## 2 Results and Discussion
These results show that the morphology of PS@TPEE fluorescent microspheres can be changed from monodisperse and spherical to apple-shaped by changing the amount of crosslinking agent, which is a facile and versatile platform to synthesize PS@TPEE fluorescent microspheres with controlled morphologies. Figure 3 shows the SEM images of the PS@TPEE fluorescent microspheres prepared with different amounts ofTPEE. As shown in Figure 3, the synthesized PS@TPEE fluorescent microspheres are non-spherical with heterogeneous structures. When the amount ofTPEE was 1-3 wt% of the weight of styrene monomer, the synthesized microspheres were apple-shaped. With the addition ofTPEE increased from 4 wt% to 5 wt%, the morphology of the synthesized fluorescent microspheres changed to red blood cell (RBC)-like morphology. This may be due to the addition ofTPEE, the critical chain length of the synthesized P(St-TPEE-DVB) polymer becoming shorter, and the rapid precipitation in the dispersion polymerization system. The precipitated P (St-TPEE-DVB) nucleus moved to the surface of the grown PS@TPEE fluorescent particles to form a crosslinked network. Unreacted monomers tend to diffuse into the PS@TPEE fluorescent particles. Therefore, the incompatibility between the monomer and the newly formed crosslinked network led to the phase separation, which resulted in the formation of RBC-like morphology [60]. When the addition ofTPEE was greater than 6%, the synthesized P (St-TPEE-DVB) polymer nucleated quickly, resulting in a change in the nucleation position of P (St-TPEE-DVB), which was conducive to the formation of a uniform crosslinked network. Accordingly, the microsphere morphologies changed from RBC-like morphology to apple-shaped morphology [61]. Figure 2: SEM images of PS@TPEE fluorescent microspheres prepared with different amounts of DVB (relative to St): (**a**) 0 wt%, (**b**) 0.5 wt%, (**c**) 1 wt%, (**d**) 2 wt%, (**e**) 3 wt%, (**f**) 5 wt%, (**g**) 8 wt%, (**h**) 10 wt%, (**i**) 12 wt%. Other reaction parameters: St (2.0 g), AIBN (0.04 g), TPEE (0.02 g), DMC (0.02 g), reaction medium ethanol–water (14.4 g/3.6 g, 80:20, \(w/w\)). To explore the relationship between the fluorescence intensity of PS@TPEE microspheres and the content of fluorescent monomer TPEE, PS@TPEE fluorescent microsphere: (**a**) 1 wt%, (**b**) 2 wt%, (**c**) 3 wt%, (**d**) 4 wt%, (**e**) 5 wt%, (**f**) 6 wt%. Other reaction parameters: St(2.00 g), AIBN (0.04 g), DMC (0.02 g), DVB (0.02 g), reaction medium ethanol-water (14.4 g/3.6 g, 80:20, \(w/w\)). In addition, to investigate whether the fluorescence of the synthesized fluorescence microspheres is homogeneous, laser confocal microscopy was used for observations. As shown in Figure 4c, by observing the darkfield fluorescence map,  
Figure 4: (**a**) Photo of an aqueous solution of PS@TPEE fluorescent microspheres with different amounts of TPEE under ultraviolet irradiation (The TPEE content was 0%, 1%, 2%, 4%, 6%, 8%, 10%, and 12% from left to right, \(\lambda\)ex = 365 nm). (**b**) PL spectra of PS@TPEE fluorescent microspheres at different amounts of TPEE. (**c**) Images of PS@TPEE fluorescent microspheres under a laser confocal microscope (from left to right (a–c) are darkfield fluorescence map, brightfield image, and brightfield fluorescence map). (**d**) Images of PS@TPEE fluorescent microspheres of various morphologies observed under a laser confocal microscope. Figure 3: SEM images of PS@TPEE fluorescent microspheres prepared with different amounts of TPEE: (**a**) 1 wt%, (**b**) 2 wt%, (**c**) 3 wt%, (**d**) 4 wt%, (**e**) 5 wt%, (**f**) 6 wt%. Other reaction parameters: St(2.00 g), AIBN (0.04 g), DMC (0.02 g), DVB (0.02 g), reaction medium ethanol–water (14.4 g/3.6 g, 80:20, \(w/w\)). brightfield fluorescence map taken by laser confocal microscopy, it can be seen that each microsphere has fluorescence, which intuitively proves the good monodispersity of the synthesized PS@TPEE fluorescent microspheres.