Genovese Maria E, Abraham Sinoj, Caputo Gianvito, Nanni Gabriele, Kumaran Surjith K, Montemagno Carlo D, Athanassiou Athanassia, Fragouli Despina
Smart Materials, Istituto Italiano di Tecnologia, Via Morego 30, Genova 16163, Italy.
Department of Chemical and Materials Engineering, University of Alberta, 9211-116 Street NW, Edmonton T6G 1H9, Canada.
ACS Omega. 2018 Oct 18;3(10):13484-13493. doi: 10.1021/acsomega.8b02570. eCollection 2018 Oct 31.
A photoresponsive microstructured composite is fabricated through the impregnation of cellulosic filter paper (FP) with a spiropyran-modified acrylic polymer. The polymer enwraps uniformly each individual cellulose fiber, increases the thermal stability of cellulose, and ensures the preservation of the composite functionalities even upon removal of the surface layers through mechanical scratching. The photochromic spiropyran moieties of the polymer, even while embedded in the cellulosic sheet, can reversibly interconvert between the colorless spiropyran and the pink merocyanine isomeric states upon irradiation with UV and visible light, respectively. Moreover, the photochromic polymer presents a faster photochromic response and a higher resistance to photodegradation, with an outstanding reusability for more than 100 switching cycles when it is incorporated in the cellulose network. Most importantly, the acidochromism of the modified FP, attributed to the spiropyran molecules after UV activation, allows the real-time optical and visual detection of acidity changes and spoilage in food products, such as wine and milk. Spoilage due to bacterial degradation and oxidation processes generates acidic vapors that induce the protonation of the merocyanine. This results in a visually detectable chromic transition from pink to white of the treated cellulose fibers, corresponding to a blue shift in the absorption spectrum. The developed photoresponsive cellulose composite can serve as cost-effective robust optical component in integrated functional platforms and consumer-friendly indicators for smart food packaging, as well as portable acidoresponsive interfaces for gas monitoring in industrial and environmental applications.
通过用螺吡喃改性的丙烯酸聚合物浸渍纤维素滤纸（FP）制备了一种光响应性微结构复合材料。该聚合物均匀地包裹每一根纤维素纤维，提高了纤维素的热稳定性，并确保即使通过机械刮擦去除表面层，复合材料的功能仍能得以保留。聚合物中的光致变色螺吡喃部分，即使嵌入纤维素片材中，在分别用紫外线和可见光照射时，也能在无色螺吡喃和粉红色部花青异构态之间可逆地相互转换。此外，这种光致变色聚合物具有更快的光致变色响应和更高的抗光降解性，当它被纳入纤维素网络时，具有超过100个开关循环的出色可重复使用性。最重要的是，改性FP的酸致变色现象，归因于紫外线活化后的螺吡喃分子，能够实时光学和视觉检测食品（如葡萄酒和牛奶）中的酸度变化和变质情况。细菌降解和氧化过程导致的变质会产生酸性蒸汽，从而引起部花青的质子化。这导致处理过的纤维素纤维在视觉上可检测到从粉红色到白色的变色转变，对应于吸收光谱中的蓝移。所开发的光响应性纤维素复合材料可作为集成功能平台中经济高效的坚固光学组件、智能食品包装中用户友好的指示剂，以及工业和环境应用中用于气体监测的便携式酸响应界面。
