## 3 Results and Discussion
### Characterization and Optical Properties of Nanophosphor
The experiment demonstrates that the weight of the nano phosphor in the pristine bulk phosphor was 0.2675 g, while the weight of the nano phosphor obtained by solvent heat treatment was 0.8314 g. This confirms the successful preparation of the nano phosphor with a yield of 5.64%. Temperature-dependent emission spectra were carried out for the product nanofluorescent powder at 45 Kintervals between 100 and 460 K with xenon excitation (Figure 10a). In the emission spectrum, two bands were observed at 440 to 525 nm. This is due to the presence of two sites available for Sr\({}^{2+}\) ions in monoclinic crystalline SAOED, and both sites occur in the same number in the lattice [40]. The emission intensity at shorter wavelengths is slightly lower due to energy transfer. At room temperature, the emission at 445 nm  
Figure 9: (a) X-ray diffraction (XRD) spectra of the nanophosphor; (b) energy dispersive analysis (EDS) spectra of the nanophosphor; (c) X-ray photoelectron spectroscopy (XPS) spectra of the nanophosphor; (d) lattice fringes of the nanophosphor (insets are diffractograms); (e–g) HRTEM images of the nanophosphor; (h,i) atomic force microscopy (AFM) images of the nanophosphor. was quenched, and only the longer wavelength emission was observed. However, in the present work, the emission spectra show a blue shift with increasing temperature. The reason for this may be that at higher temperatures, more electrons were populated on the high-energy excited state subenergy levels, but the non-radiative leaps at the intersection of excited and ground states in the configuration coordinate diagram were reduced. As a result, the intensity of the high-energy emission peaks increased, and the intensity of the low-energy emission peaks decreased. Also, due to the convolution of the peaks, the blue-shifted behavior was observed with increasing temperature. Due to the electron-phonon interaction between the ground and excited states of the luminescent center at high temperatures, the emission intensity decreases with increasing temperature. It was assumed that the non-emissivity \(\mathrm{k_{nr}}\) can be expressed as [41]  
\[\mathrm{K_{nr}}=\mathrm{Aexp}(-\Delta\mathrm{E}/\mathrm{kT}) \tag{1}\]  
where A is a constant, k is the Boltzmann constant, and \(\Delta\mathrm{E}\) is the activation energy of the thermal quenching process. Therefore, the emission intensity decreases as the probability  
Figure 10: (**a**) Variable temperature emission spectrum. (**b**) Temperature-dependent emission intensity in the range of 325–460 K. (**c**) Quantum efficiency plot. (**d**) Emission spectrum. (**e**) Room temperature afterglow decay curve. (**f**) Variable temperature phosphorescence emission spectroscopy. (**g**) Afterglow intensity at different temperatures. of non-radiative jump increases with increasing temperature. From Equation (1), the lower the value of \(\Delta\)E, the faster the non-radiative rate at a given temperature [42]. In addition, the Arrhenius equation can be used to characterize the temperature quenching of the study [43]. \[\text{I}(\text{T})=\text{I}_{0}/[1+\text{C}\text{exp}(-\Delta\text{E}/\text{kT })] \tag{2}\]  
where \(\text{I}_{0}\) and \(\text{I}(\text{T})\) are the initial intensity and the intensity at a given temperature T, respectively, and C is a constant. Comparing the emission intensities (Figure 10b) with temperature in the range of 325 to 460 K, the \(\Delta\)E of commercial SAOED and nanophosphor were obtained as 0.067 and 0.061 eV, respectively, and there was no doubt that the activation energies of unreacted commercial SAOED were higher than that of the nanophosphor, which suggests that the latter's thermal stability has been improved while being more sensitive to thermal effects. In order to visualize the optical strength of the two, the phosphor quantum efficiency test was performed by exciting the phosphor at 370 nm (Figure 10c). The quantum efficiency is the ratio of the number of photons produced per second by the phosphor to the number of incident quanta at a particular wavelength.