Correlation between Nanoscale Elasticity, Semiconductivity, and Structural Order in Functionalized Polyaniline Thin Films.

The correlation between structural order, elasticity, and semiconductivity for butylthio-functionalized polyaniline (PANI-SBu) thin films was investigated using atomic force microscopy (AFM)-based techniques with X-ray diffraction (XRD) and scanning electron microscopy (SEM). After different stirring times, the thin films were cast from the solution of PANI-SBu in N-methyl-2-pyrrolidone that was continuously stirred at a constant rate of 150 rpm in an airtight round-bottom flask. According to the XRD and SEM results, the cross-sectional film structure evolved from being generally holey to highly lamellar with an increase in the stirring time. However, some new types of disordered structures began emerging beyond the optimal stirring time, possibly caused by the formation of disordered packing structures as contributed from the overoxidized polyaniline backbones during the additional stirring time. Moreover, according to the investigation results obtained using AFM-based techniques, the out-of-plane elastic moduli and charge mobilities of the PANI-SBu films were consistently smaller for disordered thin films and larger for structurally more ordered ones. The shear force resulting from the mechanical stirring of the PANI-SBu solution may gradually disentangle the polymer chains and thus help transform the individual polyaniline molecule from a coil-like chain conformation to a better extended rodlike chain conformation. Therefore, when cast into a film, the stretched polymer chains facilitate self-organization among the PANI-SBu backbones during the film formation process. Thus, an improved structural order in the film is attained. Our results demonstrate an unambiguous correlation between the structure order, elasticity, and conductivity in PANI-SBu thin films, which may have useful applications in conducting polymer-based flexible electronics.

Copper(I)-anilide complex [Na(phen)3][Cu(NPh2)2]: an intermediate in the copper-catalyzed N-arylation of N-phenylaniline.

Complex [Na(phen)(3)][Cu(NPh(2) )(2)](2), containing a linear bis(N-phenylanilide)copper(I) anion and a distorted octahedral tris(1,10-phenanthroline)sodium counter cation, has been isolated from the catalytic C-N cross-coupling reaction with the CuI/phen/tBuONa (phen=1,10-phenanthroline) catalytic system. Complex 2 can react with 4-iodotoluene to produce 4-methyl-N,N-diphenylaniline (3 a) with 70.6 % yield. In addition, 2 can work as an effective catalyst for C-N coupling under the same reaction conditions, thus indicating that 2 is the intermediate of the catalytic system. Both [Cu(NPh(2))(2)](-) and [Cu(NPh(2))I](-) have been observed by in situ electron ionization mass spectrometry (ESI-MS) under catalytic reaction conditions, thus confirming that they are intermediates in the reaction. A catalytic cycle has been proposed based on these observations. The molecular structure of 2 has been determined by single-crystal X-ray diffraction analysis.

Disease antigens detection by silicon nanowires with the efficiency optimization of their antibodies on a chip.

Enhancing the efficiency of antibody protein immobilized on a silicon nanowire-based chip for their antigens detection is reported. An external electric field (EEF) is applied to direct the orientation of antibodies during their immobilization on a chip. Atomic force microscopy (AFM) is used to measure the binding forces between immobilized antibody and targeting antigen under the influence of EEF at different angles. The maximum binding force under a specific angle (optimal angle; oa) of EEF (maxEEFoa) implies the optimal orientation of the antibodies on the chip. In this report, two different cancer carcinoembryonic antigen (CEA)-related cell adhesion molecules 5 (CEACAM5) & 1 (CEACAM1) were used for the examples of disease antigen detection. maxEEFoa of anti-CEACAM5 or anti-CEACAM1 immobilized on a general chip was firstly determined. Spectroscopy of AFM revealed that both binding forces were the largest ones with their antigens when maxEEFoa was applied as compared with no or other angles of EEF. These antibody proteins accompanied with the application of EEF were secondly immobilized on silicon-nanowires (n = 1000) and the field effects were measured (∆I) as their target antigens were approached. Results showed that ∆I was the largest ones when maxEEFoas (225°/270° and 135°/180° for anti-CEACAM5 and anti-CEACAM1, respectively) were applied as compared with other angles of EEF. These observations imply that the silicon nanowires together with the application of maxEEFoa as detection tools could be applied for the cancer diagnostics in the future.

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.

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.

Efficient pretreatment of lignocellulosic biomass with high recovery of solid lignin and fermentable sugars using Fenton reaction in a mixed solvent.

BACKGROUND: Pretreatment of biomass to maximize the recovery of fermentable sugars as well as to minimize the amount of enzyme inhibitors formed during the pretreatment is a challenge in biofuel process. We develop a modified Fenton pretreatment in a mixed solvent (water/DMSO) to combine the advantages of organosolv and Fenton pretreatments. The hemicellulose and cellulose in corncob were effectively degraded into xylose, glucose, and soluble glucose oligomers in a few hours. This saccharide solution, separated from the solid lignin simply by filtration, can be directly applied to the subsequent enzymatic hydrolysis and ethanol fermentation. RESULTS: After the pretreatment, 94% carbohydrates were recovered as soluble monosaccharide (xylose and glucose) and glucose oligomers in the filtrates, and 87% of solid lignin was recovered as the filter residue. The filtrates were directly applied to enzymatic hydrolysis, and 92% of raw corncob glucose was recovered. The hydrolysates containing the glucose and xylose from the enzymatic hydrolysis were directly applied to ethanol fermentation with ethanol yield equals 79% of theoretical yield. The pretreatment conditions (130 °C, 1.5 bar; 30 min to 4 h) are mild, and the pretreatment reagents (H2O2, FeCl3, and solvent) had low impact to environment. Using ferrimagnetic Fe3O4 resulted in similar pretreatment efficiency and Fe3O4 could be removed by filtration. CONCLUSIONS: A modified Fenton pretreatment of corncob in DMSO/water was developed. Up to 94% of the carbohydrate content of corncob was recovered as a saccharide solution simply by filtration. Such filtrate was directly applied to the subsequent enzymatic hydrolysis and where 92% of the corncob glucose content was obtained. The hydrolysate so obtained was directly applied to ethanol fermentation with good fermentability. The pretreatment method is simple, and the additives and solvents used have a low impact to the environment. This method provides the opportunity to substantially maximize the carbohydrate and solid lignin recovery of biomass with a comparatively green process, such that the efficiency of biorefinery as well as the bioethanol production process can be improved. The pretreatment is still relatively energy intensive and expensive, and further optimization of the process is required in large-scale operation.

Ligand free copper(I)-catalyzed synthesis of diaryl ether with Cs2CO3 via a free radical path.

Complexes [Cu(I)(2,4-dimethylphenoxy)2](-) (A) and [Cu(II)(2,4-dimethylphenoxy)2(p-tolyl)](-) (B) were observed by in situ electrospray ionization mass spectrometry (ESI-MS) analysis of the ligand free copper(I)-catalyzed C-O coupling reaction using Cs2CO3 under the catalytic reaction conditions indicating that they could be intermediates in the reaction. The radical scavenger cumene retarded the reaction. Catalytic cycles involving a free radical path are proposed based on these observations.

Reactivity of [K3(phen)8][Cu(NPh2)2]3--a possible intermediate in the copper(I)-catalyzed N-arylation of N-phenylaniline.

Complex [K3(phen)8][Cu(NPh2)2]3 (1, phen = phenanthroline) was isolated from the catalytic C-N cross coupling reaction based on the CuI-phen-tBuOK catalytic system. Complex 1 can react with 4-iodotoluene to give 4-methyl-N,N-diphenylaniline (3a) in 50% yield (based on all available NPh2(-) ligands of complex 1). In addition, 1 can also work as an effective catalyst for the C-N coupling reactions under the same reaction conditions, indicating that 1 may be an effective intermediate of the catalytic system. In the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), a radical scavenger, the stoichiometric reaction between complex 1 and 4-iodotoluene was significantly quenched to give a low yield of 12%. The results suggest that the radical path dominates in the reaction, with (phen)KNPh2 as the possible radical source. The structures of 1 and (phen)KNPh2 were both determined by single crystal X-ray diffraction studies.

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.

A copper(II) complex as an intermediate of copper(I)-catalyzed C-N cross coupling of N-phenylaniline with aryl halide by in situ ESI-MS study.

Complexes [Cu(NPh(2))(2)](-), [Cu(NPh(2))I](-) and K[Cu(phen)(NPh(2)) (p-tolyl)](+) were observed by in situ electrospray ionization mass spectrometry (ESI-MS) analysis of the copper(I)-catalyzed C-N coupling reaction under the catalytic reaction condition indicating that they are intermediates in the reaction. A catalytic cycle composed of a free radical path and a 2e oxidative addition path is proposed based on these observations.

A serendipitous C-C bond formation reaction between Michael donors and diiminoquinoid ring assisted by quaternary ammonium fluoride.

An efficient C-C bond formation reaction assisted by a fluoride ion has been identified for N,N'-diphenyl-1,4-phenylenediimine with the compounds having an active methylene group. The reaction follows the typical Michael addition fashion and proceeds to completion within 1 h at 70 degrees C in acetonitrile in the presence of tetrabutylammonium fluoride (TBAF), while the same reaction failed to proceed in the absence of a fluoride anion. The new finding reported herein also offers an unprecedented method for a direct functionalization of polyaniline backbone with versatile functional alkyl groups.

The different electronic natures displayed by the alkylthio groups in simple and higher conjugated aniline systems.

Systematic studies based on 1H NMR and 13C NMR indicated that the alkylthio group behaves as a weak electron-withdrawing group in a simple aniline system like 2-butylthioaniline, while the same alkylthio group clearly acted as a resonance electron-donating group in higher conjugated aniline trimer systems, like butylthio-substituted PDA (mono-PDA) and dibutylthio-substituted PDA (2,6-diPDA). The formation of 2,6-diPDA as the major byproduct during the preparation of mono-PDA from PDI and butane-1-thiol provided additional support for the resonance electron donating nature of the butylthio group in these aniline trimer systems. Furthermore, CV studies also clearly indicated that the redox potential E degrees (vs. SCE) of the aniline trimer systems decreased with the increase in the number of butylthio groups, further confirming the electron-donating nature of the butylthio group in these higher conjugated trimer systems.