Hyperbranched polylysine: Synthesis, mechanism and preparation for NIR-absorbing gold nanoparticles

• Published in: Chinese chemical letters 2019-07, Vol.30 (7), p.1428-1431
• Main Authors: Ge, Yiying, Li, Pan, Guan, Yanfei, Dong, Chang-Ming
• Format: Article
• Language: English
• Subjects: Gold nanoparticles; Hyperbranched polylysine; NCA; NIR; ROP
• ISSN: 1001-8417; 1878-5964
• DOI: 10.1016/j.cclet.2019.03.009

The hyperbranched polylysine fluoroborate was synthesized by NH3BF4-Lys NCA ROP in triethylamine at 15 °C, during which the cyclic dimer mainly initiated ROP as the secondary initiating species. The hyperbranched polylysine can be used as a stabilizer to prepare the NIR-absorbing HPlys@Au NPs. [Display omitted] The ring-opening polymerization (ROP) of N-(tetrafluoroboran ammonium)-l-lysine-N-carboxyanhydride (NH3BF4-Lys NCA) was initiated by triethylamine to prepare hyperbranched polylysine (HPlys) fluoroborate with narrow polydispersity at a low temperature. Both mass spectroscopy analysis and DFT computation evidenced that the resultant cyclic dimer mainly initiated ROP as a secondary species according to normal amine mechanism. The hyperbranched polylysine in aqueous solution existed in a unimolecular state at low concentrations, but transformed into spherical micellar aggregates at a high concentration of 5 mg/mL, as characterized by dynamic laser scattering and transmission electron microscopy. By utilizing multivalent coordination interactions between hyperbranched polylysine and gold, the plasmonic gold nanoparticles (HPlys@Au NPs) were successfully prepared in aqueous solution, which elevated the solution by 23.1 °C upon 5 min of NIR laser irradiation (808 nm, 2 W/cm2).