A novel high selective and sensitive fluorescent-colorimetric sensor have been developed for the determination of Pb2+ ions based on an ultrasound-assisted nano thieno[2,3-b]thiophene-2,5-dicarboxaldehyde-based Schiff base (H2L). A silica-based portable probe was fabricated via spin coating of H2L on a glass slide with diameter of 64 nm which has been applied in real sample successfully. The probe has been exploited as a dual chemosensor to detection lead ions in aqueous media with a detection limit of 6.78 μg/L and 7.38 μg/L respectively and dynamic concentration range of 0.6 × 10−8 to 4.12 × 10−5 mol L−1. Based on the Job plot analysis, 1:1 stoichiometric ratio between H2L and Pb2+ has been established. The removal percentage range of lead ions has been obtained 96–99.6% with a response time of 80 s. Furthermore, DFT calculated molecular orbital, energy gap, MPA, MEP and ESP of the optimized structure of chemosensor confirmed the sensing results. © 2018 Elsevier B.V.