High-Stability Printable Perovskite SERS Substrates in an Aqueous Environment via Plasmon-Induced Resonance Energy Transfer

The excellent photoelectric conversion efficiency and tunable bandgap of metal halide perovskites make them highly suitable for SERS applications. However, the low stability of perovskites in water and oxygen greatly hinders their use in SERS detection, particularly in biomolecule detection applications, which often require water-based test solutions. Herein, we report a gold (Au)/perovskite-polyvinylidene difluoride (PVDF) nanocomposite/ZnO nanoflower (GPPZ) SERS substrate capable of functioning in aqueous solutions. Its enhancement ability is attributed to plasmon-induced resonance energy transfer (PIRET) and an electromagnetic mechanism. The surface plasmon resonance created by ultrathin Au and ZnO nanoflowers induces resonance energy transfers to the perovskite via PIRET, facilitating a quasi-matched charge transfer between the perovskite and the probe molecule. The PVDF coating protects the perovskite from water and oxygen without affecting the resonance energy-transfer process. As a result, an enhancement factor (EF) approaching 1 × 10⁶ was achieved for the crystal violet molecule. Additionally, we fabricated a flexible GPPZ substrate using silk screen printing, enabling mass production of an SERS array substrate. The printed flexible GPPZ substrates demonstrated micromole-level cysteine detection with an EF of 6.8 × 10⁵, showing potential for application in hyperhomocysteinemia diagnosis.