Femtosecond pulse laser fabrication of zinc oxide quantum clusters/nanoparticles and their electrical, optical, and chemical characteristics

Abstract

Despite various studies on the preparation of different types and sizes of ZnO, the synthesis of quantum clusters of bare metal oxide has rarely been reported. The research goals of this study were to create clusters/nanoparticles using femtosecond laser irradiation to increase the electrical, optical, and chemical functionalities of ZnO. Femtosecond pulse laser irradiation deposition technology was used here to produce ZnO from a precursor in water (pH = 5.5) and aqueous alkaline solution (pH = 10.2). These products were named ZnO(F5.5) and ZnO(F10.2), respectively. In this procedure, Zn ions react with hydroxyl radicals (OH*) produced by the decomposition of water molecules, and Zn(OH*)2 is dehydrated by femtosecond laser energy to create ZnO. The spherical particle size of ZnO(F5.5) after 1–30 min irradiation was found to be small (1–7 nm) compared to that of ZnO(F10.2) spheres (10–13 nm). Furthermore, ZnO(F5.5) shows a larger band gap (5.3–5.6 eV), a longer electron life time (40.4 ms), and a higher emission intensity (483 a.u.) compared to ZnO(F10.2). For the photodegradation of harmful pollutants, ZnO(F5.5) prepared at 1 min of laser irradiation reduces formaldehyde by 98.5% under UV light irradiation for 15 min. However, ZnO(F10.2) and other larger ZnO particles with various shapes require a longer time for formaldehyde conversion. These results confirm that an ultrasmall ZnO nanoparticle (1 nm in size) can be called a quantum cluster and has better electrical, optical, and photocatalyst characteristics. In particular, efficient photocatalytic reactions may be used to study the ecological and environmental impacts of ZnO quantum cluster.