Abstract
Thermal desolvation of poly(N-isopropylacrylamide) (PNIPAM) in the presence of a low concentration of gold nanoparticles incorporates the nanoparticles resulting in suspended aggregates. By covalently incorporating <1% acenaphthylene into the polymerization feed this copolymer is enabled to be used as a model to study the segmental mobility of the PNIPAM backbone in response to gold nanoparticles both below and above the desolvation temperature, showing that there is a physical conformational rearrangement of the soluble polymer at ultralow nanoparticle loadings, indicating low affinity interactions with the nanoparticles. Thermal desolvation is capable of extracting >99.9% of the nanoparticles from their solutions and hence demonstrates that poly(N-isopropylacrylamide) can act as an excellent scrubbing system to remove metallic nanomaterial pollutants from solution.
Highlights
Conformational responses to stimuli have allowed us to carry coated nanoparticles have previously been investigated and the out experimental trials on polymer/gold nanoparticle interac- polymer-coating was observed to retain its responsive properties, tions at low concentrations; to investigate the physical response changing in volume as the nanoparticles were driven across the of the temperature responsive, azo-initiated poly(N-isopropyl polymer’s little emphasis being placed critical solution temperature (LCST).[18]
This was verified by heating a solution of mixed P(NIPAM-co-ACE) and Au nanoparticles from 10 to 50 °C and measuring the lifetime of the ACE label in order to contrast the collapse of the polymer with temperature (Figure 3f)
As the data indicates that the stimuli-driven thermal desolvation of PNIPAM into aggregate particles incorporates nanoparticles from solution further tests were carried out to investigate the efficacy of removal of Au nanoparticles from solution
Summary
Synthetic and instrumental details, including the synthesis of P(NIPAM-co-ACE) and the Au nanoparticles, are contained within the Supporting Information. The decrease in fluorescence lifetime at room temperature occurs with a polymer in an extended conformation This was verified by heating a solution of mixed P(NIPAM-co-ACE) and Au nanoparticles from 10 to 50 °C and measuring the lifetime of the ACE label in order to contrast the collapse of the polymer with temperature (Figure 3f). Addition of the nanoparticles decreases the lifetime of the polymer-ACE fluorescence decay by a few nanoseconds below the LCST but a marked decrease was observed at higher temperatures as the desolvating polymer incorporated the gold nanoparticles into the aggregates as they formed following the coil-to-globule transition of the macromolecule. Förster resonance energy transfer calculations indicate that the maximum average label—nanoparticle surface separation within the globule is ≈3 nm
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