Abu Bakar Nur I, Chandren Sheela, Attan Nursyafreena, Leaw Wai L, Nur Hadi
Centre for Sustainable Nanomaterials, Ibnu Sina Institute for Scientific and Industrial Research, Universiti Teknologi Malaysia, Johor, Malaysia.
Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, Johor, Malaysia.
Front Chem. 2018 Sep 11;6:370. doi: 10.3389/fchem.2018.00370. eCollection 2018.
The demonstration of the structure-properties relationship of shape-dependent photocatalysts remains a challenge today. Herein, one-dimensional (1-D)-like titania (TiO), as a model photocatalyst, has been synthesized under a strong magnetic field in the presence of a magnetically responsive liquid crystal as the structure-aligning agent to demonstrate the relationship between a well-aligned structure and its photocatalytic properties. The importance of the 1-D-like TiO and its relationship with the electronic structures that affect the electron-hole recombination and the photocatalytic activity need to be clarified. The synthesis of 1-D-like TiO with liquid crystal as the structure-aligning agent was carried out using the sol-gel method under a magnetic field (0.3 T). The mixture of liquid crystal, 4'-pentyl-4-biphenylcarbonitrile (5CB), tetra--butyl orthotitanate (TBOT), 2-propanol, and water, was subjected to slow hydrolysis under a magnetic field. The TiO-5CB took a well-aligned whiskerlike shape when the reaction mixture was placed under the magnetic field, while irregularly shaped TiO-5CB particles were formed when no magnetic field was applied. It shows that the strong interaction between 5CB and TBOT during the hydrolysis process under a magnetic field controls the shape of titania. The intensity of the emission peaks in the photoluminescence spectrum of 1-D-like TiO-5CB was lowered compared with the TiO-5CB synthesized without the magnetic field, suggesting the occurrence of electron transfer from 5CB to the 1-D-like TiO-5CB during ultraviolet irradiation. Apart from that, direct current electrical conductivity and Hall effect studies showed that the 1-D-like TiO composite enhanced electron mobility. Thus, the recombination of electrons and holes was delayed due to the increase in electron mobility; hence, the photocatalytic activity of the 1-D-like TiO composite in the oxidation of styrene in the presence of aqueous hydrogen peroxide under UV irradiation was enhanced. This suggests that the 1-D-like shape of TiO composite plays an important role in its photocatalytic activity.
如今，证明形状依赖型光催化剂的结构-性能关系仍是一项挑战。在此，一维（1-D）状二氧化钛（TiO）作为一种模型光催化剂，已在强磁场下，以磁响应液晶作为结构排列剂合成，以证明良好排列的结构与其光催化性能之间的关系。需要阐明一维状TiO的重要性及其与影响电子-空穴复合和光催化活性的电子结构之间的关系。以液晶作为结构排列剂合成一维状TiO是在磁场（0.3 T）下采用溶胶-凝胶法进行的。将液晶、4'-戊基-4-联苯甲腈（5CB）、四丁氧基钛（TBOT）、2-丙醇和水的混合物在磁场下进行缓慢水解。当反应混合物置于磁场中时，TiO-5CB呈现出排列良好的晶须状，而在不施加磁场时则形成形状不规则的TiO-5CB颗粒。这表明在磁场下水解过程中5CB与TBOT之间的强相互作用控制了二氧化钛的形状。与无磁场合成的TiO-5CB相比，一维状TiO-5CB的光致发光光谱中发射峰的强度降低，这表明在紫外照射期间发生了从5CB到一维状TiO-5CB的电子转移。除此之外，直流电导率和霍尔效应研究表明一维状TiO复合材料提高了电子迁移率。因此，由于电子迁移率的增加，电子与空穴的复合被延迟；因此，在紫外照射下，一维状TiO复合材料在过氧化氢水溶液存在下氧化苯乙烯的光催化活性增强。这表明TiO复合材料的一维状形状在其光催化活性中起重要作用。
