Open AccessDestabilization of PVA-stabilized Ag NPs: color changes at low aqueous concentrations, induced by aggregation and coalescence
Author(s) -
Junqiang Hu,
Longlai Yang,
Yan Zhu,
DeQuan Yang,
E. Sacher
Publication year - 2020
Publication title -
materials research express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.383
H-Index - 35
ISSN - 2053-1591
DOI - 10.1088/2053-1591/ab6c90
Subject(s) - aqueous solution , coalescence (physics) , agglomerate , precipitation , surface plasmon resonance , vinyl alcohol , nanoparticle , chemical engineering , silver nanoparticle , blueshift , materials science , red color , chemistry , analytical chemistry (journal) , nanotechnology , chromatography , polymer , optics , organic chemistry , photoluminescence , physics , astrobiology , engineering , optoelectronics , meteorology
Aqueous concentrations of poly(vinyl alcohol) (PVA)-stabilized ∼10 nm silver nanoparticles (Ag NPs), in the 1000 ppm concentration range, have been shown to be highly stable at elevated temperatures. However, lower concentrations of these NPs undergo color changes, without precipitation, when heated or when held for extended periods of time at room temperature. We have studied their optical and morphological changes at 80 °C, using UV–vis spectra and TEM, and found that their color, at a concentration of 10 ppm, changes from yellow to claret-red to black without precipitation. Further, the plasmon resonance peak at ∼400 nm diminishes as a new peak develops at ∼550 nm. These changes occur as the previously well-dispersed NPs (yellow color) agglomerate to chains (claret-red color) and, finally, coalesce (black color). We discuss the cause of the instability.