Nano‐sensor materials, especially if they target biological purposes, require fine control and tuning of the properties at the molecular scale when intramolecular properties have to be exploited, for example, in optical sensors. By means of optical spectroscopies (namely, spectrophotometry, spectrofluorimetry, and surface differential reflectivity), we demonstrate that thin films of porphycene show a spectacular chromatic change when exposed to acid vapors (specifically to hydrochloric acid). After exposure, the original optical properties of the porphycene films are recovered within a few seconds and without any thermal annealing. In addition, since clear spectroscopic signatures are observed both in absorption and in reflectivity, the parent porphycene is shown to be suitable even for deposition of films onto opaque substrates. These findings are of significant interest in view of potential engineering of the molecules and implementation in devices.

中文翻译：

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卟啉质子化：一种快速和可逆的反应，使光学传感能够进行酸传感

当必须利用分子内特性（例如在光学传感器中）时，纳米传感器材料，尤其是针对生物目的的纳米传感器材料，需要在分子尺度上对性能进行精细控制和调整。通过光学分光光度法（即分光光度法，分光荧光法和表面微分反射率），我们证明了当暴露于酸性蒸汽（特别是盐酸）时，卟啉的薄膜显示出惊人的色度变化。曝光后，卟啉薄膜的原始光学性能可在几秒钟内恢复，无需任何热退火。另外，由于在吸收和反射率上均观察到清晰的光谱特征，因此表明母卟啉甚至适用于将膜沉积在不透明的基底上。