Using thiol-stabilizing aqueous solution method, we have synthesized PbS quantum dots (QDs) that emit stable and spectrally tunable photoluminescence in the optical telecommunication band at around 1300 nm. The emission wavelength of the QDs was varied from 1295 to 1330 nm by increasing the synthesis time or Pb2+/TGA molar ratio. PbS nanocrystals (NCs) were directly imaged using high-resolution transmission electron microscopy, which gave an evaluation of the averaged sizes and the symmetry indexes of NCs. The symmetry index of NCs synthesized for 96 h was improved to 0.92 from 0.85, compared with that synthesized for 24 h. It has been found that chemically synthesized water-soluble PbS QDs are a potential source of entangled photon pairs in the near future. (c) 2013 Elsevier B.V. All rights reserved.