Blue Photoluminescence and Cyan-Colored Afterglow of Undoped SrSO(4) Nanoplates

[Image: see text] Undoped SrSO(4) nanoplates were synthesized via the composite hydroxide-mediated approach. The products were characterized by means of X-ray diffractometry, scanning electron microscopy, X-ray energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, photoluminescence (PL) spectroscopy, electron spin resonance technique, afterglow spectroscopy, and thermoluminescence dosimetry. The steady-state PL spectrum of undoped SrSO(4) nanoplates can be deconvoluted into two distinct Gaussian bands centered at 2.97 eV (417.2 nm) and 2.56 eV (484.4 nm), respectively. The nature of the defect emissions is confirmed through the emission-wavelength-dependent PL decays as well as the excitation-wavelength-dependent PL decays. A cyan-colored afterglow from undoped SrSO(4) nanoplates can be observed with naked eyes in the dark, and the afterglow spectrum of the undoped SrSO(4) nanoplates exhibits a peak at about 492 nm (2.52 eV). The duration of the afterglow is measured to be 16 s. The thermoluminescence glow curve of the undoped SrSO(4) nanoplates shows a peak at about 40.1 °C. The trapping parameters are determined with the peak shape method, the calculated value of the trap depth is 0.918 eV, and the frequency factor is 1.2 × 10(14) s(–1). Using density functional calculations, the band structures and densities of states of oxygen-deficient SrSO(4) and strontium-deficient SrSO(4) are presented. The mechanisms of the cyan-colored afterglow are discussed for undoped SrSO(4), and the oxygen vacancies in SrSO(4) are proposed to be the luminescence center of the afterglow.