Thermoresponsive nanoparticle agglomeration/aggregation in salt solutions: Dependence on graft density
Thaddeus W Vasicek1, Samir V Jenkins2, Leticia Vaz1
1Department of Chemistry and Biochemistry, University of Arkansas, 345 N Campus Dr., Fayetteville, AR 72701, United States.
Journal of Colloid and Interface Science
|July 26, 2017
Summary
Polymer graft density on gold nanoparticles dictates their stability in salt solutions. Higher densities allow reversible agglomeration, while lower densities lead to irreversible aggregation, highlighting the need for multiple characterization techniques.
Area of Science:
- Nanotechnology
- Materials Science
- Polymer Chemistry
Background:
- Thermoresponsive polymers like poly(N-isopropylacrylamide) are used to coat nanoparticles.
- The stability of these polymer-coated nanoparticles in salt solutions is crucial for their applications.
- Previous studies have shown conflicting results regarding the reversibility of nanoparticle agglomeration.
Purpose of the Study:
- To investigate the effect of poly(N-isopropylacrylamide) graft density on the thermoresponsive behavior and stability of gold nanoparticles in 50mM NaCl.
- To determine the reversibility of nanoparticle agglomeration at different graft densities.
- To reconcile conflicting findings in the literature regarding the reversibility of polymer-nanoparticle agglomeration.
Main Methods:
- Synthesis of gold nanoparticles with varying poly(N-isopropylacrylamide) graft densities (0.09, 0.30, 0.40 chains/nm²).
- Characterization using localized surface plasmon resonance (LSPR), hydrodynamic diameter measurements, and electron microscopy.
- Assessment of agglomeration and aggregation behavior at room temperature and 37°C in 50mM NaCl.
- Evaluation of agglomerate dispersibility using sonication.
Main Results:
- Nanoparticles were stable at room temperature but agglomerated at 37°C.
- Particles with graft densities of 0.30 and 0.40 chains/nm² showed reversible agglomeration dispersible by sonication.
- Particles with a graft density of 0.09 chains/nm² exhibited irreversible aggregation.
- Discrepancies were observed between LSPR and hydrodynamic diameter measurements for determining agglomeration reversibility.
Conclusions:
- Polymer graft density significantly influences the thermoresponsive stability and aggregation behavior of gold nanoparticles in salt solutions.
- Lower graft densities lead to irreversible aggregation due to altered steric effects.
- The use of complementary techniques is essential for accurately assessing nanoparticle agglomeration reversibility.
- This study clarifies the factors governing the stability of thermoresponsive polymer-nanoparticle systems.
