Chiral nanostructures have been attracting extensive interest in recent years primarily because of the unique materials properties that can be exploited for diverse applications. In this study, gold Janus nanoparticles, with hexanethiolates and 3-mercapto-1,2-propanediol segregated on the two hemispheres of the metal cores (dia. 2.7 ± 0.4 nm), self-assembled into vesicle-like, hollow nanostructures in both water and organic media, and exhibited apparent plasmonic circular dichroism (PCD) absorption in the visible range. This was in contrast to individual Janus nanoparticles, bulk-exchange nanoparticles where the two ligands were homogeneously mixed on the nanoparticle surface, or nanoparticles capped with only one kind of ligand. The PCD signals were found to become intensified with increasing coverage of the 3-mercapto-1,2-propanediol ligands on the nanoparticle surface. This was accounted for by the dipolar property of the structurally asymmetrical Janus nanoparticles, and theoretical simulations based on first principles calculations showed that when the nanoparticle dipoles self-assembled onto the surface of a hollow sphere, a vertex was formed which gave rise to the unique chiral characteristics. The resulting chiral nanoparticle vesicles could be exploited for the separation of optical enantiomers, as manifested in the selective identification and separation of d -alanine from the l -isomer.
more »
« less
Janus Nanoparticle Emulsions as Chiral Nanoreactors for Enantiomerically Selective Ligand Exchange
Janus nanoparticles capped with a hydrophobic and hydrophilic hemisphere of mercapto ligands can self‐assemble into hollow, emulsion‐like nanostructures in controlled media. As the nanoparticle emulsions are chiroptically active exhibiting a plasmonic circular dichroism absorption in the visible range, they can be exploited as a unique chiral nanoreactor by selective encapsulation of
- PAR ID:
- 10461352
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Particle & Particle Systems Characterization
- Volume:
- 36
- Issue:
- 5
- ISSN:
- 0934-0866
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Metal chalcogenide nanoparticles play a vital role in a wide range of applications and are typically stabilized by organic derivatives containing thiol, amine, or carboxyl moieties, where the nonconjugated particle–ligand interfaces limit the electronic interactions between the inorganic cores and organic ligands. Herein, a wet-chemistry method is developed for the facile preparation of stable platinum chalcogenide (S, Se) nanoparticles capped with acetylene derivatives (e.g., 4-ethylphenylacetylene, EPA). The formation of Pt–C≡ conjugated bonds at the nanoparticle interfaces, which is confirmed by optical and X-ray spectroscopic measurements, leads to markedly enhanced electronic interactions between the d electrons of the nanoparticle cores and π electrons of the acetylene moiety, in stark contrast to the mercapto-capped counterparts with only nonconjugated Pt–S– interfacial bonds, as manifested in spectroscopic measurements and density functional theory calculations. This study underscores the significance of conjugated anchoring linkages in the stabilization and functionalization of metal chalcogenides, a unique strategy for diverse applications.more » « less
-
The molecular features that dictate interactions between functionalized nanoparticles and biomolecules are not well understood. This is in part because for highly charged nanoparticles in solution, establishing a clear connection between the molecular features of surface ligands and common experimental observables such as ζ potential requires going beyond the classical models based on continuum and mean field models. Motivated by these considerations, molecular dynamics simulations are used to probe the electrostatic properties of functionalized gold nanoparticles and their interaction with a charged peptide in salt solutions. Counterions are observed to screen the bare ligand charge to a significant degree even at the moderate salt concentration of 50 mM. As a result, the apparent charge density and ζ potential are largely insensitive to the bare ligand charge densities, which fall in the range of ligand densities typically measured experimentally for gold nanoparticles. While this screening effect was predicted by classical models such as the Manning condensation theory, the magnitudes of the apparent surface charge from microscopic simulations and mean-field models are significantly different. Moreover, our simulations found that the chemical features of the surface ligand ( e.g. , primary vs. quaternary amines, heterogeneous ligand lengths) modulate the interfacial ion and water distributions and therefore the interfacial potential. The importance of interfacial water is further highlighted by the observation that introducing a fraction of hydrophobic ligands enhances the strength of electrostatic binding of the charged peptide. Finally, the simulations highlight that the electric double layer is perturbed upon binding interactions. As a result, it is the bare charge density rather than the apparent charge density or ζ potential that better correlates with binding affinity of the nanoparticle to a charged peptide. Overall, our study highlights the importance of molecular features of the nanoparticle/water interface and underscores a set of design rules for the modulation of electrostatic driven interactions at nano/bio interfaces.more » « less
-
null (Ed.)A mechanistic understanding of the influence of the surface properties of engineered nanomaterials on their interactions with cells is essential for designing materials for applications such as bioimaging and drug delivery as well as for assessing nanomaterial safety. Ligand-coated gold nanoparticles have been widely investigated because their highly tunable surface properties enable investigations into the effect of ligand functionalization on interactions with biological systems. Lipophilic ligands have been linked to adverse biological outcomes through membrane disruption, but the relationship between ligand lipophilicity and membrane interactions is not well understood. Here, we use a library of cationic ligands coated on 2 nm gold nanoparticles to probe the impact of ligand end group lipophilicity on interactions with supported phosphatidylcholine lipid bilayers as a model for cytoplasmic membranes. Nanoparticle adsorption to and desorption from the model membranes were investigated by quartz crystal microbalance with dissipation monitoring. We find that nanoparticle adsorption to model membranes increases with ligand lipophilicity. The effects of ligand structure on gold nanoparticle attachment were further analyzed using atomistic molecular dynamics simulations, which showed that the increase in ligand lipophilicity promotes ligand intercalation into the lipid bilayer. Together, the experimental and simulation results could be described by a two-state model that accounts for the initial attachment and subsequent conversion to a quasi-irreversibly bound state. We find that only nanoparticles coated with the most lipophilic ligands in our nanoparticle library undergo conversion to the quasi-irreversible state. We propose that the initial attachment is governed by interaction between the ligands and phospholipid tail groups, whereas conversion into the quasi-irreversibly bound state reflects ligand intercalation between phospholipid tail groups and eventual lipid extraction from the bilayer. The systematic variation of ligand lipophilicity enabled us to demonstrate that the lipophilicity of cationic ligands correlates with nanoparticle-bilayer adsorption and suggested that changing the nonpolar ligand R group promotes a mechanism of ligand intercalation into the bilayer associated with irreversible adsorption.more » « less
-
Using ligand exchange on FAPbI3 perovskite nanocrystals (PNCs) surface with chiral tridentate L-cysteine (Lcys) ligand, we successfully prepared chiral FAPbI3 PNCs that show circularly polarized luminescence (CPL) (dissymmetry factor; glum = 2.1 × 10−3) in the near-infrared (NIR) region from 700 to 850 nm and a photoluminescence quantum yield (PLQY) of 81%. The chiral characteristics of FAPbI3 PNCs are ascribed to induction by chiral L/D-cys, and the high PLQY is attributed to the passivation of the PNCs defects with L-cys. Also, effective passivation of defects on the surface of FAPbI3 PNCs by L-cys results in excellent stability toward atmospheric water and oxygen. The conductivity of the L-cys treated FAPbI3 NC films is improved, which is attributed to the partial substitution of L-cys for the insulating long oleyl ligand. The CPL of the L-cys ligand treated FAPbI3 PNCs film retains a glum of −2.7 × 10−4. This study demonstrates a facile yet effective approach to generating chiral PNCs with CPL for NIR photonics applications.more » « less
