Chien-Chung Han

Study of anode work function modified by self-assembled monolayers on pentacene/fullerene organic solar cells

The authors investigated the anode work function modified by series of self-assembled monolayers comprising alkanethiols and perfluorinated alkanethiols with different alkyl lengths on pentacene/fullerene thin-film organic solar cells. Via selecting different types of self-assembled molecules, the anode work function can be tailored for modifying the interfacial barrier. The measured open-circuit voltages indicated reduced anode work function that tends to form Schottky contact. The maximal open-circuit voltage and short-circuit current were measured to be 0.4V and 17.7mA∕cm2, respectively, in the case of anode work function modified by perfluorinated alkanethiols. The power conversion efficiency is 2.24%.

A novel method for making highly dispersible conducting polymer and concentric graphitic carbon nano-spheres based on an undoped and functionalized polyaniline

A novel method has been successfully established for making highly dispersible conducting polymer nano-spheres with conveniently controllable sizes directly from preformed, undoped, butylthio-functionalized polyaniline (Pani-SBu) in the absence of any stabilizer, surfactant, and/or functional protonic acid dopant. The success of this approach stemmed from the unique ability of Pani-SBu (prepared via the concurrent reduction and substitution method) to form a nanometer-sized spherical micelle-like self-assembly in the selected co-solvent medium as confirmed by dynamic light scattering studies. With further help of the dithiol treatment, the resultant soft non-isolable micelle-like self-assembly could then be converted into rigid, stable, and isolable nano-spheres. Preliminary studies indicated that these highly ordered undoped Pani-SBu nano-spheres could also serve as ideal precursor materials for making concentric graphitic carbon nano-spheres at relatively low processing temperatures.

Directly Thiolated Modification onto the Surface of Detonation Nanodiamonds

An efficient method for modifying the surface of detonation nanodiamonds (5 and 100 nm) with thiol groups (-SH) by using an organic chemistry strategy is presented herein. Thiolated nanodiamonds were characterized by spectroscopic techniques, and the atomic percentage of sulfur was analyzed by elemental analysis and X-ray photoelectron spectroscopy. The conjugation between thiolated nanodiamonds and gold nanoparticles was elucidated by transmission electron microscopy and UV-vis spectrometry. Moreover, the material did not show significant cytotoxicity to the human lung carcinoma cell line and may prospectively be applied in bioconjugated technology. The new method that we elucidated may significantly improve the approach to surface modification of detonation nanodiamonds and build up a new platform for the application of nanodiamonds.

Chain-growth cationic polymerization of 2-halogenated thiophenes promoted by Brønsted acids

Bronsted acids are found to be effective and generally applicable catalysts for inducing the cationic chain-growth polymerization of a wide variety of 2-halogenated-3-substituted-thiophenes with hydrogen, alkyl, alkylthio, alkoxy, and dialkoxy substituent groups. The effectiveness of the cationic polymerization depends on the acid strength and the electron density of the 2-halothiophene monomer. For the most electron-rich monomer, like EDOT, the polymerization can be initiated essentially with any acid that is stronger than acetic acid. While for the electron-poor 2-bromothiophene, it only works with the strongest acid, e.g., trifluoromethanesulfonic acid. Using this new polymerization method, highly solution-processable and conductive poly(alkylthiothiophene)s with a conductivity greater than 180 S cm−1 can be conveniently prepared. Control experiments indicate that Lewis acid like BF3 and SnCl4 (0.5 equiv.) can also induce the polymerization of 3-alkylthio-2-bromothiophenes in a similar fashion, but their polymerization failed totally in the presence of a trace amount of acid scavenger (e.g., <0.1 equiv. NEt3). On the other hand, similar polymerizations with Bronsted acid did not show any noticeable adverse effect under the same condition. The polymerization with Bronsted acid may involve the coupling between the monomer (as the nucleophile) and its protonated form (as the electrophile), followed by the elimination of HBr (or HCl) to convert the unstable nonconjugated dimeric intermediate 11 (Scheme 2) into the more stable conjugated chain growing species 12, which then initiates the polymerization by repeating the propagation steps of coupling with additional monomers, and then undergoes HX-elimination to regenerate the chain-growing centres.

Simple and highly efficient direct thiolation of the surface of carbon nanotubes

We established a highly efficient and simple method to directly functionalize the surface of carbon nanotubes (CNTs) with thiol groups (–SH). The –SH groups on the surface of the CNTs were characterized using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), and transmission electron microscopy (TEM). The TEM indicated that gold nanoparticles (Au NPs) or other metals can be attached to thiolated CNTs (CNT–SHs) through thiol–metal bonding. Hence, the proposed approach can be used for developing self-assembled materials, sensors, catalysts, and CNT nanodevices.

Low-dose paeonol derivatives alleviate lipid accumulation

Here, we present a series of novel paeonol derivatives that prevent lipid accumulation at lower doses and exhibit improved water solubility. According to SAR analysis results, 1-(4-methoxy-2-(2-(piperidin-1-yl)ethoxy)phenyl)ethanone (6a) and 4′-methoxy-2′-[(phenylsulfonyl)oxy]acetophenone (7a) demonstrate as good inhibition ability at low-dose (10 μg mL−1) as that of paeonol at high-dose (100 μg mL−1). In addition, compounds 6a and 7a can be synthesized quantitatively with simple preparation methods. Hence, we believe that compounds 6a and 7a are potentially suitable antiatherogenic compounds for future drug development.

Cross C–S coupling reaction catalyzed by copper(I) N-heterocyclic carbene complexes

Copper(I) N-heterocyclic carbene has a good activity towards aryl halides and was used as a model complex to study the catalytic cycle of Cu(I) to catalyze the cross C–S coupling reaction because the N-heterocyclic carbene has a strong electron donating property, and ligand dissociation can be avoided. Free radical scavenger cumene does not retard the yield of the reaction indicating that the catalytic reaction goes through a non free radical path. Switching the solvent from toluene to DMF lowered the yield of the reaction. DFT calculation shows that the activation of aryl halide is the rate determining step, and the activation energy is higher for the reaction in DMF than in toluene. A plausible catalytic cycle is proposed with the support of DFT calculation.

A new and easy method for making micrometer-sized carbon tubes

Highly crystalline and single-walled micrometer-sized carbon tubes several centimeters in length have been prepared via the pyrolysis of composite fibers consisting of a thermally stable polypyrrole skin layer and a thermally degradable PET core fiber.

One-Step, Effective, and Cascade Syntheses of Highly Functionalized Cyclopentenes with High Diastereoselectivity

Tetrabutylammonium fluoride works as an effective organocatalyst for the cycloaddition between phenacylmalononitriles and electron-deficient olefins (having substituent groups of NO2, CHO, and COR), providing a facile synthetic route to versatile multifunctionalized cyclopentenes having an allylic quaternary carbon center bearing both cyano and carboxamide groups with high yields and high diastereoselectivity. Preliminary studies reveal that these functionalized cyclopentenes are convenient precursors for making α-cyano-functionalized cyclopentadienone oximes.

Cascade and Effective Syntheses of Functionalized Tellurophenes

A one-pot and transition-metal-catalyst-free synthetic strategy to construct functionalized tellurophenes has been developed. Substituted 1,1-dibromo-1-en-3-ynes are smoothly converted to tellurophenes with telluride salts in high yield via a series of cascade reactions through reductive debromination, hydrotelluration, nucleophilic cyclization, and aromatization. Close inspection of the results clearly showed that the reactivity of in situ prepared telluride salts are significantly influenced by the polarity of the solvent system and the electronic nature of the substituent on the enyne substrate. This method reports the first direct synthesis of 3-aryltellurophenes in high yields at room temperature. This novel reaction strategy is also found to be a promising synthetic method for multisubstituted tellurophenes and selenophenes.