In Situ Polymerization of Vinyl-Functionalized Perovskite for Polarity-Switching Photoelectrochemical Enantioselective Sensing

Sensitive detection and enantioselective discrimination of chiral molecules remain significant challenges in the field of sensing. Herein, we present a polarity-switching photoelectrochemical (PEC) sensing platform based on the in situ polymerization of vinyl-functionalized perovskite for highly sensitive enantioselective detection of l-/d-cysteine (l-/d-Cys). Vinyl-functionalized FAPbI₃ (Vl-FAPbI₃) perovskite was synthesized by replacing conventional oleic acid and oleamide ligands with polymerizable methacrylate monomers, introducing vinyl groups for polymerizable functionality. During sensing, enantioselective binding of 2-bromoisobutyryl bromide-modified β-cyclodextrin (Br-CD) to surface-immobilized l-/d-Cys initiated atom transfer radical polymerization (ATRP) of Vl-FAPbI₃ to different extents, producing enantiomer-specific interfaces (Au-CdS/l-Cys/Br-CD/pVl-FAPbI₃ vs Au-CdS/d-Cys/Br-CD/pVl-FAPbI₃). The polymerization simultaneously enhanced the perovskite stability and amplified the PEC output, ultimately inducing enantiomer-dependent polarity-switching behaviors. The platform exhibited wide linear ranges for l-Cys and d-Cys (10^-2-10⁵ nM) and low detection limits of 3.8 pM and 5.7 pM, respectively. Notably, within the concentration range of 60-200 pM, l-Cys and d-Cys produced opposite photocurrent polarities, thereby enabling intuitive discrimination of molecular chirality. The polarity-switching behavior further offered a straightforward indicator for distinguishing pure samples from mixed ones. This work suggested a unique and generalizable polarity-switching PEC sensing strategy that couples polymerization-driven perovskite stabilization with signal amplification, converting subtle enantiomeric differences into intuitively distinguishable PEC outputs for highly sensitive enantioselective analysis.