Tahir M Nazir, Salloum Sarah, Rondeau-Gagné Simon, Eichhorn S Holger
Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B 3P4.
Langmuir. 2022 Sep 13;38(36):10943-10952. doi: 10.1021/acs.langmuir.2c01222. Epub 2022 Sep 1.
Incorporation of directing amide groups has been shown to facilitate the topochemical polymerization of 1,3-butadiyne (diacetylene) groups in noncrystalline phases such as gels, amorphous solids, and liquid crystals. It remains challenging to polymerize 1,3-butadiyne-containing alkylthiolate ligands within their self-assembled monolayers on gold nanoparticles (AuNPs), which enhances their stability and adds new optical and electronic properties. Especially smaller AuNPs of sizes below 5 nm in diameter have been reported to display sluggish photopolymerization and are susceptible to photodegradation under UV irradiation. To probe the effectiveness of the amide-directed photopolymerization of 1,3-butadiyne ligands, small AuNPs in the 2-4 nm range were synthesized that contain alkylthiolate ligands with and without amide and 1,3-butadiyne groups. Their photopolymerization and photostability were studied by transmission electron microscopy (TEM), UV-vis spectroscopy, and Raman spectroscopy. AuNP with amide-free 1,3-butadiyne ligands templated the polymerization of the 1,3-butadiyne ligands but fused to large and insoluble particles during the polymerization process. AuNPs with ligands containing both 1,3-butadiyne and amide groups polymerized significantly faster, which slowed down photodegradation. A UV irradiation (254 nm and 176 W/m) for 5-10 min was found to be optimal for the AuNPs with directing amide groups studied here, although their average core sizes grew from 3.8 to 4.0 nm in diameter and about 20% of the attached 1,3-butadiyne ligands remained unreacted after 10 minutes of irradiation. About 75% of the attached 1,3-butadiyne ligands were already polymerized during the first 5 min of UV irradiation. This decrease in reactivity is reasoned with a fast polymerization of ligands attached to facet sites and slower polymerization rates for ligands attached to edge and corner sites. Unexpectedly, photopolymerization occurred only in the presence of solvent, whereas no polydiacetylene was generated when dry powders of any of the diacetylene-containing gold nanoparticles were irradiated.
已证明引入导向酰胺基团有助于在凝胶、非晶态固体和液晶等非晶相中实现1,3 - 丁二炔（双乙炔）基团的拓扑化学聚合。在金纳米颗粒（AuNP）上的自组装单分子层中聚合含1,3 - 丁二炔的烷基硫醇盐配体仍然具有挑战性，这一过程可增强其稳定性并赋予新的光学和电子性质。据报道，特别是直径小于5 nm的较小AuNP表现出缓慢的光聚合反应，并且在紫外线照射下易发生光降解。为了探究酰胺导向的1,3 - 丁二炔配体光聚合的有效性，合成了直径在2 - 4 nm范围内的小AuNP，其包含有和没有酰胺及1,3 - 丁二炔基团的烷基硫醇盐配体。通过透射电子显微镜（TEM）、紫外 - 可见光谱和拉曼光谱研究了它们的光聚合和光稳定性。具有不含酰胺的1,3 - 丁二炔配体的AuNP模板化了1,3 - 丁二炔配体的聚合，但在聚合过程中融合成大的不溶性颗粒。具有同时含1,3 - 丁二炔和酰胺基团配体的AuNP聚合速度明显更快，这减缓了光降解。对于此处研究的具有导向酰胺基团的AuNP，发现紫外线照射（254 nm和176 W/m）5 - 10分钟是最佳的，尽管它们的平均核心直径从3.8 nm增长到4.0 nm，并且在照射10分钟后约20%的附着1,3 - 丁二炔配体仍未反应。在紫外线照射的前5分钟内，约75%的附着1,3 - 丁二炔配体已经聚合。反应性的这种降低归因于附着在晶面位点的配体快速聚合，而附着在边缘和角落位点的配体聚合速率较慢。出乎意料的是，光聚合仅在有溶剂存在的情况下发生，而当任何含双乙炔的金纳米颗粒的干粉受到照射时，不会生成聚二乙炔。
