Reversible ESR linebroadening in thin films of alkali-DCNQI radical ion salts by oxygen

Abstract

Thin films of 2,5-dimethyl-NN'-dicyanoquinonediimine (DMe-DCNQI) with alkaline counter ions can be used as contactless sensors for spin-carrying gases, e.g. oxygen or NO. In the title compound, the linewidth of the electron spin resonance signal is a linear function of the partial pressure of oxygen. The sensitivity is in the order of 10-10 mol. O2. The films are 100 nm thick and show typical response times which are faster than tau =100 ms, the time constant of the ESR apparatus used. Because of the sensitivity, the constants of diffusion of gases through layers of coatings can be measured even at macroscopic thicknesses.

ESR Broadening in Conducting Polypyrrole Because of Oxygen: Application to the Study of Oxygen Adsorption

“…ESR spectroscopy is one of the most powerful approaches for obtaining microscopic information on paramagnetic compounds, and it has been actually employed for examining the interactions between electron spins of molecular oxygen and paramagnetic materials 3,[5][6][7][8][9][10][11][12][13][14][15] including PPy. 3,[9][10][11] In the researches, special attention has been paid to the ESR line width, which is usually broadened by the presence of molecular oxygen.…”

“…ESR spectroscopy is one of the most powerful approaches for obtaining microscopic information on paramagnetic compounds, and it has been actually employed for examining the interactions between electron spins of molecular oxygen and paramagnetic materials ,− including PPy. ,− In the researches, special attention has been paid to the ESR line width, which is usually broadened by the presence of molecular oxygen. It should be particularly emphasized because of the contribution of the researches that elucidation of such a broadening effect due to molecular oxygen not only is of importance to clarify the influence of oxygen on the paramagnetic materials but also is available for an estimate of the polaron mobility 12,15 and for a spin-label oximetry.…”

ESR in conducting polymers: Oxygen-induced contribution to the linewidth

“…As examples we mention ͑i͒ free radicals in solution: the resolution of the hyperfine structure is lost if the solution has not been properly degassed, 4,5 ͑ii͒ phtalocyanine radicals such as lithium phtalocyanine, [6][7][8][9][10][11] ͑iii͒ alkali-DCNQI radical ion salts, 12 and ͑iv͒ amorphous silicon. 13 We also mention the effect of oxygen in polyacetylene, which is only partly reversible.…”

N,N‘-Dicyanoquinone Diimines (DCNQIs): Versatile Acceptors for Organic Conductors

“…Thorough spectroscopical investigations are reported for films of DMe-DCNQI on surfaces of Ag(111), Ag (100) and Cu(111), Cu(110). ,,− The same protocol was applied to surfaces of alkali metals, freshly prepared on an inert support. ,,,, In all cases, highly structured films are obtained, variable by the conditions applied, including annealing, which may produce the corresponding anion radical metal salts in highly ordered arrangements. Strong pressure dependence of conductivity and oxygen adsorption 192 of such [DMe-DCNQI] 2 Cu layers on copper may be of practical importance.…”

“…378 For STM, materials containing DCNQI type metal salts are described as media for electron density memories. 379 Various sensors have been designed as follows: (i) thin films of DCNQI type alkali salts for the contactless determination of spin-carrying gases, e.g., O 2 and NO; 228 (ii) DCNQI type copper salts on the surface of conducting SnO 2 as a sensor for hydrogen; 192,380 and (iii) pressure sensors from DCNQI type films. 192…”