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Issue 44, 2017
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Colloidal inks from bumpy colloidal nanoparticles for the assembly of ultrasmooth and uniform structural colors

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Abstract

Angle-independent structural colors obtained from colloidal nanoparticles (NPs) are of interest for potential applications in displays, color printing, 3D printing, and direct writing. However, it remains challenging to prepare uniform structural colors that can be directly written from colloidal inks that not only have no coffee-ring effect, but also have ultrasmooth film thickness, which will be important for layer-by-layer stacking. Herein, we synthesize polypyrrole (PPy) black coated silica NPs that have a low coverage (∼10.7 wt%) of bumpy PPy nanogranules (10–30 nm in diameter). When the PPy@silica NPs are drop-cast on a substrate, the surface roughness of the PPy@silica NPs effectively suppresses the coffee-ring effect and center aggregation during the drying of the colloidal ink, leading to ultrasmooth surfaces with sub-micron thickness and uniform structural colors with wide viewing angles. The color can be fine-tuned by the size of silica NPs, and the presence of PPy black significantly enhances the color contrast by suppressing incoherent and multiple light scattering. Moreover, we show that the bumpy colloidal ink is very versatile: the ink can be formulated from both low and high surface tension liquids as solvents and applied to a hydrophilic or hydrophobic substrate. We demonstrate direct writing of uniformly colored lines and three different color drops stacked on top of each other.

Graphical abstract: Colloidal inks from bumpy colloidal nanoparticles for the assembly of ultrasmooth and uniform structural colors

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Publication details

The article was received on 27 Aug 2017, accepted on 07 Oct 2017 and first published on 02 Nov 2017


Article type: Paper
DOI: 10.1039/C7NR06380F
Citation: Nanoscale, 2017,9, 17357-17363
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    Colloidal inks from bumpy colloidal nanoparticles for the assembly of ultrasmooth and uniform structural colors

    D. Ge, X. Yang, Z. Chen, L. Yang, G. Wu, Y. Xia and S. Yang, Nanoscale, 2017, 9, 17357
    DOI: 10.1039/C7NR06380F

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