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Antioxidants are important to protect and maintain biological barriers, such as the skin. Antioxidant effects are often assessed using clinical trials, however these tests are costly and time consuming. In this work we introduce a skin membrane-covered oxygen electrode (SCOE) as an in vitro tool for monitoring H 2 O 2 and antioxidant reactions in skin. The SCOE gives amperometric response to H 2 O 2 concentrations down to 0.05 mM. More importantly, the electrode allows measurements of polyphenol penetration and reaction with H 2 O 2 in skin. Measurements with SCOE show that lipophilic polyphenols such as quercetin, piceatannol, resveratrol, and plant extract from Plantago major impose their antioxidant effect in skin within 2-20 min. Rutin is however too hydrophilic to penetrate into stratum corneum and therefore cannot deliver its antioxidant effect during similar time interval. The measurements are interpreted considering polyphenol partition-penetration through stratum corneum and the reaction with the H 2 O 2 -catalase system in the skin. The contribution of other enzymes will be addressed in the future., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Massive integration of biosensors into design of Internet-of-Things (IoT) is vital for progress of healthcare. However, the integration of biosensors is challenging due to limited availability of battery-less biosensor designs. In this work, a combination of nanomaterials for wireless sensing of biological redox reactions is described. The design exploits silver nanoparticles (AgNPs) as part of the RFID tag antenna. We demonstrate that a redox enzyme, particularly, horseradish peroxidase (HRP), can convert AgNPs into AgCl in the presence of its substrate, hydrogen peroxide. This strongly changes the impedance of the tag. The presented example exploits gold nanoparticle (AuNP)-assisted electron transfer (ET) between AgNPs and HRP. We show that AuNP is a vital intermediate for establishing rapid ET between the enzyme and AgNPs. As an example, battery-less biosensor-RFID tag designs for H 2 O 2 and glucose are demonstrated. Similar battery-less sensors can be constructed to sense redox reactions catalysed by other oxidoreductase enzymes, their combinations, bacteria or other biological and even non-biological catalysts. In this work, a fast and general route for converting a high number of redox reaction based sensors into battery-less sensor-RFID tags is described.

A highly selective and sensitive fluorescent sensor for the determination of fructose is developed. The fluorescent sensor was prepared by incorporating a new naphthalimide dye with a planar structure as a selectophore and graphene oxide (GO) nanoplatelets as a quencher for rapid optical detection of fructose. The designed probe, made with the high fusion loop-containing dye, along with the GO nanoplatelets, detected fructose over the other monosaccharides very well. The proposed sensor displays a linear response range of 7 × 10 -5 to 3 × 10 -2 M with a low limit of detection of 23 × 10 -6 M in solution at pH 7.4. This sensor shows a good selectivity towards fructose with respect to other saccharides. The proposed sensor was then applied to the determination of fructose in human plasma with satisfactory results., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In this study, CdTe QDs were prepared in aqueous medium and then capped with a synthetic heterocycle ligand (CdTe/L QDs) via surface modification method. Characterization of synthesized CdTe/L QDs was carried out through various analytical techniques including fluorescence spectroscopy, transmission electron microscopy (TEM), UV-Vis spectrophotometry, thermo-gravimetric (TG) analysis and Fourier transform infrared (FTIR). The fluorescence intensity of the CdTe/L QDs at 520 nm (excitation at 380 nm) was selectively quenched in the presence of trace amounts of silver ions. CdTe/L QDs were utilized as an ultrasensitive and selective fluorescent sensor for determination of trace concentrations of silver ions with a detection limit of 6.12 ± 0.11 × 10 -10  mol L -1 and a linear range of 2.04 ± 0.10 × 10 -9  mol L -1 -3.63 ± 0.12 × 10 -7  mol L -1 . The fabricated optical sensor was also used for the measurement of silver ions in real water samples which yielded satisfactory analytical results. These results were also evaluated with inductively coupled plasma emission spectroscopy (ICP-OES). This study shows that CdTe/L QDs could have potential applications in selective and sensitive analysis of different water samples for detection of silver ions., (Copyright © 2018. Published by Elsevier B.V.)

A sensitive fluorescent chemical nanosensor for the detection of entacapone (EN) in pharmaceutical samples is introduced. EN is a nitrocatechol drug that functions as a selective and reversible inhibitor of catechol-O-methyl transferase and is widely prescribed in the treatment of Parkinson disease. Molecularly imprinting technology and graphene oxide quantum dots (GOQDs) were employed in designing the EN fluorescent nanosensor. GOQDs were embedded into an inorganic polymer while the imprinting process occurred. The synthesized GOQDs-embedded silica molecularly imprinting polymer (SMIP) showed strong fluorescent emission at 450 nm by exciting at 360 nm. The fluorescence intensity of GOQDs-embedded SMIP was quenched effectively by adsorption of EN as a template molecule. The quenching corresponded to EN concentration in a linear range of at least 0.40-6.00 μM with a limit of detection of 0.31 μM. The designed chemical nanosensor was successfully applied to the analysis of entacapone in some pharmaceutical tablets also containing carbidopa and levodopa (RSD 3.8%).

A luminescence nanosensor has been developed for analysis of Ornidazole in biological samples using graphene-quantum-dot-embedded silica molecular imprinted polymer (GQD-SMIP) as a selective probe for this analyte. The GQD-SMIP was found to possess a strong fluorescent emission at 450 nm upon excitation at 365 nm. This emission was found to linearly quench in the presence of Ornidazole in a concentration range of 0.75 to 30 μM. A detection limit of 0.24 μM was reached using the probe and the sensor was successfully used in the determination of the analyte in plasma samples., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This review (with 131 references) summarizes the progress made in the past years in the field of nanomaterial based sensing of serotonin (5-HT). An introduction summarizes the significant role of 5-HT as a biomarker for several major diseases, methods for its determination and the various kinds of nanomaterials for use in electrochemical sensing process relies principally on a precise choice of electrodes. The next main section covers nanomaterial based methods for sensing 5-HT, with subsections on electrodes modified with carbon nanotubes, graphene related materials, gold nanomaterials, and by other nanomaterials. A concluding section discusses future perspectives and current challenges of 5-HT determination. Graphical abstract Conceptual design of electrochemical sensing process of the biomarker serotonin by using nanomaterials and the role of 5-HTas biomarker in the body from preclinical to clincal.

Cytochrome c (Cyt c), a heme protein, can be a potential biomarker for cell-apoptosis or even cancer diagnosis. In this work, a simple, rapid, sensitive and selective label-free assay for Cytochrome c (Cyt c) detection is introduced based on an interaction between nucleic acid aptamer biomolecules and surfaces of Carbon Dots (CDs). CDs are used as a fluorescent probes and Cyt c-aptamers as a sensing materials. Interactions of aptamers with CDs quench the fluorescent intensity of CDs. By addition of Cyt c biomolecule as an analyte to the solution and binding to the aptamers, CDs fluorescence turns on. Stronger binding affinity of the aptamers toward Cyt c than CDs, causes they leave the CDs surfaces and the fluorescence is recovered. The amount of recoveries corresponds linearly to the concentration of Cyt c and be used as the basis of detection. The method exhibited high sensitivity to Cyt c with a detection limit of 25.90 nM and a linear range from 40 nM to 240 nM.

In this study, a sensitive fluorescent DNA nanobiosensor has been developed to determine DNA sequence of a well-known tumor suppressor gene, Adenomatous Polyposis Coli (APC). The design of the nanobiosensor was carried out using a synthetic organic ligand as a new fluorophore. The response mechanism of the nanobiosensor was based on DNA hybridization. The new fluorophore was assembled on gold nanoparticles (Au NPs) to enhance the sensitivity of the nanobiosensor response. The fabricated DNA nanobiosensor showed a fluorescence emission at 477 nm by exciting wavelength of 360 nm. By addition of the ssDNA target, the fluorescent emission of the nanobiosensor enhanced linearly in the range from 3.3 × 10 -10 to 1.1 × 10 -9 mol L -1 with detection limit of 1.3 × 10 -11 mol L -1 . The proposed DNA nanobiosensor responded selectively to its complementary strand in comparison with non-complementary and three mismatched bases. The nanobiosensor had also a fast response time with acceptable repeatability. Finally, the performance of the DNA nanobiosensor in biological fluid, serum plasma, was investigated and a satisfactory results were obtained., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this work, a rapid, selective naked eyes colorimetric chemical probe for the detection of Cr 3+ was developed based on functionalization of gold nanoparticles. For this purpose, surface of Au NPs was functionalized using 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol (AMTT). Through colorimetric studies, it was found that in the presence of Cr 3+ ions, AMTT-Au NPs instantly aggregated and resulted in a color change of the solution from red to blue. The color change of AMTT-Au NPs due to the aggregation induced by Cr 3+ can be seen with even naked eyes and also by UV-Vis spectroscopy with a detection limit of 1.8μM and 0.1μM, respectively. AMTT-Au NPs showed excellent selectivity toward Cr 3+ compared to other cations tested, including K + , Na + , Cs + , Fe 3+ , Ni 2+ , Cu 2+ , Co 2+ , Zn 2+ , Ba 2+ , Ca 2+ , Mg 2+ , Cd 2+ , Pb 2+ , Hg 2+ ions and especially all trivalent lanthanide ions. The absorbance ratio (A 650 /A 525 ) was linear toward Cr 3+ concentrations in the range of 0.6-6.1μM (R 2 =0.996). The best response was achieved over a pH range of 3-5. Furthermore, the proposed colorimetric method based on AMTT-Au NPs was successfully used for Cr 3+ ion detection in plasma sample and some water samples., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A computational study at the density functional theory (DFT) as well as electrochemical methods, was carried out on the structural and physico-chemical properties of a series of sulfonamide derivatives (SAs) as WHO essential medications in the treatment of basic health system. The B3LYP/6-311++G(d,p) level of theory carried out on sulfadiazine (SDZ), sulfathiazole (STZ), sulfaquinoxaline (SQX), sulfacetamide (SAA), and the reference unsubstituted sulfonamide (SA) was discussed and rationalized in term of the N1-sulfonamide substituent. The geometric structures and the electronic properties related to the bacteriostatic reactivity were revealed to be affected by the steric and "push-pull" characteristics of the substituents. Electrochemical experiments on oxidation of SAs, using cyclic voltammetry are presented. The results obtained showed that the calculated ionization potentials (IPs) could be correlated linearly with the electro-oxidation potentials. From the molecules studied it is evident that SDZ act as the most electro-active agent, possessing the highest biological activity. DFT computations carried out using the standard molar enthalpies of formation in the gas phase predicted improvements in the thermodynamic stabilization of the SDZ, SQX, and SAA molecules and an unstabilization of STZ with respect to the parent molecule SA.

In this work, as a novel fluorescent nano-sensor, a ligand-capped CdTe QDs (CdTe-L QDs) was designed for the detection and quantification of Cu 2+ ions in environmental water samples. The synthesized QDs were characterized by transmission electron microscopy (TEM), thermo-gravimetric (TG) analysis, Fourier transform infrared (FTIR), UV-Vis spectrophotometry and fluorescence spectroscopy. Optical properties of the produced nanosensor were monitored by UV-Vis and fluorescence spectrophotometry. It was observed that fluorescence intensity of the produced nano-sensor selectively quenched by adding Cu 2+ ions in comparison to other metal ions tested. Using CdTe-L QDs, a rapid and facile analytical method was developed to determine Cu 2+ ions in the concentration range of 5.16 ± 0.07 × 10 - 8 mol L - 1 -1.50 ± 0.03 × 10 - 5 mol L - 1 with a detection limit of 1.55 ± 0.05 × 10 - 8 mol L - 1 . The nanosensor was successfully applied for the determination of Cu 2+ ions in various water samples, and the results were compared with the standard method. Graphical Abstract.

A novel optical nanosensor for detection of Metronidazole in biological samples was reported. Graphene quantum dots embedded silica molecular imprinted polymer (GQDs-embedded SMIP) was synthesized and used as a selective fluorescent probe for Metronidazole detection. The new synthesized GQDs-embedded SMIP showed strong fluorescent emission at 450nm excited at 365nm which quenched in presence of Metronidazole as a template molecule.. The quenching was proportional to the concentration of Metronidazole in a linear range of at least 0.2μM to 15μM. The limit of detection for metronidazole determination was obtained 0.15μM. The nanosensor successfully worked in plasma matrixes., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A highly ordered mesoporous silica material functionalized with isatin (SBA-Pr-IS) was designed and synthesized. Characterization techniques including XRD, TGA, BET, SEM, and FT-IR were employed to characterize the pore structure, textural properties, microscopic morphology, and molecular composition of grafted organic moieties of SBA-Pr-IS. The successful attachment of the organic moiety (0.34 mmol g -1 ) without the SBA-15 structure collapsing after the modification steps was confirmed. Fluorescence characterization of SBA-Pr-IS was examined upon addition of a wide variety of cations in aqueous medium and it showed high sensitivity toward Hg 2+ ions. During testing in an ion competition experiment, it was observed that the fluorescence changes of the probe were remarkably specific for Hg 2+ ions. Furthermore, a good linearity between the fluorescence intensity of this material and the concentration of Hg 2+ ions was constructed with a suitable detection limit of 3.7 × 10 -6  M. Finally, the applicability of the proposed method was successfully evaluated for the determination of Hg 2+ ions in real samples. Therefore, SBA-Pr-IS can be used as an efficient fluorescence probe for Hg 2+ ions. Graphical Abstract A novel organic-inorganic hybrid material was designed and synthesized by functionalization of SBA-15 mesoporous silica material with isatin. The evaluation of the sensing ability of SBA-Pr-IS using fluorescence spectroscopy revealed that the SBA-Pr-IS was a selective fluorescent probe for Hg 2+ ion in water in the presence of a wide range of metal cations.

In this work, graphene quantum dots (GQDs) was synthesized through hydrothermal method and used as a photoluminescent bulk nano-chemosensor for detection of Ce 3+ ion in the aqueous solution. The synthesized GQD was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Visible absorption and fluorescence emission spectroscopy. The sheet diameters of the synthesized GQDs were mainly distributed in the range of 15-20 nm. The interactions of GQDs with common cations and lanthanide ions were studied by fluorescence spectroscopy. Among the tested cations, Ce 3+ ions was able to quench the fluorescence emission intensity of the GQD selectively. This quenching can be attributed to a redox mechanism between Ce 3+ ion on the GQDs surface.

A novel ultrasensitive sensing system for the rapid detection of cytochrome c (Cyt C) was developed on the basis of an electrochemiluminescence (ECL) method. A nanocomposite biosensor was made of reduced graphene oxide decorated with cerium oxide/tris(2,2-bipyridyl)ruthenium(II)/chitosan (CeO2NPs-RGO/ Ru(bpy)3 (2+)/CHIT) and used for this purpose. The ECL signal was produced by an electrochemical interaction between Ru(bpy)3 (2+) and tripropyl amine (TPA) on the surface of the electrode. Addition of Cyt C to the solution decreases the ECL signal due to its affinity for TPA and inhibition of its reaction with Ru(bpy)3 (2+). The effects of the amount of CeO2NPs-RGO, Ru(bpy)3 (2+), TPA concentration as a co-reactant, and the pH of the electrolyte solution on the ECL signal intensity were studied and optimized. The results showed that the method was fast, reproducible, sensitive, and stable for the detection of Cyt C. The method has a linear range from 2.5 nM to 2 μM (R (2) = 0.995) with a detection limit of 0.7 nM. Finally, the proposed biosensor was used for the determination of Cyt C in human serum samples with RSDs of 1.8-3.6 %. The results demonstrate that this solid-state ECL quenching biosensor has high sensitivity, selectivity, and good stability. Graphical Abstract A novel solid-state electrochemiluminescence sensor for detection of cytochrome C based on Ceria Nanoparticles Decorated Reduced Graphene Oxide Nanocomposite.

Citrus Tristeza virus (CTV) is one of the most destructive pathogens worldwide that exist as a mixture of malicious (Sever) and tolerable (Mild) strains. Mild strains of CTV can be used to immunize healthy plants from more Severe strains damage. Recently, innovative methods based on the fluorescent properties of DNA/silver nanoclusters have been developed for molecular detection purposes. In this study, a simple procedure was followed to create more active DNA/AgNCs probe for accurate and selective detection of Tristeza Mild-RNA. To this end, four distinct DNA emitter scaffolds (C12, Red, Green, Yellow) were tethered to the Mild capture sequence and investigated in various buffers in order to find highly emissive combinations. Then, to achieve specific and reliable results, several chemical additives, including organic solvents, PEG and organo-soluble salts were used to enhance control fluorescence signals and optimize the hybridization solution. The data showed that, under adjusted conditions, the target sensitivity is enhanced by a factor of five and the high discrimination between Mild and Severe RNAs were obtained. The emission ratio of the DNA/AgNCs was dropped in the presence of target RNAs and I0/I intensity linearly ranged from 1.5 × 10(-8) M to 1.8 × 10(-6) M with the detection limit of 4.3 × 10(-9) M.

A simple and sensitive method for the detection of DNA hybridization in a homogeneous format was developed, using bis(8-hydroxyquinoline-5-solphonate)cerium(III) chloride (Ce(QS)2Cl) as a novel fluorescent probe. The method is based on fluorescence quenching by gold nanoparticles used as both nanoscafolds for the immobilization of the probe DNA sequence, which is related to Alicyclobacillus acidophilus strain TA-67 16S ribosomal RNA, and nanoquenchers of the Ce(QS)2Cl probe. The probe DNA-functionalized GNPs were synthesized by derivatizing the colloidal gold nanoparticles solution with 3-thiolated 16-base oligonucleotides. Addition of sequence-specific target DNAs (16 bases) into the mixture containing probe DNA-functionalized GNPs and fluorescent probe lead to the quenching of Ce(QS)2Cl fluorescence at 360 nm (λex=270 nm), due to DNA hybridization, the resulting quenched intensity being proportional to the concentration of target DNA. Under optimal conditions of pH 7.4 and Ce(QS)2Cl concentration of 1.0 × 10(-7) M, the linear dynamic range found to be 1.0 × 10(-10)-3.0 × 10(-8) M DNA, with a limit of detection of 7.0 × 10(-11) M. The interaction mechanism for the binding of Ce(QS)2Cl to DNA was studied in detail, and results proved that the interaction mode between Ce(QS)2Cl and DNA is groove binding, with a binding constant of 1.0 × 10(5) M(-1)., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A new strategy was introduced for ssDNA immobilization on a modified glassy carbon electrode. The electrode surface was modified using polyaniline and chemically reduced graphene oxide decorated cerium oxide nanoparticles (CeO2NPs-RGO). A single-stranded DNA (ssDNA) probe was immobilized on the modified electrode surface. Fast Fourier transform square wave voltammetry (FFT-SWV) was applied as detection technique and [Ru(bpy)3](2+/3+) redox signal was used as electrochemical marker. The hybridization of ssDNA with its complementary target caused a dramatic decrease in [Ru(bpy)3](2+/3+) FFT-SW signal. The proposed electrochemical biosensor was able to detect Aeromonas hydrophila DNA oligonucleotide sequence encoding aerolysin protein. Under optimal conditions, the biosensor showed excellent selectivity toward complementary sequence in comparison with noncomplementary and two-base mismatch sequences. The dynamic linear range of this electrochemical DNA biosensor for detecting 20-mer oligonucleotide sequence of A. hydrophila was from 1 × 10(-15) to 1 × 10(-8) mol L(-1). The proposed biosensor was successfully applied for the detection of DNA extracted from A. hydrophila in fish pond water up to 0.01 μg mL(-1) with RSD of 5%. Besides, molecular docking was applied to consider the [Ru(bpy)3](2+/3+) interaction with ssDNA before and after hybridization., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Using the concept of electrogenerated chemiluminescence (ECL), a sensitive analytical method for the determination of carbidopa is described. Electro-oxidation of carbidopa on the surface of a graphene oxide (GO)-modified gold electrode (GE) leads to enhancement of the weak emission of oxidized luminol. Under optimum experimental conditions, the ECL signal increases linearly with increasing carbidopa concentrations over a range of 1.0 × 10(-9) -1.7 × 10(-7)  M, with a detection limit of 7.4 × 10(-10)  M. The proposed ECL method was successfully used for the determination of carbidopa in urine samples., (Copyright © 2014 John Wiley & Sons, Ltd.)

In this work, a ligand capped CdS QDs was synthesized, characterized and its fluorescence behavior was studied. The surface of the CdS QDs was modified using N-(3-methyl-2-(thiophene-2-carboxamido) phenyl) thiophene-2-carboxamide. The immobilized ligand on the surface of the CdS QDs can interact by cationic species due to the existence of donating atoms in its structures. Thus, effect of some metal cations on the fluorescent intensity of the ligand capped CdS QDs were studied. It was found that fluorescence intensity of the modified CdS QDs quenched selectively by addition of Co(II) ion in comparison with other cations tested. The ligand capped CdS QDs can be used as a fluorescent bulk chemosensor for detection of Co(II) ions. The fluorescent quenching is linear in the range of 1.0 × 10(-5) to 1.5 × 10(-4) mol L(-1) of Co(II) ions. The limit of detection was obtained 8.3 × 10(-7) mol L(-1). The nanosensor exhibits high selectivity toward Co(II) ions in comparison with common metal ions.

The potential benefits of decorated graphene are of great interest as they may lead to technological advancements in fabricating electro-chemical devices for catalysis, sensing and energy storage. In this study, we have developed a self-assembly approach to anchor CeO 2 nanoparticles on reduced graphene oxide (RGO) through a facile, efficient sonochemical method. We characterized the CeO 2 -RGO nanocomposites using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy and field-emission scanning electron microscopy (FE-SEM). The results reveal that CeO 2 nanoparticles with a uniform size distribution are anchored on RGO. Furthermore, we investigated the electrochemical properties of CeO 2 -RGO nanocomposites for different probes by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. We found that a suitable loading content of CeO 2 on RGO can induce a synergistic effect for optimizing the electro-catalytic activity of the nanocomposites. Our findings will have a profound effect on the use of CeO 2 -RGO nanocomposites in electrochemical devices.

The purpose of this work was to investigate the performance of electrodes synthesized with Polyacrylonitrile-based carbon nanofibers (PAN-based CNFs). The homogenous PAN solutions with different concentrations were prepared and electrospun to acquire PAN nanofibers and then CNFs were fabricated by heat treatment. The effective parameters for the production of electrospun CNF electrode were investigated. Scanning electron microscopy (SEM) was used to characterize electrospun nanofibers. Cyclic voltammetry was applied to investigate the changes of behavior of electrospun CNF electrodes with different diameters. The structure of CNFs was also evaluated via X-ray diffraction (XRD) and Raman spectroscopy. The results exhibited that diameter of nanofibers reduced with decreasing polymer concentration and applied voltage and increasing tip-to-collector distance, while feeding rate did not have significant effect on nanofiber diameter. The investigations of electrochemical behavior also demonstrated that cyclic voltammetric response improved as diameter of CNFs electrode decreased., (Copyright © 2014 Elsevier B.V. All rights reserved.)

An electrochemical detection technique based on combination of was coulometric differential fast Fourier transformation admittance voltammetry (CDFFTAV) and nano-composite film modified glassy carbon electrode was successfully applied for sensitive determination of Amlodipine. The nano-composite film was made by a mixture of ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4), multiwall carbon nanotube and Au nanoparticles as electrochemical mediators. Studies reveal that the irreversible oxidation of Amlodipine was highly facile on the electrode surface. The electrochemical response was established on calculation of the charge under the admittance peak, which was obtained by discrete integration of the admittance response in a selected potential range, obtained in a flow injection analysis. Once established the best operative optimum conditions, the resulting nano-composite film electrode showed a catalytic effect on the oxidation of the analyte. The response is linear in the Amlodipine concentration range of 1.0 × 10(-9) to 2.0 × 10(-7)M with a detection limit of 1.25 × 10(-10)M. Moreover, the proposed technique exhibited high sensitivity, fast response time (less than 6s) and long-term stability and reproducibility around 96%, and it was successfully used to the determination of Amlodipine content in the pharmaceutical formulation., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The enhancing effect of histidine and tryptophan on chemiluminescence (CL) of CdSe quantum dots (QDs)-H2O2 system was studied. This reaction is based on the catalytic effect of amino acids, causing a significant increase in the light emission, as a result of the reaction of quantum dots (QDs) with hydrogen peroxide. In the optimum conditions, this method was satisfactorily described by linear calibration curve in the range of 0.66-35.5 μM and 0.83-35.1 μM for histidine and tryptophan, respectively. The effect of various parameters such as concentration of CdSe QDs, concentration of H2O2 and concentration of imidazole on the intensity of CL system were studied. The main experimental advantage of the proposed method is it's selective to two amino acids compared with other amino acids., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Based on a selective complexation of N'-(2-oxo-1,2-di(pyridin-2-yl)ethylidene)furan-2-carbohydrazide (L) with Gd(III) ions, it was used as a selectophore in construction of a Gd(III) selective PVC membrane sensor. Different compositions for the membrane were tested. The o-nitrophenyloctyl ether (NPOE) was used as suitable plasticizer, and a mixture of sodium tetraphenyl borate (NaTPB) and oleic acid (OA) as anion excluders. The proposed sensor displayed a Nernstian behavior with the slope of 19.9 ± 0.6 mV decade(-1) in concentration range of 1.0 × 10(-6) to 1.0 × 10(-2)mol L(-1). Detection limit was 4.2 × 10(-7)molL(-1) and response time was ~10s. Applicable pH range of the electrode was 4.2-8.0. Lifetime of the sensor is at least 10 weeks. Analysis of certified reference materials confirmed the accuracy of the proposed electrode., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A Methimazole sensor was designed and constructed based on nanocomposite of carbon, ionic liquid, reduced graphene oxide (RGO) and CdS nanoparticles. The sensor signal was obtained by Differential FFT continuous linear sweep voltammetry (DFFTCLSV) technique. The potential waveform contains two sections, preconcentration potential and potential ramp. In this detection technique, after subtracting the background current from noise, the electrode response was calculated, based on partial and total charge exchanges at the electrode surface. The combination of RGO and CdS nanoparticles can catalyze the electron transfer, which outcomes of the amplification of the sensor signal. The result showed that the sensor response was proportional to the concentrations of Methimazole in the range of 2.0 to 300 nM, with a detection limit of 5.5×10(-10) M. The sensor showed good reproducibility, long-term of usage stability and accuracy. The characterization of the sensor surface was studied by atomic force Microscopy and Electrochemical Impedance Spectroscopy. Moreover, the proposed sensor exhibited good accuracy, and R.S.D value of 2.82%, and the response time of less than 7 s., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: The risk of inadequate nutrition such as trace elements and vitamin deficiencies is considerable in postmenopausal women. The aim of this study was to compare trace elements (Zinc, Copper and Magnesium) concentration in nail, urine and serum among osteoporotic postmenopausal women with control group in Iran., Methods: Forty eight postmenopausal women aged 36-60 years, were recruited, consisting 30 osteoporotic patients and 18 healthy controls. Blood, nail and urine concentration of Zinc (Zn), copper (Cu) and magnesium (Mg) were determined using Inductively Coupled Plasma -Atomic Emission Spectrometry (ICP-AES) method. Their Bone Mineral Density was measured by Dual X-ray Absorption (DEXA) method., Results: The urine level of trace elements had significant difference between osteoporotic groups and controls (p < 0.001). Moreover Mg level significantly differed in serum between two groups (p < 0.04). There was no statistically significant difference in trace minerals in nail beyond groups., Conclusion: Our findings indicate that Urine Zn level could be considerable an appropriate marker for bone absorption, usage of Zn supplements in postmenopausal women may result a beneficial reduction in osteoporotic risk.

The intensity of emitted light from CdSe quantum dots (QDs)-H2O2 is described as a novel chemiluminescence (CL) reaction for determination of dysprosium. This reaction is based on the catalytic effect of Dy(3+) ions, causing a significant increase in the light emission, as a result of the reaction of quantum dots (QDs) with hydrogen peroxide. In the optimum conditions, this method was satisfactorily described by linear calibration curve in the range of 8.3×10(-7)-5.0×10(-6)M, the detection limit of 6.0×10(-8)M, and the relative standard deviation for five determinations of 2.5×10(-6)M Dy(3+) 3.2%. The main experimental advantage of the proposed method is its selective to Dy(3+) ions compared with common coexisting cations, therefore, it was successfully applied for the determination of dysprosium ions in water samples., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A novel Eu(3+)-sensitive fluorescent chemosensor is introduced. It is based on magnetic core-shell silica nanoparticle which is functionalized by Cinchonidine (CD-Fe3O4@SiO2). The nano-chemosensor was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-visible absorption and fluorescence emission. The fluorescent nano-chemosensor shows a selective interaction with Eu(3+) ion. Fluorescence studies revealed that the emission intensity of the functionalized magnetic core-shell silica nanoparticles (CD-Fe3O4@SiO2 NPs) increases significantly by addition of various concentrations of Eu(3+) ion. While in case of mono, di, and other trivalent cations, weak changes or either no changes in intensity were observed. The enhancement in fluorescence intensity of nano-chemosensor is because of the strong covalent binding of Eu(3+) ion to CD-Fe3O4@SiO2 NPs with a large binding constant value of 1.7 × 10(5) mol L(-1)., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A new Lu(3+) sensitive fluorescent chemosensor is designed using 8-hydroxyquinoline functionalized mesoporous silica with highly ordered structure (LUS-SPS-Q). The characterization of LUS-SPS-Q showed that the organized structure has been preserved after the post grafting procedure. The synthesized material showed a selective interaction with Lu(3+) ion, most probably due to the presence of the fluorophore moiety at its surface. The emission intensity of the Lu(3+)-bound mesoporous material increases with an increase in concentrations of Lu(3+) ion. Addition of other mono-, di-, trivalent ions resulted in insignificant change in the fluorescent intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Lu(3+) ion. The linear response range of Lu(3+) chemo-sensor was from 1.6×10(-7) to 1.0×10(-5) mol L(-1). The Limit of detection obtained was 8.2×10(-8) mol L(-1) and the pH range which the proposed chemo-sensor can be applied was 3.3-8.3., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A new ion-selective electrode for Sm(3+) ion is described based on the incorporation of N,N',N"-tris(4-pyridyl)trimesic amide (TPTA) in a poly(vinylchloride) (PVC) matrix. The membrane sensor comprises nitrobenzene (NB) as a plasticizer, and oleic acid (OA) as an anionic additive. The sensor with the optimized composition shows a Nernstian potential response of 19.8 ± 0.5 mV decade(-1) over a wide concentration range of 1.0 × 10(-2) and 1 × 10(-6)mol L(-1), with a lower detection limit of 4.7 × 10(-7)mol L(-1) and satisfactor applicable pH range of 3.6-9.2. Having a short response time of less than 10s and a very good selectivity towards the Sm(3+) over a wide variety of interfering cations (e.g. alkali, alkaline earth, transition and heavy metal ions) the sensor seemed to be a promising analytical tool for determination of the Sm(3+). Hence, it was used as an indicator electrode in the potentiometric titration of samarium ion with EDTA. It was also applied to the direct samarium recovery in binary mixtures., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A simple, rapid and sensitive method was developed for the selective separation and preconcentration of Ni(II) using dispersive liquid-liquid microextraction, by a yellow Schiff's base bisazanyl derivative, as a selective complexing agent. In this method, a mixture of 45 μL chloroform (extraction solvent) and 450 μL tetrahydrofuran (dispersive solvent) is rapidly injected by syringe into a 5 mL aqueous sample containing 3% (w/v) sodium chloride and an appropriate amount of the Schiff's base. As a result, a cloudy solution is formed by entire dispersion of the extraction solvent into the aqueous phase. After centrifuging for 5 min at 5000 rpm, the sedimented phase is directly injected into the electrothermal atomic absorption spectrometry for Ni(II) determination. Some important parameters, such as kind and volume of extraction and dispersive solvents, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor for the presented method is 138. The calibration curve was linear over a nickel concentration range of 10-50 ng mL(-1). The detection limit and relative standard deviation were 0.04 ng mL(-1) and 2.1%, respectively. The method was successfully applied to the extraction and determination of Ni(II) in different water samples., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A novel Dy(III) ion-selective PVC membrane sensor was made using a new synthesized organic compound, 3,4-diamino-N'-((pyridin-2-yl)methylene)benzohydrazide (L) as an excellent sensing element. The electrode showed a Nernstian slope of 19.8 ± 0.6 mV per decade in a wide concentration range of 1.0 × 10(-6)-1.0 × 10(-2) mol L(-1), a detection limit of 5.5 × 10(-7) mol L(-1), a short conditioning time, a fast response time (<10s), and high selectivity towards Dy(III) ion in contrast to other cations. The proposed sensor was successfully used as an indicator electrode in the potentiometric titration of Dy(III) ions with EDTA. The membrane sensor was also applied to the F(-) ion indirect determination of some mouth washing solutions and to the Dy(3+) determination in binary mixtures., (Copyright © 2012 Elsevier B.V. All rights reserved.)

In this research, we report a new Ho(3+)-PVC membrane electrode based on N-(4,5-dimethyl-2-(picolinamido)phenyl)picolinamide (H(2)Me(2)bpb) as a suitable ion carrier. Poly vinylchloride (PVC)-based membrane composed of H(2)Me(2)bpb with oleic acid (OA) as anionic additives, and o-nitrophenyloctyl ether (NPOE) as plasticized solvent mediator. The sensor exhibits a Nernstian slope of 20.1 ± 0.2 mV decade(-1) over the concentration range of 1.0 × 10(-6) to 1.0 × 1(-2) mol L(-1), and a detection limit of 5.0 × 10(-7) mol L(-1) of Ho(3+) ions. The potentiometric response of the sensor is independent of the solution pH in the range of 3.5-9.4. It has a very short response time, in the whole concentration range (<10s), and can be used for at least eight weeks. The proposed electrode shows a good selectivity towards Ho(3+) ions over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. To assess its analytical applicability the proposed Ho(3+) sensor was successfully applied as an indicator electrode in the titration of Ho(3+) ion solutions in certified reference materials, alloy samples and for the determination of the fluoride ion in two mouthwash preparations., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Fluorescence study of the complexation between uranyl salophen (L) and some common anions in acetonitrile-water (90:10, v/v) solution showed a tendency of L toward acetate ion (AcO-). The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and acetate ion which was utilized as the basis for the selective detection of AcO-. The association constant of the 1:1 complex formation of L-AcO- was calculated as 6.60 × 10(6) . The linear response range of the fluorescent chemosensor covers a AcO- concentration range of 1.6 × 10(-7) to 2.5 × 10(-5)  mol/L, with a detection limit of 2.5 × 10(-8)  mol/L. L showed a selective and sensitive fluorescence enhancement response toward acetate ion over I3- , NO3-, CN-, CO3 (2-), Br-, Cl-, F-, H2 PO4- and SO4 (2-) , which was attributed to the higher stability of inorganic complex between acetate and L., (Copyright © 2012 John Wiley & Sons, Ltd.)

A novel fluorescence nano-chemosensor for Cr(2)O(7)(2-) anion has been developed by assembly of fluorescent aluminum complex of 8-hydroxyquinoline (AlQ(x)) within the channels of modified SBA-15. SBA-SPS-AlQ(x) shows a fluorescence emission at 486 nm. The observed remarkable fluorescence of SBA-SPS-AlQ(x) quenches in presence of Cr(2)O(7)(2-) anion. The results showed that this fluorescent nano-material can be a useful chemo-sensor for determination of dichromate anions in aqueous solutions. The linear detecting range of fluorescent nano-chemosensor for Cr(2)O(7)(2-) anion was 0.16-2.9 μmol L(-1). The lowest limit of detection (LDL) was also found to be 0.2 ng mL(-1) in aqueous solutions. SBA-SPS-AlQ(x) showed selectively and sensitively fluorescent quenching response toward Cr(2)O(7)(2-) ion in comparison with I(3)(-), NO(3)(-), CN(-), CO(3)(2-), Br(-), Cl(-), F(-), H(2)PO(4)(-) and SO(4)(2-) ions, which was because of the higher stability of its inorganic complex with dichromate ion., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A novel fluorescence nano-chemosensor for MnO(4)(-) anion has been developed by assembly of fluorescent aluminum complex of 8-hydroxyquinoline (8-HQ) within the channels of modified SBA-15 (SBA-SPS-QAl). The ordered porous structure of SBA-15 is still retained after hybridization by chemosensor material. A remarkable fluorescent quenching of SBA-SPS-QAl was attributed to the effect of MnO(4)(-) anion. The linear detecting range of the hybrid mesoporous chemosensor is 0.16-4.6μmolL(-1) of MnO(4)(-) anion and the lowest detection limit is 0.2ngmL(-1) in the aqueous solution. SBA-SPS-QAl showed a selective and sensitive fluorescent quenching response toward MnO(4)(-) ion in comparison with N(3)(-), NO(3)(-), CN(-), HCO(3)(-), Cl(-), F(-), H(2)PO(4)(-), SO(4)(2-), Cr(2)O(7)(2-), IO(3)(-) and I(-) ions, which was because of the higher stability of its inorganic complex with permanganate anion., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A novel and simple fluorescence enhancement method is introduced for selective pyrophosphate (PPi) sensing in an aqueous solution. The method is based on a 1:1 metal complex formation between tris(8-hydroxyquinoline-5-sulphonate) thulium(III) [Tm(QS)(3)] and PPi ion. The linear response covers a concentration range of 1.6 × 10(-7) -1.0 × 10(-5)  mol/L PPi and the detection limit is 2.3 × 10(-8)  mol/L. The association constant of Tm(QS)(3) -PPi complex was calculated as 2.6 × 10(5)  mol/L. Tm(QS)(3) shows a selective and sensitive fluorescence enhancement toward PPi ion in comparison with I(3)(-), NO(3)(-), CN(-), CO(3)(2-), Br(-), Cl(-), F(-), H(2) PO(4) (-) and SO(4)(2-), which is attributed to higher stability of the inorganic complex between pyrophosphate ion and Tm(QS)(3)., (Copyright © 2011 John Wiley & Sons, Ltd.)

Bis(8-hydroxy quinoline-5-solphonate) cerium(III) chloride (Ce(QS)(2)Cl) (L) was synthesized and then used as a novel fluorescent sensor for anion recognition. Preliminarily study showed that fluorescence of L enhanced selectively in the presence of HPO(4)(2-) ion. This enhancement is attributed to a 1:1 complex formation between L and HPO(4)(2-) anion. The association constant of 1:1 complex of L-HPO(4)(2-) was calculated as 3.0×10(6). Thus, L was utilized as a basis for a selective detection of HPO(4)(2-) anion in solution. The linear response range of the proposed fluorescent chemo-sensor covers a concentration range of HPO(4)(2-) from 3.3×10(-7) to 5.0×10(-6) mol L(-1) with a detection limit of 2.5×10(-8) mol L(-1). L showed selective and sensitive fluorescence enhancement response toward HPO(4)(2-) ion in comparison with I(3)(-), NO(3)(-), CN(-), CO(3)(2-), Br(-), Cl(-), F(-), H(2)PO(4)(-) and SO(4)(2-) ions. It was probably attributed to the higher stability of the inorganic complex between HPO(4)(2-) ion and L. The method was successfully applied for analysis of phosphate ions in some fertilizers samples., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A new fluorogenic method for selective and sensitive determination of beryllium using 2,6-diphenyl-4-benzo-9-crown-3-pyrane (DBCP) was developed. The proposed fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to beryllium ions in MeOH/H(2)O (70:30, v/v) solution. The fluorescence enhancement of DBCP is attributed to a 1:1 complex formation between DBCP and Be(2+) ion, which has been utilized as the basis for selective detection of Be(2+) ion. With the optimum condition described, the fluorescence enhancement at 531 nm was linear to the concentration of beryllium in the range of 1.6×10(-8)-1.6×10(-7) M and a detection limit of 1.5×10(-9) M. The fluorescent probe exhibits high selectivity for Be(2+) ion over the other common mono, di- and trivalent cations., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)(2)Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10(-7) to 1.0 × 10(-5) mol/L of PPi and the detection limit of 2.3 × 10(-8) mol/L. The association constant of L-PPi complex was calculated 2.6 × 10(5) L/mol. L was found to show selectively and sensitively fluorescence enhancement toward PPi over than I(3)(-), NO(3)(-), CN(-), CO(3)(2-), Br(-), Cl(-), F(-), H(2)PO4(-) and SO(4)(2-), which was attributed to higher stability of inorganic complex between pyrophosphate and L., (© Springer Science+Business Media, LLC 2011)

In this work, UV-Vis. electronic spectra of 1-pyridinyl-2-methylene-benzene carbohydrazonic acid (L) have been studied. The different bands observed have been assigned to the proper electronic transitions. The solvatochromic behavior of this compound is investigated by studying their electronic spectra in organic solvents with different polarities. The longer wavelength band is assigned to an intermolecular charge transfer (CT) transition. The solvated H-bonding complexes formed between dimethylformamide and L is also investigated. ΔG, and Kf values of this complex have been determined. Effects of temperature increase and concentration changes on the longer spectroscopic wavelength band of 1-pyridinyl-2-methylene-benzenecarbohydrazonic acid were studied too.

In this work, a highly sensitive carcinoembryonic antigen fast Fourier transform admittance biosensor is introduced. The proposed biosensor is based on bilayer films of ZnO/Au nanoparticles as an immobilization matrix. These layers are prepared by self-assembly and deposition method on a gold electrode surface, respectively. Carcinoembryonic antibody (anti-CEA) was immobilized on gold nanoparticles and positively charged horseradish peroxidase (HRP) was used to block sites against nonspecific binding. The admittance biosensor was developed based on fast Fourier transform continuous square wave voltammetry, which produces a sensitive, fast (less than 20 s) and reliable response for determination of carcinoembryonic antigen. The technique was applied as a detector in a flow injection system. The admittances reduction current of the biosensor decreases linearly in two concentrations ranges of CEA from 0.1 to 70 ng/mL and from 70 to 200 ng/mL with a detection limit of 0.01 ng/mL in presence of 0.5 mM H(2)O(2) as an eluent solution.

Pioglitazone is a medicine of thiazolidinedione (TZD) class with hypoglycemic (antihyperglycemic, antidiabetic) action. Pioglitazone binding to human serum albumin (HSA) was investigated at different temperatures (290, 300 and 310 K) by fluorescence spectroscopic method. Molecular docking study was also carried out besides the experiments. Experimental results revealed that pioglitazone have an ability to quench the intrinsic fluorescence of HSA tryptophan through a static quenching procedure. The binding constant was determined using Stern-Volmer modified equation and energy transfer mechanisms of quenching were discussed. Thermodynamic parameters were also calculated according to enthalpy changes dependence on different temperatures. According to the theoretical and experimental results, hydrogen bonding was found to play a major role in the interaction of pioglitazone with HSA., (Copyright © 2010 Elsevier B.V. All rights reserved.)

For the first time a highly sensitive and selective fluorimetric optode membrane was prepared for determination of trace amounts of Tb(III) ions in phosphate rock samples. The Tb(III) sensing system was constructed by incorporating 5-(dimethylamino)-N'-(2-hydroxy-1-naphthoyl) naphthalene-1-sulfonohydrazine (L) as a neutral Tb(III)-selective fluoroionophore, in the plasticized PVC membrane containing sodium tetraphenyl borate as a liphophilic anionic additive. The response of the optode is based on the strong fluorescence quenching of L by Tb(3+) ions. At a pH value of 5.0, the optode displays a wide concentration range of 1.0 x 10(-7) to 1.0 x 10(-2)M, with a relatively fast response time of less than 45 s. In addition, to high stability and reproducibility, the sensor shows a unique selectivity towards Tb(3+) ion with respect to common cations. The optode was applied successfully to the trace determination of terbium ion in binary mixture and water samples and the determination of Tb(3+) in phosphate rock samples., (Crown Copyright 2010. Published by Elsevier B.V. All rights reserved.)

N,N'-phenylenebis(salicylideaminato) (L) has been used to detect trace amounts of zinc ion in acetonitrile-water solution by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to zinc ions in MeCN/H(2)O (1:1, v/v) solution. The fluorescence enhancement of L is attributed to the 1:1 complex formation between L and Zn(II), which has been utilized as the basis for selective detection of Zn(II). The linear response range for Zn(II) covers a concentration range of 1.6x10(-7) to 1.0x10(-5)mol/L, and the detection limit is 1.5x10(-7)mol/L. The fluorescent probe exhibits high selectivity over other common metal ions, and the proposed fluorescent sensor was applied to determine zinc in water samples and waste water., (Copyright 2009 Elsevier B.V. All rights reserved.)

A novel carbon paste ion selective electrode for determination of trace amount of lead was prepared. Multi-walled carbon nanotubes (MWCNTs) and nanosilica were used for improvement of a lead carbon paste sensor response. MWCNTs have a good conductivity which helps the transduction of the signal in carbon paste electrode. The electrode composition of 20 wt% paraffin oil, 57% graphite powder, 15% ionophore (thiram), 5% MWCNTs, and 3% nanosilica showed the stable potential response to Pb(2+) ions with the Nernstian slope of 29.8 (+/-0.2)mV decade(-1) over a wide linear concentration range of 10(-7)-10(-2)mol L(-1). The electrode has fast response time, and long term stability (more than 2 months). The proposed electrode was used to determine the concentration of lead ions in waste water and black tea samples.

Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(terthiophene)s, poly(aniline)s, poly(fluorine)s, poly(3-alkylthiophene)s, polytetrathiafulvalenes, polynapthalenes, poly(p-phenylene sulfide), poly(p-phenylenevinylene)s, poly(3,4-ethylenedioxythiophene), polyparaphenylene, polyazulene, polyparaphenylene sulfide, polycarbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs), i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article, we try to give an overview of Solid-Contact ISE (SCISE), Single-Piece ISE (SPISE), Conducting Polymer (CP)-Based, and also non-conducting polymer PVC-based ISEs for various ions which their difference is in the way of the polymer used with selective membrane. In SCISEs and SPISEs, the plasticized PVC containing the ionophore and ionic additives govern the selectivity behavior of the electrode and the conducting polymer is responsible of ion-to-electron transducer. However, in CPISEs, the conducting polymer layer is doped with a suitable ionophore which enhances the ion selectivity of the CP while its redox response has to be suppressed.

Ionophore incorporated PVC membrane sensors are well-established analyticaltools routinely used for the selective and direct measurement of a wide variety of differentions in complex biological and environmental samples. Potentiometric sensors have someoutstanding advantages including simple design and operation, wide linear dynamic range,relatively fast response and rational selectivity. The vital component of such plasticizedPVC members is the ionophore involved, defining the selectivity of the electrodes' complexformation. Molecular recognition causes the formation of many different supramolecules.Different types of supramolecules, like calixarenes, cyclodextrins and podands, have beenused as a sensing material in the construction of ion selective sensors. Schiff's bases andcrown ethers, which feature prominently in supramolecular chemistry, can be used assensing materials in the construction of potentiometric ion selective electrodes. Up to now,more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anioncomplexes will be described. Liquid membrane sensors based on Schiff's bases and crownethers will then be discussed.