In this research direction, optical and electrochemical sensing principles are integrated for the realization of a sensing device. This includes nanoemulsions embedded in a hydrogel to separate out colloidal sample components. Paper channels decorated with appropriate sensing chemistry can be used for a distance-based, instrument-free readout. Optical sensing particles are read out in a massively serial manner by flow cytometry. Devices based on thin sample layer coulometry aim to avoid the need for recalibration. Flow devices are designed to selectively acidify, alkalanize or desalinate the sample for integrated analysis.
Publications:
(1) Soda, Y.; Bakker, E. Ionic strength-independent potentiometric cation concentration sensing on paper using a tetrabutylammonium-based reference electrode. Sensor Actuat B-Chem 2021, 346. DOI: 10.1016/j.snb.2021.130527.(2) Sailapu, S. K.; Sabate, N.; Bakker, E. Self-Powered Potentiometric Sensors with Memory. ACS Sensors 2021, 6 (10), 3650-3656. DOI: 10.1021/acssensors.1c01273.
(3) Jansod, S.; Bakker, E. Self-Powered Electrochromic Readout of Potentiometric pH Electrodes. Anal Chem 2021, 93 (9), 4263-4269. DOI: 10.1021/acs.analchem.0c05117.
(4) Soda, Y.; Robinson, K. J.; Cherubini, T. J.; Bakker, E. Colorimetric absorbance mapping and quantitation on paper-based analytical devices. Lab Chip 2020, 20 (8), 1441-1448. DOI: 10.1039/d0lc00028k.
(5) Soda, Y.; Citterio, D.; Bakker, E. Equipment-Free Detection of K+ on Microfluidic Paper-Based Analytical Devices Based on Exhaustive Replacement with Ionic Dye in Ion-selective Capillary Sensors. ACS Sensors 2019, 4 (3), 670-677. DOI: 10.1021/acssensors.8b01521.
(6) Soda, Y.; Bakker, E. Quantification of Colorimetric Data for Paper-Based Analytical Devices. ACS Sensors 2019, 4 (12), 3093-3101. DOI: 10.1021/acssensors.9b01802.
(7) Gerold, C. T.; Bakker, E.; Henry, C. S. Selective Distance-Based K+ Quantification on Paper-Based Microfluidics. Anal Chem 2018, 90 (7), 4894-4900. DOI: 10.1021/acs.analchem.8b00559.
(8) Athavale, R.; Pankratova, N.; Dinkel, C.; Bakker, E.; Wehrli, B.; Brand, A. Fast Potentiometric CO2 Sensor for High-Resolution in Situ Measurements in Fresh Water Systems. Environ Sci Technol 2018, 52 (19), 11259-11266. DOI: 10.1021/acs.est.8b02969.
(9) Pankratova, N.; Cuartero, M.; Cherubini, T.; Crespo, G. A.; Bakker, E. In-Line Acidification for Potentiometric Sensing of Nitrite in Natural Waters. Anal Chem 2017, 89 (1), 571-575. DOI: 10.1021/acs.analchem.6b03946.
(10) Cuartero, M.; Pankratova, N.; Cherubini, T.; Crespo, G. A.; Massa, F.; Confalonieri, F.; Bakker, E. In Situ Detection of Species Relevant to the Carbon Cycle in Seawater with Submersible Potentiometric Probes. Environ Sci Tech Let 2017, 4 (10), 410-415. DOI: 10.1021/acs.estlett.7b00388.
(11) Athavale, R.; Dinkel, C.; Wehrli, B.; Bakker, E.; Crespo, G. A.; Brand, A. Robust Solid-Contact Ion Selective Electrodes for High-Resolution In Situ Measurements in Fresh Water Systems. Environ Sci Tech Let 2017, 4 (7), 286-291. DOI: 10.1021/acs.estlett.7b00130.
(12) Afshar, M. G.; Tercier-Waeber, M. L.; Wehrli, B.; Bakker, E. Direct sensing of total alkalinity profile in a stratified lake. Geochem Perspect Let 2017, 3 (1), 85-93. DOI: 10.7185/geochemlet.1709.
(13) Jansod, S.; Afshar, M. G.; Crespo, G. A.; Bakker, E. Alkalinization of Thin Layer Samples with a Selective Proton Sink Membrane Electrode for Detecting Carbonate by Carbonate-Selective Electrodes. Anal Chem 2016, 88 (7), 3444-3448. DOI: 10.1021/acs.analchem.6b00346.
(14) Pankratova, N.; Crespo, G. A.; Afshar, M. G.; Crespi, M. C.; Jeanneret, S.; Cherubini, T.; Tercier-Waeber, M. L.; Pomati, F.; Bakker, E. Potentiometric sensing array for monitoring aquatic systems. Environ Sci-Proc Imp 2015, 17 (5), 906-914. DOI: 10.1039/c5em00038f.
(15) Cuartero, M.; Crespo, G. A.; Bakker, E. Paper-Based Thin-Layer Coulometric Sensor for Halide Determination. Anal Chem 2015, 87 (3), 1981-1990. DOI: 10.1021/ac504400w.
(16) Cuartero, M.; Crespo, G. A.; Bakker, E. Tandem Electrochemical Desalination-Potentiometric Nitrate Sensing for Seawater Analysis. Anal Chem 2015, 87 (16), 8084-8089. DOI: 10.1021/acs.analchem.5b01973.
(17) Athavale, R.; Kokorite, I.; Dinkel, C.; Bakker, E.; Wehrli, B.; Crespo, G. A.; Brand, A. In Situ Ammonium Profiling Using Solid-Contact Ion-Selective Electrodes in Eutrophic Lakes. Anal Chem 2015, 87 (24), 11990-11997. DOI: 10.1021/acs.analchem.5b02424.
(18) Afshar, M. G.; Crespo, G. A.; Bakker, E. Thin-Layer Chemical Modulations by a Combined Selective Proton Pump and pH Probe for Direct Alkalinity Detection. Angew Chem Int Edit 2015, 54 (28), 8110-8113. DOI: 10.1002/anie.201500797.
(19) Dorokhin, D.; Crespo, G. A.; Afshar, M. G.; Bakker, E. A low-cost thin layer coulometric microfluidic device based on an ion-selective membrane for calcium determination. Analyst 2014, 139 (1), 48-51. DOI: 10.1039/c3an01715j.
(20) Sohail, M.; De Marco, R.; Lamb, K.; Bakker, E. Thin layer coulometric determination of nitrate in fresh waters. Anal Chim Acta 2012, 744, 39-44. DOI: 10.1016/j.aca.2012.07.026.
(21) Grygolowicz-Pawlak, E.; Sohail, M.; Pawlak, M.; Neel, B.; Shvarev, A.; de Marco, R.; Bakker, E. Coulometric Sodium Chloride Removal System with Nafion Membrane for Seawater Sample Treatment. Anal Chem 2012, 84 (14), 6158-6165. DOI: 10.1021/ac301096r.
(22) Xu, C.; Wygladacz, K.; Retter, R.; Bell, M.; Bakker, E. Multiplexed flow cytometric sensing of blood electrolytes in physiological samples using fluorescent bulk optode microspheres. Anal Chem 2007, 79 (24), 9505-9512. DOI: 10.1021/ac7016212.
(23) Wygladacz, K.; Radu, A.; Xu, C.; Qin, Y.; Bakker, E. Fiber-optic microsensor array based on fluorescent bulk optode microspheres for the trace analysis of silver ions. Anal Chem 2005, 77 (15), 4706-4712. DOI: 10.1021/ac050856s.
(24) Wygladacz, K.; Bakker, E. Imaging fiber microarray fluorescent ion sensors based on bulk optode microspheres. Anal Chim Acta 2005, 532 (1), 61-69. DOI: 10.1016/j.aca.2004.10.071.
(25) Retter, R.; Peper, S.; Bell, M.; Tsagkatakis, I.; Bakker, E. Flow cytometric ion detection with plasticized poly(vinyl chloride) microspheres containing selective ionophores. Anal Chem 2002, 74 (20), 5420-5425. DOI: 10.1021/ac025782o.