Self-Assembly of Europium-Containing Polyoxometalates/Tetra-n-alkyl Ammonium with Enhanced Emission for Cu²⁺ Detection

Abstract

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 (Na 9 [EuW 10 O 36 ]·32H 2 O, abbreviated to EuW 10 ) 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 EuW 10 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 EuW 10 /tetramethylammonium bromide (TMAB) composite increased about 14 times, whereas the extent of increase of fluorescence for EuW 10 /tetraethylammonium bromide (TEAB) and EuW 10 /tetrabutylammonium bromide (TMAB) composites gradually decrease due to the bulkier steric hindrance of the longer alkyl chain. Besides, the luminescence of EuW 10 /TMAB nanoparticles is pH responsive, and the reversibility of their structures and luminescence can be realized upon the addition of NaOH/HCl. Moreover, the EuW 10 /TMAB system also shows great fluorescence-sensing behavior, which could detect Cu 2+ 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.

Synthesis of a New Amino-Furopyridine-Based Compound as a Novel Fluorescent pH Sensor in Aqueous Solution

“…Development of small fluorescent molecules, − especially pH-sensitive fluorescent dyes, has gained substantial attention owing to their promising applications in various fields, including analytical chemistry, , biomedicinal research, − clinical diagnostics, − biology, − and environmental science . They are used as strainers, biomolecular labels, , environmental indicators, etc.…”

Novel Gemini Surfactant for Binding Eu(III)-Polyoxometalate into Hydrogels and Polymer Latexes

“…Thus, the 5 D 0 → 7 F 2 transition (I 2(to F2) ), an electric dipole transition frequently called hypersensitive transition, is extremely sensitive to the small changes in the environment surrounding Eu 3+ [ 34 , 36 , 37 ], while the 5 D 0 → 7 F 1 transition (I 1(to F1) ) is a magnetic dipole transition whose intensity is quasi-independent of the vicinity of Eu 3+ , being an internal standard of this kinds of Eu 3+ -based compounds [ 35 , 36 , 37 ]. By taking into account all these features, the value of intensity ratio I 1(to F1) /I 2(to F2) is used as a measure of symmetry/asymmetry of the Eu 3+ site in different surrounding microenvironments [ 34 , 35 , 36 , 37 , 38 ]. As a general rule, an increase in this ratio value is associated with an increase in Eu 3+ symmetry and vice versa [ 36 ].…”

Lanthanide-Containing Polyoxometalate Crystallized with Bolaamphiphile Surfactants as Inorganic–Organic Hybrid Phosphors

“…The as-prepared precipitate of C8N2-EuW10 was obtained in 15-20% yield, and the as-prepared precipitate of C10N2-EuW10 was obtained in 40-50% yield. In each case, single crystals were successfully isolated from the synthetic filtrate after the removal of the Cationic surfactants and polymer matrices as well as neutral block copolymers are effectively hybridized with the EuW 10 anion to obtain luminescent nanocomposites [26][27][28][29], thin films [30][31][32][33][34][35][36][37], and sensors [38][39][40][41]. These systems are functional as soft matter and compatible with living organisms.…”

“…The intramolecular energy transfer from the LMCT state of W5O18 6− ligands to the 5 D0 state of Eu 3+ causes distinct orange-red light emission. Cationic surfactants and polymer matrices as well as neutral block copolymers are effectively hybridized with the EuW10 anion to obtain luminescent nanocomposites [26][27][28][29], thin films [30][31][32][33][34][35][36][37], and sensors [38][39][40][41]. These systems are functional as soft matter and compatible with living organisms.…”