Minella Marco, Minero Claudio
Department of Chemistry and NIS Center of Excellence, University of Torino, Via P. Giuria 5, 10125 Torino, Italy.
Materials (Basel). 2019 Feb 8;12(3):508. doi: 10.3390/ma12030508.
The photo-induced reactivity of compounds at the surface of photocatalytic materials is used to maintain the cleanliness of the surface of glass, concretes and paints. A standard method to quantify the photocatalytic self-cleaning (SC) properties of non-transparent materials was recently published. It is based on the covering of the sample surface with a defined amount of dye and on the evaluation of the reflectance spectra of the coloured surface under irradiation. The calibration of the spectral changes allowed the quantification of the surface residual dye and the evaluation of the self-cleaning kinetics. The method was tested on seven white and coloured photocatalytic materials using methylene blue (MB), rhodamine B (RhB) and metanil yellow (MY). The main by-products of the MB photocatalytic degradation at the solid/solid interface were identified, showing that MB degradation in solution follows a path quite different from that at the solid/solid interface. Also MY showed a different order of photoreactivity. Furthermore, experiments at the solid/solid interface are more trustworthy than tests in solution for evaluating the self-cleaning ability. The differences of the photocatalytic phenomena at the solid/solid interface in comparison with the most studied photoactivated processes at the solid/liquid interface are outlined. Furthermore, photocatalytic materials showed selectivity toward some specific dyes. This encourages the use of more than one dye for the evaluation of the self-cleaning ability of a photocatalytic material.
光催化材料表面化合物的光致反应性被用于保持玻璃、混凝土和涂料表面的清洁。最近公布了一种量化非透明材料光催化自清洁（SC）性能的标准方法。该方法基于用规定量的染料覆盖样品表面，并评估辐照下有色表面的反射光谱。光谱变化的校准使得能够对表面残留染料进行量化，并评估自清洁动力学。使用亚甲基蓝（MB）、罗丹明B（RhB）和间胺黄（MY）对七种白色和有色光催化材料进行了该方法的测试。确定了MB在固/固界面光催化降解的主要副产物，表明MB在溶液中的降解路径与在固/固界面的路径有很大不同。MY也表现出不同的光反应活性顺序。此外，在评估自清洁能力方面，固/固界面的实验比溶液中的测试更可靠。概述了固/固界面光催化现象与研究最多的固/液界面光活化过程相比的差异。此外，光催化材料对某些特定染料表现出选择性。这促使在评估光催化材料的自清洁能力时使用不止一种染料。
