Sorbonne Université, CNRS - UMR 7197, Laboratoire de Réactivité de Surface (LRS) F-75005, Paris, France.
Phys Chem Chem Phys. 2018 May 9;20(18):12898-12907. doi: 10.1039/c7cp08054a.
We investigate the characteristics, fate and photocatalytic activity of spheroid- and rod-shaped TiO2 nano-crystals in aqueous solutions to better understand their behaviour in media of biological and environmental interest. For this purpose, the potential of a solvothermal method in synthesizing highly crystalline nanoparticles and tuning their sizes/shapes is explored. Spheroid- and rod-shaped nanoparticles are successfully obtained with different aspect ratios, while keeping their structures as well as their cross-sectional areas identical. The aggregation/agglomeration of these nanostructures in aqueous solutions shows an obvious shape effect, revealing critical coagulation concentrations (CCCs) significantly lower for the rods compared to the spheroids (aspect ratio ∼ 2-3). This trend is observed in both NaCl and CaCl2 electrolytes at pH values above and below the pHPZC of TiO2 nanoparticles. The photocatalytic activity of the spheroids is unexpectedly superior to that of the rods at NaCl and CaCl2 concentrations over a range of 2 to 100 and 1 to 50 mM, respectively. Our results show that an increase in the chloride concentration leads to an inhibition of the photocatalytic activity rate, with a more pronounced impact for the rods. In contrast, the size of aggregates/agglomerates has only a little effect on the photocatalytic properties of both nano-crystals.
我们研究了球形和棒形 TiO2 纳米晶体在水溶液中的特性、命运和光催化活性，以更好地了解它们在生物和环境相关介质中的行为。为此，我们探索了溶剂热法在合成高结晶度纳米粒子和调节其尺寸/形状方面的潜力。我们成功地获得了具有不同纵横比的球形和棒形纳米粒子，同时保持了它们的结构和截面积相同。这些纳米结构在水溶液中的聚集/团聚显示出明显的形状效应，表明与球形相比，棒形的临界聚结浓度（CCC）显著降低（纵横比约为 2-3）。在 pH 值高于和低于 TiO2 纳米粒子等电点的 NaCl 和 CaCl2 电解质中，都观察到了这种趋势。在 NaCl 和 CaCl2 浓度范围内为 2 至 100 和 1 至 50 mM 时，球形的光催化活性出人意料地优于棒形，我们的结果表明，随着氯化物浓度的增加，光催化活性速率受到抑制，棒形的影响更为明显。相比之下，聚集体/团聚体的大小对两种纳米晶体的光催化性能只有很小的影响。
