Bright-green-emissive nitrogen-doped carbon dots as a nanoprobe for bifunctional sensing, its logic gate operation and cellular imaging

Abstract

A fluorescent nanoprobe based on nitrogen-doped carbon dots (N-CDs) with green fluorescent emission have been fabricated through a facile one-step hydrothermal treatment using catechol and triethylene tetramine as precursors. The obtained N-CDs with excellent luminescent properties and superior biocompatibility have been applied for the development of a bifunctional sensor for the detection of Fe3+ and ascorbic acid (AA). Fe3+ that are tightly chelating the surface of N-CDs can induce fluorescence (FL) quenching of N-CDs through photo-induced electron transfer (PET). Meanwhile, the addition of AA serves to shelter the CDs effectively from being quenched by Fe3+ due to AA, as an antioxidant, enable easy-conversion of Fe3+ to reduced states (i.e. Fe3+ and Fe2+). The N-CDs are used as a facile and label-free “on-off-on” fluorescent nanoprobe for the determination of Fe3+ and AA with detection limits of 58.82nM and 0.236µM with the corresponding linear ranges of 25–200µM and 25–300µM, respectively. According to this phenomenon, an “AND” logic gate based on the novel N-CDs has been constructed. As-prepared N-CDs with negligible toxicity and perfect biocompatibility were expanded for cellular imaging and sensing Fe3+ and AA in living cell, which enlarges the application range of the N-CDs. Most importantly, the as-constructed fluorescent sensing system was successfully applied to detection of Fe3+ in tap water and the analyses of AA in fresh fruits with satisfactory results.