Gold Nanoparticle Adsorption in Covalently Bonded Weak Polyelectrolyte Brushes

The adsorption of spherical citrate-coated gold nanoparticles (AuNPs) into poly(2-vinylpyridine) (P2VP) brushes was investigated using a quartz crystal microbalance with dissipation (QCM-D). This study examined the impacts of environmental pH and brush molecular weight (10 and 53 kg/mol) on AuNP adsorption kinetics and areal number densities. We synthesized and characterized the P2VP brushes, grafted onto a poly(glycidyl methacrylate) (PGMA) priming layer, on both silicon wafers and QCM-D sensors. Adsorption experiments explored the pH-dependent adsorption behavior of 10- and 20-nm diameter AuNPs. The QCM-D data show that higher molecular weight brushes enhanced AuNP uptake. At pH = 4.0, the swollen brushes promote greater adsorption compared with the collapsed brush state at pH = 6.2. This study highlights the advantages of the homopolymer brush architecture compared with the block copolymer brush architecture from our previous work. Additionally, it reaffirms the pH-mediated size selectivity observed in our prior study, where the smaller 10 nm AuNPs show preferential adsorption at higher pH. These findings provide insights into the impacts of brush molecular weight and environmental conditions on nanoparticle adsorption, with implications for designing smart surfaces for sensing and filtration applications.