Abstract
The adsorption of the thermoresponsive positively charged copolymer poly(N-isopropylacrylamide)-block-poly(3-acrylamidopropyl)trimethylammonium chloride, PNIPAAM48-b-PAMPTMA6(+), onto negatively charged gold nanoparticles can provide stability to the nanoparticles and make the emerging structure tunable by temperature. In this work, we characterize the nanocomposite formed by gold nanoparticles and copolymer chains and study the influence of the copolymer on the expected aggregation process that undergoes those nanoparticles at high ionic strength. We also determine the lower critical solution temperature (LCST) of the copolymer (around 42 °C) and evaluate the influence of the temperature on the nanocomposite. For those purposes, we use dynamic light scattering, UV-vis spectroscopy and transmission electron microscopy. At the working PNIPAAM48-b-PAMPTMA6(+) concentration, we observe the existence of copolymer structures that trap the gold nanoparticles and avoid the formation of nanoparticles aggregates. Finally, we discuss how these structures can be useful in catalysis and nanoparticles recovery.
Highlights
Gold nanoparticles (AuNPs) with their unique functional properties and easy synthesis have attracted much attention and promoted a variety of applications in biomedicine [1], catalysis [2], colorimetric sensing [3], environmental remediation [4], etc
An interesting type of polymer is the temperature-sensitive poly(N-isopropylacrylamide), or PNIPAAM, because its structural features can be tuned by temperature [9]
It is well-known that high-molecular-weight PNIPAAM dissolved in water undergoes coil-to-globule transition when the temperature exceeds its lower critical solution temperature, LCST ≈ 32 ◦ C [10]
Summary
Gold nanoparticles (AuNPs) with their unique functional properties and easy synthesis have attracted much attention and promoted a variety of applications in biomedicine [1], catalysis [2], colorimetric sensing [3], environmental remediation [4], etc. A solution is to add some polymer that is adsorbed onto the nanoparticle surface and gives rise to a core-shell nanoparticle [6,7] or forms some type of network that protects the nanoparticle [8]. For such a purpose, an interesting type of polymer is the temperature-sensitive poly(N-isopropylacrylamide), or PNIPAAM, because its structural features can be tuned by temperature [9].
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