N-doped carbon quantum dots as fluorescent probes for highly selective and sensitive detection of Fe3+ ions

Abstract

To investigate the effect of nitrogen on the photoluminescence properties of carbon quantum dots (CQDs), N-doped carbon quantum dots (N-CQDs) were synthesized by one-step hydrothermal treatment using biomass tar as the carbon precursor. As an inevitable organic pollutant, the unsaturated bonds in biomass tar, such as carboxylic acids, aldehydes, and aromatics, are favorable for formation of the graphitic carbon lattice. The obtained N-CQDs are spherical with an average particle size of 2.64nm and the crystal lattice spacing is 0.25nm, corresponding to the (100) facet of graphitic carbon. The N-CQDs emit bright blue photoluminescence under 365nm ultraviolet light, and they have excellent water solubility and stability with a high quantum yield of 26.1%. Coordination between the functional groups on the N-CQD surface and Fe3+ ions is promoted because of the improved electronic properties and surface chemical reactivity caused by N atoms, leading to a significant fluorescence quenching effect of the N-CQDs in the presence of Fe3+ ions with high selectivity and sensitivity. There is a linear relationship between ln (F0/F) and the Fe3+ concentration in the N-CQD concentration range 0.06–1400μmol/L with a detection limit of 60nmol/L, showing that the N-CQDs have great potential as a fluorescent probe for Fe3+ detection.