9 research outputs found
Antioxidation Properties and Surface Interactions of Polyvinylpyrrolidone-Capped Zerovalent Copper Nanoparticles Synthesized in Supercritical Water
Zerovalent copper nanoparticles (CuNPs)
(diameter, 26.5 ± 9 nm) capped with polyvinylpyrrolidone (PVP)
were synthesized in supercritical water at 400 °C and 30 MPa
with a continuous flow reactor. The PVP-capped CuNPs were dispersed
in distilled water, methanol, ethanol, 1-propanol, 2-propanol, butanol,
and their mixed solvents to study their long-term stability. Temporal
variation of UV–vis spectra and surface plasmon resonance were
measured and showed that ethanol, the propanols, and butanol solvents
provided varying degrees of oxidative protection for Cu<sup>0</sup>. Fourier transform infrared spectroscopy showed that PVP adsorbed
onto the surface of the CuNPs with a pyrrolidone ring of PVP even
if the CuNPs were oxidized. Intrinsic viscosities of PVP were higher
for solvents that provided antioxidation protection than those that
give oxidized CuNPs. In solvents that provided Cu<sup>0</sup> with
good oxidative protection (ethanol, the propanols, and butanol), PVP
polymer chains formed large radii of gyration and coil-like conformations
in the solvents so that they were arranged uniformly and orderly on
the surface of the CuNPs and could provide protection of the Cu<sup>0</sup> surface against dissolved oxygen. In solvents that provided
poor oxidative protection for Cu<sup>0</sup> (water, alcohol–water
mixed solvents with 30% water), PVP polymer chains had globular-like
conformations due to their relatively high hydrogen-bonding interactions
and sparse adsorption onto the CuNP surface. Antioxidative properties
of PVP-capped CuNPs in a solvent can be ascribed to the conformation
of PVP polymer chains on the Cu<sup>0</sup> particle surface that
originates from the interaction between polymer chains and its interaction
with the solvent