Structure and Stability of PEG‐ and Mixed PEG‐Layer‐Coated Nanoparticles at High Particle Concentrations Studied In Situ by Small‐Angle X‐Ray Scattering

Schulz, Florian; Möller, Johannes; Lehmkühler, Felix; Smith, Andrew J.; Voßmeyer, Tobias; Lange, Holger; Grübel, G.; Schroer, Martin A.

doi:10.1002/ppsc.201700319

Cited by 19 publications

(34 citation statements)

References 55 publications

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“…To precisely model nanorods, some authors had to use a combination of form-factors [ 117 ]. To take into account interactions between nanorods, a structure-factor can also be combined to the form-factor [ 118 ]. Unfortunately, very thin silica coating cannot be efficiently characterized through this technique, as its scattering contribution is not significant enough, but thicker layers should be quantifiable if modelled with the appropriate form factor, as well as more complicated structures (e.g., core/satellite superstructures in [ 119 ]).…”

Section: Methods Of Characterizationmentioning

confidence: 99%

Gold Nanorods for LSPR Biosensing: Synthesis, Coating by Silica, and Bioanalytical Applications

Pellas

Mazouzi

et al. 2020

Biosensors

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Nanoparticles made of coinage metals are well known to display unique optical properties stemming from the localized surface plasmon resonance (LSPR) phenomenon, allowing their use as transducers in various biosensing configurations. While most of the reports initially dealt with spherical gold nanoparticles owing to their ease of synthesis, the interest in gold nanorods (AuNR) as plasmonic biosensors is rising steadily. These anisotropic nanoparticles exhibit, on top of the LSPR band in the blue range common with spherical nanoparticles, a longitudinal LSPR band, in all respects superior, and in particular in terms of sensitivity to the surrounding media and LSPR-biosensing. However, AuNRs synthesis and their further functionalization are less straightforward and require thorough processing. In this paper, we intend to give an up-to-date overview of gold nanorods in LSPR biosensing, starting from a critical review of the recent findings on AuNR synthesis and the main challenges related to it. We further highlight the various strategies set up to coat AuNR with a silica shell of controlled thickness and porosity compatible with LSPR-biosensing. Then, we provide a survey of the methods employed to attach various bioreceptors to AuNR. Finally, the most representative examples of AuNR-based LSPR biosensors are reviewed with a focus put on their analytical performances.

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Section: Methods Of Characterizationmentioning

confidence: 99%

Gold Nanorods for LSPR Biosensing: Synthesis, Coating by Silica, and Bioanalytical Applications

Pellas

Mazouzi

et al. 2020

Biosensors

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“…a significant decrease of the degree of orientational order. In addition, MUA addition leads to different ligand layer conformations that affect the stability of the particles (Schulz et al, 2018). Obviously, this way the assembly of layers in the (sub-)micrometre range as studied in this work is affected as well.…”

Section: Discussionmentioning

confidence: 93%

Local orientational order in self-assembled nanoparticle films: the role of ligand composition and salt

Lehmkühler¹,

Schulz²,

Schroer³

et al. 2019

J Appl Cryst

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An X-ray cross-correlation study of the local orientational order in selfassembled films made from PEGylated gold nanoparticles is presented. The local structure of this model system is dominated by four-and sixfold order. Coadsorption of shorter ligands in the particle's ligand layer and variation of salt concentration in the suspension prior to self-assembly result in a change of local orientational order. The degree of sixfold order is reduced after salt addition. This decrease of order is less pronounced for the fourfold symmetry. The results presented here suggest complex symmetry-selective order formation upon ligand exchange and salt addition and demonstrate the versatility of X-ray crosscorrelation methods for nanoparticle superlattices. research papers J. Appl. Cryst. (2019). 52, 777-782 Felix Lehmkü hler et al. Local orientational order in self-assembled nanoparticle films 781

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“…As shown previously, SAXS measurements are dominantly sensitive to the Au core, as the ligand shell has a much weaker scattering contrast. 20,33,34 With increasing hydrostatic pressure up to p = 2000 bar (200 MPa), only slight changes of the SAXS profile are present. In particular, the form factor does not change, while the intensity of the structure factor peak drops and the peak position shifts slightly to larger scattering angles (q max ≈ 0.17 nm −1 ).…”

Section: Resultsmentioning

confidence: 99%

“…We note that PEG high grafting densities are critical to achieve concentrations of AuNR@PEG as used in this study and that the specific PEG-ligand used, PEGMUA2k, allows for such high grafting densities. 34,37 For the crystal state, the ligand shell thickness can be determined as t = a/2 − R mean , which yields t = 7.0 -7.5 nm, pointing to a still hydrated PEG-shell. It is thus likely that not only attractive van der Waals interactions between the AuNR cores, but also the interactions between PEG-shells determine the crystallization.…”

Section: Resultsmentioning

confidence: 99%

“…This collapse of the ligand shell is accompanied by an increase of the attractive interparticle interactions, 33,34 resulting in the supercrystal formation. Having investigated in detail the role of different salt types and concentrations and ligand lengths, ideal conditions for the supercrystal formation of spherical nanoparticles have been determined.…”

Section: Introductionmentioning

confidence: 99%

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Supercrystal Formation of Gold Nanorods by High Pressure Stimulation

et al. 2019

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We demonstrate the pressure-induced formation of supercrystals made from PE-Gylated gold nanorods in aqueous suspension. Utilizing the combined effect of hydrostatic pressure and salt on the solubility of the organic PEG shell that passivates the nanorods, the reversible formation of two-dimensional hexagonal supercrystals has been observed by means of small angle X-ray scattering. The pressure dependence of the crystal lattice's structural parameters is determined. By time-resolved measurements performed after a pressure-jump, the growth process of the crystals is found to be finished already after a few seconds. The presented results demonstrate that by PEGylating nanoparticles pressure-induced homogeneous supercrystals can be formed for different particle shapes, in particular anisotropic nanorods, which determine the resulting lattice type.

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Structure and Stability of PEG‐ and Mixed PEG‐Layer‐Coated Nanoparticles at High Particle Concentrations Studied In Situ by Small‐Angle X‐Ray Scattering

Cited by 19 publications

References 55 publications

Gold Nanorods for LSPR Biosensing: Synthesis, Coating by Silica, and Bioanalytical Applications

Gold Nanorods for LSPR Biosensing: Synthesis, Coating by Silica, and Bioanalytical Applications

Local orientational order in self-assembled nanoparticle films: the role of ligand composition and salt

Supercrystal Formation of Gold Nanorods by High Pressure Stimulation

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