Ag2CO3/UiO-66(Zr) composite with enhanced visible-light promoted photocatalytic activity for dye degradation.

Because of their excellent properties, metal-organic frameworks (MOFs) are considered as ideal materials for the development of visible-light photocatalyst. Particularly, although increasing research interests have been put on MOF based photocatalysts, the MOF supported Ag2CO3 as photocatalyst has not been reported in the field of water treatment. In this study, a zirconium based MOF, UiO-66, was incorporated with Ag2CO3 through a convenient solution method and used for visible-light prompted dye degradation. Compared to the mixture of pristine UiO-66 and Ag2CO3, the developed Ag2CO3/UiO-66 composite exhibited enhanced photocatalytic activity to the degradation of rhodamine B (RhB) under visible-light irradiation. It was supposed that the participation of UiO-66 during the synthesis of Ag2CO3 was crucial for such improvement. In addition, the Ag2CO3/UiO-66 composite demonstrated good structural stability after the degradation experiment, and most of its photocatalytic activity was still preserved after the recycle test. Moreover, the photocatalytic mechanism of the Ag2CO3/UiO-66 composite was investigated and a possible pathway of RhB degradation was also proposed.

Enhanced Photocatalytic Activity of the AgI/UiO-66(Zr) Composite for Rhodamine†B Degradation under Visible-Light Irradiation.

Visible-light photocatalysts that degrade organic pollutants in an efficient and recyclable way are highly desirable for water treatment. In this study, UiO-66, a zirconium-based metal-organic framework, was conjugated with AgI to obtain a composite for use as photocatalyst. The AgI/UiO-66 composites with different composition ratios were synthesized by a simple solution method and exhibited remarkable activity for the degradation of rhodamine B (RhB) under visible-light irradiation. The scanning electron microscopy and X-ray diffraction results confirmed the outstanding structural stability of the AgI/UiO-66 photocatalysts. The photocatalytic stability of the AgI/UiO-66 composite was further examined by reusing AgI/UiO-66 for long-term dye degradation. The good stability of the AgI/UiO-66 composite can be attributed to the outstanding stability of the UiO-66 framework material, as well as the good interaction between AgI and the UiO-66 framework. The mechanism of the photocatalytic RhB degradation by AgI/UiO-66 was investigated by introducing different scavengers to compete for the possible reactive species involved in the degradation process.

Bisacenaphthopyrazinoquinoxaline derivatives: synthesis, physical properties and applications as semiconductors for n-channel field effect transistors.

Several bisacenaphthopyrazinoquinoxaline (BAPQ) based derivatives 1-3 were synthesized by condensation between the acenaphthenequinones and 1,2,4,5-tetraaminobenzene tetrahydrochloride. Their optical, electrochemical and self-assembling properties are tuned by different substituents. Among them, compound 3 possesses a homogeneously distributed low-lying LUMO due to the peripheral substitution with four cyano groups. The corresponding n-channel field effect transistors showed a field effect electron mobility of 5 × 10(-3) cm(2) V(-1) s(-1).

Design and synthesis of amphiphilic xanthone-based, membrane-targeting antimicrobials with improved membrane selectivity.

This work describes how to tune the amphiphilic conformation of α-mangostin, a natural compound that contains a hydrophobic xanthone scaffold, to improve its antimicrobial activity and selectivity for Gram-positive bacteria. A series of xanthone derivatives was obtained by cationic modification of the free C3 and C6 hydroxyl groups of α-mangostin with amine groups of different pKa values. Modified structures using moieties with high pKa values, such as AM-0016 (3b), exhibited potent antimicrobial properties against Gram-positive bacteria. Compound 3b also killed bacteria rapidly without inducing drug resistance and was nontoxic when applied topically. Biophysical studies and molecular dynamics simulations revealed that 3b targets the bacterial inner membrane, forming an amphiphilic conformation at the hydrophobic-water interface. In contrast, moieties with low pKa values reduced the antimicrobial activity of the parent compound when conjugated to the xanthone scaffold. This strategy provides a new way to improve "hits" for the development of membrane-active antibiotics that target drug-resistant pathogens.

Morphology evolution of polyaniline microstructures via reverse micelles and their hydrophobicity.

Polyaniline morphology evolution in toluene has been observed for the first time. Various structures, including one-dimensional open-ended microtubes, three-dimensional solid microspheres and two-dimensional novel solid microplates were controllably synthesized in the same reaction system. The structures obtained were sensitive to oxidant concentration and molar ratio of monomer to oxidant. Solid microplates were mainly formed on the glass beaker wall and bottom, while tubes and spheres were produced in solution by employing reverse micelles as soft templates. Studies on the effect of reaction temperature, mechanical stirring and the addition of more acid were also carried out. FTIR and UV-Vis results showed that the PANI products were in the emeraldine form. The PANI film prepared from spheres exhibited hydrophobic property due to its rough surface covered with nanoscale dots and the large distribution of sphere diameters.

Large-size linear and star-shaped dihydropyrazine fused pyrazinacenes.

Linear and star-shaped pyrazinacenes 1a-b and 2 were synthesized via condensation between a new building block 11 and pyrene tetraones or cyclohexaone. Compound 2 represents the largest star-shaped dihydropyrazine fused pyrazinacene reported so far. These largely expanded pyrazinacenes show good solubility and have a strong tendency to aggregate in both solution and thin films, indicating their potential applications for organic electronic devices.

H-shaped oligothiophenes with low band gaps and amphoteric redox properties.

H-shaped bridged oligothiophenes HT-1 and HT-2 were synthesized by two different approaches. Different from normal oligothiophenes, HT-1 and HT-2 showed low band gaps and amphoteric redox behaviors due to intramolecular charge transfer, which is further supported by time-dependent DFT calculations.

Synthesis, self-assembly, and charge transporting property of contorted tetrabenzocoronenes.

A facile route has been developed for the preparation of a new family of contorted 1.2,3.4,7.8,9.10-tetrabenzocoronenes (TBCs). A two-step cyclization reaction, i.e., oxidative photocyclization followed by FeCl(3)-mediated intramolecular cyclodehydrogenation, was carried out on the olefin precursors to obtain the final TBC compounds. These new TBC molecules have contorted conformation due to steric overcrowding as disclosed by single-crystal crystallographic analysis. Nevertheless, they showed extended π-conjugation compared with coronene and exhibited strong aggregation in solution. The thermal behavior and self-assembly of TBC-C8 in solid were studied by a combination of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). Compound TBC-C8 showed very good thermal and photostability and exhibited long-range ordered π-stacking in the bulk state. Moreover, uniform nanofibers with tens of micrometer length are formed in the drop-casted thin films. TBC-C8 also possesses a desirable HOMO energy level (-5.10 eV), which allows efficient charge injection from electrodes such as gold electrode. The charge carrier mobilities were determined by using the space-charge limited-current (SCLC) technique and high average hole mobility of 0.61 cm(2) V(-1) s(-1) was obtained for TBC-C8.

Oriented gold nanoparticle-polyaniline nanorods with nanofibers of controlled density on their surface.

We report here the preparation of fibrous gold nanoparticles-polyaniline (PANI) nanorod composite as an extension of our previous work in nanostructured conducting polymers. We have been able to control the amount of gold particles and the density of nanofibers covering the surface of the nanorods, which are characterized by selected area electron diffraction (SAED), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The morphology of PANI products is confirmed by both scanning electron microscopy (SEM) and TEM. The effect of reaction conditions on the morphology of PANI nanostructures is also studied. The chemical and electronic structures of the PANI nanorods are determined by Fourier transform IR (FTIR) and UV-vis spectrometry. I-V curves of as-prepared PANI nanostructures measured by conductive atomic force microscopy (c-AFM) indicate negative differential resistance (NDR) behavior.

Self-assembly of perfunctionalized beta-cyclodextrins on a quartz crystal microbalance for real-time chiral recognition.

This study reports the development of novel chiral sensors based on the self-assembly of perfunctionalized beta-cyclodextrins (beta-CD) on a quartz crystal microbalance transducer for real time chiral recognition. Ten chiral sensors immobilized with mercaptyl perfunctionalized beta-cyclodextrins were found to exhibit promising enantioselectivity in the gas phase. Well-defined sizes of molecular cavities of the modified beta-CDs associated with cooperative weak interactions with the host molecules afforded enhanced chiral discrimination. This study contributes to the realization of novel chiral sensors applicable for real-time recognition and analysis of enantiomeric alcohols and lactates.

Supramolecule-regulated photophysics of oligo(p-phenyleneethynylene)-based rod-coil block copolymers: effect of molecular architecture.

Three new topology-varied rod-coil block copolymers, comprising the same oligo(p-phenyleneethynylene) (OPE) rod components and the same coil components, were synthesized by atom-transfer radical polymerization. Their photophysical properties were systematically studied and compared in consideration of their solid-state structures and self-assembly abilities. These copolymers have similar intrinsic photophysical properties to the OPE rods, as reflected in dilute solution. However, their photophysical properties in the solid state are manipulated to be dissimilar by supramolecular organization. Wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM) data demonstrate that these copolymers possess different self-assembly abilities due to the molecular-architecture-dependent pi-pi interactions of the rods. Hence, the aggregates in the solid state are formed with a different mechanism for these copolymers, bringing about the discrepancy in the solid-state luminescent properties.

Controlled synthesis of Y-junction polyaniline nanorods and nanotubes using in situ self-assembly of magnetic nanoparticles.

Novel Y-junction polyaniline (PANI) nanorods and nanotubes (40-100 nm in diameter and a few micrometers in length) were selectively prepared, for the first time, using in situ self-assembly of water-soluble Fe3O4 nanoparticles coated with polyethylene glycol(5) nonylphenyl ether (NP5) and cyclodextrin (CD) as templates and pH control in an aqueous medium. The morphology of Fe3O4 nanoparticles and the PANI nanostructures (rods and tubes) was determined by TEM and the effects of reaction conditions on the morphology of PANI nanostructures were also studied. Characterization experiments including FTIR and X-ray diffraction were carried out to study the chemical and electronic structures of the PANI nanostructures.

Fabrication of polymeric hollow nanospheres, hollow nanocubes and hollow plates.

A facile strategy for fabricating polypyrrole-chitosan (PPy-CS) hollow nanostructures with different shapes (sphere, cube and plate) and a wide range of sizes (from 35 to 600 nm) is described. These hollow structures have been fabricated using silver bromide as a single template material for polymer nucleation and growth. PPy-CS hollow nanostructures are formed by reaction with an etching agent to remove the core. These hollow nanostructures have been extensively characterized using various techniques such as TEM, FT-IR, UV-vis, and XRD.

Synthesis and application of mono-6-ammonium-6-deoxy-beta-cyclodextrin chloride as chiral selector for capillary electrophoresis.

A facile synthetic approach for mono-6-amino-6-deoxy-beta-cyclodextrin (beta-CD-NH2) was proposed. Its hydroxy chloride salt, mono-6-ammonium-6-deoxy-beta-cyclodextrin chloride (beta-CD-NH3Cl) was further prepared and used for the enantioseparation of various anionic and ampholytic analytes by capillary electrophoresis (CE). The effect of background electrolyte (BGE) pH and selector concentration on the enantioseparation was studied. Results showed that beta-CD-NH3Cl displayed powerful chiral resolution ability towards anionic analytes. In addition, baseline separation of a standard mixture consisting of eight acids was achieved within 35 min.

Synthesis and application of single-isomer 6-mono(alkylimidazolium)-beta-cyclodextrins as chiral selectors in chiral capillary electrophoresis.

Novel single isomers of positively charged beta-CDs were prepared via nucleophilic substitution of 6-monotosyl-beta-CD with alkylimidazoles to afford 6-mono(alkylimidazolium)-beta-CD tosylates and then 6-mono(alkylimidazolium)-beta-CD chlorides by anion exchange. The chiral resolution abilities of these cationic CDs were studied by CE using dansyl (Dns)-amino acids as model analytes. From the experimental results, it was found that both resolution and selectivity of these cationic CDs were dependent on the following parameters: concentration of chiral selectors, pH of the running buffer, counteranions of the CDs, side chain length of the n-alkyl-imidazolium cation, temperature of the capillary column, and organic modifier used. The concentration of chiral selectors required for enantioseparation varied from 3 to 30 mM. The BGE pH played an important role in the resolution of Dns-amino acids. For acidic BGEs, chiral resolution increased with pH (4.0-6.0) and reached a local maximum at pH 6.0. However, better resolutions were obtained with basic phosphate buffer at pH 9.6. Methanol was found to be an effective organic modifier for the resolution of Dns-amino acids by CE.

Formation of ordered arrays of oriented polyaniline nanoparticle nanorods.

We report the preparation of ordered polyaniline (PANI) nanorod arrays in an aqueous medium. The oriented PANI nanorods (80-400 nm in diameter and 8-15 mum in length) were synthesized in the presence of hydrophilic Allura Red AC (ARAC) as the structure-directing agent and ammonium persulfate as an oxidant in HCl solution. The morphologies of the oriented PANI nanoparticle nanorods were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy images, and the effect of reaction conditions on the morphology of PANI nanostructures was also studied. On the basis of the result obtained from small-angle X-ray scattering, we propose that rodlike micelle arrays of ARAC-aniline are responsible for directing the formation of oriented PANI nanoparticle nanorods. SEM images and the data analysis of static and dynamic light scattering give supportive evidence to the formation of the PANI nanoparticle nanorods by an elongation process. The chemical and electronic structures of the PANI nanorods were also studied by Fourier transform IR and UV-vis spectrometries, respectively.

Facile fabrication of AgCl@polypyrrole-chitosan core-shell nanoparticles and polymeric hollow nanospheres.

A one-step sequential method for preparing AgCl@polypyrrole-chitosan core-shell nanoparticles and subsequently the formation of polypyrrole-chitosan hollow nanospheres is reported. The formation of the core and the shell is performed in one reaction medium almost simultaneously. Transmission electron microscopy (TEM) images show the presence of core-shell nanoparticles and hollow nanospheres. Ultraviolet-visible (UV-vis) studies reveal that AgCl was formed first followed by polypyrrole. X-ray diffration (XRD) and UV-vis studies show that AgCl was present in the core-shell nanoparticles and could be removed completely from the core.