Fluorescence modulation of an aggregation-induced emission active ligand via rigidification in a coordination polymer and its application in singlet oxygen sensing

A new Zn(II)-based coordination polymer (CP) having the formula [Zn(L)(2,2'-bpy)] (1) was synthesized using ZnCl2, 3,3'-(anthracene-9,10-diyl)diacrylic acid ligand (H2L), and 2,2'-bipyridine (2,2'-bpy) in DMF under solvothermal conditions. Here, the anthracene-based dicarboxylic acid ligand shows aggregation-induced emission (AIE) activity in an ethanol/hexane medium. Single-crystal X-diffraction analysis reveals that the one-dimensional (1D) zigzag chainlike structure of 1 is assembled from tetrahedrally coordinated Zn2+ ions interconnected by 2,2'-bpy and ditopic anthracene-based ligand molecules. The crystal structure analysis reveals that the ditopic anthracene-based flexible ligand adopts a twisted conformation in the CP crystal compared to its free state. Because of the twisted conformation of the ATE active ligand in the CP crystal, a large (similar to 80 nm) hypsochromic shift was observed in the emission spectrum with a drastic color change compared to the free state of ligand. The origin of these rare fluorescence properties is ascribed to the twisted diacrylic acid ligand conformation and rigidity in the CP crystal. An unprecedented response was observed toward singlet oxygen (O-1(2)) by 1 via a fluorescence turn-off mechanism. The presence of the anthracene moiety is the main influential factor for O-1(2) sensing, which undergoes [4 + 2] cycloaddition reaction with O-1(2), producing a nonemissive 9,10-endoperoxide product. The unique photoluminescence properties along with tunable fluorescence responses indicate that incorporating an AIE active anthracene core into the CP crystal is a beneficial strategy to develop new fluorescent materials with significant sensing ability

Aqueous Medium Fluoride Anion Sensing by Fluorophore Encapsulated UiO-66 Type Zirconium Metal–Organic Framework

A well-known fluorophore molecule, pyrene was encapsulated into a stable metal organic framework by in situ encapsulation method. The existing metal-organic framework (MOF) called UiO-66 (UiO = University of Oslo) served as host material for pyrene fluorophore. The fluorescence of pyrene was quenched after encapsulation inside the porous host. Recovery of quenched fluorescence was accomplished by anion induced host dissolution, followed by the release of the fluorophore molecule. Using this anion induced dissolution, a selective sensing of fluoride anion in pure aqueous was achieved

A Dual Fluorometric and Colorimetric Sulfide Sensor Based on Coordinating Self-Assembled Nanorods: Applicable for Monitoring Meat Spoilage

Psychrotrophic bacteria, commonly called spoilage bacteria, can produce highly toxic hydrogen sulfide (H2S) in meat products. Thus, monitoring the presence of hydrogen sulfide in meat samples is crucial for food safety and storage. Here, we report a unique chemical sensor based on supramolecular nanorods synthesized via copper ion induced self-assembly of N,N-bis[aspartic potassium salt]-3,4,9,10-perylenetetracarboxylic diimide (APBI-K). The self-assembled nanorods can specifically detect sulfide with a detection limit of 0.181 μM in solution. The nanorods suspended in pure water show a turn-on fluorescence sensing behavior along with color change, acting as a dual fluorometric and colorimetric sensor. Spectroscopic investigation confirms the sensing mechanism due to copper ion displacement induced by the association with sulfide. Based on the high selectivity and sensitivity, supramolecular nanorod sensors were successfully employed to detect H2S in spoiled meat sample as well as dissolved H2S in water

Correction: Dalapati et al. A Dual Fluorometric and Colorimetric Sulfide Sensor Based on Coordinating Self-Assembled Nanorods: Applicable for Monitoring Meat Spoilage. <i>Chemosensors</i> 2022, <i>10</i>, 500

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Understanding the role of tetramethyl urea for the synthesis of mesoporous alumina

Mesoporous alumina was synthesized by hydrothermal method at 150 °C for 6–24 h using tetramethyl urea followed by their calcination at 500–1100 °C. The samples were characterized by XRD, FTIR, N2 adsorption–desorption, FESEM and TEM. The γ-Al2O3 was found to be stable up to 1000 °C for the samples prepared at 150 °C/6 h, and up to 900 °C for the samples prepared at 150 °C/12–24 h. The BET surface area values of 500 °C treated samples were 428 m2 g−1, 393 m2 g−1, and 366 m2 g−1 for the reaction time of 6 h, 12 h and 24 h, respectively. FESEM and TEM showed the formation of alumina nanoparticles at 150 °C/6 h, which ripened to flake-shaped alumina comprising of alumina nanoflakes (70–100 nm) at 150 °C/12–24 h. To understand the role of tetramethyl urea, a tentative formation mechanism was illustrated

Structural Diversity in Supramolecular Organization of Anionic Phosphate Monoesters: Role of Cations

Syntheses and structures of anionic arylphosphate monoesters [ArOP­(O)2(OH)]− (Ar = 2,6-CHPh2-4-R-C6H2; R = Me/Et/iPr/tBu) with different counter cations are reported. The counter cations were varied systematically: imidazolium cation, 2-methyl imidazolium cation, N-methyl imidazolium cation, N,N′-alkyl substituted imidazolium cation, 1,4-diazabicyclo[2.2.2]­octan-1-ium cation, 4,4′-bipyridinium dication, and magnesium­(II) dication. The objective was to examine if the supramolecular structure of anionic arylphosphate monoesters could be modulated by varying the cation. It was found that an eight-membered P2O4H2-hydrogen-bonded dimeric motif involving intermolecular H-bonding between the [P­(O)­(OH)] unit of the anionic phosphate monoester along with the counter cation is formed with 2-methyl imidazolium cation, N-methyl imidazolium cation, N,N′-alkyl substituted imidazolium cation, 1,4-diazabicyclo[2.2.2]­octan-1-ium cation, and magnesium­(II) dication; both discrete and polymeric H-bonded structures are observed. In the case of imidazolium cations and 1,4-diazabicyclo[2.2.2]­octan-1-ium cation, the formation of one-dimensional polymers (single lane/double lane) was observed. On the other hand, two types of phosphate motifs, intermolecular H-bonded dimer and an open-form, were observed in the case of 4,4′-bipyridinium dication