Dual-mode detection of ascorbic acid in orange juice by N/S doped carbon dots based on cellulose acetate

N/S-doped carbon dots/gold nanoparticles/Ag+ (N/S-CDs/AuNPs/Ag+) as a dual-mode nanoprobe was constructed to detect ascorbic acid (AA). Compared with simple carbon dots, N/S-CDs exhibited superior fluorescence properties, which could play a more important role in building a sensitive homogenous FRET fluorescence detection platform. Moreover, AuNPs/Ag+ was reduced to core-shell Au@AgNPs by AA in an alkaline environment, which could induce the localized surface plasmon resonance (LSPR) and led to the change of UV absorption peak position from 520 nm to 426 nm with the color changing from pink to bright yellow. Due to the fluorescence "turn on-off" and LSPR, the N/S-CDs/AuNPs/Ag+ nanoprobe is inspected for the sensitive dual-mode detection of AA. The linear detection ranges are from 0.5∼100 μM for colorimetric mode and 0.5∼90 μM for fluorescence method. Their LODs are 0.17 and 0.10 μM, respectively. Furthermore, this proposed nanoprobe showed high sensitivity and accuracy for AA detection in real orange juice, displaying great possibility in food testing.