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Peptide-Directed Assembly of Single-Helical Gold Nanoparticle Superstructures Exhibiting Intense Chiroptical Activity.

ABSTRACT: Chiral nanoparticle assemblies are an interesting class of materials whose chiroptical properties make them attractive for a variety of applications. Here, C18-(PEPAuM-ox)2 (PEPAuM-ox = AYSSGAPPMoxPPF) is shown to direct the assembly of single-helical gold nanoparticle superstructures that exhibit exceptionally strong chiroptical activity at the plasmon frequency with absolute g-factor values up to 0.04. Transmission electron microscopy (TEM) and cryogenic electron tomography (cryo-ET) results indicate that the single helices have a periodic pitch of approximately 100 nm and consist of oblong gold nanoparticles. The morphology and assembled structure of C18-(PEPAuM-ox)2 are studied using TEM, atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD) spectroscopy, X-ray diffraction (XRD), and solid-state nuclear magnetic resonance (ssNMR) spectroscopy. TEM and AFM reveal that C18-(PEPAuM-ox)2 assembles into linear amyloid-like 1D helical ribbons having structural parameters that correlate to those of the single-helical gold nanoparticle superstructures. FTIR, CD, XRD, and ssNMR indicate the presence of cross-? and polyproline II secondary structures. A molecular assembly model is presented that takes into account all experimental observations and that supports the single-helical nanoparticle assembly architecture. This model provides the basis for the design of future nanoparticle assemblies having programmable structures and properties.

SUBMITTER: Merg AD

PROVIDER: S-EPMC5388601 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Peptide-Directed Assembly of Single-Helical Gold Nanoparticle Superstructures Exhibiting Intense Chiroptical Activity.

Merg Andrea D AD Boatz Jennifer C JC Mandal Abhishek A Zhao Gongpu G Mokashi-Punekar Soumitra S Liu Chong C Wang Xianting X Zhang Peijun P van der Wel Patrick C A PCA Rosi Nathaniel L NL

Journal of the American Chemical Society 20161011 41

Chiral nanoparticle assemblies are an interesting class of materials whose chiroptical properties make them attractive for a variety of applications. Here, C18-(PEPAuM-ox)2 (PEPAuM-ox = AYSSGAPPMoxPPF) is shown to direct the assembly of single-helical gold nanoparticle superstructures that exhibit exceptionally strong chiroptical activity at the plasmon frequency with absolute g-factor values up to 0.04. Transmission el ...[more]

PMID: 27726354

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Project description:Photon-to-matter chirality transfer offers both simplicity and universality to chiral synthesis, but its efficiency is typically low for organic compounds. Besides the fundamental importance of this process relevant for understanding the origin of homochirality on Earth, new pathways for imposing chiral bias during chemical process are essential for a variety of technologies from medicine to informatics. The strong optical activity of inorganic nanoparticles (NPs) affords photosynthetic routes to chiral superstructures using circularly polarized photons. Although plasmonic NPs are promising candidates for such synthetic routes due to the strong rotatory power of highly delocalized plasmonic states (Ma et al. Chem. Rev. 2017, 117 (12), 8041), realization of light-driven synthesis of chiral nanostructures has been more challenging for plasmonic NPs than for the semiconductor due to the short lifetime of the plasmonic states. Here we show that illumination of gold salt solutions with circularly polarized light induces the formation of NPs and their subsequent assembly into chiral nanostructures 10-15 nm in diameter. Despite their seemingly irregular shape, the resulting nanocolloids showed circular dichroism (CD) spectra with opposite polarity after exposure to photons with left and right circular polarization. The sign and spectral position of the CD peaks of illuminated dispersions matched those calculated for nanostructures with complex geometry identified from electron tomography images. Quantification of the complex shapes of NP assemblies using chirality measures revealed a direct correlation with the experimental spectra. The light-driven assembly of chiral nanostructures originates from the asymmetric displacement of NPs in dynamic assemblies by plasmonic fields followed by particle-to-particle attachment. The ability of gold NPs to "lock" the chirality of the incident photons in assembled nanostructures can be used to create a variety of chiral nanomaterials with plasmonic resonances.

Dataset Information

Peptide-Directed Assembly of Single-Helical Gold Nanoparticle Superstructures Exhibiting Intense Chiroptical Activity.

Publications

Peptide-Directed Assembly of Single-Helical Gold Nanoparticle Superstructures Exhibiting Intense Chiroptical Activity.

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