Antenna Effect on the Organic Spacer-Modified Eu-Doped Layered Gadolinium Hydroxide for the Detection of Vanadate Ions over a Wide pH Range

Layered Gadolinium-Europium-Terbium Hydroxides Sensitised with 4-Sulfobenzoate as All Solid-State Luminescent Thermometers

Ternary layered gadolinium-europium-terbium basic chlorides were synthesised using a facile hydrothermal-microwave technique. A continuous series of solid solutions was obtained in a full range of rare earth concentrations. To sensitise the luminescence of Eu3+ and Tb3+, a 4-sulfobenzoate anion was intercalated in the ternary layered rare earth hydroxides using one of two methods—a high-temperature ion exchange or a single-stage synthesis. The luminescent colour of the materials was governed by the gadolinium content: at low and medium gadolinium concentrations (0–70%), layered Gd-Eu-Tb basic sulfobenzoate exhibited a bright red europium luminescence; at high gadolinium content (70–90%), a bright green terbium luminescence was observed. The colour coordinates of layered Gd-Eu-Tb basic sulfobenzoate luminescence depended on the temperature in the physiological range (20–50 °C). The relative thermal sensitivity of the obtained materials was up to 2.9%·K−1.

Eu(III) Functionalized Crystalline Polyimide Hydrogel Film as a Multifunctional Platform for Consecutive Sensing of Spermine and Copper Ions

In this study, a novel Eu(III) functionalized crystalline polyimide hydrogel film (Eu-1) is fabricated by incorporating highly stable polyimide (PI) into a sodium alginate (SA) matrix, followed by cross-linking reaction with Eu³⁺ ions. Based on different fluorescence responses, Eu-1 is used for the consecutive detection of spermine (Spm) and copper ions (Cu²⁺). Eu-1 can be employed as a sensor for polyamine, especially for Spm with significant fluorescence enhancement based on the "turn on" mode. The fluorescent sensor Eu-1@Spm constructed by the Eu-1 and Spm can be further used as a "turn off" sensor to quantitatively monitor Cu²⁺. The good selectivity combined with the low detection limit of the sensor meets the requirements for monitoring Cu²⁺. The possible luminescence response mechanisms to Spm and Cu²⁺ have been studied through experimental data and theoretical calculations. In addition, a back-propagation neural network (BPNN) model based on an Eu-1@Spm sensor is constructed, which can accurately distinguish Cu²⁺ concentrations by deep machine learning (ML). This work not only puts forward a facile method to prepare a novel Eu-functionalized PI-based hybrid film but also demonstrates the potential of PI-based film materials for fluorescence detection.

Eroding the Surface of Rare Earth Microcrystals through Vanadate Ions for Considerable Improvement of Luminescence

Developing an efficient approach to improve the luminescence of the phosphors without heating processing is a challenge, but attracts much attention. In the present paper, prismatic microcrystals of RE4O(OH)9NO3 (RE = Y, Eu) were synthesized by a hydrothermal reaction at 180 °C for 24 h. The reaction with VO3− did not change the crystal structure of the microcrystals and VO3− substituting for NO3− anions did not take place. However, it contributed to the formation of amorphous particles containing VO3− on the surface of a prism, which is similar to the surface corrosion of a metal, called “surface eroding”. Therefore, surface modification was successfully achieved by eroding the surface of the microcrystals through the reaction with vanadate ions. As a result of VO3−→Eu3+ energy transfer and the light-harvesting ability of VO3−, the red emission intensity at 617 nm of the modified microcrystals greatly increased. Eroding the surface of rare earth microcrystals recommends a new paradigm for luminescence improvement of rare earth compounds.

Optical Properties of New Terbium(III) Ternary Complexes Containing Anionic 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione and Neutral Sensitizers in Solution, Solid and PMMA Thin Films: Intra and Interphase Colour Tuning

Four new terbium(III) ternary complexes, [Tb(fod)₃ (indazole)] (1), [Tb(fod)₃ (tptz)] (2), [Tb(fod)₃ (impy)] (3) and [Tb(fod)₃ (tppo)₂ ] (4) with 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, (Hfod) and N and O donors are synthesized and structurally characterized. The photoluminescence of the complexes are studied in solid, chloroform solution and thin PMMA hybrid films (PMMA is a poly(methyl methacrylate)). The ligand-based emission is dominant in solution of 3 and 4. The effect of ancillary ligands on the photoluminescence of terbium(III) ion is investigated. The mechanism of energy transfer is discussed and correlates the luminescence of acceptor terbium ion with the triplet state energy level of donor ligands. Among the four complexes studied, the luminescence from 1 is most intense followed by 2, 4 and 3. The Commission International de I'Eclairage (CIE) color coordinates of these complexes are calculated and presented. The complexes 3 and 4 show intraphase color tuning when excited under different UV wavelengths. The emission color of [Tb(fod)₃ (tppo)₂ ] (4) changes from pure blue to turquoise green via almost pure white under 360, 328 and 280 nm UV excitation wavelengths respectively. The [Tb(fod)₃ (impy)] (3) show similar results. The complex [Tb(fod)₃ (tptz)] (2) displays interphase color tuning from yellow (solution) to turquoise green (solid) and fascinatingly incorporation of complex in PMMA polymer generates white light under same excitation wavelength (360 nm).

Selective Sensing of Cu2+ and Fe3+ Ions with Vis-Excitation using Fluorescent Eu3+-Induced Aggregates of Polysaccharides (EIAP) in Mammalian Cells and Aqueous Systems

Fluorescent lanthanide complexes have favorable features for fluorescence-based sensors compared to organic fluorophores and quantum dots. They exhibit very long fluorescence lifetimes, sharp emission bands, and stability with respect to photo-bleaching, without blinking. However, these complexes are usually hydrophobic, and many are excited by UV light, making them hazardous and incompatible with aqueous environments and biological samples. In this work, the strong fluorescent Eu³⁺-induced aggregates of polysaccharides (EIAP) was used to improve their aqueous solubility, and to tune the appropriate excitation wavelength in the visible range for avoiding toxicity of UV light in biological applications. The complexes exhibit bright fluorescence with an excitation maximum in the visible range, near 405 nm. EIAP 3 also exhibit rapid quenching response in the presence of transition metal ions. This enables the detection of Cu²⁺ and Fe³⁺ below 1 ppm. The reverse of quenching response of copper by the addition of a chelating agent makes it possible to recover the fluorescence property. Successfully, the EIAP exhibit cytocompatibility with mammalian cells. Thus, these new polysaccharide-based complexes have the potential for rapid, sensitive and selective metal ion sensors for the environmental systems.

Regulation of the Metal Center and Coordinating Anion of Mononuclear Ln(III) Complexes to Promote an Efficient Luminescence Response to Various Organic Solvents

A series of mononuclear lanthanide complexes [Ln(L1)(NO₃)₃], (Ln = Dy(III), 1; Tb(III), 3; and Eu(III), 4; L1 = (N¹E,N²E)-N¹,N²-bis((1-methyl-1H-benzo[d]imidazol-2-yl)methylene)cyclohexane-1,2-diamine) is obtained by reacting N-methylbenzimidazole-2-carbaldehyde (L2) and 1,2-cyclohexanediamine (L3) with Ln(NO₃)₃·6H₂O under solvothermal conditions. L1 ligand is produced via an in situ Schiff base reaction of two molecules of L2 and one molecule of L3. The metal center Ln(III) is in a N₄O₆ environment formed by L1 and NO₃^-. NaSCN is added on the basis of 1 synthesis. One SCN^- replaces one of the three coordinated NO₃^- anions in the 1 structure, and the complex [Dy(L1)(NO₃)₂(SCN)]·CH₃CN (2) is synthesized. The complex 1 shows excellent luminescence response to petroleum ether (PET), an organic solvent. To the best of our knowledge, this study is the first to use a complex for sensing responses to PET. When the metal center is changed, the obtained mononuclear complexes 3 and 4 show an excellent luminescence response to tetrahydrofuran (THF). Lastly, 2 obtained by changing the coordinating anion shows an excellent luminescence response to dichloromethane. Herein, for the first time, we regulate the metal center and coordinating anion of lanthanide complexes to adjust the recognition and response of these complexes to different organic solvents.

Dual-Mode, Color-Tunable, Lanthanide-Doped Core-Shell Nanoarchitectures for Anti-Counterfeiting Inks and Latent Fingerprint Recognition

With the rapid development of information in modern society, the research and development of advanced anti-counterfeiting technology is becoming more and more important to protect the security and comprehensiveness of information. Therefore, fluorescent ink as an anti-counterfeiting technology and fingerprint recognition technology as a ″human information identification card″ has attracted the attention of many research groups. Herein, dual-mode (upconversion and downconversion) lanthanide-doped luminescent nanoarchitectures were developed using Y₂O₃:Er³⁺,Yb³⁺ nanoparticles as a core and layered lanthanide hydroxides nanomaterials as a shell. Under the irradiation of 980 nm near-infrared light, the nanoarchitectures emitted a bright upconverted red light emission. Meanwhile, under the irradiation of 254 nm UV light, the nanoarchitectures can directly emit multicolor luminescence (from green to yellow-green, yellow, orange, and red) by changing the suitable ratios of Tb³⁺/Eu³⁺ ions. The information can only be extracted when the irradiation of two kinds of excitation light sources existed at the same time, which can improve the difficulty of illegal imitation and enhance the level of anti-counterfeiting. Furthermore, these luminescent nanoarchitectures were investigated for visual latent fingerprint recognition on various substrates with high definition, high sensitivity, and high anti-interference. These results indicated that the nanoarchitectures reported in this study may have great application prospects in information security and identity recognition.

Luminescence Tuning of Layered Rare-Earth Hydroxides (LRHs, R = Tb, Y) Composites with 3-Hydroxy-2-naphthoic Acid and Application to the Fluorescent Detection of Al3

Tunable luminescence (quenching or blue shift) of HNA/OS-LRH composites (HNA is 3-hydroxy-2-naphthoic acid; OS is the anionic surfactant of 1-octanesulfonic acid sodium; LRHs are layered rare-earth hydroxides, R = Tb³⁺, Y³⁺) in the solid state and delaminated state is reported, which is utilized as an effective fluorescent probe for detecting metal ions. HNA/OS species are intercalated into LRH layers to generate composites of HNA _xOS_{1- x}-LTbH ( x = 0.10, 0.15, 0.20 , 0.25) and HNA _yOS_{1- y}-LYH ( y = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30). In the solid state, LYH composites exhibit green emissions (from 493 to 504 nm) with a large blue shift in comparison to the 542 nm emission of free HNA^- anions, while in the delaminated state in formamide (FM), the composites display blue emission (480 nm) relative to the green emission (512 nm) of an HNA soltuion in FM. However, LTbH composites display coquenched luminescence in both the solid state and delaminated state. Also, HNA_0.25OS_0.75-1:1-LYH, HNA_0.25OS_0.75-1:2-LYH, and HNA_0.05OS_0.95-1:1-LYH (1:1 and 1:2 are HNA:NaOH molar ratios) show significantly elongated fluorescence lifetimes of 15.35, 14.37, and 12.72 ns, respectively, in comparison with free HNA-Na (6.44 ns), and their quantum yields of 23.40%, 21.97%, and 22.31%, respectively, are much larger than that of free HNA-Na (4.86%). The LTbH composite (HNA_0.25OS_0.75-1:1-LTbH) has also a relatively higher quantum yield of 12.46%. The HNA_0.25OS_0.75-1:1-LYH colloid exhibits excellent recognition selectivity for Al³⁺ over other metal ions (Mg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, and Hg²⁺) with distinct fluorescence sensitization. It shows an intense change in its fluorescence emission when it is bound to Al³⁺ ions, giving a lower detection limit of 6.32 × 10^-6 M. This is novel research on the fluorescence chemosensing of LRH composites.

A self-calibrated luminescent thermometer based on nanodiamond-Eu/Tb hybrid materials

ND-PMA-RE was synthesized and the ND-PMA-Eu/Tb could be served as a self-referencing luminescent thermometer due to the temperature-dependent luminescence performance.

Eu-Doped layered yttrium hydroxides sensitized by a series of benzenedicarboxylate and sulphobenzoate anions

A series of new Eu-doped layered yttrium hydroxides intercalated with various organic dianions having similar molecular structure (dicarboxylates and sulphobenzoates) were synthesized.

Synthesis, characterization, photoluminescence and intensity parameters of high quantum efficiency pure-red emitting Eu(iii) fluorinated β-diketone complexes

The high quantum efficiency mononuclear 7-, 8- and 9-coordinate complexes of tris(heptafluoro-dimethyl-octanedionato)Eu(iii) and 1H-indazole, 2-(1H-imidazol-2-yl)pyridine and 2,4,6-tris(2-pyridyl)-s-triazine are synthesized and thoroughly characterized.

Synthesis, crystal structure and photoluminescence studies of [Eu(dbm)3(impy)] and its polymer-based hybrid film

An eight-coordinate Eu(iii) complex with 1,3-dibenzoylmethane (Hdbm) and 2-(1H-imidazol-2-yl)pyridine (impy), [Eu(dbm)₃(impy)], was synthesized and characterized via elemental analysis, FTIR spectroscopy, ESI-MS⁺ studies and thermal analysis (TGA/DTA).

Layered rare-earth hydroxide (LRH, R = Tb, Y) composites with fluorescein: delamination, tunable luminescence and application in chemosensoring for detecting Fe(iii) ions

We demonstrate a novel example of tunable luminescence and the application of the delaminated FLN/OS-LRH composites (LRHs are layered rare-earth hydroxides, R = Tb, Y; FLN is the fluorescein named 2-(6-hydroxy-3-oxo-(3H)-xanthen-9-yl)benzoic acid; OS is the anionic surfactant 1-octane sulfonic acid sodium) in detecting Fe(iii) ions. The FLNxOS1-x species (x = 0.02, 0.05, 0.10, and 0.20) are intercalated into the LTbyY1-yH layers (y = 1, 0.9, 0.7, 0.5, 0.3, 0.1 and 0) by ion exchange reactions to yield the composites FLNxOS1-x-LTbyY1-yH. In the solid state, the LYH composites display green emission (564 nm) arising from the organic FLN, while in LTbH composites, the luminescence of the Tb3+ in the layers (545 nm) and the FLN in the interlayers is co-quenched. In the delaminated state in formamide (FM), FLNxOS1-x-LTbH composites display green to yellowish-green luminescence (540-574 nm) following the increasing FLN/OS ratio; while the FLN0.02OS0.98-LTbyY1-yH composites show green emission at ∼540 nm. The fluorescence lifetimes of the composites (4.22-4.63 ns) are comparable to the free FLN-Na, and the quantum yields (31.62-78.70%) of the composites especially that (78.70%) of the FLN0.02OS0.98-LYH are much higher than that (28.40%) of free FLN-Na. The recognition ability of the FLN0.02OS0.98-LYH composite for metal cations is researched. The delaminated FLN0.02OS0.98-LYH colloidal suspension exhibits high selectivity for Fe3+ over other ions (Mg2+, Al3+, Ni2+, Co2+, Cu2+, Zn2+, Mn2+, Pb2+, and Cd2+) with fluorescence quenching, which can work as a kind of turn-off fluorescence sensor for the detection of Fe3+. The detection limit of Fe3+ is determined to be 2.58 × 10-8 M and the quenching constant (Ksv) is 1.70 × 103 M-1. This is the first work on LRH materials working as a chemosensor for recognising metal cations. It provides a new approach for the design of LRH materials to be applied in fluorescence chemosensing.

Multi-responsive luminescent sensor based on three dimensional lanthanide metal–organic framework

A novel multi-functional luminescent MOF was synthesized, which shows excellent recyclable luminescent sensing for acetone, Fe³⁺, Cr₂O₇²⁻ and 4-NP.

3D water-stable europium metal organic frameworks as a multi-responsive luminescent sensor for high-efficiency detection of Cr2O72−, MnO4−, Cr3+ ions and SDBS in aqueous solution

A 3D water-stable europium metal organic framework has been synthesized. Fluorescence measurements show that the MOF can selectively and sensitively detect Cr₂O₇²⁻, MnO₄⁻, Cr³⁺ ions and SDBS in aqueous solutions.

Color tuning and white light emission by codoping in isostructural homochiral lanthanide metal–organic frameworks

Pure white-light emission and fluent light-emitting color change can be facilely obtained by codoping isostructural homochiral lanthanide metal–organic frameworks.

Hydrothermal crystallization of a Ln2(OH)4SO4·nH2O layered compound for a wide range of Ln (Ln = La–Dy), thermolysis, and facile transformation into oxysulfate and oxysulfide phosphors

Ln-Dependent crystallization, structure, and thermolysis were systematically studied for layered Ln₂(OH)₄SO₄·nH₂O compounds, and their transformation into oxysulfate and oxysulfide phosphors was demonstrated.

A unique delaminated MoS4/OS-LEuH composite exhibiting turn-on luminescence sensing for detection of water in formamide

A delaminated MoS₄/OS-LEuH composite showed quenched luminescence in pure formamide while highly enhanced emission in the water-present case.