Synthesis of TiO₂/Al₂O₃ Double-Layer Inverse Opal by Thermal and Plasma-Assisted Atomic Layer Deposition for Photocatalytic Applications.

Content Provider	Europe PMC
Author	Lemago, Hamsasew Hankebo Addin, Feras Shugaa Kárajz, Dániel Atilla Igricz, Tamás Parditka, Bence Erdélyi, Zoltán Hessz, Dóra Szilágyi, Imre Miklós
Editor	Zhu, Shenmin
Copyright Year	2023
Abstract	In comparison to conventional nano-infiltration approaches, the atomic layer deposition (ALD) technology exhibits greater potential in the fabrication of inverse opals (IOs) for photocatalysts. In this study, TiO2 IO and ultra-thin films of Al2O3 on IO were successfully deposited using thermal or plasma-assisted ALD and vertical layer deposition from a polystyrene (PS) opal template. SEM/EDX, XRD, Raman, TG/DTG/DTA-MS, PL spectroscopy, and UV Vis spectroscopy were used for the characterization of the nanocomposites. The results showed that the highly ordered opal crystal microstructure had a face-centered cubic (FCC) orientation. The proposed annealing temperature efficiently removed the template, leaving the anatase phase IO, which provided a small contraction in the spheres. In comparison to TiO2/Al2O3 plasma ALD, TiO2/Al2O3 thermal ALD has a better interfacial charge interaction of photoexcited electron–hole pairs in the valence band hole to restrain recombination, resulting in a broad spectrum with a peak in the green region. This was demonstrated by PL. Strong absorption bands were also found in the UV regions, including increased absorption due to slow photons and a narrow optical band gap in the visible region. The results from the photocatalytic activity of the samples show decolorization rates of 35.4%, 24.7%, and 14.8%, for TiO2, TiO2/Al2O3 thermal, and TiO2/Al2O3 plasma IO ALD samples, respectively. Our results showed that ultra-thin amorphous ALD-grown Al2O3 layers have considerable photocatalytic activity. The Al2O3 thin film grown by thermal ALD has a more ordered structure compared to the one prepared by plasma ALD, which explains its higher photocatalytic activity. The declined photocatalytic activity of the combined layers was observed due to the reduced electron tunneling effect resulting from the thinness of Al2O3.
Journal	Nanomaterials (Basel, Switzerland)
Volume Number	13
PubMed Central reference number	PMC10141218
Issue Number	8
PubMed reference number	37110896
e-ISSN	20794991
DOI	10.3390/nano13081314
Language	English
Publisher	MDPI
Publisher Date	2023-04-08
Access Restriction	Open
Rights License	Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). © 2023 by the authors.
Subject Keyword	inverse opal TiO2 Al2O3 nanocomposites thermal ALD plasma ALD photocatalysis
Content Type	Text
Resource Type	Article
Subject	Chemical Engineering Materials Science