Novel carbon dots from phenylenediamine for simultaneous detection of peroxydisulfate and phosphate with a smart phone by dual-channel of fluorometry and colorimetry.

Carbon dots (CDs), one type of zero-dimensional carbon nanomaterial, showed extensive application in food analysis. Herein, CDs as fluorometry and colorimetry probes were developed to determine peroxydisulfate (PDS) and phosphate ion (Pi) in food samples. CDs were developed with one-pot hydrothermal process from 5-amino salicylic acid and o/m-phenylenediamine named o/m-CDs. o-CDs and m-CDs showed bright green fluorescence with quantum yield at 5.73 % and 6.40 %, which was quenched by PDS and Pi. Fluorometry was based on fluorescence quenching with LOD at 1.6 nM (PDS) and 5.2 nM (Pi). The colorimetry was based on color change of CDs from colorless to brown and indigo blue with LOD at 2.4 (PDS) and 21.1 μM (Pi). Interestingly, for both channels there was no interfering of each other. For portable detection, a wechat mini program of smart phone was employed to calculate the color change. Furthermore, the systems were potential for application in food safety analysis.