Electrochemical synthesis of photoluminescent carbon nanodots from glycine for highly sensitive detection of hemoglobin

An electrochemical approach has been employed for the preparation of photoluminescent carbon nanodots (C-dots) from glycine under alkaline conditions. The formation of C-dots is through electro-oxidation, electro-polymerization, carbonization, and passivation. The as-prepared C-dots possess excitation-wavelength-dependence and pH sensitive photoluminescence (PL) properties and are stable in solution containing high salt concentration (up to 500 mM NaCl). Detection of hemoglobin using C-dots has been demonstrated through a fluorescence resonance energy transfer (FRET) process. The PL intensity (excitation/emission wavelengths 365/440 nm) of C-dots is inversely proportional to the concentration of hemoglobin over a range of 0.05-250 nM (r = 0.99), with a limit of detection (signal-to-noise ratio 3) of 30 pM. We have validated this assay by determining the concentrations of hemoglobin in five representative diluted blood samples, with results being in good agreement with that obtained by using a commercial hemoglobin meter. The water-dispersible and photostable C-dots have been applied to obtain bloodstained images and fingerprints.