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In recent years, most of the dedication to waste recycling and upcycling has been focused on plastic polymers. There is less development in utilizing discarded iron or aluminum cans for upcycling. In this study, we aim to prepare anodic aluminum oxide membranes from the top of discarded aluminum cans (T-AAO) and from the side of discarded aluminum cans (S-AAO) and demonstrate their application values. The T-AAO and S-AAO membranes are obtained by anodically oxidizing the top and the side of discarded aluminum cans separately, and the pore sizes of both membranes can be enlarged by using 5 wt % phosphoric acid with different pore-widening times. The physical, chemical, and morphological properties of T-AAO and S-AAO membranes are analyzed by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), thermogravimetric analysis (TGA), X-ray diffraction (XRD) (wide-angle X-ray scattering (WAXS) and grazing-incidence wide-angle X-ray (GIWAX)), X-ray fluorescence (XRF), electron backscatter diffraction (EBSD), and contact angle measurement, and the properties are also compared with those of AAO membranes made by high-purity (99.997%) aluminum sheets. The thermal annealing method is also applied to aluminum cans for fabricating more stereoscopic AAO membranes attributed to changes of primary lattice planes. One of the application values of T-AAO and S-AAO membranes is demonstrated by infiltration of polymer materials, poly-(methyl methacrylate) (PMMA) and polystyrene (PS), into the nanopores of the membranes with the thermal annealing method, followed by releasing the polymer nanoarrays from the T-AAO and S-AAO membranes with NaOH solutions. Moreover, functional self-cleaning surfaces of T-AAO and S-AAO membranes are produced by grafting hydrophobic octadecyltrimethoxysilane (OTMS) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) molecules. This work not only provides a feasible approach to recycle and upcycle aluminum waste but also gives a promising strategy for fabricating widely applicable nanomaterials in eco-friendly and low-cost ways. [ABSTRACT FROM AUTHOR]

Over the past few decades, stimuli-responsive materials have been widely applied to porous surfaces. Permeability and conductivity control of ions confined in nanochannels modified with stimuli-responsive materials, however, have been less investigated. In this work, the permeability and conductivity control of ions confined in nanochannels of anodic aluminum oxide (AAO) templates modified with thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes are demonstrated. By surface-initiated atom transfer radical polymerization (SI-ATRP), PNIPAM brushes are successfully grafted onto the hexagonally packed cylindrical nanopores of AAO templates. The surface hydrophilicities of the membranes can be reversibly altered because of the lower critical solution temperature (LCST) behavior of the PNIPAM polymer brushes. From electrochemical impedance spectroscopy (EIS) analysis, the temperature-gating behaviors of the AAO-g-PNIPAM membranes exhibit larger impedance changes than those of the pure AAO membranes at higher temperatures because of the aggregation of the grafted PNIPAM chains. The reversible surface properties caused by the extended and collapsed states of the polymer chains are also demonstrated by dye release tests. The smart thermo-gated and ion-controlled nanoporous membranes are suitable for future smart membrane applications., (© 2023 Wiley-VCH GmbH.)