Parrino Francesco, Gottuso Alessandro, Viganò Lorenzo, Mariani Pietro, Villa Irene, Cova Francesca, Callone Emanuela, Dirè Sandra, Palmisano Leonardo, Stredansky Matus, D'Arienzo Massimiliano
Department of Industrial Engineering, University of Trento, Via Sommarive 9, 38123, Trento, Italy.
Department of Materials Science (INSTM), University of Milano-Bicocca, Via R. Cozzi 55, 20125, Milano, Italy.
Angew Chem Int Ed Engl. 2025 Jan 10;64(2):e202414445. doi: 10.1002/anie.202414445. Epub 2024 Nov 7.
A commercial TiO sample, used as received or hydrothermally treated to increase surface hydroxylation, has been functionalized by surface modification with hexadecyltrimethoxysilane. The anchoring of the silane has been characterized by means of FTIR and solid-state NMR spectroscopies, and the grafting density was determined by thermogravimetric and N physisorption analyses. The silane moieties induce a partial decrease of the shielding of the valence electrons of the Ti ions at the surface, and a local modification of their crystal field, as demonstrated by XPS and UV/Vis spectroscopy, respectively. The changes in coordination and the produced oxygen vacancies result in the formation of Ti defects localized in the sub-surface region, as revealed by EPR spectroscopy. These paramagnetic centers are stabilized in the silanized samples, as the electron transfer to O is efficiently inhibited even under UV irradiation. However, the amount of Ti centers appears to be correlated with the singlet oxygen (O) formation rate. Accordingly, epoxidation of limonene under UV light, chosen as a model photocatalytic reaction triggered by O, occurred with higher selectivity when TiO was silanized and upon simultaneous NIR irradiation. These evidences suggest that in the silanized sample O may be generated through Förster-type energy transfer from excited sub-surface Ti centers.
一种商用TiO样品，按原样使用或经过水热处理以增加表面羟基化，已通过用十六烷基三甲氧基硅烷进行表面改性实现功能化。通过傅里叶变换红外光谱（FTIR）和固态核磁共振光谱对硅烷的锚固进行了表征，并通过热重分析和N物理吸附分析确定了接枝密度。分别通过X射线光电子能谱（XPS）和紫外可见光谱（UV/Vis）证明，硅烷部分导致表面Ti离子价电子屏蔽的部分降低及其晶体场的局部改变。电子顺磁共振光谱（EPR）表明，配位变化和产生的氧空位导致在次表面区域形成局部化的Ti缺陷。这些顺磁中心在硅烷化样品中得以稳定，因为即使在紫外线照射下，电子向O的转移也能被有效抑制。然而，Ti中心的数量似乎与单线态氧（O）的形成速率相关。因此，在紫外光下，选择柠檬烯的环氧化作为由O引发的模型光催化反应，当TiO硅烷化并同时进行近红外辐射时，反应具有更高的选择性。这些证据表明，在硅烷化样品中，O可能通过从激发的次表面Ti中心进行的福斯特型能量转移产生。
