Water-ultrastable perovskite CsPbBr₃ nanocrystals tailored by surface-confined strategy for amaranth sensing in food samples

A vital challenge is to develop water-stable perovskite nanocrystals owing to the easy attack of its surface vacancy defects by water-molecule. Here, a facile surface-passivated strategy to dramatically improve the chem-stability and luminescent efficiency (LE) of the CsPbBr₃ nanocrystals (CPB) is proposed, where sodium dodecyl sulfate (SDS) encapsulate on CPB, generating confined environment (named SDS@CPB). The flexible long carbon-chain of SDS can confine the movement of CPB to form an externally hydrophobic closed-shell and internally structural rigidity through the hydrophobic association between surface hydrophobic groups, improving the LE and maintaining long-term composition of CPB. While the sulfate group in SDS can reduce the surface-defects exposure of CPB through the coordination with Pb²⁺, inhibiting the invasion of water-molecule. Importantly, an SDS@CPB-based sensor was fabricated to detect amaranth in food samples with a lower detection limit (5.43 nM), which opens a new avenue for food sensing based on high-efficiency perovskite nanocrystals.