In Situ Green Synthesis of Nitrogen-Doped Carbon-Dot-Based Room-Temperature Phosphorescent Materials for Visual Iron Ion Detection

Room-temperature phosphorescent (RTP) materials show great potential for ion detection due to a long lifetime and a high signal-to-noise ratio. Most RTP materials are limited to organometallic or organic compounds that are costly, toxic, and complex. Here, an in situ green synthesis of carbon dot (CD)-based RTP materials using Schisandra chinensis polysaccharide as the only carbon source, which has a natural nitrogen-containing structure for endogenous nitrogen-doping, is performed. RTP measurements show that the CD-based RTP materials had lifetimes up to 271.2 ms under 350 nm excitation and with a smaller energy gap (0.32 eV). In addition, they exhibit adequate quenching in the presence of iron ions (Fe3+). The visible RTP intensity is inversely proportional to the Fe3+ concentration over the range of 0.1–2 mM, with a 0.57 μM detection limit. Further, the prepared CD-based RTP materials have highly stable optical and physical properties, which open a new perspective as luminescent sensors for Fe3+ detection with inexpensive and green raw materials.