We found that mixed films made of the title aminoazobenzene-based material with various organic acids exhibited reversible colour changes in response to exhaled breath. Such reversible colour changes were shown to be general phenomena for films composed of aminoazobenzene-based amorphous molecular materials mixed together with organic acids. The ability of this type of film to reversibly change colour was suggested to be due to protonation of the aminoazobenzene caused by the organic acid and deprotonation by moisture, and the acidity levels and concentrations of the organic acids were suggested to be important factors affecting the colour of the film and its response to moisture.

中文翻译：

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由4,4'-双[双（双（4-甲基苯基）氨基]偶氮苯和有机酸组成的混合膜对呼出气的可逆颜色变化†

我们发现，由标题氨基偶氮苯基材料与各种有机酸制成的混合膜在呼气时表现出可逆的颜色变化。对于由基于氨基偶氮苯的非晶态分子材料与有机酸混合而成的薄膜，这种可逆的颜色变化已证明是普遍现象。这种类型的薄膜可逆改变颜色的能力被认为是由于有机酸引起的氨基偶氮苯的质子化和水分引起的去质子化，而有机酸的酸度水平和浓度被认为是影响颜色的重要因素。膜的附着力及其对水分的反应。