Layer-by-layer assembly of ordered organic–inorganic luminescent film toward sensoring nitrobenzene compound

• Fabrication of colorimetric fluorescent indicator films has been reported.
• The films show a stepwise growth and a layered structure perpendicular to the substrates.
• The films can be used as colorimetric fluorescent chemosensor for vapor NB detection.
• The sensoring films have been extended to two-color luminescence systems.

Luminescent film materials sensitive to pollutions are important to develop new types of optical sensors toward environmental detection. Herein we report organic–inorganic hybrid thin films (TFs) with reversible luminescence response to the volatile nitrobenzene (NB) using layer-by-layer (LBL) assembly of fluorescent brightener CXT and Mg–Al-layered double hydroxide (LDH) nanoparticles. The structural and surface morphology studies show that the TFs are continuous and uniform with stacking order in the normal direction of the substrate. AFM and SEM measurements indicated that the films feature periodic structure with a period of ca. 25 nm as well as uniform surface morphology. Moreover, the CXT/LDH TF displays a high luminescent response as a fast colorimetric chemosensor for NB vapor with a low detection limit (4.02 ppb), good regeneration and high selectivity. In addition, by combining suitable luminescent building blocks, the films can also be extended to other two-color luminescence systems, which exhibit changes in both luminescence intensity and ratiometric fluorescence upon interaction with NB vapor, suggesting that these films can serve as new types of selective solid luminescent sensor. Therefore, this work supplies a facile LBL strategy for the fabrication of TFs as selective luminescent sensor for the trace detection of NB.

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