Self-Assembled Hyperbranched Polymer–Gold Nanoparticle Hybrids: Understanding the Effect of Polymer Coverage on Assembly Size and SERS Performance

Abstract

In the past few years, remarkable progress has been made in unveiling novel and unique optical properties of strongly coupled plasmonic nanostructures. However, the application of such plasmonic nanostructures in biomedicine remains challenging because of the lack of facile and robust assembly methods for producing stable nanostructures. Previous attempts to achieve plasmonic nanoassemblies using molecular ligands were limited by the lack of flexibility that could be exercised in forming them. Here, we report the utilization of tailor-made hyperbranched polymers (HBP) as linkers to assemble gold nanoparticles (NPs) into nanoassemblies. The ease and flexibility in tuning the particle size and number of branch ends of an HBP make it an ideal candidate as a linker, as opposed to DNA, small organic molecules, and linear or dendrimeric polymers. We report a strong correlation of polymer (HBP) concentration with the size of the hybrid nanoassemblies and "hot-spot" density. We have shown that such solutions of stable HBP-gold nanoassemblies can be barcoded with various Raman tags to provide improved surface-enhanced Raman scattering (SERS) compared to that of nonaggregated NP systems. These Raman-barcoded hybrid nanoassemblies, with further optimization of the NP shape, size, and hot-spot density, may find application as diagnostic tools in nanomedicine.

How to accurately predict solution-phase gold nanostar stability

“…Previously, localized surface plasmon resonance (LSPR) spectroscopy revealed that the morphology of gold nanostars changed during storage [19]. Furthermore, both supporting electrolyte composition and concentration as well as surface functionalization with molecules such as PEG [24], PVP [25], PSS-PDD multilayers [26], and hyperbranched polymers [27] improved nanostar stability. These functionalized nanostructures provide excellent examples as to why nanostructure stability is important in analytical applications.…”

Hydrophilic packaging of iron oxide nanoclusters for highly sensitive imaging

“…24 Size has been shown to vary with polymer content during fabrication, 25–28 however, clusters made with HPG 3k -g-C 18 (5) or LPG 3k -g-C 18 (2) remained 80 nm, regardless of concentration (Figure S9), with core diameters of approximately 40 nm and 60 nm respectively. To strengthen potential HPG-mediated inter-droplet interactions, 29 a larger HPG with a molecular weight of 50 kg/mol, termed HPG 50k , was synthesized by increasing the ratio of glycidol-to-initiator in the polymerization reaction (Figure S1a).…”

RAFT synthesis of block copolymers and their self-assembly properties

“…Raman and FTIR spectroscopy-established techniques for in situ reaction monitoring-have been used to good advantage in polymerization processes (Gulari et al, 1984;Dey et al, 2013). We have utilized Raman in situ monitoring to determine the real time trajectory of monomer content in the reactor.…”