Crystal packing motifs of oligothiophenes end-capped with N-containing aryls

Oligothiophenes (OThs) end-capped with 3-quinolyl or pyridyl with nitrogen atom at meta-, ortho- or para-position were synthesized. The single-crystal structures of the resulting molecules, i.e., o-PyTh4, m-PyTh4, p-PyTh4, QuTh2, and QuTh3, were successfully determined by single-crystal X-ray analysis. Pyridyl end-capped OThs; o-PyTh4, m-PyTh4, and p-PyTh4, adopt the different herringbone packing arrangement in crystals depending on the position of the nitrogen atom because of the presence of weak C-H center dot center dot center dot N hydrogen bonds. The p-PyTh4 molecules are linked each other along the long axis of the molecules to form the extended chains by C-H center dot center dot center dot N dimer synthon. For m-PyTh4, the C-H center dot center dot center dot N interactions two-dimensionally extend through C-H center dot center dot center dot N trimer synthon.

Film Morphology and Molecular Orientation in Oligothiophene-fluorene Films

The effects of processing conditions on film morphology and molecular orientation were studied for a novel conjugated fluorene-bithiophene oligomer, oligo(9,9-dioctylfluorene-alt-bithiophene) (OF8T2). Depending on the method of film preparation, OF8T2 molecules adopt different orientations in the films. X-ray diffraction peak at 4.9 degrees of the OF8T2 film deposited from petroleum ether/dichloromethane mixture is attributed to a layering distance between sheets of OF8T2 chains, which are separated by the octyl side chains. Preferred orientation is clearly inferred through the absence of peaks corresponding to pi-pi stacking.

Tin (IV) phthalocyanine oxide: An air-stable semiconductor with high electron mobility

Air-stable n-type field effect transistors were fabricated with an axially oxygen substituted metal phthalocyanine, tin (IV) phthalocyanine oxide (SnOPc), as active layers. The SnOPc thin films showed highly crystallinity on modified dielectric layer, and the electron field-effect mobility reached 0.44 cm(2) V-1 s(-1). After storage in air for 32 days, the mobility and on/off ratio did not obviously change. The above results also indicated that it is an effective approach of seeking n-type semiconductor by incorporating the appropriate metal connected with electron-withdrawing group into pi-pi conjugated system.

Morphology and crystalline transition of poly (3-butylthiophene) associated with its polymorphic modifications

Poly (3-butylthiophene) (P3BT) is a much less studied conjugated polymer despite its high crystallizability and thus excellent electrical property. In this work, morphology of P3BT at different crystalline polymorphs and solvent/thermal induced phase transition between form I and U modifications have been intensively investigated by using optical microscopy, electron microscopy, differential scanning calorimetry, and X-ray diffraction. It is shown that a direct deposition from carbon disulfide (CS2) at fast evaporation results in P3BT crystals in form I modification, giving typical whiskerlike morphology. In contrast, low evaporation rate from CS, leads to formation of form II crystals with spherulitic morphology, which is so far scarcely observed in polythiophene.

Ultrathin-film growth of para-sexiphenyl (II): Formation of large-size domain and continuous thin film

The large-size domain and continuous para-sexiphenyl (p-6P) ultrathin film was fabricated successfully on silicon dioxide (SiO2) substrate and investigated by atomic force microscopy and selected area electron diffraction. At the optimal substrate temperature of 180 degrees C, the first-layer film exhibits the mode of layer growth, and the domain size approaches 100 mu m(2). Its saturated island density (0.018 mu m(-2)) is much smaller than that of the second-layer film (0.088 mu m(-2)), which begins to show the Volmer-Weber growth mode.

Formation of reversible shell cross-linked micelles from the biodegradable amphiphilic diblock copolymer poly(L-cysteine)-block-poly(L-lactide)

A novel biodegradable diblock copolymer, poly(L-cysteine)-b-Poly(L-lactide) (PLC-b-PLLA), was synthesized by ring-opening polymerization (ROP) of N-carboxyanhydride of beta-benzyloxycarbonyl-L-Cysteine (ZLC-NCA) with amino-terminated Poly(L-lactide) (NH2-PLLA) as a macroinitiator in a convenient way. The diblock copolymer and its precursor were characterized by H-1 NMR, Fourier transform infrared (FT-IR), gel permeation chromatography (GPC), and X-ray photoelectron spectroscopy (XPS) measurements. The length of each block polymer could be tailored by molecular design and the ratios of feeding monomers.

Ultrathin-film growth of para-sexiphenyl (I): Submonolayer thin-film growth as a function of the substrate temperature

The para-sexiphenyl (p-6P) monolayer film induces weak epitaxy growth (WEG) of disk-like organic semiconductors, and their charge mobilities are increased dramatically to the level of the corresponding single crystals [Wang et al., Adv. Mater. 2007, 19, 2168]. The growth behavior and morphology of p-6P monolayer film play decisive roles on WEG. Here, we investigated the growth behavior of p-6P submonolayer film as a function of the substrate temperature. Its growth exhibited two different mechanisms at high and low substrate temperature.

Weak epitaxy growth of metal-free phthalocyanine on p-sexiphenyl monolayer and double-layer films

Weak epitaxy growth (WEG) can afford high-mobility thin films of disk-like organic semiconductor of which mobility is up to the level of the corresponding single crystals. We investigated the WEG behavior and mechanism of planar phthalocyanine in the model system of metal-free phthalocyanine (H2Pc) grown on p-sexiphenyl (p-6P) ultrathin films (monolayers and double layers). Highly oriented H2Pc films with molecules standing up exhibited two kinds of different in-plane orientations, i.e., three sets of in-plane orientations and only one set of in-plane orientation, on p-6P monolayer and double-layer films, respectively.

Ambipolar organic heterojunction transistors with various p-type semiconductors

Ambipolar transport has been realized in organic heterojunction transistors with metal phthalocyanines, phenanthrene-based conjugated oligomers as the first semiconductors and copper-hexadecafluoro-phthalocyanine as the second semiconductor. The electron and hole mobilities of ambipolar devices with rod-like molecules were comparable to the corresponding single component devices, while the carrier mobility of ambipolar devices with disk-like molecules was much lower than the corresponding single component devices.

Phthalocyanato tin(IV) dichloride: An air-stable, high-performance, n-type organic semiconductor with a high field-effect electron mobility

Phthalocyanato tin(IV) dichloride, an axially dichloriniated MPc, is an air-stable high performance n-type organic semiconductor with a field-effect electron mobility of up to 0.30 cm(2) V-1 s(-1). This high mobility together with good device stability and commercial availability makes it a most suitable n-type material for future organic thin-film transistor applications.

Length dependence of electron conduction for oligo(1,4-phenylene ethynylene)s: A conductive probe-atomic force microscopy investigation

The dependence of electron conduction of oligo(1,4-phenylene ethynylene)s (OPEs) on length, terminal group, and main chain structure was examined by conductive probe-atomic force microscopy (CP-AFM) via a metal substrate-molecular wire monolayer-conductive probe junction. The electron transport in the molecular junction was a highest occupied molecule orbital (HOMO)-mediated process following a coherent, non-resonant tunneling mechanism represented by the Simmons equation.

Probing Charge Transport of Ruthenium-Complex-Based Molecular Wires at the Single-Molecule Level

A ruthenium(II) bis(sigma-arylacetylide)-complex-based molecular wire functionalized with thiolacetyl alligator clips at both ends (OPERu) was used to fabricate gold substrate-molecular wire-conductive tip junctions. To elucidate the ruthenium-complex-enhanced charge transport, we conducted a single-molecule level investigation using the technique-combination method, where electronic delay constant, single-molecular conductance, and barrier height were obtained by scanning tunneling microscopy (STM) apparent height measurements, STM break junction measurements, and conductive probe-atomic force microscopy (CP-AFM) measurements, respectively.

含二硫键多肽的基质辅助激光解析电离飞行时间质谱研究

The determination of disulfide bonds becomes an important aspect of obtaining a comprehensive understanding of the chemical structure of a protein. Numerous experimental methods have been developed for the determination of disulfide bonds in proteins. Modern mass spectrometry has developed as an important tool for the analysis of disulfide bond patterns due to its advantages of being simple, rapid and sensitive. The dissociations of the disulfide bonds were detected during the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. These fragment ions were attributed to prompt fragmentation or “in-source decay” rather than “post-source decay”. For the double disulfide bonds, ions of plus sulfur and minus sulfur atoms corresponding to cleavages at different sites within the carbon-sulfur-sulfur-carbon disulfide bonds were also observed.

Ultrasound-promoted chiral fluorescent organogel

In this paper, we have described a chiral binaphthyl-based fluorescent organogel. Very interestingly, similar to sonocrystallisation of organics, ultrasound can promote the gelation while it cannot occur spontaneously at relatively high temperature or low concentration. The fluorescence enhancement of the gel obtained via ultrasound irradiation is observed. In solution there exist rapid dynamic equilibria between (S)-1 oligomers. The association interactions both between gelator molecules and between solvent and gelator molecules could together effect the helical growth of distorted (S)-1 nanocrystals.

Monodisperse Co-oligomer Approach toward Nanostructured Films with Alternating Donor-Acceptor Lamellae

A series of donor-acceptor (D-A) co-oligomers with oligo(fluorene-alt-bithiophene) and perylene diimide as donor and acceptor segments, respectively, have been designed and synthesized. They can self-assembly into alternating D-A lamellar nanostructured films with the periods depending on the molecular length. These films have been successfully used in fabrication of high-performance single-molecular solar cells with power conversion efficiency up to 1.50%.