Silver-loading in uncrosslinked hydrogen-bonded LBL films: structure change and improved stability

Abstract

As nanoreactor for the synthesis of metal nanoparticles, hydrogen-bonded layer-by-layer assembled (LBL) films may be a better choice than the electrostatic ones, because more carboxylic acid groups are available for metal ion binding. However, these films should be crosslinked before metal ion loading because of their instability (Chem. Mater., 2005, 17, 1099–1105). Here we report that the uncrosslinked hydrogen-bonded poly(vinyl pyrrolidone)/poly(acrylic acid) (PVPON/PAA) LBL films remain stable during Ag⁺ loading. FTIR and XPS studies indicate that Ag⁺ binds with PVPONvia coordination interaction, while it simultaneously binds with PAAvia electrostatic interaction. Therefore the films do not disintegrate upon the disruption of hydrogen bonds between PVPON and PAA. After Ag⁺ loading, the erosion rate of the film in water decreases, indicating that the long-term stability of the film is actually improved. The loaded Ag⁺ can be easily unloaded by immersing the film in acidic solutions. The loading and unloading of Ag⁺ are reversible and can be repeated many times. Silver nanoparticles were synthesized in situ by UV irradiation. The nanoparticles are spherical in shape and present a surface plasmon absorption peak at 434 nm.