Study of paramagnetic defect centers in as-grown and annealed TiO(2) anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR.
Study of paramagnetic defect centers in as-grown and annealed TiO(2) anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR.
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DOI：
10.1016/j.jmmm.2015.10.072
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发表时间：
2016-03-01
影响因子：
2.7
通讯作者：
Prakash O
中科院分区：
文献类型：
--
作者：
Misra SK;Andronenko SI;Tipikin D;Freed JH;Somani V;Prakash O
在X波段（9.6 GHz）77、120-300 K和236 GHz 292 K下对生长和退火的金红石相和金红石相TiO 2纳米颗粒进行了详细的EPR研究。对生长态和退火态金红石和金红石样品的EPR数据分析表明，存在几个顺磁中心：Ti 3+、O−、吸附氧（O2−）和氧空位。另一方面，在生长态金红石样品中，观察到由于两个Ti 4+替代位置上的吸附氧（O2-）和Fe 3+离子而产生的EPR线，无论是否与附近的氧空位耦合。当在1000° C下退火时，锐钛矿纳米颗粒完全转化为金红石相，表现出与生长态金红石纳米颗粒所表现出的EPR谱相似的EPR谱。在g = 2.0的区域记录的金红石和金红石样品的高频（236 GHz）EPR数据显示出分辨的EPR谱线，这是由于O−和O2−离子使得能够以更高的精度确定它们的g值，以及由于Mn 2+和Mn 4+离子在金红石中观察到的超精细六重态。
Detailed EPR investigations on as-grown and annealed TiO2 nanoparticles in the anatase and rutile phases were carried out at X-band (9.6 GHz) at 77, 120–300 K and at 236 GHz at 292 K. The analysis of EPR data for as-grown and annealed anatase and rutile samples revealed the presence of several paramagnetic centers: Ti3+, O−, adsorbed oxygen (O2−) and oxygen vacancies. On the other hand, in as-grown rutile samples, there were observed EPR lines due to adsorbed oxygen (O2−) and the Fe3+ ions in both Ti4+ substitutional positions, with and without coupling to an oxygen vacancy in the near neighborhood. Anatase nanoparticles were completely converted to rutile phase when annealed at 1000° C, exhibiting EPR spectra similar to those exhibited by the as-grown rutile nanoparticles. The high-frequency (236 GHz) EPR data on anatase and rutile samples, recorded in the region about g = 2.0 exhibit resolved EPR lines, due to O− and O2− ions enabling determination of their g-values with higher precision, as well as observation of hyperfine sextets due to Mn2+ and Mn4+ ions in anatase.