APTES-Assisted In Situ Growth of CsPbBr3 in PVDF Nanofibers via Interfacial Ionic-Dipole Interactions for Enhanced Piezoelectric Performance

Poly(vinylidene fluoride) (PVDF)-based piezoelectric materials are commonly constrained by low polar-phase content. Here, we report an APTES-assisted in situ crystallization strategy to fabricate PVDF/APTES@CsPbBr3 nanocomposites. APTES acts as a bifunctional linker that passivates CsPbBr3 quantum dot surfaces while introducing protonated ammonium (−NH3+) groups. When incorporated into electrospun PVDF fibers, these -NH3+ groups interact with fluorine atoms of PVDF chains via ionic-dipole interactions, as evidenced by a blue shift of the C–F stretching band in Fourier-transform infrared (FT-IR). This molecular-level interaction lowers the free energy barrier for polar phase nucleation, promoting the transformation from nonpolar α phase to electroactive β phase, as confirmed by X-ray diffraction (XRD), FT-IR, and differential scanning calorimetry (DSC). The optimized composite achieves a markedly higher β-phase fraction compared to pure PVDF and unmodified CsPbBr3 composites. As a functional demonstration, the material delivers substantially enhanced piezoelectric output (130 V) and operates as a self-powered motion sensor. When coupled with a support vector machine classifier, the system achieves high-accuracy recognition (94.6%) of diverse human activities. This work establishes APTES-mediated interfacial engineering as a versatile platform for controlling polymer crystallization in hybrid systems toward high-performance piezoelectric applications, with the output enhancement attributed to a synergistic combination of increased β-phase fraction, intrinsic piezoelectricity of the perovskite fillers, improved interfacial stress transfer, and refined fiber morphology.