Phenothiazine-based porous organic polymers with high sensitivity and selective fluorescence response to mercury ions

Phenothiazine Embedded Dithiasmaragdyrins

Two different types of novel phenothiazine-embedded dithiasmaragdyrins containing one phenothiazine ring, two thiophene rings and two pyrrole rings connected via three meso carbons and two direct bonds in the macrocyclic framework were synthesized over the sequence of synthetic steps starting with phenothiazine. Three examples of phenothiazine-embedded dithiasmaragdyrins were synthesized by condensing appropriate phenothiazine-based pentapyrrane with pentafluorobenzaldehyde and two examples of phenothiazine sulfone embedded dithiasmaragdyrins were synthesized by condensing phenothiazine-based diol with appropriate meso-aryl dipyrromethane under mild acid-catalysed conditions. 1D&2D NMR studies revealed that the thiophene rings adopted inverted orientation in phenothiazine sulfone embedded dithiasmaragdyrins whereas in phenothiazine-embedded dithiasmaragdyrins, the thiophene rings were in normal orientation. Both types of macrocycles exhibit nonaromatic absorption features and showed panchochromic absorption features in its neutral and protonated forms. The electrochemical studies indicated that the phenothiazine-embedded dithiasmaragdyrins were more electron-rich compared to phenothiazine sulfone embedded dithiasmaragdyrins. DFT studies revealed that both types of dithiasmaragdyrins exhibit significantly distorted structures and TD-DFT studies support the experimental observations.

Construction of fluorescent sensor array and three-dimensional microfluidic paper based analytical device for specific identification and visual determination of antibiotics in food

For antibiotics misuse since the global outbreak of COVID 19, a novel strategy for discriminating and detecting antibiotics is proposed based on the graphene quantum dots with multi-doped heteroatoms including F, N and P (M-GQDs), which exhibit blue emission (419.0 nm) under the excitation of 336.0 nm. Specifically, the fluorescence of M-GQDs is quenched by tetracyclines (TCs) owing to inner filter effect (IFE) and enhanced by alkane-modified fluoroquinolones (AFQs), which is attributed to restricted conformational rotation based on π-π stacking, hydrogen-bonding and electrostatic interactions. Meanwhile, the electron-accepting property of oxazine ring in oxazine-modified fluoroquinolones (OFQs) increases emission peak at 498.0 nm and decreases emission peak at 419.0 nm as the color changes from blue to cyan. Moreover, a cascade system integrated with 3D microfluidic paper-based analytical device (3D-μPAD) is applied successfully for visually distinguishing three antibiotics, which shows great potential and versatility of M-GQDs for food safety monitoring.

A 'turn-off' fluorescence sensor for selective Hg(II) based on phenothiazine derivative

Given how crucial it is to preserve a human-safe and sustainable environment, the rapid discovery of possibly lethal heavy metals such as Hg(II) has drawn much attention in recent years. A novel sensor, known as (E)-2-((10-octyl-10H-phenothiazin-3-yl)methylene)hydrazine-1-carbothioamide (PTZHC), was synthesized as a fluorescence 'on-off' sensor for Hg2+ ions. Coordination alters organic molecule electron densities, quenching the fluorescence intensity. PTZHC was described completely with the help of FTIR and 1 H-NMR spectrum studies. The Hg2+ ion was successfully detected using the PTZHC sensor even when there were other metal ions present. The limit of the detection was estimated to be 2.5 × 10-8  M and the Job's plot examination implied that PTZHC was bound to Hg2+ with a simple 1:1 stoichiometry in s CH3 CN/H2 O (9:1, v/v) suspension. To further cast light on the bridged effect on geometric and optoelectronic characteristics, time-dependent density functional theory (TD-DFT) at the B3LYP/6-31G(d) level and DFT were both examined.

Recent Development in Fluorescent Probes for the Detection of Hg2+ Ions

Mercury, a highly toxic heavy metal, poses significant environmental and health risks, necessitating the development of effective and responsive techniques for its detection. Organic chromophores, particularly small molecules, have emerged as promising materials for sensing Hg²⁺ ions due to their high selectivity, sensitivity, and ease of synthesis. In this review article, we provide a systematic overview of recent advancements in the field of fluorescent chemosensors for Hg²⁺ ions detection, including rhodamine derivatives, Schiff bases, coumarin derivatives, naphthalene derivatives, BODIPY, BOPHY, naphthalimide, pyrene, dicyanoisophorone, bromophenol, benzothiazole flavonol, carbonitrile, pyrazole, quinoline, resorufin, hemicyanine, monothiosquaraine, cyanine, pyrimidine, peptide, and quantum/carbon dots probes. We discuss their detection capabilities, sensing mechanisms, limits of detection, as well as the strategies and approaches employed in their design. By focusing on recent studies conducted between 2022 and 2023, this review article offers valuable insights into the performance and advancements in the field of fluorescent chemosensors for Hg²⁺ ions detection.

Novel Carbazole-Based Porous Organic Polymer for Efficient Iodine Capture and Rhodamine B Adsorption

A new porous organic polymer (CTF-CAR), which takes carbazole as the electron-rich center unit and thiophenes as the auxiliary group, has been synthesized through catalyst-free Schiff-base polymerization. At the same time, the structure, thermal stability, morphology, and other basic properties of the polymer were analyzed by IR, NMR, TGA, and SEM. Then, CTF-CAR was applied to iodine capture and rhodamine B adsorption. Due to its strong electron donor ability and abundant heteroatom binding sites, which have a positive effect on the interaction between the polymer network and adsorbates, CTF-CAR exhibits high uptake capacities for iodine vapor and rhodamine B as 2.86 g g-1 and 199.7 mg g-1, respectively. The recyclability test also confirmed that it has good reusability. We found that this low-cost and catalyst-free synthetic porous organic polymer has great potential for the treatment of polluted water and iodine capture.

TEGylated Phenothiazine-Imine-Chitosan Materials as a Promising Framework for Mercury Recovery

This paper reports new solid materials based on TEGylated phenothiazine and chitosan, with a high capacity to recover mercury ions from aqueous solutions. They were prepared by hydrogelation of chitosan with a formyl derivative of TEGylated phenothiazine, followed by lyophilization. Their structural and supramolecular characterization was carried out by 1H-NMR and FTIR spectroscopy, as well as X-ray diffraction and polarized light microscopy. Their morphology was investigated by scanning electron microscopy and their photophysical behaviour was examined by UV/Vis and emission spectroscopy. Swelling evaluation in different aqueous media indicated the key role played by the supramolecular organization for their hydrolytic stability. Mercury recovery experiments and the analysis of the resulting materials by X-ray diffraction and FTIR spectroscopy showed a high ability of the studied materials to bind mercury ions by coordination with the sulfur atom of phenothiazine, imine linkage, and amine units of chitosan.