New luminescent electrospun (ES) fibers for pH-tunable colorimetric sensors were prepared from binary blends of poly(phenylquinoline)-block-polystyrene (PPQ-b-PS)/polystyrene (PS) with a single-capillary spinneret. The PPQ-b-PS aggregated domain sizes in the ES fibers prepared from dichloromethane (CH2Cl2), chlorobenzene (CB) and chloroform (CHCl3) were 1.5 +/- 0.5, 2.2 +/- 0.4 and 4.1 +/-1.1 mu m, respectively. Such variation on the aggregation size led to the red-shifting photoluminescence spectra changing from green, to yellow, and orange. ES fibers prepared from CH2Cl2 exhibited pH-tunable photoluminescence and the emission maximum varied from 532 to 560 nm as the pH value changed from 7 to 1. The study demonstrated that the ES fibers prepared could have potential applications for sensory devices.