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Temperature dynamics of magnetoactive compounds under terahertz irradiation: characterization by an EPR study. Russ Chem Bull 2022. [DOI: 10.1007/s11172-022-3543-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Panarelli EG, Gast P, Groenen EJJ. Temperature-cycle electron paramagnetic resonance. Phys Chem Chem Phys 2020; 22:9487-9493. [PMID: 32314999 DOI: 10.1039/d0cp00664e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We report on a novel approach to the study of rates and short-lived intermediates of (bio)chemical reactions that involve paramagnetic species. Temperature-cycle Electron Paramagnetic Resonance (EPR) concerns the repeated heating of a reaction mixture in the cavity of an EPR spectrometer by pulsed irradiation with a near-infrared diode laser combined with intermittent characterization of the sample by 275 GHz EPR at a lower temperature at which the reaction does not proceed. The new technique is demonstrated for the reduction of TEMPOL with sodium dithionite in aqueous solution down to the sub-second time scale. We show that a single sample suffices to obtain a complete kinetic trace. Variation of the length and power of the laser pulse offers great flexibility as regards the time scale of the experiment and the temperature at which the reaction can be studied. For water/glycerol mixtures we introduce a simple way to obtain and load an unreacted sample into the spectrometer at low temperature.
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Affiliation(s)
- E Gabriele Panarelli
- Department of Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands.
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Folli A, Choi H, Barter M, Harari J, Richards E, Slocombe D, Porch A, Murphy DM. A novel dual mode X-band EPR resonator for rapid in situ microwave heating. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 310:106644. [PMID: 31812887 DOI: 10.1016/j.jmr.2019.106644] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 11/04/2019] [Accepted: 11/08/2019] [Indexed: 06/10/2023]
Abstract
A unique dual mode X-band Continuous Wave (CW) EPR resonator designed for simultaneous EPR measurement and rapid microwave (MW) induced sample heating is described. Chemical reactions subjected to a flow of energy and matter can be perturbed away from the thermodynamic equilibrium by imposing a rapid shock or physical change to the system. Depending on the magnitude of the perturbation, these changes can dictate the subsequent evolution of the entire system, allowing for instance to populate non-equilibrium reactive intermediate states. Temperature jump (T-jump) experiments are a common method to achieve such perturbations. Most T-jump experiments are based on Joule Heating methods or IR lasers. Here we demonstrate the principle of rapid sample heating based on microwaves. The benefits of MW heating include (i) rapid and efficient heating (i.e. using a tuned resonant cavity, >99% efficient power transfer to the sample can be achieved), and (ii) volumetric heating (i.e. the entire sample volume rises in temperature at once, since heat is generated in the sample instead of being transferred to it). Accordingly, the key concept of the design is the use of a cavity resonator allowing EPR detection (at 9.5 GHz) and simultaneous sample heating (at 6.1 GHz). Temperature increments of 50 °C within a few seconds are possible. This is evidenced and illustrated here by probing the temperature-induced variation of the rotational dynamics of 16-doxyl stearic acid methyl ester (16-DSE) spin probe grafted on the surface of sodium dodecyl sulphate (SDS) micelles in water, as well as copper (II) acetylacetonate in chloroform. Rapid changes in the rotational dynamics of the paramagnetic centres provide direct evidence for the in situ and simultaneous EPR measurement-heating capabilities of the resonator. Improvements afforded by the use of pulsed MW sources will enable faster heating time scales to be achieved. In the longer term, this current study demonstrates the simple and direct possibilities for using MW heating as a means of performing T-jump experiments.
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Affiliation(s)
- Andrea Folli
- School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, UK.
| | - Heungjae Choi
- School of Engineering, Cardiff University, The Parade, Cardiff CF24 3AA, UK
| | - Michael Barter
- School of Engineering, Cardiff University, The Parade, Cardiff CF24 3AA, UK
| | - Jaafar Harari
- School of Engineering, Cardiff University, The Parade, Cardiff CF24 3AA, UK
| | - Emma Richards
- School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, UK
| | - Daniel Slocombe
- School of Engineering, Cardiff University, The Parade, Cardiff CF24 3AA, UK
| | - Adrian Porch
- School of Engineering, Cardiff University, The Parade, Cardiff CF24 3AA, UK
| | - Damien M Murphy
- School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, UK
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