Aiqing Zhang

A highly sensitive sensor based on hollow particles for the detection, adsorption and removal of Hg2+ ions

A simple and facile method has been developed for the preparation of highly sensitive hollow spheric chemosensors. In this method, positively charged polystyrene (PS) particles were employed as templates to prepare silica hollow microspheres, and then the micro-sensors were grafted onto the hollow spheres to obtain hollow-chemosensors. A series of different SiO2 hollow spheres could be prepared by tuning the preparation conditions, and were used to carry the sensors. The hollow-chemosensors could not only detect Hg2+ ions, but were also able to separate them with high efficiency. When the hollow-chemosensors were added to Hg2+ ion solutions, the color of solution instantly changed from red to yellow and could be seen by naked eye. The adsorption capacity did not vary significantly over a wide pH range from 3 to 8. The hollow-chemosensors exhibited high selectivity for the detection of Hg2+ ions over other heavy metal ions. In addition, the superiority of using hollow silica spheres as carriers, which was promising for chemosensor detection, adsorption and removal of heavy metal ions in solution, could be clearly seen.

A rational construction of microporous imide-bridged covalent–organic polytriazines for high-enthalpy small gas absorption

A series of microporous imide functionalized 1,3,5-triazine frameworks (named TPIs@IC) were designed by an easy-construction technology other than the known imidization method for the construction of porous triazine-based polyimide networks (TPIs) with the same chemical compositions. In contrast to TPIs, TPIs@IC exhibit much higher Brunauer–Emmett–Teller (BET) surface areas (up to 1053 m2 g−1) and carbon dioxide uptake (up to 3.2 mmol g−1/14.2 wt% at 273 K/1 bar). The presence of abundant ultramicropores at 5.4–6.8 A, mainly ascribed to a high-level cyano cross-linking, allows the high heat absorption and high selective capture of CO2. The Qst (CO2 esoteric enthalpies) from their CO2 adsorption isotherms at 273 and 298 K are calculated to be in the range 46.1–49.3 kJ mol−1 at low CO2 loading, and the ideal CO2/N2 separation factors are up to 151, exceeding those of the most reported porous organic polymers to date. High storage capacities of TPIs@IC for other small gases like CH4 (5.01 wt% at 298 K/22 bar) and H2 (1.47 wt% at 77 K/1 bar) were also observed, making them promising adsorbents for gas adsorption and separation.

The effect of molecular weight of hyperbranched epoxy resins with a silicone skeleton on performance

Hyperbranched epoxy resins with a silicone skeleton (HERSS) obtained by us through an environmentally-friendly synthetic method have shown a prominent comprehensive performance in modifying the diglycidyl ether of bisphenol-A (DGEBA). However, controlling the performance of the HERSS is still a challenge. In this paper, we report the preparation of three other kinds of HERSS with various molecular weights via hydrosilylation, in order to study the effect of the molecular weights of the HERSS on the degree of branching (DB), the viscosity and the mechanical performance, the thermal properties and the micro-phase separation behavior of cured HERSS–DGEBA composites, which contain the HERSS prepared recently. The degree of branching and viscosities of the HERSS are 0.71–0.84 and 103.5–697.4 mPa s, respectively. An increase in the molecular weight of the HERSS results in a decrease in the DB and an appearance of a maximum viscosity. Accordingly, the mechanical properties of the cured HERSS–DGEBA composites, including the tensile, flexural and impact strength, increase first and then decrease, and their glass transition temperatures decrease weakly. Both the average diameters of 3.62–4.75 μm and the distribution of the islands in the “sea–island” structure of all the cured composites show an increase. Compared with those of DGEBA, the tensile, flexural and impact strength could be increased by about 76.4–88.6%, 25.3–36.0% and 78.4–92.1%, respectively, but their glass transition temperature was impaired only by about 6.3–6.8%.

High Performance Carbon Nanotube Yarn Supercapacitors with a Surface-Oxidized Copper Current Collector.

Threadlike linear supercapacitors have demonstrated high potential for constructing fabrics to power electronic textiles (eTextiles). To improve the cyclic electrochemical performance and to produce power fabrics large enough for practical applications, a current collector has been introduced into the linear supercapcitors to transport charges produced by active materials along the length of the supercapacitor with high efficiency. Here, we first screened six candidate metal filaments (Pt, Au, Ag, AuAg, PtCu, and Cu) as current collectors for carbon nanotube (CNT) yarn-based linear supercapacitors. Although all of the metal filaments significantly improved the electrochemical performance of the linear supercapacitor, two supercapacitors constructed from Cu and PtCu filaments, respectively, demonstrate far better electrochemical performance than the other four supercapacitors. Further investigation shows that the surfaces of the two Cu-containing filaments are oxidized by the surrounding polymer electrolyte in the electrode. While the unoxidized core of the Cu-containing filaments remains highly conductive and functions as a current collector, the resulting CuO on the surface is an electrochemically active material. The linear supercapacitor architecture incorporating dual active materials CNT + Cu extends the potential window from 1.0 to 1.4 V, leading to significant improvement to the energy density and power density.

Environment-friendly synthesis and performance of a novel hyperbranched epoxy resin with a silicone skeleton

Hyperbranched epoxy resins have attracted increasing attention for their excellent comprehensive performance in toughening and reinforcing the diglycidyl ether of bisphenol-A (DGEBA). However, the tedious synthetic procedure, high cost, and the use of large amounts of organic solvents have hampered their industrial application. This paper presents an environment-friendly method to synthesize a novel hyperbranched epoxy resin with a silicone skeleton (HERSS) through a hydrosilylation reaction catalyzed by a heterogeneous halloysite-supported platinum catalyst. The reaction involves only one solvent and affords a high yield (>90%). The chemical structure, molecular weight, and degree of branching of the HERSS were characterized by FT-IR, GPC and NMR. The resulting HERSS was used to modify a DGEBA based epoxy resin and showed excellent performance. With the incorporation of 9 wt% HERSS, the impact, flexural and tensile strength of DGEBA are increased by about 92.5%, 36.0% and 88.6%, respectively. The toughening and reinforcing mechanism was attributed to the “sea-island” structure of the cure composite, as shown by the SEM micrographs of the fractured surfaces. An initial thermal decomposition temperature of about 380.0 °C of the cured HERSS/methyl nadic anhydride resin also indicates promising applications with regard to high-temperature-resistance.

1D nano- and microbelts self-assembled from the organic-inorganic hybrid molecules: oxadiazole-containing cyclotriphosphazene.

A new oxadiazole-containing cyclotriphosphazene, namely, hexakis-(4-(5-phenyl-1,3,4-oxazodiazol-2-yl)-phenoxy)-cyclotriphosphazene (HPCP) was synthesized. Single-crystal nano- and microbelts of HPCP were self-assembly via two simple solution methods. The shapes of the as-prepared nano- and microstructures can be readily controlled by varying the solvent and aging time in the self-assembly process. A growth mechanism was proposed for the formation of the 1D morphological structures. Crystal structure analysis demonstrated that the overlap between the aryl units attached to the cyclotriphosphazene backbone forms effective intermolecular π-π linking for crystal growth. Electronic and optical properties of the as-prepared nano- and microstructures are investigated.

High performance two-ply carbon nanocomposite yarn supercapacitors enhanced with a platinum filament and in situ polymerized polyaniline nanowires

Two-ply yarn supercapacitors behave like conventional textile yarns to power next generation electronic textiles. To improve the capacitance of the yarn, we produced a metal filament reinforced carbon nanotube composite yarn which was further in situ polymerized with polyaniline nanowires for use as electrodes. The wearable two-ply yarn supercapacitor made from the composite electrodes possesses very high capacitance (91.67 mF cm−2) and energy density (12.68 μW h cm−2), and excellent long term cycling stability for charging-discharging and flexing deformation. The two-ply nanocomposite yarn supercapacitors have been connected in series and in parallel to power miniature electronic devices in smart textiles.

Photocrosslinking of sulfonated poly(arylene ether sulfone) in a swollen state

Novel photocrosslinkable sulfonated poly(arylene ether sulfone)s containing chalcone moieties in the polymer backbone (SPAEF) were synthesized from 4,4′-dihydroxychalcone (4DHC), 4,4′-difluoro-diphenylsulfone-3,3′-disulfonate (SDFDPS) and decafluorobiphenyl (DFBP). We introduced a new strategy to crosslink photosensitive polymer electrolyte membranes by UV irradiation in a swollen state in order to preserve the interconnected hydrophilic channels in the hydrated SPAEF electrolyte membrane. Photocrosslinked membranes showed desired effects of improved mechanical properties with significantly low methanol diffusion coefficient, while maintaining high proton conductivity. SPAEF membranes after the photocrosslinking exhibited a proton/methanol selectivity of 7.6 × 105 S s cm−3 at 30 °C, which is 21 times higher than that of Nafion® 117. This novel photocrosslinking strategy also improved oxidative and hydrolytic stabilities of polymer membranes which are desirable for direct methanol fuel cell application.

Chemical functionalization for improving dispersion and interfacial bonding of halloysite nanotubes in epoxy nanocomposites

The effects of chemical functionalization of halloysite nanotubes (HNTs) on dispersion, interfacial interaction, and mechanical properties of epoxy nanocomposites were investigated. HNT-filled epoxy nanocomposites were fabricated and their morphology and mechanical properties were systematically studied; the results were compared with those for neat epoxy resin. Transmission electron microscopic micrographs revealed uniform morphologic dispersion of functional HNTs in the epoxy matrix. The interfacial interaction between functional HNTs and the epoxy matrix was shown by differential scanning calorimetry and scanning electron microscopy analyses. The reaction between the functional amine--terminated groups of HNTs and epoxy monomers improved the dispersion of HNTs and the interfacial adhesion between HNTs and epoxies. The functional HNT-filled epoxy nanocomposites showed improved mechanical properties compared with the as-received HNT-filled nanocomposites. This was attributed to better dispersion and stronger interfacial interaction.

Synthesis and evaluation of a novel cationic konjac glucomannan-based flocculant.

A novel cationic flocculant of konjac glucomannan-graft-poly-(2-methacryloyloxyethyl)trimethyl ammonium chloride (KGM-g-PDMC), was successfully synthesized by using acidic ammonium cerium (IV) nitrate (CAN) as initiator in homogeneous aqueous solution. The graft copolymer was characterized using Fourier-transform infrared (FT-IR) spectroscopy, (1)H nuclear magnetic resonance ((1)H NMR), thermogravimetric analysis (TGA) and elemental analysis. The influences of degree of substitution (DS) of KGM, concentration of NaCl and pH value on turbidity removal rate of the cationic flocculant were investigated. The results demonstrated that the flocculant exhibited excellent flocculating ability in the presence of salt and a wide range of pH (1<pH<9). With DS of 0.2, the turbidity removal rate of flocculant to 0.1% kaolin suspension could reach more than 90% at pH 7.0. The flocculation mechanisms were investigated by screening effect and means of zeta potential. Holding the positive charge, the KGM-g-PDMC could efficiently remove the negatively charged contaminants such as kaolin suspension.