Fluorescence Signaling Behavior Research Articles

Fluorometric hypochlorite sensing by 2-acetylnaphthol phosphinothioate and its application to hypochlorite analysis in industrial effluent

In this study, we report the hypochlorite-selective signaling behavior of 2-acetyl-6-naphthol phosphinothioate (Hyp-1). Probe Hyp-1 demonstrated marked turn-on fluorescence signaling behavior exclusively toward hypochlorite in a phosphate-buffered saline solution with the pH value of 7.4. The signaling was triggered by the hypochlorite-induced hydrolysis of the phosphinothioate with the concomitant chlorination of the generated 2-acetyl-6-naphthol fluorophore. Interference from other metal ions and anions was not observed during the signaling process. A clear signal was produced within 1 min with a detection limit of 2.70 × 10–8 M (1.39 ppb). To demonstrate its practical utility, the probe was successfully used to detect the presence of hypochlorite in simulated pulp/paper mill and textile industrial effluents.

Colorimetric analysis of palladium using thiocarbamate hydrolysis and its application for detecting residual palladium in drugs

In this research, we report a practical colorimetric method for the convenient analysis of residual palladium ions in drugs and drug intermediates. In a phosphate-buffered (pH 7.0) 50% aqueous DMSO solution, chlororhodol-based probe PP-1 demonstrated a prominent colorimetric (APP-1+Pd(II)/APP-1 at 531 nm is over 780) and turn-on type fluorescence signaling behavior (IPP-1+Pd(II)/IPP-1 at 561 nm is over 2000) toward palladium. The signaling was realized through the palladium-assisted hydrolysis of the thiocarbamate protecting moiety of the probe. Palladium-selective signaling was feasible in the presence of possibly interfering chemical species, and it was concluded within 7 min. The selective signaling was observed for palladium species with different oxidation states (Pd2+, Pd4+, and Pd0). The detection limit of the probe for palladium analysis was sufficiently sensitive to analyze the residual palladium in drugs and related products (LODPP-1 = 1.0 × 10–8 M, LODPP-2 = 4.3 × 10–8 M). In particular, palladium analysis could be performed in the presence of ibuprofen and 2-cyano-4′-methylbiphenyl, as the drug and drug intermediate, respectively.

Dual signaling of thallium(III) ions via oxidative cleavage of a sulfonhydrazide linkage

The thallium is widely used in various research and industrial applications but is very toxic. In this work, we developed a novel reaction-based dual signaling probe for the selective and sensitive determination of Tl3+ via the oxidative cleavage of a rhodamine–dansylhydrazide conjugate. The designed probe showed pronounced colorimetric and fluorescence signaling behavior toward Tl3+ with a detection limit of 1.3 × 10–7 M (0.027 ppm), as well as selectivity over other common metal ions, anions, and oxidants. The Tl3+ signaling process required less than 2 min and was not influenced by the solution pH within the range of 4.0–5.5; however, the signal diminished significantly above pH 6.0. To demonstrate the practical applicability of the designed probe, a simple and convenient colorimetric assay for the determination of Tl3+ in commercial reagents was established using an office scanner as a readily available signal capturing device.

Novel Hg2+-Selective Signaling Probe Based on Resorufin Thionocarbonate and its \u03bcPAD Application

In this study, a novel resorufin thionocarbonate-based Hg2+-selective signaling probe (RT) for microfluidic paper-based analytical device (μPAD) applications is reported. The designed probe, RT, was readily synthesized by the one-step reaction of resorufin with phenyl thionochloroformate. The RT probe displayed a prominent color change from yellow to pink and a marked turn-on fluorescence signaling behavior exclusively toward the Hg2+ ion. The signaling of RT was due to Hg2+-induced hydrolysis of the phenyl thionocarbonate moiety to form the parent resorufin dye, which restored its spectroscopic properties. In addition, RT exhibited the Hg2+-selective signaling behavior without interference by coexisting environmentally relevant metal ions. The detection limit for Hg2+ in simulated wastewater samples was estimated to be 5.8 × 10−8 M. In particular, an RT-equipped μPAD prepared using a wax printing technique enabled simple and convenient determination of Hg2+ ions in simulated wastewater samples, with a detection limit of 5.9 × 10−6 M.

Fluorometric determination of Au3+ via hydrolysis of thiocarbonate with bromide as a masking agent

Gold ions are very important in chemistry and materials science owing to their various uses in chemical reactions as well as industrial and biological applications. In this study, we developed a novel reaction-based probe (GP), which is a thiocarbonate derivative of the 2-(2-hydroxyphenyl)benzothiazole dye, for the selective and sensitive determination of Au3+. The probe GP showed turn-on fluorescence signaling behavior toward Au3+ ions triggered by the metal-induced hydrolysis of the thiocarbonate group. Interference from other thiophilic ions, Ag+ and Hg2+, was effectively eliminated by using bromide ions as a masking agent. Prominent off–on type fluorescent sensing of Au3+ over other coexisting metal ions was possible with a detection limit of 4.8 × 10−8 M (9.5 ppb). Fluorescence sensing of Au3+ by GP was fast and applicable over a wide pH range between 4.0 and 10.5. Application of the probe to the analysis of Au3+ in synthetic wastewater was conducted using an easily accessible smartphone.

A simple hypochlorous acid signaling probe based on resorufin carbonodithioate and its biological application.

A novel hypochlorous-acid-selective signaling probe based on the carbonodithioate derivative of resorufin (RT-1) was developed. Probe RT-1 showed prominent colorimetric and turn-on type fluorescence signaling behavior exclusively toward hypochlorous acid, induced by oxidative hydrolysis, to regenerate resorufin dye. Hypochlorous acid signaling was not affected by the presence of common metal ions and anions as background, except for the redox active bromide and iodide anions. The detection limit of RT-1 for hypochlorous acid was found to be 2.18 × 10-9 M (0.11 ppb), and the signaling was completed within 3 min. It was also confirmed that hypochlorous acid signaling by the carbonodithioate-based probe RT-1 was superior to that of the closely related carbonothioate derivative RT-2. This was rationalized by density functional theory calculations, which demonstrated that the C[double bond, length as m-dash]S sulfur atom of the former is more negatively charged than that of the latter. Finally, as a biological application of the probe, visualization of hypochlorous acid in RAW 264.7 murine macrophages and HeLa cells was successfully conducted to detect the cellular response to hypochlorous acid.

Fluorometric analysis of borohydrides based on reductive aldehyde-to-alcohol conversion of arylaldehydes

Fluorometric analysis of borohydride (BH4–) species by the reduction of arylaldehydes to the corresponding arylmethanols was investigated. 9-Anthracenecarboxaldehyde (9-AA) exhibited pronounced ratiometric fluorescence signaling behavior toward borohydride in alkaline aqueous media. The borohydride-selective signaling of 9-AA was unaffected by the presence of commonly encountered metal ions and anions. 1-Pyrenecarboxaldehyde (1-PA) also showed comparable borohydride signaling behavior. The detection limit was found to be 7.4 μM (0.11 ppm) for 9-AA and 15.7 μM (0.23 ppm) for 1-PA. The utility of the probe with μPAD as a convenient tool for the determination of borohydrides was demonstrated.

Polyurethane network using 1-naphthylamine embedded epoxy-based polymer: ferric ion selective fluorescent probe

Polyurethane network 1 was prepared through curing of epoxy-based polymer bearing 1-naphthylamine units with tolylene-2,4-diisocyanate as curing agent. With ferric ions, the network was found to exhibit selective ON–OFF-type fluorescence signaling behavior even in the presence of other representative metal ions such as Na+, K+, Ag+, Cu2+, Zn2+, Co2+, Ni2+, Cd2+, Hg2+, Mg2+, Sr2+, Pb2+ and Ca2+ ions.

Cu2+-selective fluorescent probe based on the hydrolysis of semicarbazide derivative of 2-(2-aminophenyl)benzothiazole

A new Cu2+-selective reaction-based fluorescent probe 1 based on the semicarbazide-bearing derivative of 2-(2-aminophenyl)benzothiazole has been developed. Designed probe 1 exhibited turn-on-type fluorescence signaling behavior that was more prominent toward Cu2+ ions than to other environmentally relevant metal ions. The signaling of probe 1 was due to the Cu2+-induced hydrolysis of semicarbazide moiety to form its strongly fluorescent parent dye. Cu2+ signaling of probe 1 was not influenced by the presence of commonly encountered metal ions, and the detection limit was 1.71 × 10−8 M (1.1 ppb). As a practical application, the determination of Cu2+ in simulated semiconductor wastewater was conducted using a smartphone as a portable signal detection tool. For the color test analysis, enhanced reproducibility of Cu2+-sensing was realized using the grayscale image rather than the red, green, or blue channel image.

Fluorescence sensing of Ag+ ions by desulfurization of an acetylthiourea derivative of 2-(2-hydroxyphenyl)benzothiazole

A novel Ag+-selective reaction-based probe based on an acetylthiourea derivative of 2-(2-hydroxyphenyl)benzothiazole dye was investigated. The designed probe showed pronounced off-on type fluorescence signaling behavior towards Ag+ ions via Ag+-induced desulfurization of acetylthiourea to acetylurea. The signaling was superior to the analogous thioamide-to-amide conversion in terms of both speed and signaling contrast. Interference from thiophilic Hg2+ ions was effectively suppressed using the chelating agent EDTA as a masking agent. The practical application of the system to the detection of Ag+ in simulated wastewater with a detection limit of 0.76 μM using a smartphone as an easy-to-use data capturing and processing device was successfully demonstrated.

Fluorescence signaling of thiophenol by hydrolysis of dinitrobenzenesulfonamide of 2-(2-aminophenyl)benzothiazole

Thiophenols are important chemical species in industrial and chemical sciences but are very toxic and therefore need selective and sensitive detection methods. In this work, a new reaction-based fluorescence signaling probe using a fluorescent dye, 2-(2-aminophenyl)benzothiazole, for thiophenol has been designed and its fluorescence signaling behavior has been investigated. The 2,4-dinitrobenzenesulfonamide derivative of 2-(2-aminophenyl)benzothiazole was found to exhibit a pronounced off–on-type of fluorescence signaling behavior towards thiophenol over other commonly encountered metal ions, anions, as well as aliphatic thiols. Signaling of thiophenol is based on the thiol-induced cleavage of sulfonamide linkage to generate a strongly fluorescent dye. The designed probe was applied to the monitoring of thiophenols in environmental samples of simulated wastewater with a detection limit of 4.72 × 10−8 M (0.005 ppm). In addition, convenient signaling of thiophenol levels in environmentally relevant aqueous solutions was conducted by using an easily accessible smartphone.

Selective fluorescence signaling of hypochlorite in tap water by oxidative hydrolysis of sulfonhydrazone

A new hypochlorite-selective fluorescence signaling probe based on the sulfonhydrazone of 2-acetyl-6-methoxynaphthalene was investigated. The probe was easily prepared by the simple one-step reaction of 2-acetyl-6-methoxynaphthalene with p-toluenesulfonylhydrazide. The probe exhibited off/on-type fluorescence signaling behavior toward hypochlorite in aqueous solution via hypochlorite-triggered oxidative hydrolysis of the sulfonhydrazone to yield strongly fluorescent 2-acetyl-6-methoxynaphthalene. Selective hypochlorite signaling over other common oxidants with a large fluorescence enhancement (76-fold) was possible, with a detection limit of 2.0×10−8M. Hypochlorite signaling was not affected by the presence of other common metal ions or representative anions. As a practical application, the methoxyacetylnaphthalene sulfonhydrazone probe was used to determine hypochlorite levels in a tap water sample using a standard smartphone as the detection tool.

Selective Hg2+ signaling via dithiane to aldehyde conversion of an ESIPT fluorophore

We herein report the development of a simple structured reaction-based probe for the fluorescence signaling of Hg2+ ions using a dithiane derivative of an excited-state intramolecular proton transfer (ESIPT) dye. The designed probe exhibited prominent fluorescence signaling behavior towards Hg2+ ions by the deprotection of its dithiane function to an aldehyde in an aqueous acetonitrile solution. The interfering response of Cu2+ ions was efficiently removed using citrate as both a masking agent and a buffer. Thus, the use of a citrate buffer allowed exclusive Hg2+-selective signaling to be obtained in the presence of common environmentally relevant transition metal ions. Signaling of the Hg2+ ions was complete within 15 min after sample preparation, and a detection limit of 2.0 × 10−7 M was estimated. As a practical application of the designed probe, the detection of Hg2+ ions in simulated wastewater was tested using a smartphone as a portable signal-capturing device.

Cu2+-selective ratiometric fluorescence signaling probe based on the hydrolysis of dansylhydrazine

A simple Cu2+-selective ratiometric fluorescence signaling probe based on the hydrolysis of dansylhydrazine was developed. Dansylhydrazine 1 showed prominent ratiometric fluorescence signaling behavior toward Cu2+ ions in a 50% aqueous (pH 7.4) acetonitrile solution. The ratiometric signaling behavior was due to the Cu2+-assisted hydrolysis of the yellow-colored fluorescent dansylhydrazine to strongly blue-fluorescent dansyl acid. The Cu2+-selective signaling of probe 1 was not affected by the presence of biologically important metal ions. The ratiometric signaling of Cu2+ by 1 was possible with a detection limit of 6.0×10−8M (3.8ppb). In addition, the signaling of Cu2+ in biological samples using synthetic urine was also tested.

Discriminative sensing of sulfide and azide ions in solution by a nitrobenzoxadiazole-dansyl dyad by simply tuning the water content

A new chromogenic and fluorogenic probe for the discriminative signaling of sulfide and azide ions using a nitrobenzoxadiazole (NBD)-dansyl dyad 3 has been investigated. Probe 3 showed prominent colorimetric and fluorescence signaling behavior toward sulfide and azide ions in aqueous tetrahydrofuran (THF). Anion selectivity was controlled by the water content in THF. In a water rich system (H2O/THF=99:1, v/v), probe 3 reacted mainly with sulfide ions, owing to the sulfide-selective cleavage of the NBD-OSO2Ar bond, to yield the pink-colored NBD-SH and fluorescent dansyl acid. However, in water deficient conditions (H2O/THF=10:90, v/v), probe 3 exhibited both azide- and sulfide-selective reactions, due to the cleavage of the NBD-OSO2Ar bond, to yield either NBD-N3 (for azide ions) or NBD-SH (for sulfide ions), and dansyl acid. Azide ions can be discriminatively signaled by selective excitation at the NBD-N3 without interference from the sulfide signaling products. This selective signaling behavior is not affected by other anions that might be present in the environmental samples. To test the practical use of this probe, we created a test strip that could be used to detect sulfide and azide ions.

Ratiometric Signaling of Hypochlorite by the Oxidative Cleavage of Sulfonhydrazide-Based Rhodamine-Dansyl Dyad.

A reaction-based probe 1 for hypochlorite signaling was designed by the conjugation of two fluorophores, rhodamine and dansyl moieties, by the reaction of rhodamine B base with dansylhydrazine. Probe 1 exhibited pronounced hypochlorite-selective chromogenic and fluorescent signaling behavior over other oxidants used in practical applications, such as hydrogen peroxide, peracetic acid, and ammonium persulfate, as well as commonly encountered metal ions and anions. Signaling was attributed to the hypochlorite-induced oxidative cleavage of the sulfonhydrazide linkage of the probe. In particular, favorable ratiometric fluorescence signaling was possible by utilizing the emissions of the two fluorophores. A detection limit of 1.13 × 10(-6) M (0.058 ppm) was estimated for the determination of hypochlorite. A paper-based test strip was prepared and was used as a semiquantitative indicator for the presence of hypochlorite in aqueous solutions. The probe was also successfully applied for the determination of hypochlorite in practical tap water samples.

Structural relevance of N2O2-donor naphthodiaza-crown macrocyclic ligands to selective fluorescence signaling behavior towards aliphatic tertiary amines

Abstract A series of N2O2-donor naphthodiaza-crown macrocyclic ligands, L1–L5, were synthesized and characterized by IR, 1H and 13C NMR spectroscopy, mass spectrometry as well as microanalysis. Preliminary observations employing UV–vis spectrophotometry of L3 in ethanol revealed that triethylamine (TEA) has a significant blue-shift effect on the entire of the spectra. Then, the detection of aliphatic and aromatic amines by L3 were followed by monitoring of fluorescence quenching of the resulting adducts in terms of their binding with L1-L5. Both steady-state and time-resolved spectroscopic measurements in the polar ethanol (EtOH) solvent show that the fluorescence quenching phenomenon of L1–L5 in presence of TEA is primarily due to the involvement of dynamic process. The fluorescence quenching of L1–L5 was described according to the hydrogen bonding of NH groups on the aza-crowns with TEA. A mechanism of proton transfer in excited state in terms of hydrogen bonding of the macrocyclic ligands with amines was also proposed for selective fluorescence quenching of tertiary aliphatic amines by L1–L5.

Signaling of water content in organic solvents by solvatochromism of a hydroxynaphthalimide-based merocyanine dye

Determining the water content in organic solvents has attracted much research interest in view of its importance in various chemical processes. We investigated the signaling behavior of a benzothiazolium appended 4-hydroxynaphthalimide derivative 1 for the water content in water-miscible organic solvents such as tetrahydrofuran, acetone, dimethyl sulfoxide, acetonitrile, ethanol, and methanol using UV–vis and fluorescence spectroscopy. Probe 1 showed pronounced negative solvatochromism in common organic solvents and revealed excellent correlation between the 1/λmax value and Reichardt's ET(30) parameter. The response to the changes in water content in the surveyed organic solvents could be analyzed using a ratiometric approach. The dependence of the absorption maximum (λmax) on the changes in water content was also useful as a calibration plot. The fluorescence signaling behavior was less pronounced than that of the UV–vis signaling, but was still usable.

Signaling of chloramine: a fluorescent probe for trichloroisocyanuric acid based on deoximation of a coumarin oxime

A new chloramine signaling probe, based on a coumarin oxime, was developed. The coumarin oxime 1 exhibited efficient off–on type fluorescent signaling behavior toward trichloroisocyanuric acid (TCCA) in an aqueous acetonitrile solution. The signaling is due to the TCCA-assisted transformation of the oxime function to its carbonyl analogue. The presence of common metal ions and anions did not interfere with the TCCA signaling of this probe. Probe 1 was found to be useful for the sensitive determination of the concentration of the practical oxidant TCCA in an aqueous environment, with a detection limit of 7.58×10−7M.

A highly selective PET-based chemosensor for instant detecting of Zn2+

A simple Zn2+-selective chemosensor system based on acylhydrazone was designed and synthesized, which could detect Zn2+ ions in aqueous solution with high selectivity and sensitivity over a wide pH range by the mechanism of photo-induced electron transfer (PET). The obvious color changes and pronounced OFF-ON-type fluorescent signaling behavior can be seen by the naked eye. The detection limit of L2 for Zn2+ ion was as low as 0.13 μM. In addition, L2–Zn2+ complex can be used as an ON-OFF chemosensor candidate for Cu2+, as the Zn2+-induced emission can be quenched upon addition of Cu2+. Moreover, test strips for Zn2+ based on L2 were also fabricated, which could be used as a convenient and efficient test kit for instantly detecting Zn2+ in aqueous solution.