Photoluminescence of Lanthanide-Titanium-Oxo Clusters and Based on a β-Diketone Ligand

Hg2+ detection and information encryption of new [1+1] lanthanide cluster

The sensing of heavy metal ion and information encryption are two very important research areas. Therefore, developing multi-functional materials capable of sensing heavy metal ions and encrypting information is highly important. In this work, three [1 + 1] lanthanide clusters [Ln(TFBA)3(dmp) (H2O)2]2 (Ln = Tb3+Tb1+1, Eu3+Eu1+1, Gd3+Gd1+1, HTFBA = 2,3,4,5-tetrafluorobenzoic acid, dmp = 4,7-dimethyl-1,10-phenanthroline) were designed and synthesized. Among them, Tb1+1 shows excellent luminescence sensing towards Hg2+ (Ex = 350 nm, Em = 545 nm). Results demonstrates the sensing with high selectivity, strong anti-interference, 20-s response time, high accuracy, excellent linear relationship in 0-20.0 μM, and a very low limit of detection (0.02 ppb). Furthermore, paper strips based on Tb1+1 is fabricated for visual detection of Hg2+ in real samples of tap water, lake water, human urine, and human serum. More interestingly, a new method for confidentiality of information is realized through multi-color anti-counterfeiting patterns with the [1 + 1] lanthanide cluster ink, based on the luminescence "on-off" sensing towards Hg2+.

Doping transition metals to modulate the chirality and photocatalytic activity of rare earth clusters

In this paper, we report the successful assembly of achiral {Ln6M} ([Ln6M(μ3-OH)8(acac)12(CH3O)x(CH3OH)y], Ln = La, M = Mn, Co, Fe) and chiral {Nd9Fe2} ([Nd9Fe2(μ4-O)(μ3-OH)14(acac)16(NO3)(CH3OH)2(H2O)3]) rare earth clusters using achiral rigid ligands and a transition metal doping strategy. {Ln6M} can be viewed as the fusion of two {Ln3M} tetrahedrons by sharing vertices. {Nd9Fe2} results from the fusion of four {Ln3M} tetrahedrons by vertice and edge sharing. The substitution of Ln with transition metal leads to changes in the coordination pattern around neighboring Ln, which triggers the switch of metal center chirality. This study demonstrates the potentiality of utilizing transition metal doping and rigid ligand to control the chirality of rare earth clusters. In addition, the photocatalytic CO2 activity of these transition metal-doped rare earth clusters has been studied.

Tetra-Nuclear Cluster-Based Lanthanide Metal-Organic Frameworks as White Phosphor, Information Encryption, Self-Calibrating Thermometers, and Fe2+ Sensors

The application of one kind of metal-organic framework (MOF) material used in multiple fields is one of the most interesting research topics. In this work, four new tetra-nuclear cluster-based lanthanide metal-organic frameworks (LnMOFs) [Ln₂(BTDB)₃(DMA)(phen)]_n (Ln = Tb TbMOF, Eu EuMOF, Gd GdMOF, Tb_1.830Eu_0.170 Tb,EuMOF, 3,5-bis(trifluoromethyl)-4',4″-dicarboxytriphenylamine = H₂BTDB, 1,10-phenanthroline = phen) are obtained based on the ligand of H₂BTDB that is synthesized in our laboratory, and the precise single-crystal structure of H₂BTDB is obtained for the first time. The white phosphor was obtained by facilely hybridizing two components of the orange-yellow emission phosphor of Tb,EuMOF and the blue luminescence material of triphenylamine according to the trichromatic theory. At the same time, TbMOF, EuMOF, Tb,EuMOF, and the white phosphor can be used for information encryption, demonstrating their potential application in the field of anti-counterfeiting. Tb,EuMOF is also a multi-mode and self-calibrating thermometer within a broad temperature range of 110-300 K. Further studies show that EuMOF is a rapid response sensor for Fe²⁺, with a very low limit of detection of 2.0 nM, which is much lower than the national standards for Fe²⁺ (GB 5749-2005, 5.357 μM). It can achieve strong anti-interference detection of Fe²⁺ in actual samples of tap water and lake water. In addition, EuMOF can also be made into an easy-to-use sensing device of test paper for real-time and visual sensing of Fe²⁺.

Visual and Real-Time Monitoring of Cd2+ in Water, Rice, and Rice Soil with Test Paper Based on [2 + 2] Lanthanide Clusters

Cadmium ions (Cd²⁺) are highly toxic to animal and human health, especially through the drinking of Cd²⁺-contaminated water and eating Cd²⁺-contaminated rice. Therefore, accurate detection of Cd²⁺ in water, rice, and rice soil is urgent. In this work, two [2 + 2] lanthanide clusters of Tb₂Tb₂ and Eu₂Eu₂ were synthesized and characterized in detail. Interestingly, Tb2Tb2 is a rapid sensor for Cd²⁺ through luminescence "turn-off". Further studies show that Tb2Tb2 is a highly sensitive and selective sensor toward Cd²⁺ in water, rice supernatants, and rice soil supernatants, with a very short response time of 20 s. The limit of detection (LOD) in the above three real samples is as low as 0.0112, 1.1240, and 0.1124 ppb, respectively, which is lower than the national standards for food safety in China (GB 2762-2022). More interestingly, a portable sensing device of test paper based on Tb2Tb2 is developed with a facile method, which shows visible, highly sensitive, and selective sensing toward Cd²⁺ in real samples of water, rice supernatants, and rice soil supernatants. Tb2Tb2 and its sensing device of test paper are an on-site analysis sensor for potentially non-expert users, especially for people in remote rural areas.

Two Windmill-Shaped Ln18 Nanoclusters Exhibiting High Magnetocaloric Effect and Luminescence

The self-assembly of the high-nuclearity Ln-exclusive nanoclusters is challenging but of significance due to its aesthetically pleasing architectures and far-reaching latent applications in magnetic cooling technologies. Herein, two novel high-nuclearity lanthanide nanoclusters were successfully synthesized under solvothermal conditions, formulated as {[Gd₁₈(IN)₂₀(HCOO)₈(μ₆-O)(μ₃-OH)₂₄(H₂O)₄]·4H₂O}_n and {[Eu₁₈(IN)₁₆(HCOO)₈(CH₃COO)₄(μ₆-O)(μ₃-OH)₂₄(H₂O)₄]·5H₂O}_n (abbreviated as Gd₁₈ and Eu₁₈, HIN = isonicotinic acid). Both of them possess novel and exquisite windmill-shaped cationic cores in the family of high-nuclearity Ln-exclusive nanoclusters. Remarkably, the adjacent second building units are interconnected into a three-dimensional (3D) metal-organic framework by IN^- ligands. As expected, the abundant existence of Gd^III ions endows Gd₁₈ with a favorable magnetic entropy change at 2.0 K for ΔH = 7.0 T (-ΔS_m^max = 40.0 J kg^-1 K^-1), and Eu₁₈ displays the typical luminescence of Eu^III ions.

Circularly polarized luminescence and performance modulation of chiral europium-titanium (Eu2Ti4)-oxo clusters

The designed synthesis of chiral luminescent molecules with excellent circularly polarized luminescence (CPL) performance and high quantum yield (QY) levels has attracted great interest but remains very challenging. Herein, we report three pairs of chiral europium-titanium-oxo clusters featuring both modest CPL characteristics and high QY levels (up to 79%), which can be regulated by switching between different ligand substituents.

Upcycling waste expanded polystyrene into UV-excited dual-mode multicolor luminescent electrospun fiber membranes for advanced anti-counterfeiting†

Expanded polystyrene (EPS) is causing severe environmental problems due to its high consumption and non-biodegradability. Upcycling waste EPS into high value-added functional materials is highly advisable in terms of sustainability and environmental concerns. Meanwhile, it is imperative to develop new anti-counterfeiting materials with high security against increasingly high-tech counterfeiting. Developing UV-excited dual-mode luminescent advanced anti-counterfeiting materials that can be excited by commonly used commercial UV light sources (such as 254 nm and 365 nm wavelengths) remains a challenge. Herein, UV-excited dual-mode multicolor luminescent electrospun fiber membranes were fabricated from waste EPS by co-doping with a Eu³⁺ complex and a Tb³⁺ complex via electrospinning. The SEM results prove that the lanthanide complexes are uniformly dispersed in the PS matrix. The luminescence analysis results suggest that all the as-prepared fiber membranes with the different mass ratios of the two complexes can exhibit the characteristic emission of Eu³⁺ ions and Tb³⁺ ions under UV light excitation. The corresponding fiber membrane samples can exhibit intense visible luminescence with different colors under UV lights. Moreover, each membrane sample can display different color luminescence irradiated with UV light at 254 nm and 365 nm, respectively, e.g. show excellent UV-excited dual-mode luminescent properties. This is owing to the different UV absorption properties of the two lanthanide complexes doped in the fiber membrane. Finally, the fiber membranes with different color luminescence from green light to red light were achieved by tuning the mass ratio of the two complexes in the PS matrix and changing UV irradiation wavelengths. The as-prepared fiber membranes with tunable multicolor luminescence are very promising for high-level anti-counterfeiting applications. This work is very meaningful not only to upcycle waste EPS to high value-added functional products but also to develop advanced anti-counterfeiting materials.

A simple and effective method to upcycle waste EPS to UV-excited dual-mode multicolor luminescent membranes for advanced anti-counterfeiting was developed.

Pentagram-type Ln15 (Ln = Dy, Tb, Eu, Sm, Ho) clusters with different anion templates: magnetic and luminescence properties

Five pentagram-type Ln15 clusters with different anion templates were obtained. The pentagonal skeleton is composed of five cubane-like [Ln4(μ3-OH)4] building units. The magnetic properties and the luminescence behavior were investigated.