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Near-infrared (NIR) fluorescent quantum dots (QDs) have attracted considerable attentions in bio-imaging and bio-detection because auto-fluorescence and absorption from cells and tissues can be effectively lowered in the NIR range1, 2.By coupling the biochemical process of Na2SeO3 reduction with the binding of silver ions with alanine to construct a quasi-biosystem, sub-3 nm water-dispersible Ag2Se QDs with good monodispersity were controllably synthesized, with controllable NIR fluorescence wavelengths (700nm to 800nm).And Ag2Se QDs are environmentally-benign alternatives for heavy metal-containing NIR QDs.The new ultrasmall and low-toxicity alanine-coated NIR QDs possess carboxyl groups available for use, which can be easily bound to biomolecules, such as proteins.After the alanine-coated Ag2Se QDs were covalently conjugated with alpha-fetoprotein (AFP) antibodies (anti-AFP) using EDC as the coupling reagent, the resulting NIR fluorescent probe (anti-AFP-conjugated Ag2Se QDs) could specifically bind to the HCCLM9-1iver cancer cells (Figure 1), demonstrating the potential of this less toxic NIR probe based on Ag2Se QDs in bio-labeling and bio-imaging.