Congxin Xia

pH-Responsive Nanovesicles with Enhanced Emission Co-Assembled by Ag(I) Nanoclusters and Polyethyleneimine as a Superior Sensor for Al3+

Metal nanoclusters (NCs) have been engineered as a new kind of luminescent material, whereas the application of metal NCs in aqueous solution was subjected to great limitations owing to their poor solubility, stability, and strong luminescence quenching in a single-molecule state. Herein, facile supramolecular self-assembly strategy was carried out to enhance the luminescence of Ag(I) NCs (Ag6-NCs) through multiple electrostatic interactions with polyethyleneimine (PEI). Functional colloid aggregates of Ag6-NCs such as nanospheres and nanovesicles were formed along with the enhanced emission because of the formation of compact-ordered self-assemblies, which effectively restricted intramolecular vibration of the capping ligands on Ag6-NCs to diminish the nonradiative decay. All those could block energy loss and facilitated the radiative relaxation of excited states which ultimately induced an aggregation-induced emission (AIE) phenomenon. Furthermore, the luminescent Ag6-NCs/PEI nanovesicles are pH-responsive and show a superior fluorescent sensing behavior for the detection of Al3+ with a limit of detection low to 3 μM. This is the first report about AIE of silver NCs with polymers in aqueous solution. This work sheds light on the controlled NCs-based supramolecular self-assembly and the NCs-based functional materials, which will be well-established candidates in controllable drug delivery, biomarkers, and sensors in aqueous solution.

Self-assembly of biosurfactant–inorganic hybrid nanoflowers as efficient catalysts for degradation of cationic dyes

Three-dimensional (3D) hierarchical nanostructures have generated a large amount of interest because of their unique, unusual properties and potential applications. In this article, copper(II) ions as the inorganic component and various biosurfactants as the organic component were used to successfully form 3D nanoflowers via a facile and effective self-assembly template synthesis strategy. It can be confirmed that the biosurfactant molecules can first form complexes with the copper ions, and these complexes then become nucleation sites for primary crystals of copper phosphate, indicating that the interaction between biosurfactant and copper ions leads to the formation of 3D nanoflowers. Several reaction parameters such as aging time and the concentration of the biosurfactant, which play a critical role in the formation process and morphologies of the nanoflowers, were investigated. Under the optimum synthetic conditions, a spherical flowerlike structure with hundreds of nanopetals was obtained. Moreover, the biosurfactant–Cu3(PO4)2·3H2O nanoflowers also showed high stability and catalytic activity for degradation of cationic dyes. Our results demonstrate that the biosurfactant–inorganic 3D nanoflowers, which combined the advantages of the biosurfactant and inorganic material, have potential applications in industrial biocatalysis, biosensors, and environmental chemistry.

Coassembly of Mixed Weakley-Type Polyoxometalates to Novel Nanoflowers with Tunable Fluorescence for the Detection of Toluene

In this work, three-dimensional nanoflowers with tunable fluorescent properties constructed with mixed Weakley-type polyoxometalates (POMs, Na9[LnW10O36]·32H2O, Ln = Eu, Tb, abbreviated to LnW10) and tetraethylenepentamine (TEPA) have been successfully prepared through a facile ionic self-assembly (ISA) method. The shape and petal size of the nanoflower as well as its fluorescent behaviors can be tuned through varying the ratio of EuW10/TbW10. The varied-temperature emission behaviors at 80-260 K show that the fluorescent intensity of both Tb3+ and Eu3+ decreased with the increase in temperature, which makes them potential luminescent ratiometric thermometers. Moreover, after being mixed with polydimethylsiloxane (PDMS), the as-formed hybrid films showed stable fluorescence along with good transparency. The robustness of the hybrid films was also demonstrated by corrosion resistance upon treatment with strong acid and alkali and thus can be used as a sensor to detect toluene circularly. Our results provide a new avenue to the facile construction of fluorescent composites and demonstrate that the POM complexes can be further used in supramolecular chemistry and nanomaterials.

Self-Assembly of Peptide-Polyoxometalate Hybrid Sub-Micrometer Spheres for Photocatalytic Degradation of Methylene Blue

The spontaneous formation of hybrid submicrometer spheres that were composed by a Weakley-type polyoxometalate Na9[EuW10O36]·32H2O (denoted as EuW10) and cationic peptide (K8) through a simple ionic self-assembly method was investigated. The approach presented in this study is an extended research which combined a biomolecule and a functional inorganic polyoxoanion for the fabrication of a multifunctional material. The K8/EuW10 hybrid submicrometer spheres were fully characterized by transmission electron microscopy, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, confocal laser scanning microscopy, and fluorescence spectra. The results indicated that the electrostatic interaction, hydrogen-bonding interaction, and combined hydrophobic interaction between EuW10 and K8 favored the formation of the smooth submicrometer sphere structure. Once the EuW10/K8 submicrometer spheres were forming, the fluorescence of EuW10 was reduced due to the hydrogen bonding between the ammonium group of K8 and the oxygen atom of EuW10 that blocked the hopping of the d1 electron in EuW10. Interestingly, our submicrometer spheres showed excellent decomposition efficiency toward organic pollutants such as the dye of methylene blue (MB), suggesting their promising applications in the treatment of wastewater.