Self-assembly of nanoparticles (NPs) to form structural colors offers promising opportunities for developing electronic, optoelectronic, and magnetic devices. In this regard, we reported co-assembly of cellulose nanofibrils (CNFs) and graphene to produce colored thin films. We demonstrated that biomimetic iridescent “peacock feather”-like full-color thin films can be generated by simple evaporation of aqueous suspensions on a surface tension confined, optically symmetric indium tin oxide-coated polyethylene terephthalate substrate. Amphiphilic CNFs serve dual functions to attract hydrophobic graphene via van der Waals interactions and to disperse hydrophilically and anionically CNF-tethered graphene while regulating surface tension to induce capillary and Marangoni flows in the force fields and construct thickness variation during dewetting. These CNF–graphene thin films exhibit full-color patterns and function as tunable light and moisture actuators. This approach has high potential to be applied to assemble other metal or metal oxide NPs for fast, simple, and robust fabrication without involving any complex lithography and external fields.

中文翻译：

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由两亲性纤维素纳米纤丝组装而成的光子薄膜，显示出虹彩全彩

纳米粒子 (NPs) 的自组装形成结构颜色为开发电子、光电和磁性器件提供了有希望的机会。在这方面，我们报道了纤维素纳米纤维（CNF）和石墨烯的共组装以生产彩色薄膜。我们证明了仿生虹彩“孔雀羽毛”状全彩薄膜可以通过在表面张力受限的光学对称氧化铟锡涂层聚对苯二甲酸乙二醇酯基材上简单蒸发水性悬浮液来产生。两亲性 CNF 具有双重功能，通过范德华相互作用吸引疏水性石墨烯，分散亲水性和阴离子性 CNF 束缚的石墨烯，同时调节表面张力以诱导力场中的毛细管和 Marangoni 流动，并在去湿过程中构建厚度变化。这些 CNF-石墨烯薄膜呈现出全彩图案，可作为可调光和湿度执行器。这种方法具有很高的潜力，可用于组装其他金属或金属氧化物 NP，以实现快速、简单和稳健的制造，而不涉及任何复杂的光刻和外部场。