Sensitive Fluorescent Chemosensor Research Articles

A smartphone-integrated bimetallic ratiometric fluorescent probe for specific visual detection of tetracycline antibiotics in food samples and latent fingerprinting

Designing and preparing highly sensitive and accurate fluorescent chemosensors for monitoring tetracycline antibiotics remains a challenge. Herein, a fluorescent chemosensor based on lanthanide metal-organic frameworks (Ln-MOFs) is proposed to realize high-precision monitoring by adjusting the ratio of lanthanide ions. Ln-MOFs with good aqueous stability were prepared by a solvothermal method using Eu3+, Tb3+ and the ligand 4,4′,4″-s-triazine-2,4,6-triyltribenzoic acid (H3TATB) in DMF/NMP/H2O. The Ln-MOFs could recognize oxytetracycline (OTC) and doxycycline (DOX), and the detection limits of OTC and DOX were as low as 8.6 and 4.8 nM, respectively. In particular, Eu(1.4 μM)-Tb-MOF sensors were used for visual detection of OTC and DOX in combination with smartphones with detection lines as low as 9.8 nM and 14.2 nM, respectively. Meanwhile, Eu-MOF, Tb-MOF and Eu(1.4 μM)-Tb-MOF can be used for latent fingerprint (LFP) visualization, demonstrating their potential applications in the field of criminal case investigation. The developed probes were successfully applied to determining OTC and DOX in milk, beef and pork with recoveries ranging from 92.0 % to 109.63 % and relative standard deviations (RSDs) ranging from 1.83 % to 4.56 %. Eu(1.4 μM)-Tb-MOF is believed to utilize its lanthanide metal ion coordination and photoinduced electron transfer (PET) mechanism to achieve highly selective and accurate OTC and DOX detection, which is supported by experimental and density functional theory (DFT) calculations.

A highly selective and sensitive quinoline-based fluorescent turn-off chemosensor for the detection of picric acid

A simple turn-off quinoline-based fluorescent chemosensor, 1-(6-amino-2-methyl-4-phenylquinolin-3-yl)ethan-1-one (QN) has been developed, synthesized, and characterized by various spectroscopic methods. This probe is selective for the sequential recognition of picric acid (PA), using a fluorescent turn-off method. QN exhibits a broad emission band at 504 nm, but fluorescence quenching occurs upon the addition of picric acid over other nitro compounds. The binding stoichiometric ratio between QN and picric acid was calculated to be 1:1 through Job's plot analysis, and the binding constant was determined. The limit of detection towards picric acid was found to be 9.33 µM. Further, the mechanistic approach for binding has been investigated by spectroscopic methods like 1H NMR titration, FT-IR studies, and density functional theory (DFT) studies.

Pyrene‐based ratiometric fluorescent chemosensor for sensitive detection of hypochlorite in a perfect aqueous solution

AbstractWe synthesized a pyrene‐based sensitive fluorescent chemosensor, TPA‐Cl ((E)‐N,N,N‐trimethyl‐2‐oxo‐2‐(2‐(pyren‐1‐ylmethylene)hydrazinyl)ethan‐1‐aminium chloride), to detect hypochlorite in a perfect aqueous solution. TPA‐Cl showed high selectivity for hypochlorite through fluorescence color change from sky blue to blue. The detection limit for hypochlorite was calculated as 0.27 μM, which is a quite low value. Moreover, the presence of other anions or ROS hardly hindered the sensing of hypochlorite by TPA‐Cl. Furthermore, TPA‐Cl could be applied successfully as a test kit for the simple recognition of hypochlorite. Surprisingly, TPA‐Cl is the first pyrene‐based fluorescent chemosensor that can detect ClO− by using the TPA‐Cl‐coated test kit. Moreover, TPA‐Cl could achieve the quantification of ClO− in various environmental water samples. The hydrolytic cleavage and oxidation mechanism of TPA‐Cl by hypochlorite was elucidated through UV–vis and fluorescent spectroscopy, 1H NMR titration, ESI‐MS analysis and DFT calculation.

Synthesis of biscarbazole derivative, detection of the “on-off” sensor property of Cu2+ by fluorimetry, and anti-cancer evaluation

Biscarbazole derivative probe (6) (Z)-2-(3-(((9-heptyl-9H-carbazol-3-yl)methylene)amino)-9H-carbazol-9-yl)ethan-1-ol containing an imine group, which is a sensitive and selective fluorescence chemosensor, was designed and synthesized for the effective evaluation of Cu2+ metal ion levels. The synthesized compounds were characterized using 1H NMR, 13C NMR, FT-IR, and MALDI-TOF MS (for compound 6) spectroscopic data. The interaction model between probe 6 and Cu2+ was determined by combining fluorescence methods, 1H NMR titration, Job’s plot, and theoretical calculations. For probe 6, the fluorogenic recognition of Cu2+ was investigated by fluorescence spectroscopy, and the optical changes caused by Cu2+ ions were carried out in ACN/H2O (50:50) solution at pH 7.0. Fluorescence probe 6 was found to “turn-off” its fluorescence in the presence of paramagnetic Cu2+ ions. Probe 6 was determined to have a rapid response within 40s and showed a fluorescence response to Cu2+ with a low detection limit of 0.16 μM. Additionally, in vitro anticancer activity and cell imaging studies of probe 6 against the prostate cell line (PC-3) were performed.

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 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+ .

Rapid synthesis of a BODIPY derivative serving as a highly selective and sensitive fluorescence chemosensor for Hg2+ ion detection

A 2-amino-1,3-propanediol-modified BODIPY was synthesized in 6 hours, exhibiting high selectivity and a fourfold emission increase with Hg2+ ions in polar solvents.

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.

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.

Novel Crown Ether Amino Acids as Fluorescent Reporters for Metal Ions.

Unnatural amino acids with enhanced properties, such as increased complexing ability and luminescence, are considered to be highly attractive building blocks for bioinspired frameworks, such as probes for biomolecule dynamics, sensitive fluorescent chemosensors, and peptides for molecular imaging, among others. Therefore, a novel series of highly emissive heterocyclic alanines bearing a benzo[d]oxazolyl unit functionalized with different heterocyclic π-spacers and (aza)crown ether moieties was synthesized. The new compounds were completely characterized using the usual spectroscopic techniques and evaluated as fluorimetric chemosensors in acetonitrile and aqueous mixtures in the presence of various alkaline, alkaline-earth, and transition metal ions. The different crown ether binding moieties as well as the electronic nature of the π-bridge allowed for fine tuning of the sensory properties of these unnatural amino acids towards Pd2+ and Fe3+, as seen by spectrofluorimetric titrations.

Naphthalene-based silica nanoparticles as a highly sensitive fluorescent chemosensor for mercury detection in real seawater

Mercury is considered one of the most harmful contaminants threatening human lives and the aquatic environment. Naphthalene and its derivatives have excellent fluorescence properties that can be exploited for mercury (Hg2+) sensing applications. Herein, we covalently attached naphthalene with silica nanoparticles (NSPs) using one-pot multiple steps synthesis approach. The NSPs were characterized by 1H NMR, FTIR, TGA, FESEM, and UV–vis spectroscopy. The fluorescent properties were analyzed in deionized water under normal and UV-light illumination. Finally, the synthesized NSPs were investigated as a chemosensor for Hg2+ ions detection in real seawater samples via photoluminescence (PL) spectroscopy. The results indicate that the fluorescence properties of NSPs (20 ppm) were quenched upon Hg2+ addition in the range from 0 to 50 ppm. The studies demonstrated that NSPs acted as a potential host for Hg2+ ions compared to other interfering ions present in the seawater sample. The NSPs chemosensor provides a linearity range (5 – 1000 ppb) and limit of detection LOD (1 ppb; 5 nM), even below the values suggested by US EPA drinking water safety regulations, which indicates its potential utilization for mercury sensing in seawater environments.

A sensitive ratiometric fluorescent chemosensor for visual and wearable mercury (II) recognition in river prawn and water samples

A novel ratiometric fluorescent probe p-RPT was prepared with triphenylamine and a rhodamine derivative. The probe displays high sensitivity and selectivity for Hg2+, which was applied in real water sample detection and biologic cell imaging. Hydrogel-coated paper sensors were fabricated with p-RPT, which displayed fluorescent colour change upon Hg2+ ion contact with a detection limit of 1.2 × 10-8 M (∼10 ppb). In addition, flexible fluorescent p-RPT gloves were developed for visible and wearable Hg2+ detection and applied to detect mercury (II) in river prawn samples. In summary, the p-RPT probe not only shows great potential in mercury (II) detection for food and water, but also provides a new perspective for wearable sensing apparatus.

Synthesis of 2D fluorescent polyaniline derivatives as multifunctional fluorescent chemosensor

AbstractPolyaniline (PANI) has been widely studied and applied due to its easy‐to‐obtain raw materials, excellent electrochemical performance and high environmental stability. Here, we present a general synthetic strategy for preparing two‐dimensional (2D) fluorescent PANI derivatives. The double bonds are used as a conjugated spacer between benzene rings in PPED and PPBA. The work breaks through the limitation of PANI derivatives are non‐emissive in solutions. The fluorescence quantum yields (Фf) of PPED and PPBA are 2.5% and 1.5%, respectively. PPED and PPBA show highly selective and sensitive detection of iron ion (Fe3+), copper ion (Cu2+) and hydrochloric acid (HCl). It is worth noting that the detection limit of PPED for Fe3+ is 35 nM. In addition, the theoretical study indicates that the introduction of double bonds in PPED and PPBA greatly enhances their conjugation extent. The results demonstrate that we provide a powerful method for the preparation of highly sensitive fluorescent chemosensors based on 2D PANI derivatives.

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.

A Phenothiazine‐Thiophene‐linked Chalcone as a Highly Sensitive Fluorescent Chemosensor for Ag+ Ions

AbstractA novel Phenothiazine‐Thiophen Chalcone (PTC) sensor exhibit selective fluorescent recognition of Ag+ ions over other potential influencing metal ions. A turn off fluorescence was observed with addition of Ag+ ion which revealed through naked eye detection with red to colorless solution after addition of Ag+ ion. The optical sensing activities were investigated with UV‐Visible and fluorescence spectroscopic techniques in acetonitrile/water (6 : 4, v/v) mixture. The ligand PTC showed quenching in absorbance and fluorescence with increasing addition of Ag+ ions that related to the static quenching due to ground state complex formation. The sensor PTC established a lowest detection limit of about ∼10−8 m and good binding equilibrium. The binding and optical sensing mechanism of PTC with Ag+ was evaluated using FT‐IR, NMR, ESI‐MS and optical spectrum. The surface morphology of the probe and its ensemble was investigated by using SEM and EDAX analysis. Also the environmental applications have shown that the results of PTC have the greatest potential in testing using different water samples.

An easy to make Hg(II) complex as a selective and sensitive fluorescent turn-on chemosensor for iodide in an aqueous solution based on metal ion displacement mechanism

• The rationally designed receptor forms Hg(II) complex easily. • The Hg(II) complex senses I − via turn-on fluorescent in aqueous solution. • The mechanism of sensing involves displacement of metal ion from the complex. • This complex exhibited many advantages than similar in-situ generated Hg(II) complexes. A simple Schiff base ligand ( L ) bearing 3,5-dibromo-2-hyrdoxybenzaldehyde fluorophore moiety has rationally been designed, synthesized and characterized. The Hg(II) complex of L has been synthesized by simply stirring a mixture of L and HgCl 2 in ethanol at RT and the resultant non-fluorescent complex HgL is found to detect iodide ion selectively, with a turn-on fluorescence in H 2 O:DMSO (1:1 v/v) medium. The detection of iodide is performed via the metal ion displacement mechanism with a 1:2 (Probe:Iodide) stoichiometry and binding constant of 1.51x10 4 M −1 . The results indicated that novel HgL complex showed rapid response towards iodide ion with a limit of detection (LOD) as low as 60 nM. Moreover, the sensing mechanism of iodide by the complex is theoretically supported by density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. In addition, estimation of iodide in real water samples, table salt and urine sample demonstrate the practical value of the probe.

Highly sensitive and selective coumarin-based fluorescent chemosensor for Cu2+ detection

Our research resulted in the development of a new synthetic semicarbazide derivative based on coumarin (CS1) as a fluorescent chemosensor for Cu2+ detection. The probe demonstrated an “on–off” fluorescence response at 492 nm in the presence of Cu2+ with a detection limit of 5.80 ± 0.01 nM. A copper existence diminished visible fluorescence under UV light. The binding ratio of the CS1 probe to Cu2+ was found to be 1:1, resulting from the ESI-MS, Job’s method, and density functional theory (DFT) calculation. The probe exhibited acceptable Cu2+ sensitivity, within nanomolar scale, and selectivity, even in the presence of other important metal ions. Apart from the laboratory study, CS1 was also capable of real water sample measurement with great accuracy.

Adenosine triphosphate (ATP) and zinc(II) ions responsive pyrene based turn-on fluorescent probe and its application in live cell imaging.

A novel highly selective and sensitive turn-on fluorescent chemosensor PCE to recognize Zn2+ has been developed. The sensor PCE displays a remarkable fluorescent enhancement at 456nm (λex=340nm) with Zn2+ without the interference of other biologically important relevant metal ions in aqueous acetonitrile solution. Job's plot and mass spectral studies divulge such the interaction of PCE by Zn2+ was 1:1 binding stoichiometry. The association constant and detection limit of PCE to recognize Zn2+ was found to be 0.948×104M-1 and 4.82×10-7M respectively. The nature of turn-on fluorescence sensor was supported by TD-DFT calculations. And the synthesized probe PCE was able to image intracellular Zn2+ in living cells using confocal imaging techniques. PCE-Zn ensemble showed the remarkable fluorescence enhancement with ATP selectively among other biologically important phosphates. 31P NMR experiments suggesting that the triphosphates unit of ATP is intact with the PCEZn. PCE-Zn ensemble can be utilized for monitoring ATP in live cells.

Synthesis of new anthracene-substituted calix[4]triazacrown-5 as highly sensitive fluorescent chemosensor and extractant against hazardous dichromate anion.

A new fluorogenic anthracene functionalized calix[4]triazacrown-5 (Ant-AzClx) was successfully synthesized using a simple Schiff's base reaction. The 1 H-NMR, 13 C-NMR, ESI-MS, and elemental analysis techniques were performed to characterize its structure. Excited at 370 nm, Ant-AzClx reveals excimer emission at 418 nm. Therefore, its anion binding properties were investigated against F- , HCO3 - , H2 PO4 - , NO3 - , Cr2 O7 2- , and SO4 2- ions. When hazardous dichromate anion was introduced into medium, the fluorescence intensity of Ant-AzClx was markedly quenched. The binding constant, stoichiometry, the detection limits and Stern-Volmer equation for the complex formed between Ant-AzClx and Cr2 O7 2- ion were determined. Furthermore, the 1 H-NMR technique was also performed to assess the mechanism of the complex (Ant-AzClx@Cr2 O7 2- ). Apart from its excellent fluorescent chemosensor properties for selective and sensitive recognition of Cr2 O7 2- ion, Ant-AzClx was used as an efficient extractant towards dichromate anion. The extraction results indicated that Ant-AzClx exhibited high extraction capability, leading to it being a promising extractant for the removal of dichromate anions from water.

Highly Selective and Sensitive Colorimetric and Fluorescent Chemosensors for Rapid Detection of Cyanide Anions in Aqueous Medium: Investigation on Supramolecular Recognition of Tweezer‑shaped Salophenes.

Three tweezer‑shaped salophenes having catechols (1), phenols (2) and anisoles (3) units in conjunction to the dipodal Schiff bases have been applied for the optical sensing of cyanide (CN¯) ions in CH3CN-H2O (7:3) as solvent of choice. Among them, compounds 1 and 2 recognized CN¯, relying on distinct color and spectral changes. They are easy-to-use probes that exhibit extremely high sensitivity (limit of detection = 1-10 nM), rapid response (5s) and excellent selectivity. Moreover, the visual detection and concentration determination of CN¯ by solution test kits of both sensors are the advantages for the practical applications. Based on the fluorescence and NMR spectroscopy, as well as the OH¯ and reversibility experiments, the explicit effect of hydroxyl groups on sensing and as well the different recognition of 1 and 2 toward CN¯ ions was proved. While probe 1 senses CN¯ via deprotonation, probe 2 recognizes it through an intramolecular aldimine condensation cyclization, leading to formation of anions of dihydroxyquinoxaline 4. This chemodosimetry is being reported for the first time in a Schiff's base. Furthermore, the similarity of fluorescence and NMR responses of 2 and 4 toward CN¯ supports the proposed process.