A ratiometric fluorescent hybrid nanoprobe CDs-1 for arginine (Arg), exhibiting high sensitivity (the limit of detection, LOD, being 6.5 x 10(-8) mol/L) and excellent selectivity and anti-interference ability, was fabricated through fluorescence resonance energy transfer (FRET) and the electrostatic attraction between positively-charged hemicyanine molecules and negatively-charged carbon dots (CDs). Arg can be quantitatively detected in the concentration range from 6.0 x 10(-5) mol/L to 2.7 x 10(-4) mol/L. Further, due to its ability to target mitochondrion and low cytotoxicity, intracellular Arg was successfully tracked through ratiometric fluorescence imaging. (C) 2019 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.