High-performance silica-coated Cs₃Sb₂Br₉ as a novel fluorescent probe for the detection of o-nitrophenol

Lead-free antimony halides have emerged as promising candidates for optoelectronic applications due to their low toxicity and unique electronic structures. However, achieving high photoluminescence quantum yield (PLQY) and environmental stability remains a significant challenge. In this work, we report the synthesis of highly stable and luminescent Cs₃Sb₂Br₉@TMOS microstructures via an in-situ encapsulation strategy assisted by tetramethyl orthosilicate (TMOS). Spectroscopic analyses confirm the formation of Sb-O-Si interfacial bonds, which effectively suppress non-radiative recombination with an enhanced absolute PLQY from 6.3% to 29.6%. Furthermore, the Cs₃Sb₂Br₉@TMOS was utilized as a fluorescent probe for the sensitive and selective detection of o-nitrophenol (o-NP) in the range of 0–19 μM. Our results demonstrate that the quenching process is governed by a synergistic combination of dominant static quenching, the inner filter effect (IFE), and photoinduced electron transfer (PET). This work provides an effective approach for developing lead-free perovskite-based sensors for practical environmental monitoring.