López Carlos, Galmés Bartomeu, Soberats Bartolomé, Frontera Antonio, Rotger Carmen, Costa Antonio
Department of Chemistry, Universitat de les Illes Balears, Ctra. Valldemossa km 7.5, 07122 Palma, Spain.
ACS Omega. 2019 Sep 3;4(12):14868-14874. doi: 10.1021/acsomega.9b01459. eCollection 2019 Sep 17.
The functionalization of interfaces has become very important for the protection or modification of metal (metal oxides) surfaces. The functionalization of aluminum is particularly interesting because of its relevance in fabricating components for electronic devices. In this work, the utilization of squaramic acids for the functionalization of aluminum substrates is reported for the first time. The physicochemical properties of the interfaces rendered by -alkyl squaramic acids on aluminum metal substrates coated with pseudoboehmite [Al(O)(OH)] layers are characterized by contact angle, grazing-angle Fourier-transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and matrix-assisted laser desorption ionization time-of-flight. Moreover, we could confirm the squaramic functionalization of the substrates by diffuse reflectance UV-vis spectroscopy, which cannot be used for the characterization of UV-vis-inactive substrates such as carboxylates and phosphonates, commonly used for coating metallic surfaces. Remarkably, the results of sorption experiments indicate that long-chain alkyl squaramic acid desorbs from activated-aluminum substrates at a reduced rate compared to palmitic acid, a carboxylic acid frequently used for the functionalization of metal oxide surfaces. Theoretical calculations indicate that the improved anchoring properties of squaramic acids over carboxylates are probably due to the formation of additional hydrogen bonding interactions on the interface. Accordingly, we propose -alkyl squaramic acids as new moieties for efficient functionalization of metal oxides.
界面功能化对于金属（金属氧化物）表面的保护或改性已变得非常重要。铝的功能化尤其引人关注，因为它在制造电子器件组件方面具有重要意义。在这项工作中，首次报道了利用方酸对铝基底进行功能化。通过接触角、掠角傅里叶变换红外光谱、原子力显微镜、扫描电子显微镜、X射线光电子能谱和基质辅助激光解吸电离飞行时间质谱对涂覆有拟薄水铝石[Al(O)(OH)]层的铝金属基底上的烷基方酸所形成的界面的物理化学性质进行了表征。此外，我们能够通过漫反射紫外可见光谱确认基底的方酸功能化，而漫反射紫外可见光谱不能用于表征常用于涂覆金属表面的诸如羧酸盐和膦酸盐等紫外可见无活性的基底。值得注意的是，吸附实验结果表明，与常用于金属氧化物表面功能化的羧酸棕榈酸相比，长链烷基方酸从活性铝基底上解吸的速率较低。理论计算表明，方酸相对于羧酸盐具有更好的锚固性能可能是由于在界面上形成了额外的氢键相互作用。因此，我们提出烷基方酸作为金属氧化物高效功能化的新基团。
