A new poly(3-alkoxy-4-methylthiophene)-based polymer PTMA was synthesized via simple methods.

The fluorescence of PTMA could be quenched in the presence of Co²⁺, Cu²⁺ and Cd²⁺ in MeCN/Tris–HCl solution.

Cd²⁺ induced a significant bathochromic shift on the maximum absorption of PTMA solution.

The fluorescence of PTMA could only be quenched by Cu²⁺ in THF/Tris–HCl solution, and recovered by GSH and HCy.

Detection limits for Co²⁺, Cu²⁺ and Cd²⁺ can be reached 2.5, 2.0 and 83 nM, respectively.