A reliable and selective ratiometric sensing probe for fluorometric determination of PO based on AIE of GSH@CuNCs-assisted by Al-N@CQDs.

In this study, a novel composite material was developed for the ratiometric detection of pyrophosphate anion (PO). This composite consisted of Al and nitrogen co-doped carbon dots (Al-N@CQDs) and glutathione-capped copper nanoclusters (GSH@CuNCs). The Al-N@CQDs component, with its high reserved coordination capacity of Al, induced the non-luminescent behavior of GSH@CuNCs, resulting in an aggregation-induced emission (AIE) effect. The hybrid material (Al-N@CQDs/GSH@CuNCs) exhibited dual-emission signals at 620 nm and 450 nm after integrating the two independent materials utilizing the AIE effect and the fluorescence resonance energy transfer (FRET) approach. This approach represents the first utilization of this composite for ratiometric detection. Nevertheless, upon the addition of PO, the AIE and FRET processes were hindered due to the higher coordination interaction of Al towards PO compared to the amino/carboxyl groups on Al-N@CQDs. This successful interference of the AIE and FRET processes allowed for the effective estimation of PO. The response ratio (F/F) increased with increasing the concentration of PO in the range of 0.035-160 µM, with an impressive detection limit of 0.012 µM. This innovative approach of utilizing hybrid CQDs/thiolate-capped nanoclusters as a ratiometric fluorescent sensor for analytical applications introduces new possibilities in the field. The as-fabricated system was successfully applied to detect PO in different real samples such as water, serum, and urine samples with acceptable results.