Selective Fluorescent Chemosensor Research Articles

Development of a simple polymer-based sensor for detection of the Pirimicarb pesticide

In this study, a sensitive and selective fluorescent chemosensor was developed for the determination of pirimicarb pesticide by adopting the surface molecular imprinting approach. The magnetic molecularly imprinted polymer (MIP) nanocomposite was prepared using pirimicarb as the template molecule, CuFe2O4 nanoparticles, and graphene quantum dots as a fluorophore (MIP-CuFe2O4/GQDs). It was then characterized using X-ray diffraction (XRD) technique, Fourier transforms infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and transmission electron microscopy (TEM). The response surface methodology (RSM) was also employed to optimize and estimate the effective parameters of pirimicarb adsorption by this polymer. According to the experimental results, the average particle size and imprinting factor (IF) of this polymer are 53.61 nm and 2.48, respectively. Moreover, this polymer has an excellent ability to adsorb pirimicarb with a removal percentage of 99.92 at pH = 7.54, initial pirimicarb concentration = 10.17 mg/L, polymer dosage = 840 mg/L, and contact time = 6.15 min. The detection of pirimicarb was performed by fluorescence spectroscopy at a concentration range of 0–50 mg/L, and a sensitivity of 15.808 a.u/mg and a limit of detection of 1.79 mg/L were obtained. Real samples with RSD less than 2 were measured using this chemosensor. Besides, the proposed chemosensor demonstrated remarkable selectivity by checking some other insecticides with similar and different molecular structures to pirimicarb, such as diazinon, deltamethrin, and chlorpyrifos.

A new water−soluble naphthalene diimide as a highly selective fluorescent chemosensor for Cu(II) ion: Synthesis, DFT calculations, photophysical and electrochemical properties

The highly selective, sensitive, and water-soluble fluorescent sensors are desideratum for optoelectronic, environmental, biological, and biomedical applications. An innovative fluorescence chemosensor, naphthalene diimide (3) with metal binding sites, was designed, synthesized and characterized. The chemosensor's optical, electrochemical, spectroelectrochemical, and morphological properties were investigated, and then the density functional theory (DFT) simulations were conducted. The selectivity of 3 for the metals Cu(II), Ag(I), Hg(II), Mg(II), Fe(III), Ca(II), Co(II), Zn(II), Pb(II) and Cd(II) were investigated through UV–visible and fluorescence spectroscopy techniques. 3 was highly selective and sensitive toward Cu(II) metal ions. The chemosensor can detect Cu(II) in water with a detection limit of 1.11 μM, which is lower than the WHO standard and has good repeatability. Further investigations through the IR, DPV, AFM, UV–visible and fluorescence spectroscopies, SEM, EDX and TEM techniques confirmed the binding capabilities of the 3 with Cu(II).

Phenoxazine-based fluorescence chemosensor for selective detection of cyanide

Purpose A highly selective cyanide phenoxazine-based fluorescence chemosensor POH was created to detect cyanide (CN) ions. Design/methodology/approach A malonitrile was added to a phenoxazine fluorophore to make this widely available chemosensor. By fluorescence spectroscopy, the sensor POH showed turn-off fluorescence emission for CN with 2:1 binding stoichiometry in CH3CN/H2O (90:10 v/v) medium. Findings The detection limits for CN were 9.8 × 10−9 M, which were much lower than WHO standards. NMR and FT-IR investigations backed up the suggested sensor POH mechanism. Originality/value The detection CN method should be applicable in a number of situations, where the CN anion for fresh water and drinking water has to be quickly and accurately analyzed. Graphical abstract

Chromene Carbohydrazide- Schiff Base as a Highly Selective Turn-Off Fluorescence Chemosensor for In3+ Ion and its Application.

A new 7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide design to synthesize a simple Schiff-base condition. The synthesized molecules' (probe L) photophysical properties were investigated in various solvent systems and solvent-poor-solvent assays. Probe L exhibits the absorbance band at 440nm and the emission band at 488nm in DMSO: H2O (7:3, v/v). Further, probe L shows selective turn-off emission recognition of In3+ ions in DMSO: H2O (7:3, pH = 7.4). By Job's plot and ESI mass analysis, probe L forms a 1:2 stoichiometry complex with an estimated association constant of 4.04 × 104 M- 2 with In3+ ions. Metal induces CHEQ (chelation-caused fluorescence quenching) to reduce the intensity of probe L's emission, and the estimated quenching constant was 4.52 × 104 M- 1. The limit of detection was found to be 5.93 nM; the time response of the sensor is instantaneous, and its reversible nature was confirmed using EDTA additions. Solid substrates (test strips) were designed and tested for fast, reliable, user-friendly, and real-time sensing of In3+ ions for on-site applications. The binding mechanism of probe L with In3+ ions was investigated using 1H NMR titration and DFT/TD-DFT studies.

A novel chromone Schiff base as Zn2+ turn-on fluorescent chemosensor in a mixed solution.

In this study, a novel fluorescent chemosensor 1 based on chromone-3-carboxaldehyde Schiff base was synthesized and featured through nuclear magnetic resonance (NMR) and mass spectra. Spectroscopic investigation indicated that the fluorescent sensor showed high selectivity toward Zn2+ over other metal ions and that the detection limit of 1 could reach 10-7 M. These indicated that 1 acted as a highly selective and sensitive fluorescence chemosensor for Zn2+ .

Starch/rhodamine 6G conjugate as a non-cytotoxic, effective, and selective fluorescent chemosensor for detection of Fe3+ ion

Iron is a crucial trace mineral vital for maintaining optimal human health and well-being. Despite being needed in small amounts, its importance cannot be overstated as it plays an important role in various physiological processes. In this research, we have developed a fluorescence probe utilizing starch functionalized with derivatives of rhodamine 6G to efficiently detect Fe3+ ions. This structure forms self-assembled starch/rhodamine 6G (RS0) fluorescent nanoparticles that exhibit strong fluorescence intensity under ultraviolet light. The ability of Fe3+ ions to increase the fluorescence of the RS0 probe enables the effective detection of Fe3+ ions. Importantly, this fluorescence increasing effect is specific to Fe3+ ions and remains unaffected by the presence of other metal ions. MTT assay against SH-SY5Y cells showed that RS0 was rather cytocompatible. Finally, SH-SY5Y cells were used to measure cell uptake and fluorescence imaging performances of RS0 which showed a good ability for live-cell fluorescence imaging.

Bodipy-based quinoline derivative as a highly Hg2+-selective fluorescent chemosensor and its potential applications

A highly efficient sensor has been successfully developed using quinoline-based BODIPY compounds (8-quinoline-4,4-difluoro-4-boro-3a, 4a-diazaindacene (C1) and 7-hydroxy-8-quinoline-4,4-difluoro-4-boro-3a, 4a-diazindacene (C2) to detect Hg2+ ions. The sensor C1 exhibits remarkable selectivity in detecting Hg2+ with a limit of detection 3.06 × 10-8 mol/L. The developed chemical sensors have shown stability, cost-effectiveness, ease of preparation, and remarkable selectivity towards Hg2+ ions compared to other commonly occurring metal ions. The total recovery of the sensor C1 can be achieved by using a 0.1 mol/L solution of KI. The proposed sensor C1 has been applied to determine Hg2+ in tap and distilled water, yielding excellent results. In addition, the binding mode of C1-Hg2+ and C2-Hg2+ complexes was a 1:1 ratio confirmed by mass spectra, Job’s plot, and DFT study. Moreover, the sensor C1 successfully applied for the biological studies results in negligible cytotoxicity, which demonstrates it can be used to determine Hg2+ in HT22 cells.

5-Aminoisophthalate-based kojic acid-appended bis-1,2,3-triazole: a fluorescent chemosensor for Cu2+ sensing and in silico study.

A new, easy-to-prepare, and highly selective fluorescent chemosensor, i.e., 5-aminoisophthalate-based kojic acid-appended bis-1,2,3-triazole, was synthesized from an alkyne of 5-aminoisophthalic acid and azido-kojic acid using Cu(i)-catalyzed click chemistry and then successfully characterized. The alkyne structure of 5-aminoisophthalic acid, 1, was supported by the single-crystal X-ray crystallographic data. The fluorescent probe 3 was found to be highly selective for Cu2+ ions supported by the Job's plot with a stoichiometric ligand : metal ratio of 2 : 1, exhibiting almost a two-fold enhancement in the emission intensity upon the addition of Cu2+ ions (0-25 μM) with a detection limit of 8.82 μM. A comparison with LODs from previously developed chemosensors for Cu2+ ions was also conducted. Reversibility analysis indicated that probe 3 could be used as both a reusable sensor and as a scavenger of copper ions. DFT calculations with the basis sets B3LYP/6-311G(d,p) and LanL2DZ were employed for geometrical optimizations of structures of the alkyne 1, azide 2, probe 3, and complex 3.Cu2+. Hirshfeld surface analysis revealed significant intermolecular interactions in compound 1. Additionally, molecular docking for the antimicrobial activity showed the better antibacterial efficacy of probe 3.

Isatin-Schiff base functionalized graphene oxide as a highly selective turn-on fluorescent probe for the detection of Pd(II) via photoinduced electron transfer pathway

We investigated the use of isatin-Schiff base functionalized graphene oxide (ISBGO) as a selective fluorescent chemosensor for the detection of palladium ions. Selectivity tests indicated that over 23 metal ions tested, ISBGO (λex = 340 nm, λem = 504 nm) showed the highest affinity for Pd(II), displaying a 10.1-fold enhancement. Also, interference tests proved that in the presence of both Pd(II) and other metal ions, there was still high fluorescence intensity and no considerable quenching occurred. According to DFT and TD-DFT calculations, photo-induced electron transfer (PET) is responsible for the turn-on response produced by the chemosensor. Coordination of Pd(II) with ISBGO in fact blocks PET from imine nitrogen of 3-iminoindolin-2-one moiety to the benzene ring, which in turn leads to a turn-on response. In addition, Job’s plot analysis and Benesi-Hildebrand approach suggest that ISBGO preferably forms a 1:1 complex with Pd(II) with an association constant of 1.020 × 105 M−1. Moreover, FT-IR spectroscopy and DFT study showed that amide oxygen and imine nitrogen of 3-iminoindolin-2-one moiety acted as binding sites of ISBGO. High sensitivity, fast response, great degree of sensitivity, short life time, low detection limit of 32 nM combined with high association constant (Kf) of 1.020 × 105 M−1 and increased fluorescence quantum yield (Φf) of roughly 1.5-fold in the presence of Pd (II), highlight the role of ISBGO as an excellent probe for sensing Pd(II) in aqueous solution.

New graphene oxide-loaded probe as a highly selective fluorescent chemosensor for the detection of iron ions in water samples using optical methods

A highly selective Graphene Schiff base Probe, GP chemosensor was synthesized by modification of functionalized graphene oxide with Naphthaldehyde-diaminobenzophenone Schiff base probe, NDABSB. The loading of the NDABSB on graphene oxide (GO) was carried out by ultrasonication method and characterized by FT-IR, PXRD, 1H NMR, EDX, TGA, Raman spectroscopy, and microscopic SEM techniques. All the characterization techniques validated the successful loading of the NDABSB on GO. The optical properties of GP were investigated by absorption and fluorescence titration studies, which revealed that GP displayed selective fluorescence sensing for Fe2+ and Fe3+ ions over other metal ions viz., Cr3+, Cd2+, Cu2+, Co2+, Mn2+, Ni2+, V3+, Li+, and Zn2+. The binding ratio was determined by Job's plot, and 2:1 stoichiometry was observed. The detection limit of GP for Fe2+ and Fe3+ was found to be 0.277 × 10−5 mol L−1 and 0.337 × 10−5 mol L−1, respectively. The lower detection limit of the GP for Fe2+ and Fe3+ ions proved its application in the sensing phenomenon and showed its sensitivity. Furthermore, density functional theory (DFT) and confocal fluorescence imaging studies were carried out to support the results of optical sensing experiments. The practical applicability of GP was investigated by examining iron content in different water samples.

Ultrasound-Assisted Synthesis of Chalcone: A Highly Sensitive and Selective Fluorescent Chemosensor for the Detection of Fe3+ in Aqueous Media.

The chalcone compound DHPO was synthesized through a chemical reaction between 1-(2-hydroxyphenyl)-ethanone and 3,4-dimethoxy benzaldehyde under ultrasound irradiation. The interaction between the DHPO compound and several metal ions was studied using fluorescence behavior, revealing that the chalcone function as a "turn on and turn off" switch fluorescent sensor, for selectively and sensitively detecting Fe3+ ions. The process of fluorescence quenching and complexation of DHPO with Fe3+ ion was further studied using methods such as Benesi-Hildebrand, Stern-Volmer plot, and job plot.

A multi responsive phosphonic acid based fluorescent sensor for sensing Fe3+, benzaldehyde and antibiotics

Herein, we report a multi responsive and selective fluorescent chemo sensor with anthracene as a fluorophore and phosphonic acid group as receptor (anthracene-9,10-diylbis(methylene)) diphosphonic acid (ANDP) for detecting Fe3+, benzaldehyde and few antibiotics. The sensor was characterised by single crystal X-ray diffraction and 1H NMR. ANDP could selectively and sensitively detect Fe3+ and benzaldehyde in DMSO-water with the detection limits of 5.09 µM and 39.8 µM respectively. 1H NMR, FT-IR and Fluorescence life time measurements suggests the interaction of Fe3+ with the sensor and the oxygen of phosphonic acid group is responsible for the interaction in both the sensing of iron ion and benzaldehyde. Mainly nitro group based antibiotics (NFZ, MDZ, FZD) and TCL sensitively quenched the fluorescence of the sensor with the detection limit of 2.07 µM, 1.25 µM, 1.19 µM and 0.66 µM. The quenching mechanism was further discussed and it was found that the photo induced electron transfer (PET) was responsible for the quenching of fluorescence intensity of ANDP. The HOMO and LUMO energies were estimated by DFT calculations.

The new coumarin derivative cyclotetraphosphazene fluorometric chemosensor with reversible, high selective and sensitive for Fe3+ ion detection

A new coumarin-based cyclotetraphosphazene molecule (OCCTP) that can show fluorescence and chemosensory properties has been designed and synthesized. For this purpose, the 7-hydroxy-3-(3,4,5-trimethoxyphenyl)coumarin (4) was synthesized.For the first time in this study, compound 4 which solid state structure and geometry were determined by using crystal X-ray structural analysis were crystallized in the orthorhombic Fdd2 space group. The purified compounds were structurally characterized by elemental analysis, NMR (1H, 13C and 31P) and FT-IR spectroscopy, and mass analysis. Photophysical and chemosensory properties of OCCTP against a range of analytes (various metal ions) were investigated by UV–vis and Fluorescent Spectrophotometer. As a result of fluorimetric studies, OCCTP was found to be a Turn-Off fluorescent chemosensor against Fe3+ ions. The limit of detection (LOD) of OCCTP for Fe3+ was calculated as 1.87 µM and its complex stoichiometry was determined as 1:2 (L/M) as a result of Job's plot. The reversibility study of the iron complex with EDTA showed that the free OCCTP chemosensor regenerated causing an increase in the fluorescence intensity of EDTA. The results showed that the newly synthesized coumarin-based cyclotetraphosphazene compound (OCCTP) can be used as a reversible, highly selective and sensitive fluorescent chemosensor (Turn- Off) which responds immediately against Fe3+ ions.

Pyrene based Schiff base ligand: A highly selective fluorescence chemosensor for the detection of Cu2+ ions

A Schiff base ligand L has been designed and synthesized by the condensation of 1′-Hydroxy-2′-acetonaphthonehydrazide with pyrene aldehyde for the detection of Cu2+ ions. The ligand was spectroscopically characterized by all possible techniques. Among different metal ions, Cu2+ ions give a tremendous enhancement of fluorescence intensity in 20% water with THF. The “Turn-On” fluorescence for Cu2+ ions utilizes the Photo-induced Electron Transfer (PET) mechanism. It has been observed that the presence of relevant cations and anions did not affect the probe's fluorescence intensity. The stoichiometric binding mode of the complex is confirmed using Job's method. The low detection limit and reversibility make it cost-effective.

Architecture of a functionalized SBA-15 (SBA-Pr-N-BFE) chemosensor for the detection of Fe3+ ions in aqueous media

SBA-Pr-N-BFE was designed as a chemosensor starting from mesoporous silica SBA-15, (3-aminopropyl)trimethoxy silane, and 1,2-bis(2-formylphenoxy)ethane (BFE), characterized by various techniques and applied as a selective fluorescent chemosensor. Photoluminescence (PL) spectroscopy has been employed to examine the sensing prowess of the functionalized SBA-Pr-N-BFE, which could selectively detect the Fe3+ ions in H2O over various metal ions; notable quenching in the fluorescence intensity was discerned after adding Fe3+ ions in H2O. Furthermore, the fluorescence studies established the linear correlation of fluorescence intensity of SBA-Pr-N-BFE and the concentration of Fe3+ ions with a detection limit of 1.209 × 10-6 M.

Shining light on fluoride detection: a comprehensive study exploring the potential of coumarin precursors as selective turn-on fluorescent chemosensors.

In this study, we report a fluoride chemosensor based on the use of a non-fluorescent pre-coumarin, compound 1. This compound undergoes selective fluoride-triggered formation of coumarin 2, with a concomitant turn-on fluorescence signal. Although compound 1 exists as a mixture of alkene isomers (2 : 1 in favor of the E isomer), only the minor Z-isomer undergoes cyclization. Nonetheless, comprehensive computational and experimental studies provide evidence that in situ isomerization of E-1 to Z-1, followed by fluoride-triggered phenolate evolution and intramolecular cyclization, facilitates the generation of coumarin 2 in high yield. Moreover, this system is an effective turn-on fluorescence sensor for fluoride anions, which displays outstanding selectivity (limited response to other commonly occurring analytes), sensitivity (lowest reported limits of detection for this sensor class), and practicality (works in solution and on paper to generate both fluorometric and colorimetric responses). Ongoing efforts are focused on expanding this paradigm to other pre-coumarin scaffolds, which also undergo analyte-specific coumarin formation accompanied by turn-on fluorescence.

Self-Associated 1,8-Naphthalimide as a Selective Fluorescent Chemosensor for Detection of High pH in Aqueous Solutions and Their Hg2+ Contamination.

A novel diamino triazine based 1,8-naphthalimide (NI-DAT) has been designed and synthesized. Its photophysical properties have been investigated in different solvents and its sensory capability evaluated. The fluorescence emission of NI-DAT is significantly impacted by the solvent polarity due to its inherent intramolecular charge transfer character. Moreover, the fluorescence emission quenched at higher pH as a result of photo-induced electron transfer (PET) from triazine moiety to 1,8-naphthalimide after cleaving hydrogen bonds in the self-associated dimers. Furthermore, the new chemosensor exhibited a good selectivity and sensitivity towards Hg2+ among all the used various cations and anions in the aqueous solution of ethanol (5:1, v/v, pH = 7.2, Tampon buffer). NI-DAT emission at 540 nm was quenched remarkably only by Hg2+, even in the presence of other cations or anions as interfering analytes. Job's plot revealed a 2:1 stoichiometric ratio for NI-DAT/Hg2+ complex, respectively.

Highly selective turn-on fluorescent chemosensor for the detection of Cr (III) ion in drinking water

An effective and simple carbazole-based Schiff base (CrbPy2) chemosensor for selective recognition of Cr(III) was designed and synthesized. The molecular structure of CrbPy2 was confirmed by NMR and FT-IR spectroscopies, its crystal structure was investigated by XRD analysis and the results were in good agreement with the DFT calculations. The CrbPy2 probe showed high selectivity toward Cr3+ ions in THF/H2O (95/5%) solution. Adding Cr3+ ions to CrbPy2 dilute solution induced a naked eye color change from colorless to yellow accompanied with a fluorescence turn-on. The proposed sensing mechanism was related to chelation-enhanced fluorescence (CHEF) process. The stoichiometry ratio of CrbPy2-Cr3+ complex is 1:1 with an association constant exceeding 3 × 105 M-1. The study of the sensing properties in different pH showed that CrbPy2 can tolerate the detection of Cr3+ ions in a pH range from 6 to 8. The chelating sites of the chemosensor and the coordination geometry of the complex were determined using 1H NMR titrations and MEP calculations. The detection was completed within 2–3 min and the detection limit reaches 1.08 μM. The linear recognition range of Cr(III) is from 1.08 μM to 4 μM making CrbPy2 a suitable probe for real-time identification of unsafe Cr3+ concentration in drinking water.

AIE-active phenothiazine based Schiff-base for the selective sensing of the explosive picric acid in real water samples and paper-based device

A highly selective and sensitive AIE fluorescent chemosensor based on phenothiazine and ethylene diamine was synthesized (DPTZ-SB) for the exclusive detection of picric acid (PA). Interestingly, DPTZ-SB can sense PA exclusively over five other competitive explosives, due to the specific complexation ability of DPTZ-SB towards PA. For the better mechanistic understanding, Stern-Volmer, Modified Stern-Volmer and Job’s plot were employed, which showed the limit of detection and binding constant to be 0.2 ppb and 4.05 × 1010 M−1, respectively, and the stoichiometric ratio of DPTZ-SB:PA as 1:2. The values are promising as compared to the AIE fluorophores reported for PA sensing recently. The sensing mechanism was elucidated using DFT studies and 1H NMR titration experiment, which revealed the active involvement of the imine groups of the Schiff base in the complexation process. Furthermore, in order to broaden the applicability, the probe DPTZ-SB was applied in real water samples obtained from the local river, lake and tap water. Interestingly, a paper based fluorescent sensor was devised by embedding DPTZ-SB on the filter paper and was analyzed by a handheld UV lamp. Under UV light illumination, the paper-based sensor exhibited prominent fluorescence quenching in the presence of PA, which can be conveniently visualized. Moreover, the color-scanning application available in smart phones was coupled with the paper-based sensor to quantitate the scanometric assays. On a parallel note, DPTZ-SB showed excellent aggregation induced enhanced emission (AIEE) property. In fact, a 9.4-times enhancement in the photoluminescence (PL) intensity was noted for a 90:10 H2O:DMF of DPTZ-SB as compared to that in pure DMF. Therefore, the multifaceted applicability of the Schiff base has been explored, particularly in the fields of PA explosive detection device in real life samples and AIEE.

Highly specific and selective fluorescent chemosensor for sensing of Hg(II) by NH-pyrazolate-functionalized AIEgens

Luminescent organic molecules are of important realistic significance to the human health and ecological environment due to their fascinating applications. Here we report the design and synthesis of luminescent organic-molecules by introducing two or four NH-pyrazolate groups as mercury-binding moieties to aromatic cores. Interestingly, the new aromatic tetraphenylene-bridged multi–NH–pyrazoles exhibit strong fluorescence in both aggregate and solid state and constitutes highly selective proof-of-concept luminescent sensor for Hg(II) ion among various competitive transition-metal ions in both organic and mixed solutions via metal-nitrogen binding. Especially, the present sensor including two NH-pyrazolyl groups showed an extremely high sensitivity with low limit of detection of 7.26 and 3.67 nM. The proposed design strategy provides a wide scope for the construction of unique turn-on sensors with substantial potential in the sense of heavy metal pollution in enviromental water samples.