Specific colorimetric detection of Fe3+ ions in aqueous solution by squaraine-based chemosensor

Exploration of NIR Squaraine Contrast Agents Containing Various Heterocycles: Synthesis, Optical Properties and Applications

Squaraine dye is a popular class of contrast near-infrared (NIR) dyes. Squaraine dyes have shown the ability to be modified with various heterocycles. The indole moiety is the most notable heterocycle incorporated in squaraine dyes. A tremendous amount of work has gone into developing indole-based squaraine dyes and determining their applications. The optical properties of squaraine dyes containing an indole moiety facilitate high quantum yields and molar absorptivity, but the absorbance maxima is capped near 700 nm. This is the major limitation of indole-based squaraine dyes. In comparison, other heterocycles with larger conjugated systems such as quinoline and perimidine have demonstrated promising optical properties and immense potential for modifications, albeit with limited development. Quinoline- and perimidine-based squaraine dyes have molar extinction coefficients over 100,000 M-1 cm-1 and absorbances over 800 nm. This report will look at indole-, quinoline-, and perimidine-based squaraine dyes. Due to the sheer number of reported dyes, the search for indole-based squaraine dyes has been limited to reports from the past five years (2018-2023). For quinoline- and perimidine-based squaraine dyes, a holistic search was performed to analyze the optical properties and applications, due to the abovementioned limitation. This report will evaluate the three different classes of squaraines: indole-, quinoline-, and perimidine-based, to evaluate their optical properties and applications, with the goal of encouraging the exploration of other heterocycles for use in squaraine dyes.

Development of highly selective fluorescent ferrocenyl-iminopyridine chemosensor for biologically relevant Fe3

Design, synthesis, characterization, and ion detection studies of two ferrocene-appended Schiff bases namely N-(2-[ferrocenylamino]ethyl)-5-nitropyridin-2-amine (1) and ferrocenylamino-1H-imidazole-4-carboxamide (2) been reported. Both the chemosensors have been thoroughly characterized using Fourier transfer infrared, 1 H and 13 C nuclear magnetic resonance, high resolution mass spectrometry, and ultraviolet/visible (UV/visible) and fluorescence spectral techniques. Probes 1 and 2 were designed with the aim of appending the ferrocenyl group with pyridine ring having an amine substitution (for 1) and imidazole ring with an amide substitution (for 2). Interaction of these probes with a series of cations and anions was examined through UV/vis and fluorescence spectral techniques. Probe 2 exhibited an insignificant response towards anions and loss of selectivity for cations, whereas 1 displayed highly selective detection towards biologically important Fe3+ in 2:1 (probe:cation) stoichiometry. Notably, none of the cations and anions could interfere the selectivity of Fe3+ ensured by 1 in aqueous medium. The limit of detection for Fe3+ detection using 1 was determined to be 0.2 ppm. The results strongly suggest that 1 could find promising future application as a chemosensor for Fe3+ in biological systems for quantification and qualitative analysis.

Fluorescence determination of Fe(iii) in drinking water using a new fluorescence chemosensor

A new fluorescence chemosensor based on (Z)-2-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene)hydrazine-1-carbothioamide (CEHC) has been developed for the determination of Fe(iii) in drinking water. The optimum conditions were acetate buffer solution with a pH 5.0. In this approach, the determination of Fe(iii) is based on static quenching of the luminescence of the probe upon increasing concentrations of Fe(iii). The CEHC sensor binds Fe(iii) in a 1 : 1 stoichiometry with a binding constant K_a = 1.30 × 10⁴ M⁻¹. CEHC responds to Fe(iii) in a way that is more sensitive, selective, and quick to turn off the fluorescence than to other heavy metal ions. Selectivity was proved against seven other metal ions (Mn(ii), Al(iii), Cu(ii), Ni(ii), Zn(ii), Pb(ii), and Cd(ii)). The calibration curve was constructed based on the Stern–Volmer equation. The linear range was 2.50–150 μM with the correlation coefficient of 0.9994, and the LOD was 0.76 μM. The method was successfully applied to determine Fe(iii) in drinking water samples, and the accuracy of the chemosensor was validated by atomic absorption spectrometry.

A new fluorescence chemosensor based on (Z)-2-(1-(3-oxo-3H-benzo[f]chromen-2-yl)ethylidene)hydrazine-1-carbothioamide (CEHC) has been developed for the determination of the fluorescence probe of Fe(iii) in drinking water.

Recent progress in the development of highly active dyeing photoinitiators based on 1,3-bis(p-substituted phenylamino)squaraines for radical polymerization of acrylates

The photopolymerization is a very popular technique used in the production of various polymeric materials. The key role in the light induced polymerization processes plays a photoinitiator. One of the...

Impacts of aluminum- and iron-based coagulants on municipal sludge anaerobic digestibility, dewaterability, and odor emission

Although aluminum- and iron-based chemicals have been broadly used as the two most common types of coagulants for wastewater treatment, their impacts on the performance of downstream sludge management can be quite different and have not been well understood. This work reviewed and analyzed their similarities and differences in the context of the anaerobic digestion performance, dewaterability of digested sludge, and odor emission from dewatered biosolids. In short, iron-based coagulants tend to show less negative impact than aluminum-based coagulants. This can be attributed to the reduction of ferric to ferrous ions in the course of anaerobic digestion, which leads to a suite of changes in protein bioavailability, alkalinity and hydrogen sulfide levels, and in turn the sludge dewaterability and odor potential. Whether these observations still hold true in the context of thermally hydrolyzed sludge management remains to be studied. PRACTITIONER POINTS: The impacts of aluminum-/iron-based coagulant addition on municipal sludge anaerobic digestibility, dewaterability, and odor emission are reviewed. Iron-based coagulants show less negative impact on the sludge digestibility than aluminum-based coagulants. Conclusions may aid practitioners in selecting coagulants in practice and better understanding the mechanisms behind the phenomena.

A Deferasirox Derivative That Acts as a Multifaceted Platform for the Detection and Quantification of Fe3+

Here, we report that ExSO3H, a synthetically accessible, water-soluble, non-toxic derivative of the clinical iron chelator deferasirox, acts as a colorimetric chemosensor that permits the detection and quantification of Fe3+ in aqueous samples at pH 2–5. In addition, we observed that a fluorescent turn-on response was produced when this chelator was allowed to interact with human serum albumin (HSA). This fluorescence was quenched in the presence of Fe3+, thus allowing us to monitor the presence of this biologically important metal cation via two independent methods.

Rational design and bioimaging application of water-soluble Fe3+ fluorescent probes

The carboxyl group improves the water-solubility of Fe³⁺ fluorescent probes, while resulting in different performances based on its position.

Case study on the use of image analysis for the simple and inexpensive colorimetric detection of Fe(iii) in water

In the present work, we have reported a simple and cost effective colorimetric method for the detection of Fe(iii) in water. The method is based on the color change through the formation of an Fe(iii)-glycine complex at room temperature. This type of complex formation produces an intense color due to the ligand to metal charge transfer (LMCT). The rate of this type of complex formation depends appreciably on the Fe(iii) concentrations. An important aspect of the present work is that here the image analysis technique has been used successfully for the discrimination of the color obtained by the variation of the Fe(iii) concentration. The fundamental spectro-photochemical studies on the colorimetric detection of Fe(iii) by forming a metal ligand complex and thereafter the discrimination of the complex through image analysis can provide effective insight into the development of cost effective devices for the detection of liquid phase analytes.

Furo[3,2-c]coumarin-derived Fe3+ Selective Fluorescence Sensor: Synthesis, Fluorescence Study and Application to Water Analysis

Furocoumarin (furo[3,2-c]coumarin) derivatives have been synthesized from single step, high yielding (82-92%) chemistry involving a 4-hydroxycoumarin 4 + 1 cycloaddition reaction. They are characterized by FTIR, 1H-NMR, and, for the first time, a comprehensive UV-Vis and fluorescence spectroscopy study has been carried out to determine if these compounds can serve as useful sensors. Based on the fluorescence data, the most promising furocoumarin derivative (2-(cyclohexylamino)-3-phenyl-4H-furo[3,2-c]chromen-4-one, FH), exhibits strong fluorescence (ФF = 0.48) with long fluorescence lifetime (5.6 ns) and large Stokes' shift, suggesting FH could be used as a novel fluorescent chemosensor. FH exhibits a highly selective, sensitive and instant turn-off fluorescence response to Fe3+ over other metal ions which was attributed to a charge transfer mechanism. Selectivity was demonstrated against 13 other competing metal ions (Na+, K+, Mg2+, Ca2+, Mn2+, Fe2+, Al3+, Ni2+, Cu2+, Zn2+, Co2+, Pb2+ and Ru3+) and aqueous compatibility was demonstrated in 10% MeOH-H2O solution. The FH sensor coordinates Fe3+ in a 1:2 stoichiometry with a binding constant, Ka = 5.25 × 103 M-1. This novel sensor has a limit of detection of 1.93 µM, below that of the US environmental protection agency guidelines (5.37 µM), with a linear dynamic range of ~28 (~2-30 µM) and an R2 value of 0.9975. As an exemplar application we demonstrate the potential of this sensor for the rapid measurement of Fe3+ in mineral and tap water samples demonstrating the real-world application of FH as a "turn off" fluorescence sensor.

Synthesis and Antibacterial Activity of Rhodanine-Based Azo Dyes and Their Use as Spectrophotometric Chemosensor for Fe3+ Ions

This research includes the design and synthesis of new derivatives for rhodanine azo compounds (4a–c) containing a naphthalene ring. Physiochemical properties of the synthesized compounds were determined by their melting points, FTIR, 1H-NMR, 13C-NMR, and elemental analysis spectroscopic techniques. The biological activities of the newly prepared azo rhodanine compounds were evaluated against some pathogenic bacteria using three different bacterial species including (Escherichia coli., Pseudomonas aeruginosa, Staphylococcus aureus) and compared with amoxicillin as a reference drug. The results showed that our compounds have moderate-to-good vital activity against the mentioned pathogenic bacteria. The selectivity and sensitivity of the newly prepared rhodanine azo compounds with transition metals Co2+, Cu2+, Zn2+, Ni2+, and Fe3+ were studied using UV–vis and fluorescence spectroscopy techniques. Among the synthesized azos, azo 4c showed affinity toward Fe3+ ions with an association constant of 4.63 × 108 M−1. Furthermore, this azo showed high sensitivity toward Fe3+ ions with detection limits of 5.14 µM. The molar ratio and Benesi–Hildebrand methods confirmed the formation of complexes between azo 4c and Fe3+ with 1:2 binding stoichiometry. Therefore, azo 4c showed excellent potential for developing efficient Fe3+ chemosensors.