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Biomedical subjects

Daoben Zhu

Publications and source records attributed to Daoben Zhu.

At least 37 records · Page 2Linked to original sources
PubMed2006

Hybrid organic-inorganic conductor with a magnetic chain anion: kappa-BETS2[Fe(III)(C2O4)Cl2] [BETS = bis(ethylenedithio)tetraselenafulvalene].

The synthesis, crystal structure, and electrical, optical, and magnetic properties of kappa-BETS2[Fe(III)(C2O4)Cl2], where BETS is bis(ethylenedithio)tetraselenafulvalene, are reported. The black plate crystals consist of parallel donor layers, two per unit cell, displaying a kappa-type packing of BETS(0.5+) within the bc plane and anionic magnetic chains, [Fe(C2O4)Cl2-]n, running along the c axis. It displays metallic behavior down to 4.2 K, and analysis of the optical reflectivity data gives unscreened plasma energies of 0.69 eV (E parallel c) and 0.40 eV (E perpendicular c). The optical anisotropy is larger than that seen for other kappa phases and is described well by transfer integrals obtained from extended Hückel calculations. However, the transfer integrals need to be scaled down uniformly by a factor of 1.21 to reproduce the absolute experimental plasma frequencies. The band structure consists of a one-dimensional (1D) band and a hole pocket, characteristics of kappa phases. The magnetic properties were modeled by the sum of a 1D antiferromagnetic chain contribution from the d spins of Fe3+, a temperature-independent paramagnetic contribution, and a Curie impurity term. At 4.5 K, there is a signature of long-range magnetic ordering to a canted-antiferromagnetic state in the zero-field-cooled-field-cooled magnetizations, and at 2 K, a small hysteresis loop is observed.

Journal Article↗
PubMed2006

Synthesis and characterization of pyrrolidin-2-one fused N-confused calix[4]phyrins.

[reaction: see text] A facile method for the synthesis of pyrrolidin-2-one fused N-confused calix[4]phyrins is provided by reactions of 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin with acyl chlorides in the presence of triethylamine. The (1)H NMR and UV-vis spectra of products indicate their loss of macrocyclic aromaticity.

Journal Article↗
PubMed2006

Binaphthalene molecules with tetrathiafulvalene units: CD spectrum modulation and new chiral molecular switches by reversible oxidation and reduction of tetrathiafulvalene units.

By combining the features of binaphthalene and tetrathiafulvalene (TTF), compounds 1-4 were designed for studies of chiral molecular switches. Absorption and CD spectral studies clearly indicate that the CD spectra resulting from axial chiral binaphthalene units can be modulated through the redox reactions of TTF units, which means new chiral molecular switches can be established on the basis of binaphthalene molecules with TTF units. The reference compound 5, which has one TTF unit rather than two as in the case of compounds 1, 3, and 4, failed to show such property, hinting that the presence of two or more TTF units is required for the realization of CD spectrum modulation. In addition, the manner of the CD spectrum modulation has been found to be dependent on the way TTF units are linked to the binaphthalene skeleton, in terms of the linker length, the positions for substitution, and the number of TTF units.

Journal Article↗
PubMed2006

Suzuki coupling reaction of 1,6,7,12-tetrabromoperylene bisimide.

1,6,7,12-Tetrabromoperylene-3,4,9,10-tetracarboxylic acid bisanhydride and the corresponding tetrabrominated perylene bisimide were first synthesized with high yields. The Suzuki coupling reaction of novel tetrabromoperylene bisimide with phenylbonoric acid was studied. The four bromines in the bay position of the perylene core were substituted successfully to yield 1,6,7,12-teraphenylperylene bisimide. The photochemical properties of the novel perylene bisimides were studied and presented.

Journal Article↗
PubMed2006

Tuning the magnetic behavior via dehydration/hydration treatment of a new ferrimagnet with the composition of K0.2Mn1.4Cr(CN)6 x 6H2O.

A new complex (1) of Prussian blue analogue with the composition of K0.2Mn1.4Cr(CN)6 x 6H2O was prepared and characterized structurally as well as magnetically. The crystal structure of complex 1 was determined by X-ray diffraction analysis. The results indicate that complex 1 consists of a 3D cubic lattice similar to those of Mn3[Cr(CN)6]2 x xH2O, Mn3[Co(CN)6]2 x xH2O, Cd3[Cr(CN)6]2 x xH2O, and Cd3[Co(CN)6]2 x xH2O. Magnetic measurements show that complex 1 is a ferrimagnet with T(c) = 66 K. It is interesting to note that the magnetic behavior of complex 1 can be substantially modulated through a dehydration/rehydration treatment. The T(c) value of this ferrimagnet increases to 99 K after dehydration reaching a 23.4% weight loss, and it decreases back to 66 K after the dehydrated sample reabsorbs water molecules.

Journal Article↗
PubMed2006

Assembly of a tetrathiafulvalene-anthracene dyad on the surfaces of gold nanoparticles: tuning the excited-state properties of the anthracene unit in the dyad.

Due to the unique features of the tetrathiafulvalene (TTF) unit, such as the electron-donating ability and presence of methylthio groups, dyad 1 can be assembled on the surfaces of gold nanoparticles, as indicated by absorption, electrochemical, and fluorescent-spectral studies. Dyad 1 can also be disassembled by the addition of thiols. Assembly of dyad 1 on the surfaces of gold nanoparticles leads to the formation of a triad (A1-D-A2), which in turn modulates the photoinduced electron-transfer process within dyad 1. Accordingly, the fluorescence intensity of dyad 1, after assembly with gold nanoparticles, increases, and the fluorescence lifetime is prolonged. Furthermore, the assembly of dyad 1 on gold nanoparticles facilitates photodimerization of the anthracene units of dyad 1. Both fluorescence and photodimerization are associated with the excited-state behavior of the anthracene unit, thus it may be concluded that the excited-state properties of the anthracene unit can be tuned upon complexation with gold nanoparticles.

Journal Article↗
PubMed2006

Electron transport in self-assembled polymer molecular junctions.

A molecular junction of a poly(p-phenyleneethynylene)s derivative with thioacetate end groups (TA-PPE) was fabricated by self-assembling. Nanogap electrodes made by electroplating technique was used to couple thiol end groups of TA-PPE molecules. Room temperature current-voltage characteristics of the molecular junction exhibited highly periodic, repeatable, and identical stepwise features. First-principles calculations suggest that one possibility for the equidistant step is due to the opening of different conducting channels that corresponds to the unoccupied molecular orbitals of the polymer in the junction. It is interesting to see that an 18 nm long polymer is of quantized electronic structures and behaves like a quantum transport device.

Journal Article↗
PubMed2006

Novel butterfly pyrene-based organic semiconductors for field effect transistors.

Novel butterfly pyrene derivatives functionalized with trifluoromethylphenyl and thienyl aromatic groups in the 1-, 3-, 6- and 8-positions of pyrene cores and have been synthesized by Suzuki coupling reactions, and their crystal structures, optical and electrochemical properties investigated; additionally, the field effect transistor using as the active material exhibited a p-type performance.

Journal Article↗
PubMed2006

A new method to synthesize complicated multi-branched carbon nanotubes with controlled architecture and composition.

Here we develop a simple method by using flow fluctuation to synthesize arrays of multi-branched carbon nanotubes (CNTs) that are far more complex than those previously reported. The architectures and compositions can be well controlled, thus avoiding any template or additive. A branching mechanism of fluctuation-promoted coalescence of catalyst particles is proposed. This finding will provide a hopeful approach to the goal of CNT-based integrated circuits and be valuable for applying branched junctions in nanoelectronics and producing branched junctions of other materials.

Catalysis↗
PubMed2006

High-yield self-assembly of flower-like ZnO nanostructures.

High-yield three-dimensional (3D) flower-like nanostructures self-assembled from 1 D ZnO nanorods and nanotubes are experimentally demonstrated. The Zn and O terminated crystal planes of ZnO nanorods results in positively and negatively charged top (001) and bottom (00-1) surfaces, respectively. The nanorods self-assembled into 3D nanostructures via the electrostatic interaction between the crystal planes with opposite charges. Moreover, on the basis of the different stability of polar and nonpolar planes in wurtzite-type ZnO, the nanorods based 3D nanostructures transformed into nanotubes based ones spontaneously. This provides a new approach to prepare multi-dimensional materials without the necessity to employ any external intervention.

Crystallization↗
PubMed2005

Synthesis and characterization of 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole functionalized tetraaryloxy perylene bisimide and metal-directed self-assembly.

[structure: see text] New perylene bisimide dyes bearing 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole receptor units with different spacers have been synthesized and characterized. The fluorescence and electronic properties of these compounds have been studied. MALDI-TOF, UV-vis, and fluorescence titration experiments proved that monotopic perylene bisimide ligands could be assembled into dimmers by Fe(III) coordination. The coordination properties of the ditopic perylene bisimide ligands have also been studied preliminarily. Furthermore, the SEM images indicated that well-defined nanoscale structures could be fabricated by self-assembly due to metal ion coordination and pi-pi stacking interactions of perylene rings with the help of a proper spacer.

Journal Article↗
PubMed2005

Stable, reproducible nanorecording on rotaxane thin films.

Stable, reversible conductance transitions and memory effects were observed in solid-state rotaxane-based Langmuir-Blodgett (LB) thin films. Taking advantage of the switching property, we have achieved reproducible nanometer-scale recording dots on rotaxane LB films via voltage application using a scanning tunneling microscope probe. The stable and easily controlled conductance switching makes the rotaxanes a hopeful candidate for nanorecording.

Journal Article↗
PubMed2005

Energy transfer switching in a bistable molecular machine.

[reaction: see text] A novel [2]rotaxane, containing pyrene and perylene bisimide as both stoppers and photoactive units, has been prepared. The shuttling of the protonated macrocycle switched the energy transfer (EN) from a pyrene moiety to a perylene moiety, which resulted in changes of fluorescence of the perylene moiety.

Journal Article↗
PubMed2005

Novel carboxylated oligothiophenes as sensitizers in photoelectric conversion systems.

Novel carboxylated oligothiophenes with different thiophene units were designed and synthesized as photosensitizers in dye-sensitized solar cells (DSSCs) for efficient opto-electric materials. The introduction of -COOH into thiophene molecules can lead to a red shift of UV-visible absorption, increase light-harvesting efficiency, and enhance photoinduced charge transport by forming efficient covalent bonds to the substrate surface. A red shift of the absorption spectrum of oligothiophene is also achieved by the increase in the number of thiophene units. The DSSCs based on the oligomers have excellent photovoltaic performances. Under 100 mW cm(-2) irradiation a short-circuit current of 10.57 mA cm(-2) and an overall energy conversion efficiency of 3.36 % is achieved when pentathiophene dicarboxylated acid was used as a sensitizer. The incident photo-to-current conversion efficiency (IPCE) has a maximum as high as 80 %. In addition, photovoltage and photocurrent transients show that slow charge recombination in DSSCs is important for efficient charge separation and excellent photoelectric conversion properties of the oligomers. These initial and promising results suggest that carboxylated oligothiophenes are efficient photosensitizers.

Journal Article↗
PubMed2005

A novel multisignaling optical-electrochemical chemosensor for anions based on tetrathiafulvalene.

[structure: see text] A multisignaling optical-electrochemical receptor for anions based on a triad with anthracene and TTF units was prepared. It showed a unique selectivity for fluoride ion over various anions with dramatic fluorescence enhancement in neutral condition and displayed a special recognition of H2PO4(-) in electrochemical studies with remarkable cathodic displacement of the first oxidation potential E(ox)1 of the TTF unit.

Anions↗
PubMed2005

A highly pi-stacked organic semiconductor for field-effect transistors based on linearly condensed pentathienoacene.

We present the synthesis and characterization of a fused-ring compound, dithieno[2,3-d:2',3'-d']thieno[3,2-b:4,5-b']dithiophene (pentathienoacene, PTA). In contrast to pentacene, PTA has a larger band gap than most semiconductors used in organic field-effect transistors (OFETs) and therefore is expected to be stable in air. The large pi-conjugated and planar molecular structure of PTA would also form higher molecular orders that are conductive for carrier transport. X-ray diffraction and atomic force microscopy experiments on its films show that the molecules stack in layers with their long axis upright from the surface. X-ray photoelectron spectroscopy suggests that there are no chemical bonds at the PTA/Au interface. OFETs based on the PTA have been constructed, and their performances as p-type semiconductors are also presented. A high mobility of 0.045 cm(2)/V s and an on/off ratio of 10(3) for a PTA OFET have been achieved, demonstrating the potential of PTA for application in future organic electronics.

Electric Conductivity↗