Fluoranthene-based derivatives for multimodal anti-counterfeiting and detection of nitroaromatics

Abstract

In this study, we developed two novel sky blue fluorescent fluorophores comprising ethyl alcohol (FOH) and ethanethiol (FSH) units appended to fluoranthene at the periphery. Single Crystal X-Ray Diffraction (SC-XRD) studies reveal that the molecular flexibility of alkyl chains leads to distinct diagonal (FOH) and ladder (FSH) shaped supramolecular arrangements in the crystal lattices. Detailed photophysical and DFT studies showed that FOH and FSH demonstrate high sensitivity and selectivity towards the detection of trinitrophenol (TNP). FSH exhibits high quenching efficiency (∼84%), a rate constant of K_SV = 1.1 × 10⁴ M⁻¹ with a limit of detection of ∼97 ppm in THF, and ∼76 ppm in river water. Mechanistic investigation through NMR and SC-XRD of the FSH adduct with 1,3-dinitrobenzene (DNB) reveal strong π–π interactions (3.518 Å). Furthermore, photoinduced electron transfer occurs from the fluorophores to the nitro analytes and leads to strong intermolecular interactions using the static quenching mechanism. Both fluorophores were employed in advanced surveillance to identify finger marks on a wide range of substrates (glass, cellophane tape, aluminium foil and floor tiles) with different resolutions to provide an unadorned and lucrative method for viewing the latent fingerprints (LFPs) with exceptionally consistent evidence of up to level 3 and without the requirement for post-treatments, leading to promising applications for onsite forensic analysis. Furthermore, FOH and FSH were evaluated in 72 hpf zebrafish larvae/embryos to demonstrate the non-toxicological behaviour and fluorescence imaging/tracking.