Au@poly(N-propargylamide) nanoparticles: preparation and chiral recognition

This communication reports the first gold nanoparticles (NPs) chirally functionalized with optically active helical substituted polyacetylene (the resulting hybrid particles are defined as Au@PPA NPs). The novel nanoparticles consist of gold as core and optically active helical poly(N-propargylamide) as shell and show considerable optical activity derived from helical poly(N-propargylamide) chains with predominantly one-handed screw sense. The Au@PPA NPs are prepared by a three-step approach: i) a thiol-containing N-propargylamide monomer [Mth , HC≡CCH2 NHCO(CH2 )10 SH] is synthesized and characterized with FTIR and(1) HNMR spectroscopy and elemental analysis; ii) a copolymer (poly(Mth -co-Mch )) was prepared by starting from monomer Mth and another chiral N-propargylamide monomer (Mch ); poly(Mth -co-Mch ) formed helical conformations and showed optical activities; and, iii) Au@PPA NPs are prepared from hydrogen tetrachloroaurate (III) and poly(Mth -co-Mch ) through a one-spot procedure by using LiBH4 as reducing agent. The as-obtained hybrid nanoparticles are characterized by FTIR spectroscopy, TEM, UV-vis absorption and circular dichroism (CD) techniques. UV-vis and CD measurements demonstrated the remarkable optical activity of the Au@PPA NPs. More interestingly, the Au@PPA NPs show much stronger UV-vis and CD sigals when compared to the corresponding orginal helical copolymer, poly(Mth -co-Mch ). The chiral hybrid nanoparticles demonstrate different absorption toward (R)-(+)- and (S)-(-)-1-phenylethylamines, preferentially adsorbing the (S)-isomer.