An efficient conjugated polymer sensor based on the aggregation-induced fluorescence quenching mechanism for the specific detection of palladium and platinum ions

Abstract

Based on the aggregation-induced fluorescence quenching mechanism, a 2,6-dithienyl-4-phenylpyridine-containing conjugated polymer (P-A) has been designed and synthesized via a Sonogashira coupling reaction as an efficient fluorescent sensor for palladium and platinum ions. The metal ion-sensitivity of P-A was evaluated using a series of transition metal ions in aqueous solution. On binding to Pd²⁺ or Pt⁴⁺, fluorescence quenching of P-A was demonstrated by an approximately 80% reduction in the fluorescence intensity, while no obvious fluorescence change could be observed in the presence of other metal ions. Compared with its small molecular counterpart, P-A exhibits higher sensitivity and selectivity. The fluorescence intensity of P-A has shown a linear response to both Pd²⁺ and Pt⁴⁺ in the concentration range of 1–10 μM with a detection limit of 1 × 10⁻⁶ M in aqueous solution. It has been demonstrated that the sensitive property of the polymer sensors for the palladium and platinum ions is highly dependent on the fine structure of the conjugated polymers. The fluorescence quenching can be attributed to the Pd/Pt-induced aggregation of the polymer chains, which has been proved by fluorescence anisotropy methods. These results indicate that the fluorescence-amplifying method based on the aggregation-induced fluorescence quenching mechanism has enormous potential for the development of highly efficient fluorescence sensors towards the detection of palladium and platinum ions.