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  • 1. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Coulometric Calcium Pump for Thin Layer Sample Titrations2015Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, nr 19, s. 10125-10130Artikkel i tidsskrift (Fagfellevurdert)
  • 2. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Counter electrode based on an ion-exchanger Donnan exclusion membrane for bioelectroanalysis2014Inngår i: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 61, s. 64-69Artikkel i tidsskrift (Fagfellevurdert)
  • 3. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Direct Ion Speciation Analysis with Ion-Selective Membranes Operated in a Sequential Potentiometric/Time Resolved Chronopotentiometric Sensing Mode2012Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, nr 20, s. 8813-8821Artikkel i tidsskrift (Fagfellevurdert)
  • 4. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Flow Chronopotentiometry with Ion-Selective Membranes for Cation, Anion, and Polyion Detection2016Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, nr 7, s. 3945-3952Artikkel i tidsskrift (Fagfellevurdert)
  • 5. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Thin-Layer Chemical Modulations by a Combined Selective Proton Pump and pH Probe for Direct Alkalinity Detection2015Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, nr 28, s. 8110-8113Artikkel i tidsskrift (Fagfellevurdert)
  • 6. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Dorokhin, Denis
    Neel, Bastien
    Bakker, Eric
    Thin Layer Coulometry of Nitrite with Ion-Selective Membranes2015Inngår i: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 27, nr 3, s. 609-615Artikkel i tidsskrift (Fagfellevurdert)
  • 7. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Xie, Xiaojiang
    Bakker, Eric
    Direct Alkalinity Detection with Ion-Selective Chronopotentiometry2014Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, nr 13, s. 6461-6470Artikkel i tidsskrift (Fagfellevurdert)
  • 8. Ampurdanes, Jordi
    et al.
    Crespo, Gaston A.
    Maroto, Alicia
    Angeles Sarmentero, M.
    Ballester, Pablo
    Xavier Rius, F.
    Determination of choline and derivatives with a solid-contact ion-selective electrode based on octaamide cavitand and carbon nanotubes2009Inngår i: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 25, nr 2, s. 344-349Artikkel i tidsskrift (Fagfellevurdert)
  • 9. Athavale, Rohini
    et al.
    Dinkel, Christian
    Wehrli, Bernhard
    Bakker, Eric
    Crespo, Gaston A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Brand, Andreas
    Robust Solid-Contact Ion Selective Electrodes for High-Resolution In Situ Measurements in Fresh Water Systems2017Inngår i: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS, ISSN 2328-8930, Vol. 4, nr 7, s. 286-291Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biogeochemical processes are often confined to very narrow zones in aquatic systems. Therefore, highly resolved in situ measurements are required to study these processes. Potentiometric solid -contact ion selective electrodes (SC-ISEs) are promising tools for such measurements. SCISEs show good performance in analyses under controlled experimental conditions. Very few sensor designs, however, can sustain the challenges of natural water matrices and external environmental conditions during in situ applications. We fabricated ammonium and pH selective SC-ISEs with functionalized multiwalled carbon nanotubes (f-MWCNT) as a solid contact. Their functionality was tested in the laboratory and applied in situ for vertical profiling in a eutrophic lake. Sensors were insensitive to strong redox changes, high sulfide concentrations, and bright daylight conditions during the application in the lake. In addition, sensors are easily fabricated and exhibit short response times (<10 s). The proposed design of SC-ISEs based on f-MWCNTs is quite suitable for high-resolution in situ profiling of ionic species in fresh water lakes.

  • 10. Athavale, Rohini
    et al.
    Kokorite, Ilga
    Dinkel, Christian
    Bakker, Eric
    Wehrli, Bernhard
    Crespo, Gaston A.
    Brand, Andreas
    In Situ Ammonium Profiling Using Solid-Contact Ion-Selective Electrodes in Eutrophic Lakes2015Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, nr 24, s. 11990-11997Artikkel i tidsskrift (Fagfellevurdert)
  • 11. Bakker, Eric
    et al.
    Crespo, Gaston A.
    Afshar, Majid Gharhaman
    Saxer, Till
    Bendjelid, Karim
    Detecting Heparin in Whole Blood for Point of Care Anticoagulation Control During Surgery2013Inngår i: Chimia (Basel), ISSN 0009-4293, Vol. 67, nr 5Artikkel i tidsskrift (Fagfellevurdert)
  • 12. Bakker, Eric
    et al.
    Crespo, Gaston A.
    Grygolowicz-Pawlak, Ewa
    Mistlberger, Guenter
    Pawlak, Marcin
    Xie, Xiaojiang
    Advancing Membrane Electrodes and Optical Ion Sensors2011Inngår i: Chimia (Basel), ISSN 0009-4293, Vol. 65, nr 3, s. 141-149Artikkel i tidsskrift (Fagfellevurdert)
  • 13. Bakker, Eric
    et al.
    Tercier-Waeber, Mary-Lou
    Cherubini, Thomas
    Crespi, Miguel Coll
    Crespo, Gaston A.
    Cuartero, Maria
    Afshar, Majid Ghahraman
    Jarolimova, Zdenka
    Jeanneret, Stephane
    Mongin, Sandrine
    Neel, Bastien
    Pankratova, Nadezda
    Touilloux, Romain
    Xie, Xiaojiang
    Zhai, Jingying
    Environmental Sensing of Aquatic Systems at the University of Geneva2014Inngår i: Chimia (Basel), ISSN 0009-4293, Vol. 68, nr 11, s. 772-777Artikkel i tidsskrift (Fagfellevurdert)
  • 14.
    Canovas, Rocio
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Sanchez, Sara Padrell
    Karolinska Inst, Dept Clin Sci Intervent & Technol, SE-14186 Stockholm, Sweden.;Karolinska Univ Sjukhuset, Div Obstet & Gynecol, SE-14186 Stockholm, Sweden..
    Parrilla, Marc
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Cuartero, Maria
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Crespo, Gaston A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Cytotoxicity Study of Ionophore-Based Membranes: Toward On Body and in Vivo Ion Sensing2019Inngår i: ACS SENSORS, ISSN 2379-3694, Vol. 4, nr 9, s. 2524-2535Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the most complete study to date comprising in vitro cytotoxicity tests of ion-selective membranes (ISMs) in terms of cell viability, proliferation, and adhesion assays with human dermal fibroblasts. ISMs were prepared with different types of plasticizers and ionophores to be tested in combination with assays that focus on the medium-term and long-term leaching of compounds. Furthermore, the ISMs were prepared in different configurations considering (i) inner-filling solution-type electrodes, (ii) all-solid-state electrodes based on a conventional drop-cast of the membrane, (iii) peeling after the preparation of a wearable sensor, and (iv) detachment from a microneedle-based sensor, thus covering a wide range of membrane shapes. One of the aims of this study, other than the demonstration of the biocompatibility of various ISMs and materials tested herein, is to create an awareness in the scientific community surrounding the need to perform biocompatibility assays during the the very first steps of any sensor development with an intended biomedical application. This will foster meeting the requirements for subsequent on-body application of the sensor and avoiding further problems during massive validations toward the final in vivo use and commercialization of such devices.

  • 15. Ciftci, S.
    et al.
    Cánovas, Rocio
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Neumann, F.
    Paulraj, T.
    Nilsson, M.
    Crespo, Gaston A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Madaboosi, N.
    The sweet detection of rolling circle amplification: Glucose-based electrochemical genosensor for the detection of viral nucleic acid2020Inngår i: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 151, artikkel-id 112002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herein, an isothermal padlock probe-based assay for the simple and portable detection of pathogens coupled with a glucose oxidase (GOx)-based electrochemical readout is reported. Infectious diseases remain a constant threat on a global scale, as in recurring pandemics. Rapid and portable diagnostics hold the promise to tackle the spreading of diseases and decentralising healthcare to point-of-care needs. Ebola, a hypervariable RNA virus causing fatalities of up to 90% for recent outbreaks in Africa, demands immediate attention for bedside diagnostics. The design of the demonstrated assay consists of a rolling circle amplification (RCA) technique, responsible for the generation of nucleic acid amplicons as RCA products (RCPs). The RCPs are generated on magnetic beads (MB) and subsequently, connected via streptavidin-biotin bonds to GOx. The enzymatic catalysis of glucose by the bound GOx allows for an indirect electrochemical measurement of the DNA target. The RCPs generated on the surface of the MB were confirmed by scanning electron microscopy, and among other experimental conditions such as the type of buffer, temperature, concentration of GOx, sampling and measurement time were evaluated for the optimum electrochemical detection. Accordingly, 125 μg mL−1 of GOx with 5 mM glucose using phosphate buffer saline (PBS), monitored for 1 min were selected as the ideal conditions. Finally, we assessed the analytical performance of the biosensing strategy by using clinical samples of Ebola virus from patients. Overall, this work provides a proof-of-concept bioassay for simple and portable molecular diagnostics of emerging pathogens using electrochemical detection, especially in resource-limited settings.

  • 16. Crespi, Miguel Coll
    et al.
    Crespo, Gaston A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Xie, Xiaojiang
    Touilloux, Romain
    Tercier-Waeber, Marylou
    Bakker, Eric
    Agarose hydrogel containing immobilized pH buffer microemulsion without increasing permselectivity2018Inngår i: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 177, s. 191-196Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A heterogeneous pH buffer based on a colloidal emulsion containing ion-exchanger and lipophilic base is described that can be integrated into hydrogels without affecting their ion-exchange properties. Each sphere works on the basis of reversible ion-exchange of hydrogen ions with solution cations, acting as a pH buffer while staying removed from solution in the nonpolar core of the spheres. The ion-exchange mechanism is supported by titration experiments in aqueous emulsion, showing that the nature and concentration of the exchanging solution cations influences the buffer action, with increasing lipophilicity moving the equilibrium to lower pH values. Agarose gels with entrapped pH buffer emulsions and mounted in a transport cell are shown by zero current potentiometry to exhibit negligible permselective properties above an ionic strength of 1 mM, a behavior no different from unmodified agarose, with an observed ion-exchanger concentration of 7 mM in dry agarose. This suggests that such pH buffers do not give rise to substantial ion-exchange properties of the gel material. In a first attempt to control the pH in the vicinity of an electrode surface by this approach, the emulsion was entrapped in an agarose gel in direct contact with a pH electrode, demonstrating the ability to buffer such gel films.

  • 17.
    Crespo, Gaston A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Recent Advances in Ion-selective membrane electrodes for in situ environmental water analysis2017Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 245, s. 1023-1034Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Ion-selective membrane electrodes (ISEs) have become very attractive sensing platforms for environmental water analysis. This review mainly presents recent advances in polymeric-based ISEs relevant to water research and primarily focused on alkali and alkali earth-metal cations, ammonium ions, halide anions and certain oxoanions involved in biogeochemical cycles (e.g. nutrients (NO2 −, NO3 −), carbon (HCO3 −/CO3 2−) and phosphorus (HPO4 2−/H2PO4 −)). Clearly, ISEs have the potential to be the icon of decentralized ion chemical information for water research as in the case of wearable ISE sensors. The modern development of robust ISEs (mainly in all-solid-state format) has allowed an easy implementation either into submersible or non-submersible probes that maintain, to an acceptable degree, the required analytical performance. Remarkable benefits, such as avoidance of sample contamination, sample preservation and determination of perturbations of chemical speciation, are significant to enhancing the fundamental knowledge of ongoing biogeochemical process. A perspective on the current requirements of ISEs in terms of analytical performance and engineering construction is provided initially and is followed by recent contributions listed according to the sampling methodology, including i) on-board/on-site sampling with subsequent coverage of decentralized analysis (on moving or fixed platforms) and ii) in situ monitoring with submersible sensing probes. On the one hand, there is difficulty in making a general statement about ISEs for water research, specifically in terms of whether they are suitable. This lies in the complexity and heterogeneity of the samples. Accordingly, particular scenarios are discussed. On the other hand, it is also evident that further steps are still needed at the fundamental level, including development of receptors, robust membranes and novel alternatives that would enable the sensing of ions at deep-sea. Importantly, there is a plenty of room for improvement and new approaches; and it should be stressed that the recent progress in water research using ISEs has been owing to multidisciplinary efforts. Facing this challenge is very exciting and the development of ISE platforms that enable working in real conditions is quite plausible.

  • 18. Crespo, Gaston A.
    Solid Contact Ion Selective Electrodes Based on Carbon Nanotubes2010Doktoravhandling, monografi (Annet vitenskapelig)
  • 19. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Bakker, Eric
    Chronopotentiometry of pure electrolytes with anion-exchange donnan exclusion membranes2014Inngår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 731, s. 100-106Artikkel i tidsskrift (Fagfellevurdert)
  • 20. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Bakker, Eric
    Direct Detection of Acidity, Alkalinity, and pH with Membrane Electrodes2012Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, nr 23, s. 10165-10169Artikkel i tidsskrift (Fagfellevurdert)
  • 21. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Bakker, Eric
    Reversible Sensing of the Anticoagulant Heparin with Protamine Permselective Membranes2012Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, nr 50, s. 12575-12578Artikkel i tidsskrift (Fagfellevurdert)
  • 22. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Barrabes, Noelia
    Pawlak, Marcin
    Bakker, Eric
    Characterization of Salophen Co(III) Acetate Ionophore for Nitrite Recognition2015Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 179, s. 16-23Artikkel i tidsskrift (Fagfellevurdert)
  • 23. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Dorokhin, Denis
    Bakker, Eric
    Thin Layer Coulometry Based on Ion-Exchanger Membranes for Heparin Detection in Undiluted Human Blood2014Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, nr 3, s. 1357-1360Artikkel i tidsskrift (Fagfellevurdert)
  • 24. Crespo, Gaston A.
    et al.
    Andrade, F J
    Inon, F A
    Tudino, M B
    Kinetic method for the determination of trace amounts of copper(II) in water matrices by its catalytic effect on the oxidation of 1,5-diphenylcarbazide2005Inngår i: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 539, nr 1-2, s. 317-325Artikkel i tidsskrift (Fagfellevurdert)
  • 25. Crespo, Gaston A.
    et al.
    Bakker, Eric
    Dynamic electrochemistry with ionophore based ion-selective membranes2013Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 3, nr 48, s. 25461-25474Artikkel i tidsskrift (Fagfellevurdert)
  • 26. Crespo, Gaston A.
    et al.
    Bakker, Eric
    Ionophore-based ion optodes without a reference ion: electrogenerated chemiluminescence for potentiometric sensors2012Inngår i: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 137, nr 21, s. 4988-4994Artikkel i tidsskrift (Fagfellevurdert)
  • 27. Crespo, Gaston A.
    et al.
    Bakker, Eric
    Afshar, Majid
    Reversible detection of ions with perm-selective membranes2014Patent (Annet (populærvitenskap, debatt, mm))
  • 28. Crespo, Gaston A.
    et al.
    Cuartero, Maria
    Bakker, Eric
    Thin Layer Ionophore-Based Membrane for Multianalyte Ion Activity Detection2015Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, nr 15, s. 7729-7737Artikkel i tidsskrift (Fagfellevurdert)
  • 29. Crespo, Gaston A.
    et al.
    Gugsa, Derese
    Macho, Santiago
    Xavier Rius, F.
    Solid-contact pH-selective electrode using multi-walled carbon nanotubes2009Inngår i: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 395, nr 7, s. 2371-2376Artikkel i tidsskrift (Fagfellevurdert)
  • 30. Crespo, Gaston A.
    et al.
    Macho, Santiago
    Bobacka, Johan
    Rius, F. Xavier
    Transduction Mechanism of Carbon Nanotubes in Solid-Contact Ion-Selective Electrodes2009Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, nr 2, s. 676-681Artikkel i tidsskrift (Fagfellevurdert)
  • 31. Crespo, Gaston A.
    et al.
    Macho, Santiago
    Riu, Jordi
    Ruis, FX
    Electrodes selective for solid contact ions based on carbon nanotubes2007Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Selective Electrodes solid contact ions based on carbon nanotubes. The invention defines a solid selective electrode contact ions comprising a transducer layer of carbon nanotubes which contacts the sensing layer and conducting element. The invention also defines a method for preparing such ion selective electrode solid contact and the use thereof for the qualitative, quantitative or semiquantitative determination of analytes. Said selective contact electrode solid ion allows detect or quantify highly diverse chemical species in a reliable and reproducible manner with the additional advantages derived from its simplicity and low construction cost.

  • 32. Crespo, Gaston A.
    et al.
    Macho, Santiago
    Xavier Rius, F.
    Ion-selective electrodes using carbon nanotubes as ion-to-electron transducers2008Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 80, nr 4, s. 1316-1322Artikkel i tidsskrift (Fagfellevurdert)
  • 33. Crespo, Gaston A.
    et al.
    Mistlberger, Guenter
    Bakker, Eric
    Electrogenerated Chemiluminescence for Potentiometric Sensors2012Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, nr 1, s. 205-207Artikkel i tidsskrift (Fagfellevurdert)
  • 34. Crespo, Gaston A.
    et al.
    Mistlberger, Guenter
    Bakker, Eric
    Electrogenerated chemiluminescence triggered by electroseparation of Ru(bpy)(3)(2+) across a supported liquid membrane2011Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, nr 42, s. 11644-11646Artikkel i tidsskrift (Fagfellevurdert)
  • 35. Crespo, Gaston A.
    et al.
    Mistlberger, Guenter
    Bakker, Eric
    Towards Ion-Selective Membranes with Electrogenerated Chemiluminescence Detection: Visualizing Selective Ru(bpy)(3)(2+) Transport Across a Plasticized Poly(vinyl chloride) Membrane2012Inngår i: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 24, nr 1, s. 61-68Artikkel i tidsskrift (Fagfellevurdert)
  • 36. Cuartero, Maria
    et al.
    Acres, Robert G.
    Bradley, John
    Jarolimova, Zdenka
    Wang, Lu
    Bakker, Eric
    Crespo, Gaston A.
    University of Geneva, Switzerland.
    De Marco, Roland
    Electrochemical Mechanism of Ferrocene-Based Redox Molecules in Thin Film Membrane Electrodes2017Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 238, s. 357-367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cyclic voltammetry (CV) in chloride-based aqueous electrolytes of ferrocene molecule doped thin membranes (similar to 200 nm in thickness) on glassy carbon (GC) substrate electrodes, both plasticized poly (vinyl chloride) (PVC) and unplasticized poly(methyl methacrylate)/poly(decyl methacrylate) (PMMA-PDMA) membranes, has shown that the electrochemical oxidation behavior is irreversible due most likely to degradation of ferrocene at the buried interface (GC vertical bar membrane). Furthermore, CV of the ferrocene molecules at GC electrodes in organic solvents employing chloride-based and chloride-free organic electrolytes has demonstrated that the chloride anion is inextricably linked to this irreversible ferrocene oxidation electrochemistry. Accordingly, we have explored the electrochemical oxidation mechanism of ferrocene-based redox molecules in thin film plasticized and unplasticized polymeric membrane electrodes by coupling synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and near edge X-ray absorption fine structure (NEXAFS) with argon ion sputtering to depth profile the electrochemically oxidized thin membrane systems. With the PVC depth profiling studies, it was not possible to precisely study the influence of chloride on the ferrocene reactivity due to the high atomic ratio of chloride in the PVC membrane; however, the depth profiling results obtained with a chlorine-free polymer (PMMA-PDMA) provided irrefutable evidence for the formation of a chloride-based iron product at the GC| PMMA-PDMA interface. Finally, we have identified conditions that prevent the irreversible conversion of ferrocene by utilizing a high loading of redox active reagent and/or an ionic liquid (IL) membrane plasticizer with high ionicity that suppresses the mass transfer of chloride.

  • 37. Cuartero, Maria
    et al.
    Acres, Robert G.
    De Marco, Roland
    Bakker, Eric
    Crespo, Gaston A.
    Electrochemical Ion Transfer with Thin Films of Poly(3-octylthiophene)2016Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, nr 13, s. 6939-6946Artikkel i tidsskrift (Fagfellevurdert)
  • 38.
    Cuartero, Maria
    et al.
    Univ Geneva, Dept Inorgan & Analyt Chem, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland..
    Acres, Robert G.
    ANSTO, Australian Synchrotron, 800 Blackburn Rd, Clayton, Vic 3168, Australia..
    Jarolimova, Zdenka
    Univ Geneva, Dept Inorgan & Analyt Chem, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland..
    Bakker, Eric
    Univ Geneva, Dept Inorgan & Analyt Chem, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland..
    Crespo, Gaston A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi. Univ Geneva, Dept Inorgan & Analyt Chem, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland.
    De Marco, Roland
    Univ Sunshine Coast, Fac Sci Hlth Educ & Engn, 90 Sippy Downs Dr, Sippy Downs, Qld 4556, Australia.;Univ Queensland, Sch Chem & Mol Biosci, Brisbane, Qld 4072, Australia.;Curtin Univ, Dept Chem, GPO Box U1987, Perth, WA 6109, Australia..
    Electron Hopping between Fe 3d States in Ethynylferrocene-doped Poly(Methyl Methacrylate)-poly(Decyl Methacrylate) Copolymer Membranes2018Inngår i: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 30, nr 4, s. 596-601Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Synchrotron radiation-valence band spectroscopy (SR-VBS) has been utilized in a study of redox molecule valence states implicated in the electron hopping mechanism of ethynylferrocene in unplasticized poly(methyl methacrylate)-poly(decyl methacrylate) [PMMA-PDMA] membranes. In this communication, it is revealed that, at high concentrations of ethynylferrocene, there are observable Fe 3d valence states that are likely linked to electron hopping between ferrocene moieties of neighbouring redox molecules. Furthermore, electrochemically induced stratification of ethynylferrocene in an oxidized PMMA-PDMA membrane produces a gradient of Fe 3d states toward the buried interface at the glassy carbon/PMMA-PDMA membrane enabling electron hopping and electrochemical reactivity of dissolved ethynylferrocene across this buried film.

  • 39. Cuartero, Maria
    et al.
    Bishop, Josiah
    Walker, Raymart
    Acres, Robert G
    Bakker, Eric
    De Marco, Roland
    Crespo, Gaston A.
    University of Geneva, Quai Ernest-Ansermet 30, Geneva, CH-1211, Switzerland.
    Evidence of double layer/capacitive charging in carbon nanomaterial-based solid contact polymeric ion-selective electrodes2016Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 52, nr 62, s. 9703-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the first direct spectroscopic evidence for double layer or capacitive charging of carbon nanomaterial-based solid contacts in all-solid-state polymeric ion-selective electrodes (ISEs). Here, we used synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and SR valence band (VB) spectroscopy in the elucidation of the charging mechanism of the SCs.

  • 40.
    Cuartero, Maria
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Chai, Lijun
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Zhang, Biaobiao
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi.
    De Marco, Roland
    Univ Sunshine Coast, Fac Sci Hlth Educ & Engn, 90s Sippy Downs Dr, Sippy Downs, Qld 4556, Australia.;Univ Queensland, Sch Chem & Mol Biosci, Brisbane, Qld 4072, Australia.;Curtin Univ, Fuels & Energy Technol Inst, Perth, WA 6102, Australia..
    Crespo, Gaston A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Ferrocene self assembled monolayer as a redox mediator for triggering ion transfer across nanometer-sized membranes2019Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 315, s. 84-93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modulation of ion-transfer processes across nanometer-sized voltammetry membranes by ferrocene-based self-assembled monolayer on regular glassy carbon electrode is herein demonstrated. The composition of the membrane is advantageously tuned to promote either cation or anion transfer: the presence of an exchangeable cation results in cation transfer, whereas a lipophilic salt induces anion transfer through the fulfilment of the electroneutrality of the system. When an anodic scan oxidizes ferrocene moieties in the monolayer, these are stabilized by the pairing of lipophilic anions present in the membrane. As a result, either, hydrophilic cations present in the membrane are expelled into the solution or anions enter from the solution generating hence reversible and voltammetric waves for these transfers. The use of a redox active monolayer rather than a conducting polymer film or a redox active compound into the membrane overcomes a number of drawbacks previously manifested by these systems. The confinement of the redox process in a thin film at the immediate vicinity of the membrane allows to avoid the need of elevated number of redox moieties to be sued in the membrane, therefore suppressing its acute leaching and being compatible with the incorporation of both cation and anion ionophores for the first time. In this sense, assisted transfer of lithium and chloride are shown as proof-of-concept. Here, the peak potential of the associated voltammetric waves shifts according to the Nernst equation, in analogy to potentiometric sensors. Analytical detection of lithium and chloride ions in real samples is additionally presented.

  • 41.
    Cuartero, Maria
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Colozza, Noemi
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Fernandez-Perez, Bibiana M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Crespo, Gaston A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Why ammonium detection is particularly challenging but insightful with ionophore-based potentiometric sensors - an overview of the progress in the last 20 years2020Inngår i: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 145, nr 9, s. 3188-3210Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The monitoring of ammonium ion concentration has gained the attention of researchers from multiple fields since it is a crucial parameter with respect to environmental and biomedical applications. For example, ammonium is considered to be a quality indicator of natural waters as well as a potential biomarker of an enzymatic byproduct in key physiological reactions. Among the classical analytical methods used for the detection of ammonium ions, potentiometric ion-selective electrodes (ISEs) have attracted special attention in the scientific community because of their advantages such as cost-effectiveness, user-friendly features, and miniaturization ability, which facilitate easy portable measurements. Regarding the analytical performance, the key component of ISEs is the selective receptor, labelled as an ionophore in ISE jargon. Indeed, the preference of an ionophore for ammonium amongst other ions (i.e., selectivity) is a factor that primarily dictates the limit of detection of the electrode when performing measurements in real samples. A careful assessment of the literature for the last 20 years reveals that nonactin is by far the most employed ammonium ionophore to date. Despite the remarkable cross-interference of potassium over the ammonium response of nonactin-based ISEs, analytical applications comprising water quality assessment, clinical tests in biological fluids, and sweat monitoring during sports practice have been successfully researched. Nevertheless, there is evident difficulty in the determination of close-to-micromolar levels of ammonium in real samples with a significant potassium background level (i.e., millimolar concentration). This fact has fostered the search for a large variety of ammonium ionophores over the years, which are critically inspected herein. Overall, we provide an easily readable state of the art accompanied by a comprehensive description of other types of ammonium electrodes, including commercially available units. We conclude that newer breakthroughs are still required in the field to reach the desired analytical applications.

  • 42.
    Cuartero, Maria
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Crespo, Gaston A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    All-solid-state potentiometric sensors: A new wave for in situ aquatic research2018Inngår i: Current Opinion in Electrochemistry, ISSN 2451-9103, Vol. 10, s. 98-106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Over the last few years, all-solid-state potentiometric ion-selective sensors have demonstrated a huge potential for environmental water analysis. Beyond the excellent analytical performances exhibited in benchtop conditions for the detection of important targets (e.g. pH, species relevant to the carbon and nitrogen cycles, trace metals), the challenge now lies in bringing those sensors to in situ format and obtaining valuable chemical information directly in the field while minimizing or avoiding the need for sampling. Technically speaking, the instrumentation for potentiometric assessment is extremely simple, low cost and requires minimal space. In addition, the all-solid-state configuration seems ideal to fabricate miniaturized sensors with sufficient analytical performance to detect certain ions in water resources. Herein, we highlight the power of all-solid-state potentiometric sensors applied to environmental water analysis providing a threefold overview: (i) the recent materials used in the fabrication of all-solid-state polymeric membrane electrodes, both the solid contact and ion-selective membrane; (ii) a collection of the main targets explored during the last 5 years; and (iii) examples of the most recent and relevant in situ applications employing submersible equipment. Throughout the review, issues such as ‘What are the real implications of all-solid-state membrane electrodes in the environmental field?’ and ‘To what extent has the effort in developing new sensors over time been well-exploited?’ are addressed. Convincingly, all-solid-state potentiometric sensors are positioning as a unique in situ interface providing real-time data that allow for an understanding of ongoing biogeochemical processes and possible anthropogenic activities implications.

  • 43.
    Cuartero, Maria
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Crespo, Gaston A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Using Potentiometric Electrodes Based on Nonselective Polymeric Membranes as Potential Universal Detectors for Ion Chromatography: Investigating an Original Research Problem from an Inquiry-Based-Learning Perspective2018Inngår i: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328, Vol. 95, nr 12, s. 2172-2181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Because traditional laboratory practices in advanced chemistry education are being replaced by inquiry based approaches, we present herein a new laboratory activity based on a small research project that was designed and executed by students. The laboratory project aims at answering a well-defined research question: how far can potentiometric electrodes based on nonselective polymeric membranes be used as universal detectors in ion chromatography (IC)? Hence, the experiments were designed and conducted to explore the analytical performances of potentiometric electrodes based on different commercial membranes that are typically used in electrodialysis. The nonselective behavior shown by the electrodes permits a critical evaluation of their further implementation as a universal detector of anions in regular IC. Thus, the students were able to integrate a nonselective potentiometric sensor to analyze several anions in flow mode, mimicking the signal that is to be obtained using such electrodes as an IC detector. The proposed practice covers different pedagogical purposes: (i) to develop competence toward "thinking like a scientist" through reflective teaching; (ii) to promote argumentation skills and critical decision making; (iii) to improve students' research-planning and experimental-design skills; (iv) to refresh conceptual knowledge about analytical detectors, which typically goes unnoticed in laboratory practices; and (v) to reinforce students' knowledge about the basis of potentiometry. Furthermore, the present document may serve as an easy guide to develop other laboratory practices based on potentiometric sensors.

  • 44. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Afshar, Majid Ghahraman
    Bakker, Eric
    Exhaustive Thin-Layer Cyclic Voltammetry for Absolute Multianalyte Halide Detection2014Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, nr 22, s. 11387-11395Artikkel i tidsskrift (Fagfellevurdert)
  • 45. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Ionophore-Based Voltammetric Ion Activity Sensing with Thin Layer Membranes2016Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, nr 3, s. 1654-1660Artikkel i tidsskrift (Fagfellevurdert)
  • 46. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Paper-Based Thin-Layer Coulometric Sensor for Halide Determination2015Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, nr 3, s. 1981-1990Artikkel i tidsskrift (Fagfellevurdert)
  • 47. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Polyurethane Ionophore-Based Thin Layer Membranes for Voltammetric Ion Activity Sensing2016Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, nr 11, s. 5649-5654Artikkel i tidsskrift (Fagfellevurdert)
  • 48. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Tandem Electrochemical Desalination-Potentiometric Nitrate Sensing for Seawater Analysis2015Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, nr 16, s. 8084-8089Artikkel i tidsskrift (Fagfellevurdert)
  • 49. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Thin Layer Samples Controlled by Dynamic Electrochemistry2015Inngår i: Chimia (Basel), ISSN 0009-4293, Vol. 69, nr 4, s. 203-206Artikkel i tidsskrift (Fagfellevurdert)
  • 50. Cuartero, Maria
    et al.
    Pankratova, Nadezda
    Cherubini, Thomas
    Crespo, Gaston A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Massa, Francesco
    Confalonieri, Fabio
    Bakker, Eric
    In Situ Detection of Species Relevant to the Carbon Cycle in Seawater with Submersible Potentiometric Probes2017Inngår i: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS, ISSN 2328-8930, Vol. 4, nr 10, s. 410-415Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the development of a submersible probe for the simultaneous potentiometric detection of carbonate, calcium, and pH in seawater. All-solid-state electrodes incorporating nanomaterials provide an adequate response time (<10 s), stability (drifts of <0.9 mV h(-1)), reproducibility (calibration parameter deviation of <0.7%), and accuracy (deviation of <8% compared to reference techniques) for real-time monitoring of seawater using a flow system. The functioning of the deployable prototype was checked in an outdoor mesocosm and via long-term monitoring in Genoa Harbor. The electrodes worked properly for 3 weeks, and the system demonstrated the capability to autonomously operate with routines for repetitive measurements, data storage, and management. In situ profiles observed in Genoa Harbor and Arcachon Bay were validated using on site and ex situ techniques. The validation of in situ-detected carbonate is a challenge because both re-equilibration of the sample with atmospheric CO2 and the use of apparent thermodynamic constants for speciation calculations lead to some differences (<20% deviation). The submersible probe is a promising tool for obtaining rapid and trustworthy information about chemical levels in marine systems. Moreover, the fluidic approach allows for the integration of other ion sensors that may require sample pretreatment.

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