A low-angle–dependent photonic crystal hydrogel (LAD-PCH) material was developed to simultaneously detect and remove uranyl ions (UO22+). Different from traditional SiO2 photonic crystal hydrogel with the problem of angle dependency, the LAD-PCH material overcomes the restriction of observation direction. The LAD-PCH is a composite material with the photonic crystal array of 180-nm monodisperse CdS@SiO2 particles embedded into the functional hydrogel. As one UO22+ can bind to multiple carboxyl groups and amide groups, the functional hydrogel fabricated by acrylic acid and acrylamide will shrink after chelating. These changes in the hydrogel volume alter the array spacing and trigger a blue shift of diffraction wavelength and naked-eye visual color changes of LAD-PCH. The color can vary from orange-red to orange, yellow, green, and cyan, corresponding to the determination range of 100 pM–100 μM. The LAD-PCH material detects UO22+ sensitively as the lowest detectable concentration is about 100 pM, and removes UO22+ high-efficiently as the maximum adsorption capacity of U(VI) is about 1010 mg g−1 at 298 K. This LAD-PCH material is convenient and has potential to simultaneously monitor and remove UO22+ from uranium-polluted water. Schematic representation of the low-angle–dependent photonic crystal hydrogel (LAD-PCH) material for UO22+ detection and removal: The structural colors of LAD-PCH material overcome the restriction of observation angles. After the ligands complex with UO22+, the networks of LAD-PCH show different degrees of shrinkage; these volume changes of hydrogel trigger obvious naked-eye visual color changes of LAD-PCH. Schematic representation of the low-angle–dependent photonic crystal hydrogel (LAD-PCH) material for UO22+ detection and removal: The structural colors of LAD-PCH material overcome the restriction of observation angles. After the ligands complex with UO22+, the networks of LAD-PCH show different degrees of shrinkage; these volume changes of hydrogel trigger obvious naked-eye visual color changes of LAD-PCH.

中文翻译：

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用于视觉检测和去除铀酰离子的低角度依赖 CdS@SiO2 光子晶体水凝胶材料

开发了一种低角度依赖光子晶体水凝胶 (LAD-PCH) 材料以同时检测和去除铀酰离子 (UO22+)。与传统的SiO2光子晶体水凝胶存在角度依赖性问题不同，LAD-PCH材料克服了观察方向的限制。LAD-PCH 是一种复合材料，将 180 nm 单分散 CdS@SiO2 颗粒的光子晶体阵列嵌入功能水凝胶中。由于一个UO22+可以与多个羧基和酰胺基结合，丙烯酸和丙烯酰胺制备的功能性水凝胶螯合后会收缩。水凝胶体积的这些变化会改变阵列间距并触发 LAD-PCH 的衍射波长蓝移和肉眼视觉颜色变化。颜色可以从橙红色到橙色、黄色、绿色和青色，对应的测定范围为 100 pM–100 μM。LAD-PCH 材料灵敏地检测 UO22+，最低可检测浓度约为 100 pM，并高效去除 UO22+，因为 U(VI) 在 298 K 下的最大吸附容量约为 1010 mg g-1。这种 LAD-PCH 材料方便并且有可能同时监测和去除铀污染水中的 UO22+。用于 UO22+ 检测和去除的低角度依赖光子晶体水凝胶 (LAD-PCH) 材料的示意图：LAD-PCH 材料的结构颜色克服了观察角度的限制。配体与UO22+复合后，LAD-PCH的网络呈现不同程度的收缩；水凝胶的这些体积变化引发了 LAD-PCH 明显的肉眼视觉颜色变化。用于 UO22+ 检测和去除的低角度依赖光子晶体水凝胶 (LAD-PCH) 材料的示意图：LAD-PCH 材料的结构颜色克服了观察角度的限制。配体与UO22+复合后，LAD-PCH的网络呈现不同程度的收缩；水凝胶的这些体积变化引发了 LAD-PCH 明显的肉眼视觉颜色变化。