature.     

Template-based,near-ambient synthesis of crystalline metal-oxide nanotubes,nanowires and coaxial nanotubes

In response to a growing need for metal-oxide nanotubes and nanowires for nanoelectronic applications and size-effect studies, crystalline nanotubes and nanowires in a range of metal oxides have been synthesized at near-ambient conditions and without the application of heat treatments, pressure or an external electric field. Specifically, the mechanisms of formation of crystalline TiO₂ nanotubes and nanowires from flourine-based liquid precursors inside anodic aluminum oxide templates have been elucidated. This method can be extended to synthesizing nanotubes/nanowires of other crystalline metal oxides, such as ZrO₂, SnO₂ and FeOOH. Using sequential deposition, TiO₂/ZrO₂ coaxial nanotubes have been synthesized. In principle, the methods outlined here could be used to fabricate crystalline nanotubes and nanowires of tailored dimensions in other metal oxides. The ability to synthesize, at near-ambient conditions, crystalline metal-oxide nanotubes and nanowires of tailored geometries represents a clear advantage in terms of minimal equipment requirements, low cost and possible incorporation of biomolecules and temperature-sensitive moieties.     

Fabrication of Ag/polypyrrole coaxial nanocables through common ions adsorption effect

According to the common ions adsorption effect, Ag⁺ ions will be adsorbed onto the closest surface of silver nanowires after being immersed in AgNO₃ solution. This makes the surface of silver nanowires become the active sites to oxidize pyrrole monomer to form PPy sheath without adding other oxidizing agent. The results of FT-IR and UV–vis spectra show the formation of PPy chain when pyrrole monomer was added to the reaction mixture containing the disposed silver nanowires. TEM images further prove that the Ag/polypyrrole (PPy) coaxial nanocables have been fabricated. The thickness of PPy sheath can be controlled by adjusting the concentration of AgNO₃ aqueous solution, which used to dispose silver nanowires. To some extent, the thickness of PPy layer would increase with the increasing of the concentration of AgNO₃ solution. After the adsorbed Ag⁺ ions on the surface of silver nanowires reach to the saturation, the thickness of PPy layer would not change greatly with continuously increasing of AgNO₃ concentration.     

Solution-based synthesis of ZnO nanoparticle/CdS nanowire heterostructure

The heterostructure of ZnO nanoparticle (NP)/CdS nanowire (NW) was successfully fabricated by a two-step chemical solution method. The first, CdS nanowires were synthesized by a simple solvothermal route. The second, ZnO nanoparticles were grown on the surface of CdS nanowires in a chemical solution of Zn(CH₃COO)₂·2H₂O and anhydrous ethanol at 200 °C. The heterostructure of synthesized ZnO NP/CdS NW was characterized by transmission electron microscopy (TEM). The effects of reaction conditions, such as different reaction time of CdS nanowires synthesized and deposition reaction time were investigated. Moreover, the formation mechanism of the ZnO NP/CdS NW heterostructure has been phenomenologically discussed.     

Syntheses and properties of π-conjugated polymers containing tetrathiafulvalene in the polymer backbone

Syntheses of π-conjugated polymers containing tetrathiafulvalene (TTF) in the polymer backbone were successfully attempted from dibrominated TTF derivatives and diboronic acid derivatives using the Suzuki coupling reaction. The present polymers showed high molecular weight (12,900–36,700) and excellent solubility in conventional organic solvents, suggesting the effect of the introduction of an alkoxy chain. Electrochromic phenomenon was observed using spin-coated film of the polymers on ITO glass plate, and the color of the film changed reversibly from yellow to red purple depending on the applied potential. The response of the electrochromic change was rapid and reproduced over thousand times. Optoelectrochemical measurement for spin-coated film revealed that the color change was responsible for the electronic state of the TTF moiety, and the observed charge-transfer band was caused by the intermolecular interaction between TTF moieties in the different polymer backbones.     

Single-component organic conductors based on neutral betainic radicals of N-methyl substituted dioxo- and aminooxo-pyrimido-fused TTFs

New dioxo- and aminooxo-pyrimido-fused tetrathiafulvalene (TTF) derivatives, whose pyrimido-rings are substituted by methyl group, were synthesized. In the crystal structures of their tetrabutylammonium salts, complementary hydrogen-bonds inherent in pyrimido-fused TTF derivatives were inhibited by the methyl substitution, and the crystals were constructed by the segregated motifs of cations and anions. Betainic radicals prepared by one-electron oxidation of tetrabutylammonium salts exhibited relatively high conductivities (ca. 10⁻⁴ S cm⁻¹ at room temperature) as single-component organic molecules. The optical measurement of betainic radicals showed considerably low-energy charge-transfer absorption between radical molecules compared to those of conventional TTF systems, indicating the reduction of on-site Coulomb repulsion.     

Synthesis and electrochemical behaviors of novel TTF derivatives bearing thiazole groups

At present work, five new tetrathiafulvalene (TTF) derivatives bearing two or four thiazole groups are prepared, which have been characterized by ¹H NMR, IR, MS spectra, elemental analysis and X-ray analysis for 6. The preliminary electrochemical properties of them are investigated by cyclic voltammetry (CV) and two one-electron quasi-reversible waves with redox potentials are observed.     

Synthesis and structure of charge transfer salts of tetrathiafulvalene (TTF) and tetramethyl-TTF with 2,4,7-trinitro and 2,4,5,7-tetranitro-9-fluorenone

Charge transfer salts of tetrathiafulvalene (TTF) and tetramethyltetrathiafulvalene (TMTTF) with the organic acceptors 2,4,7-trinitro-9-fluorenone and 2,4,5,7-tetranitro-9-fluorenone have been prepared and characterized. The compounds (TTF)[TENF] (1), (TTF)₃[TRNF]₂ (2) and (TMTTF)[TRNF] (3) contain mixed stacks of alternating TTF and nitrofluorenone units. Surprisingly, the degree of charge transfer that occurs in these salts is not controlled solely by the redox potentials of the building blocks, but apparently also by the most effective intermolecular interactions in the solid, as determined from the crystal structures obtained. These three compounds exhibit poor electron delocalization and therefore they behave as diamagnetic insulators.     

HOPG上ALD沉积Al2O3介电薄膜的生长行为研究

本文采用原子层沉积(ALD)的方法,选择三甲基铝(TMA)和H₂O₂作为反应前驱体,在高定向热解石墨(HOPG)基体上沉积Al₂O₃。系统研究了反应温度和生长周次对Al₂O₃生长行为的影响。研究表明：受HOPG表面饱和成键的影响,Al₂O₃在衬底表面处形核困难,在生长初期主要表现为台阶处择优生长,其形态为线状结构。当沉积100周次Al₂O₃时,其中在沉积温度为50 °C、150 °C和200 °C时呈现为纳米线状结构,而在100 °C时呈现为非连续薄膜。随着生长周次的增加,不同温度下沉积态Al₂O₃都趋于形成连续薄膜,表明其生长行为发生了由三维岛状生长模式向二维平面生长模式的转变。分析认为,生长模式的转变是由纳米线状结构横向生长造成的;横向生长速率主要受生长温度影响。拉曼结果表明：沉积后的石墨烯层结构未受影响,可保留其原有的优越性能。     

Growth of Sb2S3 nanowires synthesized by colloidal process and self-assembly of amorphous spherical Sb2S3 nanoparticles in wires formation

We report the organic synthesis and growth of antimony sulfide (Sb₂S₃) amorphous nanospheres to nanowires via a simple, colloidal synthetic method. Amorphous Sb₂S₃ nanospheres self-assembly in wires formation was dispersed in isopropyl alcohol. With increased heating time, Sb₂S₃ nanospheres grew into Sb₂S₃ nanowires, probably involving both mechanisms of Ostwald-ripening and spherical nanoparticle self-organization through oriented-attachment of individual nanoparticles. Also, the as-synthesized Sb₂S₃ nanowires with different heating times (0, 5 and 10 min.) from the moment of appearance of the Sb₂S₃ precipitate were analyzed. The observed nanowires become longer with increased heating time and are around 100 nm in diameter and 10?C20 ??m in length. UV-Vis absorption spectroscopy reveals that the optical band-gap energy of the Sb₂S₃ nanowires is independent of the heating times and is found to be ??1.5?C1.6 eV. The optical band-gap energy found for amorphous Sb₂S₃ nanospheres was also ??1.5 eV. The structure of Sb₂S₃ samples was refined down to R-factors of 10.82, 11.76 and 12.08%. The refinement showed that Sb₂S₃ powder belongs to the orthorhombic type with space group Pbnm (no. 62) and that Sb₂S₃ nanowires grow along the [010] direction.     

Synthesis of tetra-silylated tetrathiafulvalene derivatives TTF(SiR2H)4 (R = Me,Ph): Novel assembling ligands for the construction of bimetallic transition metal complexes

The HR₂Si-functionalized tetrathiafulvalene (TTF) ligand TTF(SiR₂H)₄ (R = Me 2a; R = Ph 2b) have been synthesized and the molecular structure of 2a determined. The reactivity of the four Si–H bonds for oxidative addition reactions has been exploited. Thus, the bimetallic platinum–silicon complex [(PPh₃)₂Pt{(Me₂Si)₂TTF(SiMe₂)₂}Pt(PPh₃)₂] 3 incorporating TTF(SiMe₂H)₄ as bridging unit has been assembled by oxidative addition across [Pt(PPh₃)₂(CH₂CH₂)]. Electrochemical investigations by means of cyclic voltammetry reveals, for the complex 3, a strong cathodic shift of the two redox processes of the TTF core compared with those of 2a.     

Orientation of nanowires consisting of poly(3-hexylthiophene) using strong magnetic field

Nanowires consisting of regioregular poly(3-hexylthiophene) (P3HT) as a conducting polymer were prepared using p-xylene. Magnetic processing of the nanowires was carried out using two superconducting magnets with horizontal (B_max = 8 T) and vertical (B_max = 10 T) directions. The formation of the nanowires was confirmed by atomic force microscopy (AFM) measurement. The results from the AFM images and the polarized absorption spectra on glass plates indicated that the nanowires partly oriented themselves with their long axes, which are parallel to the π–π stacking direction, being perpendicular to the magnetic field. The magnetic orientation is most likely ascribed to anisotropy in the magnetic susceptibilities of the ordered P3HT in the nanowires.     

Fabrication of Cu-induced networks of linear nanostructures on different length scales

Scanning electron microscopy and atomic force microscopy revealed that the deposition Cu onto VSe₂ substrates in ultra-high vacuum leads to the self-organized formation of linear nanostructures, nanowires and nanotunnels, on the substrate surface. The nanowires and nanotunnels are approximately equi-axed and form networks with a mesh width much larger than their diameter. Surprisingly, systematic increase of the Cu coverage studied here does not simply increase the thickness of the nanowires and nanotunnels, but induces the formation of further, distinct networks with increased feature size and increased mesh width. At very high Cu coverages, eventually, we obtained a hierarchy of apparently independent nanowire and nanotunnel networks on different length scales. A model is presented for the micromechanism that leads to this complex arrangement of nanostructures.