Perylene bisimide-based nanocubes for selective vapour phase ultra-trace detection of aniline derivatives

Rapid and selective detection of biomarkers at trace levels is a highly coveted objective in the early diagnosis of cancer. Herein, we disclose the design and synthesis of a polyhedral oligomeric silsesquioxane (POSS) substituted perylene diimide. This compound is fully characterized in solution by multi nuclear NMR, as well as in gas state by ESI-MS. Surprisingly, solid-state characterization revealed an unusual cubic morphology with particle dimensions of 80-160 nm. Fluorescence studies indicate that the bulky POSS units effectively prevent perylene's aggregation caused quenching, yielding quantum yields as high as 92%. Exposing the sensor droplet-cast on quartz to anline and o-toluidine, two important biomarkers for lung cancer, results in very highly reproducible, reversible and selective fluorescence quenching responses, with LODs as low as 19 and 8 ng L^-1, and linear ranges of 65-350 and 25-450 ng L^-1 respectively. Mechanistic investigations point to photoinduced electron transfer (PET) as the operative pathway responsible for fluorescence quenching.