Time filter

Source Type

Li J.,Hong Kong Polytechnic University | Yan F.,Hong Kong Polytechnic University | Miao Q.,Chinese University of Hong Kong | Miao Q.,Institute of Molecular Functional Materials
Chemistry of Materials | Year: 2010

Quinones are well-known as organic oxidizing reagents in organic synthesis and biological systems, but their ability of accepting electrons was rarely explored in connection with n-type organic semiconductors. Here, we report a comprehensive study on two groups of π-deficient pentacenequinones, fluorinated pentacenequinones and N-heteropentacenequinones, highlighting their electronic structures,molecular packing, and n-channel thin film transistors. It is found that replacingH atoms of pentacenequinone with F atoms or replacing C atoms with N can lower the lowest unoccupied molecular orbital (LUMO) energy level of pentacenequinone to yield n-type organic semiconductors with the field effect mobility up to higher than 0.1 cm2V-1s-1 in thin film transistors. A comparison between the two groups of quinones in terms of their electronic structures and molecular packing has led to interesting findings on the roles of electron-withdrawing moieties in tuning frontier molecular orbitals and p-stacking. Another interesting finding on the molecular packing is the quadruple weak hydrogen bonds, which link the neighboring p-stacks of quinones. This study suggests that π-deficient quinones would be a general design for n-type organic semiconductors. ©2010 American Chemical Society.

Xuan S.,Institute of Molecular Functional Materials | Xuan S.,Hefei University of Technology | Wang F.,Institute of Molecular Functional Materials | Wang Y.-X.J.,Interventional Imaging | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2011

This article reports the fabrication of mesoporous Fe3O 4 nano/microspheres with a high surface area value (163 m 2/g, Brunauer-Emmett-Teller) and demonstrates their use for drug loading, release, and magnetic resonance imaging (MRI). These monodispersed, mesoporous Fe3O4 nano/microspheres with controllable average sizes ranging from 50 to 200 nm were synthesized using a Fe 3O4/poly(acrylic acid) hybrid sphere template and subsequent silica shell formation and removal. We found that the SiO2 coating is a crucial step for the successful synthesis of uniform mesoporous Fe3O4 nano/microspheres. The as-synthesized mesoporous Fe3O4 nanospheres show a high magnetic saturation value (Ms = 48.6 emu/g) and could be used as MRI contrast agents (r 2 = 36.3 s-1 mM-1). Trypan blue exclusion and MTT assay (see Supporting Information) cytotoxicity analyses of the nanospheres based on HepG2 and MDCK cells showed that the products were biocompatible, with a lower toxicity than lipofectamine (positive control). Hydrophilic ibuprofen and hydrophobic zinc(II) phthalocyanine drug loading into mesoporous Fe 3O4 nanospheres and selected release experiments were successfully achieved. The potential use of mesoporous Fe3O 4 nanospheres in biomedical applications, in light of the nano/microspheres' efficient drug loading and release, MRI, and low cytotoxicity, has been demonstrated. It is envisaged that mesoporous Fe 3O4 nanospheres can be used as drug carriers and MRI contrast agents for the reticuloendothelial system; they can also be delivered locally, such as via a selective catheter. © 2011 American Chemical Society.

Liu J.,Hong Kong University of Science and Technology | Lam J.W.Y.,Hong Kong University of Science and Technology | Jim C.K.W.,Hong Kong University of Science and Technology | Ng J.C.Y.,Hong Kong University of Science and Technology | And 9 more authors.
Macromolecules | Year: 2011

The atom-economical alkyne polyhydrothiolations of aromatic diynes (1) and dithiol (2) catalyzed by rhodium complexes proceed smoothly under mild conditions at room temperature in a regioselective manner, producing sole anti-Markovnikov products of poly(vinylene sulfide)s (3) with high molecular weights (Mw up to 31500) and stereoregularities (E content up to 100%) in high yields (up to 95.2%). The stereostructures of the polymers are readily tuned by engineering control on the sequential addition of monomers during the polymerization process and postmanipulation by light irradiation. All the poly(vinylene sulfide)s are soluble in common organic solvents and exhibit good film-forming ability and high optical transparency. The functional pendants in 1 have endowed 3 with novel properties such as aggregation-enhanced emission characteristics, optical limiting to harsh laser pulses, and ceramization capability to semiconducting nanoparticles. The polymers are thermal and UV curable, enabling the fabrication of fluorescent photopatterns. Their thin films show high refractive indices (nD = 1.75-1.70) and low optical dispersions (down to 0.006) at telecom important wavelengths. Their refractive indices vary with their stereostructures and can be modulated by UV irradiation. © 2010 American Chemical Society.

Chen L.,South China University of Technology | Jiang Y.,Hong Kong University of Science and Technology | Nie H.,South China University of Technology | Hu R.,South China University of Technology | And 6 more authors.
ACS Applied Materials and Interfaces | Year: 2014

In this work, two tailored luminogens (TPE-NB and TPE-PNPB) consisting of tetraphenylethene (TPE), diphenylamino, and dimesitylboryl as a Ï-conjugated linkage, electron donor, and electron acceptor, respectively, are synthesized and characterized. Their thermal stabilities, photophysical properties, solvachromism, fluorescence decays, electronic structures, electrochemical behaviors, and electroluminescence (EL) properties are investigated systematically, and the impacts of electron donor-acceptor (D-A) interaction on optoelectronic properties are discussed. Due to the presence of a TPE unit, both luminogens show aggregation-induced emission, but strong D-A interaction causes a decrease in emission efficiency and red-shifts in photoluminescence and EL emissions. The luminogen, TPE-PNPB, with a weak D-A interaction fluoresces strongly in solid film with a high fluorescence quantum yield of 94%. The trilayer OLED [ITO/NPB (60 nm)/TPE-PNPB (20 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm)] utilizing TPE-PNPB as a light emitter shows a peak luminance of 49a"‰993 cd m-2 and high EL efficiencies up to 15.7 cd A-1, 12.9 lm W-1, and 5.12%. The bilayer OLED [ITO/TPE-PNPB (80 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm)] adopting TPE-PNPB as a light emitter and hole transporter simultaneously affords even better EL efficiencies of 16.2 cd A-1, 14.4 lm W-1, and 5.35% in ambient air, revealing that TPE-PNPB is an eximious p-type light emitter. © 2014 American Chemical Society.

Hong Y.,Institute of Molecular Functional Materials | Hong Y.,Clear Technology | Meng L.,Institute of Molecular Functional Materials | Chen S.,Hong Kong University of Science and Technology | And 11 more authors.
Journal of the American Chemical Society | Year: 2012

Amyloid fibrillation of proteins is associated with a great variety of pathologic conditions. Development of new molecules that can monitor amyloidosis kinetics and inhibit fibril formation is of great diagnostic and therapeutic value. In this work, we have developed a biocompatible molecule that functions as an ex situ monitor and an in situ inhibitor for protein fibrillation, using insulin as a model protein. 1,2-Bis[4-(3-sulfonatopropoxyl)phenyl]-1,2- diphenylethene salt (BSPOTPE) is nonemissive when it is dissolved with native insulin in an incubation buffer but starts to fluoresce when it is mixed with preformed insulin fibril, enabling ex situ monitoring of amyloidogenesis kinetics and high-contrast fluorescence imaging of protein fibrils. Premixing BSPOTPE with insulin, on the other hand, inhibits the nucleation process and impedes the protofibril formation. Increasing the dose of BSPOTPE boosts its inhibitory potency. Theoretical modeling using molecular dynamics simulations and docking reveals that BSPOTPE is prone to binding to partially unfolded insulin through hydrophobic interaction of the phenyl rings of BSPOTPE with the exposed hydrophobic residues of insulin. Such binding is assumed to have stabilized the partially unfolded insulin and obstructed the formation of the critical oligomeric species in the protein fibrillogenesis process. © 2011 American Chemical Society.

Hong Y.,Institute of Molecular Functional Materials | Chen S.,Hong Kong University of Science and Technology | Leung C.W.T.,Institute of Molecular Functional Materials | Lam J.W.Y.,Institute of Molecular Functional Materials | And 8 more authors.
ACS Applied Materials and Interfaces | Year: 2011

Terpyridine-containing tetraphenylethenes (TPEs) are synthesized and their optical and metal sensing properties are investigated. They are practically nonluminescent in the solution state but become highly emissive as nanoparticle suspensions in poor solvents or thin films in the solid state, demonstrating a novel phenomenon of aggregation-induced emission (AIE). The emission of the nanoaggregates of TPEs is pH-sensitive: it is decreased and eventually quenched upon protonation of their terpyridine units because of their AIE nature. The TPEs can work as "turn-off" fluorescent chemosensors for metal ions and display different fluorescence responses to various metal ions. A characteristic red shift in the emission spectra is observed in the presence of Zn2+, which facilitates the discrimination of Zn2+ from other metal ions. Because of the metal-to-ligand-charge-transfer process, terpyridine-substituted TPEs display an obvious magenta color upon selectively binding with Fe2+, allowing a rapid identification of Fe2+ in the aqueous media by naked eyes. © 2011 American Chemical Society.

Xuan S.-H.,Institute of Molecular Functional Materials | Xuan S.-H.,Hefei University of Technology | Lee S.-F.,Institute of Molecular Functional Materials | Lau J.T.-F.,Institute of Molecular Functional Materials | And 11 more authors.
ACS Applied Materials and Interfaces | Year: 2012

Novel high magnetization microspheres with porous γ-Fe 2O 3 core and porous SiO 2 shell were synthesized using a templating method, whereas the size of the magnetic core and the thickness of the porous shell can be controlled by tuning the experimental parameters. By way of an example, as-prepared γ-Fe 2O 3@meso-SiO 2 microspheres (170 nm) display excellent water-dispersity and show photonic characteristics under externally applied a magnetic field. The magnetic property of the γ-Fe 2O 3 porous core enables the microspheres to be used as a contrast agent in magnetic resonance imaging with a high r 2 (76.5 s -1 mM -1 Fe) relaxivity. The biocompatible composites possess a large BET surface area (222.3 m 2/g), demonstrating that they can be used as a bifunctional agent for both MRI and drug carrier. Because of the high substrate loading of the magnetic, dual-porous materials, only a low dosage of the substrate will be acquired for potential practical applications. Hydrophobic zinc(II) phthalocyanine (ZnPC) photosensitizing molecules have been encapsulated into the dual-porous microspheres to form γ-Fe 2O 3@meso-SiO 2-ZnPC microspheres. Biosafety, cellular uptake in HT29 cells, and in vitro MRI of these nanoparticles have been demonstrated. Photocytotoxicity (λ > 610 nm) of the HT29 cells uptaken with γ-Fe 2O 3@meso-SiO 2-ZnPC microspheres has been demonstrated for 20 min illumination. © 2012 American Chemical Society.

Vreshch V.,CNRS Chemistry Institute of Rennes | Shen W.,CNRS Chemistry Institute of Rennes | Nohra B.,CNRS Chemistry Institute of Rennes | Yip S.-K.,Institute of Molecular Functional Materials | And 5 more authors.
Chemistry - A European Journal | Year: 2012

Treatment of U-shaped, binuclear Cu I complexes 1,1′ (1, counterion: BF 4 -; 1′, counterion: PF 6 -) with metal cyanide linear linkers K[Au(CN) 2] (3) and Hg(CN) 2 (4) lead to formation of new supramolecular assemblies 5,5′ and 6,6′, respectively, in good yield. These derivatives have been characterized by NMR spectroscopy, IR, and X-ray diffraction studies. Derivative 5,5′ are supramolecular metallacycles in which intramolecular aurophilic interactions between the Au I metal centers of the linkers are observed. Derivative 5 crystallizes as a single solid phase, whereas derivative 5′ is characterized in the solid state as four different pseudo-polymorphs (5′a-d). Notably in the case of phase 5′d, a dimer of supramolecular metallacycles bounded by intermolecular aurophilic interactions is formed. Conversely, derivatives 6,6′ present large structural diversity depending on the nature of the counterion. Derivative 6 is a supramolecular rectangle in which the Hg II-Hg II metal distance suggests mercurophilic interaction, whereas 6′ crystallizes as two different pseudo-polymorphs 6′a,b, that is, a one-dimensional coordination polymer and one oligomer with no short Hg II-Hg II metal contacts, respectively. In derivatives 6,6′, short contacts between the Hg II metal centers and fluorine atoms of the counterions are also observed, which may explain the counterion structural dependence of these supramolecular assemblies based on Hg II metal cyanide linker. Comparison of the different solid-state structures characterized highlights the importance of weak secondary interactions between the linkers for the formation supramolecular metallacycles from molecular clips 1,1′ and suggests the range of energies required for these interactions to form metallacycles and to induce self-aggregation. Aurophilicity versus mercurophilicity: The impact of d 10-d 10 metallophilic interactions on the structure of metal-rich supramolecular assemblies has been examined by treating U-shaped binuclear Cu I complexes with linear metal cyanide linkers (metal=Au I, Hg II; see figure). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li C.H.,Institute of Molecular Functional Materials | Ng A.M.C.,University of Hong Kong | Mak C.S.K.,Institute of Molecular Functional Materials | Djurisic A.B.,University of Hong Kong | Chan W.K.,Institute of Molecular Functional Materials
ACS Applied Materials and Interfaces | Year: 2012

We report the synthesis of a multifunctional block copolymer incorporated with pyrene and ruthenium terpyridyl thiocyanato complex moieties by reversible addition-fragmentation chain transfer polymerization. The pyrene block in the copolymer facilitates the dispersion of multiwalled carbon nanotubes in DMF solution because of the strong π-π interaction between the pyrene moieties and nanotube surface. On the other hand, the ruthenium complexes greatly enhance the photosensitivity of the functionalized nanotubes in the visible region. The photocurrent responses of the nanotubes at different wavelength measured by conductive AFM spectrum strongly agree with the absorption spectrum of the ruthenium complex. The results demonstrate a new and versatile approach in enhancing and fine-tuning the photosensitivity or other opto-electronic properties of carbon nanotubes by multifunctional block copolymers. © 2011 American Chemical Society.

Xia H.,Chinese University of Hong Kong | Liu D.,Chinese University of Hong Kong | Xu X.,Chinese University of Hong Kong | Miao Q.,Chinese University of Hong Kong | Miao Q.,Institute of Molecular Functional Materials
Chemical Communications | Year: 2013

Reported here are a new group of cyclopent[hi]aceanthrylene derivatives, which have a cyclopentadiene moiety to accept electrons and thus function as ambipolar organic semiconductors in thin film transistors. © 2013 The Royal Society of Chemistry.

Loading Institute of Molecular Functional Materials collaborators
Loading Institute of Molecular Functional Materials collaborators