Novel thieno-imidazole based polymer P showed both colorimetric and ratiometric detections of Hg(2+) as well as fluorometric detection of Zn(2+) via fluorescence turn-on response with augmented lifetime. Its model polymer M did not show any such sensing capability under similar conditions, which further confirmed the unique sensitivity of P toward Hg(2+) and Zn(2+) via the chelation of metal ions to both "S" and "N" heteroatoms.