Surface Asymmetry of Coated Spherical Nanoparticles

Koch, Amelie H. R.; Lévêque, Gaëtan; Harms, Sebastian; Jaskiewicz, Karmena; Bernhardt, Max; Henkel, Andreas; Sönnichsen, Carsten; Landfester, Katharina; Fytas, George

doi:10.1021/nl501783x

Cited by 32 publications

(48 citation statements)

References 32 publications

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“…In fact, recent simulation, theory and experiments suggest that, for small number of grafts, their spatial distribution on spherical NPs is anisotropic and asymmetric. 15,16,28 On the other hand, . Interparticle core−core London dispersion potential (V/ k B T) as a function of separation (h) between the outer layers of the particles.…”

Section: Acs Macro Lettersmentioning

confidence: 99%

Self-Assembly of Monodisperse versus Bidisperse Polymer-Grafted Nanoparticles

et al. 2016

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We systematically compare the dispersion and self-assembly of silica nanoparticles (NPs) grafted with either a sparse monomodal long chain length polystyrene (PS) brush or a bimodal brush comprised of a sparse grafting of long PS chains and a dense carpet of short poly(2-vinylpyridine) (P2VP) chains. These two different types of NPs are placed in pure PS matrices of varying molecular weights in a series of experiments. We first show that NP dispersion is generally improved in the case of bimodal brushes. More interestingly, at low PS grafting densities the bimodal brushes give different self-assembled structures relative to the monomodal brushes; we conjecture that the presence of the short P2VP chains in the bimodal brush reduces the effective core−core attractions and thus allows these bidisperse NPs to display self-assembly behavior that is less likely to be kinetically trapped by the strong intercore attractions that control the behavior of monomodal NPs. In this low PS grafting density limit, where we expect the spatial coverage of the brush to be the most nonuniform, we find the formation of "vesicular" structures that are representative of highly asymmetric ("tadpole") surfactants. Our results therefore show that reducing the inter-NP attractions gives rise to a much richer ensemble of NP self-assemblies, apparently with a smaller influence from kinetic traps (or barriers). P olymer nanocomposites (PNCs), mixtures of nanometersized particles and polymer matrices, have attracted continuing interest over the past few decades, primarily because they offer the promise of significant property improvements relative to the pure polymer. 1−6 The mixing of inorganic nanoparticles (NP) with typically hydrophobic polymers, however, is challenging because of their strong energetic dislike for each other. One common strategy to improve their miscibility is to covalently graft the NP surface with polymer chains possessing the same chemistry as the matrix. 7−9 Initially, monomodal 10−12 brushes were used to control particle/ polymer miscibility. Interestingly, in these systems, anisotropic NP morphologies (strings, sheets, or connected structures) were observed when the NPs were sparsely grafted with polymer chains. 11,13,14 This finding was reconciled by the fact that lightly grafted NPs act akin to surfactants, that is, some parts of the particle surface are covered by the grafted chains ("hydrophobic"), while the other hydrophilic parts are exposed to the matrix. 15,16 Very recently bimodal brushes, consisting of a densely grafted, short brush (enthalpic screening for core− core attraction) and a sparsely grafted, long brush (favorable entropic interactions with the matrix chains) have been studied as a route to further improve NP dispersion. 17−21 Again, all the chains were of the same chemistry. These bimodal polymer grafted NPs were found to be well-dispersed across a broad range of matrix molecular weights, a fact that is attributed to the significant reduction in attraction between the particles due to the presen...

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Section: Acs Macro Lettersmentioning

confidence: 99%

Self-Assembly of Monodisperse versus Bidisperse Polymer-Grafted Nanoparticles

et al. 2016

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“…A comparison of coarse-grained and atomistic simulations was used to demonstrate that such fluctuation-driven anisotropy was necessary to explain the formation of stringlike assemblies in this system. 22 In the case of aqueous dispersions of isotropically coated gold nanoparticles, localized surface plasmon resonance-enhanced dynamic light scattering experiments demonstrate a contribution to surface asymmetry due to ligand fluctuations; 23 extension and refinement of this approach to various nanoparticle systems offers the possibility of testing the role of this source of anisotropy on selfassembly.…”

Section: Introductionmentioning

confidence: 99%

Fluctuation-driven anisotropy in effective pair interactions between nanoparticles: Thiolated gold nanoparticles in ethane

Jabes

Yadav

Kumar

et al. 2014

The Journal of Chemical Physics

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Fluctuations within the ligand shell of a nanoparticle give rise to a significant degree of anisotropy in effective pair interactions for low grafting densities [B. Bozorgui, D. Meng, S. K. Kumar, C. Chakravarty, and A. Cacciuto, Nano Lett. 13, 2732 (2013)]. Here, we examine the corresponding fluctuation-driven anisotropy for gold nanocrystals densely passivated with short ligands. In particular, we consider gold nanocrystals capped by alkylthiols, both in vacuum and in ethane solvent at high density. As in the preceding study, we show that the anisotropy in the nanoparticle pair potential can be quantified by an angle-dependent correction term to the isotropic potential of mean force (PMF). We find that the anisotropy of the ligand shells is distance dependent, and strongly influenced by ligand interdigitation effects as well as expulsion of ligand chains from the interparticle region at short distances. Such fluctuation-driven anisotropy can be significant for alkylthiol-coated gold nanoparticles, specially for longer chain lengths, under good solvent conditions. The consequences of such anisotropy for self-assembly, specially as a function of grafting density, solvent quality and at interfaces, should provide some interesting insights in future work. Our results clearly show that an isotropic two-body PMF cannot adequately describe the thermodynamics and assembly behavior of nanoparticles in this dense grafting regime and inclusion of anisotropic effects, as well as possibly many-body interactions, is necessary. Extensions of this approach to other passivated nanoparticle systems and implications for self-assembly are considered.

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“…This decrease could be due to the deposition of a less densely packed PDA layer after 10 cycles reducing the overall mechanical film properties. [ 47 ] Prior studies of PDA films prepared by dip coating and measured by the compressive thin film buckling contact technique reported an elastic modulus of about 2 GPa for a film thickness of about 25 nm. [ 31 ] The PDA films reported herein revealed much higher elastic moduli at lower thickness (10, 13, 16 nm) and the freestanding PDA films formed after 5 and 10 cycles show elastic moduli within the same range as carbon nanomembranes.…”

Section: Resultsmentioning

confidence: 99%

Ultrathin Polydopamine Films with Phospholipid Nanodiscs Containing a Glycophorin A Domain

D'Alvise

Harvey

Hueske

et al. 2020

Adv Funct Materials

Self Cite

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Cellular membranes have long served as an inspiration for nanomaterial research. The preparation of ultrathin polydopamine (PDA) films with integrated protein pores containing phospholipids and an embedded domain of a membrane protein glycophorin A as simplified cell membrane mimics is reported. Large area, ultrathin PDA films are obtained by electropolymerization on gold surfaces with 10-18 nm thickness and dimensions of up to 2.5 cm 2 . The films are transferred from gold to various other substrates such as nylon mesh, silicon, or substrates containing holes in the micrometer range, and they remain intact even after transfer. The novel transfer technique gives access to freestanding PDA films that remain stable even at the air interfaces with elastic moduli of ≈6-12 GPa, which are higher than any other PDA films reported before. As the PDA film thickness is within the range of cellular membranes, monodisperse protein nanopores, so-called "nanodiscs," are integrated as functional entities. These nanodisc-containing PDA films can serve as semipermeable films, in which the embedded pores control material transport. In the future, these simplified cell membrane mimics may offer structural investigations of the embedded membrane proteins to receive an improved understanding of protein-mediated transport processes in cellular membranes.

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Surface Asymmetry of Coated Spherical Nanoparticles

Cited by 32 publications

References 32 publications

Self-Assembly of Monodisperse versus Bidisperse Polymer-Grafted Nanoparticles

Self-Assembly of Monodisperse versus Bidisperse Polymer-Grafted Nanoparticles

Fluctuation-driven anisotropy in effective pair interactions between nanoparticles: Thiolated gold nanoparticles in ethane

Ultrathin Polydopamine Films with Phospholipid Nanodiscs Containing a Glycophorin A Domain

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