Instituto Federal de São Paulo - Câmpus Itapetininga, 18202-000 Itapetininga, SP, Brazil.
Departamento de Física, Universidade Federal de São Carlos, P.O. Box 676, CEP 13565-905 São Carlos, São Paulo, Brazil.
J Colloid Interface Sci. 2017 Nov 1;505:454-459. doi: 10.1016/j.jcis.2017.06.024. Epub 2017 Jun 9.
Effective heterostructures for photocatalysis need to present good electron-hole mobility among phases, a feature that is only attained with satisfactory interface quality. For very small sizes and with a stable colloidal state, the oriented attachment mechanism can be used to prepare suitable structures by means of a building blocks strategy, whereby preformed nanoparticles are used to control the desired amount of each phase in the heterostructure. Here, we show the success of this strategy for anatase TiO/rutile SnO heterostructures, applying conventional hydrothermal annealing, where successive collisions among particles increase the probability of oriented attachment. The photodegradation of Rhodamine B in water under UV radiation was used as a probe reaction to evaluate formation of the heterostructure, as indicated by an increase in photoactivity. Increased heterostructure photoactivity was related to heterojunction formation and charge separation. The increased lifetimes of the photogenerated charges, due to heterojunction formation, enabled them to reach the oxides surface and promote photocatalytic reactions. The insights presented here may be used in a rationalized synthesis method to obtain heterostructures from preformed nanocrystals.
对于光催化而言，有效的异质结构需要在各相之间表现出良好的载流子迁移率，而这一特性只有在界面质量令人满意的情况下才能实现。对于非常小的尺寸和稳定的胶体状态，可以采用取向附生机制，通过构建块策略来制备合适的结构，即在该策略中使用预先形成的纳米颗粒来控制异质结构中各相的所需量。在这里，我们通过常规水热退火展示了该策略在锐钛矿 TiO/金红石 SnO 异质结构中的成功应用，其中颗粒之间的连续碰撞增加了取向附生的可能性。罗丹明 B 在水中的光降解被用作探针反应来评估异质结构的形成，这表明光催化活性有所提高。由于形成了异质结，增加了异质结构的光催化活性，从而实现了载流子的分离。光生载流子寿命的增加归因于异质结的形成，使得它们能够到达氧化物表面并促进光催化反应。本文提出的这些见解可用于合理的合成方法，从预先形成的纳米晶体中获得异质结构。
