Electron Spin Resonance Spectroscopy of Organic Radicals

Gerson, Fabian; Huber, Walter

doi:10.1002/3527601627

Cited by 288 publications

(367 citation statements)

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“…As the signal to be detected is very weak, a phasesensitive detector system, a low-pass filter and an amplifier are needed to complete the spectrometer (Figure 32). The reader can find a detailed description of EPR instrumentation in general EPR textbooks (e.g., Pilbrow, 1990;Poole, 1996;Weil et al, 1994;Gerson and Huber, 2003) and some EPR dating reviews (Jonas, 1997;Pilbrow, 1997).…”

Section: Introductionmentioning

confidence: 99%

EPR dosimetry with tooth enamel: A review

Fattibene

Callens

2010

Applied Radiation and Isotopes

203

160

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When tooth enamel is exposed to ionizing radiation, radicals are formed that can be detected using Electron Paramagnetic Resonance (EPR) techniques. EPR dosimetry using tooth enamel is based on the (presumed) correlation between the intensity or amplitude of some of the radiation-induced signals with the dose absorbed in the enamel. In the present paper a critical review is given of this widely applied dosimetric method.The first part of the paper is quite fundamental and deals with the main properties of tooth enamel and several of its model systems (e.g., synthetic apatites). Considerable attention is also devoted to the numerous radiation-induced and native EPR signals, and the radicals responsible for them. The relevant EPR detection, identification and spectrum analysing methods are reviewed from a general point of view. Finally, the need for solid state modelling and the linearity of the dose response are investigated.The second part is devoted to the practical implementation of EPR dosimetry using enamel. It concerns the preparation of samples, specific irradiation problems, spectrum acquisition and it is described how the dosimetric signal intensity and dose can be retrieved from the EPR spectra. Special attention is paid to the energy dependence of the EPR response and to sources of uncertainties. Results of and problems encountered in international intercomparisons and epidemiological studies are also dealt with.In the final chapter the future of EPR dosimetry with tooth enamel is analysed.

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Section: Introductionmentioning

confidence: 99%

EPR dosimetry with tooth enamel: A review

Fattibene

Callens

2010

Applied Radiation and Isotopes

203

160

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“…An absolute requirement is that the 2 radicals, between them, have at least 1 hyperfine interaction, i.e., an intraradical coupling between the magnetic moment of the unpaired electron and the magnetic moment of an atomic nucleus such as 1 H or 14 N. Almost all biologically occurring radicals have several potentially suitable hyperfine interactions. Ample data on hyperfine tensors is available from electron paramagnetic resonance (EPR) spectroscopy (40,41) and ab initio density functional calculations (42).…”

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confidence: 99%

Chemical magnetoreception in birds: The radical pair mechanism

Rodgers

Hore²

2009

Proc. Natl. Acad. Sci. U.S.A.

466

449

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Migratory birds travel vast distances each year, finding their way by various means, including a remarkable ability to perceive the Earth's magnetic field. Although it has been known for 40 years that birds possess a magnetic compass, avian magnetoreception is poorly understood at all levels from the primary biophysical detection events, signal transduction pathways and neurophysiology, to the processing of information in the brain. It has been proposed that the primary detector is a specialized ocular photoreceptor that plays host to magnetically sensitive photochemical reactions having radical pairs as fleeting intermediates. Here, we present a physical chemist's perspective on the ''radical pair mechanism'' of compass magnetoreception in birds. We outline the essential chemical requirements for detecting the direction of an Earth-strength Ϸ50 T magnetic field and comment on the likelihood that these might be satisfied in a biologically plausible receptor. Our survey concludes with a discussion of cryptochrome, the photoactive protein that has been put forward as the magnetoreceptor molecule.

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“…7 reveal proton hfc's around 25 MHz, a value comparable to those found for conjugated aliphatic radicals. 40 The detailed analysis of the cross-peak line shape and intensity is beyond the scope of this article, and will be presented elsewhere. Similar to the analysis reported 41 on hydrogen absorption in ball milled graphite, if we assume the ESR signals to result from π radicals, then we can use the proton hfc's to estimate the electron spin density ρ π at the adjacent carbon atoms by means of the McConnell equation, 42 a H (α) = Q H ρ π , where Q H ∼ 2.7 mT is an intrinsic coupling value for unit density and a H (α) is the proton hyperfine coupling in mT.…”

Section: Resultsmentioning

confidence: 99%

Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

et al. 2014

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Electronic spin transport properties of graphene nanoribbons (GNRs) are influenced by the presence of adatoms, adsorbates and edge functionalization. To improve the understanding of the factors that influence the spin properties of GNRs, local (element) spin-sensitive techniques such as electron spin resonance (ESR) spectroscopy are important for spintronics applications. Here, we present results of multi-frequency continuous wave (CW), pulse and hyperfine sublevel correlation (HYSCORE) ESR spectroscopy measurements performed on oxidatively unzipped graphene nanoribbons (GNRs), which were subsequently chemically converted (CCGNRs) with hydrazine. ESR spectra at 336 GHz reveal an isotropic ESR signal from the CCGNRs, of which the temperature dependence of its line width indicates the presence of localized unpaired electronic states. Upon functionalization of CCGNRs with 4-nitrobenzene diazonium tetrafluoroborate, the ESR signal is found to be 2 times narrower than that of pristine ribbons. NH3 adsorption/desorption on CCGNRs is shown to narrow the signal, while retaining the signal intensity and g value. The electron spin-spin relaxation process at 10 K is found to be characterized by slow (163 ns) and fast (39 ns) components. HYSCORE ESR data demonstrate the explicit presence of protons and 13C atoms. With the provided identification of intrinsic point magnetic defects such as proton and 13C has been reported, which are roadblocks to spin travel in graphene-based materials, this work could help in advancing the present fundamental understanding on the edge-spin (or magnetic)-based transport properties of CCGNRs.

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Electron Spin Resonance Spectroscopy of Organic Radicals

Cited by 288 publications

References 0 publications

EPR dosimetry with tooth enamel: A review

EPR dosimetry with tooth enamel: A review

Chemical magnetoreception in birds: The radical pair mechanism

Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

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