Carbon dots-based room-temperature phosphorescent test strip: Visual and convenient water detection in organic solvents

Room-temperature phosphorescence (RTP) has got more and more attentions in sensing due to its specific optical properties of longer lifetime and higher signal-to-noise ratio. However, developing low-cost RTP test strip (RTP-TS) for visual and convenient detection is still a challenging. Here, we reported the construction of new RTP-TS based on N-doped carbon dots (N-CDs), which was synthesized with a simple hydrothermal method using isophthalic acid (IPA) and ethylenediamine (EDA) as precursors. The constructed RTP-TS exhibited bright green RTP emission under UV excitation (365 nm) with a longer lifetime of 0.769 s. The mechanism studying indicates the efficient RTP emission of RTP-TS is from the N/O-rich CDs and the anchor effect of polyacrylic acid (PAA), which can restrict the varication/rotation of N-CDs by H-bonds, and suppress the nonirradiative quenching processes. Nevertheless, the presence of H2O can destroy these H-bonds and therefore effectively quench the RTP emission of RTP-TS, the changes of RTP intensity is inversely proportional to H2O concentration. Based on this, the RTP-TS has been successfully used for visual and convenient water detection in several common organic solvents (ethanol, acetone, acetonitrile, tetrahydrofuran) with high sensitivity, excellent stability, accuracy and reliability. This work will open a new approach to construct visual RTP-TS for practical use in sensing.