Proton "off-on" behaviour of methylpiperazinyl derivative of naphthalimide: a pH sensor based on fluorescence enhancement

In a search for new type pH sensing fluorophores, the possibility of using the proton "off-on" switch behaviour of naphthalimide derivatives for optical pH sensor preparation has been explored. A new compound, N-allyl-4-(4[prime or minute]-methyl-piperazinyl)-1,8-naphthalimide (AMPN), was synthesized. The enhancement of fluorescence of AMPN with the increase of hydrogen ion concentration is based on arresting photo-induced electron transfer to the naphthalimide fluorophore from aliphatic amine group after its protonation. The Stokes Shift of the proposed type of pH sensing fluorophore is significantly larger than that of the fluorescein counterparts. To avoid the leakage of the fluorophore, AMPN was photo-copolymerized with 2-hydroxyethyl methacrylate and acrylamide on the glass surface. The fluorescence intensity of membrane contacted with a pH 3.50 buffer is 4.7 times of that for pH 12.00 buffer solutions. The proposed pH sensor is not susceptible to ionic strength and shows good selectivity, repeatability and short response time. The membrane shows a good stability with a lifetime over two months. The sensor can be used for the determination of pH in the range of pH 4.5-9.0, without interference of most commonly co-existing inorganic ions and some organic species. The sensor has been applied to the analysis of urine samples.     

Reactive sensing of gold (III) by coumarin tethered fluorescent probe through alkyne activation

A novel strategy, involving anchoring and un-anchoring of coumarin based fluorophore, has been established for the selective detection of Au³⁺ species. Selective sensing of Gold (Au³⁺) was triggered due to alkynophilicity of gold ions to create lateral fluorescence of a latent fluorophore. The 4-methyl-2-oxo-2H-chromen-7-yl 2-(2-phenylethynyl) benzoate (CEB) probe was synthesized by reacting 7-hydroxy-4-methylcoumarin with iodo-benzoic acid. CEB probe has an absorption at 300 nm and 335 nm which decreases gradually and new absorption appeared at 406 nm due to Au³⁺ promoted ester hydrolysis selectively over other metal ions with great sensitivity, which accompanies a turn on fluorescence change produced by 7-hydroxy coumarin. The principle behind this sensing strategy is activation of triple bond induced uniquely by Au⁺³ ions leading to cascade and delivers active fluorophore. The sensing mechanism was proposed and supported by ¹H NMR, MS and TD-DFT experiments. The density functional theory (DFT) and time dependent density functional theory (TD-DFT) theoretical results of the CEB-probe and Au³⁺ reaction is in good agreement with the experimental results. Additionally, probe could be well incorporated onto the test strips for effective detection of Au^3+.     

Synthesis of dipicolylamino substituted quinazoline as chemosensor for cobalt(II) recognition based on excited-state intramolecular proton transfer

A new fluorescent chemosensor for sensing Co(II) using di(2-picolyl)amino (DPA) as a recognition group and quinazoline as a reporting group has been synthesized and characterized. The quinazoline derivative contains an intramolecular hydrogen bond, which would undergo excited-state intramolecular proton transfer (ESIPT) at illumination. The fluorescence quenching is attributed to cation-induced inhibition of ESIPT, which constitutes the basis for the determination of Co(II) with the prepared chemosensor. The fluorophore forms 1:1 cobalt(II) complex with the logarithm of apparent dissociation constant log K(a)=6.8. The analytical performance characteristics of the proposed Co(II)-sensitive sensor were investigated. The chemosensor exhibits a linear response toward Co(II) in the concentration range 3.2 x 10(-8) to 1.4 x 10(-6) M, with a working pH range from 7.0 to 9.5 and high selectivity.     

Esterase-activated two-fluorophore system for ratiometric sensing of biological zinc(II)

Intracellular ester hydrolysis by cytosolic esterases is a common strategy used to trap fluorescent sensors within the cell. We have prepared analogues of Zinpyr-1 (ZP1), an intensity-based fluorescent sensor for Zn2+, that are linked via an amido-ester or diester moiety to a calibrating fluorophore, coumarin 343. These compounds, designated Coumazin-1 and -2, are nonpolar and are quenched by intramolecular interactions between the two fluorophores. Esterase-catalyzed hydrolysis generates a Zn2+-sensitive ZP1-like fluorophore and a Zn2+-insensitive coumarin as a calibrating fluorophore. Upon excitation of the fluorophores, coumarin 343 emission relays information concerning sensor concentration whereas ZP1 emission indicates the relative concentration of Zn2+-bound sensor. This approach enables intracellular monitoring of total sensor concentration and provides a ratiometric system for sensing biological zinc ion.     

适于测定苄胺的可逆光敏膜的研究

本文报道了一种测定苄胺的可逆光敏膜.将作为苄胺离子载体的联萘冠醚和亲脂的pH指示剂,结合在增塑的PVC膜中,苄胺离子与氢离子在膜相的竞争引起膜的吸光值变化.报道了该传感器的响应特性,推导了有关的理论关系式.     

Novel fluorescent pH sensor based on 5-(4-carboxy-phenyl)-10,15,20-tris(phenyl)-porphyrin

A novel fluorescent pH sensor based on 5-(4-carboxy-phenyl)-10,15,20-tris(phenyl)-porphyrin, as sensing agent, has been developed. The carboxyl functionalized asymmetric porphyrin has been synthesized and characterized by high performance liquid chromatography (HPLC), thin layer chromatography (TLC), proton nuclear magnetic resonance (¹H NMR), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible (UV–vis), emission, excitation and mass spectrometry (MS) spectra. Optical and fluorescence behaviors were investigated in relationship with variation of acid concentration in the range of acid pH from 1.5 to 5.5. Upon increasing the acidity of the solution, the decrease of the fluorescence intensity was noticed, as a linear function of pH. Different metal ions were tested to put into evidence the changes regarding the fluorescence intensity, but the fluorescence obtained results revealed no significant interference on pH determination. The conclusion is that the proposed fluorescent sensor can measure pH in acid range in the presence of different metal ions making this sensor a proper one for pH determinations in leaching solutions of the recyclable processes of valuable metals.     

Novel sulfate ion-selective polymeric membrane electrode based on a derivative of pyrilium perchlorate

A sulfate ion-selective PVC membrane sensor based on 4-(4-bromophenyl)-2,6-diphenylpyrilium perchlorate (BDPP) as a novel sensing material is successfully developed. The electrode shows a good selectivity for sulfate ion with respect to common organic and inorganic anions. The sensor exhibits a good linear response with slope of -28.9+/-0.5 mV per decade over the concentration range of 1.0x10(-6)-1.0x10(-2) M, and a detection limit of 8.0x10(-7) M of SO(4)(2-) ions. The electrode response is independent of pH in the range of 4.0-9.0. The proposed sensor was applied as an indicator electrode in potentiometric titration of sulfate and barium ions, and to the determination of zinc in zinc sulfate tablets.     

DPA-substituted coumarins as chemosensors for zinc(II): modulation of the chemosensory characteristics by variation of the position of the chelate on the coumarin

The sensory capabilities of two novel di(2-picolyl)amine (DPA)-substituted coumarins are described and it is shown that the variation of the point of attachment of the DPA group to the coumarin framework controls their sensing behavior: the 4-substituted system is a CHEF-type sensor that shows a significant increase in fluorescence intensity upon Zn(2+) binding, whereas the 3-substituted system is a ratiometric sensor.     

Naphthalimide as Highly Selective Fluorescent Sensor for Ag^＋ Ions

The naphthalimide derivative. NA1 was synthesized, which consists of a bis（2-（ethylthio）ethyl）amine group binding cations and naphthalimide unit as chromogenic and fluorogenic signaling subunit. Absorption and emission spectra and the effect of polarity of solvents and pH values were studied. The photo-induced electron transfer （PET） occurred from the donor of bis（2-（ethylthio）ethyl）amine group to the naphthalimide fluorophore. The present study demonstrates that NA1 is a viable candidate as a fluorescent receptor for a new Ag^＋ ion sensor. This silver ion chemosensor can discriminate Ag^＋ ion well among heavy metal ions by an enhancement of the fluorescence intensity in ethanol-water （1 ： 9, V ： V）. And NA1 is also a pH-sensor because the fluorescence of the compound varies with the pH values.     

2-Amino-4-(4-aminophenyl)thiazole application as an ionophore in the construction of a Lu(III) selective membrane sensor

A derivative of thiazole（AAT） has been explored as a sensing material for preparation a selective Lu（III） PVC-based membrane sensor.The proposed sensor exhibits a Nernstian response over a wide concentration range from 1.0×10^-6 to 1.0×10^-1 mol/L of Lu（Ⅲ） and the detection limit is 5.7×10^-7 mol/L.The sensor response is independent of pH of the solution in the range 3.2-8.8 and possesses the advantages of fast response time（～6） and in particular,good selectivity to the lutetium ions with regard to most common metal ions,and especially all lanthanide ions.     

Novel mercury (II) ion-selective polymeric membrane sensor based on ethyl-2-benzoyl-2-phenylcarbamoyl acetate

Mercury (II) ion-selective PVC membrane sensor based on ethyl-2-benzoyl-2-phenylcarbamoyl acetate (EBPCA) as a novel nitrogen containing sensing material is successfully developed. The sensor exhibits good linear response of 30 mV per decade within the concentration range 10(-6)-10(-3) mol l(-1) Hg(II). The sensor shows good selectivity for mercury (II) ion in comparison with alkali, alkaline earth, transition and heavy metal ions. The EBPCA-based sensor is suitable for use with aqueous solutions of pH 2.0-4.5 and exhibits minimal interference by Ag(I) and Fe(III), which are known to interfere with other previously suggested sensors. The nature and composition of the sensing material and its mercury complex are examined using Fourier-transform infrared analysis, elemental analysis and X-ray fluorescence techniques. The proposed sensor is applied as a sensor for the determination of Hg(II) content in some amalgam alloys. The results show good correlation with data obtained by atomic absorption spectrometric method.     

Fabrication of an optical sensor based on the immobilization of Qsal on the plasticized PVC membrane for the determination of copper(II)

A novel optical sensor has been proposed for sensitive determination of Cu(II) ion in aqueous solutions. The copper sensing membrane was prepared by incorporating Qsal (2-(2-hydroxyphenyl)-3H-anthra[2,1-d]imidazole-6,11-dione) as ionophore in the plasticized PVC membrane containing tributyl phosphate (TBP) as plasticizer. The membrane responds to Cu(II) ion by changing color reversibly from yellow to dark red in acetate buffer solution at pH 4.0. The proposed sensor displays a linear range of 6.3 × 10^?7?1.00 × 10^?4 M with a limit of detection of 3.3 × 10^?7 M. The response time of the optical sensor was about 3?C5 min, depending on the concentration of Cu(II) ions. The selectivity of the optical sensor to Cu(II) ions in acetate buffer is good. The sensor can readily be regenerated by hydrochloric acid (0.1 M). The optical sensor is fully reversible. The proposed optical sensor was applied to the determination of Cu(II) in environmental water samples.     

响应范围可调的pH荧光传感器的构建及其性能研究

合成并表征了化合物N,N'-二谷氨酸铵盐-3,4,9,10-苝四羧酸二酰亚胺(PTCDG).此化合物水溶性好,荧光量子产率高.基于此,设计了一组新颖的响应范围可调的pH荧光传感器.PTCDG与顺磁性的Fe3+可按1∶1络合,络合常数为6.5×105,考察了其它金属离子的影响,表明PTCDG对Fe3+有良好的选择性.PTCDG与Fe3+结合后,由于PET效应,荧光猝灭,伴随pH值增大,Fe3+与OH-形成Fe(OH)3,从体系中沉淀出来,荧光团被释放,从而荧光恢复.在不同的Fe3+的良好配体存在条件下,形成Fe(OH)3的pH范围向碱性方向移动.PTCDG,PTCDG/Fe3+,PTCDG/Fe3+/三乙胺,PTCDG/Fe3+/吡啶、PTCDG/Fe3+/邻菲罗啉的响应范围分别为4.0～6.0,5.0～10,5.0～7.0,6.0～8.0和7.0～9.0,涵盖了pH值4.0～10的区间,实现了响应范围的可调.考察了内在的干扰物对该传感器的效能的影响,探讨了此体系的荧光传感机理.此传感器具有很多优异的性能,响应的范围可调且近中性,荧光和颜色变化明显,响应快,具有较高的灵敏性.     

Novel PVC-based copper(II) membrane sensor based on 2-(1'-(4'-(1'-hydroxy-2'-naphthyl)methyleneamino)butyl iminomethyl)-1-naphthol.

A copper(II) ion-selective PVC membrane sensor based on 2-(1'-(4'-(1'-hydroxy-2'-naphthyl)methyleneamino)butyl iminomethyl)-1-naphthol (BHNB) as a novel Schiff base containing a sensing material has been successfully developed. The sensor exhibits a good linear response of 29 mV per decade within the concentration range of 10(-1)-10(-6) M of Cu2+. The sensor shows good selectivity for copper(II) ion in comparison with alkali, alkaline earth, transition and heavy metal ions. The BHNB-based sensor is suitable for use with aqueous solutions of pH 3.5-7.0 and displays minimal interference by Sr(II), Cd(II), Hg(II), Zn(II) and Pb(II), which are known to interfere with other previously suggested electrodes. The proposed membrane electrode was used as a sensor for determining the Cu(II) content in black tea samples. It was also applied as an indicator electrode in the potentiometric titration of Cu2+ ions with EDTA.     

A fluorescent anion sensor that works in neutral aqueous solution for bioanalytical application

Anion recognition and anion sensing are of interest because anions play many important roles in living organisms. Most currently known anion sensors work only in organic solution, but sensors for biological applications are required to function in neutral aqueous solution. We have designed and synthesized a novel fluorescent sensor for anions. The sensor molecule 1-Cd(II) contains 7-amino-4-trifluoromethylcoumarin as a fluorescent reporter and Cd(II)-cyclen (1,4,7,10-tetraazacyclododecane) as an anion host. In neutral aqueous solution, Cd(II) of 1-Cd(II) is coordinated by the four nitrogen atoms of cyclen and the aromatic amino group of coumarin. When various anions are added to 100 mM HEPES buffer solution (pH 7.4) containing 1-Cd(II), the aromatic amino group of coumarin is displaced from Cd(II), causing a change of the excitation spectrum. While pyrophosphate and citrate were detected with high sensitivity, fluoride and perchlorate produced no response. Among organic anions, ATP and ADP gave strong signals, while cAMP showed little signal. By utilizing the different affinities of the sensor for AMP and cAMP, the activity of phosphodiesterase, which cleaves cyclic nucleotide, was monitored in real-time. The sensor should have many biochemical and analytical applications and the sensing principle should be widely applicable to the sensing of other molecules.     

A test strip for chloride analysis in environmental water

A disposable and reversible test strip for chloride is proposed. It is based on a polyester strip containing a circular sensing zone, 6 mm in diameter and 9.5 microm in thickness, with all the reagents necessary to produce a selective response to chloride. This sensing zone comprises a plasticized poly(vinyl chloride) (PVC) membrane that incorporates trioctyltin chloride as ionophore and 4',5'-dibromofluorescein octadecyl ester as chromoionophore. The prepared test strip works on a co-extraction system of chloride and hydrogen ions in the sensing zone. This disposable test strip can determine chloride simply by introducing the strip into a water sample containing a pH 2.0 buffer and measuring the absorbance at 534 nm as the analytical signal because the colour changes from red to orange. Experimental variables that influence the sensor response have been studied, especially those related to selectivity and response time. The sensor responds linearly in activities in the range 0.15-24.7 mM. The detection limit is 0.15 mM, the intermembrane reproducibility at a mid-level of the range is 6.4% relative standard deviation (RSD) of log aCl- and the intramembrane reproducibility is 4.5%. The procedure was applied to the determination of chloride in different types of water (tap, well, stream and sea), validating results against a reference procedure. This proposed test system for chloride determination in waters is inexpensive, selective and sensitive and uses only conventional instrumentation.     

Coumarin Based Neutral Sensor for Biologically Important Anions

A coumarin Shiff-base derivative, salicylaldehyde-N-(6-phenylazo-coumarin-3-formyl)-hydrazone(1), was obtained by simple organic synthesis from cheap and commercially available starting materials. Sensor 1 exhibits a very weak fluorescence emission, however, in the presence of acetate ions “turn-on” fluorescence is observed, which results from binding-induced conformational restriction of the fluorophore. Importantly, sensor 1 can also be used as colorimetric chemosensor for the anions with strong basicity, which is easily observed from yellow to red by naked eyes. Consequently, compound 1 can behave as a colorimetric and fluorescence sensor for biologically important F–, CH3COO– and H2PO4– in the presence of the other anions tested such as Cl–, Br– and I– in dimethyl sulfoxide(DMSO).     

Ion-induced FRET on-off in fluorescent calix[4]arene

A novel calix[4]arene bearing one 2,3-naphthocrown-6 and two coumarin amide units at the lower rim in partial-cone conformation was synthesized as a colorimetric and FRET-based fluorometric sensor for F(-) and Cs(+) ions. Intramolecular FRET from the naphthalene emission to the coumarin absorption affords high fluorescence selectivity toward F(-) and Cs(+) ions.     

Synthesis of N'-(1-pyridin-2-ylmethylene)-2-furohydrazide and its application in construction of a highly selective PVC-based membrane sensor for La(III) ions.

A highly La(III) ion-selective PVC membrane sensor based on N'-(1-pyridin-2-ylmethylene)-2-furohydrazide (NPYFH) as an excellent sensing material was successfully developed. The electrode shows a good selectivity for La(III) ion with respect to most common cations including alkali, alkaline earth, transition and heavy metal ions. The proposed sensor exhibits a wide linear response with slope of 19.2 +/- 0.6 mV per decade over the concentration range of 1.0 x 10(-6) - 1.0 x 10(-1) M, and a detection limit of 7.0 x 10(-7) M of La(III) ions. The sensor response is independent of pH in the range of 3.5-10.0. The proposed electrode was applied as an indicator electrode in potentiometric titration of La(III) ion with EDTA.     

A Novel Sulfate Polymeric Membrane Sensor Based on a New Bis‐Pyrylium Derivative

A novel ion‐selective polymeric membrane sensor based on pyrylium‐4,4‐(1,4‐phenylen) bis[2,6‐bis(2‐naphthyl)]‐bis[tetrafluoroborate] (PBGNB) as an excellent sensing material is successfully developed. The electrode possesses the advantages of a very low detection limit (5.0×10^?8 M), a wide working concentration range (1.0×10^?8?1.0×10^?1 M) and specially, a high sulfate selectivity over most common organic and inorganic anions. The sensor displays Nernstian behavior (slope of 29.5±0.5 mV per decade) in a wide pH range (3.0–8.5). It shows a short response time in the whole concentration range (ca. 10 s). The electrode was used as an indicator electrode in the potentiometric titration of sulfate ions with barium ions. The proposed sensor was successfully applied to the direct determination of salbutamol sulfate and paromomycin sulfate.