Fast and easily distinguishable color change is the simplest sensor signal recognized by naked eyes. Rapid color change has been done via filling or removing liquid inside channels constructed by multilayered reflectors in biological species for camouflage or signaling. By mimicking it, a test paper for fast detection of similar organic solvents or water-content in ethanol has been designed based on nanocomposite films composed of cellulose nanocrystals (CNC) and polyvinylpyrrolidone (PVP) with chiral nematic structure. The chiral nematic architecture and structural color of CNC can be kept in CNC/PVP nanocomposites in a wide range of PVP content, up to 70 wt %. Moreover, we have observed that the nanocomposite containing higher weight percentage of PVP showed more distinguishable color difference while dipping in similar solvents. Owing to the wide solubility of PVP in organic solvents and the magnifying effect via increasing content of PVP, CNC/PVP nanocomposite films can work as discrimination sensors by presenting apparent color change while being dipping in several groups of similar organic solvents, such as homologues (methanol/ethanol), skeletal isomers (1-propanol/2-propanol), halogenated hydrocarbons (choloroform/dichloromethane), and even ethanol containing a small amount of water. The fast color change of CNC/PVP has been induced by the sensitive response of its structural color to the volume fraction change of CNC in the swollen state.

中文翻译：

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虹彩手性向列纤维素纳米晶体/聚乙烯吡咯烷酮纳米复合薄膜，用于区分相似的有机溶剂

快速，容易区分的颜色变化是肉眼识别的最简单的传感器信号。通过填充或去除由生物物种中的多层反射器构成的通道内的液体以进行伪装或发出信号，可以快速改变颜色。通过模仿，已设计出一种用于快速检测乙醇中类似有机溶剂或水含量的试纸，该试纸基于具有手性向列结构的纤维素纳米晶体（CNC）和聚乙烯吡咯烷酮（PVP）组成的纳米复合膜。CNC的手性向列结构和结构颜色可以在CNC / PVP纳米复合材料中以高达70 wt％的广泛PVP含量保持。此外，我们已经观察到，含有较高重量百分比的PVP的纳米复合材料在浸入相似溶剂时显示出更明显的色差。由于PVP在有机溶剂中的广泛溶解性以及通过增加PVP的含量而产生的放大作用，CNC / PVP纳米复合膜可以通过呈现明显的颜色变化，同时浸入几组相似的有机溶剂（例如同系物）中，从而作为判别传感器。甲醇/乙醇），骨架异构体（1-丙醇/ 2-丙醇），卤代烃（氯仿/二氯甲烷），甚至是含少量水的乙醇。CNC / PVP的快速颜色变化是由其结构颜色对溶胀状态下CNC的体积分数变化的敏感响应引起的。CNC / PVP纳米复合膜可以通过呈现明显的颜色变化，同时浸入几组相似的有机溶剂（例如同系物（甲醇/乙醇），骨架异构体（1-丙醇/ 2-丙醇），卤代烃（氯仿/二氯甲烷），甚至乙醇中也含有少量水。CNC / PVP的快速颜色变化是由其结构颜色对溶胀状态下CNC的体积分数变化的敏感响应引起的。CNC / PVP纳米复合膜可以通过呈现明显的颜色变化，同时浸入几组相似的有机溶剂（例如同系物（甲醇/乙醇），骨架异构体（1-丙醇/ 2-丙醇），卤代烃（氯仿/二氯甲烷），甚至乙醇中也含有少量水。CNC / PVP的快速颜色变化是由于其结构颜色对溶胀状态下CNC的体积分数变化的敏感响应所致。