Template-free solvothermal synthesis of ZnO nanoparticles with controllable size and their size-dependent optical properties

• Published in: Materials letters 2012, Vol.66 (1), p.318-320
• Main Authors: Lian, Jiabiao, Liang, Yao, Kwong, Fung-luen, Ding, Zhimin, Ng, Dickon H.L.
• Format: Article
• Language: English
• Subjects: absorption; Absorption spectra; Band spectra; Emission; ethanol; Ethyl alcohol; ethylene glycol; Nanoparticles; Optical properties; oxygen; particle size; Quantum confinement; Quantum confinement effect; Semiconductor; Solvothermal synthesis; Stability; surface area; Zinc oxide
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2011.09.007

ZnO nanoparticles (NPs) have been synthesized via a facile and template-free solvothermal method. The size of ZnO NPs could be tailored by adjusting the ratio of ethanol to ethylene glycol (EG). Their structure and morphology have been investigated. The as-prepared samples are monodispersed ZnO NPs with controllable sizes of about 24.2, 18.9 and 14.7 nm. The cathodoluminescence (CL) spectra of the samples show that the relative intensity ratio of the visible emission peak at 500–650 nm to the band-edge UV emission peak at 380 nm increases as the particle size decreases. Sample with smaller crystallites would have larger surface area and more oxygen vacancy defects, thus it exhibits higher visible emission peak. The UV–vis absorption spectrum indicates the band gap variation of the ZnO NPs with their size. Moreover, the size-dependent blue shifts of both the CL emission and the UV–vis absorption spectra reveal the effect of quantum confinement. ► Size-controlled ZnO NPs were synthesized via a template-free solvothermal method. ► The size of NPs could be tailored by adjusting the volume ratio of ethanol to EG. ► Their size-dependent optical properties were investigated in detail.