A series of novel π-electron rich fluoranthene derivatives (P1–P3) adorned with symmetrical and unsymmetrical alkoxy chains were developed using Diels-Alder reaction. The use of peripheral triethyleneglycol (TEG) chains on fluoranthene enhances its electron donating ability and furnishes decrease in their energy levels and optical band gap. The intense sky-blue fluorescence exhibiting fluoranthene ensembles have been investigated as potential fluorescent chemosensors for the detection of explosive nitroaromatics (NACs). Fluorescence studies demonstrate that emission intensity of P1–P3 was efficiently decreased upon interaction with picric acid (PA) in a dominant static quenching phenomena which is attributed to photoinduced electron transfer process. The limit of detection (LOD) was found to be in the range of 2–20 ppb. The vapour phase sensing study involving thin films of P1–P3 showed efficient quenching response and sensing process is found to be highly reversible. Surface morphology of thin films significantly varied with the type of alkyl chain present on fluoranthene. The thin films are highly selective towards PA in aqueous medium containing commonly interfering nitro-explosives. Contact mode approach using silica gel substrates allows femto-gram detection of trinitrotoluene (TNT) and PA makes these materials as potential chemosensors for real time applications. Display omitted •High blue fluorescent novel fluoranthene derivatives with varied nature of alkyl chains•Selective detection of 2,4,6-trinitrophenol in aqueous and vapour phase methods•Porous nature thin films enhance the sensitivity and selectivity.•Good reversibility and recycling of thin films•Femto-gram detection of 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol by contact method