Defining New Benchmarks of Low CTAB-Concentration-Based Gold Nanorod Synthesis: The Underestimated Potential of Polymer-Directed Anisotropic Growth

This work presents new anisotropic growth-directing copolymers suitable for the seed-mediated growth of gold nanorods (GNRs). Copolymers with different architectures are studied. They all contain dimethylaminomethyl methacrylate (DMAEMA) functionalized with 1-bromohexadecane (BHD) as the vital component. For the synthesis of the different copolymers, the photo-iniferter reversible addition-fragmentation chain transfer (photoRAFT) polymerization is used, where DMAEMA is combined with a lower critical solution temperature (LCST) polymer block for better solubility after the functionalization. The results show that the presented copolymers can induce anisotropic growth of gold nanoparticles. Additionally, the influence of the LCST of the water-soluble block and the temperature of the growth solution on the GNR synthesis are investigated. Furthermore, the plasmonic behavior of the resulting GNRs solution is investigated at temperatures around the LCST of the copolymer. Dimethylaminoethyl methacrylate (DMAEMA)-based copolymers showing a lower critical solution temperature (LCST) are presented, which allow anisotropic growth of gold nanoparticles at a reduced concentration of highly toxic cetyltrimethylammonium bromide (CTAB) of 99% within the growth solution of a seeded-growth approach. Due to the LCST of the copolymer matrix, the gold nanorods show a temperature-dependent plasmon shift in UV-vis spectra. image