ABSTRACT
Luminescent supramolecular metallacycles have attracted great interest as a new promising class of sensing substrates. In this work, two tetraphenylethene (TPE)-based diimidazole and dipyrazole ligands with the aggregation-induced emission (AIE) feature were designed for the construction of supramolecular tetragonal metallacycles 1-4 with two 90° mononuclear [(bpy)M]2+ or dinuclear [(bpy)2M2]4+ acceptors (bpy = 2,2'-dipyridine; M = Pd, Pt), in which the fluorescence can be quenched to an "off" state due to the ligand-to-metal charge transfer (LMCT). Metallacycle 1 was utilized as a fluorescence sensor for phosphate (PO43-) detection in aqueous solution by means of disassembly, leading to the release of the ligand. Additionally, the metallacycle can be regenerated through self-assembly via the introduction of Pd(II) acceptors. PO43- was detected using TPE-based metallacycles over a wide concentration range, with a detection limit as low as 2.1 × 10-8 M. Furthermore, sensor 1 also presented the semiquantitative visual detection ability for PO43- in the test paper mode via fluorescence changes. The aforementioned studies not only enhance the current research on fluorescent materials but also offer a strategy for the creation of stimuli-responsive supramolecular coordination complexes.
ABSTRACT
In this study, three-dimensional (3D) networked porous polyvinyl alcohol/sodium alginate/graphene oxide (PVA/SA/GO) spherical composites were fabricated by the sol-gel method and employed as adsorbents for the adsorption of methylene blue (MB) in aqueous solution. The obtained samples were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal property analysis, and nitrogen adsorption/desorption isotherms. Moreover, the adsorption properties for MB were investigated by batch experiments. The pseudo-first-order and pseudo-second-order equations were used to fit the adsorption kinetics data, and the Langmuir and Freundlich isothermal models were used to analyze the adsorption isothermals. The results showed that the spherical composites had 3D porous structures, and GO, PVA and SA were fused and linked together by self-assembly, physical intertwining, hydrogen bonding, and Ca2+ and boric acid crosslinking. The maximum adsorption capacity of the 3D porous PVA/SA/GO spherical composites for MB was 759.3 mg/g. The adsorption kinetics had a better agreement with the pseudo-secondorder equation than the pseudo-first-order equation, and the equilibrium data followed the Freundlich model.
ABSTRACT
In this paper, using maleic anhydride and ethylenediamine as functional monomers, graphene oxide (GO) loaded magnetic Fe3O4 nanoparticles modified by (3-Aminopropyl) triethoxysilane as support, magnetic graphene oxide grafted polymaleicamide dendrimer (GO/Fe3O4-g-PMAAM) nanohybrids were fabricated by divergent method and magnetic separation technology. The obtained samples were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, elementary analyzer and vibrating sample magnetometer. The effects of PMAAM generations, solution pH, Pb(II) initial concentration, temperature and contact time on the adsorption property of the samples for Pb(II) in aqueous solution were studied. The results demonstrated that nitrogen content and adsorption capacity of the as-synthesized samples with amino terminal groups were all higher than their adjacent generations PMAAM with carboxyl terminal groups. Moreover, with increasing generations of PMAAM grafted on to the GO/Fe3O4, the nitrogen content and the adsorption capacity of the samples with the same terminal groups gradually increased. The maximum adsorption capacity of GO/Fe3O4-g-G3.0 for Pb(II) was 181.4mgg-1 at 298K. The rising of temperature was beneficial for the adsorption. The adsorption kinetics had a better agreement with pseudo-second-order equation, and equilibrium data followed the Langmuir model.
