The morphology and size of the as-synthesized powder of Ag2Se is characterized by FESEM, as shown in Fig. 1(b). One can find that Ag2Se has granular structures with average size of around 100nm. In the chemical reaction process, ethylenediamine could reduce Ag+ to atomic Ag, which can be combined with elemental selenium, forming the seeds (original nanoparticles). The fresh nanoparticles tend to aggregate and produce larger particles due to the existence of high surface energy at nanoscale, which forms the granular Ag2Se.