| 1. |
- Bergman, Maxime J., et al.
(author)
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A new look at effective interactions between microgel particles
- 2018
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:5039
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Journal article (peer-reviewed)abstract
- Thermoresponsive microgels find widespread use as colloidal model systems, because their temperature-dependent size allows facile tuning of their volume fraction in situ. However, an interaction potential unifying their behavior across the entire phase diagram is sorely lacking. Here we investigate microgel suspensions in the fluid regime at different volume fractions and temperatures, and in the presence of another population of small microgels, combining confocal microscopy experiments and numerical simulations. We find that effective interactions between microgels are clearly temperature dependent. In addition, microgel mixtures possess an enhanced stability compared to hard colloid mixtures - a property not predicted by a simple Hertzian model. Based on numerical calculations we propose a multi-Hertzian model, which reproduces the experimental behavior for all studied conditions. Our findings highlight that effective interactions between microgels are much more complex than usually assumed, displaying a crucial dependence on temperature and on the internal core-corona architecture of the particles.
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| 2. |
- Meijer, Janne Mieke, et al.
(author)
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Phase Behavior of Bowl-Shaped Colloids : Order and Dynamics in Plastic Crystals and Glasses
- 2018
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In: Small. - : Wiley. - 1613-6810. ; 14:46
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Journal article (peer-reviewed)abstract
- Charged fluorescent bowl-shaped colloids consisting of a polystyrene core surrounded by a poly(N-isopropylmethacrylamide) shell are obtained by nanoengineering spherical composite microgels. The phase diagram of these soft bowl-shaped colloids interacting through long-range Yukawa-type interactions is investigated using confocal laser scanning microscopy. The bowl-shaped structure leads to marked differences in phase-behavior compared to their spherical counterpart. With increasing number density, a transition from a fluid to a plastic crystal phase, with freely rotating particles, followed by a glass-like state is observed. It is found that the anisotropic bowl shape frustrates crystallization and slows down crystallization kinetics and causes the glass-like transition to shift to a significantly lower volume fraction than for the spheres. Quantitative analysis of the positional and orientational order demonstrates that the plastic crystal phase exhibits quasi-long range translational order and orientational disorder, while in the disordered glass-like phase the long-range translational order vanishes and short-range rotational order appears, dictated by the specific bowl shape. It is further shown that the different structural transitions are characterized by decoupling of the translational and orientational dynamics.
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| 3. |
- Mukharamova, Nastasia, et al.
(author)
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Femtosecond laser produced periodic plasma in a colloidal crystal probed by XFEL radiation
- 2020
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Journal article (peer-reviewed)abstract
- With the rapid development of short-pulse intense laser sources, studies of matter under extreme irradiation conditions enter further unexplored regimes. In addition, an application of X-ray Free-Electron Lasers (XFELs) delivering intense femtosecond X-ray pulses, allows to investigate sample evolution in IR pump - X-ray probe experiments with an unprecedented time resolution. Here we present a detailed study of the periodic plasma created from the colloidal crystal. Both experimental data and theory modeling show that the periodicity in the sample survives to a large extent the extreme excitation and shock wave propagation inside the colloidal crystal. This feature enables probing the excited crystal, using the powerful Bragg peak analysis, in contrast to the conventional studies of dense plasma created from bulk samples for which probing with Bragg diffraction technique is not possible. X-ray diffraction measurements of excited colloidal crystals may then lead towards a better understanding of matter phase transitions under extreme irradiation conditions.
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| 4. |
- Petukhov, Andrei, et al.
(author)
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Particle shape effects in colloidal crystals and colloidal liquid crystals: Small-angle X-ray scattering studies with microradian resolution
- 2015
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In: Current Opinion in Colloid & Interface Science. - : Elsevier BV. - 1359-0294. ; 20:4, s. 272-281
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Journal article (peer-reviewed)abstract
- Small-angle X-ray scattering (SAXS) is an indispensable tool in structural investigations of self-assembled colloidal crystals and colloidal liquid crystals. This paper reviews recent studies of the particle shape effects on the crystal structure as revealed by SAXS. Rod-like, plate-like, biaxial board-like as well as cubic-like shapes are discussed. Since relatively large, (sub)micron particles are often used in these studies, we describe the principles of the microradian X-ray diffraction technique that allows detailed characterisation of the periodic order including the determination of the intrinsic width of the Bragg peaks.
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| 5. |
- Tang, Yingying, et al.
(author)
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Highly Stable Perovskite Supercrystals via Oil-in-Oil Templating
- 2020
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 20:8, s. 5997-6004
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Journal article (peer-reviewed)abstract
- Inorganic perovskites display an enticing foreground for their wide range of optoelectronic applications. Recently, supercrystals (SCs) of inorganic perovskite nanocrystals (NCs) have been reported to possess highly ordered structure as well as novel collective optical properties, opening new opportunities for efficient films. Here, we report the large-scale assembly control of spherical, cubic, and hexagonal SCs of inorganic perovskite NCs through templating by oil-in-oil emulsions. We show that an interplay between the roundness of the cubic NCs and the tension of the confining droplet surface sets the superstructure morphology, and we exploit this interplay to design dense hyperlattices of SCs. The SC films show strongly enhanced stability for at least two months without obvious structural degradation and minor optical changes. Our results on the controlled large-scale assembly of perovskite NC superstructures provide new prospects for the bottom-up production of optoelectronic devices based on the microfluidic production of mesoscopic building blocks.
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