Hydrothermal synthesis of monodisperse Ag2Se nanoparticles in the presence of PVP and KI and their application as oligonucleotide labels

Monodispersed silver selenide (Ag2Se) nanoparticles have been prepared successfully by a hydrothermal reaction of AgNO3 with Na2SeSO3 in the presence of poly(vinyl pyrrolidone) (PVP) and KI at 180 °C for 20 h. TEM revealed that the nanoparticles are much like husked rice with lengths of about 60–80 nm and widths of about 30–40 nm. KI was dispersed in a PVP solution first, then an appropriate amount of AgNO3 solution was slowly added until the molar ratio of Ag+ to I− reached 1 : 1. The formed complex ions of [AgmIn](n−m)− and AgI in the procedure are more stable owing to the protection effect of PVP, or these could be considered as complexes of PVP–[AgmIn](n−m)− and PVP–AgI. These complexes functioned as the precursors; the formation rate of Ag2Se crystal cores in the hydrothermal reaction could be well controlled. The final shape and size of the product were affected by the amount of PVP and the molar ratio of I− to Ag+, and higher PVP content was beneficial to the formation of the husked rice-like shape. The Ag2Se nanoparticles can be used for the detection of DNA hybridization. A specific DNA sequence related to the PEP promoter gene in transgenic plants was determined with a detection range from 1.0 × 10−12 to 1.0 × 10−8 mol L−1 and a detection limit of 2.3 × 10−13 mol L−1 (3σ). The method had good selectivity and was successfully used to distinguish between a three-base mismatched ssDNA sequence, a non-complementary sequence and a complementary sequence.