Abstract Nanoporous alumina-based structures (NPA-bSs) obtained by anodization of aluminum in sulfuric acid medium were coated by atomic layer deposition (ALD) of a thin conformal layer of different functional oxides (Al2O3, TiO2, Fe2O3 or ZnO), leading to samples with similar geometrical parameters but different surface materials. Morphological characterization of the NPA-bSs confirms a reduction of about 35% in pore size associated to the presence of the oxides of interest, while chemical surface analysis permits the estimation of cover layer purity and thickness. Additionally, ALD functionalization also modifies optical (band-gap, refractive index and dielectric constant) according to transmittance and spectroscopic ellipsometry results for visible and near-infrared regions, as well as electrolyte diffusive transport parameters (effective fixed charge, ion transport numbers or ionic permselectivity) of the NPA-bSs, both of which are dependent on the nature of the coating layer. Therefore, the suitability of ALD technique for geometrical and functional modification of nanoporous structures is demonstrated, thus broadening the potential application of these NPA-bSs platforms to optical sensing, nanophotonics, biosensing, microfluidics or drug delivery applications.

中文翻译：

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ALD 改性纳米多孔氧化铝基结构的化学、光学和传输表征

摘要 通过铝在硫酸介质中阳极氧化获得的纳米多孔氧化铝基结构 (NPA-bSs) 通过原子层沉积 (ALD) 涂覆不同功能氧化物 (Al2O3、TiO2、Fe2O3 或 ZnO) 的共形薄层，导致几何参数相似但表面材料不同的样品。NPA-bSs 的形态特征证实了与目标氧化物的存在相关的孔径减少了约 35%，而化学表面分析允许估计覆盖层的纯度和厚度。此外，ALD 功能化还根据可见光和近红外区域的透射率和光谱椭偏测量结果修改光学（带隙、折射率和介电常数），以及 NPA-bSs 的电解质扩散传输参数（有效固定电荷、离子传输数或离子渗透选择性），这两者都取决于涂层的性质。因此，证明了 ALD 技术对纳米多孔结构的几何和功能修饰的适用性，从而扩大了这些 NPA-bSs 平台在光学传感、纳米光子学、生物传感、微流体或药物递送应用中的潜在应用。