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McPeak JE, Segantini M, Marcozzi G, Dona I, Künstner S, Chu A, Kern M, Poncelet M, Driesschaert B, Anders J, Lips K. Operando detection of dissolved oxygen in fluid solution using a submersible rapid scan EPR on a chip dipstick sensor. Sci Rep 2025; 15:9872. [PMID: 40119031 PMCID: PMC11928686 DOI: 10.1038/s41598-025-93591-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2024] [Accepted: 03/07/2025] [Indexed: 03/24/2025] Open
Abstract
Electron paramagnetic resonance (EPR) is an accurate and efficient technique to probe unpaired electrons in many applications across materials science, chemistry, and biology. Dynamic processes are investigated using EPR; however, these applications are limited by the use of resonator-based spectrometers such that the entire process must be confined to the resonator. The EPR-on-a-chip (EPRoC) device circumvents this limitation by integrating the entire EPR spectrometer into a single microchip. In this approach, the coil of a voltage-controlled oscillator (VCO) is used as the microwave source and detector simultaneously, operating under a protective coating such that the device may be placed in the sample solution directly. Additionally, improvements in sensitivity via rapid scan EPR (RS-EPR/RS-EPRoC) increase the accessible applications where SNR per measurement time is the fundamental limit. The herein reported device combines a dipstick EPRoC sensor with the enhanced sensitivity of frequency-swept frequency modulated rapid scan to measure triarylmethyl (trityl, Ox071) oxygen-sensitive probes dissolved in aqueous solutions. EPR spectra of Ox071 solutions were recorded using the RS-EPRoC sensor while varying the oxygen concentration of the solution between normal atmosphere and after purging the solution with nitrogen gas. We demonstrate that EPRoC may be employed to monitor dissolved oxygen in fluid solution in an online fashion.
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Affiliation(s)
- Joseph E McPeak
- Berlin Joint EPR Laboratory and EPR4Energy, Department Spins in Energy Conversion and Quantum Information Science (ASPIN), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.
- Department of Chemistry, Novo Nordisk Foundation Pulse EPR Center, University of Copenhagen, Copenhagen, Denmark.
| | - Michele Segantini
- Berlin Joint EPR Laboratory and EPR4Energy, Department Spins in Energy Conversion and Quantum Information Science (ASPIN), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | - Gianluca Marcozzi
- Berlin Joint EPR Laboratory and EPR4Energy, Department Spins in Energy Conversion and Quantum Information Science (ASPIN), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | - Irene Dona
- Berlin Joint EPR Laboratory and EPR4Energy, Department Spins in Energy Conversion and Quantum Information Science (ASPIN), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | - Silvio Künstner
- Berlin Joint EPR Laboratory and EPR4Energy, Department Spins in Energy Conversion and Quantum Information Science (ASPIN), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | - Anh Chu
- Institute of Smart Sensors, Universität Stuttgart, Stuttgart, Germany
| | - Michal Kern
- Institute of Smart Sensors, Universität Stuttgart, Stuttgart, Germany
| | - Martin Poncelet
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, USA
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, USA
| | - Benoit Driesschaert
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, USA
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, USA
| | - Jens Anders
- Institute of Smart Sensors, Universität Stuttgart, Stuttgart, Germany
- Center for Integrated Quantum Science and Technology (IQST), Stuttgart and Ulm, Germany
| | - Klaus Lips
- Berlin Joint EPR Laboratory and EPR4Energy, Department Spins in Energy Conversion and Quantum Information Science (ASPIN), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
- Berlin Joint EPR Laboratory, Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
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Segantini M, Marcozzi G, Elrifai T, Shabratova E, Höflich K, Deaconeasa M, Niemann V, Pietig R, McPeak JE, Anders J, Naydenov B, Lips K. Compact Electron Paramagnetic Resonance on a Chip Spectrometer Using a Single Sided Permanent Magnet. ACS Sens 2024; 9:5099-5108. [PMID: 39326012 PMCID: PMC11519922 DOI: 10.1021/acssensors.4c00788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 09/10/2024] [Accepted: 09/24/2024] [Indexed: 09/28/2024]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy provides information about the physical and chemical properties of materials by detecting paramagnetic states. Conventional EPR measurements are performed in high Q resonator using large electromagnets which limits the available space for operando experiments. Here we present a solution toward a portable EPR sensor based on the combination of the EPR-on-a-Chip (EPRoC) and a single-sided permanent magnet. This device can be placed directly into the sample environment (i.e., catalytic reaction vessels, ultrahigh vacuum deposition chambers, aqueous environments, etc.) to conduct in situ and operando measurements. The EPRoC reported herein is comprised of an array of 14 voltage-controlled oscillator (VCO) coils oscillating at 7 GHz. By using a single grain of crystalline BDPA, EPR measurements at different positions of the magnet with respect to the VCO array were performed. It was possible to create a 2D spatial map of a 1.5 mm × 5 mm region of the magnetic field with 50 μm resolution. This allowed for the determination of the magnetic field intensity and homogeneity, which are found to be 254.69 mT and 700 ppm, respectively. The magnetic field was mapped also along the vertical direction using a thin film a-Si layer. The EPRoC and permanent magnet were combined to form a miniaturized EPR spectrometer to perform experiments on tempol (4-hydroxy-2,2,6,6-teramethylpiperidin-1-oxyl) dissolved in an 80% glycerol and 20% water solution. It was possible to determine the molecular tumbling correlation time and to establish a calibration procedure to quantify the number of spins within the sample.
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Affiliation(s)
- Michele Segantini
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Gianluca Marcozzi
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Tarek Elrifai
- Institute
of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Ekaterina Shabratova
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Leibniz-Institut
für Höchstfrequenztechnik, Ferdinand-Braun-Institut gGmbH, 12489 Berlin, Germany
| | - Katja Höflich
- Leibniz-Institut
für Höchstfrequenztechnik, Ferdinand-Braun-Institut gGmbH, 12489 Berlin, Germany
| | | | | | | | - Joseph E. McPeak
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Jens Anders
- Institute
of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
- Center
for Integrated Quantum Science and Technology, 70569 Stuttgart and Ulm, Germany
| | - Boris Naydenov
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Klaus Lips
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Berlin Joint
EPR Laboratory, Fachbereich Physik, Freie
Universität Berlin, 14195 Berlin, Germany
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Salikhov KM, Eaton SS, Eaton GR. Celebration of 80 years of EPR. APPLIED MAGNETIC RESONANCE 2024; 55:869-888. [PMID: 40191657 PMCID: PMC11970927 DOI: 10.1007/s00723-024-01688-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2024] [Revised: 07/17/2024] [Accepted: 07/18/2024] [Indexed: 04/09/2025]
Abstract
We celebrate 80 years of EPR with a special issue of Applied Magnetic Resonance featuring both reviews and regular research articles. The focus is new opportunities for application of EPR and new directions for development of EPR. This introduction concisely surveys the scope of EPR and hints at future developments.
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Affiliation(s)
- Kev M Salikhov
- Zavoisky Physical-Technical Institute, Russian Academy of Sciences, Sibirsky trakt 10/7 Kazan 420029, Russian Federation
| | - Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado USA 80210
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado USA 80210
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Künstner S, McPeak JE, Chu A, Kern M, Wick M, Dinse KP, Anders J, Naydenov B, Lips K. Microwave field mapping for EPR-on-a-chip experiments. SCIENCE ADVANCES 2024; 10:eado5467. [PMID: 39151005 PMCID: PMC11801239 DOI: 10.1126/sciadv.ado5467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 07/12/2024] [Indexed: 08/18/2024]
Abstract
Electron paramagnetic resonance-on-a-chip (EPRoC) devices use small voltage-controlled oscillators (VCOs) for both the excitation and detection of the EPR signal, allowing access to unique sample environments by lifting the restrictions imposed by resonator-based EPR techniques. EPRoC devices have been successfully used at multiple frequencies (7 to 360 gigahertz) and have demonstrated their utility in producing high-resolution spectra in a variety of spin centers. To enable quantitative measurements using EPRoC devices, the spatial distribution of the B1 field produced by the VCOs must be known. As an example, the field distribution of a 12-coil VCO array EPRoC operating at 14 gigahertz is described in this study. The frequency modulation-recorded EPR spectra of a "point"-like and a thin-film sample were investigated while varying the position of both samples in three directions. The results were compared to COMSOL simulations of the B1-field intensity. The EPRoC array sensitive volume was determined to be ~19 nanoliters. Implications for possible EPR applications are discussed.
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Affiliation(s)
- Silvio Künstner
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Joseph E. McPeak
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Anh Chu
- Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Michal Kern
- Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Markus Wick
- Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Klaus-Peter Dinse
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Institute for Microelectronics Stuttgart (IMS CHIPS), Allmandring 30a, 70569 Stuttgart, Germany
| | - Jens Anders
- Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
- Institute for Microelectronics Stuttgart (IMS CHIPS), Allmandring 30a, 70569 Stuttgart, Germany
- Center for Integrated Quantum Science and Technology (IQST), Stuttgart and Ulm, Germany
| | - Boris Naydenov
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Berlin Joint EPR Laboratory, Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Klaus Lips
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Berlin Joint EPR Laboratory, Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
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Künstner S, McPeak JE, Chu A, Kern M, Dinse KP, Naydenov B, Fischer P, Anders J, Lips K. Monitoring the state of charge of vanadium redox flow batteries with an EPR-on-a-Chip dipstick sensor. Phys Chem Chem Phys 2024; 26:17785-17795. [PMID: 38874514 DOI: 10.1039/d4cp00373j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
The vanadium redox flow battery (VRFB) is considered a promising candidate for large-scale energy storage in the transition from fossil fuels to renewable energy sources. VRFBs store energy by electrochemical reactions of different electroactive species dissolved in electrolyte solutions. The redox couples of VRFBs are VO2+/VO2+ and V2+/V3+, the ratio of which to the total vanadium content determines the state of charge (SOC). V(IV) and V(II) are paramagnetic half-integer spin species detectable and quantifiable with electron paramagnetic resonance spectroscopy (EPR). Common commercial EPR spectrometers, however, employ microwave cavity resonators which necessitate the use of large electromagnets, limiting their application to dedicated laboratories. For an SOC monitoring device for VRFBs, a small, cost-effective submersible EPR spectrometer, preferably with a permanent magnet, is desirable. The EPR-on-a-Chip (EPRoC) spectrometer miniaturises the complete EPR spectrometer onto a single microchip by utilising the coil of a voltage-controlled oscillator as both microwave source and detector. It is capable of sweeping the frequency while the magnetic field is held constant enabling the use of small permanent magnets. This drastically reduces the experimental complexity of EPR. Hence, the EPRoC fulfils the requirements for an SOC sensor. We, therefore, evaluate the potential for utilisation of an EPRoC dipstick spectrometer as an operando and continuously online monitor for the SOC of VRFBs. Herein, we present quantitative proof-of-principle submersible EPRoC experiments on variably charged vanadium electrolyte solutions. EPR data obtained with a commercial EPR spectrometer are in good agreement with the EPRoC data.
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Affiliation(s)
- Silvio Künstner
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Joseph E McPeak
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Novo Nordisk Foundation EPR Center, Department of Chemistry, University of Copenhagen, Copenhagen, Denmark.
| | - Anh Chu
- Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Michal Kern
- Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Klaus-Peter Dinse
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Boris Naydenov
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Peter Fischer
- Fraunhofer-Institut für Chemische Technologie, Joseph-von-Fraunhofer-Straße 7, 76327 Pfinztal, Germany
| | - Jens Anders
- Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
- Center for Integrated Quantum Science and Technology (IQST), Stuttgart and Ulm, Germany
- Institute for Microelectronics Stuttgart (IMS CHIPS), Allmandring 30a, 70569 Stuttgart, Germany
| | - Klaus Lips
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
- Berlin Joint EPR Laboratory, Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
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Abhyankar N, Agrawal A, Campbell J, Maly T, Shrestha P, Szalai V. Recent advances in microresonators and supporting instrumentation for electron paramagnetic resonance spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:101101. [PMID: 36319314 PMCID: PMC9632321 DOI: 10.1063/5.0097853] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 08/13/2022] [Indexed: 06/16/2023]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy characterizes the magnetic properties of paramagnetic materials at the atomic and molecular levels. Resonators are an enabling technology of EPR spectroscopy. Microresonators, which are miniaturized versions of resonators, have advanced inductive-detection EPR spectroscopy of mass-limited samples. Here, we provide our perspective of the benefits and challenges associated with microresonator use for EPR spectroscopy. To begin, we classify the application space for microresonators and present the conceptual foundation for analysis of resonator sensitivity. We summarize previous work and provide insight into the design and fabrication of microresonators as well as detail the requirements and challenges that arise in incorporating microresonators into EPR spectrometer systems. Finally, we provide our perspective on current challenges and prospective fruitful directions.
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Affiliation(s)
| | - Amit Agrawal
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Jason Campbell
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Thorsten Maly
- Bridge12 Technologies, Inc., Natick, Massachusetts 01760, USA
| | | | - Veronika Szalai
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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