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

Abstract

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 [Ag_mI_n](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–[Ag_mI_n](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.