For an optically transparent, UV‐reflective film, hollow silica nanospheres smaller than the visible wavelength (<λ_vis) are prepared and assembled into colloidal glasses, of which interstices are then backfilled with a polymer. The polymer refractive index is matched with the silica shell to minimize backscattering in the visible range, and the average distance between the hollow silica particles is adjusted by tuning the shell thickness to satisfy the interference resonance condition for a UV selective reflection. The resulting composite film shows a strong UV reflection as expected, but it is translucent in visible light due to non‐negligible backscattering, which may be caused by large defects or fluctuation of the particle concentration. In order to avoid such backscattering, another polymer is introduced of which the refractive index is matched with the average refractive index of the hollow nanospheres. This allows an optically transparent film that selectively reflects the UV light. Furthermore, spherical aggregates of hollow silica nanospheres called “supraballs” are prepared and their average refractive index is matched with a solvent by adjusting the mixture ratio of water and ethylene glycol, which yields an optically transparent solution, selectively reflecting UV.

中文翻译：

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空心二氧化硅纳米球组成的透明和紫外线反射光子膜和超球

对于光学透明的紫外线反射膜，中空的二氧化硅纳米球小于可见波长（< _λvis）制备并组装成胶体玻璃，然后用聚合物回填其空隙。聚合物的折射率与二氧化硅壳相匹配，以最大程度地减小可见光范围内的反向散射，中空二氧化硅颗粒之间的平均距离可通过调节壳的厚度来满足UV选择性反射的干涉共振条件来调节。所得复合膜显示出预期的强烈UV反射，但由于不可忽略的反向散射而在可见光下是半透明的，这可能是由较大的缺陷或颗粒浓度的波动引起的。为了避免这种反向散射，引入了另一种聚合物，该聚合物的折射率与中空纳米球的平均折射率匹配。这允许选择性地反射UV光的光学透明膜。此外，制备了空心二氧化硅纳米球的球形聚集体，称为“超球”，并通过调节水与乙二醇的混合比使其平均折射率与溶剂匹配，从而产生了光学透明的溶液，选择性地反射了紫外线。