## 3 Results and Discussion
### Characterization and Optical Properties of Nanophosphor  
In order to separate these small-sized and nano-sized phosphors from the surface of the block, after solvent-thermal reaction, the phosphors were further processed by ultrasonication and centrifugation. The scanning electron microscope images showed that the small-sized phosphors were relatively uniform in size, numerous, and with a greatly reduced particle size (Figure 8a). The powders were in the form of clusters, similar to coral structures, and were all similar to coral structures (Figure 8b,c). The average length of the needle-like structure on the coral structure was about 568 nm, and the average diameter was about 63 nm, while the average length of the lamellar structure was about 300 nm (Figure 8d). At the same time, the length and diameter of the separated and extracted needle phosphors were less than 100 nm, and the morphology was approximately the same (Figure 8e). This indicates that the uniform size of the nanofluorescent needles can be extracted by solvent heat. The surface of the bulk phosphor after the isolation of the nanospecific morphology was rough and covered with grooves (Figure 8f), which was  
Figure 7: Scanning electron microscopy (SEM) images of surface morphology change of bulk phosphor after solvent thermal reaction with different reaction times. (**a**) Untreated commercial phosphor; (**b**) 4 h; (**c**) 12 h; (**d**) 18 h; (**e**) 24 h; (**f**) 48 h.  
similar to the morphology at 12 h of reaction (Figure 7c), which can be added to prove that the small-sized special morphology was reattached and agglomerated on the surface of the bulk powder in the middle and late stages of the reaction. During the previous experiments, after the operations of ultrasonication and centrifugation, the submicron-size and nanosize phosphors in the products were extracted, which had needle-like morphology with some flake-like morphology. In the XRD spectrum (Figure 9a), the monoclinic diffraction peaks of the small-sized phosphors were dominant, similar to those of the commercial SAOED before the reaction. It indicates that the crystal structure of the nanophosphor was not destroyed after treatment, but the summit appears broadened, which was due to the small size effect of the particles. The EDS spectra (see Figure 9b) further confirmed the chemical composition of the final products. The mass and atomic ratios of the elements of the untreated bulk and nanopowder phosphors conform to the stoichiometric formula of SrAl2O4. Wide XPS spectra showed (Figure 9c) the presence of Sr (3s, 3p, 3d), Al (2s, 2p), O1s, and C1s peaks in the spectra, suggesting that the extracted product consisted of the elements strontium, aluminum, and oxygen. The results of the XPS analyses indicated that the composition of the nanophosphors was essentially the same as that of the untreated commercial bulk phosphor. Figure 8: Scanning electron microscopy (SEM) image of phosphor after ultrasonic dispersion. (**a,b**) Overall morphology of block phosphor. (**c,d**) Surface morphology of block phosphor. (**e**) Needle phosphor extracted by ultrasound. (**f**) Block phosphor after extraction of needle phosphor. HRTEM images taken of the nanofluorescent powders were adjacent to their lattice plane spacing of 0.3115 nm, corresponding to the (\(-2\) 1 1) crystal plane of JCPDS standard card No. 34-0379 (Figure 9d). Transmission electron microscopy (Figure 9e-g) and AFM analysis (Figure 9h,i) observations showed that the product nanopins or nanosheets (PLNSs) were very thin, and the nanopins were well dispersed, whereas most of the PLNSs were in the form of irregular flakes and prone to agglomeration, with an average particle size of 86 nm and an average thickness of about 15 nm. To demonstrate the feasibility of preparing nano-sized phosphor through this experiment, we extracted the nano phosphor from the original commercial bulk phosphor and compared its weight with that of the phosphor obtained in this experiment.