One high-nuclearity Eu18 nanoring with rapid ratiometric fluorescence response to dipicolinic acid (an anthrax biomarker)

Two Three-Dimensional LnIII Coordination Polymers Exhibiting Luminescent Sensing and a Magnetocaloric Effect

Two lanthanide 3D coordination polymers [Ln2(L)4Cl2(H2O)4]n (Ln = Eu (1), Gd (2)) with quinoline-2-carboxylic acid (HL) as the ligand were successfully synthesized and characterized. Complex 1 exhibits a highly sensitive and selective luminescent response to 2,6-dipicolinic acid (DPA) in tap water and is virtually unaffected by interferences such as amino acids, aromatic carboxylic acids, and ions. With the addition of DPA, the luminescence intensity of complex 1 decreases rapidly to the naked eye. The detection limit of 1 toward DPA is 3.36 μM, which is much less than the infectious dose (60 μM) of the anthrax spores, indicating the high sensitivity of 1 to DPA. This study offers a basis for employing lanthanide complexes in real sample analysis, enabling direct and efficient detection of DPA with high sensitivity and specificity. Additionally, it is noteworthy that at a magnetic field strength of 7 T and a temperature of 3 K, the maximum entropy change for complex 2 attains a value of 23.56 J kg-1 K-1.

Highly sensitive sensing of DPA by lanthanide metal-organic frameworks and detection of fiber membranes

The detection of 2,6-pyridinecarboxylic acid (DPA), as a biomarker of Bacillus anthracis, has attracted wide attention. In previous reports of DPA detection, fluorescent probes may not have high specificity. Therefore, the rational design and development of fluorescent sensors with excellent performance is of great significance for the detection of DPA. In this study, two novel lanthanide metal-organic frameworks (Ln-MOFs) were synthesized by hydrothermal method using 3-polyfluorobiphenyl-3 ', 4,5 ' -tricarboxylic acid (H2FPTA) as ligand. Studies have shown that Ln-MOFs can detect DPA in real time, with detection limits of 0.54 μM and 0.67 μM, respectively, and have a high recovery rate (95 % -108 %) in fetal bovine serum. As a self-calibration sensor, other substances in the blood can be clearly distinguished by a two-dimensional fluorescence code diagram. After the Ln-MOFs were spun into nanofiber membranes, they responded quickly to DPA. This increases practicability and provides a promising idea for the development of simple and efficient ratio sensors.

Determination of 2, 6-dipicolinic acid as an Anthrax biomarker based on the enhancement of copper nanocluster fluorescence by reversible aggregation-induced emission

The weak fluorescence efficiency of copper nanoclusters (Cu NCs) limits their wide applications in biosensing and bioimaging areas, while the aggregation-induced emission (AIE) effect is anticipated to increase their luminescence intensity. Herein, the weak red emission of Cu NCs is increased considerably by the addition of lanthanide Tb³⁺, ascribed to the AIE effect. Monitoring of spores contamination can be carried out by determining the level of 2, 6-dipicolinic acid (DPA), which is a marker of spores. Due to the stronger synergy between DPA and Tb³⁺ for its clamped configuration of adjacent pyridine nitrogen group with the carboxylic acid group, the addition of DPA leads Tb³⁺ to be taken away from Cu NCs through a stronger coordination effect, causing Cu NCs to return to the dispersed state and weakened fluorescence. Based on this, an "off-on-off" fluorescent probe for DPA sensing was built, in which Tb³⁺ was used as a bridge to achieve AIE enhanced fluorescence effect on Cu NCs as well as a specific recognizer of DPA. The detection range for DPA was 0.1-60 μM and the detection limit was 0.06 μM, which was much lower than the infectious dose of anthrax spores. Since DPA is a unique biomarker for bacterial spores, the method was applied to the detection of actual bacterial spores and satisfactory results were obtained with a detection limit of 4.9*10³ CFU mL^-1.

Lanthanide molecular cluster-aggregates as the next generation of optical materials

In this perspective, we provide an overview of the recent achievements in luminescent lanthanide-based molecular cluster-aggregates (MCAs) and illustrate why MCAs can be seen as the next generation of highly efficient optical materials. MCAs are high nuclearity compounds composed of rigid multinuclear metal cores encapsulated by organic ligands. The combination of high nuclearity and molecular structure makes MCAs an ideal class of compounds that can unify the properties of traditional nanoparticles and small molecules. By bridging the gap between both domains, MCAs intrinsically retain unique features with tremendous impacts on their optical properties. Although homometallic luminescent MCAs have been extensively studied since the late 1990s, it was only recently that heterometallic luminescent MCAs were pioneered as tunable luminescent materials. These heterometallic systems have shown tremendous impacts in areas such as anti-counterfeiting materials, luminescent thermometry, and molecular upconversion, thus representing a new generation of lanthanide-based optical materials.

Rapid and Reliable Excitation Wavelength-Dependent Detection of 2,6-Dipicolinic Acid Based on a Luminescent Cd(II)-Tb(III) Nanocluster

A Cd(II)-Tb(III) nanocluster {[Cd₁₀Tb₉L₈(OH)₁₆(OAc)₂₃(H₂O)₃][Cd₁₀Tb₉L₈(OH)₁₆(OAc)₂₃(H₂O)₄]}·3H₂O (1), which contains two crystallographically independent components, was constructed from a tridentate ligand (HL, 3-ethoxysalicylaldehyde). It exhibits rapid and reliable excitation wavelength-dependent luminescence response to 2,6-dipicolinic acid (DPA) [limit of detection = 0.23 nM], which is not influenced by aromatic carboxylates, amino acids, and ions. The test papers of 1 can be used to check DPA in solution. The equation I_Ex272nm/I_Ex329nm = 0.0109 × [DPA]2 + 0.106 × [DPA] + 2.39 of 1 for the luminescence response could be used to quantitatively measure the concentration of DPA in tap water. 1 displays rapid and stable luminescence response to DPA, with the sensing times shorter than 5 s and no changes for the lanthanide luminescence over 24 h.