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Unprecedented stability of raspberry-like colloids

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Aqueous colloidal suspensions, both man-made and natural, are part of our everyday life. The applicability of colloidal suspensions, however, is highly limited by the range of conditions over which they are stable. Here, we report a novel type of highly monodisperse ‘raspberry’ colloids, which are prepared in a single-step synthesis that relies on simultaneous dispersion and emulsion polymerisation. The resulting raspberry colloids behave almost like hard spheres. In aqueous solutions such prepared raspberries show unprecedented stability against aggregation over large variations of added salt concentrations without addition of surfactants or other stabilisers. We present simple DLVO-calculations performed on raspberries and smooth colloids showing that this stability results from our raspberries’ unique morphology preventing salt-induced colloidal aggregation, which extends our understanding of colloidal stability against salting. Our calculations are supported by salting experiments using a variety of salts and differently sized colloids with varying ‘roughness’. Further, the raspberies’ stability facilitates the formation of superspheres and thin films in which the raspberry colloids self-assemble into hexagonally close-packed photonic crystals with exquisite reproducibility. Introduction The ability to disperse charged colloids in water is generally determined by the interplay between attractive van der Waals and

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Nature Communications

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Springer Nature

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Biotechnology and Biological Sciences Research Council (BB/K014617/1)
European Research Council (639088)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (701455)
YL thanks the CSC Cambridge scholarship for financial support. AC thanks D. Frenkel for discussions and acknowledges the ETN-COLLDENSE (H2020-MCSA-ITN-2014, Grant No. 642774). SV acknowledges the BBSRC David Phillips fellowship (BB/K014617/1), the European Research Council (ERC-2014-STG H2020 639088), and B. Frka-Petesic for discussions. GG thanks the Engineering and Physical Sciences Research Council (EPSRC, 1525292), VEJ the European Commission (Marie Curie Fellowship LODIS , 701455), JL the Marie Curie FP7 SASSYPOL ITN (607602), and MK EPSRC (EP/L027151/1) for financial support. EE, YL and SV thank the Winton Programme for the Physics of Sustainability.