2.1. Synthesis and Characterization of the Compact-Discrete MANP.
The fabrication of MANP involved a one-pot emulsification and evaporation method, where superparamagnetic Fe3O4 NPs@OA (Figure S1 ) and red-emitting AIEgens (Figure S2 ) were co-assembled as functional units, along with poly(maleicanhydride-alt-1-octadecene) (PMAO) polymer as the supporting skeleton. In this process, 6 mg of hydrophobic Fe3O4 NPs@OA, 6 mg of AIEgens, and 5 mg of PMAO were dissolved in chloroform and underwent micellar encapsulation in an aqueous phase using sodium dodecyl sulfate (SDS) as a surfactant. During the evaporation of chloroform, the components (Fe3O4 NPs@OA, AIEgens, and PMAO) self-assembled and co-constructed a spherical nanocomposite called MANP6:6. Scanning electron microscopy (SEM) image (Figure 1 a) and transmission electron microscopy (TEM) image (Figure 1 b) demonstrate the homogeneous spherical morphology of MANP6:6. The magnified TEM image (Figure1 c) clearly shows a core–shell nanostructure with a compact AIE core and a discretely packed Fe3O4NPs@OA shell, indicating a phase separation process within MANP6:6 due to the different polarities of the building blocks. By contrast, PMAO polymer nanoparticles (PNP), AIE nanoparticles (ANP6), and magnetic nanoparticles (MNP6) were synthesized as single functional component analogs. TEM image inFigure 1 d reveals the solid spherical structure of PNP. However, ANP6 displays a distinct AIE core-PMAO shell structure due to the polarity difference between AIEgens and the polymer (Figure 1 e). Figure 1 f shows that MNP6 exhibits a spherical geometry with Fe3O4 NPs@OA homogeneously distributed throughout the nanoparticle, owing to the high compatibility between OA and PMAO. These results support the reasonable formation mechanism of MANP: (i) the high mutual affinity between OA, PMAO, and SDS leads to the uniform assembly of Fe3O4 NPs@OA on the exterior PMAO shell, close to the SDS aqueous phase, with a discrete distribution; (ii) the aromatic AIEgens tend to migrate to the particle center and aggregate together due to their incompatible molecular affinity with the shell components.
Furthermore, Figure 1 g shows that MANP6:6 exhibits the characteristic UV–vis spectrum of ANP6 and demonstrates an absorption lift in the 200–600 nm range due to the incorporation of the magnetic component. By contrast, PNP exhibits negligible light absorption, indicating that the polymer matrix does not contribute to optical interference in MANP6:6. The energy dispersive X-ray (EDX) elemental mapping images display the distribution of C, Fe, O, and S in MANP6:6. Figure 1 h shows that the C elements are primarily concentrated in the core position, Fe and O elements are located on the exterior shell, and S elements are uniformly distributed throughout MANP6:6. Further EDX line scan (Figure 1 i) across the center of MANP6:6 confirms the presence of a nuclear C core and an out-layer Fe, verifying the distinct assembling spatiality of Fe3O4 NPs@OA and AIEgens in the core–shell magnetic-fluorescent MANP6:6. X-ray photoelectron spectroscopy (XPS) analysis (Figures 1 j, k,Figure S3 ) implies the co-existence of C, O, and Fe in MANP6:6. In addition, the powder X-ray diffraction (XRD) analysis (Figure 1 l) reveals characteristic diffraction peaks corresponding to the (220), (311), (400), (511), and (440) planes of superparamagnetic Fe3O4crystal, suggesting the successful loading of Fe3O4 NPs@OA in MANP6:6. Dynamic light scattering measurements show that MANP6:6is well-monodispersed with a uniform hydrodynamic size of ~320 nm (Figure 1 m). Moreover, the surface of MANP6:6 becomes predominantly negatively charged after the carboxylation process, which is beneficial for subsequent biomodification (Figure 1 n). The fluorescent spectra demonstrate that MANP6:6 exhibits maximum excitation wavelengths at 365 and 465 nm, with a maximum emission peak at 600 nm (Figure S4 ). This red-light emitter property enables MANP6:6 to effectively resist biological interference. Collectively, these results provide strong evidence for the successful construction of MANP.