Compact Electron Paramagnetic Resonance on a Chip Spectrometer Using a Single Sided Permanent Magnet
M. Segantini1, G. Marcozzi1, T. Elrifai2, E. Shabratova1,3, K. Höflich3, M. Deaconeasa4, V. Niemann4, R. Pietig4, J.E. McPeak1, J. Anders2,5, B. Naydenov1, and Klaus Lips1,6
Published in:
ACS Sens., vol. 9, no. 10, pp. 5099-5108, doi:10.1021/acssensors.4c00788 (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.
1 Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 14109 Berlin, Germany
2 Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
3 Ferdinand-Braun-Institut gGmbH, Leibniz-Institut für Höchstfrequenztechnik, 12489 Berlin, Germany
4 Bruker BioSpin GmbH, 76275 Ettlingen, Germany
5 Center for Integrated Quantum Science and Technology, 70569 Stuttgart and Ulm, Germany
6 Berlin Joint EPR Laboratory, Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
Keywords:
EPR, EPRoC, single side permanent magnet, spin counting, in situ, in vivo, operando, molecular tumbling
© 2024 The Authors. Published by American Chemical Society
This publication is licensed under CC-BY 4.0.
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