A ratiometric fluorescent sensor for zinc(II) with high selectivity

Spectroscopic studies revealed that the compound [N,N′-di(quinoline-2-methylene) -1,2-phenylenediimine] (1) exhibited a rather high selectivity toward Zn²⁺ over other metal ions, even Cd²⁺. In acetonitrile, the red shift of fluorescent emission from 396 nm to 426 nm upon zinc binding is due to the formation of a 1:1 metal/ligand complex.     

A new rhodamine-based single molecule multianalyte (Cu, Hg) sensor and its application in the biological system

A new single molecule multianalyte sensor, vanillic aldehyde rhodamine 6G hydrazone has been designed for the selective detection of Cu²⁺ and Hg²⁺ ions. UV/Vis spectroscopy indicates that the sensor is a good chromogenic chemosensor for Cu²⁺ in 1:99 (v/v) ethanol-water media. Whereas, other ions, such as Li⁺, Na⁺, Mg²⁺, K⁺, Ca²⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Ag⁺, Cd²⁺, Ba²⁺, Hg²⁺ and Pb²⁺ failed to generate a distinct response. Fluorescence spectral data reveals that the sensor is an excellent fluorescent chemosensor for Hg²⁺ in aqueous ethanol solution and with no fluorescent response toward other ions. The spectroscopic behavior of the sensor in living cells indicated that it can be used for the detection of Cu²⁺ and Hg²⁺ in environmental and biological systems. Mechanisms for the high selectivity of the sensor to Cu²⁺ and Hg²⁺ are discussed.     

(R,R)-salen/salan-based polymer fluorescence sensors for Zn detection

(R,R)-salen-based polymer fluorescence sensor P-1 could be synthesized by the polymerization of 5,5′-(isoquinoline-5,8-diylbis(ethyne-2,1-diyl))-bis(3-tert-butyl-2-hydroxybenzaldehyde) (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via nucleophilic addition-elimination reaction, and (R,R)-salan-based polymer sensor P-2 could be obtained by the reduction reaction of P-1 with NaBH₄. The fluorescence response behaviors of two chiral polymers P-1 and P-2 on Zn²⁺ were investigated by fluorescence spectra. The fluorescence intensities of P-1 and P-2 can exhibit gradual enhancement upon addition of Zn²⁺. Compared with other cations, such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Cd²⁺, Cr³⁺ and Pb²⁺, Zn²⁺ can lead to the pronounced fluorescence enhancement as high as 22.8-fold for P-1 and 3.75-fold for P-2, respectively. The results show that P-1 and P-2 incorporating (R,R)-salen/salan moieties as receptors in the polymer main chain backbone can exhibit high sensitivity and selectivity for Zn²⁺ detection.     

连续识别Zn2+和草甘膦荧光探针的合成与应用

以2-巯基苯并噻唑为原料,设计合成了一种结构简单的苯并噻唑类荧光探针NSS,并通过IR、HRMS、1HNMR、13CNMR等对其结构进行表征。荧光发射光谱表明,在DMSO溶液中,探针NSS实现了Zn2+的“Turn-ON”型检测,具有响应时间短、特异性强、抗干扰性强等优点。探针NSS荧光强度与Zn2+浓度（0～11 μmol/L）呈现良好的线性关系,检出限达19.1 nmol/L,并与Zn2+形成1:1络合物。同时,络合物NSS-Zn2+对草甘膦呈现特异性的荧光猝灭响应,猝灭率达99.4%,检出限16.0 nmol/L（2.68 ng/mL）,且不受其它有机磷农药的干扰。此外,探针NSS成功应用于实际水样中Zn2+和草甘膦的检测,具有良好的应用前景。     

连续识别Zn2+和草甘膦荧光探针的合成与应用

以2-巯基苯并噻唑为原料,设计合成了一种结构简单的苯并噻唑类荧光探针2-[2-(苯并噻吩-2-基亚甲基)肼基]苯并噻唑(简称NSS),并通过FTIR、HRMS、¹HNMR、¹³CNMR对其结构进行了表征。荧光光谱表明,在二甲基亚砜中,探针NSS实现了Zn²⁺的“关-开”型检测,具有响应时间短(30 s)、特异性强、抗干扰性强等优点。探针NSS荧光强度与Zn²⁺浓度(0～11μmol/L)呈现良好的线性关系,检出限达19.1 nmol/L,并与Zn²⁺形成物质的量比为1∶1的络合物。同时,络合物NSS-Zn²⁺对草甘膦呈现特异性的荧光猝灭响应,猝灭率达99.4%,检出限16.0 nmol/L(2.71 ng/mL),且不受其他有机磷农药的干扰。     

A highly selective chemosensor for Cu and Al in two different ways based on Salicylaldehyde Schiff

A novel, easily available colorimetric and fluorescent double-sensor 1 based on Salicylaldehyde bis-Schiff has been investigated in this work. The sensor exhibits highly selective and sensitive recognition toward Cu²⁺ in aqueous solution via a naked eye colour change from colourless to yellow and toward Al³⁺ via a significant fluorescent enhancement in ethanol over a wide range of tested metal ions. This represents the first reported Salicylaldehyde Schiff-based sensor capable of detecting both Cu²⁺ and Al³⁺ using two different modes.     

The effect of tert-butanol adsorption on the two-step electroreduction of Zn and its dependence on the NaClO4 concentration

The influence of water molecules on the adsorption of organic substances and kinetics of electroreduction of inorganic depolarizers is very often overlooked. The electroreduction of Zn²⁺ is a typical example of a reaction controlled by both diffusion and charge transfer. This process in 1.0, 0.5 and 0.1 M NaClO₄ solutions at a mercury electrode in the presence of tert-butanol is expected to involve two consecutive one-electron transfer steps in the overall reaction. Solutions of tert-butanol were prepared to cover the concentration range from 0.01 to 0.3 M. Measurements were performed using an impedance method for a wide range of both the potential and frequency. The difference between the potential of the anodic and cathodic peaks, which was obtained from the cyclic voltammetry method, increases with an increase in the concentration of both tert-butanol and NaClO₄. From the dependences of , the true standard rate constants and the constants and characterizing the stage of the first electron transfer and the stage of the second electron exchange, respectively, were determined. The obtained results indicate that the inhibiting properties of tert-butanol are the weakest in 0.1 M NaClO₄. In addition the stage of the second electron transfer is less sensitive to the inhibiting effect of tert-butanol than the stage of the first electron exchange.     

One-pot synthesis of fluorescent mesoporous materials for detection of the presence of Be<Superscript>2+</Superscript> ion

A fluorescent mesoporous silica solid (F-MCM-41) has been successfully prepared by one-pot hydrothermal synthesis from TEOS and 2-((3-(triethoxysily)propylimino)methyl)phenol in the presence of CTMABr surfactant, followed by removal of CTMABr in F-MCM-41 from extraction of ethanol solution at 50 °C for 5 h. The fluorescent sample was characterized with X-ray diffraction, nitrogen isotherms, nuclear magnetic resonance (NMR), and fluorescence spectroscopy, and the obtained results show that the sample has ordered hexagonal mesoporous symmetry, uniform pore size, high BET surface area, large pore volume as well as good fluorescent properties. When this sample is used to detect Be²⁺ ions in water, the degree of fluorescence quenching is dependent on the concentration of Be²⁺ solutions ranged from 1 to 20 μg/L.     

A new Cu-selective self-assembled fluorescent chemosensor based on thiacalix[4]arene

A new ON–OFF fluorescent chemosensor for Cu²⁺ ions was prepared through self-assembly inside Triton X-100 micelles of p-tert-butylthiacalix[4]arene (TCA) and perylene in water solution. This thiacalix[4]arene-based self-assembled fluorescent chemosensor could realize the direct sensing of Cu²⁺ ions in aqueous solution. Addition of Cu²⁺ ions could result in a quenching of the fluorescence emission of perylene inside the micelles, which is ascribed to intramicellar complex-fluorophore electron-transfer or energy-transfer effects induced by the complexation of TCA with the Cu²⁺ ions. Cu²⁺ ions can be detected selectively in the presence of other metal ions (Zn²⁺, Pb²⁺, Cd²⁺, Mn²⁺, Ni²⁺, Al³⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and its concentration in the submicromolar range can be almost linearly determined according to the fluorescence quenching.     

The effect of cytosine on the two-step electroreduction of Zn ions in acetic buffers

Cytosine plays an important role in many biological processes since it constitutes the buildings blocks of DNA and RNA. A two-step reduction of Zn²⁺ ions at the dropping mercury electrode in acetic buffers at pH 4 and 5 in the presence of cytosine was examined. The measurements were performed using an impedance method in a wide potential and frequency ranges.The values of the standard rate constants k_s in the both studied system decrease from 3.8 × 10⁻³ to 2 × 10⁻³ cm s⁻¹ at pH 4 and from 5.1 × 10⁻³ to 2.5 × 10⁻³ cm s⁻¹ at pH 5. The values of the standard rate constants k_s1 characterizing the stage of the first electron transfer decrease similarly. However, the values of the standard rate constants k_s2 characterizing the stage of the second electron exchange decrease more markedly in the buffer at pH 4 than in the buffer at pH 5.     

A benzothiazole-based semisquarylium dye suitable for highly selective Hg sensing in aqueous media

A novel semisquarylium dye was synthesized by the reaction between 3,4-dibutoxy-3-cyclobutene-1,2-dione and a benzothiazolium salt and its metal ion sensing properties were investigated using absorption and emission spectroscopy. These misquarylium exhibited high selectivity for Hg²⁺ ions, as compared with Ca²⁺, Pb²⁺, Al³⁺, Ce²⁺, Ba²⁺, Ni²⁺, Cd²⁺, Zn²⁺ and Mg²⁺ ions in DMSO/H₂O (9:1, v/v), which was attributed to the formation of a 2:1 BSQ:Hg²⁺ coordination complex, the formation of which was supported by the calculated geometry of the complex.     

Kevlar-functionalized graphene nanoribbon for polymer reinforcement

Multiwalled carbon nanotubes (MWCNTs) have been widely used as reinforcement fillers in past decades. However, the reinforcement effect has been greatly hindered by the limited available interface area (AIA) with polymer matrices for polymer composites. Successively, the method of oxidative unzipping MWCNTs into graphene nanoribbons (GNRs) was demonstrated to be the effective way for addressing the inherent drawback of MWCNTs. However, the GNRs are easy to agglomerate in polymer matrix even at relatively low loading amount. In this paper, we found that the functionalization of GNRs with Kevlar^® can significantly improve the dispersion state of GNRs in polymer matrix. Consequently, Kevlar^®-functionalized graphene nanoribbons (KGNRs) were successfully prepared through non-covalent functionalization of π–π stacking interaction between the aromatic area of Kevlar^® and the graphitic surface of GNRs. As-prepared KGNRs were characterized by FT-IR, TGA, XRD and TEM measurements. Poly(vinyl chloride) (PVC) and poly(methyl methacrylate) (PMMA) were selected as model polymers to investigate the reinforcement effect of KGNRs. The KGNRs could be well dispersed in PVC and PMMA matrices at relatively high loading level. Meantime, the ultimate tensile strengths and Young's modulus of KGNRs/PVC and KGNRs/PMMA composite films were significantly improved. Based on the observations above, KGNRs hold great promise in many potential applications in the future.     

Fluoranthene-based pyridine as fluorescent chemosensor for Fe

A fluoranthene based fluorescent chemosensor 2-(7,10-diphenyl-fluoranthen-8-yl)-pyridine (B) which shows excellent selectivity towards Fe³⁺ is described. Upon addition of FeCl₃ into the ethanol solution of B, it exhibits a great decrease of emission intensity against environmental and biological samples. Further experiments demonstrate that Fe(NO₃)₃ has the similar influence as FeCl₃ on the emission spectra of B while Fe₂(SO₄)₃ has no influence on that of B.     

Adsorption behavior and kinetics of exchange of Co2+ and Eu3+ ions on polymer composite ion exchanger

Equilibrium and kinetics of exchange of ⁶⁰Co and ^152+154Eu radionuclides on hydrous titanium oxide incorporated in polyacrylonitrile, TiO-OH-PAN, were studied. The capacities of TiO-OH-PAN for ⁶⁰Co and ^152+154Eu were found to be 2.35 and 2.69 meq/g respectively. Freundlich and Langmiur isotherms were investigated. The validity of the Langmuir isotherm over the specified concentration range indicates monolayer coverage of the surface of TiO-OH-PAN by cobalt and europium. Sorption data was treated with the Dubinin-Radushkevich equation. The results indicated that hydrous titanium oxide incorporated in polyacrylonitrile can be considered as a promising material for removal of cobalt and europium ions from aqueous solution.     

Potentiometric SO2 gas sensor based on a thick film of Ca2+ ion conducting solid electrolyte

A planar miniaturized SO₂ sensor based upon a thick film of Ca²⁺ ion conductor-CaO·0.6MgO·6Al₂O₃ (CMA) with a Na₂SO₄ auxiliary electrode and a Pt/O₂ reference electrode was fabricated and tested. The thick film was fabricated by screen-printing CMA ink on an alumina substrate and then fired at 1823 K. The solid electrolyte was interfaced with a sodium sulphate auxiliary phase containing Pt paste and the sensor showed a good SO₂ response at 873–1073 K. The electromotive force (emf) values obtained were linearly dependent upon the logarithm values of SO₂ concentration in a range of 10–500 ppm. Both the electrodes were exposed to the same test gas thus eliminating the need to separate the electrode chambers.     

A Novel Highly Copper(ll)-selective Chelating Ion Exchanger Based on Poly(Glycidyl Methacrylate-coethylene Dimethacrylate) Beads Modified with Aspartic Acid Derivative

Abstract

Anchoring the hydroxyaspartic acid onto poly(glycidyl methacrylate-co-ethylene dimethacrylate) (poly(GMA-co-EDMA)) beads or epoxysuccinic acid onto ammoniummodified poly(GMA-co-EDMA) beads resulted in a novel chelating resin, which contained up to 0.37 mmol of the ligand per gram of resin. Batch extraction experiments showed a very high selectivity for Cu²⁺ over Zn²⁺ and Cd²⁺ ions in buffered solutions under competitive conditions.     

A fluorescent color/intensity changed chemosensor for Fe by photo-induced electron transfer (PET) inhibition of fluoranthene derivative

A fluorescent color/intensity changed fluoranthene derivative chemosensor for Fe³⁺ has been prepared and confirmed by ¹H-NMR, ¹³C-NMR, HRMS, and crystal data, which displays a high selectivity and antidisturbance for Fe³⁺ among environmentally and biologically relevant metal ions. Fluorescence studies show that fluorescent emission peak blue shifts about 100 nm with fluorescent intensity enhancing 75-fold, indicating a Fe³⁺-selective dual-emission behavior. Further study demonstrates the detection limit on fluorescence response of the sensor to Fe³⁺ is down to 10⁻⁷ M range. The fluorescence signals of chemosensor can be restored with o-phenanthroline, showing the binding of chemosensor and Fe³⁺ is really chemically reversible.     

Novel thermo-responsive membranes composed of interpenetrated polymer networks of alginate-Ca and poly(N-isopropylacrylamide)

In this work, interpenetrated polymer networks (IPN) composed of alginate-Ca²⁺ and poly(N-isopropylacrylamide), PNIPAAm, were synthesized and their water uptake capability was measured at temperatures from 25 to 40 °C and compared to that of pure alginate-Ca²⁺ hydrogels without PNIPAAm. A sharp decrease of WU was observed when IPN hydrogels are heated above 32-33 °C. The phenomenon is associated to a drastic shrinking of hydrogels. At temperatures above 32 °C the PNIPAAm chains collapse, contracting their network and pulling back the alginate-Ca²⁺ network. The rate of shrinking depends of the heating rate. The phenomenon is more effective and faster in IPN containing lower amount of alginate-Ca²⁺. The shrunken IPN hydrogels can be re-swollen but the expansion is slower than the shrinking. The diffusion of Orange II dye through the membrane of IPN hydrogels decreases if the temperature is raised up to 35 °C. The shrinking results in a decrease of the average pores size that makes more difficult the diffusion of Orange II. The average pore size was evaluated in several stages by analysis of SEM micrographs of freeze dried samples: 102.0±14.3 μm at 25 °C, 15.7±5.4 μm at 33 °C and 0.4±0.3 μm at 40 °C. Below the LCST of PNIPAAm, the IPN hydrogels exhibit a morphology characterized by open pores but above the LCST their surface becomes more regular and compact. As a consequence, an increase of the apparent activation energy for permeability, , of Orange II is measured.     

A fluorescence sensor based on chiral polymer for highly enantioselective recognition of phenylalaninol

The chiral polymer P-1 incorporating (S)-2,2′-binaphthol (BINOL) and (S)-2,2′-binaphthyldiamine (BINAM) moieties in the main chain of the polymer backbone was synthesized by the polymerization of (S)-6,6′-dibutyl-3,3′-diformyl-2,2′-binaphthol (S-M-1) with (S)-2,2′-binaphthyldiamine (S-M-2) via nucleophilic addition-elimination reaction, and the chiral polymer P-2 could be obtained by the reduction reaction of P-1 with NaBH₄. The fluorescence intensity of the chiral polymer P-1 exhibits gradual enhancement upon addition of (d)- or (l)-phenylalaninol and keeps nearly a linear correlation with the concentration molar ratios of (d)- or (l)-phenylalaninol. The value of enantiomeric fluorescence difference ratio (ef) is 6.85 for the chiral polymer on (d)-phenylalaninol. On the contrary, the chiral polymer P-2 shows no obvious fluorescence response toward either (d)- or (l)-phenylalaninol.