title: Superior Photostability and Photocatalytic Activity of ZnO Nanoparticles Coated with Ultrathin TiO2 Layers through Atomic-Layer Deposition.
abstract: Atomic-layer deposition (ALD) is a thin-film growth technology that allows for conformal growth of thin films with atomic-level control over their thickness. Although ALD is successful in the semiconductor manufacturing industry, its feasibility for nanoparticle coating has been less explored. Herein, the ALD coating of TiO2 layers on ZnO nanoparticles by employing a specialized rotary reactor is demonstrated. The photocatalytic activity and photostability of ZnO nanoparticles coated with TiO2 layers by ALD and chemical methods were examined by the photodegradation of Rhodamine B dye under UV irradiation. Even though the photocatalytic activity of the presynthesized ZnO nanoparticles is higher than that of commercial P25 TiO2 nanoparticles, their activity tends to decline due to severe photocorrosion. The chemically synthesized TiO2 coating layer on ZnO resulted in severely declined photoactivity despite the improved photostability. However, ultrathin and conformal ALD TiO2 coatings (≈ 0.75-1.5 nm) on ZnO improved its photostability without degradation of photocatalytic activity. Surprisingly, the photostability is comparable to that of pure TiO2, and the photocatalytic activity to that of pure ZnO.
authors.affiliation: Department of Materials Science and Engineering, Hanyang University, Ansan 15588 (Republic of Korea).|Department of Physics, National Institute of Technology Karnataka, Surathkal, P.O. Srinivasnagar, Mangaluru 575025 (India).
authors.forename: Kishore
authors.initials: K
authors.lastname: Sridharan
authors.affiliation: Department of Advanced Materials Engineering, Hanyang University, Ansan 15588 (Republic of Korea).
authors.forename: Eunyong
authors.initials: E
authors.lastname: Jang
authors.affiliation: R&D Center, Samsung Electronics Co. Ltd., Suwon 443-742 (Republic of Korea).
authors.forename: Young Min
authors.initials: YM
authors.lastname: Park
authors.affiliation: Department of Materials Science and Engineering, Hanyang University, Ansan 15588 (Republic of Korea). tjp@hanyang.ac.kr.|Department of Advanced Materials Engineering, Hanyang University, Ansan 15588 (Republic of Korea). tjp@hanyang.ac.kr.
authors.forename: Tae Joo
authors.initials: TJ
authors.lastname: Park
keywords: atomic-layer-deposition; core-shell structures; nanoparticles; photochemistry; rotary ALD