Lizi Yang

An efficient sensor for Zn2+ and Cu2+ based on different binding modes

An efficient sensor for Zn(2+) and Cu(2+) was designed based on different binding modes. The sensor displays ratiometric signals for Zn(2+), due to the Zn(2+)-triggered amide tautomerization; while dual-mode selective behaviors for Cu(2+) result from the deprotonation of the amide tautomer.

A sensitive colorimetric and ratiometric fluorescent probe for mercury species in aqueous solution and living cells

A highly sensitive and selective fluorescent probe for inorganic and organic mercury species displays colorimetric and ratiometric response in a buffer solution via mercury promoted cleavage reaction. The probe is demonstrated to detect CH(3)HgCl in living cells.

A Multi-responsive Regenerable Europium-Organic Framework Luminescent Sensor for Fe3+, CrVI Anions, and Picric Acid

A novel luminescent microporous lanthanide metal-organic framework (Ln-MOF) based on a urea-containing ligand has been successfully assembled. Structural analysis revealed that the framework features two types of 1D channels, with urea N-H bonds projecting into the pores. Luminescence studies have revealed that the Ln-MOF exhibits high sensitivity, good selectivity, and a fast luminescence quenching response towards Fe3+ , CrVI anions, and picric acid. In particular, in the detection of Cr2 O72- and picric acid, the Ln-MOF can be simply and quickly regenerated, thus exhibiting excellent recyclability. To the best of our knowledge, this is the first example of a multi-responsive luminescent Ln-MOF sensor for Fe3+ , CrVI anions, and picric acid based on a urea derivative. This Ln-MOF may potentially be used as a multi-responsive regenerable luminescent sensor for the quantitative detection of toxic and harmful substances.

Water-Soluble Colorimetric and Ratiometric Fluorescent Probe for Selective Imaging of Palladium Species in Living Cells

A novel water-soluble colorimetric and ratiometric fluorescent probe was synthesized and applied to imaging palladium species under physiological conditions in phosphate buffered saline (PBS) containing less than 1% organic cosolvent without adding any additional reagents. Based on palladium triggered terminal propargyl ethers cleavage reaction, the probe exhibited a high selectivity and sensitivity for palladium species of all the typical oxidation states (0, +2, +4), with a low detection limit (25 nM, 2.7 μg/L) and an obvious color change. Furthermore, the probe was successfully used for ratiometric fluorescence imaging of palladium in living cells.

A colorimetric and ratiometric fluorescent probe for distinguishing cysteine from biothiols in water and living cells

A merocyanine-based highly selective colorimetric and ratiometric fluorescent probe is described for Cys detection in water and diluted deproteinized human serum. Upon reaction with Cys in aqueous buffer solution, the probe showed a dramatic color change from faint yellow to pink and remarkable ratiometric fluorescence enhancement signals were also observed, which are ascribed to an intramolecular charge transfer (ICT) process. This strategy was based on modulating the merocyanine π-electron system by conjugation and removal of the acrylate group to release the chromophore group, resulting in a specific colorimetry and fluorescence response. The probe has low cytotoxicity and good cell permeability. It is readily employed for assessing the change of the intracellular Cys level.

A Highly Selective Two-Photon Fluorescent Probe for Detection of Cadmium(II) Based on Intramolecular Electron Transfer and its Imaging in Living Cells

A new quinoline-based probe was designed that shows one-photon ratiometric and two-photon off-on changes upon detecting Cd(2+) . It exhibits fluorescence emission at 407 nm originating from quinoline groups in Tris-HCl (25 mM, pH 7.40), H2 O/EtOH (8:2, v/v). Coordination with Cd(2+) causes quenching of the emission at 407 nm and simultaneously yields a remarkable redshift of the emission maximum to 500 nm with an isoemissive point at 439 nm owing to an intramolecular charge-transfer mechanism. Thus, dual-emission ratiometric measurement with a large redshift (Δλ=93 nm) and significant changes in the ratio (F500 /F439 ) of the emission intensity (R/R0 up to 27) is established. Moreover, the sensor H2 L displays excellent selectivity response, high sensitive fluorescence enhancement, and strong binding ability to Cd(2+). Coordination properties of H2 L towards Cd(2+) were fully investigated by absorption/fluorescence spectroscopy, which indicated the formation of a 2:1 H2 L/Cd(2+) complex. All complexes were characterized by X-ray crystallography, and TD-DFT calculations were performed to understand the origin of optical selectivity shown by H2 L. Two-photon fluorescence microscopy experiments have demonstrated that H2 L could be used in live cells for the detection of Cd(2+).

An 1,3,4-oxadiazole-based OFF–ON fluorescent chemosensor for Zn2+ in aqueous solution and imaging application in living cells

A new 1,3,4-oxadiazole-based fluorescence chemosensor 1, N-(2-ethoxy-2-oxoethyl)-N-(5-(2-hydroxy-3,5-di-tert-butylphenyl)-[1,3,4]oxadiazol-2-yl)glycine ethyl ester, has been designed and synthesized. Its fluorescence properties and selectivity for various metal ions were investigated in detail. A prominent fluorescence enhancement only for Zn(2+) was found in aqueous acetonitrile solution and the response mechanism of 1 was analyzed by time-resolved fluorescence decay and DFT calculations. Furthermore, the fluorescence imaging of Zn(2+) in living cells was successfully applied.

A sensitive colorimetric and ratiometric fluorescent chemodosimeter for Hg2+ and its application for bioimaging

A colorimetric and ratiometric fluorescent chemodosimeter for Hg2+ has been developed based on mercury ion-promoted hydrolysis of a naphthalimide-derived aryl vinyl ether. The chemodosimeter displays a highly sensitive and selective response with significant changes in both color (from colorless to jade-yellow) and fluorescence (from blue to green) in PBS buffer solution (containing 1% CH3CN, pH = 7.4). The chemodosimeter exhibits a ratiometric fluorescent response towards Hg2+ with a very low detection limit (3.6 nM), which can be used to detect Hg2+ ions in drinking water. Furthermore, the chemodosimeter has been successfully applied to the imaging of Hg2+ ions in living cells with an emission change from blue to green.

2D lanthanide MOFs driven by a rigid 3,5-bis(3-carboxy-phenyl)pyridine building block: solvothermal syntheses, structural features, and photoluminescence and sensing properties

A new series of five lanthanide(III) metal–organic frameworks with a general formula of [Ln3(bcpb)4(μ-HCOO)(μ-H2O)(H2O)2(DEF)]n (1–5) was generated by solvothermal reactions from Ln(NO3)3·6H2O {Ln = Eu (1), Tb (2), Gd (3), Dy (4), and Sm (5)} and 3,5-bis(3-carboxyphenyl)pyridine (H2bcpb) in an aqueous N,N-diethylformamide (DEF) medium. The obtained products were characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric analysis (TGA), and powder and single crystal X-ray diffraction. The latter reveals that all compounds (1–5) are isostructural and feature very intricate 2D metal–organic frameworks. These were topologically analyzed, revealing a very complex hexanodal underlying net that can be simplified further to a binodal 3,5-connected layer with the 3,5L52 topology. Solid-state photoluminescence properties of 1–5 were studied in detail. Compound 1 exhibits a strong red luminescence upon excitation at 338 nm and its lifetime is 532 μs. Compound 2 shows an intense green luminescence upon excitation at 336 and its lifetime is 981 μs. The triplet state (3ππ*) of bcpb2− studied by using the Gd(III) derivative 3 demonstrated that the ligand effectively populates Tb(III) emission (Φ = 70.96%), whereas the corresponding Eu(III) derivative 1 shows a weak luminescence efficiency (Φ = 15.81%) as the triplet state of bcpb2− has a poor match with the 5D0 energy level of Eu(III). A notable feature of 1 is its remarkable sensing ability for Cu2+ ions and 2,4,6-trinitrophenol (TNP). Besides, a series of heterobimetallic Tb-based MOFs, [Tb3(1−x)Eu3x(bcpb)4(μ-HCOO)(μ-H2O)(H2O)2(DEF)]n {x = 0.001, 0.002, 0.003, 0.01, 0.02, 0.03, 0.04, 0.10, 0.15, 0.20} (compounds 2a–2j, respectively), was prepared. The luminescence studies reveal that the simultaneous presence of the characteristic sharp emission bands of Eu3+ and Tb3+ allows the tuning of the photoluminescence colors of such materials by adjusting the doping concentration of the Eu3+ ions.

Structural diversity in new coordination polymers modulated by semirigid ether-linked pyridine-phthalate building block and ancillary ligands: syntheses, structures, and luminescence properties

Seven new 2D or 3D coordination polymers based on the flexible and semirigid pyridine-phthalate building block H2pbda (3-(pyridin-3-yloxy)benzene-1,2-dicarboxylic acid), namely 3D [Cd(pbda)]n (1), 3D [Cd3(OH)2(pbda)2]n (2), 3D [Cd(pbda)(4,4′-bpy)]n (3), 3D {[Co(pbda)(4,4′-bpy)]·2H2O}n (4), 2D {[Zn(pbda)(1,4-bib)]·H2O}n (5), 2D {[Cd(pbda)(1,4-bib)]·H2O}n (6), and 3D {[Co(pbda)(4,4′-bibp)]·2H2O}n (7), were prepared by hydrothermal reactions in the presence (optional) of an ancillary ligand selected from 4,4′-bpy (4,4′-bipyridine), 1,4-bib (1,4-bis(imidazol)butane), or 4,4′-bibp (bis(benzimidazol)propane). Compounds 1–7 were fully characterized and their crystal structures were classified from the topological viewpoint, resulting in the following topological networks: gis in 1, crb in 2, ins in 3 and 7, fsc-3,4-C2/c in 4, and sql in 5 and 6. The results revealed that the crystal architectures and the coordination modes of pbda building blocks are influenced by various factors, including the nature of metal cations, the solution pH, the temperature, and the presence of N-donor ancillary ligands. In addition, TGA data show that almost all compounds are thermally stable up to 300 °C. Zn(II) and Cd(II) derivatives are also strong luminescent emitters.