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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Self-organization of 1-methylnaphthalene on the surface of artificial snow grains: A combined experimental-computational approach
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Self-organization of 1-methylnaphthalene on the surface of artificial snow grains: A combined experimental-computational approach

机译：人工雪粒表面上1-甲基萘的自组织：实验与计算相结合的方法

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A combined experimental-computational approach was used to study the self-organization and microenvironment of 1-methylnaphthalene (1MN) deposited on the surface of artificial snow grains from vapors at 238 K. The specific surface area of this snow (1.1 × 10~4 cm~2 g~(-1)), produced by spraying very fine droplets of pure water from a nebulizer into liquid nitrogen, was determined using valerophenone photochemistry to estimate the surface coverage by 1MN. Fluorescence spectroscopy at 77 K, in combination with molecular dynamics simulations, and density functional theory (DFT) and second-order coupled cluster (CC2) calculations, provided evidence for the occurrence of ground- and excited-state complexes (excimers) and other associates of 1MN on the snow grains' surface. Only weak excimer fluorescence was observed for a loading of 5 × 10~(-6) mol kg~(-1), which is ~2-3 orders of magnitude below monolayer coverage. However, the results indicate that the formation of excimers is favored at higher surface loadings (>5 × 10~(-5) mol kg~(-1)), albeit still being below monolayer coverage. The calculations of excited states of monomer and associated moieties suggested that a parallel-displaced arrangement is responsible for the excimer emission observed experimentally, although some other associations, such as T-shape dimer structures, which do not provide excimer emission, can still be relatively abundant at this surface concentration. The hydrophobic 1MN molecules, deposited on the ice surface, which is covered by a relatively flexible quasi-liquid layer at 238 K, are then assumed to be capable of dynamic motion resulting in the formation of energetically preferred associations to some extent. The environmental implications of organic compounds' deposition on snow grains and ice are discussed.
机译：实验与计算相结合的方法用于研究在238 K的蒸气下沉积在人造雪粒表面的1-甲基萘（1MN）的自组织和微环境。该雪的比表面积（1.1×10〜4通过使用戊二酮光化学法测定1MN的表面覆盖率，确定了通过将来自雾化器的非常细的纯水液滴喷入液氮中而产生的cm〜2 g〜（-1））。结合分子动力学模拟，密度泛函理论（DFT）和二阶耦合簇（CC2）计算，在77 K下进行荧光光谱分析，为出现基态和激发态复合物（准分子）和其他缔合体提供了证据在雪粒表面的1MN在5×10〜（-6）mol kg〜（-1）的负载下仅观察到弱的准分子荧光，比单层覆盖低约2-3个数量级。然而，结果表明，尽管仍低于单层覆盖率，但在较高的表面载荷（> 5×10〜（-5）mol kg〜（-1））下，准分子的形成是有利的。单体和相关基团的激发态计算表明，平行位移排列是实验观察到的准分子发射的原因，尽管某些其他缔合（例如不提供准分子发射的T型二聚体结构）仍然相对在此表面浓度下含量很高。假定沉积在冰面上的疏水性1MN分子在238 K下被一个相对柔软的准液体层覆盖，该分子能够动态运动，从而在一定程度上形成能量上优选的缔合。讨论了有机化合物在雪粒和冰上的沉积对环境的影响。

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