Time-resolved fluorescence sensor array for the discrimination of phosphate anions using transition metal...

Phosphate detection has garnered widespread attention due to its biological and environmental impact. Among several optical techniques, time-resolved fluorescence (TRF) provides a sensitive way for the discrimination of analytes in a complex mixture as it exhibits less interference from the background, therefore providing a high signal-to-noise ratio. The sensitization of rare earth metal (REM) ions by semiconducting quantum dots (QDs) can help the former overcome the drawback of low absorption coefficient, therefore allowing exploitation of the additional advantage of the REM, namely the long-excited state lifetime. Here, we have developed a TRF-based sensor array consisting of three QDs, i.e. MoS₂ , WS₂ and MoSe₂ as energy sensitizers for Tb³⁺ ions. Different QDs possess variable energy transfer abilities for Tb³⁺ ions. Therefore, they can be used to discriminate phosphates. It was also observed that CrO₄ ^2- can competitively bind to Tb³⁺ and further enhance the efficiency of the sensor array so that it could discriminate six different phosphates at 200 μM concentration in aqueous as well as serum medium with a detection limit of 10 μM in aqueous medium. Therefore, the sensitivity of the TRF-based sensor array is rarely compromised in a complex mixture, which is advantageous over a fluorescence-based sensor array.