Fluorescent and colorimetric dual-mode detection of Cu²⁺ based on carbon dots

A fluorescent and colorimetric dual-mode strategy based on carbon dots (CDs) was rationally designed for sensitive determination of Cu²⁺. Green fluorescent CDs with high absolute quantum yield of 72.9% were synthesized by facile one-step hydrothermal treatment of triethylenetetramine and Rose Bengal. Cu²⁺ could trigger the oxidative and chromogenic reaction of p-phenylenediamine (PPD) to generate chromogenic PPDox, accompanied by the fluorescence quenching of the CDs. The quenching mechanism was identified as the inner filter effect between PPDox and CDs. Therefore, a colorimetric/fluorescent dual-mode detection method for Cu²⁺ recognition was constructed. The limits of detection for Cu²⁺ were 4.14 μM and 1.28 μM for colorimetric and fluorescent mode, respectively. In addition, this method had achieved satisfactory results in the detection of Cu²⁺ in real serum samples.