响应性气-水界面的光开关表面活性剂：偶氮与芳基偶氮吡唑两亲物
Photo-Switchable Surfactants for Responsive Air-Water Interfaces: Azo vs. Arylazopyrazole Amphiphiles
摘要：
芳基偶氮吡唑（AAP）作为偶氮衍生物的替代物，由于其优异的性能，提供高收率的E/Z光异构化而受到广泛关注。为了比较和量化它们的性能，合成了偶氮苯四乙基铵（Azo-TB）和芳基偶氮吡唑四乙基铵（AAP-TB）溴化物，并使用NMR光谱在本体（水）中进行表征。在空气-水界面的振动和频发生（SFG）光谱和中子反射计（NR）的补充信息，揭示了E/Z异构化的影响非常详细。在本体水中，对于在两个方向上的E/Z切换，>89%的光稳态对于表面活性剂是非常相似的，而它们的界面行为是实质上不同的。特别是，对于AAP-TB，表面活性剂的表面过量$Γ$在E/Z异构体之间变化剧烈（$Γ$的最大变化：2.15 $μ$ mol/m $^2$）;对于Azo-TB，变化仅为中等（$Γ$的最大变化：1.02 $μ$ mol/m $^2$）。SFG光谱的分析表明，强非共振的贡献，外差的共振振动带是成正比的$Γ$，使芳香族C-H带被解释为一个指标的变化，在界面上的分子秩序。将NR的$Γ$与芳香族C-H伸缩的SFG幅度作为浓度和E/Z构象的函数进行密切比较，揭示了AAP-TB的实质性分子顺序变化。相比之下，Azo-TB仅$Γ$发生变化，分子顺序不变。界面性质的这些差异归因于AAP中心的分子结构，其能够在空气-水界面处实现有利的横向相互作用，从而在E/Z光异构化期间引起紧密堆积的界面层和实质性变化。
英文摘要：
Arylazopyrazoles (AAPs) as substitutes for azo derivatives have gained considerable attention due to their superior properties offering E/Z photo-isomerization with high yield. In order to compare and quantify their performance, azobenzene tetraethylammonium (Azo-TB) and arylazopyrazole tetraethylammonium (AAP-TB) bromides were synthesized and characterized in the bulk (water) using NMR spectroscopy. At the air-water interface complementary information from vibrational sum-frequency generation (SFG) spectroscopy and neutron reflectometry (NR) has revealed the effects of E/Z isomerization in great detail. In bulk water the photostationary states of >89% for E/Z switching in both directions were very similar for the surfactants, while their interfacial behavior was substantially different. In particular, the surface excess $Γ$ of the surfactants changed drastically between E/Z isomers for AAP-TB (maximum change of $Γ$: 2.15 $μ$mol/m$^2$); for Azo-TB the change was only moderate (maximum change of $Γ$: 1.02 $μ$mol/m$^2$). Analysis of SFG spectra revealed that strong non-resonant contributions that heterodyned the resonant vibrational bands were proportional to $Γ$, enabling the aromatic C-H band to be interpreted as an indicator for changes in interfacial molecular order. Close comparison of $Γ$ from NR with the SFG amplitude from the aromatic C-H stretch as a function of concentrations and E/Z conformation revealed substantial molecular order changes for AAP-TB. In contrast, only $Γ$ and not the molecular order varied for Azo-TB. These differences in interfacial properties are attributed to the molecular structure of the AAP center that enables favorable lateral interactions at the air-water interface, causing closed-packed interfacial layers and substantial changes during E/Z photo-isomerization.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
