Department of Chemistry, Physical Chemistry I, University of Bayreuth, Universitätsstraße 30, 95447, Bayreuth, Germany.
Department of Chemistry, Inorganic Chemistry III and Northern Bavarian NMR Center, University of Bayreuth, 95447, Universitätsstraße 30, Bayreuth, Germany.
Adv Sci (Weinh). 2023 Apr;10(11):e2206616. doi: 10.1002/advs.202206616. Epub 2023 Feb 15.
Passive radiative daytime cooling is an emerging technology contributing to carbon-neutral heat management. Optically engineered materials with distinct absorption and emission properties in the solar and mid-infrared range are at the heart of this technology. Owing to their low emissive power of about 100 W m during daytime, substantial areas need to be covered with passive cooling materials or coatings to achieve a sizeable effect on global warming. Consequently, biocompatible materials are urgently needed to develop suitable coatings with no adverse environmental impact. It is shown how chitosan films with different thicknesses can be produced from slightly acidic aqueous solutions. The conversion to their insoluble form chitin in the solid state is demonstrated and the conversion is monitored with infrared (IR) and NMR spectroscopy. In combination with a reflective backing material, the films show below-ambient temperature cooling capabilities with a suitable emissivity in the mid-IR region and low solar absorption of 3.1-6.9%, depending on the film thickness. This work highlights the potential of chitosan and chitin as widely available biocompatible polymers for passive radiative cooling applications.
被动辐射日射冷却技术是一种新兴的碳中和热管理技术。在该技术中，具有独特的太阳吸收和中红外发射特性的光学工程材料是核心。由于它们在白天的发射率约为 100 W m，因此需要大面积覆盖被动冷却材料或涂层，才能对全球变暖产生显著影响。因此，迫切需要开发具有生物相容性且无不良环境影响的合适涂层的材料。本文展示了如何从微酸性水溶液中制备不同厚度的壳聚糖薄膜。证明了其在固态下转化为不溶性形式几丁质，并通过红外（IR）和 NMR 光谱对转化进行了监测。与反射背衬材料相结合，薄膜在中红外区域具有低于环境温度的冷却能力，并且具有低的太阳能吸收率 3.1-6.9%，具体取决于薄膜厚度。这项工作突出了壳聚糖和几丁质作为广泛可用的生物相容性聚合物在被动辐射冷却应用中的潜力。
