Lead sulfide (PbS) nanocrystals (NCs) were surfactant-free synthesized and stabilized with thioglycolic acid (TGA) by an environmentally friendly and controllable chemical route. Structural, surface morphological, optical and photoluminescence properties of the samples were studied using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), low-resolution transmission electron microscopy (LR-TEM), FT-IR spectroscopy, UV visible spectroscopy and fluorescence spectroscopy, respectively. The synthesized TGA-PbS NCs showed a well-defined cubic morphology and size mono-dispersity, as well as good dispersibility in aqueous solution. The optical and photoluminescence study showed that these NCs were very crystalline, size quantized and exhibited a single strong, narrow red emission band centered at lambda(Em) = 680 nm. Time evolution of the emission properties was analyzed after six, twelve and twenty four months. The results confirmed that the as-prepared product is photostable when it is kept under storage at 4 C and has great potential for both biotechnological applications and analytical purposes. A probable chemical stabilization mechanism is proposed. (C) 2014 Elsevier B.V. All rights reserved.