Binol diuryl dipyrene fluorescent probe: Dual detection of silver and carbonate ions and its bioimaging applications

Molecular recognition of carbonate ion using a novel turn-on fluorescent probe

A novel turn-on fluorescent probe 3 was synthesized by condensing salicylaldehyde and nicotinic hydrazide for the selective detection of CO32- in aqueous medium. Probe 3 exhibited a turn-on fluorescence response toward CO32- with excellent selectivity, sensitivity (DL = 2.76 μM), and good reversibility. The binding constant (K) of probe 3 with CO32- was calculated to be 5 × 103 M-1 (log K 3.69). The 1:1 stoichiometry of the complex between probe 3 and CO32- ions was confirmed by Job's plot and ESI-MS spectra. Deprotonation and hydrogen-bonding interactions are involved in the recognition of CO32- ion, which was also suggested by 1H NMR, ESI-MS spectra, and Density Functional Theory (DFT) calculations. Moreover, an INHIBIT type molecular logic gate was constructed by using 3:CO32- and CH3COOH as inputs and current signal as output. Owing to the practical applications, probe 3 demonstrated its efficiency in quantifying CO32- ion in real water samples through standard addition method, thus showcasing its potential in real environment. Further, the MTT assay indicated very low cytotoxicity (IC50 = 1 mM) of probe 3 and also the cell imaging experiments demonstrated the effective sensing of CO32- ions with probe 3 in the biological systems.

Recent Advances in Organic Sensors for the Detection of Ag+ Ions: A Comprehensive Review (2019-2023)

Recently, organic sensors for the detection of Ag+ and other metal ions have experienced significant advancements. This is because there is a growing demand for reliable and sensitive tools to monitor various environmental pollutants. Organic sensors have O-, S-, and N-donor atoms, which can act as a ligand and coordinate with different metal ions, hence stabilizing them in a variety of oxidation states. This interaction gives colorimetric and fluorescence changes, which are used to monitor Ag+ and other metal ions. This comprehensive review highlights the latest developments in organic sensors for the recognition of Ag+. We present an in-depth analysis of the underlying principles and mechanisms governing Ag+ ion recognition. Various organic sensing platforms, such as fluorescent and colorimetric sensors, are discussed, shedding light on their unique advantages and limitations. Special attention is given to the diverse range of organic ligands, receptors, and functional materials used to achieve high sensitivity, selectivity, and quantification accuracy. Additionally, we delve into real-world applications of organic sensors for Ag+ ion detection, examining their performance in complex matrices such as biological, environmental, industrial and agricultural matrices.

Multifunctional Zn(II) Coordination Polymer as Highly Selective Fluorescent Sensor and Adsorbent for Dyes

A new Zn(II)-based coordination polymer (1) comprising the Schiff base ligand obtained by the condensation of 5-aminosalicylic acid and salicylaldehyde has been synthesized. This newly synthesized compound has been characterized by analytical and spectroscopic methods, and finally, by single-crystal X-ray diffraction technique in this study. The X-ray analysis reveals a distorted tetrahedral environment around the central Zn(II) center. This compound has been used as a sensitive and selective fluorescent sensor for acetone and Ag⁺ cations. The photoluminescence measurements indicate that in the presence of acetone, the emission intensity of 1 displays quenching at room temperature. However, other organic solvents caused meagre changes in the emission intensity of 1. Additionally, the fluorescence intensity of 1 has been examined in the presence of different ketones viz. cyclohexanone, 4-heptanone, and 5-nonanone, to assess the interaction between the C=O group of the ketones and the molecular framework of 1. Moreover, 1 displays a selective recognition of Ag⁺ in the aqueous medium by an enhancement in its fluorescence intensity, representing its high sensitivity for the detection of Ag⁺ ions in a water sample. Additionally, 1 displays the selective adsorption of cationic dyes (methylene blue and rhodamine B). Hence, 1 showcases its potential as an excellent luminescent probe to detect acetone, other ketones, and Ag⁺ with an exceptional selectivity, and displaying a selective adsorption of cationic dye molecules.

Anthracene benzene conjugate (ABC): An asymmetric Schiff base for the selective detection of Ag+ ion using fluorimetry and its applications

Anthracene based chemosensor ABC has been synthesized and characterized through ¹H, ¹³C NMR, mass spectral studies. UV absorption and emission studies performed to identify the sensing behavior of chemosensor ABC. The probe ABC, originally bright fluorescent, selectively sense Ag⁺ ion by the quenching the fluorescence intensity through a "Switch On-off" process and quench the fluorescence due to the heavy atom effect interaction with the free chemosensor. The binding constant of the probe ABC with Ag⁺ was calculated as 5.4 × 10⁴ M^-1 and the limit of detection upto 1.4 nM level. The practical utilization of the probe ABC was demonstrated by applying to the real water and soil sample analysis, latent finger print, and the sensor as a fluorescent ink.

Positional Isomeric Symmetric Dipodal Receptors Dangled with Rotatable Binding Scaffolds: Fluorescent Sensing of Silver Ions and Sequential Detection of l-Histidine and Their Multifarious Applications

Three simple dipodal artificial acyclic symmetric receptors, SDO, SDM, and SDP, driven by positional isomerism based on xylelene scaffolds were designed, synthesized, and characterized by ¹H NMR, ¹³C NMR, and mass spectroscopy techniques. Probes SDO, SDM, and SDP demonstrated selective detection of Ag⁺ metal ions and amino acid l-histidine in a DMSO-H₂O solution (1:1 v/v, HEPES 50 mM, pH = 7.4). The detection of Ag⁺ metal ions occurred in three ways: (i) inhibition of the photoinduced electron-transfer (PET) process, (ii) blueshifted fluorescence enhancement via the intramolecular charge-transfer (ICT) process, and (iii) restricted rotation of the dangling benzylic scaffold following coordination with a Ag⁺ metal ion. Job's plot analysis and quantum yields confirm the binding of probes to Ag⁺ in 1:1, 1:2, and 1:2 ratios with LODs and LOQs found to be 1.3 μM and 3.19 × 10^-7 M, 6.40 × 10^-7 and 2.44 × 10 ^-6 M, and 9.76 × 10^-7 and 21.01 × 10^-7 M, respectively. ¹H NMR titration, HRMS, ESI-TOF, IR analysis, and theoretical DFT investigations were also used to establish the binding stoichiometry. Furthermore, the probes were utilized for the detection of Ag⁺ ions in water samples, food samples, soil analysis, and bacterial imaging in Escherichia coli cells and a molecular logic gate was constructed.

A photoswitchable "turn-on" fluorescent chemosensor: Quinoline-naphthalene duo for nanomolar detection of aluminum and bisulfite ions and its multifarious applications

A quinoline-naphthalene duo-based Schiff base probe (R) was synthesized and characterized by the usual spectroscopic and single-crystal X-ray crystallographic techniques. Probe R detects Al³⁺ and HSO₃^- ions via the fluorescent turn-on approach by dual pathways i.e., i) when probe R interacts with Al³⁺, the restriction of CN single bond rotation, blocking of both photoinduced electron transfer (PET) and CN isomerization were observed, and ii) when the sensor R interacts with HSO₃^-, imine (CH = N) bond was cleaved via hydrolysis and produced the respective aldehyde and amine behaving as a chemodosimeter. The binding stoichiometric ratio of R + Al³⁺ (1:1) was confirmed by Job's plot, emission titration profile, NMR, and mass spectrometric analyses. This probe R is highly selective to both Al³⁺ -ions and HSO₃^- -ions, without any interference of other potentially competing cations and anions. Limit of detection (LOD) and quantification (LOQ) of R with Al³⁺ and HSO₃^- were downed to nanomolar concentrations, which is much lower than the recommended level of drinking water/food fixed by the World Health Organization (WHO). Furthermore, probe R was utilized in the detection of Al³⁺ and HSO₃^- ions in highly contaminated real samples, bioimaging in E. coli cells, multiple-targeting molecular logic gate, and in bovine serum albumin (BSA) binding.

Graphene oxide-rhodamine nanocomposite for picomolar detection of chromium(III) by fluorimetry and its biofilm inhibition

Graphene oxide-rhodamine B hydrazide (GO-RhB) nanocomposite was prepared by a simple chemical method and characterized by various spectroscopic and analytical techniques. GO-RhB nanocomposite potentially detects Cr³⁺ ion (excitation/emission = 550 nm/572 nm) via fluorescence turn "on-off" approach. This composite showed high binding affinity (10⁶ M^-1) with Cr³⁺ and a+ limit of detection (LOD) down to picomolar concentration (LOD = 85.6 pM). As far as we know, this is the first report for the sensing of Cr³⁺ ion at picomolar concentration. GO-RhB selectively senses Cr³⁺ ion without any interference of other coexisting metal ions. In addition, this composite exhibited the dynamic nature of quenching in the presence of Cr³⁺ ion, which is confirmed by the Stern-Volmer plot, fluorescence temperature profiles, and decay time experiments. The GO-RhB nanocomposite-based fluorescent probe was successfully applied to the quantitative detection of Cr³⁺ ion in milk sample (linear range = 2 to 10 nM) with better performance than other existing methods. Besides, this GO-RhB composite showed better antibiofilm activity against Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus (MRSA) by using the Congo red agar and tube method.

Fabrication and sensing properties of phenolphthalein based colorimetric and turn-on fluorogenic probe for CO32- detection and its living-cell imaging application

Herein, an easy assembled colorimetric and ''turn-on'' fluorescent sensor (probe P4SC) based on phenolphthalein was developed for carbonate ion (CO₃^2-) sensing in a mixture of EtOH/H₂O (v/v, 80/20, pH = 7, Britton-Robinson buffer) media. The probe P4SC demonstrated high sensitive and selective monitoring toward CO₃^2- over other competitive anions. Interaction of CO₃^2- with the probe P4SC resulted in a significant increment in emission intensity at λ_em = 498 nm (λ_ex = 384 nm) due to the strategy of blocking the photo induced electron transfer (PET) mechanism. ¹H NMR titration and Job's methods, as well as the theoretical study were carried out to support the probable stoichiometry of the reaction (1:2) between P4SC and CO₃^2-. The binding constant of the probe P4SC with CO₃^2- was calculated as 2.56 × 10¹⁰ M^-2. The probe P4SC providing rapid response time (~0.5 min) with a satisfactorily low detection limit (14.7 nM) may be useful as a valuable realistic sensor. The imaging studies on the liver cancer cells (HepG2) shows the great potential of the probe P4SC for the sensation of intracellular CO₃^2- anions. Furthermore, the satisfactory recovery and RSD values obtained for water application confirming that the probe P4SC could be applied to sensing of CO₃^2- ion.

A novel voltammetric method for the sensitive and selective determination of carbonate or bicarbonate ions by an azomethine-H probe

Our study involved a simple, sensitive voltammetric method of determining either carbonate or bicarbonate ions independently with azomethine-H and a disposable pencil graphite electrode. The reduction of azomethine-H-carbonate complexes at approximately -930 mV formed in acetic acid-acetate buffer solution (pH: 4.25) was evaluated as a response. Among the results, the limits of detection and analytical ranges for carbonate ions were 3.7 μg L^-1 and 9.9-700.0 μg L^-1 and for bicarbonate ions were 9.0 μg L^-1 and 35.0-700.0 μg L^-1, and the relative standard deviations for carbonate and bicarbonate ions ranged from 1.33% and 6.93% at different concentrations. After the proposed method was applied to water, sparkling water, seawater and baking powder samples, the results were statistically evaluated and compared with those obtained from the potentiometric auto-titration system. Last, the complex stoichiometry of both carbonate and bicarbonate ions was comprehensively investigated with fluorescence and ¹H-NMR spectroscopy.

Triphenyl-imidazole based reversible coloro/fluorimetric sensing and electrochemical removal of Cu2+ ions using capacitive deionization and molecular logic gates

A simple hydroxyl-substituted triphenyl-imidazole based receptor (HTPI) which selectively detects Cu²⁺ ion by colorimetric and fluorimetric methods was developed. HTPI detects the Cu²⁺ ions with the absorption enhancement and fluorescence quenching by the possible ligand to metal charge transfer (LMCT) and the chelation-enhanced quenching (CHEQ) approaches, respectively. HTPI showed high selectivity and sensitivity for Cu²⁺ ions detection over other interfering and competing metal ions. Interestingly, HTPI detects Cu²⁺ ion (LOD) at nanomolar concentrations (19 × 10^-9 M (UV-vis) & 27 × 10^-9 M (fluorescence), respectively), which is lower than the permissible level of Cu²⁺ ion reported by World Health Organization (WHO). Furthermore, HTPI was applied to the molecular logic gate function by using chemical inputs, and Cu²⁺ ion was potentially removed (95%) via Capacitive Deionization technique.

Lansoprazole-Based Colorimetric Chemosensor for Efficient Binding and Sensing of Carbonate Ion: Spectroscopy and DFT Studies

The new benzimidazole based receptor Lansoprazole has been used to detect carbonate anion by naked-eye and Uv-Vis spectroscopy. This receptor revealed visual changes withCO 3 2 - anion in ethanol. No detectable color changes were observed upon the addition of any other tested anions. The lansoprazole chemosensor selectively recognizesCO 3 2 - ion over the other interference anions in the ethanol, followed by deprotonation and reflected 1:1 complex formation between the receptor and the carbonate ion. Lansoprazole exhibits splendid selectivity toward carbonate ion via a visible color change from colorless to yellow with a detection limit of 57 μM. The binding mode ofCO 3 2 - to receptor L is supported by Density Functional Theory calculation. Moreover, this receptor shows a practical visible colorimetric test strip for the detection of carbonate ions. The transition states calculation demonstrates the occurrence of reaction from L to L-CO 3 2 - after overcoming an energy barrier of 10.1 kcal/mol, and there is considerable interaction energy between L andCO 3 2 - (94.9 kJ/mol), both of which confirmed that receptor L has high sensitivity and selectivity to the carbonate ion. The theoretical studies were performed to acquire an electronic description of the complexation mechanism byCO 3 2 - as well as to study bonding and structure in the complex. The optimized structures and binding mechanisms were supported with a high correlation and agreement by spectroscopy and DFT calculations.

Quinoline based reversible fluorescent probe for Pb2+; applications in milk, bioimaging and INHIBIT molecular logic gate

We report the modular design and synthesis of an amine dangled Schiff base quinoline-morpholine conjugate (QMC) for highly selective detection of Pb²⁺ ions via fluorimetry. The sensing strategy of QMC towards Pb²⁺ ion exhibits a large blue shift with fluorescent enhancement via the intramolecular charge transfer (ICT) process. At the same time, QMC coordination with Pb²⁺, the CN single bond rotation between quinoline and morpholine rings and the CN isomerization process were blocked. Best of our knowledge, this is the first blue shifted turn-on fluorescent chemosensor for Pb²⁺ ion via the ICT process. Furthermore, QMC selectively detects Pb²⁺ ion without any interference with alkali, alkaline earth, and transition metal ions, and limit of detection (LOD) downs to 13 μM, which is a permissible level of Pb²⁺ ion in drinking water reported by WHO. The 1:2 binding stoichiometry between QMC and Pb²⁺ was confirmed by fluorimetric, ¹H NMR titration, mass spectrometry, and theoretical studies. Finally, QMC was potentially applied for the sensing of Pb²⁺ ions in milk, red wine, live cells and an INHIBIT molecular logic function was constructed by using Pb²⁺ and EDTA as chemical inputs.