Amino acid derivatized carbon dots with tunable selectivity as logic gates for fluorescent sensing of metal cations

Carbon dots (CDs) modified with ethylene diamine (EDA) and the amino acids (AAs) Cys, His, Lys or Arg were synthesized, and their structures were confirmed by high resolution transmission electron microscopy, Raman spectrometry and X-ray photoelectron spectrometry. It is found that derivatization of the CDs with various AAs systemically modulates their electronic properties, and this results in a tunable selectivity in detection of metal cations via fluorescence quenching. The probes can be performed in aqueous solutions around pH 7. CDs can be excited under 345 nm excitation at room temperature and exhibit fluorescent peak at 450 nm. The decreasing fluorescence intensity is directly proportional to the concentration of metal cations. The limits of detection is 8.8 μg L^?1 for Pb(II), 20 μg L^?1 for Hg(II), 3.7 μg L^?1 for Cu(II), 5.3 μg L^?1 for Zn(II), 16 μg L^?1 for Fe(III), and 7.2 μg L^?1 for Cr(III), respectively. The different fluorescence response of the AA-modified CDs can be converted to logic gates and applied to photoelectronic nanoprobes by using microprocessors. In our perception, this assay has a large potential in terms of high-throughput screening for trace amounts of metal ions.

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Graphical abstract Amino acid derivatized carbon dots with tunable selectivity were synthesized by a one pot method for fluorescent sensing of metal cations. The sensing events can be directly converted into different logic gates.