The use of pulsed laser deposited seed layers for the aqueous solution growth of highly oriented ZnO nanowires on sapphire substrates at 95°C: Study of their photocatalytic activity in terms of octadecanoic (stearic) acid degradation

• Published in: Applied catalysis. A, General Vol. 467; pp. 559 - 567
• Main Authors: Kenanakis, G., Pervolaraki, M., Giapintzakis, J., Katsarakis, N.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 02.10.2013; Elsevier
• Subjects: Aqueous solution growth; Catalysis; Chemistry; Degradation; Deposition; Exact sciences and technology; General and physical chemistry; Nanowires; Octadecanoic acid; Photocatalysis; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Pulsed laser deposition; Sapphire; Seed layer; Seeds; Stearic acid; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zinc oxide; ZnO; Seed layer; Aqueous solution growth; Photocatalysis; Pulsed laser deposition; ZnO; Nanowires; Stearic acid; Octadecanoic acid; Binary compound; Growth; Laser deposition; Degradation; Substrate; Heterogeneous catalysis; Carboxylic acid; Saturated fatty acid; Pulsed laser; Aqueous solution
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2013.07.040

•Highly c-axis oriented ZnO nanowires were grown 95°C.•ZnO seed layers deposited by PLD at 400–700°C were used as substrates.•The photocatalytic degradation of stearic acid was studied upon UV-A irradiation.•ZnO nanowires show very good photocatalytic activity reaching 85% at 30min. The photocatalytic activity of ZnO nanowires grown via an aqueous solution approach at 95°C onto sapphire substrates, which were first pre-coated with ZnO seed layers deposited by pulsed laser deposition at various temperatures (400–700°C), was investigated against the degradation of octadecanoic (stearic) acid under UV-A light illumination. The crystallinity of the ZnO seed layers, as well as their growth orientation along the c-axis, increases with deposition temperature. All chemically grown ZnO samples show narrower (002) reflections with significantly higher intensity than the seed layers deposited by pulsed laser deposition. The grain size, as well as the seed layer roughness, gradually increases with substrate deposition temperature. The nanowires’ diameter also rises with seed layer's deposition temperature, ranging from ∼40±15nm for 400°C to ∼155±65nm for 700°C. The chemically grown ZnO nanowires exhibit relatively high transmittance values, especially those grown on sapphire substrates, which were pre-coated with seed layers deposited by pulsed laser deposition at 400 and 500°C. All ZnO samples, including seed layers and nanowires’ arrays, show very good photocatalytic activity regarding the degradation of octadecanoic (stearic) acid under UV-A light exposure. In specific, the photocatalytic activity of ZnO nanowires’ arrays grown on top of a seed layer deposited by pulsed laser deposition at 600°C is quite remarkable, showing the highest stearic acid disappearance rate, i.e., 4.22×10−8mol/min (formal quantum efficiency=4.48×10−3) at 30min of UV-A light illumination.