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  • 1. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Coulometric Calcium Pump for Thin Layer Sample Titrations2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 19, p. 10125-10130Article in journal (Refereed)
  • 2. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Counter electrode based on an ion-exchanger Donnan exclusion membrane for bioelectroanalysis2014In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 61, p. 64-69Article in journal (Refereed)
  • 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 Mode2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 20, p. 8813-8821Article in journal (Refereed)
  • 4. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Flow Chronopotentiometry with Ion-Selective Membranes for Cation, Anion, and Polyion Detection2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 7, p. 3945-3952Article in journal (Refereed)
  • 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 Detection2015In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, no 28, p. 8110-8113Article in journal (Refereed)
  • 6. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Dorokhin, Denis
    Neel, Bastien
    Bakker, Eric
    Thin Layer Coulometry of Nitrite with Ion-Selective Membranes2015In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 27, no 3, p. 609-615Article in journal (Refereed)
  • 7. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Xie, Xiaojiang
    Bakker, Eric
    Direct Alkalinity Detection with Ion-Selective Chronopotentiometry2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 13, p. 6461-6470Article in journal (Refereed)
  • 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 nanotubes2009In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 25, no 2, p. 344-349Article in journal (Refereed)
  • 9. Athavale, Rohini
    et al.
    Dinkel, Christian
    Wehrli, Bernhard
    Bakker, Eric
    Crespo, Gaston A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Brand, Andreas
    Robust Solid-Contact Ion Selective Electrodes for High-Resolution In Situ Measurements in Fresh Water Systems2017In: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS, ISSN 2328-8930, Vol. 4, no 7, p. 286-291Article in journal (Refereed)
    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 Lakes2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 24, p. 11990-11997Article in journal (Refereed)
  • 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 Surgery2013In: Chimia (Basel), ISSN 0009-4293, Vol. 67, no 5Article in journal (Refereed)
  • 12. Bakker, Eric
    et al.
    Crespo, Gaston A.
    Grygolowicz-Pawlak, Ewa
    Mistlberger, Guenter
    Pawlak, Marcin
    Xie, Xiaojiang
    Advancing Membrane Electrodes and Optical Ion Sensors2011In: Chimia (Basel), ISSN 0009-4293, Vol. 65, no 3, p. 141-149Article in journal (Refereed)
  • 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 Geneva2014In: Chimia (Basel), ISSN 0009-4293, Vol. 68, no 11, p. 772-777Article in journal (Refereed)
  • 14. Crespi, Miguel Coll
    et al.
    Crespo, Gaston A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Xie, Xiaojiang
    Touilloux, Romain
    Tercier-Waeber, Marylou
    Bakker, Eric
    Agarose hydrogel containing immobilized pH buffer microemulsion without increasing permselectivity2018In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 177, p. 191-196Article in journal (Refereed)
    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.

  • 15.
    Crespo, Gaston A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Recent Advances in Ion-selective membrane electrodes for in situ environmental water analysis2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 245, p. 1023-1034Article, review/survey (Refereed)
    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.

  • 16. Crespo, Gaston A.
    Solid Contact Ion Selective Electrodes Based on Carbon Nanotubes2010Doctoral thesis, monograph (Other academic)
  • 17. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Bakker, Eric
    Chronopotentiometry of pure electrolytes with anion-exchange donnan exclusion membranes2014In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 731, p. 100-106Article in journal (Refereed)
  • 18. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Bakker, Eric
    Direct Detection of Acidity, Alkalinity, and pH with Membrane Electrodes2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 23, p. 10165-10169Article in journal (Refereed)
  • 19. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Bakker, Eric
    Reversible Sensing of the Anticoagulant Heparin with Protamine Permselective Membranes2012In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, no 50, p. 12575-12578Article in journal (Refereed)
  • 20. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Barrabes, Noelia
    Pawlak, Marcin
    Bakker, Eric
    Characterization of Salophen Co(III) Acetate Ionophore for Nitrite Recognition2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 179, p. 16-23Article in journal (Refereed)
  • 21. 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 Blood2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 3, p. 1357-1360Article in journal (Refereed)
  • 22. 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-diphenylcarbazide2005In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 539, no 1-2, p. 317-325Article in journal (Refereed)
  • 23. Crespo, Gaston A.
    et al.
    Bakker, Eric
    Dynamic electrochemistry with ionophore based ion-selective membranes2013In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 3, no 48, p. 25461-25474Article in journal (Refereed)
  • 24. Crespo, Gaston A.
    et al.
    Bakker, Eric
    Ionophore-based ion optodes without a reference ion: electrogenerated chemiluminescence for potentiometric sensors2012In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 137, no 21, p. 4988-4994Article in journal (Refereed)
  • 25. Crespo, Gaston A.
    et al.
    Bakker, Eric
    Afshar, Majid
    Reversible detection of ions with perm-selective membranes2014Patent (Other (popular science, discussion, etc.))
  • 26. Crespo, Gaston A.
    et al.
    Cuartero, Maria
    Bakker, Eric
    Thin Layer Ionophore-Based Membrane for Multianalyte Ion Activity Detection2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 15, p. 7729-7737Article in journal (Refereed)
  • 27. Crespo, Gaston A.
    et al.
    Gugsa, Derese
    Macho, Santiago
    Xavier Rius, F.
    Solid-contact pH-selective electrode using multi-walled carbon nanotubes2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 395, no 7, p. 2371-2376Article in journal (Refereed)
  • 28. Crespo, Gaston A.
    et al.
    Macho, Santiago
    Bobacka, Johan
    Rius, F. Xavier
    Transduction Mechanism of Carbon Nanotubes in Solid-Contact Ion-Selective Electrodes2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 2, p. 676-681Article in journal (Refereed)
  • 29. Crespo, Gaston A.
    et al.
    Macho, Santiago
    Riu, Jordi
    Ruis, FX
    Electrodes selective for solid contact ions based on carbon nanotubes2007Patent (Other (popular science, discussion, etc.))
    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.

  • 30. Crespo, Gaston A.
    et al.
    Macho, Santiago
    Xavier Rius, F.
    Ion-selective electrodes using carbon nanotubes as ion-to-electron transducers2008In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 80, no 4, p. 1316-1322Article in journal (Refereed)
  • 31. Crespo, Gaston A.
    et al.
    Mistlberger, Guenter
    Bakker, Eric
    Electrogenerated Chemiluminescence for Potentiometric Sensors2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 1, p. 205-207Article in journal (Refereed)
  • 32. Crespo, Gaston A.
    et al.
    Mistlberger, Guenter
    Bakker, Eric
    Electrogenerated chemiluminescence triggered by electroseparation of Ru(bpy)(3)(2+) across a supported liquid membrane2011In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 42, p. 11644-11646Article in journal (Refereed)
  • 33. 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) Membrane2012In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 24, no 1, p. 61-68Article in journal (Refereed)
  • 34. 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 Electrodes2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 238, p. 357-367Article in journal (Refereed)
    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.

  • 35. 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)2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 13, p. 6939-6946Article in journal (Refereed)
  • 36.
    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, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. 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 Membranes2018In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 30, no 4, p. 596-601Article in journal (Refereed)
    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.

  • 37. Cuartero, Maria
    et al.
    Bishop, Josiah
    Walker, Raymart
    Acres, Robert G
    Bakker, Eric
    De Marco, Roland
    Crespo, Gaston A.
    Evidence of double layer/capacitive charging in carbon nanomaterial-based solid contact polymeric ion-selective electrodes2016In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 52, no 62, p. 9703-6Article in journal (Refereed)
  • 38.
    Cuartero, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Chai, Lijun
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Zhang, Biaobiao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    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, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Ferrocene self assembled monolayer as a redox mediator for triggering ion transfer across nanometer-sized membranes2019In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 315, p. 84-93Article in journal (Refereed)
    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.

  • 39.
    Cuartero, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Crespo, Gaston A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    All-solid-state potentiometric sensors: A new wave for in situ aquatic research2018In: Current Opinion in Electrochemistry, ISSN 2451-9103, Vol. 10, p. 98-106Article in journal (Refereed)
    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.

  • 40.
    Cuartero, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Crespo, Gaston A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    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 Perspective2018In: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328, Vol. 95, no 12, p. 2172-2181Article in journal (Refereed)
    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.

  • 41. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Afshar, Majid Ghahraman
    Bakker, Eric
    Exhaustive Thin-Layer Cyclic Voltammetry for Absolute Multianalyte Halide Detection2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 22, p. 11387-11395Article in journal (Refereed)
  • 42. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Ionophore-Based Voltammetric Ion Activity Sensing with Thin Layer Membranes2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 3, p. 1654-1660Article in journal (Refereed)
  • 43. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Paper-Based Thin-Layer Coulometric Sensor for Halide Determination2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 3, p. 1981-1990Article in journal (Refereed)
  • 44. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Polyurethane Ionophore-Based Thin Layer Membranes for Voltammetric Ion Activity Sensing2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 11, p. 5649-5654Article in journal (Refereed)
  • 45. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Tandem Electrochemical Desalination-Potentiometric Nitrate Sensing for Seawater Analysis2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 16, p. 8084-8089Article in journal (Refereed)
  • 46. Cuartero, Maria
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Thin Layer Samples Controlled by Dynamic Electrochemistry2015In: Chimia (Basel), ISSN 0009-4293, Vol. 69, no 4, p. 203-206Article in journal (Refereed)
  • 47. Cuartero, Maria
    et al.
    Pankratova, Nadezda
    Cherubini, Thomas
    Crespo, Gaston A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Massa, Francesco
    Confalonieri, Fabio
    Bakker, Eric
    In Situ Detection of Species Relevant to the Carbon Cycle in Seawater with Submersible Potentiometric Probes2017In: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS, ISSN 2328-8930, Vol. 4, no 10, p. 410-415Article in journal (Refereed)
    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.

  • 48.
    Cánovas, Rocío
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Cuartero, Maria
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Crespo, Gaston A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Modern creatinine (Bio)sensing: Challenges of point-of-care platforms2019In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 130, p. 110-124Article, review/survey (Refereed)
    Abstract [en]

    The importance of knowing creatinine levels in the human body is related to the possible association with renal, muscular and thyroid dysfunction. Thus, the accurate detection of creatinine may indirectly provide information surrounding those functional processes, therefore contributing to the management of the health status of the individual and early diagnosis of acute diseases. The questions at this point are: to what extent is creatinine information clinically relevant?; and do modern creatinine (bio)sensing strategies fulfil the real needs of healthcare applications? The present review addresses these questions by means of a deep analysis of the creatinine sensors reported in the literature over the last five years. There is a wide range of techniques for detecting creatinine, most of them based on optical readouts (20 of the 33 papers collected in this review). However, the use of electrochemical techniques (13 of the 33 papers) is recently emerging in alignment with the search for a definitive and trustworthy creatinine detection at the point-of-care level. In this sense, biosensors (7 of the 33 papers) are being established as the most promising alternative over the years. While creatinine levels in the blood seem to provide better information about patient status, none of the reported sensors display adequate selectivity in such a complex matrix. In contrast, the analysis of other types of biological samples (e.g., saliva and urine) seems to be more viable in terms of simplicity, cross-selectivity and (bio)fouling, besides the fact that its extraction does not disturb individual's well-being. Consequently, simple tests may likely be used for the initial check of the individual in routine analysis, and then, more accurate blood detection of creatinine could be necessary to provide a more genuine diagnosis and/or support the corresponding decision-making by the physician. Herein, we provide a critical discussion of the advantages of current methods of (bio)sensing of creatinine, as well as an overview of the drawbacks that impede their definitive point-of-care establishment.

  • 49. Dorokhin, Denis
    et al.
    Crespo, Gaston A.
    Afshar, Majid Ghahraman
    Bakker, Eric
    A low-cost thin layer coulometric microfluidic device based on an ion-selective membrane for calcium determination2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 1, p. 48-51Article in journal (Refereed)
  • 50. Duezguen, Ali
    et al.
    Zelada-Guillen, Gustavo A.
    Crespo, Gaston A.
    Macho, Santiago
    Riu, Jordi
    Xavier Rius, F.
    Nanostructured materials in potentiometry2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, no 1, p. 171-181Article in journal (Refereed)
12 1 - 50 of 91
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