Shanyi Guang

Facile fabrication of three-dimensional highly ordered structural polyaniline–graphene bulk hybrid materials for high performance supercapacitor electrodes

A novel approach to constructing three-dimensional (3D) highly ordered structural polyaniline–graphene bulk hybrid materials was proposed for high performance supercapacitor electrodes, in which a functional molecule, sulfonated triazine (ST), was introduced and adsorbed on graphene sheets via hydrogen bonding and π–π stacking interactions. The aim of adding ST is to achieve better dispersion of graphene nanosheets in water, and subsequently induce heterogeneous nucleation of polyaniline (PANI) through electrostatic interactions. Thus, the PANI nanorods were impelled to grow vertically on both surfaces of the individual sulfonated triazine functional graphene nanosheets (STGNS) via in situ chemical oxidative polymerization of aniline in aqueous solution. The formation mechanism of well-controlled PANI nanorod array–sulfonated triazine functional graphene nanosheet (PANI–STGNS) hybrid materials was investigated in detail using a combination of UV–vis, FTIR, Raman spectroscopy and XRD. The optimized PANI–STGNS10 bulk hybrid material possesses a specific capacitance as high as 1225 F g−1 at 1 A g−1, together with outstanding rate capability and cycling stability, which are essential for its application in high performance supercapacitor electrodes.

Thermally stable oxadiazole-containing polyacetylenes: Relationship between molecular structure and nonlinear optical properties

Two novel high molecular weight functional polyacetylenes bearing oxadiazole groups as pendants, poly(2-(4-decyloxyphenyl)-5-(4-ethynylphenyl)-1, 3, 4-oxadiazole) (P1) and poly(2-(4-butyloxyphenyl)-5-(4-ethynylphenyl)-1, 3, 4-oxadiazole) (P2) were designed and synthesized by a multistep reaction route. The structures and properties were characterized and evaluated with FTIR, NMR, UV, TGA, GPC, optical-limiting (OL) and nonlinear optical (NLO) analyses. The incorporation of oxadiazole into polyacetylene significantly endows polyacetylenes with higher thermal stability and optical limiting property. The solubility, stereoregularity and optical properties of resultant polyacetylenes are obviously affected by flexible terminal alkoxy chain length. The cis olefinic structure content in polyacetylene backbone increases with increasing terminal alkoxy group length. The functional polyacetylene with the higher cis olefinic structure content shows higher thermal stability, better optical limiting property and larger third-order nonlinear optical performance. The optical limiting mechanism of resulting polymers was investigated, which is mainly originated from larger excitation state absorption cross-section of molecules to result in reverse saturable absorption.

Supramolecular self-assembly structures and properties of zwitterionic squaraine molecules

To further investigate the influence of H-bond combining with π–π stack interaction on the optical performances, a few rigid zwitterionic squaraine molecules, with different terminal H-bond recognition abilities, are identified and designed. They can controllably construct a series of supramolecular self-assemblies with different morphologies and dimensions via a simple solution-based self-assembly method under mild conditions. The morphologies, synergetic reinforcing effect, and optical-thermal properties are investigated and confirmed by both theoretical and experimental methods. The results indicate that the morphologies of the resultant self-assemblies can be effectively controlled by rational molecular design, whose absorption and emission spectra and thermal stabilities accordingly change with the alteration of zwitterionic squaraine molecular structures.

A modified fluorescein derivative with improved water-solubility for turn-on fluorescent determination of Hg2+ in aqueous and living cells

To improve the water-solubility of heavy-metal sensing materials, a modified fluorescein-based derivative, acryloyl fluorescein hydrazine (ACFH), was designed and developed by incorporating a non-hydrogen-bonding group into the conjugated molecule for weakening intermolecular hydrogen-bonding interactions. In neutral water environments, ACFH presented a fluorescence-enhancement performance at λmax=512nm in the presence of Hg2+, which could be visualized by naked-eyes. Under the optimized conditions, the linear range of Hg2+ detection was 1.0-100×10-9molL-1 with a correlation coefficient of 0.9992 and a detection limit of 0.86×10-9molL-1. The recognition mechanism was confirmed to be a stable and irreversible 1:1 five-member ring complex between ACFH and Hg2+ with a coordination constant of 3.36×109. ACFH would possess a potential application in detecting Hg2+ for biological assay with low cytotoxicity.

Preparation and properties of electron injecting molecular hybrid materials with high thermal performance

A series of oxadiazole-containing molecular hybrid materials with different structures (H1–H5) are controllably prepared by a hydrosilylation method based on the octahydridosilsesquioxane (POSS, T88HH). All these resultant hybrid materials are soluble in common organic solvents, such as chloroform, toluene, tetrahydrofuran, and 1,2-dichloroethane, and possess good film-forming properties. Their structure and properties are characterized and evaluated by FTIR, 1H NMR, 29Si NMR, GPC, TGA, DSC, UV-vis, PL, CV, and elemental analysis, respectively. It is found that the hydrosilylation reaction almost proceeds quantitatively when the feed ratio (molar number of organic monomer to molar number of POSS) is less than 4, at which the resultant hybrids can be controllably prepared by varying the feed ratio. These hybrids possess high thermal stability and good electron injecting properties and an intense blue emission was observed in these hybrids. Simultaneously, it is found that the hybrids (H3–H5) with a strong π electron conjugation effect between POSS and the oxadiazole moiety show higher thermal stability, better electron injecting properties and more intense blue emission than those (H1 and H2) without a π electron conjugation effect between POSS and the oxadiazole moiety.

Preparation and properties of a functional polyacetylene with quinoline-based heterocyclic azo pendants

A novel functional polyacetylene with D-π-A conjugated quinoline-based heterocyclic azo pendants was designed and prepared to improve the polyacetylene properties. Its structure and properties were characterized and evaluated in details. The incorporation of D-π-A conjugated quinoline-based heterocyclic azo pendants to the polyacetylene backbone increases the polymer solubility in polar solvents. Its UV-vis absorbance is sensitive to the presence of F− anions and results in UV-VIS spectrum red-shift by ca. 21 nm from 449 nm to 470 nm in dry DMSO.

Controlling the morphology and property of carbon fiber/polyaniline composites for supercapacitor electrode materials by surface functionalization

The effect of surface functionalization of carbon materials on the morphology and performance of carbon/polymer composite materials for supercapacitor electrodes was investigated here. Three kinds of functionalized carbon fibers were prepared by the simple chemical modification of carbon fiber, named oxidated carbon fiber (OCF), amino-functionalized carbon fiber (AFCF) and aminated triazine functionalized carbon fiber (ATFCF). Then functionalized carbon fibers were used to fabricate nanostructural polyaniline/CFs composites (PANI/OCF, PANI/AFCF, PANI/ATFCF) by electrochemical in situ polymerization under pulse current. The chemical compositions and morphologies of these PANI/CFs composites were studied by FTIR, Raman spectra and SEM. It was found that PANI on OCF composites displayed a disordered nanofiber structure owing to the non-covalent connection between PANI with OCF. Conversely, PANI grew on the surface of AFCF and ATFCF in an ordered fashion due to chemically covalent connection, exhibiting nanowire arrays and petal-like nanosheets, respectively. It hints that the morphology of PANI/CFs composites can be effectively adjusted by molecular structural design of functional groups on the functionalized CF. The electrochemical properties of these PANI/CF composites were evaluated by an electrochemical workstation. In comparison with noncovalent PANI/OCF composites, the strong covalent interactions together with the ordered nanostructures of PANI/AFCF and PANI/ATFCF facilitated faster charge transfer, smaller internal resistance and better mechanical properties, resulting in improved electrochemical performance.

Controllable preparation and properties of active functional hybrid materials with different chromophores

A convenient and efficient strategy for preparing active functional hybrid materials was proposed based on an investigation of the controllable preparation of a series of anthracene-containing organic–inorganic functional hybrid materials with active ethylene groups. These functional hybrid materials with different active vinyls were controllably prepared through a Heck reaction with octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) as the raw material by adjusting the feed ratio. Their structures and properties were characterized and evaluated by various measurements. The influence of molecular structure on the optical properties of the resulting hybrids was investigated in detail. It was found that the incorporation of nano-sized inorganic polyhedral oligomeric silsesquioxane (POSS) can efficiently prevent aggregation of hybrid molecules owing to the prohibition of π–π stacking between chromophore groups, which was also confirmed by theoretical simulation. Simultaneously, thermogravimetric analysis (TGA) results also show that the inorganic POSS causes the good thermal stabilities of the hybrids.

Facile preparation and properties of multifunctional polyacetylene via highly efficient click chemistry

A series of novel multifunctional polyacetylenes bearing oxadiazole and azo groups as molecular pendants were designed and synthesized via highly effective click chemistry. The resultant polymers showed good solubility in common organic solvents. The structure and properties of the resulting polymer were characterized and evaluated by FT-IR, 1H-NMR, UV-vis, TGA and FL analyses. The results show that the thermal stability of the synthesized functional polyacetylene was significantly increased when compared to single polyacetylene due to the jacket effect between the functional groups and backbone. The influence mechanism of the oxadiazole and azo groups was also discussed in detail. Simultaneously, the optical properties of the functional polyacetylene were investigated. It was found that the optical properties of the resulting polyacetylene were affected by the oxadiazole and azo groups. For P5–P7, the intensity of the absorption peak at ca. 452 nm, belonging to the azo group, decreased gradually as the content of M1 was reduced. In contrast, the intensity of the absorption peak at ca. 312 nm, belonging to the oxadiazole group, increased as the content of M2 increased. Due to azo group isomerization under the photo-thermal conditions, quenching of the fluorescence occurred in the range of molecules for M1, P2 and P3.

A generic and effective strategy for highly effective “intrinsic” molecular luminescence in the condensed state

A generic and efficient strategy to realize a high effective “intrinsic” single molecular luminescence in the condensed state was proposed by theoretical simulation at the macrostructure level at first, and then was confirmed by molecular design and preparation of a dumbbell-type (H2) and tadpole-type (H1) polyhedral oligomeric silsesquioxane (POSS) based hybrid. The enhancement mechanism of the optical properties was investigated in theory and with experiments. It was found that the incorporation of a “huge” inorganic POSS core on the nanoscale into the organic light-emitting molecules to form three-dimensional (3D) organic–inorganic hybrids effectively improved the optical properties in the condensed matter by decreasing the intermolecular dipole–dipole and π–π stacking interactions owing to the hindrance of the intermolecular charge-transfer between adjacent organic molecules. The dumbbell-type hybrid (H2) showed a better enhancement effect of the optical properties than the resultant tadpole-type hybrid (H1) owing to the crisscross-type arrangement of its dimer induced by the incorporation of POSS. Simultaneously, the two hybrids exhibited high thermal stability and good film forming ability.