A photoluminescence “switch- on” nanosensor composed of nitrogen- doped carbon dots- silver nanoparticles for highly selective and sensitive detection of cysteine

Carbon nanodots (CDs) are a new high luminescence class of carbon nanomaterials with the size in the range of units of nanometers. Typically, CDs contain carbon core and many carboxylic groups at their surface, thus imparting them with excellent water solubility and the suitability for subsequent functionalization with various organic, polymeric, inorganic, or biological substances [1]. Isoniazid, pyridine-4-carboxylic acid hydrazide, is an antituberculosis agent, which is usually used to prevent the development of clinical tuberculosis[2] .innovative water-soluble nitrogen-doped carbon dots(N-CDs) with bright luminescence and high quantum yield were synthesized via a simple and straight forward hydrothermal method, using an aqueous solution of isoniazid as a novel N containing single-source precursor. In this paper the intraction of nitrogen-doped carbon dots from isoniazide with silver nanoparticles (AgNPs) was investigated using fluorescence spectroscopy. It was found that AgNPS efficiently quench the fluorescence of N-CDs as a result of fluorescence resonance energy transfer (FRET). thus, a FRET system between nitrogen-doped C-Dots (as the donor) and AgNPs (as the acceptor) was introduced. Moreover, it was found that cysteine could recover the fluorescence of N-CDs due to the competitive adsorption of this compound onto AgNPs. This was expolited to design a simple and selective method for the determination of cysteine in the concentration range from 3× to 6×(mol/lit), with a detection limit of 3.9×(mol/lit).