Efficient fluorescence-enhanced probe for cyanide ions based on a tetraphenylethene pyridine coordinated copper-iodide complex

An efficient fluorescence-enhanced probe was developed for detecting cyanide ions (CN^-) based on a tetraphenylethene coordinated copper-iodide complex (named CIT-Z). The coordination polymers (CPs) prepared were (Z)-1,2-diphenyl-1,2-bis[4-(pyridin-3-ylmethoxy)phenyl]ethene (1Z) and a CuI cluster, where the tetraphenylethylene (TPE) pyridine derivatives acted as organic ligands and the CuI cluster acted as a metal center. The higher-dimensional CIT-Z exhibited a 3-fold-interpenetrating network structure with excellent optical properties and chemical stability. This study also provides insights into the mechanism behind the fluorescence enhancement, which is attributed to the competitive coordination between CN^- and the ligands. The probe showed high selectivity and sensitivity towards CN^-, with a detection limit of 0.1 μM and good recovery in the real water samples.

Plasmonic Nano Silver: An Efficient Colorimetric Sensor for the Selective Detection of Hg2+ Ions in Real Samples

Environmental pollution caused by heavy metal ions has become a major health problem across the world. In this study, a selective colorimetric sensor based on starch functionalized silver nanoparticles (St-Ag NPs) for rapid detection of Hg2+ in real samples was developed. The environmentally friendly green approach was utilized to synthesize starch functionalized silver nanoparticles (St-AgNPs). A multi-technique approach involving UV-Vis absorption spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM) was used for the characterization of St-Ag NPs. These starch functionalized AgNPs were tested for the detection of heavy metals at 25 °C. The screening process revealed clear changes in the AgNPs color and absorption intensity only in the presence of Hg2+ due to the redox reaction between Ag0 and Hg2+. The color and absorption intensity of nanoparticles remain unchanged in the presence of all the other tested metals ion. The proposed method has strong selectivity and sensitivity to Hg2+ ions, with a detection limit of 1 ppm revealed by UV-visible spectrophotometry. The proposed procedure was found to be successful for the detection of Hg2+ in real samples of tap water.

Dicyanamide-intertwined assembly of two new Zn complexes based on N2O4-type pro-ligand: Synthesis, crystal networks, spectroscopic insights, and selective nitroaromatic turn-off fluorescence sensing

Two new dicyanamide bridged multinuclear Zn complexes, [Zn₂(L¹)(µ_1,5-dca)₂(µ₁-dca)]_n (1) and [Zn₂(L²)(µ_1,5-dca)₂(µ₁-dca)]_n (2) have been synthesized using N₂O₄-based pro-ligands (H₂L¹ = N,N'-bis(5-bromo-3-methoxysalicylidenimino)-1,3-diaminopropane, H₂L² = N,N'-bis(3-ethoxysalicylidene)-2,2-dimethyl-1,3-propanediamine) and characterized by microanalytical and spectroscopic techniques. Both complexes are stable in solution and solid-state. Thermogravimetric analysis (TGA) findings showed that complexes are stable at room temperature. Single-crystal X-ray diffraction (SCXRD) has proven that complexes are identical structures where two zinc metal ions are crystallographically independent. The directional properties of dicyanamide co-ligands via µ_1,5 bridging have resulted in different connectivity of zinc metal ions leading to 1D templates. SCXRD revealed some notable non-covalent interactions (π⋯π, C-H····π, and H-bonding) in their solid-state crystal structures. 1-2 have strong fluorescence behaviour over pro-ligands, which may be quenched in the presence of various electron-deficient explosive nitroaromatic compounds (epNACs). Complex 2 fluorescence intensity is sharper than 1; hence the former retained high sensitivity and selectivity for trinitrophenol (TNP). The enhancement of fluorescence mechanism, detection limit (LOD), and the quenching constant (K_SV) have been calculated using the Stern-Volmer equation (SV), where the K_SV value for TNP is found to be 1.542 × 10⁴ M^-1. The solution phase quenching mechanism has been rationalized by (a) electrostatic interactions through charge-transfer complex, (b) photo-induced electron transfer (PET) by the HOMO-LUMO energy gap via DFT, and (c) fluorescence resonance energy transfer (FRET). Finally, complex 2 is applied as a sensor by turn-off fluorescence response to detecting TNP nitroaromatics in the DMF medium.

Two Co(ii)-based coordination polymers as multi-responsive luminescent sensors for the detection of levofloxacin, benzaldehyde and Fe3+ ions in water media

Two CPs display excellent sensitivity, selectivity and low limits of detection for detection of LEV, BZH and Fe3+ ions.

Ultra-trace level detection of Cu2+ in an aqueous medium by novel Zn(ii)-dicarboxylato–pyridyl coordination polymers and cell imaging with HepG2 cells

Fluorescent 1D Zn(ii) coordination polymers are aggregated via noncovalent interactions. The emission of the CPs is exclusively quenched by Cu²⁺ and the LOD is at μM range. In aqueous medium internalization CPs within HepG2 cells is detected by microscopic cell image using Cu²⁺.

Efficient Identification for Alcohol Homologues and Hyperthermy Based on Coordination Polymer Multiple Structural Transformations

Recently, coordination polymer materials are of high interest due to the potential applications for chemical sensing and luminescent materials. In this work, we designed a photofluorescence coordination polymer material based on a donor-metal-acceptor structure. The donor-metal-acceptor architecture showed unusual multiple environmental responsiveness accompanied by a great change of fluorescence behaviors. Generally, organic homologue molecules are not easily distinguished by coordination polymer sensors because they have similar molecular structures and interaction sites. However, using the feature of multiple structural transformations, the accurate identification for organic homologue molecules can be realized, especially in a short time to quickly identify MeOH in other alcohol homologues (even in mixed atmospheres with only 10% MeOH). The visualization transformation of fluorescence can also be realized by single crystal to single crystal thermal-induced coordination bond ON/OFF behavior. The reversible structure conversion strategy provides new ideas for the accurate identification of organic homolog molecules or external environmental stimuli.

A dual-responsive luminescent sensor based on a water-stable Cd(ii)-MOF for the highly selective and sensitive detection of acetylacetone and Cr2O72− in aqueous solutions

Two water-stable cadmium(ii) MOFs were synthesized and characterized. 1 is the first dual-function Cd(ii)-MOF luminescent sensor for sensing acetylacetone and Cr₂O₇²⁻ in aqueous solution with high sensitivity and selectivity and good recyclability.

New two-dimensional Cd(ii) coordination networks bearing benzimidazolyl-based linkers as bifunctional chemosensors for the detection of acetylacetone and Fe3+

Two new CPs, namely {[Cd(L)(1,4-PDA)]·0.7(C₂H₅OH)}_n (1) and {[Cd(L)_0.5(1,8-NDC)·H₂O]}_n (2) were fabricated. 1 shows a sql 2D network. 2 shows a 2D 3,4L83 network. Both 1 and 2 were highly selective and sensitive fluorescent chemosensors toward acetylacetone and Fe³⁺.

A pyrazolopyrimidine based fluorescent probe for the detection of Cu2+ and Ni2+ and its application in living cells

A fluorescent sensor L based on a pyrazolopyrimidine core simultaneously detects Cu²⁺ and Ni²⁺ ions by photoluminescence quenching, even in the presence of other metal cations. Sensor L possesses high association constants of 5.24 × 10³ M^-1 and 2.85 × 10⁴ M^-1 and low detection limits of 0.043 μM and 0.038 μM for Cu²⁺ and Ni²⁺, respectively. The binding stoichiometry ratios of L to Cu²⁺ or Ni²⁺ is 1:1 as determined by Benesi-Hildebrand and Job's plots, and by crystal structures. DFT calculations on L-Cu²⁺ indicated reduced electron donation from the coordinated pyrazolopyridine to the fused pyrimidine and pendant phenyl group which, together with a smaller HOMO-LUMO orbital gap could favour non-radiative decay and explain the observed fluorescence quenching. Sensor L possessed low cytotoxicity and good imaging characteristics for Cu²⁺ and Ni²⁺ in living cells, suggesting potential applications for detecting Cu²⁺ and Ni²⁺in vivo.

Cd-Based metal-organic frameworks from solvothermal reactions involving in situ aldimine condensation and the highly sensitive detection of Fe3+ ions

Four Cd(ii)-based compounds (1-4) were synthesized from solvothermal reactions involving the in situ aldimine condensation of an o-diamino-functionalized precursor 3,6-di(4H-imidazol-4-yl)benzene-1,2-diamine (L), Cd(NO₃)₂·4H₂O and aldehyde. Two modes of cycloaddition ([4 + 1] cycloaddition and [4 + 2] cycloaddition) occurred during condensation, causing the in situ generation of two benzimidazole derivative ligands (L1 and L3) and a quinoxaline derivative ligand (L2). Furthermore, the chemical selectivity of the condensation was studied, where the condensation of o-diamino and the aldehyde is more stable and easy to operate. This strategy enriches the synthesis method of MOFs. Additionally, compound 2 containing uncoordinated quinoxaline N atoms showed excellent luminescent sensitivity for Fe³⁺ detection.

Highly selective luminescence sensing for the detection of nitrobenzene and Fe3+ by new Cd(ii)-based MOFs

Herein, three Cd(ii)-based MOFs were assembled, and the complex 3 showed a high selectivity in the detection of nitrobenzene and Fe³⁺.

A robust Zn(ii)/Na(i)-MOF decorated with [(OAc)2(H2O)2]n2n− anions for the luminescence sensing of copper ions based on the inner filter effect

A robust Zn(ii)/Na(i)-based MOF decorated with [(OAc)₂(H₂O)₂]_n²ⁿ⁻ anions was synthesized and employed as the probe for Cu²⁺ detection.

Luminescent Zn(ii) coordination polymers as efficient fluorescent sensors for highly sensitive detection of explosive nitroaromatics

Zn CPs 1–3 exhibit strong blue/cyan fluorescence emissions in toluene suspension for highly selective and sensitive detection of explosive nitroaromatics through remarkable fluorescence quenching responses. In addition, the framework Zn²⁺ ions in 3 were partially substituted by Cu²⁺ ions via a single-crystal to single-crystal (SCSC) transformation.

Rational synthesis of a luminescent uncommon (3,4,6)-c connected Zn(ii) MOF: a dual channel sensor for the detection of nitroaromatics and ferric ions

A 3D (3,4,6)-c connected net constructed using a rigid tetracarboxylate ligand and sensing studies to detect nitroaromatics and ferric ion performed.

Highly selective and sensitive detection of Hg2+, Cr2O72−, and nitrobenzene/2,4-dinitrophenol in water via two fluorescent Cd-CPs

Taking advantage of fluorescent Cd-CPs with 3,3′-thiodipropionic acid and imidazole ligands, herein, we demonstrate the synthesis of functional CPs, and develop two Cd-CP fluorescence sensing materials with highly selective and sensitive detection of Hg²⁺, Cr₂O₇²⁻, NB,/2,4-DNP in water.

A functionalized metal-organic framework decorated with O- groups showing excellent performance for lead(ii) removal from aqueous solution

A novel MOF decorated with O^– groups was elaborately constructed and showed excellent performance for Pb²⁺ removal.

Heavy metal ions are highly toxic and widely spread as environmental pollutants. New strategies are being developed to efficiently remove these toxic ions. Herein, we use the intrinsic advantages of metal–organic frameworks (MOFs) and develop a porous Zn(ii)-based MOF decorated with O^– groups for the removal of Pb²⁺. Benefiting from its multiple porosity, sufficient adsorption sites and strong affinity, the activated MOF material exhibits an ultrahigh Pb²⁺ uptake capacity (616.64 mg g^–1), surpassing all those of reported MOF adsorbents. Moreover, it can selectively capture Pb²⁺ with high efficiency (>99.27%) against background ions. Even in the presence of a high concentration of competitive ions, such as Ca²⁺ or Mg²⁺, effective removal (>99.21%) can also be achieved in a short time. The excellent removal performance demonstrates the strong electrostatic attraction and coordination interaction between the highly accessible O^– groups and Pb²⁺. The possible adsorption mechanism was systematically verified by zeta potential, FT-IR and XPS studies. Our work reveals the enormous potential of functionalized MOFs as an appealing platform to construct sorbent materials.

Luminescent Zn(II) Coordination Polymers for Highly Selective Sensing of Cr(III) and Cr(VI) in Water

Three photoluminescent zinc coordination polymers (CPs), {[Zn₂(tpeb)₂(2,5-tdc)(2,5-Htdc)₂]·2H₂O}_n (1), {[Zn₂(tpeb)₂(1,4-ndc)(1,4-Hndc)₂]·2.6H₂O}_n (2), and {[Zn₂(tpeb)₂(2,3-ndc)₂]·H₂O}_n (3) (tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene, 2,5-tdc = 2,5-thiophenedicarboxylic acid, 1,4-ndc = 1,4-naphthalenedicarboxylic acid, and 2,3-ndc = 2,3-naphthalenedicarboxylic acid) were prepared from reactions of Zn(NO₃)₂·6H₂O with tpeb and 2,5-H₂tdc, 1,4-H₂ndc, or 2,3-H₂ndc under solvothermal conditions. Compound 1 has a two-dimensional (2D) grid-like network formed from bridging 1D [Zn(tpeb)]_n chains via 2,5-tdc dianions. 2 and 3 possess similar one-dimensional (1D) double-chain structures derived from bridging the [Zn(tpeb)]_n chains via pairs of 1,4-ndc or 2,3-ndc ligands. The solid-state, visible emission by 1-3 was quenched by Cr³⁺, CrO₄^2-, and Cr₂O₇^2- ions in water with detection limits by the most responsive complex 3 of 0.88 ppb for Cr³⁺ and 2.623 ppb for Cr₂O₇^2- (pH = 3) or 1.734 ppb for CrO₄^2- (pH = 12). These values are well below the permissible limits set by the USEPA and European Union and the lowest so far reported for any bi/trifunctional CPs sensors. The mechanism of Cr³⁺ luminescence quenching involves irreversible coordination to free pyridyl sites in the CP framework, while the Cr⁶⁺ quenching involves reversible overlap of the absorption bands of the analytes with those of the excitation and/or emission bands for 3.

Luminescent cadmium(ii) coordination polymers of 1,2,4,5-tetrakis(4-pyridylvinyl)benzene used as efficient multi-responsive sensors for toxic metal ions in water

One luminescent cadmium(ii) coordination polymer of 1,2,4,5-tetrakis(4-pyridylvinyl)benzene works as an efficient multi-responsive sensor for Hg²⁺, CrO₄²⁻ and Cr₂O₇²⁻ in water.