Márk Géza I, Kertész Krisztián, Piszter Gábor, Bálint Zsolt, Biró László P
Institute of Technical Physics and Materials Science, Centre for Energy Research, P.O. Box 49, H-1525 Budapest, Hungary.
Hungarian Natural History Museum, Baross utca 13, H-1088 Budapest, Hungary.
Nanomaterials (Basel). 2019 May 17;9(5):759. doi: 10.3390/nano9050759.
Gas/vapor sensors based on photonic band gap-type materials are attractive as they allow a quick optical readout. The photonic nanoarchitectures responsible for the coloration of the wing scales of many butterfly species possessing structural color exhibit chemical selectivity, i.e., give vapor-specific optical response signals. Modeling this complex physical-chemical process is very important to be able to exploit the possibilities of these photonic nanoarchitectures. We performed measurements of the ethanol vapor concentration-dependent reflectance spectra of the butterfly, which exhibits structural color on both the dorsal (blue) and ventral (gold-green) wing sides. Using a numerical analysis of transmission electron microscopy (TEM) images, we revealed the details of the photonic nanoarchitecture inside the wing scales. On both sides, it is a 1D + 2D structure, a stack of layers, where the layers contain a quasi-ordered arrangement of air voids embedded in chitin. Next, we built a parametric simulation model that matched the measured spectra. The reflectance spectra were calculated by ab-initio methods by assuming variable amounts of vapor condensed to liquid in the air voids, as well as vapor concentration-dependent swelling of the chitin. From fitting the simulated results to the measured spectra, we found a similar swelling on both wing surfaces, but more liquid was found to concentrate in the smaller air voids for each vapor concentration value measured.
基于光子带隙型材料的气体/蒸汽传感器很有吸引力，因为它们能够实现快速光学读出。许多具有结构色的蝴蝶物种的翅鳞片颜色变化所涉及的光子纳米结构具有化学选择性，即能给出特定蒸汽的光学响应信号。对这种复杂的物理化学过程进行建模对于充分利用这些光子纳米结构的潜力非常重要。我们对一种蝴蝶的乙醇蒸汽浓度依赖性反射光谱进行了测量，这种蝴蝶在翅的上表面（蓝色）和下表面（金绿色）均呈现结构色。通过对透射电子显微镜（TEM）图像进行数值分析，我们揭示了翅鳞片内部光子纳米结构的细节。在翅的上下表面，它都是一种一维 + 二维结构，即一层一层的堆叠结构，其中各层含有嵌入几丁质中的准有序排列的空气空隙。接下来，我们建立了一个与测量光谱相匹配的参数模拟模型。通过从头算方法计算反射光谱，假设空气空隙中有不同量的蒸汽凝结成液体，以及几丁质的蒸汽浓度依赖性膨胀。通过将模拟结果与测量光谱进行拟合，我们发现在翅的两个表面上有类似的膨胀现象，但对于每个测量的蒸汽浓度值，发现更多的液体集中在较小的空气空隙中。
