A structurally ordered thiophene-thiazole copolymer for organic thin-film transistors

This paper reports a new donor-acceptor copolymer semiconductor, PTBTh, comprising bithiophene and bithiazole where the regular coplanar structure and the intramolecular charge transfer are expected to increase the opportunity for --- stacking and charge transport. The AFM image shows lamellar stacking of the polymer on the surface. The field-effect transistor (FET) properties of PTBTh have been evaluated by a bottom-contact/bottom-gate TFT configuration. The device showed a high hole mobility of 1.14×10-2 cm2 V-1 s-1 and a current on/off ratio of 3×105 with the polymer thin film annealed at a mild temperature of 120 ℃ when measured under ambient conditions.     

Development of Science China Chemistry during 2008–2012: From the perspective of Special Issues/Topics

1 Introduction Science China Press Co.,Ltd.(SCP) is a science and technology(ST) journal publishing company of the Chinese Academy of Sciences(CAS).SCP publishes 16 kinds of academic journals,Science China Series and Chinese Science Bulletin,of which 8 journals are in English and 8 in     

Molecular dynamics study on the relationships of modeling, structural and energy properties with sensitivity for RDX-based PBXs

In this paper,a primary model is established for MD(molecular dynamics) simulation for the PBXs(polymer-bonded explosives) with RDX(cyclotrimethylene trinitramine) as base explosive and PS as polymer binder.A series of results from the MD simulation are compared between two PBX models,which are represented by PBX1 and PBX2,respectively,including one PS molecular chain having 46 repeating units and two PS molecular chains with each having 23 repeating units.It has been found that their structural,interaction energy and mechanical properties are basically consistent between the two models.A systematic MD study for the PBX2 is performed under NPT conditions at five different temperatures,i.e.,195 K,245 K,295 K,345 K,and 395 K.We have found that with the temperature increase,the maximum bond length(L max) of RDX N N trigger bond increases,and the interaction energy(E N-N) between two N atoms of the N-N trigger bond and the cohesive energy density(CED) decrease.These phenomena agree with the experimental fact that the PBX becomes more sensitive as the temperature increases.Therefore,we propose to use the maximum bond length L max of the trigger bond of the easily decomposed and exploded component and the interaction energy E N-N of the two relevant atoms as theoretical criteria to judge or predict the relative degree of heat and impact sensitivity for the energetic composites such as PBXs and solid propellants.     

Highly sensitive and selective chemosensor for Cu2+ detection based on a N-propargyl rhodamine 6G-hydrazide derivative

A novel fluorescence "turn-on" probe for Cu2+ detection has been designed based on a Cu2+ triggered spirolactam ring-opening reaction.The synthetic probe is a double-responsive fluorescent and colorimetric Cu2+-specific sensor.In aqueous solution,it exhibits high selectivity and excellent sensitivity.With a significant color change visible to the naked eye at the concentration of 3 μM(ca.0.19 mg/L),about one magnitude lower than the WHO(World Health Organization) recommended level(2.0 mg/L) for Cu2+ ions in drinking water,the probe could be used to monitor Cu2+ ions in drinking water.     

Photofragment translational spectroscopy of ICl near 304 and 280 nm: Observation of an intense hot band effect

The photodissociation dynamics of ICl has been studied near 304 and 280 nm on a simple miniature time of flight (mini-TOF) photofragment translational spectrometer with a short pulse of a weak acceleration field. An intense hot band effect was observed. Many small peaks were resolved in each photofragment translational spectrum (PTS). Based on simulations, the principal peaks were assigned not only to the different photodissociation channels (1) I + Cl, (2) I + Cl*, (3) I* + Cl, or (4) I* + Cl*, but also to the different chlorine isotopes (35Cl and Cl). Moreover, some extra peaks showed the existence of an intense hot 37 band effect from vibrationally excited ICl molecules, though only a few percent of ICl molecules remained in the vibrationally excited states in our supersonic molecular beam. Based on the spectra near 304 nm, the quantum yield Ф of each channel, the curve crossing, and the branching fraction σ from each transition state were determined.     

Azomethine ylide-formation from N-phthaloylglycine by photoinduced decarboxylation: A theoretical study

In this work, we report the first CASPT2//CASSCF study of the mechanism of the photodecarboxylation of N-phthaloylglycine. The charge transfer excited state S CT ( 1∏∏*) is initially populated upon irradiation at 266 nm. As a result of a fast internal conversion to the lowest excited singlet state S CT-N ( 1∏∏*), this state becomes a favorable precursor state for proton transfer, which triggers decarboxylation. Actually, the excited state intramolecular proton transfer (ESIPT) and decarboxylation processes proceed in an asynchronous concerted way. The ESIPT process is accomplished in the S CT-N ( 1∏∏*) state, but the CO 2 molecule is finally formed in the ground state via the S CT /S 0 conical intersection. Azomethine ylide is formed in the ground state as a complex with CO 2 . A barrier of ~15 kcal/mol indicates that azomethine ylide is stable in the ground state, which is consistent with the experimental findings. This work provides mechanistic details about the formation of azomethine ylide by photoreaction of N-phthaloylglycine.     

Synthesis and Self‐Assembly of Dihydroxyperylene Bisimides for the Tuning of Photophysical Properties

The synthesis of 1,10‐dihydroxyperylene bisimides by nucleophilic substitution of brominated perylene bisimide is described. 1,10‐Dihydroxyperylene bisimides formed J aggregates in nonpolar solvents and showed a clearly redshifted absorption band. The solvent polarity also influenced the hydrogen bond with the hydroxyl group, and thus, the photophysical properties of perylene bisimide. The photophysical properties of these dihydroxyperylene perylene bisimides can also be tuned by changing charge transfer from the hydroxyl groups to the perylene core through the introduction of metal ions.     

Solid Supramolecular Architecture of a Perylene Diimide Derivative for Fluorescent Enhancement

A new p‐phenylenevinylene‐linked perylene diimide has been synthesized and self‐assembled for the formation of zero‐dimensional molecular aggregate structures of nanospheres and vesicles through solvent tuning. The solid‐state optical properties induced by a special wavelength laser were studied and the results indicated excellent fluorescent enhancement properties. The emission intensity of these aggregates increased with elongation of the laser irradiation time. Based on the analysis of variable‐temperature ¹H NMR spectra, DFT calculations, and the single‐crystal structure of the linkage group, a conformation‐dependent fluorescent enhancement mechanism could be demonstrated. The mechanism is different from the fluorescent bleaching of normal solid‐state fluorescent materials and offers potential applications in optical devices.     

Dispersion of Reduced Graphene Oxide in Multiple Solvents with an Imidazolium‐Modified Hexa‐peri‐hexabenzocoronene

An imidazolium‐modified hexa‐peri‐hexabenzocoronene derivative (HBC‐C₁₁‐MIM[Cl^?]) was designed and synthesized as a stabilizer to fabricate reduced graphene oxide (RGO). The resulting RGO/HBC‐C₁₁‐MIM[Cl^?] hybrid shows excellent dispersivity (5.0 mg mL^?1) and stability in water. RGO/HBC‐C₁₁‐MIM[Cl^?] was comprehensively characterized by using atomic force microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and Raman spectroscopy, thus revealing that one HBC‐C₁₁‐MIM[Cl^?] group can stabilize about 178 carbon atoms on the graphene sheets. The obtained hybrid film exhibits a high conductivity of 286 S m^?1. Furthermore, the HBC‐C₁₁‐MIM[Cl^?]‐modified RGO sheets can be readily dispersed in polar organic solvents upon exchange of the hydrophilic Cl^? ions for hydrophobic bis(trifluoromethylsulfonyl) amide (NTf₂^?) ions.