Induced circular dichroism of gold in the self-assembled polymeric nanoparticles

This study reports that the alkanethiol-capped golds loaded in the self-assembled polymeric nanoparticles exhibit the characteristic induced circular dichroism (ICD) in the near UV absorption region. The core-shell type polymeric nanoparticles composed of poly(y-benzyl L-glutamate) (PBLG) as hydrophobic inner core and poly(ethylene oxide) (PEO) as hydrophilic outer shell were obtained by the diafiltration method after dissolving PBLG/PEO block copolymer in organic solvent. The circular dichroism (CD) of alkanethiol-capped gold nanoparticles as the guest was induced by the chiral PBLG as the host in self-assembled polymeric nanoparticles with Cotton effect in the range of 220-230 nm whose crossing point matched lambda(max) in the UV region of alkanethiol-capped gold nanoparticles. Transmission electron microscopy and electrophoretic light scattering spectrophotometry were used to study the morphology and particle size of gold-loaded core-shell type polymeric nanoparticles, respectively. The results indicated that the PBLG chains in the block copolymer and alkanethiol-capped gold nanoparticles were associated together by hydrophobic interaction and chiral PBLG core in the self-assembled polymeric nanoparticles induced CD of the gold.