An efficient and selective flourescent chemical sensor based on 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane as a new fluoroionophore for determination of iron(III) ions. A novel probe for iron speciation

A novel fluorescent chemical sensor for the highly sensitive and selective determination of Fe³⁺ ions in aqueous solutions is prepared. The iron sensing system was prepared by incorporating 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L) as a neutral Fe³⁺-selective fluoroionophore in the plasticized PVC membrane containing sodium tetraphenylborate as a liphophilic anionic additive. The response of the sensor is based on the strong fluorescence quenching of L by Fe³⁺ ions. At pH 5.5, the proposed sensor displays a calibration curve over a wide concentration range from 6.0 × 10⁻⁴ to 1.0 × 10⁻⁷ M, with a relatively fast response time of less than 2 min. In addition to a high stability and reproducibility, the sensor shows a unique selectivity toward Fe³⁺ ion with respect to common coexisting cations. The proposed fluorescence optode was applied to the determination of iron(III) content of straw of rice, spinach and different water samples. The fluorescent sensor was also used as a novel probe for Fe³⁺/Fe²⁺ speciation in aqueous solution.     

Study on the synthesis of novel fluorescent macrocyclic sensors and their sensitive properties for Cu2+ and Fe3+ in aqueous solution

In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li⁺, Na⁺, K⁺, Ag⁺, Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Zn²⁺, Co²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Cr³⁺, Al³⁺, Fe³⁺) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu²⁺ and Fe³⁺ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H₂O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated.     

Electrospun nanofiber based colorimetric probe for rapid detection of Fe in water

An imidazole derivative, 2-(2′-pyridyl)imidazole (PIMH), was developed as a colorimetric probe for the qualitative analysis of Fe²⁺ in aqueous solution. PIMH was then used to post-functionalize poly(vinylbenzyl chloride) (PVBC) nanofibers after electrospinning so as to afford a solid state colorimetric probe. Upon treatment with Fe²⁺ the probe displayed a distinctive color change both in liquid and solid platforms. The linear dynamic range for the colorimetric determination of Fe²⁺ was 0.0988–3.5 μg mL⁻¹. The ligand showed a high chromogenic selectivity for Fe²⁺ over other cations with a detection limit of 0.102 μg mL⁻¹ in solution (lower than the WHO drinking water guideline limit of 2 mg L⁻¹), and 2 μg mL⁻¹ in the solid state. The concentration of Fe²⁺ in a certified reference material (Iron, Ferrous, 1072) was found to be 2.39 ± 0.01 mg L⁻¹, which was comparable with the certified value of 2.44 ± 0.12 mg L⁻¹. Application of the probe to real samples spiked with Fe²⁺ achieved recoveries of over 97% confirming accuracy of the method and its potential for on-site monitoring.     

Preparation of ethambutol-copper(II) complex and fabrication of PVC based membrane potentiometric sensor for copper

Copper(II) complex of ethambutol (I) was prepared and used in the fabrication of Cu(2+) selective ISE membrane. The membrane having Cu(II)-ethambutol complex (I) as electroactive material, along with sodium tetraphenylborate (NaTPB) as anion discriminator, dioctylphthalate (DOP) as plasticizer in poly(vinyl chloride) (PVC) matrix in the percentage ratio 6:2:190:200 (I:NaTPB:DOP:PVC) (w/w) gave a linear response in the concentration range 7.94x10(-6) to 1.0x10(-1) M of Cu(2+) with a slope of 29.9+/-0.2 mV per decade of activity and a fast response time of 11+/-2 s. The sensor works well in the pH range 2.1-6.3 and could be satisfactorily used in presence of 40% (v/v) methanol, ethanol and acetone and is selective for copper over a large number of cations with slight interference from Na(+) and Co(2+) if present at a level 1.5x10(-5) and 6.5x10(-5) M, respectively. It works well over a period of 6 months and can also be used as indicator electrode for the end point determination in the potentiometric titration of Cu(2+) against EDTA as well as in the determination of Cu(2+) in real samples.     

Novel naphthalene-based fluorescent chemosensors for Cu2+ and Fe3+ in aqueous media

Three novel compounds bearing 2,7-dihydroxylnaphthalene capable of detecting Cu²⁺ or Fe³⁺ have been synthesised based on photoinduced electron transfer. The ability of these compounds for complex transition metal ions has been studied, and complex stoichiometry for Cu²⁺ and Fe³⁺ complex has been determined in the Tris–HCl (0.01 M DMSO/H₂O (v/v) 1:1, buffer, pH 7.4) solution system by fluorescence titration experiments. These chemosensors form a 1:1 complex with Cu²⁺ or Fe³⁺ and show a fluorescent quenching with a binding constant of (4.46 ± 0.29) × 10³ and (8.04 ± 0.26) × 10⁴, respectively.     

A new lawsone azo-dye for optical sensing of Fe3+ and Cu2+ and their DFT study

A new lawsone-based azo-dye 2-hydroxy-3-((pyridin-2-ylmethyl)diazenyl)naphthalene-1,4-dione (1) was synthesized and applied for sensing of metal ions. Receptor 1 showed selective fluorescent and colorimetric response for the detection of Cu²⁺ and Fe³⁺ over other tested metal ions. The fluorescence intensity of 1 was significantly quenched allowing detection of Fe³⁺ and Cu²⁺ down to 0.61 and 6.06 μM, respectively. The binding has been established by fluorescence spectroscopic method. Receptor 1 provided a 1?:?1 binding scaffold for recognition of Fe³⁺ and Cu²⁺ ions with the association constant of 3.33 × 10⁶ and 3.33 × 10⁵ M^?1, respectively. The B3LYP/6-31G/LANL2DZ method was employed for the optimization of 1 and 1·Fe³⁺ and 1·Cu²⁺.     

Ratiometric fluorescent and colorimetric sensors for Cu based on 4,5-disubstituted-1,8-naphthalimide and sensing cyanide via Cu displacement approach

Two 4,5-disubstituted-1,8-naphthalimide derivatives 1 and 2 were synthesized as ratiometric fluorescent and colorimetric sensors for Cu²⁺, respectively. In 100% aqueous solutions of 1, the presence of Cu²⁺ induces a strong and increasing fluorescent emission centered at 478 nm at the expense of the fluorescent emission of 1 centered at 534 nm. Compound 2 senses Cu²⁺ by means of a colorimetric (primrose yellow to pink) method with a thorough quench in emission attributed to the deprotonation of the secondary amine conjugated to the naphthalimide fluorophore. 1-Cu²⁺ and 2-Cu²⁺ sense cyanide in ratiometric way via colorimetric and fluorescent changes.     

Dansyl-styrylquinoline conjugate as divalent iron sensor

Synthesis and photophysical studies of a simple and efficient dansyl-styrylquinoline conjugate (DansSQ) which shows excellent selectivity toward Fe²⁺ over other transition metal ions including Fe³⁺ are described. The fluorescent emission of DansSQ at 450 nm was enhanced upon addition of Fe²⁺ in the presence of common interfering metal ions in background. These studies suggest that DansSQ could be used as fluorescent sensor for Fe²⁺.     

苯乙烯三嗪衍生物的合成及在重金属离子识别中的应用

合成了2,4-二(2-噻吩乙烯基)-6-(4'-N,N-二甲氨基苯乙烯基)-1,3,5-均三嗪(2)并鉴定了其结构。在乙腈-水混合介质中,化合物2在355和416nm处呈现双吸收峰,加入Cu²⁺,Hg²⁺ 和Fe³⁺ 后,均在520nm附近形成新的吸收峰。化合物2与Cu²⁺、Hg²⁺ 和Fe³⁺ 均形成1:1型配合物,其结合常数分别为1.9×10⁵L·mol^-1,6.6×10³L·mol^-1,2.7×10³L·mol^-1。对照化合物4与金属离子的光谱响应与化合物2相似,仅吸收峰的位置不同。因此,可认为化合物2和4中三嗪环中的N和噻吩环中的S与Cu²⁺、Hg²⁺ 和Fe³⁺ 共同配位形成了稳定的金属配合物。     

A novel colorimetric and fluorescent chemosensor: synthesis and selective detection for Cu and Hg

A novel two-channel metal ion sensor has been synthesized from macrocyclic dioxotetraamine and 1,8-naphthalimide derivative. The metal ion-selective signaling behaviors of the sensor were investigated. The sensor presented the selective coloration for Cu²⁺ and Hg²⁺ that can be detected by the naked-eye, respectively. Besides, the addition of Cu²⁺ and Hg²⁺ quenched the fluorescence of 1 obviously and the detection limit was found to be 3 × 10⁻⁷ M for Cu²⁺ and 7 × 10⁻⁷ M for Hg²⁺. This sensor can be utilized for the visual and spectroscopic detection of Cu²⁺ or Hg²⁺ in the presence of the other competing metal ions.     

Coumarin-based symmetrical bisamide as fluorescent and colorimetric probes for copper ions

Coumarin-based new symmetrical bisamide 1 has been designed and synthesised. The bisamide 1 fluorometrically recognises Cu²⁺ in CH₃CN containing 0.06% DMSO by exhibiting an increase in emission upon complexation. In comparison, the isomeric structure 2 also reports the selectivity for Cu²⁺ under identical condition by showing an opposite mode of emission. In addition, Cu²⁺ gives rise to a change in colour of the solution of 1, which is clearly visible to the naked eye.     

A selective turn-on fluorescent sensor for Fe and application to bioimaging

A novel compound FD1 was demonstrated as a turn-on fluorescent sensor for imaging of iron(III) ion in biological samples. Based on the spirolactam (nonfluorescence) to ring-open amide (fluorescence) equilibrium, FD1 exhibited high selectivity and sensitivity for Fe³⁺ over other metal ions. Moreover, fluorescent microscopy experiments further established that FD1 could be used for sensing Fe³⁺ within living cells.     

Adsorption of copper(II) ions by keratin/PA6 blend nanofibres

Mats of randomly oriented nanosized filaments, prepared by electrospinning wool keratin/polyamide 6 blends in formic acid, were evaluated as adsorbents of Cu²⁺ ions. The adsorption capacity was evaluated as a function of the nanofibre composition, specific surface area, initial metal ion concentration, contact time and pH of the solution. The adsorption tests revealed that keratin-based nanofibres highly adsorb Cu²⁺ ions and the adsorption capacity increases with increasing the specific surface area of the nanofibre mats. The maximum adsorption capacities for nanofibre mats containing 50%, 70% and 90% (wt.%) of keratin were found to be 61.7 (mg/g), 90 (mg/g) and 103.5 (mg/g), respectively. The Cu²⁺adsorption onto the keratin rich nanofibres is highly pH-dependent and the optimum pH was found above the isoelectric point of keratin. The experimental data fit the pseudo second-order kinetic model. Infrared analysis demonstrated the formation of complexes between Cu²⁺ ions and keratin that involve terminal free carboxyl groups of the protein.     

A highly selective visual and fluorescent sensor for Pb2+ and Zn2+ and crystal structure of Cu2+ complex based-on a novel single-armed Salamo-type bisoxime

A novel single-armed Salamo-type bisoximes (H₄L) has been designed and synthesised. An obvious colour change from yellow (H₄L) to pale pink (HL-Pb²⁺) which can be visually observed by the naked eye in visible light. H₄L can act as a fluorescent sensor for ratiometric recognition of Zn²⁺ with high selectivity and sensitivity. Crystallographic data of the [Cu(HL)(μ-OAc)Cu] reveals that the two Cu²⁺ ions are both penta-coordinated with square pyramidal geometries, and forms a 2D supramolecular plane structure by hydrogen bonding interactions.     

Azo 8-hydroxyquinoline benzoate as selective chromogenic chemosensor for Hg and Cu

Azo 8-hydroxyquinoline benzoate (2) was synthesized and studied to detect metal ions. Distinct color change was found for compound 2 in the presence of transition metal ions Hg²⁺ or Cu²⁺ in CH₃CN, respectively, which makes it possible for distinguishing Hg²⁺ and Cu²⁺ from other metal ions by the ‘naked eye’.     

An off-on fluorescent sensor with high selectivity and sensitivity for Fe(III)

A new fluorescent derivative (1) containing coumarin exhibits Fe(III)-selective strong yellow-green fluorescence in ethanol. This compound could be used as an “off-on” chemosensor and allow the detection of Fe³⁺ by monitoring changes in absorption and fluorescence spectra. Upon addition of Fe³⁺, an overall emission change of 125-fold was observed. High selectivity and sensitivity were observed over other metal ions, mainly due to the spirolactam ring-opening power of Fe³⁺. The detection limit was as low as 5.6?ppb. Photo-induced electron transfer, coupled with intramolecular charge transfer are proposed to account for the observed spectral response.     

Supramolecular chemosensor for selective detection of iron in aqueous medium

We have successfully developed a ‘turn-on’ colorimetric chemosensor for Fe³⁺ based on 1,10-phenanthroline. An amide derivative of 1,10-phenanthroline 4 was developed for the selective recognition of Fe³⁺ over Co²⁺, Cr³⁺, Cu²⁺, Mn²⁺, Ni²⁺, Ag⁺ and Zn²⁺ and could measure Fe³⁺ concentration in the range of 15–210 μM by UV–vis spectroscopy. Moreover, the addition of Fe³⁺ to a colourless solution of 4 turned its colour to light pink, indicating that 4 is capable of detecting Fe³⁺ by the naked eye. Compound 4 exhibits a major absorption band centred at 268 which shifted to 278 nm after addition of Fe³⁺, and a shoulder band around 514 nm was also observed. The complexation of Fe³⁺ with 4 was analysed at a different pH and favourable binding was observed at pH 6.2.     

Facile Synthesis of Aminated Graphene Quantum Dots for Promising and Selective Detection of Cobalt and Copper Ions in Aqueous Media

Due to the rapid development of industrialization, various environmental problems such as water resource pollution are gradually emerging, among which heavy metal pollution is harmful to both human beings and the environment. As a result, there are many metal ion detection methods, among which fluorescence detection stands out because of its rapid, sensitive, low cost and non-toxic characteristics. In recent years, graphene quantum dots have been widely used and studied due to their excellent properties such as high stability, low toxicity and water solubility, and have a broad prospect in the field of metal ion detection. A novel high fluorescence Cu²⁺, Co²⁺ sensing probe produced by graphene quantum hydrothermal treatment is reported. After heat treatment with hydrazine hydrate, the small-molecule precursor nitronaphthalene synthesized by self-nitrification was transformed from blue fluorescent GQDs to green fluorescent amino-functionalized N–GQDs. Compared with other metal ions, N–GQDs are more sensitive to Cu²⁺ and Co²⁺ on the surface, and N–GQDs have much higher selectivity to Cu²⁺ and Co²⁺ than GQDs. The strategy proposed here is simple and economical in design.     

过渡金属大环配合物的研究——Ⅱ.1,7-二氮杂-4,10-二硫杂-环十二烷过渡金属配合物的研究

本文报导了三种过渡金属氯化物(CuCl₂、CoCl₂、NiCl₂)和1,7-二氮杂-4,10-二硫杂-环十二烷([12]N₂S₂)的1:1配合物及其UV、IR、ESR和XPS等波谱特征。