Thiol-capped PbS semiconductor nanoparticles (NPs) stabilized with a mixture of 1-thioglycerol/ dithioglycerol (TGL/DTG) were colloidally prepared at room temperature. UV-vis spectroscopy and photoluminescence (PL) spectra showed an obvious redshift in both the absorption shoulder and PL peak with the increase of DTG/Pb molar ratio. Room temperature photoluminescence quantum efficiency (PLQE) of freshly prepared PbS NPs (7-11%) remained higher than 5% upon aging for 3 weeks when the NPs were stored in an ice-bath in the dark, and higher than 5% for at least 5 weeks when additional DTG ligand was introduced into the nanoparticle solution every 2 weeks. The combination of reasonable room temperature quantum efficiency and strong, stable luminescence covering the 1.3 mu m telecommunication window make these NPs promising materials in optical devices and telecommunications.