Üner Deniz, Yarar Melis
Chemical Engineering Department, Middle East Technical University, Ankara, Turkey.
Turk J Chem. 2022 Mar 12;46(4):1081-1088. doi: 10.55730/1300-0527.3416. eCollection 2022.
A low field benchtop electron spin resonance (ESR) (also referred to as electron paramagnetic resonance (EPR)) spectrometer is used to reveal paramagnetic centres such as oxygen vacancies and Ti centres over 0.5%Pd/TiO. The measurement was performed at room temperature after the sample was reduced under mild hydrogen pressures and evacuated to P < 10 Torr. The measurement was possible due to a T compensation effect under vacuum: Correlation times at low pressures enabled sufficient line narrowing and detection of the ESR signal, justifying a method using benchtop spectrometers coupled to vacuum manifolds. The method justification was demonstrated using similar measurements performed on a reference compound, Mn(II) in plasticine: a measurement performed by saturation recovery technique revealed that T of the signal due to Mn(II) was smaller in vacuum than its atmosphere exposed counterpart. By applying vacuum, the ESR spectra of 0.5%Pd/TiO were collected at ambient temperatures, with features equivalent to the published data obtained at cryogenic temperatures.
一台低场台式电子自旋共振（ESR）（也称为电子顺磁共振（EPR））光谱仪用于揭示诸如0.5%Pd/TiO₂ 上的氧空位和钛中心等顺磁中心。在温和氢气压力下对样品进行还原并抽真空至P < 10托后，于室温下进行测量。由于真空下的T₂ 补偿效应，该测量得以实现：低压下的相关时间使得线宽足够变窄并能检测到ESR信号，证明了使用与真空歧管相连的台式光谱仪的方法是合理的。使用在参考化合物（橡皮泥中的Mn(II)）上进行的类似测量证明了该方法的合理性：通过饱和恢复技术进行的测量表明，真空下Mn(II)产生的信号的T₂ 比暴露在大气中的对应物小。通过施加真空，在环境温度下收集了0.5%Pd/TiO₂ 的ESR光谱，其特征与在低温下获得的已发表数据相当。
