Live demonstration: A VCO-based point-of-care ESR spectrometer

Schlecker, Benedikt; Chu, A.; Handwerker, Jonas; Künstner, Silvio; Ortmanns, Maurits; Lips, K.; Anders, Jens

doi:10.1109/icsens.2017.8234031

Cited by 4 publications

(2 citation statements)

References 2 publications

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“…Importantly, this approach breaks the classical trade-off between the resonator and detection sensitivity (Hyde et al, 2010), 60 enabling frequency-swept EPR over wide frequency ranges with near-constant sensitivity. This allows the use of permanent magnets for smaller, more affordable, battery-driven spectrometers, as recently demonstrated (Schlecker et al, 2017a, b;Anders and Lips, 2019). The magnetic field strengths of practical permanent magnets (<1.5 T) limit the EPR resonance frequency to below 35 GHz; however, EPRoC detectors are much easier to integrate into complex and application-specific sample environments, opening the door to numerous potential in situ and/or operando EPR applications from room temperature 65 to cryogenic temperatures down to 4 K (Gualco et al, 2014).…”

Section: Discussion Open Accessmentioning

confidence: 93%

Rapid Scan Electron Paramagnetic Resonance using an EPR-on-a-Chip Sensor

Künstner¹,

Chu²,

Dinse³

et al. 2021

Preprint

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Abstract. Electron paramagnetic resonance (EPR) spectroscopy is the method of choice to investigate and quantify paramagnetic species in many scientific fields, including materials science and the life sciences. Common EPR spectrometers use electromagnets and microwave (MW) resonators, limiting their application to dedicated lab environments. Here, we present an improved design of a miniaturized EPR spectrometer implemented on a silicon microchip (EPR-on-a-chip, EPRoC). In place of a microwave resonator, EPRoC uses an array of injection-locked voltage-controlled oscillators (VCOs), each incorporating a 200 µm diameter coil, as a combined microwave source and detector. The individual miniaturized VCO elements provide an excellent spin sensitivity reported to be about 4 × 109 spins/√Hz, which is extended by the array over a larger area for improved concentration sensitivity. A striking advantage of this design is the possibility to sweep the MW frequency instead of the magnetic field, which allows the use of smaller, permanent magnets instead of the bulky and power-hungry electromagnets required for field-swept EPR. Here, we report rapid scan EPR (RS-EPRoC) experiments performed by sweeping the frequency of the EPRoC VCO array. RS-EPRoC spectra demonstrate an improved SNR by approximately two orders of magnitude for similar signal acquisition times compared to continuous wave (CW-EPRoC) methods, which may improve the absolute spin and concentration sensitivity of EPR-on-a-Chip at 14 GHz to about 6 × 107 spins/√Hz and 3.6 nM/√Hz, respectively.

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Section: Discussion Open Accessmentioning

confidence: 93%

Rapid Scan Electron Paramagnetic Resonance using an EPR-on-a-Chip Sensor

Künstner¹,

Chu²,

Dinse³

et al. 2021

Preprint

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“…This allows the use of permanent magnets for smaller, cost-effective, battery-driven spectrometers, as recently demonstrated. 38,[42][43][44] Building on the success of VCO-based EPR spectrometers, we herein present proof-of-principle quantitative EPRoC fluid-submersible ''dipstick'' experiments on V electrolyte solutions with different SOCs still using an electromagnet, which are then compared with spectra obtained using a commercial resonator-based EPR spectrometer. The quantitation of the data obtained with the EPRoC and with the commercial EPR spectrometer yields similar results showing the possibility to utilise EPRoC as an online SOC monitoring sensor for VRFBs.…”

Section: Introductionmentioning

confidence: 99%

Monitoring the state of charge of vanadium redox flow batteries with an EPR-on-a-Chip dipstick sensor

Künstner,

McPeak,

Chu

et al. 2024

Phys. Chem. Chem. Phys.

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Microwave field mapping for EPR-on-a-chip experiments

Künstner,

McPeak,

Chu

et al. 2024

Sci. Adv.

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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 B 1 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 B 1 -field intensity. The EPRoC array sensitive volume was determined to be ~19 nanoliters. Implications for possible EPR applications are discussed.

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Live demonstration: A VCO-based point-of-care ESR spectrometer

Cited by 4 publications

References 2 publications

Rapid Scan Electron Paramagnetic Resonance using an EPR-on-a-Chip Sensor

Rapid Scan Electron Paramagnetic Resonance using an EPR-on-a-Chip Sensor

Monitoring the state of charge of vanadium redox flow batteries with an EPR-on-a-Chip dipstick sensor

Microwave field mapping for EPR-on-a-chip experiments

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