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首页> 外文期刊>Chemistry: A European journal >Non-UV-Induced Radical Reactions at the Surface of TiO2 Nanoparticles That May Trigger Toxic Responses
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Non-UV-Induced Radical Reactions at the Surface of TiO2 Nanoparticles That May Trigger Toxic Responses

机译：TiO2纳米颗粒表面的非紫外线诱导自由基反应可能会触发毒性反应

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Titania is generally considered to be an inert and safe material. Several studies, however, have reported that nanosized TiO2 may elicit toxic effects. In some cases the observed adverse effects have been related to free radicals. Although new studies mainly concern irradiated titania, the role and the mechanisms of the generation of free radicals by TiO2 in the absence of UV irradiation are not well known. The purpose of the present study is to investigate the free-radical-generation mechanisms by nano- and micronsized anatase or rutile powders under normal laboratory illumination or in the dark by means of a spin-trapping/ESR spectroscopy technique. This technique is used to identify the nature and the amount of free radicals released in solution, and in the solid-state to characterise the paramagnetic centres at the surface of particles that may participate in the reactions. The following radical-generating mechanisms have been considered: 1) the generation of oxygenated free radicals (HO2 center dot, O-2(center dot-), HO center dot) following the reaction of TiO2 with oxygen, water or H2O2 and 2) the generation of carbon-centred radicals following the cleavage of the C-H bond in a model molecule. Although no free radicals were detected in a simply buffered solution, anatase and rutile generated O-2(center dot-) and HO center dot, respectively, in the presence of H2O2. Both polymorphs were also active in the cleavage of the C-H bond. Although the formation of O-2(center dot-) appears to be related to exposure to sunlight, the generation of HO center dot and carbon-centred free radicals also occurs in the dark. When samples of equal surface area were tested, micron- and nanosized anatase was found to react in the same way indicating that a reduction in diameter does not generate new kinds of reactive sites. The data presented herein may have implications in the assessment of the health risk associated with the exposure to TiO2 nanoparticles and in the ecotoxicological impact following their possible leakage into the environment.
机译：二氧化钛通常被认为是一种惰性和安全的材料。但是，几项研究报告说，纳米TiO2可能引起毒性作用。在某些情况下，观察到的不利影响与自由基有关。尽管新的研究主要涉及辐照的二氧化钛，但在没有紫外线辐照的情况下，TiO2产生自由基的作用和机理尚不清楚。本研究的目的是通过自旋捕集/ ESR光谱技术研究纳米和微米级锐钛矿或金红石粉在正常实验室照明下或在黑暗中的自由基生成机理。该技术用于确定溶液中释放的自由基的性质和数量，并用于固态状态以表征可能参与反应的颗粒表面的顺磁中心。已经考虑了以下自由基产生机理：1）在TiO2与氧气，水或H2O2反应后产生氧化自由基（HO2中心点，O-2（中心点-），HO中心点）和2）在模型分子中CH键断裂后碳中心自由基的产生。尽管在简单的缓冲溶液中未检测到自由基，但在H2O2存在下，锐钛矿和金红石分别生成O-2（中心点）和HO中心点。两种多晶型物在C-H键的裂解中也具有活性。尽管O-2（中心点）的形成似乎与日光照射有关，但HO中心点和以碳为中心的自由基的产生也在黑暗中发生。当测试表面积相等的样品时，发现微米和纳米锐钛矿以相同的方式反应，表明直径减小不会产生新的反应部位。本文提供的数据可能对评估与TiO2纳米颗粒的暴露相关的健康风险以及可能泄漏到环境中的生态毒理学影响具有影响。

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