洞察ZnO缺陷对ZnO / SiO2系统中环境持久性自由基催化生成的影响,The Journal of Physical Chemistry C

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洞察ZnO缺陷对ZnO / SiO2系统中环境持久性自由基催化生成的影响
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2019-08-22 , DOI: 10.1021/acs.jpcc.9b06900
Massimiliano D’Arienzo , Silvia Mostoni , Roberta Crapanzano , Cinzia Cepek ₁ , Barbara Di Credico , Mauro Fasoli , Stefano Polizzi ₂ , Anna Vedda , Irene Villa , Roberto Scotti

Affiliation

本研究旨在通过探索具有不同内在缺陷生长的ZnO纳米颗粒（NPs）的性质，提供有关ZnO / SiO ₂系统上苯酚（PhOH）产生环境持久性自由基（EPFRs）的更深入的图像。球形（ZnO / SiO ₂ _S）和蠕虫状（ZnO / SiO ₂ _W）的高孔隙度二氧化硅上的合成。详细地，除了进行了广泛的结构，形态和表面研究外，还通过光致发光（PL）实验跟踪了样品中不等价缺陷中心的发生，该实验揭示了ZnO / SiO ₂ _W强烈的蓝色发射，可能涉及来自Zn _i激发到价带或V的能级_锌水平。电子自旋共振（ESR）光谱证实了这些结果，并揭示了样品在EPFR形成模型反应中的行为明显不同。实际上，在PhOH接触后，ZnO / SiO ₂ _S的ESR谱显示出仅存在归因于PhenO ^• EPFR的弱的各向同性信号。相反，氧化锌/二氧化硅₂ _W，与氧物种以V的接近相关联的强烈特征_Ò⁺，V_锌^-，和（V_锌^-）₂^-中心主导光谱，而苯氧的次要贡献^•自由基只能通过信号模拟来发现。这些结果明确地设想的ZnO纳米粒子的固有缺陷的上EPFR产生的最终产率和稳定性的作用，采用V _ö⁺和V_锌^-可能参与在氧化物表面解离吸附或氧化工艺的缺陷。尽管这项工作集中在ZnO上，但有望在文献中已经报道的其他金属氧化物/二氧化硅体系上进行重要的重新检验和重要结果的整合，从而为更好地评估EPFR生成对氧化物缺陷的依赖性提供了机会。化学。

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Insight into the Influence of ZnO Defectivity on the Catalytic Generation of Environmentally Persistent Free Radicals in ZnO/SiO2 Systems

The present study aims at supplying a more in-depth picture of the generation of environmentally persistent free radicals (EPFRs) from phenol (PhOH) on ZnO/SiO₂ systems, by exploring the properties of ZnO nanoparticles (NPs) with different intrinsic defectivity grown on highly porous silica with a spherical (ZnO/SiO₂_S) and wormlike morphology (ZnO/SiO₂_W). In detail, besides an extensive structural, morphological, and surface investigation, the occurrence of inequivalent defect centers in the samples was tracked by photoluminescence (PL) experiments, which unveiled, for ZnO/SiO₂_W, intense blue emissions possibly involving radiative recombination from Zn_i excited levels to the valence band or to V_Zn levels. Electron spin resonance (ESR) spectra corroborated these results and revealed a remarkably different behavior of the samples in the EPFR formation model reaction. In fact, upon PhOH contact, the ESR spectrum of ZnO/SiO₂_S showed the exclusive presence of a weak isotropic signal ascribable to a PhenO^• EPFR. Instead, for ZnO/SiO₂_W, intense features associated with oxygen species in proximity of V_O⁺, V_Zn^–, and (V_Zn^–)₂^– centers dominate the spectra, while a minor contribution of the PhenO^• radical can be discovered only by signal simulation. These outcomes definitively envisage a role of the intrinsic defectivity of ZnO NPs on the final yield and stability of EPFR generation, with V_O⁺ and V_Zn^– defects possibly involved in dissociative adsorption or oxidation processes at the oxide surface. Although this work focuses on ZnO, it is expected to foster a critical re-examination and integration of important results on other metal oxide/silica systems already reported in the literature, offering the chance to better evaluate the dependence of EPFR generation on the oxide defects chemistry.

更新日期：2019-08-23

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