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Self-Assembly of Europium-Containing Polyoxometalates/Tetra- <i>n</i> -alkyl Ammonium with Enhanced Emission for Cu <sup>2+</sup> Detection
摘要： Lanthanide-containing polyoxometalates (POMs) can be used to detect various materials, but their luminescence in water has suffered enormous limitations due to the strong fluorescence quenching. Herein, to resolve this problem, three-dimensional nanoparticles built by mixed Weakley-type europium-containing POMs (Na9[EuW10O36]·32H2O, abbreviated to EuW10) and tetra-n-alkyl ammonium (TA) with enhanced fluorescent properties have been designed in aqueous solution using an ionic self-assembly (ISA) technique, which is mainly driven by the electrostatic interaction between EuW10 and TA. The morphology and fluorescent properties of the system as well as some influencing factors (alkyl chain length, amino group, and inorganic salt concentration) were systematically investigated. The results indicated that the fluorescent intensity of EuW10/tetramethylammonium bromide (TMAB) composite increased about 14 times, whereas the extent of increase of fluorescence for EuW10/tetraethylammonium bromide (TEAB) and EuW10/tetrabutylammonium bromide (TMAB) composites gradually decrease due to the bulkier steric hindrance of the longer alkyl chain. Besides, the luminescence of EuW10/TMAB nanoparticles is pH responsive, and the reversibility of their structures and luminescence can be realized upon the addition of NaOH/HCl. Moreover, the EuW10/TMAB system also shows great fluorescence-sensing behavior, which could detect Cu2+ with a detection limit of 0.15 μM. Our work provides a facile construction strategy for a functional fluorescent complex via POMs-based supramolecular self-assembly in aqueous solution, which will be further used in biomarkers and sensors.
关键词： Cu2+ detection,fluorescence enhancement,ionic self-assembly,lanthanide-containing polyoxometalates,pH-responsive
更新于2025-09-23 15:21:01
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Ionic Self-Assembled Luminescent Nanospheres from Cationic Polyelectrolyte and Eu-Containing Polyoxometalate
摘要： Using the ionic self-assembly (ISA) strategy to combine Eu-containing polyoxometalates (Eu-POMs) and organic molecules mainly through noncovalent electrostatic interactions can protect Eu-POMs from solvent quenching of luminescence and enhance their processability. For this reason, a cationic polyelectrolyte, branched polyethyleneimine (PEI), and a Eu-POM, Na9(EuW10O36)·32H2O (EuW10), were used here to construct luminescence-enhanced spherical aggregates with diameters ranging from 50 to 200 nm. At a fixed concentration of EuW10, the phase behavior and luminescence properties of the mixture could be modulated by the PEI concentration. Such ISA-induced aggregates could effectively shield water molecules and result in better photophysical properties. Compared to bare EuW10, the absolute quantum yield and lifetime of luminescence for aggregates increased 10 and 5 times, respectively. Meanwhile, the sensitivity of the EuW10 coordination structure to the environment made it possible for obtained aggregates being used to detect either copper cations or permanganate anions due to their strong specific quenching effects to luminescence. Such a new type of luminescent soft material not only provided a reference for exploring the luminescence enhancement mechanism of lanthanide through self-assembly in aqueous solution but also exhibited potential in detection by luminescence analysis.
关键词： polyoxometalates,permanganate detection,polyethyleneimine,ionic self-assembly,copper detection,luminescence enhancement,luminescent nanospheres
更新于2025-09-23 15:19:57
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The construction and modulation of photoelectric functional hierarchical materials based on ionic self-assembly
摘要： The photoelectric functional hierarchical materials have been successfully prepared by the simple ionic self-assembly (ISA) strategy from the cationic ferrocenyl surfactant, 16-alkyl (ferrocenyl-methyl)ammonium bromide (Fc16AB) and the anionic alizarin red (AR). The obtained complexes exhibited multiple stimuli-responsive switching behaviour triggered by β-cyclodextrin (β-CD) inclusion, redox species, and pH. The switching mechanism corresponding to each stimulus was studied in detail. Moreover, the fluorescent intensity of binary complexes could be modulated by the concentration of Fc16AB and redox of ferrocene part. The fluorescence switching mechanism upon redox stimulus was studied in detail. Both the complexes fabrication and transition mechanisms were found to be controlled by the inclusion equilibrium and the cooperative binding of non-covalent interactions, including the electrostatic interactions, π-π stacking, and amphiphilic hydrophobic association. This work provides a deep understanding of electro-photo molecular switching device.
关键词： Hierarchical materials,pH,Redox species,Stimuli-responsive,β-Cyclodextrin (β-CD) inclusion,Ionic self-assembly
更新于2025-09-19 17:15:36
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A liquid crystal based method for detection of urease activity and heavy metal ions by using stimulus-responsive surfactant-encapsulated phosphotungstate clusters
摘要： A liquid crystal (LC) based method is described for the sensitive determination of the activity of urease and of heavy metal ions which acts as inhibitors. Stimulus-responsive surfactant-encapsulated phosphotungstate clusters (SECs) were fabricated and deposited onto octadecyltrichlorosilane-coated glass. A copper TEM grid filled with LCs was placed on the substrate to construct the LC optical cell. Upon addition of water to the LC interface, the optical appearance of LCs on the glass undergoes a bright-to-dark shift due to an orientational transition of the LCs from a planar to a homeotropic state. However, the LCs display a bright appearance if they are pretreated with an aqueous solution containing urea and urease. This is caused by the disassemby of the SECs from the glass surface due to an increase of the pH value that is induced by the enzymatic hydrolysis of urea by urease. The method is highly sensitive and can detect urease activities as low as 0.03 mU/mL. It can also be applied to the determination of heavy metal ions which exert an inhibitory effect on the activity of urease. For example, Cu(II) can be quantified via urease inhibition in 1 nM concentration.
关键词： Ionic liquid,Stimulus-responsive material,Surfactant,Sensor layer,Polyoxometalates,Urease,Nanocomposites,Ionic self-assembly,Liquid crystal
更新于2025-09-04 15:30:14