Varasteanu Pericle, Romanitan Cosmin, Bujor Alexandru, Tutunaru Oana, Craciun Gabriel, Mihalache Iuliana, Radoi Antonio, Kusko Mihaela
National Institute for Research and Development in Microtechnology (IMT-Bucharest), 126A Erou Iancu Nicolae Street, 077190 Voluntari, Romania.
Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125 Magurele, Romania.
Nanomaterials (Basel). 2020 Nov 23;10(11):2321. doi: 10.3390/nano10112321.
We report a simple, scalable route to wafer-size processing for fabrication of tunable nanoporous gold (NPG) by the anodization process at low constant current in a solution of hydrofluoric acid and dimethylformamide. Microstructural, optical, and electrochemical investigations were employed for a systematic analysis of the sample porosity evolution while increasing the anodization duration, namely the small angle X-ray scattering (SAXS) technique and electrochemical impedance spectroscopy (EIS). Whereas the SAXS analysis practically completes the scanning electronic microscopy (SEM) investigations and provides data about the impact of the etching time on the nanoporous gold layers in terms of fractal dimension and average pore surface area, the EIS analysis was used to estimate the electroactive area, the associated roughness factor, as well as the heterogeneous electron transfer rate constant. The bridge between the analyses is made by the scanning electrochemical microscopy (SECM) survey, which practically correlates the surface morphology with the electrochemical activity. The results were correlated to endorse the control over the gold film nanostructuration process deposited directly on the substrate that can be further subjected to different technological processes, retaining its properties. The results show that the anodization duration influences the surface area, which subsequently modifies the properties of NPG, thus enabling tuning the samples for specific applications, either optical or chemical.
我们报道了一种简单、可扩展的方法，用于通过在氢氟酸和二甲基甲酰胺溶液中以低恒定电流进行阳极氧化工艺来制造可调谐纳米多孔金（NPG）的晶圆级加工。在增加阳极氧化持续时间的过程中，采用微观结构、光学和电化学研究对样品孔隙率演变进行系统分析，即小角X射线散射（SAXS）技术和电化学阻抗谱（EIS）。SAXS分析实际上完善了扫描电子显微镜（SEM）研究，并提供了关于蚀刻时间对纳米多孔金层在分形维数和平均孔表面积方面影响的数据，而EIS分析则用于估计电活性面积、相关的粗糙度因子以及异质电子转移速率常数。扫描电化学显微镜（SECM）测量建立了分析之间的桥梁，它实际上将表面形态与电化学活性联系起来。结果相互关联，以支持对直接沉积在基板上的金膜纳米结构化过程的控制，该过程可进一步经受不同的工艺过程，同时保持其性能。结果表明，阳极氧化持续时间会影响表面积，进而改变NPG的性能，从而能够针对光学或化学等特定应用对样品进行调谐。
