Tunable photoluminescence emission from surface-state to carbon core-state of PAMAM carbonized polymer dots and its high-sensitive detection of copper(II)

Carbon dots (CDs) are important zero-dimensional materials with excellent luminescent properties. However, the mechanism of CDs photoluminescence is still an open debate, which significantly hinders the development of CDs with desired optical properties. In this work, bright blue fluorescent carbonized 1.0 G polyamine-amine polymer dots (NCPDs) has been prepared by a simple hydrothermal method, with a quantum yield of 57 %. The dominant luminescence of the NCPDs is attributed to the surface states based on synergistic hybridization between the carbon backbones and connected functional groups at below 120 °C. Photoluminescence transforms from the surface states to the surface - carbon core states, and then to carbon core states from 120° to 150 °C. Meanwhile, the degree of carbonization increases along with the size of NCPDs growing from 1.36 to 3.20 nm, and the NCPDs present excitation-dependent emission properties. Due to the remarkable fluorescence property of NCPDs, Cu2+ determination has been carried out in the aqueous phase, and the detection limit is 9 nM, which is much lower than the international minimum standard (20 μM). NCPDs present high selectivity and sensitivity toward detecting Cu2+, and provide potential applications in detecting metal pollution in the environmental water.