ABSTRACTSolution‐dispersible hyperbranched conjugated polymer nanoparticles (FT‐HBCPNs) consist of an intrinsic crosslinked rigid skeleton structure of both 9,9‐dihexyl‐fluorene and triphenylamine repeating units, and are synthesized via the miniemulsion Suzuki polymerization, and FT‐HBCPNs for highly selective and sensitive Fe3+ fluorescent detection and their application in logic gate at molecular level are successfully developed. FT‐HBCPNs with an average particle size of 10.6 nm can disperse in common organic solvents. FT‐HBCPNs show high selectivity and sensitivity for Fe3+ over other commonly co‐existent metal ions in THF solution with a detection limit of 3.65 × 10−8 mol L−1. Furthermore, homogeneous transparent thin films of FT‐HBCPNs developed by a simple spin‐coating method can be reversibly quenched by Fe3+ with a detection limit of 3.09 × 10−7 mol L−1. Using Fe3+ and EDTA as chemical inputs and the fluorescence intensity signal as outputs, FT‐HBCPNs films can be utilized as a logic gate at molecular level. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3694–3700