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Nanocrystals of Cs3Cu2I5, a metal halide with promising potential as a perovskite substitute, are successfully grown on graphene nanosheets. An intermediate stage of physically exfoliated graphene nanosheets, concurrent with the formation of copper‐based seeds on graphene surface, is developed, for the first time, allowing for the subsequent growth of Cs3Cu2I5 nanocrystals (CsNCs) to obtain CsNCs‐decorated graphene nanohybrids (CsGNHs). The morphology and properties of the CsGNHs depend on the input amount of graphene nanosheets during the reaction. The photoluminescence intensity of the CsGNHs decreases with increasing graphene content, indicating that graphene facilitates nonradiative energy transfer from the CsNCs in the CsGNHs. The inherent self‐trapping exciton emission of the CsNCs is also affected by the graphene substrate. As the graphene content increases, the emission peaks of the CsGNHs broaden and diminish. The CsGNHs emit a stable solid‐state luminescence with a large Stokes shift (zero self‐absorption) under a high‐energy ultraviolet (UV) light. Consequently, the CsGNHs can act as optoelectronic transducers and selectively generate a turn‐on photocurrent response under specific‐wavelength UV light. Additionally, a new anticounterfeiting strategy is developed using the CsGNHs as a luminescent black ink to fabricate luminescent quick‐response codes with fake pixels. [ABSTRACT FROM AUTHOR]

Isothiazolinones, which are widely used as chemical additives in many industries, may lead to skin irritation and allergies, thereby adversely influencing human health and the environment. Therefore, this paper proposes an efficient strategy for screening nanohybrid transducers to selectively detect 2-octyl-3-isothiazolinone (OIT) as a representative isothiazolinone. Chemical receptor (CR) candidates consisting of two parts: a reactive imidazole unit and side functional group for covalent conjugation with graphene and noncovalent interaction with the target, respectively, were designed. Five CR structures were selected and synthesized based on density-functional-theory calculations. The synthesized CRs were anchored to graphene for electrochemical transduction. The alkyl groups calculated to have the highest chemical affinities toward OIT were introduced in the CR/graphene nanohybrids (CGNHs). The electrochemical responses of the CGNHs toward OIT depended on the CR type, OIT concentration, and applied potential. Therefore, the combination of five CGNHs as a transducer with different potentials enabled the facile and effective detection of OIT (1–200 mg L–1) from the interferences through principal component analyses. The best CR corresponded to the dodecyloxy group, and the optimal measurement conditions included a scan rate of 25 mV s–1 and applied potentials of −0.75, 0.08, and 1.30 V (vs Ag/AgNO3). The proposed strategy can facilitate the efficient development of nanotransducers for identifying different types of chemical species such as biocides. [ABSTRACT FROM AUTHOR]