A smartphone-assisted colorimetric/fluorescence dual-mode sensor based on Si-CDs for highly selective and sensitive detection of Cu2.

In this study, silicon-doped carbon dots (Si-CDs) were synthesized using a one-step solvothermal method to construct a colorimetric-fluorescence dual-mode sensing platform for Cu2+ detection. The prepared Si-CDs exhibit excellent water solubility and stable optical properties, and can respond specifically to Cu2+ through a chelation-enhanced fluorescence mechanism. This dual-mode sensing system exhibited excellent linear relationships with Cu2+ concentration, with R2 values of 0.998 and 0.997, respectively, and detection limits as low as 6 nM and 0.11 μM, demonstrating outstanding selectivity and resistance to interference. To enable rapid on-site detection, this study also established two smartphone-assisted visual detection methods based on HSV values corresponding to the dual-mode system. The four methods-instrumental colorimetry, instrumental fluorescence, and smartphone detection under daylight and UV light-complement and cross-validate one another, effectively enhancing detection accuracy and the reliability of results. This system provides an efficient and practical new strategy for the highly sensitive, portable detection of Cu2+ in environmental water bodies.