“…Due to their optical transparency [1][2][3], thermal stability [1], biocompatibility [4], as well as the controllability of structural parameters [5], nanoporous (NP) alumina (Al2O3) films have attracted scientific and technological attention for nanotechnology and nanoengineering applications, such as drug delivery [4,6,7], electrochemical sensors [8,9], molecular transport [6,10,11], and solar-energy conversion [12]. Compared with bulk crystal Al2O3, NP Al2O3 has higher hardness, corrosion resistance, and wear resistance [13].…”