Job's Plot Research Articles

Silver induced self-assembly of a rhodanine derived reversible fluorescent chemosensor: Applications in smart-phone color assist app, logic gate, real sample analysis and bio-imaging

An innovative chemosensor, Rhodanine-appended benzaldehyde (RB), was developed and analyzed using spectroscopic methods to detect silver ions (Ag+) in a THF–H2O buffer solution via fluorimetry. The RB probe exhibited low fluorescence due to C-N free rotation and inhibition of electron transfer. However, interaction with Ag+ ions resulted in a noteworthy redshift of approximately 6 nm and increased fluorescence intensity owing to the chelation-enhanced fluorescence (CHEF) effect, which hindered the Intramolecular Charge Transfer (ICT) process. The binding ratio between RB and Ag+ ions was determined to be 2:1 using the job plot method. The association constant (Ka) was calculated to be 4.84 × 105 M−1 and further confirmed through ESI-TOF spectroscopic and DFT analyses. The limit of detection (LOD) and quantification (LOQ) for RB in binding with Ag+ ions were found to be 1.7 × 10−8 M and 5.4 × 10−8 M, respectively. Additionally, the color changes of RB when binding with Ag+ ions were effectively leveraged in an RGB-assisted smartphone color analysis app for precise sample analysis for Ag+ ion detection. Most importantly, the RB probe’s ability to detect silver ions in the E. coli pathogen was successfully demonstrated, providing reassurance about its practical application, using a confocal scanning electron microscope via the green channel.

Constructing ESIPT-Capable α-Cyanostilbene Luminogens: Influence of Different Aromatic Substitutions Tethered to H-Acceptor (CH = N) on Photophysical Properties, Cu2+ and Fe3+ Detection.

Herein, two excited-state intramolecular proton transfer (ESIPT)-capable α-cyanostilbene luminogens were synthesized by Schiff base reaction of salicylaldehyde-like α-cyanostilbene candidate with 1-naphthylamine and 3-biphenylamine, respectively. We systematically analyzed their photophysical properties compared with their analogue, and demonstrated that their fluorescence behaviors could be elaborately modulated by different aromatic substitutions tethered to H-acceptor (CH = N). In virtue of the outstanding solid fluorescence, the 3-biphenylamine-decorated fluorophore was applied for monitoring Cu2+/Fe3+ qualitatively on the TLC-based test strip in real time and sensing Cu2+/Fe3+ quantitatively in the THF/H2O medium (fw = 90%, pH = 7.4). When the probe chelated with Cu2+/Fe3+, similar "turn-off" fluorescence signal outputs were triggered. From the fluorescence titration experiments, the detection limits were evaluated as 7.97 × 10- 8 M for Cu2+ and 8.24 × 10- 8 M for Fe3+, and the binding constant (Kα) values of the complexes were found to be 7.80 × 104 M-1 for Cu2+ and 9.06 × 104 M-1 for Fe3+. Job's plots indicated that probe complexed with Cu2+/Fe3+ in a 2:1 binding stoichiometry ratio. Furthermore, the probe was used to accurately quantify the Fe3+ spiked in real water specimens. This study offered a new perspective to construct ESIPT-capable α-cyanostilbene luminogen as the potential luminescent probe.

Novel coumarin-Schiff base derived electronically distinct fluorescent probes: Synthesis and comparative investigations of their unique selective sensing properties with Cu2+ and Cu+ ions

The present work describes the synthesis and comparative investigations of Cu2+ and Cu+ ions sensing properties of two novel π-extended coumarin-Schiff base-derived electronically distinct fluorescent probes (4 and 5). Due to the additional electron donating group substituent (-NEt2) close proximate to the binding site of Schiff base in probe 5, it exhibits distinct electronic properties compared to probe 4. Our studies indicate that probe 5 displays efficient and highly selective fluorescence quenching behaviors with Cu2+ and Cu+ ions compared to other competitive metal ions (Ca2+, Mg2+, Al3+, Hg2+, Pb2+, Cd2+, Mn2+, Co2+, Ni2+, Fe2+, Fe3+, Cr3+ and Zn2+). In our studies, Job's plot experiments revealed that the binding stoichiometry of the ligand-Cu2+ was 1:1 for both probes. The limit of detection (LOD) of 2.35 × 10–5 M and 1.56 × 10–5 M were obtained for the probes 4 and 5, respectively. Further, the Stren-Volmer equation has been used to calculate the binding abilities of probes with Cu2+ ions; it reveals the binding constant of 6.70 × 104 M-1 and 22.0 × 104 M-1 for probes 4 and 5, respectively. Also, in the present studies, our DFT computed results were comparatively presented to understand the electronic parameters (HOMO-LUMO energy band gaps, ESP and Mulliken atomic charge distribution) of compound 1, probes 4 and 5. We anticipate that the developed probes can be used to analyze Cu2+ and Cu+ ions in environmental and biological samples.

Synthesis, Characterization, DPPH Radical Scavenging, Urease Enzyme Inhibition, Molecular Docking Simulation, and DFT Analysis of Imine Derivatives of 4-formylpyridine with Selective Detection of Cu+2 Ions.

This study aimed to prepare three imine derivatives (1, 2, and 3) via a condensation reaction of phenyl hydrazine, 2-hydrazino pyridine, and 4-methoxy aniline with 4-formyl pyridine. Electron impact mass spectrometry (EIMS), proton nuclear magnetic resonance (1H-NMR), ultraviolet-visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy were utilized for the characterization. The chemosensing properties of [4((2-phenyl hydrazono)methyl) pyridine] (1), [2-(2-(pyridin-4-ylmethylene)hydrazinyl) pyridine] (2), and [4-methoxy-N-yl methylene) aniline] (3) imino bases have been explored for the first time in aqueous media. The photophysical properties of chemosensors (1, 2, and 3) were examined by various cations (Na+, NH4+, Ba+2, Ni+2, Ca+2, Hg+2, Cu+2, Mg+2, Mn+2, and Pd+2). The chemosensor (1) showed very selective binding capability with copper ions at low concentrations (20 μM) without the influence of any other mentioned ions. The maximum complexation was noted with Cu+2 and 1 at pH between 7 to 7.5. The stoichiometry binding ratio between chemosensor (1) and Cu+2 was determined by Job's plot and it was found to be 1:2. The current study explored the use of these Schiff bases for the first time as heterocyclic chemosensors. DPPH radical scavenging, urease enzyme inhibition activities, molecular docking simulation, and density functional theory (DFT) analysis of compounds 1, 2, and 3 were also conducted.

Synthesis, Characterization, Spectroscopic, and Electrochemical Investigation of Inclusion Complex of Ethyl Cinnamate with γ‐Cyclodextrin for Antibacterial Studies

AbstractWe synthesized cinnamic acid derivatives of ethyl cinnamate (EC) and analyzed the resulting products using 1H‐NMR and FTIR spectroscopy. The formation of the confirmed EC and γ‐Cyclodextrin inclusion complex is investigated through UV–vis and fluorescence spectroscopy. Cyclic voltammetry techniques are employed to analyze the formation of the inclusion complex. By using Job's plot, the stoichiometric ratio of the inclusion complex is found to be 1:1, and the binding constant (K) is calculated through the Benesi‐Hildebrand plot. Furthermore, we calculated the thermodynamic parameters (ΔG) using the Gibbs‐Helmholtz free energy equation, indicating that the formation of this inclusion complex is spontaneous. The molecular interaction between EC and the hydrophobic cavity of γ‐CD is characterized using 2D NMR (ROESY), revealing their specific interactions. Research highlights the need for antibacterial studies due to the rise of new infectious diseases. Specifically, the study investigates the antibacterial activity of inclusion complexes compared to the guest molecule alone.

Machine learning-assisted colorimetric sensor array for rapid identification of adulterated Panax notoginseng powder

Panax notoginseng (PN) is a popular functional food worldwide, yet adulterated PN powders are prevalent in the commercial market. Herein, a method combining a low-cost colorimetric sensor array and machine learning is proposed to rapidly identify and quantify adulterated PN powder. We constructed a sensitive indicator displacement assay (IDA) sensor array by innovatively using Job's plot to optimize sensor units. The array was used to identify adulterated PN powders after its discriminatory ability was evaluated by amino acid analysis. Among the four machine learning models, the support vector machine (SVM) models achieved the highest accuracy, with above 98.3% for authenticity and 99.0% for adulteration types. The blending percentages of four PN adulterants were further analyzed quantitatively using support vector machine regression (SVR) models with good prediction ability (R > 0.93). Finally, our sensor array method was applied to identify commercially available PN powders with satisfactory results. This study offers a low-cost new method for the rapid identification of PN powder, contributing to quality control of powdered food.

Exploring dual-channel ion detection and theoretical insights: Chromone-based colorimetric receptor for Cu2+and its Zn(II)-complex as ultrasensitive fluorescent probe for Ag+ and Fe3+

Present article delineates the design and synthesis of a chromone-appended Schiff base (1) and its complexes with Zn(II) (2) and Cu(II) (3), which have been characterized by various spectro-analytical techniques i.e., elemental analysis, FTIR, 1H & 13C NMR, ESI-MS, UV−vis and fluorescence. Structures of 1 and 3 have also been elucidated using single crystal X-ray diffraction analysis. Compounds 2 showed significant effect in vitro cytotoxicity as compared to 1 Against MDA−MB-231 cell line. Interestingly, 1 serves as a chromogenic sensor for Cu2+ with exceptional selectivity whereas, 2 serves as an ultrasensitive fluorescent probe for Ag+ and Fe3+ in mixed aqueous−ethanol. The presence of Ag+ causes ratiometric change in the fluorescence spectral feature of 2 whereas Fe3+ induces ‘turn-off’ fluorescence in 2. Probe−analyte binding stoichiometry suggested by Job's plot analysis, ESI−MS and DFT studies, has been found to be 1:1 for 1 with Cu2+ and 2 with Ag+ whereas, 1:2 between 2 and Fe3+. Based on diverse analyses and binding constants, it is observed that 2 offers higher selectivity toward Ag+ over Fe3+. Limit of detection (LoD) of 1 for Cu2+ and 2 for Ag+ and Fe3+ have been found to be 2.33 nM, 22.4 µM and 2.05 µM, respectively. Complexes 2+Ag+ and 2+Fe3+ characterized by ESI−MS whereas DFT studies have been carried out to investigate the deeper bonding insights and provide support in our experimental investigations. Further, detection of Ag+ and Fe3+ has been practically accomplished in real water samples using probe 2.

Structural and antibacterial assessment of two distinct dihydroxy biphenyls encapsulated with β-cyclodextrin supramolecular complex

β-Cyclodextrin plays a vital role in biological application because it can enhance the stability and solubility of the guest molecules in the supramolecular inclusion complexes. Moreover, the β-Cyclodextrin inclusion complex has control-releasing behavior and lower toxicity than bare guest molecules. To improve the solubility and stability properties of two structurally different fluorescent guest molecules, namely 2,2′-dihydroxy biphenyl and 3,3′-dihydroxy biphenyls, they involve the β-Cyclodextrin inclusion complex process. Optical measurements clearly described the efficient binding through the changes in the absorbance and emission intensities of guest molecules in the presence of β-Cyclodextrin. The Job's plot from absorbance measurements reveals the 1:1 stochiometric ratio of binding of guests and the β-Cyclodextrin host. The FT-IR spectra of the solid complex show the characteristic stretching and bending vibrations from both the guests and the host molecule. The 1HNMR spectra of the inclusion complex promote downfield shifting of guest molecule protons upon binding with the β-Cyclodextrin host. The solid complex prepared using the solution method exhibits superior antibacterial activity against both gram-positive and gram-negative bacteria compared to the kneading and physical mixing methods.

Selective Chromo-Fluorogenic Chemoprobe for nM Al3+ Recognition: Experimental and Living-Cell Applications.

A rhodamine based chemoprobe BESN was engineered and employed as a selective ''OFF-ON'' chromo-fluorogenic sensor for Al3+ in H2O:MeOH (1:9, v:v). Notable changes in the absorption and emission spectra of BESN were clearly detectable upon the addition of Al3+. Sensitivity and binding mechanism studies demonstrated a good sensing performance of BESN with nanomolar detection limit (130nM), and it was found to be highly selective towards interfering metal ions. Besides, the binding constant between BESN and Al3+ was found to be 3.19 × 103M-1. Then, the validation study of BESN for Al3+ was performed based on significant analytical parameters and statistical tests. The binding of Al3+ with BESN (1:1) was probed via infrared, high-resolution mass and emission (Job's plot) spectroscopy measurements. The sensing performance of BESN could make it ideal chemosensor for real applications including vegetable, tuna fish and water samples, also for Smartphone and test-kit applications. The recovery values of the BESN to Al3+ were estimated within a range from 95.13% to 105.30% for water, 94.63% to 109.62% for tuna fish and 94.80% to 109.80% for vegetable samples. Additionally, the BESN has very low cytotoxicity and was triumphantly utilized for the recognition of Al3+ in living-cells.

2-hydroxy-1- Naphthaldehyde Based Colorimetric Probe for the Simultaneous Detection of Bivalent Copper and Nickel with High Sensitivity and Selectivity.

A neoteric colorimetric probe based on 2-hydroxy-1-naphthaldehyde (PMB3) was designed and synthesized for the real-time as well as on-site naked-eye detection of Cu2+/Ni2+ ions. Various physicochemical methods were employed to characterize the probe, and its colorimetric response to different metal ions was meticulously investigated. The probe, PMB3, exhibited a sensitive colorimetric response to Cu2+/Ni2+ ions among other competing metal ions, culminating in a prominent colour change from colourless to yellow. The stoichiometry of the ligand metal complexes was ascertained to be in a 1:1 ratio using Job's plot analysis, which was further corroborated by ESI-MS data. With detection limits of 4.56µM for Cu2+ and 2.68µM for Ni2+, the method was effectively extended to real sample analysis, ensuring propitious results that closely aligned with the actual values.

Investigation of Host-Guest Inclusion Complex of Mephenesin with α-Cyclodextrin for Innovative Application in Biological System.

The goal of this study was to use coevaporation to look into how polyether compounds like mephenesin (MEP) can be encapsulated into the host molecule α-cyclodextrin's nanohydrophobic cage. Fourier transform infrared spectroscopy (FT-IR) investigations, powder X-ray diffraction (PXRD), and 1H NMR were among the spectroscopic techniques used to describe the inclusion complex. Additionally, Job's plot has been utilized to illustrate how MEP is encapsulated with α-cyclodextrin (α-CD) at a 1:1 molar ratio. The thermal stability of MEP increased after encapsulation according to thermogravimetric analysis (TGA) and differential thermal analysis (DTA) experiments. Mephenesin fits into the cavity of α-cyclodextrin in a 1:1 ratio, as observed by molecular docking for the inclusion complex to find the most appropriate orientation. This observation is further supported by the Job plot. Furthermore, a comparison was carried out based on a cell viability study between the medication and its inclusion complex.

Visual‐Detection of Cu2+ in DMSO aAqueous Solution Based on Benzimidazole Azo‐dye as a Colorimetric Chemosensor

AbstractIn this work, a novel colorimetric chemosensor (BIAD) containing azo chromophore, 1,5dihydroxynaphthalene, and benzimidazole was synthesized and characterized by using IR, 1H,13C NMR, and mass spectral data, and elemental analysis. The cation recognition studies (including fourteen metal cations) exhibited that the synthesized azo dye can act as a rapid, sensitive, and selective colorimetric chemosensor for detecting Cu2+ ions. The addition of Cu2+ ions to the BIAD solution, changed immediately the solution color from purple to blue‐green, which could be observed by the naked eye. Comparison of the UV/Visible spectra of BIAD and (BIAD+Cu2+) revealed a red shift from 543 nm to 616 nm, which confirms the formation of a complex between Cu2+ cations and BIAD molecules. The result of Job's plot indicated that the stoichiometry binding ratio of BIAD to Cu2+ is 1 : 1. The limit of detection (LOD) was found for BIAD toward Cu2+ ion to be 0.10 μM. Furthermore, the BIAD‐based test paper strips were successfully used for the rapid detection of Cu2+ ions (<1 sec) in the aqueous solution (H2O‐DMSO, 9 : 1).

Carbohydrate-modified simple efficient fluorometric probe for sensing Cu2+ions in aqueous solution

Triazole-appended pyrenyl-modified carbohydrate 1 was introduced in one step for detecting Cu2+ ions over various metal ions and anions in a 90 % aqueous acetonitrile medium. Selectivity of 1 towards Cu2+ ions was established from spectroscopic (absorbance and fluorescence) variations. Probe 1 is more effective in sensing Cu2+ ions within the pH range from 6 to 11. The quenched fluorescence of 1 with Cu2+ at a second was attributed to the reverse PET process from pyrene to electron-deficient Cu2+. The Stern-Volmer plot indicated static quenching at lower concentrations of Cu2+ ions, but both static and dynamic quenching processes were involved at higher concentrations. The ligand-metal ratio (1:1) was established from the Job plot and supported by the complex's HRMS data. The detection limit of 1 (0.08 µM) indicated that probe 1 can detect Cu2+ ions in the micromolar range. The binding mode of 1 with Cu2+ and HOMO-LUMO of 1 and 1-Cu2+ were discussed from DFT calculations. Finally, the practical use of the probe was established from the recovery of Cu2+ ions from natural water samples.

A Novel AIE-Active Salicylaldehyde-Schiff Base Probe with Carbazole Group for Al3+ Detection in Aqueous Solution.

A donor-acceptor Schiff-base fluorescent probe BKS with chelation enhanced fluorescence (CHEF) mechanism was designed and synthesized via benzophenone(Acceptor), salicylaldehyde and carbazole(Donor) for Al3+ detection, which exhibited typical aggregation-induced emission (AIE) characteristic. BKS probe could provide outstanding selectivity to Al3+ with a prominent fluorescence "turn-on" at 545nm in a wide pH range from 2 to 11. By the Job's plot, the binding stoichiometry ratio of probe BKS to Al3+ was determined 1:1. The proposed strategy offered a very low limit of detection at 1.486 µM in THF/H2O(V/V = 1:4, HEPBS = 10 mM, pH = 7.40),which was significantly lower than the standard of WHO (Huang et al., Microchem J 151:104195, 2019)-(Yongjie Ding et al., Spectrochim Acta Mol Biomol Spectrosc 167:59-65, 2021) guidelines for drinking water. BKS probe could provide a wider linear detection range of 50 to 500 µM. Furthermore, the probe could hardly be interfered by other examined metal ions. The analysis of Al3+ in real water samples with appropriate recovery (100.72 to 102.85) with a relative standard deviation less than 2.82% indicated the accuracy and precision of BKS probe and the great potential in the environmental monitoring of Al3+.

5-Oxo-7,7-Dimethyl-5,6,7,8-Tetrahydro-4-H-Chromene Bearing N, N-Dimethylaniline as Turn-Off Fluorescent Chemosensor for Picric Acid in Real Water Sample.

We have synthesized a one-pot, three-component pyran-based fluorescence chemosensor using onion extract as a green catalyst. The confirmed structure of the 1:2 binding of receptor SPR-2-picric acid adduct revealed that the pyran-based receptor accommodated two guest picric acid molecules through non-covalent interactions. UV-Vis and fluorescence spectroscopy show high selectivity and sensitivity towards picric acid. The 1D/2D NMR and Job's plot analysis show the complexation and stoichiometric binding of the receptor SPR-2 with picric acid are 1:2. The 1H NMR spectral studies confirm that the formation of receptor SPR-2-picric acid adduct via weak hydrogen bonding. The cooperativity of the receptor SPR-2-picric acid adduct shows negative cooperativity due to the weak hydrogen bonding of receptor SPR-2 and picric acid. Further, the density functional theory (DFT) confirmed the molecular level interaction of the SPR-2 and receptor SPR-2-Picric acid adduct. The receptor was effectively used to assess picric acid concentrations in real water samples.

Indole Schiff Base Complex: Synthesis and Optical Binding Investigation with Biogenic Amines.

Biogenic amines, produced by bacterial enzymatic reactions in food storage or processing, serve as indicators in food processing industries to assess food quality and freshness. Biogenic amines also often associated with various health problems, including abnormal immune responses and gastrointestinal disease. Previously, salphen base complexes have been reported but still exhibited low fluorescence enhancement upon biogenic amines. This research focused on synthesizing and characterizing new Zn(II) Schiff base complex with indole sidechain to enhance the fluorescence property and exploring their binding behaviour with the biogenic amines, which were phenylethylamine and cadaverine. The Zn(II) indole Schiff base complex's structure was verified by diverse spectroscopic techniques. Then, the binding behaviours between the Zn(II) indole Schiff base complex with the biogenic amines were analyzed using UV-Vis, fluorescence spectroscopy, and Job's plot analysis. UV-Vis binding study results indicated that the synthesized complexes could bind stronger with phenylethylamine than cadaverine, with binding constant, Kb= (8.21 ± 0.58) × 104 M- 1 and (2.506 ± 0.004) × 104 M- 1 respectively. Moreover, Zn(II) indole Schiff base complex-phenylethylamine binding also generated higher fluorescence enhancement than cadaverine, which were 54% and 51% respectively. Based on Job's plot analysis, the complex and biogenic amines were bound in the ratio of 1:1. To conclude, the synthesized complex has promising potential as a sensing material for biogenic amines detection in food. The complex is recommended to be deployed in the development of solid-state fluorescence sensor for biogenic amines detection for monitoring the food spoilage in the food industry in the future.

A simple turn-on fluorescent sensor for Cu2+ detection based on Schiff base via restricted ICT and fabrication of paper strips for on-site visual sensing applications

Herein, Sensor RN2 was prepared by condensation of 2‑hydroxy-1-naphthaldehyde and 2-chloroaniline and well characterized by FTIR, PXRD, 1H NMR, and 13C NMR. Photophysical investigation reveals that sensor RN2 exhibits remarkable colorimetric and fluorometric “turn-on” behavior towards Cu2+ with high selectivity and sensitivity in the presence of other examined metal ions. The stoichiometric ratio was determined to be 2:1 for RN2 and Cu2+ based on the Job plot, DFT and HRMS analysis. The detection limit for Cu2+ reached the nM level. The binding constant of RN2 with Cu2+ was 2.55 × 1011M−2. RN2 was successfully applied for quantitative recognition of Cu2+ in biological and environmental samples. The test strips based on RN2 were fabricated, which could act as an efficient and convenient Cu2+test kit.

Reduced nephrotoxicity of epichlorohydrin-crosslinked β-cyclodextrin nanoparticles (βCDNPs) and its enhanced binding with hydrophobic compounds

This paper explores the development and characterization of epichlorohydrin-crosslinked β-cyclodextrin nanoparticles (βCDNPs) for drug delivery, focusing on their interaction with hydrophobic drugs and biocompatibility. We synthesized βCDNPs using β-cyclodextrin (βCD) and epichlorohydrin (ECH). Our study assessed the biocompatibility and safety of βCDNPs, particularly in avoiding nephrotoxicity commonly associated with βCD, by examining their interaction with cholesterol and conducting survival analyses in mice at various dosing concentrations. Additionally, we highlight the advantages of using diffusion-ordered NMR spectroscopy (DOSY) to determine the enhanced binding constants of βCDNPs with hydrophobic compounds, in comparison with the solubility method, Job plot analysis, and isothermal titration calorimetry (ITC). We demonstrated the enhanced binding capacity of βCDNPs compared to βCD alone and established the polymerization of βCD as a significant factor in this enhancement. Our findings suggest that βCDNPs show promise as drug delivery systems due to their improved solubility, stability, and safety profiles.

Novel benzothiazole-based fluorescent probe for efficient detection of Cu2+/S2− and Zn2+ and its applicability in cell imaging

BackgroundIn recent years, environmental pollution has been increasing due to the excessive emission of toxic ions, which has caused serious harm to human health and ecological environment. There are various methods for detecting Cu2+, S2− and Zn2+, but the traditional ion detection methods have obvious disadvantages, such as poor selectivity and long detection time. Therefore, it is still crucial to develop simple, efficient and rapid detection methods. ResultsA fluorescent probe based on benzothiazole, (E)-N'-(3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzylidene)-3,4,5-tris(benzyloxy)benzohydrazide (BT), was designed and synthesized. It was characterized using ESI-MS, 1H NMR, and 13C NMR. BT can be used as a chemosensor to detect Cu2+, S2− and Zn2+ in CH3CN/H2O (7:3, v/v, pH = 7.4, HEPES buffer: 0.1 M), with detection limits of 0.301 μM, 0.017 μM, and 0.535 μM, respectively. At an excitation wavelength of 320 nm, BT exhibits an “on-off-on” response to Cu2+/S2− and enhanced fluorescence response to Zn2+, with a change in fluorescence color from orange to green. The coordination ratio of ions to the probe was determined to be 1:1 through Job's plot and hydrogen spectral titration. The recognition mechanism was discussed in conjunction with theoretical calculations. Furthermore, the probe has been successfully used in test strips and medical swabs colorimetry, as well as live cell imaging. SignificanceThe probe BT lays the foundation for the design and synthesis of multifunctional fluorescent probes. As a portable detection method, probe BT was used to detect Cu2+, S2− and Zn2+ on strips. Furthermore, the probe was applied to biological cells to detect target ions with low cytotoxicity and excellent cell permeability. This indicating that it can be used as a potential candidate for tracking Cu2+ and S2− in clinical diagnostics and biological systems.

A 1,8-Naphthalimide-based Tripodal Fluorescent Chemosensor to Selectively Detect Copper Ions.

A 1,8-naphthalimide-based tripodal fluorescent ligand (L3) was synthesized through the copper (I) catalyzed Huisgen azide-alkyne cycloaddition reaction of 2-(2-azidoethyl)-6-morpholino-1H-benzo[de]isoquinoline-1,3(2H)-dione with triproparagylamine. Naphthalimide acts as the fluorophore while the triazole and amine nitrogens chelate the metal ion. L3 showed a selective fluorescence turn-off for Cu(II) over other metal ions in aqueous acetonitrile solution. A Job's plot, Benesi-Hildbrand plot and high-resolution mass spectrometry data confirm a 1:1 binding stoichiometry with a binding constant of 7.8 х105 M- 1 while addition of disodium EDTA demonstrates its reversibility. The structure and stability of the complex was supported by theoretical calculations. The limit of detection for Cu(II) was calculated to be 0.3 µM which is considerably lower than WHO recommended Cu(II) limit in drinking water.