Hongyu Guo,Linfang Liang,Jiayi Guo,Liangbin Lin,Fafu Yang
The metal-coordination self-assemble system played an important role on constructing novel supramolecular smart-response materials. Although the single and double-response materials based on metal-induced self-assembly had been studied extensively, the triple responses for this kind of supramolecular material was seldom reported. In this work, the first metal-induced self-assemble system with triple responses on photophysical, liquid crystalline and gel properties was presented based on Hg 2+ -coordination tetraphenylene dimer ( Bis-TPE ). Bis-TPE was prepared by bridging two alkyl-substituted tetraphenylene with amido chain. It possessed the fluorescence response from the strong emission for Bis-TPE to the faint emission for Bis-TPE -Hg 2+ complex. The self-assemble mechanism of Bis-TPE -Hg 2+ was clarified as that Hg 2+ was located in the cavity of the amido-ether chain of Bis-TPE . The Hg 2+ -induced mesomorphic transition was also observed from smectic mesophase for Bis-TPE to hexagonal columnar mesophase for Bis-TPE -Hg 2+ complex. The unique Hg 2+ -induced gel transition was further distinguished from low-order spherical morphology for Bis-TPE to high-order fibrous morphology for Bis-TPE -Hg 2+ complex. The maximum fluorescence wavelength exhibited the giant shift from 494 nm for Bis-TPE in gel to 606 nm for Bis-TPE -Hg 2+ in gel. This kind of triple responses on photophysical, liquid crystalline and gel properties for metal-coordination self-assemble system was described for the first time, affording a new idea on design of new multiple-response materials with unique properties.
A citrate-assisted hydrothermal method was utilized for the preparation of Sr-substituted hydroxyapatite (HA) nanoparticles. The influences of Sr-substituting degree on the phase identifications, microstructures and colloidal stability of the resultant products were studied. The experimental results show that the crystalline structures and morphologies of final resultants are significantly changed by controlling the Sr-substituting degree. As the Sr-substituting degree increases, the colloidal stability of samples first increases and then decreases rapidly; the morphology of the product first changes from nanorods to short nanorods rod and then becomes nanowires. Uniform HA hexagonal nanorods with high aspect ratio (>4.0) and excellent aqueous colloidal stability were prepared by 6 h hydrothermal reaction at 180 °C without Sr substitution. The dispersion underwent the phase transition from isotropic to liquid-crystalline state upon the increasing concentration of 25wt% and the complete liquid-crystalline phase was achieved when at the concentration above 31wt%. These novel findings provide new insights into the role of Sr substitution on both the citrate-assisted hydroxyapatite crystallization and tailoring of colloidal stability. Moreover, HA liquid crystal behavior was successfully observed, which lays a foundation for the fabrication of macroscopically assembled hydroxyapatite-based biomimetic materials for biomedical applications.
MOF/polymer hybrid membranes integrate the surface activity of MOFs and the advantages of PVDF membranes, and can be used as adsorption membranes in the efficient removal of target organics. In this work, a new hybrid membrane of ZIF-67/PVDF with varying ZIF-67 dosages has been fabricated through a facile mechanical blending followed by a lyotropic phase transition. Methods including field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), FT-IR analyses and surface hydrophobicity/hydrophilicity measurements are applied to characterize the structure, physicochemical properties and membrane performances. Two synthetic triarylmethane dyes, cationic malachite green (MG) and anionic fuchsin acid (FA), are chosen as the main adsorption targets to evaluate the adsorption capacities of the resulting ZIF-67/PVDF hybrid membranes. Interestingly, all of the ZIF-67/PVDF hybrid membranes exhibit distinctly favorable efficiencies and selectivities toward MG and FA compared to pristine PVDF, which proves the positive roles of ZIF-67 in the adsorption ability of the hybrid membranes. The adsorption conditions are optimized and the adsorption kinetics and thermodynamics are analysed to study the adsorption mechanism. The reusability and the structural stability of the hybrid membranes undergoing cyclic adsorption processes are also discussed. To the best of our knowledge, this is the first time that good adsorption capacities for MG and FA for these MOF/PVDF membranes have been reported. This work highlights the prospective applications of MOF/PVDF hybrid membranes in the rapid and effective removal of target organics in the treatment of waste water.
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