The development of visible-light-responsive inorganic photoreversible color switching materials (PCSMs) for constructing long-legible rewritable papers is fascinating owing to resource sustainability. This work reports the colloidal synthesis of WO_3–x hierarchical nanostructures constructed by 2D thin nanostructures with crystalline/amorphous homojunctions that show excellent visible-light-responsive color switching properties. The surface-bound hydroxyl ligands, oxygen vacancies, and homojunctions could enhance absorption in the visible region, improve charge separation and transfer efficiencies, and act as internal sacrificial electron donors for scavenging photogenerated holes, endowing WO_3–x hierarchical nanostructures with high visible-light-responsive photoreductive activity. The protons localized in WO_3–x hierarchical nanostructures promote photoreduction for the coloration process and stabilize metastable W⁵⁺ species for the discoloration process, enabling rapid coloration in 30 s upon 437 nm light illumination and excellent color stability under ambient air conditions (∼51 days). A light-printable rewritable paper (LPRP) fabricated by the WO_3–x hierarchical nanostructures exhibits a grayish white background, high reusability (>100 times), long legible time (>30 days), negligible interference by office light, and high color contrast. Moreover, the LPRP can be used for direct visible-light-responsive laser printing, which is fully compatible with current printing technology. This work opens an avenue for designing visible-light-responsive inorganic PCSMs for LPRP and utilizing visible light for practical applications.

中文翻译：

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缺氧 WO3–x 分层纳米结构的可见光响应光可逆颜色转换，用于长清晰可重写纸

由于资源的可持续性，用于构建长清晰可重写纸张的可见光响应无机光可逆颜色切换材料（PCSM）的开发是令人着迷的。这项工作报告了由具有晶体/非晶同质结的二维薄纳米结构构建的 WO _{3– x}分层纳米结构的胶体合成，该结构表现出优异的可见光响应颜色切换特性。表面结合的羟基配体、氧空位和同质结可以增强可见光区域的吸收，提高电荷分离和转移效率，并作为内部牺牲电子供体清除光生空穴，赋予WO _{3– x}分级纳米结构高可见光-光响应光还原活性。位于 WO _{3– x}分级纳米结构中的质子促进了着色过程的光还原，并稳定了变色过程中的亚稳态 W ⁵⁺物质，能够在 437 nm 光照射下在 30 秒内快速着色，并在环境空气条件下具有出色的颜色稳定性 (∼51天）。由WO _{3– x}分层纳米结构制造的光可打印可重写纸（LPRP）具有灰白色背景、高可重复使用性（>100次）、长可读时间（>30天）、办公室光线干扰可忽略不计和高色彩对比。此外，LPRP可用于直接可见光响应激光打印，与当前的打印技术完全兼容。这项工作为设计用于 LPRP 的可见光响应无机 PCSM 以及利用可见光进行实际应用开辟了一条途径。