Reversible Fluorescent Sensor Research Articles

A reversible fluorescent sensor for continuous detection of fluoride ion and trace water in chemical reagents

Continuously monitorable fluorescence sensors can provide fast, immediate, in-field detection of analytes without tedious process. A simple fluorescent sensor (BN) constructed from naphthol Schiff base was developed for reversible monitoring of F- and trace water. Sensor BN showed specific selectivity toward F- over other anions giving rise to a fluorescence “turn-on” response. After added F-, the BN solution caused a dramatically observable color change from non-fluorescence to blue-green, and the limit of detection reached 78.5 nM. The Job’s and 1H NMR analysis confirmed that the recognition mechanism could be concluded to F- caused deprotonation of sensor BN by hydrogen bonding interaction. Moreover, the deprotonated form BN∙F obtained by using F- was acted as excellent sensitivity sensor for trace water detection with instant response through reprotonation. After addition of trace water, the emission color and spectral signal of BN∙F reverted to the original BN sate with the limit of detection of 0.0011 %. The reversible detection characteristic was conducive to the development of an inkless writing and encryption device. And importantly, BN∙F was utilized as a promising fluorescent sensor in the quantitative determination of water content in routinely chemical reagents.

A Simple Live Cell Imaging "Turn-On" Fluorescence Probe for the Selective and Sensitive Detection of Aqueous Hg2+ Ions.

A simple, efficient, and reversible fluorescent sensor probe, PBA (2,6-dimethyl pyrone barbituric acid conjugate), comprised of a pro-aromatic donor conjugated with a barbituric acid, was developed for the detection of highly toxic mercuric ions. The probe showed high selectivity and "Turn-On" fluorescence response towards Hg2+ among various metal cations such as Na+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, and Pb2+, in both homogeneous and microheterogeneous micelle medium sodium dodecyl sulphate (SDS). The binding stoichiometry, limit of detection (LOD), and binding constant for the PBA-Hg complex were determined. The mechanism of binding was ascertained using the N,N'-dimethylbarbituric acid conjugate of 2,6-dimethylpyran (PDMBA), where no binding interaction by deprotonation is possible. In the presence of cysteamine hydrochloride and trifluoroacetic acid (TFA), the complexation of Hg2+ with PBA was demonstrated to be reversible, indicating its potential for the development of reusable sensors. Moreover, the practical applicability of PBA in monitoring Hg2+ in living cells was also evaluated.

Tuning of distinguished fluorescent responses to methylmercury and Hg2+ ions: Selective detection of methylmercury over Hg2+ ions by fluorescent sensor using micelle system

Although CH3Hg+ is highly toxic, reversible fluorescent sensors for detecting CH3Hg+ over Hg2+ are rare. In this study, we synthesized a reversible fluorescent sensor (1) based on tryptophan amino acid and 6-membered cyclic amine as an electron-donating unit of the fluorophore for turn-on monitoring of Hg2+ in H2O and developed a fluorescent sensing method for selective sensing CH3Hg+ over Hg2+ using 1 and the micelles with a different surface charge. 1 in triton X-100 (TX-100) micelles differentiated between CH3Hg+ and Hg2+ by fluorescent response types (turn-on vs red-shifted emission), whereas 1 in cetyltrimethylammonium bromide (CTAB) micelles detected only CH3Hg+ among 16 metal ions by turn-on response. 1 in the micelles exhibited remarkable detection ability for CH3Hg+ such as ultrafast response (<30 s), high sensitivity and/or selectivity for CH3Hg+, low detection limits (107 nM), and large enhancement of the fluorescence. We proposed the plausible binding mode of 1 in the micelles for selective sensing CH3Hg+ based on fluorescence and NMR and IR study. The 6-membered cyclic amine group of the fluorophore part of 1 might play a critical role to distinguish between CH3Hg+ and Hg2+ by fluorescent response types in TX-100 micelles. 1 detected sensitively Hg2+ and CH3Hg+ in live cells through significant enhancement of green and red fluorescence. 1 with and without the micelles successfully quantified CH3Hg+ and Hg2+ in groundwater and tap water. The combination of the sensor with the micelles provided a selective detection of CH3Hg+ over Hg2+ or distinguished between CH3Hg+ and Hg2+ by fluorescent response types.

A quinolimide-based reversible fluorescent sensor for Cu2+ and S2− and its applications

A quinolimide-based reversible fluorescent sensor QPC with carboxamidoquinoline as the receptor was prepared for the relay recognition of Cu2+ and S2−. QPC displayed the high selectivity and anti-interference ability to Cu2+ through the 1:1 binding mode. Subsequently, the selectively sensing S2− with the QPCCu2+ complex gave a remarkable recovery of the emission. The LODs of QPC and its Cu2+ complex for Cu2+ and S2− were calculated to be 47.8 nM and 0.178 µM, respectively. Moreover, QPC and its Cu2+ complex had the satisfactory recoveries 93.5–105.8% for Cu2+ and 97.7–104.0% for S2− in water samples, and exhibited low cytotoxicity, which enabled them to image Cu2+ and S2− in yeast cells.

Solvent directed fluorometric discrimination of Cu2+ and Ni2+ ions by a quinoline-based glucopyranosyl derivative

The reversible fluorescence sensor 1 has been reported for the discrimination of metal ions in aqueous medium after excitation at a higher wavelength. Sensor 1 showed specific sensing properties towards Cu2+ and Ni2+ in aqueous solutions of DMSO and CH3CN. The discrimination of Cu2+ and Ni2+ions was carried out by controlling the testing media. Sensor 1 exhibited high selectivity and excellent sensitivity (LOD: 0.17 µM for Cu2+ and 0.18 µM for Ni2+) towards Cu2+ and Ni2+ in two different analytical techniques (absorbance and fluorescence). The 1:1 complexation for both Cu2+ and Ni2+ was established from Job plots and ESI-mass spectra of the complexes. Model compound 2 and FTIR spectroscopy were used to know the binding mechanism of sensor 1 with Cu2+ and Ni2+ ions. Finally, DFT calculations were performed to establish the binding mode of 1 with Cu2+ and Ni2+.

A novel phenolphthalein-based fluorescent chemosensor for pyrophosphate detection via an Al3+ displacement approach in real samples and living cells

Herein, we report a new phenolphthalein appended Schiff base (PASB) as reversible fluorescent sensor for the detection of pyrophosphate (PPi) ions through the metal displacement mechanism. PASB showed sensing exclusively toward Al3+ ions in DMF/H2O (v/v = 1/4, pH 5.5) solution, which resulted in a significant fluorescence enhancement at 540 nm. The 1: 2 binding stoichiometry for the complex formation between PASB and Al3+ was confirmed by Job’s plot and mass spectroscopic studies. Moreover, a solution of the in situ formed PASB–Al3+ complex displayed a high selectivity to PPi. The addition of PPi to PASB-Al3+ ensemble significantly quenched its fluorescence. Thus, a dual response was established based on “Off–On–Off” strategy for detection of both Al3+ and PPi. The detection limit is 5.86 nM and 26 nM for Al3+ and PPi, respectively. On this basis, we use PASB to detect Al3+ in food samples. Furthermore, PASB was successfully applicable to detect Al3+ and PPi for intracellular imaging in Human liver cancer cells.

A smart TP-FRET-based ratiometric fluorescent sensor for bisulfite/formaldehyde detection and its imaging application

Bisulfite (HSO3−) and formaldehyde (FA) are hazardous environmental pollutants that pose serious risks to human health. Herein, we report for the first time a novel TP-FRET-based TP-ratiometric reversible fluorescence sensor NPXH, which is based on combining TP naphthalimide fluorophore with a deep red-emitting xanthene fluorophore via a nonconjugated linker, for reversible detection of bisulfite/formaldehyde. In presence of HSO3−, NPXH shows a significant ratio enhancement (∼6-fold) in I535/I630, ultra-fast response (less than 8 s) and super low detection limit (7.48 nM). In addition, the fluorescence signal of NPXH is easily and rapidly recovered by FA within 1 min. More impressively, NPXH has shown excellent detection capability in food and water samples and has been successfully applied to HSO3−/FA detection in liver tissue, zebrafish and mice.

A rhodamine-based fluorescent sensor for selective detection of Cu2+ in aqueous media: Synthesis and spectroscopic properties

Two new chemosensors, rhodamine B derivative bearing 3-formyl-6-nitrochromone (L1) and 3-formyl-6-methylchromone (L2) units were designed and synthesized using microwave irradiation for the selective detection of Cu2+ in aqueous media. Copper triggers the formation of highly fluorescent ring-open spirolactam. The fluorescence intensity was remarkably increased upon the addition of Cu2+ within a minute, while the other metal ions caused no significant effect. More importantly, the resulting complexes can be used as a reversible fluorescence sensor for CN−. The recognition ability of the sensors was investigated by fluorescence titration, Job’s plot, 1H NMR spectroscopy and density functional theory (DFT) calculations.

Bioinspired fluorescent dihydroxyindoles oligomers

In this paper we report the desgin and synthesis of dihydroxyindoles oligomers based reversible fluorescence sensor. We find dihydroxyindoles-2-carboxylic acid derived oligmer (P-DHICA) has the highest selectivity and sensitivity for Cu2+ detection. This work provide a highly efficient, environmentally friendly biosensor for potential use in medical testing.

Superhydrophobic Silica Aerogels Encapsulated Fluorescent Perovskite Quantum Dots for Reversible Sensing of SO2 in a 3D-Printed Gas Cell.

Recently emerging perovskite quantum dots (PQDs) with several excellent optical properties, such as quantum efficiency, narrow band emission, and tunable emission wavelength, have promising applications in solar cells and light emitting diodes. However, relatively rare applications of PQDs can be found in the field of sensing, mainly due to the very easy degradation of PQDs upon exposure to water or ambient humidity. In this work, for the first time CH3NH3PbBr3 PQDs were encapsulated into superhydrophobic silica aerogels (AGs) to protect PQDs from being degraded by water. The synthesized PQDs@AGs not only maintain the strong fluorescence emission activity of PQDs but also show excellent stability in the presence of water. Additionally, PQDs@AGs have abundant pores making them very suitable for gas sensing. For improving sensing performances, 3D-printing technology is introduced into gas cell design and fabrication for the first time. Finally, a novel, sensitive, selective, and reversible fluorescence sensor for SO2 gas based on the PQDs@AGs functional material and the 3D-printed gas cell has been developed.

A new ‘turn-on’ and reversible fluorescent sensor for Al3+ detection and live cell imaging

Herein, we report a new benzothiazole-based azomethine receptor L as a reversible fluorescent sensor for the selective detection of Al3+ in buffered aqueous methanol (20 mM HEPES, pH = 6.0, 50% (v/v) CH3OH).

A rhodamine-based sensor for Hg2+ and resultant complex as a fluorescence sensor for I−

A rhodamine-based sensor displays a quick response for Hg2+. The resulting complex can act as a reversible fluorescence sensor for I−.

A reversible fluorescent chemosensor for the rapid sensing of CN− in water: utilization of the intramolecular charge transfer blocking

A reversible fluorescent sensor combines naphthyridine groups as signaling subunits and the presence of the active hydrogen of the primary amine confers the recognition capacity toward cyanide ions in water.

A highly selective fluorescent sensor for Al³⁺ and the use of the resulting complex as a secondary sensor for PPi in aqueous media: its applicability in live cell imaging.

An easy-to-make salicylimine (L) bearing an "O-N-O"-coordination site was used as a highly selective fluorescent sensor for Al(3+) and PPi in aqueous solution. Sensor L showed a significant fluorescence enhancement in the presence of Al(3+) over other competitive metal ions. It works based on the Al(3+)-induced formation of a 1 : 1 L-Al(3+) complex, producing a chelation-enhanced fluorescence effect, the fluorescence quantum yield reached 0.59. This L-Al(3+) ensemble is a subsequent fluorescent sensor for PPi due to the strong attraction between Al(3+) and PPi, it can selectively discriminate PPi overcoming the interference of the biological competitors including PO4(3-), ADP and ATP at physiological pH. L and L-Al(3+) exhibit high sensitivity and selectivity for Al(3+) and PPi, the detection limits were found to be as low as 2.94 × 10(-8) M and 2.74 × 10(-7) M, respectively. It was further confirmed that sensor L had potential practical applications through mapping of Al(3+) in live cells.

A turn-on and reversible fluorescence sensor with high affinity to Zn2+ in aqueous solution

A new simple receptor 1 based on aminosalicylimine was prepared. It exhibited an ‘off–on fluorescence type’ mode with high sensitivity in the presence of Zn2+. In particular, this chemosensor could clearly distinguish Zn2+ from Cd2+. Also, it could be a reusable chemosensor because the addition of EDTA quenched the fluorescence of the Zn2+-2·1 complex. Furthermore, receptor 1 had a sufficiently low detection limit (68nM) in aqueous solutions, which implies that 1 could sense the nanomolar concentration of Zn2+. Therefore, this sensor has the ability to be a practical system for the monitoring of Zn2+ concentrations in aqueous samples.

Novel reversible and selective nerve agent simulant detection in conjunction with superoxide “turn-on” probing

Herein, we present fluorescein as a reversible fluorescent sensor for nerve agent simulants diethylchlorophosphate (DCP), diethyl methylphosphonate (DEMP), and diethyl cyanophosphonate (DECP). The superoxide allows for an "off-on" mechanism to regenerate fluorescein. The order of decrease in fluorescence intensity for nerve agent simulants is DCP > DEMP ≫ DECP.

Conjugated Polyfluorene-based Reversible Fluorescent Sensor for Cu(II) and Cyanide Ions in Aqueous Medium

Abstract A blue emissive polyfluorene bearing sulfate functionality in the side chain (PFS), as a sensory polymer to selectively report the presence of Cu2+ (detection limit down to 2.5 µM) based on the fluorescence “turn-off.” Surprisingly, the quenched luminescence of PFS by Cu2+ could be turned on after the addition of CN− (detection limit down to 6 µM), making PFS a sensitive, selective, and reversible cyanide probe.

Benchtop Monitoring of Reaction Progress via Visual Recognition with a Handheld UV Lamp: In Situ Monitoring of Boronic Acids in the Suzuki−Miyaura Reaction

[reaction: see text] Although boronic acids are widely used in metal-catalyzed reactions, it is difficult to assay their consumption. As such, we developed a reversible fluorescent sensor that is activated upon binding a boronic acid. The sensor can be used to monitor consumption of a boronic acid in Suzuki-Miyaura reactions. Importantly, only a standard handheld long-wave UV lamp (365 nm) is required and fluorescence is easily detectable with the naked eye without disturbing the reaction mixture.

Selective determination of bisphenol A (BPA) in water by a reversible fluorescence sensor using pyrene/dimethyl β-cyclodextrin complex

A bifurcated optical fiber chemical sensor for continuous monitoring of bisphenol A (BPA) has been proposed based on the fluorescence quenching ( λ ex/ λ em = 286/390 nm) of pyrene/dimethyl β-cyclodextrin (HDM-β-CD) supramolecular complex immobilized in a plasticized poly(vinyl chloride) (PVC) membrane, in which pyrene served as a sensitive fluorescence indicator probe. The decrease of the fluorescence intensity of pyrene/HDM-β-CD complex upon the addition of BPA was attributed to the displacement of pyrene by BPA, which has been utilized as the basis of the fabrication of a BPA-sensitive fluorescence sensor. The response mechanism of the sensor was discussed in detail. The sensor exhibited a dynamic detection range from 7.90 × 10 −8 to 1.66 × 10 −5 mol L −1 with a detection limit of 7.00 × 10 −8 mol L −1, and showed excellent reproducibility, reversibility, selectivity, and lifetime. The proposed sensor was successfully used for the determination of BPA in water samples and landfill leachate.

A reversible fluorescence sensor based on insoluble β-cyclodextrin polymer for direct determination of bisphenol A (BPA)

Based on the reversible recognizing reaction between insoluble β-cyclodextrin polymer (β-CDP) and bisphenol A (BPA), a bifurcated optical fiber chemical sensor has been proposed for continuous monitoring of BPA. When immobilized in a plasticized poly(vinyl chloride) membrane of 5 μm thickness, β-CDP extracts BPA from aqueous solutions into the bulk membrane phase and reacts with the analyte to form an inclusion complex with high fluorescence efficiency. Formation of the complex gives a significant enhancement of the intrinsic fluorescence ( λ ex/ λ em = 286 nm/312 nm) of BPA which is suitable for signaling the occurrence of the host–guest recognizing interaction. The fluorescence sensor exhibits a dynamic detection range from 6.0 × 10 −6 mol/L to 1.0 × 10 −3 mol/Lwith a detection limit of 1.0 × 10 −6 mol/L. The high selectivity of the sensor toward BPA depends on the synergistic shielding effect by β-CD units and an optimal space-matching between the host and the guest. The proposed sensor was successfully used for the determination of BPA in water samples.