A near-infrared ratiometric fluorescent probe for simultaneous detection of hydrazine and hypochlorous acid in biological systems and its portable detection in environmental samples using a smartphone

Hydrazine (N2H4) and hypochlorous acid (HClO) are significant chemicals that gain widespread applications in industrial fields. Excessive N2H4 and HClO can cause severe environmental pollution and have toxic effects on living organisms. In this study, a near-infrared (NIR) dual-responsive fluorescent probe PTZ-BA was designed for the ratiometric detection of N2H4 and HClO. PTZ-BA exhibited a remarkable near-infrared signal at 680 nm with a large Stokes shift of 275 nm, and it can simultaneously detect N2H4 and HClO through different fluorescence channels without signal crosstalk. PTZ-BA possessed good selectivity, low detection limits, dramatic emission wavelength shift, short response time for the detection of N2H4 and HClO. PTZ-BA could be employed for the quantitative analysis of N2H4 and HClO in environmental soil and water samples, respectively. Furthermore, the functionalized nanofiber membranes and hydrogels were readily fabricated using this probe, enabling the portable on-site detection of gaseous N2H4 and HClO with the help of smartphone. PTZ-BA could achieve the real-time tracking of N2H4 and HClO in HeLa cells, onion cells and zebrafish. This research offers a versatile fluorescence detection platform for N2H4 and HClO, holding a significant potential for environmental analysis and public health monitoring.

Synthesis, photophysical, linear, and non-linear optical properties of 4-methoxyphenyl dicyanovinylene dyes: DFT and TD-DFT studies

Dyes were synthesized via Knoevenagel condensation using various aldehydes of julolidine, n-hexylcarbazole, n-hexylphenothiazine, triphenylamine, and 7-N, N-diethylaminocoumarin named as MB1, MB2, MB3, MB4, and MB5. The dyes were characterized using FT-IR, 1H NMR, 13C NMR, and HRMS, which provided detailed structural information. Significant absorption, emission, and Stokes shift properties were observed through spectroscopic analysis. Notably, MB2, MB3, and MB4 exhibited solid-state and aggregation-induced emission (AIE) properties. MB1, MB3, and MB4 showed high viscosity sensitivity in polar solvents. Dyes containing nitrogen donors (MB1, MB2, and MB3) demonstrated acidochromism, responding to trifluoroacetic acid, while MB4 and MB5 remained neutral. Solvatochromic analysis indicated enhanced hyperpolarizabilities (αCT, βCT and γCT) in polar solvents, with MB1 exhibiting the highest linear and second-order hyperpolarizability, making it ideal for non-linear optical (NLO) applications. MB5 also showed a notable solvent polarity response. Computational studies using B3LYP and CAM-B3LYP functionals confirmed increased hyperpolarizabilities in polar environments. All dyes displayed solvatochromism and promising NLO properties, with MB3 and MB5 showing lower band gaps and higher dipole moments in polar solvents, indicating their potential for photonics, bioimaging, and sensors.

Organoplatinum Complex Exhibiting Aggregation-Enhanced Emission (AEE) and Dual-Channel Ion-Sensing Properties by Terminating the Molecular Configuration Transformation (MCT) and Excited-State Intramolecular Proton Transfer (ESIPT)

Emitters produce weak emissions when they undergo structural changes such as molecular configuration transformation (MCT) or excited-state intramolecular proton transfer (ESIPT) but give out strong emissions after terminating these distortions. Herein, an organoplatinum complex, Pt-ppy-ABP, carrying a salicylaldehyde-based Schiff base unit is synthesized. It exhibits weak emission in dilute solutions but shows bright emission at the aggregated state or after interacting with F- and Zn2+. This suggests that it has an aggregation-enhanced emission (AEE) property and holds potential in ion detection. Supported by theoretical calculations and femtosecond transient absorption results, this complex suffers excited-state structural changes including MCT from a square-planar configuration to a tetrahedral one, as well as intramolecular rotation of a monodentate ligand and ESIPT, showing weak emission in its solutions. At the aggregated state, it releases strong yellow emissions because of the restraints of MCT and ligand rotation. Upon interacting with F- or Zn2+, it emits bright-red or -green emissions, achieving detection limits of 10-7 M. The sensing mechanism is concluded as deprotonation- and coordination-induced ESIPT terminations, respectively. Given its AEE property and ion-responsive emissions, its application in information encryption is also explored. Finally, these findings should provide valuable clues for the developments of chemosensors with dual-channel recognition abilities.

Ratiometric fluorescence-based and chromogenic sensors for the detection of fluoride ions and their application in real samples

This review focuses on the results of synthetic ratiometric fluorescent and colorimetric probes, which have been applied to qualitatively and quantitatively detect fluoride anions in cells, living organisms, and real samples. Primary attention is given to progress made in the working mechanism and applications of these probes to detect fluoride ions in living systems. In addition, design strategies and detection limit for these probes are discussed. This review aims to deliver a comprehensive compilation of the examples reported from 2005 to 2021 on the developments of ratiometric chromogenic and fluorogenic chemosensors for fluoride anions. A total of 20 different ratiometric/colorimetric sensors have been selected for the novelty in their design, sensitivity, detection limit, dynamic range, and speed of detection based on the three fundamental principles of F- ion detection, namely Si-O bond cleavage; excimer emission; and intramolecular charge transfer emission through the B-F monomer, B-F-B bridged dimers, and deprotonation of the amide N-H. Special emphasis has been given to categorize the fluorophores that work in aqueous media, and possible strategies that might be adopted to design green sensors are discussed. Finally, a tabular summary of the comparative studies of all the sensors based on their sensitivity, detection limit, working solvent, and applications is provided. This extensive review may expedite improvements in the development of advanced fluorescent probes for vast and stimulating applications in the future.

One-dimensional Europium-coordination polymer as luminescent sensor for highly selective and sensitive detection of 2,4,6-trinitrophenol

Three isostructural lanthanide coordination polymers (LnCPs), [Ln(L)₆(DMF)]_n {HL = 2-(2-formylphenoxy) acetic acid, Ln = Sm (1); Eu (2); Tb (3)} have been synthesized by solvothermal reaction and characterized. Single crystal analyses revealed that the architectures of these LnCPs own one dimensional chain which can be further packed into two-dimensional architectures by hydrogen bonds. Moreover, these LnCPs can offer strategically placed uncoordinated formyl groups, which may act as hydrogen-bond acceptor in the sensing of nitro explosives. Luminescence measurements reveal that LnCPs 2 and 3 exhibit strong luminescence in solid states. LnCP 2 shows quick, highly selective and sensitive detection of 2,4,6-trinitrophenol (TNP) with the high quenching constant (2.6 × 10⁴ M^-1) and low detection limit (3.39 μM), which indicates that LnCP 2 is more efficient than most of Eu-based coordination polymers for the sensing of TNP. Furthermore, LnCP 2 represents the first example of one-dimensional Eu-based sensors with formyl group as hydrogen-bonding site in the detection of TNP.

Imidazopyridine–fluoride interaction: solvent-switched AIE effects via S⋯O conformational locking

Imidazopyridine-based carboxamide exhibiting the aggregation-induced emission phenomenon works effectively in fluoride ion detection through H-bond interaction and subsequent deprotonation.

Hexaphenylbenzene-based fluorescent probes for the detection of fluoride ions

Novel hexaphenylbenzene derivatives (HPB-1 and HPB-2) were synthesized and their sensing abilities were investigated.

A novel AIE fluorescent probe based on myrtenal for Cu2+ detection in a near-perfect aqueous medium and bioimaging in vegetables and zebrafish

An AIE-active fluorescent probe MHTS with good sensitivity and selectivity for the detection of Cu2+ was synthesized from myrtenal.