Department of Chemistry, University of California, Riverside, CA 92521 (USA).
Angew Chem Int Ed Engl. 2015 Jan 19;54(4):1321-6. doi: 10.1002/anie.201410408.
Colloidal barium-doped TiO2 nanocrystals have been developed that enable the highly reversible light-responsive color switching of redox dyes with excellent cycling performance and high switching rates. Oxygen vacancies resulting from the Ba doping serve as effective sacrificial electron donors (SEDs) to scavenge the holes photogenerated in TiO2 nanocrystals under UV irradiation and subsequently promote the reduction of methylene blue to its colorless leuco form. Effective color switching can therefore be realized without relying on external SEDs, thus greatly increasing the number of switching cycles. Ba doping can also accelerate the recoloration under visible-light irradiation by shifting the absorption edge of TiO2 nanocrystals to a shorter wavelength. Such a system can be further casted into a solid film to produce a rewritable paper on which letters and patters can be repeatedly printed using UV light and then erased by heating; this process can be repeated for many cycles and does not require additional inks.
已开发出胶体钡掺杂 TiO2 纳米晶，可实现氧化还原染料的高可逆光响应颜色切换，具有出色的循环性能和高切换速率。Ba 掺杂产生的氧空位可用作有效的牺牲电子供体 (SED)，可在紫外光照射下清除 TiO2 纳米晶中产生的空穴，并随后促进亚甲基蓝还原为无色的隐色形式。因此，无需依赖外部 SED 即可实现有效的颜色切换，从而大大增加了切换循环的次数。Ba 掺杂还可以通过将 TiO2 纳米晶的吸收边缘移动到较短的波长来加速可见光照射下的再着色。该系统还可以浇铸成固体膜，在其上可以使用紫外光重复打印字母和图案，然后通过加热擦除；此过程可以重复多次，且无需额外的墨水。
