Colorimetric and luminescent detection of cysteamine based on lanthanide-doped upconversion nanoparticles and gold nanoparticles

A colorimetric/luminescent detection nanoprobe based on polyacrylic acid (PAA)-modified lanthanide-doped upconversion nanoparticles (PAA-UCNPs) and gold nanoparticles (AuNPs) is prepared for cysteamine detection. PAA-UCNPs (NaYF 4 :Yb,Er@NaYF 4 ) exhibit green and red emission under near-infrared laser excitation. In the presence of cysteamine, citrate-stabilized AuNPs aggregate, causing a significant red shift in their absorption peak and weakening the red luminescence of PAA-UCNPs based on the inner filter effect (IFE). This nanoprobe enables rapid (5 min) and precise determination of cysteamine, with a wide linear range (0.1–1.0 µM in colorimetric mode and 0.25–1.25 µM in luminescence mode) and a low detection limit (44.4 nM in colorimetric mode and 23.3 nM in luminescence mode). Moreover, this dual-mode method is used for cysteamine detection in calf serum, demonstrating high sensitivity and reproducibility. Section Graphical