Compact Electron Paramagnetic Resonance on a Chip Spectrometer Using a Single Sided Permanent Magnet.

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 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.

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

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 field produced by the VCOs must be known.

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

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 VO/VO and V/V, the ratio of which to the total vanadium content determines the state of charge (SOC).

Long-Term Characterization of Oxidation Processes in Graphitic Carbon Nitride Photocatalyst Materials via Electron Paramagnetic Resonance Spectroscopy.

Graphitic carbon nitride (gCN) materials have been shown to efficiently perform light-induced water splitting, carbon dioxide reduction, and environmental remediation in a cost-effective way. However, gCN suffers from rapid charge-carrier recombination, inefficient light absorption, and poor long-term stability which greatly hinders photocatalytic performance. To determine the underlying catalytic mechanisms and overall contributions that will improve performance, the electronic structure of gCN materials has been investigated using electron paramagnetic resonance (EPR) spectroscopy.

Rapid-scan electron paramagnetic resonance using an EPR-on-a-Chip sensor.

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, novel aspects of voltage-controlled oscillator (VCO)-based EPR-on-a-Chip (EPRoC) detectors are discussed, which have recently gained interest in the EPR community.

Electron paramagnetic resonance of lanthanides.

Many applications of lanthanides exploit their electron spin relaxation properties. Double electron-electron measurements of distances are possible because of the relatively long relaxation times of Gd. Relaxation enhancement measurements of distance are possible because of the much shorter relaxation times of other lanthanides.

EPR Everywhere.

This review is inspired by the contributions from the University of Denver group to low-field EPR, in honor of Professor Gareth Eaton's 80th birthday. The goal is to capture the spirit of innovation behind the body of work, especially as it pertains to development of new EPR techniques. The spirit of the DU EPR laboratory is one that never sought to limit what an EPR experiment could be, or how it could be applied.

Rapid-Scan Electron Paramagnetic Resonance of Highly Resolved Hyperfine Lines in Organic Radicals.

X-band (ca. 9 GHz) fluid solution rapid-scan electron paramagnetic resonance spectra are reported for radicals with multiline spectra and resolution of hyperfine lines as narrow as 30 mG. Highly-resolved spectra of 3-carbamoyl-2,2,5,5-tetramethylpyrrolidin-1-yloxy, diphenylnitroxide, galvinoxyl, and perylene cation radical with excellent signal-to-noise are shown, demonstrating the capabilities of the rapid-scan technique to characterize very small, well-resolved hyperfine couplings.

C isotope enrichment of the central trityl carbon decreases fluid solution electron spin relaxation times.

Electron spin relaxation times for perdeuterated Finland trityl 99% enriched in C at the central carbon (C-dFT) were measured in phosphate buffered saline (pH = 7.2) (PBS) solution at X-band. The anisotropic C hyperfine (A = A = 18 ± 2, A = 162 ± 1 MHz) and g values (2.

An x-band continuous wave saturation recovery electron paramagnetic resonance spectrometer based on an arbitrary waveform generator.

An X-band (ca. 9-10 GHz) continuous wave saturation recovery spectrometer to measure electron spin-lattice relaxation (T) was designed around an arbitrary waveform generator (AWG). The AWG is the microwave source and is used for timing of microwave pulses, generation of control signals, and digitizer triggering.

Mechanism of SmI Reduction of 5-Bromo-6-oxo-6-phenylhexyl Methanesulfonate Studied by Spin Trapping with 2-Methyl-2-nitrosopropane.

The radical formed by reduction of 5-bromo-6-oxo-6-phenylhexyl methanesulfonate, an α-bromoketone, with SmI was spin trapped with 2-methyl-2-nitrosopropane. Electron paramagnetic resonance spectra of the spin adduct and the adduct formed in the analogous reaction with selectively deuterated substrate identify the radical intermediate in this SmI reduction as a carbon-centered radical. This result supports the proposal that the formation of reactive Sm-enolates arises from reduction of the carbon-bromine bond rather than a ketyl radical anion.