Synthesis of ZnO in PVA media: Expanding the applicability of ZnO toward lighting

Abstract Zinc oxide nanoparticles were successfully synthesized in poly(vinyl alcohol) (PVA) media using a modified coprecipitation method and a green chemistry approach. Single-phase ZnO samples with wurtzite structure were formed already at 400°C. The polymer media forms agglomerating clouds around the ZnO nanoparticles. Average nanoparticle size has a tendency to decrease with the PVA content. Visible photoluminescence and radioluminescence emission spectra of the pure ZnO and ZnO- x PVA revealed strong differences. The spectra of pure ZnO samples contain components at 385 and 510 nm corresponded to excitonic and defect-related emission, respectively. Spectra of the ZnO-xPVA samples are dominated by a band peaked in the red spectral region. This band consists of two components at 630 and 720 nm that are assigned to recombination transitions from Zn i and H i to O i defect energy levels, respectively. These results demonstrate that luminescence of ZnO can be tailored by manipulating defect configurations, even without high-temperature processing. Graphical abstract Impact statement The work is devoted to the development of green chemistry principles for synthesis of visible light-emitting ZnO nanoparticles. The ZnO samples were obtained in poly(vinyl alcohol) (PVA) media and characterized by SEM, PXRD, FTIR, radio- and photoluminescence spectroscopy for the first time. The obtained nanoparticles exhibit intense luminescence in the visible range. Emission spectra of the pure ZnO and ZnO- x PVA samples revealed different luminescence properties. The spectra of pure ZnO samples contain narrow band at 385 nm and broad band peaking at 510 nm. These emission bands correspond to the well-known excitonic emission and to defect-related electronic transitions in ZnO crystal structure, respectively. Spectra of the ZnO- x PVA samples are dominated by a band peaking in the red spectral region. It was found that this band consists of two components at 630 and 720 nm which are assigned to recombination transitions from interstitial zinc and hydrogen to interstitial oxygen defect states, respectively. These results demonstrate that the luminescence of ZnO can be tailored by manipulating defect configurations, even without high-temperature processing, and the use of green chemistry principles not only ensures the economically efficient approach to synthesis, but also contributes to the engineering of spectral properties of the luminescent materials.