Job's Plot Research Articles

Spectroscopic Rationalization of Selective Colorimetric Chemosensing of Fe(lll) in Aqueous Medium by a New Mono-Substituted Dibenzodiaza-Crown Ether Macrocyclic Ligand Appended with Mono 2-Benzimidazole N-Pendant Side Arm.

Optical chemosensor L comprising of a new mono-N-substituted derivative of dibenzodiaza-crown ether macrocyclic ligand bearing a 2-benzimidazole (2Bim) side arm was synthesized, and characterized by FT-IR, elemental microanalyses, 1H NMR, and 13C NMR, UV-visible, fluorescence (FL) spectroscopy. The colorimetric chemosensing behavior of L toward the library metal ions was examined, wherein L represented a prompt and selective yellow-to-purple color change for Fe(III) cation in a 25µM solution with LOD as 0.23 µM in ethanol:water (9:1, v/v), even in the presence of the other library metal ions (LMI). Based on the 1H NMR, UV-visible, and FL observations the coordination sphere of Fe(III) was shared with two 2-benzoimidazole (2Bim) side arms which were also confirmed by the elemental microanalyses (in the solid state) and the Job plot method (in the solution) of the complex. Moreover, the above-mentioned color change was attributed to the presence of a strong charge transfer (LMCT) band for the Fe(III)/L interaction in the solution. Furthermore, the viscosity measurement in the presence of Fe(III) uncovered an increase at 0.5-1.0 ratios for Fe(III)/L, attributable to the formation of a self-assembly in the solution. A TLC paper strip was impregnated by L for selective detection of Fe(III), demonstrating a live color change for Fe(III) at 0-5 mM in the presence of LMI.

A Simple and Rapid Quinoline Schiff Base as a Fluorescent Probe for Zn2+ and Its Application in Test Strips

AbstractA simple fluorescent probe, (E)‐N‐(3‐methoxy‐4‐methylphenyl)‐1‐(quinolin‐2‐yl)methanimine (L), was synthesized via Schiff base condensation reaction between quinoline‐2‐carboxaldehyde and 3‐methoxy‐4‐methylaniline. L can be used as a ′turn‐on′ fluorescent probe for the selective and sensitive detection of Zn2+ ions in a CH3OH/HEPES medium. The detection limit was 1.04×10−7 M. Job plot analysis shows that the binding stoichiometry of L and Zn2+ is 1 : 1, further verified by the single crystal structure. The fluorescence‐enhanced response of L towards Zn2+ ions may be related to the chelation‐enhanced fluorescence (CHEF) supported by theoretical calculations. By adding EDTA, the reversibility of the probe binding to Zn2+ ions is demonstrated, enabling the construction of a functional molecular logic circuit. In addition, probe L was successfully incorporated into test strips for the quantitative detection of Zn2+.

Anticounterfeiting Feature of a Writable and Self-Erasable Ni(II)-Metallogel Pad via Fluorescent "Turn-On" Detection of Cyanide.

A Schiff base 5-(2-hydroxy-3-methoxybenzylidieneamino)-1-H-imidazole-4-carboxamide (HL) comprising multibinding sites has been synthesized with the aim of fabricating a supramolecular gel. The gelator HL was characterized by FT-IR, 1H & 13C NMR, and ESI-MS techniques and also formed a [Ni(L)2] complex. The gelation property of HL was investigated with various metal ions, wherein Ni(II) selectively forms a mechanically and thermally stable supramolecular metallogel (MG) in the presence of a triethylamine base in DMF-MeOH media. Characterization of MG was accomplished with different spectro-analytical techniques such as FT-IR, ESI-MS, powder-XRD, SEM, rheological investigations, UV/vis, and fluorescence. The gelator HL displays moderate emission upon addition of Ni2+ and gives "turn-off" fluorescence output by forming the complex [Ni(L)2] (MG) due to the chelation-enhanced quenching of fluorescence (CHEQ). Job plot and ESI-MS data suggested a 2:1 stoichiometry between HL and Ni(II) in MG. Further, MG exhibited highly selective and ultrasensitive "turn-on" fluorescence signaling with CN- in the background presence of several cations and anions. The limit of detection (LoD) of MG was determined to be 6.9 × 10-9 M for CN- using the fluorescence technique. Notably, MG behaves as a fluorescent writable pad material explicitly with CN- under 365 nm UV light but not under ordinary light and the fluorescent text is self-erased after 15 min. Hence, MG can be used as a metallogel pad in the presence of CN- to communicate secret messages. Overall, the present work explores the fabrication of a thermo- and mechanostable Ni(II)-metallogel (MG), which selectively and ultrasensitively detects CN- both in the solution phase and in the gel form, wherein MG behaves as a writable and self-erasable pad with anticounterfeiting features for practical applications.

A novel “on−off−on” fluorescent probe with high selectivity for continuous identification of Cu2+ and S2− and its applications

A BODIPY-derived fluorescent probe (B-2) was developed to recognize Cu2+ and S2− sequentially in the CH3CN/HEPES (7:3 v/v, pH=7.27) buffer solution. After Cu2+ was added, the fluorescence was quenched, where the quenching rate was 95.3 %, and the detection limit was 0.36 μmol/L. The binding mechanism between B-2 and Cu2+ was elucidated using IR spectra, 1H NMR titration, DFT study, and Job's plot analysis. The complex B-2-Cu2+ formed from B-2 and Cu2+ could continuously recognize S2−, where the recovery rate was 90.6 %, and the detection limit was 0.01 μmol/L. In the pH range of 3∼9, probe B-2 had a high recognition ability for Cu2+ and S2−, which could be recycled four times. Furthermore, a cheap medical cotton swab can confirm that probe B-2 can continuously detect Cu2+ and S2−. Meanwhile, the applicability of B-2 for Cu2+ detection was verified in actual water samples with good precision and accuracy.

Functionalized 2-Hydrazinobenzothiazole with Bithiophene as a Colorimetric Sensor for Lethal Cyanide Ions and Its Application in Food Samples.

A newly synthesized Schiff's base 2-(2-([2,2'-bithiophen]-5-ylmethylene)hydrazinyl)benzothiazole (BT) was obtained from the condensation reaction between 2-hydrazinobenzothiazole and 2,2-bithiophene-5-carboxaldehyde. The prepared probe BT was subjected to a confirmation of the structural arrangement through NMR, FTIR, ESI-HRMS, and single-crystal XRD spectral analysis. The BT colorimetric sensor showed selectivity and sensitivity toward the cyanide (CN-) ion over other common anions such as ClO4-, Cl-, Br-, F-, I-, NO2-, OH-, HSO4-, and H2PO4- in a partial aqueous system CH3CN/H2O (8:2, v/v). The probe BT detects CN- with the lowest detection range as low as 1.33 × 10-8 M (3.59 ppm); in comparison to that given by WHO guidelines, it is significantly lower. The stoichiometric interaction between the probe BT and analyte CN- was found to be 1:1 (BT/CN-) binding mode using Jobs plot, and further association binding affinity was calculated to be 6.64 × 10-3 M-1. Additionally, these results were further supported by the FTIR and DFT calculations, as well as the 1H NMR titration analysis, which complemented the binding data. The sensor probe BT was successfully employed in a cotton swab test kit approach and also in smartphone-assisted applications for the determination of CN- ions. Finally, the outstanding sensing properties of probe BT aided the quantitative detection of CN- ions, and it could be further applied to a variety of food samples, including apple seeds, sprouting potatoes, and cassava.

Detection of Arsenic(V) by Fluorescence Sensing Based on Chlorin e6-Copper Ion.

The high toxicity of arsenic (As) can cause irreversible harm to the environment and human health. In this study, the chlorin e6 (Ce6), which emits fluorescence in the infrared region, was introduced as the luminescence center, and the addition of copper ion (Cu2+) and As(V) provoked a regular change in fluorescence at 652 nm, whereas that of As(III) was 665 nm, which was used to optionally detect Cu2+, arsenic (As(III), and As(V)). The limit of detection (LOD) values were 0.212 μM, 0.089 ppm, and 1.375 ppb for Cu2+, As(III), and As(V), respectively. The developed method can be used to determine Cu2+ and arsenic in water and soil with good sensitivity and selectivity. The 1:1 stoichiometry of Ce6 with Cu2+ was obtained from the Job plot that was developed from UV-visible spectra. The binding constants for Cu2+ and As(V) were established to be 1.248 × 105 M-1 and 2.35 × 1012 M-2, respectively, using B-H (Benesi-Hildebrand) plots. Fluorescence lifetimes, B-H plots, FT-IR, and 1H-NMR were used to postulate the mechanism of Cu2+ fluorescence quenching and As(V) fluorescence restoration and the interactions of the two ions with the Ce6 molecule.

Chelation of iron(II) ions by ellagitannins—Effects of hexahydroxydiphenoyl and nonahydroxytriphenoyl groups

Tannins represent secondary plant metabolites that are used to control bacterial populations by chelation of essential metal ions. Their presence in food also affects the bioavailability of iron. This study investigates the influence of ellagitannins (vescalin, castalin, vescalagin, castalagin) structure and pH on the stoichiometry and formation constants of ellagitannin-Fe(II) coordination compounds. We demonstrated that ellagitannins are stable for at least one hour at pH values lower than 7.25. The spectra of neutral compounds were measured and explained with the help of TDDFT calculations. Furthermore, the pH-dependence of the ellagitannins UV–Vis spectra was examined to obtain insight into their protolytic equilibrium. Using Job’s method in the pH range 3.50–5.51, the stoichiometry of the formed ellagitannin-Fe(II) ions complexes was determined. A model explaining interactions between ellagitannins and Fe(II) ions, that took into account the protolytic equilibrium of ellagitannins, was fitted globally to all four Job plots, whereby the corresponding formation constants were obtained.

Quinoline-quinoline schiff-base as an effective chromogenic, fluorogenic, and smartphone assisted RGB detection of Pb2+ ion in near aqueous medium

A novel multimode colorimetric and fluorescent chemosensor was developed using an 8-hydroxy quinoline carbaldehyde Schiff base with a quinoline hydrazide probe (E)-2-((2-(quinolin-2-yl)hydrazineylidene)methyl)quinolin-8-ol (L). NMR (1H &13C), FTIR, and HR-mass spectral characterization techniques confirmed the probe L structural conformation. As Probe L contacts Pb2+ ions, a color change and turn-off emission can be visually detected in EtOH:H2O (1:1, v/v, pH = 7.21) medium. The probe displays a good emission at 440 nm due to the combined ESIPT and ICT process. The Pb2+ ion interacts with the probe and selectively quenches fluorescence by inhibiting ESIPT and >CN- isomerization. As per Job's plot, L-Pb2+ complex formation occurred in a 1:1 stoichiometric ratio, with association constant (Ka) and quenching constant (Ksv) estimated at 1.52 × 105 M−1 and 4.12 × 105 M, respectively. The detection limits of Pb2+ by spectrophotometric and spectrofluorometric were 1.99 μM (41 ppb) and 23.4 nM (485 ppt), respectively. Additionally, the test paper kit and RGB tool were used to monitor the color changes of L with Pb2+ and the LOD was found to be 5.99 μM (125 ppb). Its recognition mechanism has been verified by 1H NMR, ESI-mass, and theoretical studies.

Synthesis of hybrid azobenzene-chalcone dyes and studies on their photophysical properties: Molecular recognition of carbonate and phosphate ions using a novel turn-off fluorescent probe

The work presented here describes the synthesis and comparative physiochemical studies of hybrid compounds C-1 to 5 of azobenzene A-1 and chalcone B-1, which exhibited the characteristic of both. Further, electron-withdrawing and donating substituents analogues have also been synthesized. The hybrid compound is unique in nature because it contains the phenolic -OH, -N = N-, as well as α,β-unsaturated enone functional groups. The photophysical properties of hybrid C-1 behaved more or less like the azobenzene moieties and showed the same pattern of UV–vis absorption as with the change in the polarity of the solvent and the change in the pH of the medium. Thus, in the non-polar solvent or in the water medium, the phenol form dominates with its yellow colour and in polar solvents shows an intense red colour of keto form. They show a dramatic quenching of fluorescence emission in the polar solvent. Furthermore, after screening, C-1 was found to show selective sensing of the aqueous CO32− ion as well as minimally with PO43- and show a characteristic colour change in an organic solvent such as CH3CN. A few ions also changed colour in DMF, but that was due to the only shifting of the tautomerization equilibrium from keto to enol form. The UV–vis as well as fluorescent spectral studies, determination of the detection limits, and binding constants illustrated significant sensing of CO32− ions. A systematic study was performed to understand the binding interactions of the chemosensor by using Job's plot and time-dependent 1H NMR studies that supported the involvement of phenoloc -OH and β carbon of α,β-unsaturated system. The characteristic pattern of UV–vis and interaction mode was confirmed by DFT studies. The applicability of chemosensor C-1 was demonstrated by the development of a paper strip model to check the presence of CO32− ions in different kinds of water in society.

A novel isophorone-based NIR fluorescent and colormetric probe for Al3+ sensing and its application for living cells and plants imaging

In this paper, an isophorone-based NIR fluorescent and colormetric probe BDDH for Al3+ was synthesized and characterized, it showed highly selectivity and sensitivity through significant fluorescence enhancement and visible color change towards Al3+. The job plot confirmed that the binding ratio of BDDH with Al3+ was 1:1. Furthermore, the limit of detection (LOD) of Al3+ was determined to be 4.01 × 10−8 M. Moreover, BDDH was successfully applicated in identification of Al3+ in the different water samples, cell imaging in alive MCF-7 cells and plant imaging in soybean roots.

Chitosan and Anionic Solubility Enhancer Sulfobutylether-β-Cyclodextrin-Based Nanoparticles as Dexamethasone Ophthalmic Delivery System for Anti-Inflammatory Therapy.

Cataract surgery interventions are constantly increasing, particularly among adult and elderly patients. This type of surgery can lead to inflammatory states of the ocular anterior segment (AS), usually healed via postoperative treatment with dexamethasone (DEX)-containing eye drops. The application of eye drops is challenging due to the high number of daily administrations. In this study, mucoadhesive nanoparticles (NPs) were formulated to improve the residence time of DEX on the corneal mucosa, enhancing the drug's solubility and bioavailability. The NPs were generated using an ionotropic gelation technique, exploiting the interaction between the cationic group of chitosan (CS) and the anionic group of sulfobutylether-β-cyclodextrin (SBE-β-CD). The formation of the inclusion complex and its stoichiometry were studied through phase solubility studies, Job's plot method, and Bi-directional transport studies on MDCKII-MDR1. The obtained NPs showed good chemical and physical characteristics suitable for drug loading and subsequent testing on animal mucosa. The DEX-loaded CS/SBE-β-CD NPs exhibited a prolonged residence time on animal mucosa and demonstrated enhanced drug permeability through the corneal membrane, showing a sustained release profile. The developed NPs posed no irritation or toxicity concerns upon local administration, making them an optimal and innovative drug delivery system for inflammatory AS diseases treatment.

A hepatocyte-targeting fluorescent probe of dicyanomethylene-4H-pyran to detect cysteine in living cells and zebrafish: Design, synthesis and evaluation

In this study, a novel hepatocyte-targeting fluorescent probe DCM-Cys-Gal detecting cysteine (Cys) was developed. The low toxic DCM-Cys-Gal could simultaneously exhibit good sensitivity and selectivity, long emission wavelength, low detection limit toward Cys, and pH independency under the physiological range. The responsive mechanism of DCM-Cys-Gal toward Cys was proposed based on LC-MS and Job's plot experiment. DCM-Cys-Gal could effectively differentiate hepatocellular carcinoma cells from other tissue cells, and visualize detection Cys in zebrafish, which could be conducive to the early diagnosis of Cys-related diseases.

The effect of Cu(II) ion on antioxidant and DNA‐binding mechanism of baicalein and scutellarein: Spectroscopic, theoretical, and molecular docking study

Flavonoids are a group of polyphenolic compounds known to possess good radical scavenging activity. It was also shown that their anti/prooxidant properties are strongly structure‐dependent and can be modified by metal ion binding. The structural parameters also appear to be key factors during their DNA‐binding abilities. This work deals with spectroscopic and theoretical studies of two flavonoids, baicalein and scutellarein, alone, and in the presence of redox‐active metal ion Cu(II). Cu(II) is the catalytic active ion in Fenton‐like reactions and can enhance the production of reactive oxygen species or, when bound to the flavonoid, influence its antioxidant potential. UV–Vis spectroscopy showed that the electronic properties of the parent flavonoids are changed following the CuCl2 addition. Job's plot method revealed the 1:1 binding mode of interaction in DMSO and DMSO/PBS solvent. The ABTS•+ assay showed only a negligible effect of Cu(II) presence on the antioxidant properties of baicalein and scutellarein. The mix of the natural reductant, glutathione, with flavonoids showed a synergistic effect in ABTS•+ inhibition; however, this effect was suppressed by the presence of Cu(II). Absorption titration and molecular docking studies showed an effective DNA binding of both flavonoids that is further enhanced by the presence of Cu(II). DFT calculations were carried out to identify the most energetically stable Cu(II)–flavonoid structures as well as to determine the ability of their hydroxyl groups to undergo homolytic or heterolytic cleavage.

A Sensitive Probe of Meso-Cyanophenyl Substituted BODIPY Derivative as Fluorescent Chemosensor for the Detection of Multiple Heavy Metal Ions.

A fluorescent turn-on chemosensor (BA) was constructed by attaching bis(pyridin-2-ylmethyl)-amine (DPA) unit to the BODIPY scaffold. It can give a prominent green/yellow fluorescent response selectivity with each of Zn2+/Hg2+/Cd2+/Ca2+/Mn2+/Pb2+/Al3+. The 1:1 stoichiometry of BA and metal ions was drawn from the analysis of Job's plot. The limit detection of BA in recognition of Zn2+/Hg2+/Cd2+/Ca2+/Mn2+/Pb2+/Al3+ is ranged in 50.8-146.6 nM. There exists a linear relationship between the fluorescence intensity and concentration of metal ions (Zn2+: 4-15 µM). The mechanism of fluorescence signal "turn-on" is based on the photo induced transfer (PET) in the excited state of BA. The coordinated metal ions significantly weakened the electron-donating ability nitrogen atom in DPA, thus recovering the emission character of BODIPY. The substituted group at the phenyl ring in meso-position of BODIPY scaffold determines the recognizable list of metal ions.

A Novel Multi-Functional Fluorescence Probe for the Detection of Al3+/Zn2+/Cd2+ and its Practical Applications.

A novel multi-functional fluorescence probe HMIC based on hydrazide Schiff base has been successfully synthesized and characterized. It can distinguish Al3+/Zn2+/Cd2+ in ethanol, in which fluorescence emission with different colors (blue for Al3+, orange for Zn2+, and green for Cd2+) were presented. The limits of detection of HMIC towards three ions were calculated from the titration curve as 7.70 × 10- 9 M, 4.64 × 10- 9 M, and 1.35 × 10- 8 M, respectively. The structures of HMIC and its complexes were investigated using UV-Vis spectra, Job's plot, infrared spectra, mass spectrometry, 1H-NMR and DFT calculations. Practical application studies have also demonstrated that HMIC can be applied to real samples with a low impact of potential interferents. Cytotoxicity and cellular imaging assays have shown that HMIC has good cellular permeability and potential antitumor effects. Interestingly, HMIC can image Al3+, Zn2+ and Cd2+ in the cells with different fluorescence signals.

Spectroscopic Investigation of Coumarin Based Novel Fluorescent TURN OFF Sensor for the Selective Detection of Fe3+: In-vitro Live Cell Imaging Application.

The novel TURN-OFF fluorescent sensors 4-(Benzo[1,3]dioxol-5-yloxymethyl)-7-hydroxy-chromen-2-one (4BHC) and 4-(6-Bromo-benzo[1,3]dioxol-5-yloxymethyl)-7-hydroxy-chromen-2-one (4BBHC) are designed and synthesized for the spectrofluorometric detection of the biologically important Fe3+ ions, which has sensitive and selective fluorescence quenching over other competitive metal ions. The effectiveness of the sensors and rapid response are validated through UV-Visible, and fluorescence spectral changes. These spectral changes could be due to the formation of coordination bond between ligand and metal ion. The binding stoichiometry of both sensors with Fe3+ ions is studied with the help of Job's plot, which gives a 1:2 coordination ratio; this is further confirmed through DFT, IR and NMR studies. The association constants of 4BHC and 4BBHC are calculated through Benesie-Hildebrand plots, and they are found to be 6 × 104M-1 and 11.2 × 104M-1 respectively. Following, LOD is calculated to define the range of sensitivity of the proposed sensors and is found to be 3.43μM and 2.14μM respectively. The chemical hardness parameter suggested that both sensors are soft molecules. In addition, low cytotoxicity levels of 4BHC and 4BBHC led to the demonstration of their efficacy in In-Vitro imaging of Fe3+ ions inside living cells, which ensures that these sensors are promising candidates for bioimaging.

Two helical Schiff bases with “AIE+ESIPT” characteristics exhibiting selective ion recognition properties

Two racemic Schiff bases (H4L1 and H4L2) were synthesized and characterized, and the crystal structures indicated their helical configurations with equal amounts of P- and M-helicity. The aggregation-induced emission (AIE) and selective ion recognition properties of H4L1 and H4L2 were investigated using UV–vis absorption and fluorescence spectra. The results showed that both H4L1 and H4L2 exhibited obvious “AIE + ESIPT” characteristics in THF/H2O solution upon increasing the water fraction. Both H4L1 and H4L2 displayed an obvious turn-off fluorescence response to Cu2+ and F−, and a slight turn-off response to Fe3+ in DMSO, while they displayed an efficient selective ion recognition of Cu2+ in THF/H2O (1: 1, V/V). The corresponding stoichiometry ratio, association constant, Stern-Volmer quenching constant, and the detection limits were determined via Job's plots, UV–vis spectra titration as well as fluorescence spectra titration experiments. The crystal structures of the complexes obtained from the interactions of H4L1 with Cu2+ and Fe3+ illustrated their binding modes and binding differences, which helped us interpret the ion recognition mechanism of H4L1 and H4L2. In addition, the application of H4L2 on test strips was performed, indicating that H4L2 can be used for the rapid detection of Cu2+ and F− in THF. The acid-responsive fluorescence behavior of H4L2 showed that the white light emission can be obtained upon the addition of hydrochloric acid or aldehyde c into H4L2.

Fluorescent imidazole derived sensor for selective in vitro and in vivo Fe2+ detection and bioimaging in zebrafish with DFT studies

Herein, we have developed imidazole derivatized fluorescent probes IM-1 and IM-2 for extremely selective detection of Fe2+ with rapid response (LOD: 3.245 μM for IM-1 and 0.297 μM for IM-2) and excellent binding constants (0.214 × 105 M−1 and 1.004 × 105 M−1). Aqueous ethanol system was employed to assess the sensing potency of the probes both in vitro and in vivo in zebrafish is the main highlight of this work. The synthesized fluorophores possess admirable quantum yields of 0.61 and 0.78. The 1:1 binding mechanism of ligands with Fe2+ ions is supported by Job's plot and ESI-Mass spectrum. The synthesized probes demonstrated limited cytotoxicity both in vitro (MDA-MB-231 cells) and in vivo (zebrafish, Danio Rerio) studies. These results prompted us to employ the probes IM-1 and IM-2 to trace out intra cellular Fe2+ ions in zebrafish embryos.

Exploring Brilliant Blue FCF Assembly with Beta Cyclodextrin, Characterizations and Applications in Biological Systems Using Physicochemical and Computational Methods

AbstractThis research delvedinto the BrilliantBlue FCF (BB) dye encapsulation within the nano hydrophobic cavity of β‐cyclodextrin (β‐CD) utilizing various spectroscopic and physicochemical techniques. Job's plot using UV‐visible and Fluorescence spectroscopy, surface tension, and conductance study confirmed 1 : 1 stoichiometry of theinclusion complex (BBIC).1H NMR and FT‐IR studies demonstrated the possible binding mode of BB into the β‐CD cavity, which wasin good agreement withthe DFT study. The degree of affinity of β‐CD for BB in the ground state and excited state were estimatedfromUV‐visible andFluorescence spectroscopy(binding constant=8113.9451 M−1and10199.563 M−1), andthe negative free binding energyshowedthe encapsulation process to bethermodynamically feasible. PXRD analysis and SEM image studies revealed the formation of the BBIC. After complexation with β‐CD, the photostability of BB was found to be enhanced. The interaction study of BB and BBIC with CT‐DNA revealed the sustained release of BB from the complex. Furthermore, neither BBICnor free BB exhibited a significant cytotoxic effect on the normal cell line HEK‐293. However, BBIC complex (IC50=6.15 μM) showed significant in vitrocytotoxic activity compared to pure BB (IC50=8.90 μM) towards cancer cell line A549.

Salicylaldehyde built fluorescent probe for dual sensing of Al3+, Zn2+ ions: Applications in latent fingerprint, bio-imaging & real sample analysis

This Schiff base chemosensor (SNN) detected dual ions, Al3+ and Zn2+ ions selectively. Fluorescence spectrum investigations showed that Al3+ ions increased fluorescence intensity, notably at 493 nm. Introducing Zn2+ ions caused a significant blue shift of roughly ∼65 nm at a wavelength of 434 nm, resulting in a notable change in fluorescence intensity. When binding Al3+/Zn2+ ions, the SNN receptor uses three methods. Inhibition of photoinduced electron transfer (PET), excited state intramolecular proton transfer (ESIPT), and restriction of CN isomerization. The jobs plot method found that SNN + Al3+ and SNN + Zn2+ complexations had a 1:1 stoichiometry. DFT, LC-HRMS, and 1H NMR titration confirm this conclusion. The probe SNN's limit of detection (LOD) for Al3+/Zn2+ ions was 3.99 nM and 1.33 nM. Latent fingerprint (LFP), food samples, pharmaceutical products, and E. coli pathogen bio-imaging have all used the SNN probe to identify Al3+ and Zn2+ ions.