Highly luminescent carbon dots as temperature sensors and off-on sensing of Hg2+ and biothiols

Here, Carbon dots (CDs) were fabricated through a simple one-step hydrothermal treatment of N-aminoethylpiperazine (AEP) and citric acid (CA). The as-prepared CDs have a bright blue emission with a quantum yield of 56%, with good water solubility, light stability and temperature sensitivity. In addition, the photoluminescence of the CDs deriving from two components was experimentally verified: one is amide molecules resulting from the reaction between AEP and CA, and the other is the carbon nucleus coming from the precursors at high temperatures. More importantly, the fluorescence intensity of the CDs is temperature-dependent, and decreasing linearly from 25 degrees C to 95 degrees C, with excellent sensitivity and recoverability. A CD/epoxy composite was prepared by doping the CDs into an epoxy resin, which exhibits superior temperature response that may be caused by the greater dielectric constant of epoxy resin. In addition, the fluorescence of the CDs can be efficiently quenched by Hg2+, and the addition of biothiols restore the quenched fluorescence of CDs. The sensor was applied to detect ions in river water and tap water and satisfied results were achieved.