A ratiometric fluorescent probe for a smartphone-based dual-emission carbon dot fluorescence sensor for the rapid detection of 5-HIAA

This study utilized Panax notoginseng leaves carbon dots (PN-CDs) with red and blue fluorescence to detect 5-hydroxyindoleacetic acid (5-HIAA). It is a straightforward one-pot hydrothermal technique using Panax ginseng leaves to synthesize these CDs. Under 400 nm excitation, 5-HIAA decreases the fluorescence intensity at 670 nm while enhancing the fluorescence intensity at 420 nm. The fluorescence intensity ratio (F 670 /F 420 ) exhibited a significant linear relationship over the 5-HIAA concentration range of 0–100 μM. Notably, smartphones could capture the observable color change of the PN-CDs under 365 nm UV exposure and perform RGB (red/green/blue) analysis for color quantification using the smartphone’s software. The detection limit for its fluorescence detection was determined to be 0.023 μM, whereas that of mobile phone detection was 0.36 μM. This study proposes a novel platform combining fluorescence sensing and cell phone technology, facilitating real-time analysis of 5-HIAA levels in human urine.