The effect of thermal treatment on the morphology (crystalline phase and size) and photocatalytic activity of freshly prepared TiO₂ nano-powder is communicated. TiO₂ nano-powders, prepared by hydrolyzing titanium tetraisopropoxide at room temperature, were all dried at 382 K and subsequently calcined at different temperatures, for 1 h, up to 1172 K. Raman analysis of each thermally treated sample exhibited different titania phase structures. Up to 772 K a mixture of brookite and anatase phases was observed, while a mixture of all three phases, i.e. anatase, brookite and rutile, was observed at 872 K, with a rutile only phase at 1097 K and above. The photocatalytic activity of all samples was assessed by means of the photocatalytic degradation of methyl orange dye (MeO). All anatase-brookite compositions exhibited high photocatalytic activity with the rate of degradation decreasing with increasing calcination temperature, which coincides with (i) a slight increase of the anatase phase, (ii) a slight decrease of the brookite phase, and (iii) a gradual increase of the crystallite size of all phases. The greatest photocatalytic activity was observed for the sample calcined at 382 K, which contained the highest amount of brookite (in the presence of anatase as the dominant phase), while the lowest rate was observed for the pure rutile sample.

交流了热处理对新鲜制备的TiO ₂纳米粉体的形貌（晶相和尺寸）和光催化活性的影响。二氧化钛₂通过在室温下水解四异丙氧基钛制备的纳米粉末，均在382 K下干燥，随后在不同温度下煅烧1 h，直至1172K。每个热处理样品的拉曼分析显示不同的二氧化钛相结构。高达772 K时，观察到板钛矿和锐钛矿相的混合物，而在872 K时观察到所有三相的混合物，即锐钛矿，板钛矿和金红石，只有金红石相在1097 K和更高。通过甲基橙染料（MeO）的光催化降解来评估所有样品的光催化活性。所有锐钛矿-板钛矿成分均表现出较高的光催化活性，降解速率随煅烧温度的升高而降低，这与（i）锐钛矿相的轻微增加相吻合。（ii）板钛矿相的稍微减少，以及（iii）所有相的微晶尺寸逐渐增加。对于在382 K下煅烧的样品，观察到其最大的光催化活性，该样品中的板钛矿含量最高（在锐钛矿为主导相的情况下），而对纯金红石样品则观察到最低的催化活性。