Novel fluorescent sensor for Ag and Hg based on the BINOL-pyrene derivative via click reaction

A novel BINOL-pyrene derivative sensor 1 for Ag⁺ and Hg²⁺ incorporating the triazole moieties and pyrenes was synthesized via click reaction. Binding of Ag⁺ ion induces the formation of 1:1 Ag⁺-1 chelating complex, and occurs in a ratiometric manner through an enhanced monomer and declining excimer emission, which make it possible to ratiometrically detect Ag⁺. The competitive experiment shows 1 can be used as an Ag⁺ specific fluorescence sensor over a wide range of competing cations. In the meanwhile, the sensor 1 was found to be selectively quenched by only Hg²⁺ at both monomer and excimer emission. Furthermore, we obtained evidences for different fluorescence signaling behaviors with Ag⁺ and Hg²⁺ by ¹H NMR titration experiments.     

A highly selective fluorescent sensor for Cu based on 2-(2′-hydroxyphenyl)benzoxazole in a poly(vinyl chloride) matrix

This paper describes a copper selective optical chemical sensor based on static quenching of the fluorescence of 2-(2′-hydroxyphenyl)benzoxazole entrapped in a poly(vinyl chloride) (PVC) membrane. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensors exhibit stable response over the concentration range from 4.0 × 10⁻⁸ M to 5.0 × 10⁻⁵ M Cu²⁺ at pH 4.0-6.5, and a high selectivity. The response time for Cu²⁺ with concentration ≤5 × 10⁻⁶ M is less than 7 min. The optode can be regenerated using 0.1 M HCl and acetate buffer solution. The sensor has been used for direct measurement of copper content in river water samples with a relative error less than 4% with reference to that obtained by atomic absorption spectrometry.     

A fluorescent chemical sensor for Fe based on blocking of intramolecular proton transfer of a quinazolinone derivative

In this paper, 2-(2′-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe³⁺ sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe³⁺ was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe³⁺ in the concentration range of 7.1 × 10⁻⁷ M to 1.4 × 10⁻⁴ M with a limit of detection of 8.0 × 10⁻⁸ M, and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe³⁺ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results.     

A fluorescent sensor for Hg and Ag functions as a molecular switch based on click-generated triazole moiety

The novel (S)-BINOL-based sensor 1 incorporating triazole moieties could be obtained by click reaction. The results show that 1 can exhibit excellent fluorescence response behaviors toward Hg²⁺ (selective switching-off) and Ag⁺ (selective switching-on) without interference from other metal ions, which functions as a molecular switch. This work can expand the application of click reaction in design and synthesis of the novel fluorescence sensor molecules.     

Cu(II) complex of an abiotic receptor as highly selective fluorescent sensor for acetate

A copper complex having quinoline moiety as fluorophore has been synthesized. The anion recognition behavior of the receptor and its copper complex has been studied in acetonitrile and in acetonitrile: H₂O (95:5 v/v). The copper complex shows high selectivity toward acetate over other anions studied such as F⁻, Cl⁻, Br⁻, I⁻, OAc⁻, dl-malate, l-mandelate, benzoate, isophthalate, , and .     

A fast,highly selective and sensitive dansyl-based fluorescent sensor for copper (II) ions and its imaging application in living cells

Since the copper ions (Cu²⁺) play a fatal role in many foundational physiological processes, it is important to develop a simple, highly sensitive and selective sensor for Cu²⁺ detection in living systems. Herein, an intramolecular charge transfer (ICT) and dansyl-based fluorescent chemosensor 1 was designed, synthesized and characterized for the sensitive and selective quantification of Cu²⁺. It exhibited remarkable fluorescence quenching upon addition of Cu²⁺ over other selected metal ions, attributed to the complex formation between 1 and Cu²⁺ with the association constant 6.7 × 10⁵ M^?1. The sensor 1 showed a fast and linear response towards Cu²⁺ in the concentration range from 0 to 12.5 × 10^?6 mol L^?1 with the detection limit of 2.5 × 10^?7 mol L^?1. This detection could be carried out in a wide pH range of 5.0–14. Furthermore, sensor 1 can be used for detecting Cu²⁺ in living cells.     

1-Pyrenecarboxaldehyde thiosemicarbazone:A novel fluorescent molecular sensor towards mercury(Ⅱ) ion

<正>A novel and simple fluorescent molecular sensor,1-pyrenecarboxaldehyde thiosemicarbazone(Hpytsc),was synthesized.Its higher sensitivity and selectivity to mercury(Ⅱ) ion were studied through absorption and emission channels.The UV-vis spectra show that the increasing mercury(Ⅱ) ion concentrations result in the decreasing absorption intensity.The fluorescence monomer emission of Hpytsc is enhanced upon binding mercury(Ⅱ) ion,which should be due to the 1:1 complex formation between Hpytsc and metal ion.     

A fluorescent chemosensor for cobalt ions based on a multi-substituted phenol-ruthenium(II) tris(bipyridine) complex

An amide-linked 2,6-bis{[(2-hydroxy-5-tert-butylbenzyl)(pyridyl-2-methyl)-amino]-methyl}-4-methylphenol-ruthenium(II) tris(bipyridine) 2PF₆⁻ complex, 1, was first used to recognize Co(II) in EtOH/H₂O (1:1, v/v) solution, with the ruthenium(II) tris(bipyridine) moiety selected as a fluorophore and the multi-substituted phenol unit chosen as a receptor. The fluorescence quenching of 1 was attributed to the formation of an inclusion complex between multi-substituted phenol unit and Co(II) by 1:1 complex ratio (K = 2.5 × 10⁵), which has been utilized as the basis of the fabrication of the Co(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Co(II)-sensitive chemosensor were investigated. The sensor can be applied to the quantification of Co(II) with a linear range covering from 1.0 × 10⁻⁷ to 5.0 × 10⁻⁵ M and a detection limit of 5 × 10⁻⁸ M. The experiment results show that the response behavior of 1 to Co(II) is pH-independent in medium condition (pH 4.5–9.5) and show excellent selectivity for Co(II) over transition metal cations except Cu(II). The chemosensor has been used for determination of Co(II) in water samples.     

5,10,15-Tris(pentafluorophenyl)corrole as highly selective neutral carrier for a silver ion-sensitive electrode

A new highly selective silver(I) electrode was prepared with a PVC membrane using 5,10,15-tris(pentafluorophenyl)corrole as an electroactive material, 2-nitrophenyl octyl ether (o-NPOE) as a plasticizer and sodium tetraphenylborate (NaTPB) as an additive in the percentage ratio of 3:3:62:32 (corrole:NaTPB:o-NPOE:PVC, w:w). The electrode exhibited linear response with a near Nernstian slope of 54.8 mV/decade within the concentration range of 5.1 × 10⁻⁶ to 1.0 × 10⁻¹ M silver ions, with a working pH range from 4.0 to 8.0, and a fast response time of <30 s. Selectivity coefficients for Ag(I) relative to a number of interfering ions were investigated. The electrode is highly selective for Ag(I) ions over a large number of mono-, bi-, and tri-valent cations. Common interferents like Hg²⁺ and Cd²⁺ show very low interfering effect on the silver assay, which is valuable property of the proposed electrode. Several electroactive materials and solvent mediators have been compared and the experimental conditions were optimized. The sensor was applied to the determination of silver in real ore samples with satisfied results.     

A functionalized gold nanoparticles and Rhodamine 6G based fluorescent sensor for high sensitive and selective detection of mercury(II) in environmental water samples

A gold-nanoparticles (Au NPs)-Rhodamine 6G (Rh6G) based fluorescent sensor for detecting Hg (II) in aqueous solution has been developed. Water-soluble and monodisperse gold nanoparticles (Au NPs) has been prepared facilely and further modified with thioglycolic acid (TGA). Free Rh6G dye was strongly fluorescent in bulk solution. The sensor system composing of Rh6G and Au NPs fluoresce weakly as result of fluorescence resonance energy transfer (FRET) and collision. The fluorescence of Rh6G and Au NPs based sensor was gradually recovered due to Rh6G units departed from the surface of functionalized Au NPs in the presence of Hg(II). Based on the modulation of fluorescence quenching efficiency of Rh6G-Au NPs by Hg(II) at pH 9.0 of teraborate buffer solution, a simple, rapid, reliable and specific turn-on fluorescent assay for Hg(II) was proposed. Under the optimum conditions, the fluorescence intensity of sensor is proportional to the concentration of Hg(II). The calibration graphs are linear over the range of 5.0 × 10⁻¹⁰ to 3.55 × 10⁻⁸ mol L⁻¹, and the corresponding limit of detection (LOD) is low as 6.0 × 10⁻¹¹ mol L⁻¹. The relative standard deviation of 10 replicate measurements is 1.5% for 2.0 × 10⁻⁹ mol L⁻¹ Hg(II). In comparison with conventional fluorimetric methods for detection of mercury ion, the present nanosensor endowed with higher sensitivity and selectivity for Hg(II) in aqueous solution. Mercury(II) of real environmental water samples was determined by our proposed method with satisfactory results that were obtained by atomic absorption spectroscopy (AAS).     

A ratiometric chemosensor for fluorescent determination of Hg based on a new porphyrin-quinoline dyad

Quinolin-8-ol p-[10′,15′,20′-triphenyl-5′-porphyrinyl]benzoate (1) was synthesized for the first time and developed as a ratiometric fluorescent chemosensor for recognition of Hg²⁺ ions in aqueous ethanol with high selectivity. The 1–Hg²⁺ complexation quenches the fluorescence of porphyrin at 646 nm and induces a new fluorescent enhancement at 603 nm. The fluorescent response of 1 towards Hg²⁺ seems to be caused by the binding of Hg²⁺ ion with the quinoline moiety, which was confirmed by the absorption spectra and ¹H NMR spectrum. The fluorescence response fits a Hill coefficient of 1 (1.0308), indicating the formation of a 1:1 stoichiometry for the 1–Hg²⁺ complex. The analytical performance characteristics of the chemosensor were investigated. The sensor shows a linear response toward Hg²⁺ in the concentration range of 3 × 10⁻⁷ to 2 × 10⁻⁵ M with a limit of detection of 2.2 × 10⁻⁸ M. Chemosensor 1 shows excellent selectivity to Hg²⁺ over transition metal cations except Cu²⁺, which quenches the fluorescence of 1 to some extent when it exists at equal molar concentration. Moreover, the chemosensor are pH-independent in 5.0–9.0 and show excellent selectivity for Hg²⁺ over transition metal cations.     

Developing a genetically encoded green fluorescent protein mutant for sensitive light-up fluorescent sensing and cellular imaging of Hg(II)

Hg(II) is well-known for quenching fluorescence in a distance dependent manner. Nevertheless, when we exposed the fluorophore of a green fluorescent protein (GFP) toward Hg(II), through H148C mutation, the GFP fluorescence could be “lighted up” by Hg(II) down to sub-nM level. The detection linear range is 0.5–3.0 nM for protein solutions at 8.0 nM. The GFPH148C protein displayed a promising selectivity toward Hg(II) and also the cellular imaging capacity. Spectra measurements suggested that the ground-state redistribution of protein contributed to the fluorescence enhancement, which was found not limited to Hg(II), and thus presented an opening for building a pool of GFP-based chemosensors toward other heavy metal ions.     

An optical chemical sensor for mercury ion based on 2-mercaptopyrimidine in PVC membrane

An optical chemical sensor based on 2-mercaptopyrimidine (2-MP) in plasticized poly(vinyl chloride) (PVC) membrane incorporating (N,N-diethyl-5-(octadecanoylimino)-5H benzo[a]phenoxazine-9-amine (ETH 5294) and sodium tetraphenyl borate (NaTPB) for batch and flow-through determination of mercury ion is described. The response of the sensor is based on selective complexation of Hg²⁺ with 2-MP in the membrane phase, resulting in an ion exchange process between H⁺ in the membrane and Hg²⁺ in the sample solution. The influences of several experimental parameters, such as membrane composition, pH, and type and concentration of the regenerating reagent, were investigated. The sensor has a response range of 2.0 × 10⁻⁹ to 2.0 × 10⁻⁵ mol L⁻¹ Hg²⁺ with a detection limit of 4.0 × 10⁻¹⁰ mol L⁻¹ and a response time of ≤45 s at optimum pH of 6.5 with high measurement repeatability and sensor-to-sensor reproducibility. It shows high selectivity for Hg²⁺ over several transition metal ions, including Ag⁺, Cd²⁺, Co²⁺, Cr³⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, and common alkali and alkaline earth ions such as Na⁺, K⁺, Mg²⁺, Ca²⁺, and Pb²⁺. The sensor membrane can be easily regenerated with dilute acid solutions. The sensor has been used for the determination of mercury ion concentration in water samples.     

A selective, sensitive probe for mercury(II) ions based on oxazine-thione

A selective, sensitive probe for Hg(II) ions, 7-(diethylamino)-3-methyl-2H-benzo[b][1,4] oxazine-2-thione (1), is developed. Compound 1 behaves as a ratiometric probe, exhibiting a large blue shift of 100 nm in its absorption spectra upon exposure to Hg(II) ions. The dramatic color change of the solution made ‘naked-eye’ detection of Hg(II) ions possible. Emission spectra of 1 displayed a selective enhancement in intensity in the presence of Hg(II) ions. ESI⁺-MS analysis indicated that Hg²⁺-induced desulfurization caused the large absorption response.     

A fluorescent ammonia sensor based on a porphyrin cobalt(II)-dansyl complex

Detecting and measuring the concentration of ammonia is of interest in many scientific and technological areas. A porphyrin based cobalt(II) complex with a dansyl fluorophore has been synthesized and investigated as a ‘turn-on’ fluorescent ammonia sensor. Over sixfold increase in fluorescence emission occurs upon the treatment of NH₃ to [Co(TPP)(Ds-pip)] sensor solution, resulting from NH₃-induced displacement of the axially coordinated fluorophore.     

A new bis(pyrenyl)azadiene-based probe for the colorimetric and fluorescent sensing of Cu(II) and Hg(II)

A novel colorimetric and fluorescent chemosensor 2, made up of two pyrene units connected by a 2-aza-1,3-butadiene ionophore, was designed and prepared for the selective detection of Cu²⁺ and Hg²⁺ in the presence of other metal cations. This molecular sensor exhibits substantial colour changes and fluorescence enhancement upon complexation with these metal cations in acetonitrile solutions, with detection limits in the order of 10⁻⁶ M. Job's plots revealed a 1:1 stoichiometry rationalized by theoretical DFT calculations.     

A highly selective pyrene based fluorescent sensor toward Hg detection

A new pyrene-containing fluorescent sensor has been synthesized from 2,3,3-trimethylindolenine. Spectroscopic and photophysical properties of sensor are presented. The large change in fluorescence intensity (I/I₀ = 0.13) at 381 nm and affinity to Hg²⁺ over other cations such as K⁺, Na⁺, Ca²⁺, Mg²⁺, Pb²⁺, and Cu²⁺ make this compound a useful chemosensor for Hg²⁺ detection in hydrophilic media. The sensor (6.0 × 10⁻⁶ M) displays significant fluorescence quenching upon addition of Hg²⁺ in pH 7.4 HEPES buffer without excimer formation. Job’s plot analysis shows the binding stoichiometry to be 2:1 (host/guest).     

Novel colorimetric sensor for mercury (Ⅱ) based on layer-by-layer assembly of unmodified silver triangular nanoplates

A simple layer-by-layer deposition technique was used to fabricate the multilayer thin films of unmodified silver triangular nanoplates(AgTNPs).The multilayer of AgTNPs thin films were fabricated by alternate deposition of each anionic sodium citrate stabilized AgTNPs and cationic poly(diallyldimethylammonium chloride).All prepared AgTNPs multilayer thin films were exhibited a strong plasmon band at the wavelength of 667 nm,which confirmed the formation of AgTNPs onto the substrate.The characteristics of the multilayer thin films were investigated using contact angle measurement,UV-visible spectroscopy,X-ray diffraction analysis(XRD),atomic force microscope(AFM)and field emission scanning electron microscope(FESEM).As these films are to be used as a mercury(II)colorimetric sensor,the changes in optical properties of the films were evaluated for various mercury(Ⅱ)concentrations.AgTNPs assembled into thin films showed a strong color shift from blue to mauve and colorless when exposed to mercury(Ⅱ).The constructed multilayer thin films exhibited excellent color changes of mercury(II) with a linear range between 0.5 and 20 ppm.The limit of detection(LOD) and limit of quantitation(LOQ) were 0.45 ± 0.002 and 1.52 ± 0.002 ppm,respectively.The recovery values of AgTNPs multilayer thin films are satisfactory in the range of 100.1%-106.4%when applied to determining mercury(Ⅱ) in water samples.     

p-Dimethylaminobenzaldehyde thiosemicarbazone: a simple novel selective and sensitive fluorescent sensor for mercury(II) in aqueous solution

A novel and simple fluorophore, p-dimethylaminobenzaldehyde thiosemicarbazone (DMABTS), was prepared in order to find available fluorescent chemosensor for mercuric ion in aquesous solution. DMABTS emitted fluorescence at 448 nm in aqueous solution and its fluorescence intensity was completely quenched upon interaction with Hg²⁺ ions, which should be attributed to the 1:1 complex formation between DMABTS and Hg²⁺. The binding constant of the complex was determined as 7.48 × 10⁶ mol l⁻¹. The linear range of quantitative detection of 0 to 5.77 × 10⁻⁶ mol l⁻¹ and the detection limit of 7.7 × 10⁻⁷ mol l⁻¹ for Hg²⁺ in the 6.3 × 10⁻⁶ mol l⁻¹ DMABTS aqueous solution were obtained from a calibration curve. The coexistence of several transition metal ions and anions did interfere the fluorometric titration of Hg²⁺ ion by less than 4% in the emission change.     

Development of a test strip based on DNA-functionalized gold nanoparticles for rapid detection of mercury(II) ions

A rapid,sensitive,selective and reliable strip assay based on DNA-functionalized gold nanoparticles for Hg²⁺ detection has been developed,with a detection limit 5 nmol/L.The measurement principle was based on thymine-Hg²⁺-thymine(T-Hg²⁺-T) coordination chemistry and streptavidin-biotin interaction.The major advantages of this assay are that results can be read visually without any instrument in less than 10 min and that it does not require any sample pretreatment.