A zinc(II) triazolate framework with luminescence response toward dichromate anion in aqueous solution

A cellulose-based material as a fluorescent sensor for Cr(VI) detection and investigation of antimicrobial properties of its encapsulated form in two different MOFs

It is crucial to detect toxic chromium ions quickly, reliably, sensitively and at low concentrations. In recent years, fluorescence-based methods have been developed for the rapid detection and determination of toxic ions such as chromium. In present work, we focused on the development of a cellulose-based fluorescent probe (Cel-Nap) for the determination of Cr(VI). The fluorescent probe bearing the 1,8-naphthalimide group displayed a low LOD of 1.07 μM for Cr(VI) in the working range of 0.33 × 10^-5-3.22 × 10^-5 M. The fluorescence and antibacterial properties of UiO-66-Cel-Nap and ZIF-8-Cel-Nap materials prepared by encapsulating Cel-Nap with 2 different MOF types (UiO-66 and ZIF-8) were investigated. While it was found that ZIF-8-based materials had better antimicrobial properties compared to those of UiO-66, it was determined that materials containing Ag⁺ were more effective against microbial than those containing AgNPs. It was found that the most effective material was ZIF-8-Cel-Nap-Ag⁺ and it had a significant antibacterial effect against E. coli at a MIC value of 0.0024 mg/mL.

A water-soluble naphthalimide fluorescent probe for Cr2O72- and Fe3+ based on inner filter effect

A probe 3 (2-ethoxy-N-(2-(2-(2-hydroxyethoxy)ethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de] isoquinolin-6-yl)benzamide) that could selectively respond to Cr₂O₇^2- and Fe³⁺ was reported in this paper. The selectivity, pH titration, concentration titration, detection limit, time dependence, quenching constant and recognition mechanism of probe 3 for Cr₂O₇^2- and Fe³⁺ were studied in CH₃CN/HEPES buffer solution. The results showed that Cr₂O₇^2- and Fe³⁺ could rapidly quench the fluorescence of probe 3 through the inner filter effect (IFE). The quenching kept constant after 30 s, and the quenching constants were 7.99 × 10³ L^.mol^-1 and 4.13 × 10³ L^.mol^-1, respectively. The detection limits of probe 3 for Cr₂O₇^2- and Fe³⁺ were 1.15 μmol^.L^-1 and 1.95 μmol^.L^-1, respectively, which were lower than the maximum allowable concentrations in drinking water stipulated by EPA. The determination results of Cr₂O₇^2- and Fe³⁺ in water samples indicated that probe 3 could be used as a potential detection tool in practical applications.

Synthesis of new anthracene-substituted calix[4]triazacrown-5 as highly sensitive fluorescent chemosensor and extractant against hazardous dichromate anion

A new fluorogenic anthracene functionalized calix[4]triazacrown-5 (Ant-AzClx) was successfully synthesized using a simple Schiff's base reaction. The ¹ H-NMR, ¹³ C-NMR, ESI-MS, and elemental analysis techniques were performed to characterize its structure. Excited at 370 nm, Ant-AzClx reveals excimer emission at 418 nm. Therefore, its anion binding properties were investigated against F^- , HCO₃ ^- , H₂ PO₄ ^- , NO₃ ^- , Cr₂ O₇ ^2- , and SO₄ ^2- ions. When hazardous dichromate anion was introduced into medium, the fluorescence intensity of Ant-AzClx was markedly quenched. The binding constant, stoichiometry, the detection limits and Stern-Volmer equation for the complex formed between Ant-AzClx and Cr₂ O₇ ^2- ion were determined. Furthermore, the ¹ H-NMR technique was also performed to assess the mechanism of the complex (Ant-AzClx@Cr₂ O₇ ^2- ). Apart from its excellent fluorescent chemosensor properties for selective and sensitive recognition of Cr₂ O₇ ^2- ion, Ant-AzClx was used as an efficient extractant towards dichromate anion. The extraction results indicated that Ant-AzClx exhibited high extraction capability, leading to it being a promising extractant for the removal of dichromate anions from water.

Electrochemiluminescence properties and luminescence sensing of four novel polymers derived from 3-(pyrazin-2-yl)-1H-pyrazole-5-carboxylic acid

Four novel pyrazolate polymers with high efficiency electrochemiluminescence properties and potential cationic fluorescence sensoring property.

Pore-Functionalized and Hydrolytically Robust Cd(II)-Metal-Organic Framework for Highly Selective, Multicyclic CO2 Adsorption and Fast-Responsive Luminescent Monitoring of Fe(III) and Cr(VI) Ions with Notable Sensitivity and Reusability

Metal-organic frameworks (MOFs) show a distinctive pre-eminence over other heterogeneous systems for adsorption of carbon dioxide (CO₂) gas and fluorescence detection of water contaminating ions, where integration of both these attributes along with enhancement of pore functionality and water stability is crucial for potential applications related to environmental remediation. Pore functionalization has been achieved in a 2-fold interpenetrated, mixed-ligand Cd(II)-framework [Cd_1.5(L)₂(bpy)(NO₃)]·2DMF·2H₂O (CSMCRI-5) (HL = 4-(4-carboxyphenyl)-1,2,4-triazole, bpy = 4,4'-bipyridine, DMF = dimethylformamide, CSMCRI = Central Salt & Marine Chemicals Research Institute) by utilizing a bifunctional ligand HL. The bpy-pillared framework, containing diverse Cd(II) nodes, optimum sized voids, and free N-atom affixed one-dimensional porous channels, shows notable structural robustness in diverse organic solvents and water. In spite of a negligible surface area, the activated MOF (5a) exhibits good CO₂ uptake and highly selective CO₂ adsorption over N₂ (259.94) and CH₄ (14.34) alongside minor loss during multiple CO₂ adsorption-desorption cycles. Luminescence studies demonstrate extremely selective and ultrafast sensing of Fe³⁺ ions in the aqueous phase with notable quenching (1.13 × 10⁴ M^-1) as well as an impressive 98 ppb limit of detection (LOD). Importantly, Fe³⁺ detection is exclusively retained under simulated physiological conditions. The framework further serves as a quick-responsive scaffold for toxic CrO₄^2- and Cr₂O₇^2- anions, where individual quenching constants (CrO₄^2-: 1.73 × 10⁴ M^-1; Cr₂O₇^2-: 5.42 × 10⁴ M^-1) and LOD values (CrO₄^2-: 280 ppb; Cr₂O₇^2-: 320 ppb) rank among the best sensory MOFs for aqueous phase detection of Cr(VI) species. It is imperative to stress vivid monitoring of all these aqueous pollutants by a handy paper-strip method, besides outstanding applicability of 5a toward their recyclable detection. Mechanism of selective quenching is comprehensively investigated in light of the absorption of the excitation/emission energy of the host framework by an individual studied analyte.