Nanocrystals of the thermosalient (TS) material 1,2,4,5-tetrabromobenzene (TBB) with diameters of 20, 100 and 200 nm were prepared by using nanoporous anodic aluminum oxide (AAO) templates. In contrast with bulk crystallization, which mainly affords single crystals of TBB in the stable phase β, two-dimensional X-ray microdiffraction revealed exclusive formation of polycrystalline TBB in the less stable phase γ inside the AAO nanopores. While bulk crystals of TBB undergo TS transition from phase β to γ at 41 °C and melt at 180 °C, the nanocrystals of phase γ TBB remain stable from cryogenic temperatures to nearly 80 °C and sublime at higher temperature. This study reveals fundamentally different crystallization and thermal behaviour of the TS materials at the nanoscale compared to the macroscale.

中文翻译：

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1,2,4,5-四溴苯的纳米级结晶和热行为†

通过使用纳米多孔阳极氧化铝（AAO）模板，制备了直径20、100和200 nm的热敏（TS）材料1,2,4,5-四溴苯（TBB）的纳米晶体。与主要提供稳定相β的TBB单晶的块状结晶相反，二维X射线微衍射揭示了AAO纳米孔内不稳定的相γ中唯一形成多晶TBB。TBB的块状晶体在41°C时经历了从β相到γ的TS转变并在180°C时熔融，而γTBB相的纳米晶体在低温至接近80°C的温度下保持稳定，并在更高的温度下升华。这项研究揭示了与宏观尺度相比，TS材料在纳米尺度上的根本不同的结晶和热行为。