Experimental and theoretical evidence for molecular forces driving surface segregation in photonic colloidal assemblies

Xiao, Ming; Hu, Ziying; Gartner, Thomas E.; Yang, Xiaozhou; Li, Weiyao; Jayaraman, Arthi; Gianneschi, Nathan C.; Shawkey, Matthew D.; Dhinojwala, Ali

doi:10.1126/sciadv.aax1254

Cited by 22 publications

(51 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We model color generation using FDTD on supraball structures generated from coarse‐grained molecular dynamics (CG‐MD) simulations with the CG‐MD approach previously validated by direct comparison to experiments. [ 39,48 ] The CG‐MD simulations represent the melanin and silica nanoparticles (in the case of binary mixtures) as spheres, placed under a shrinking spherical confinement to mimic an emulsion‐based assembly process [ 38,39 ] for supraball generation. We probe the desired design space by varying the interparticle interactions, particle–interface interactions, and particle size dispersity in the CG‐MD simulations to generate a diverse set of supraball structures.…”

Section: Resultsmentioning

confidence: 99%

“…[ 35–37 ] However, experimental work on spherical supraparticles (referred to as supraballs) formed via reverse emulsion‐based assembly of synthetic melanin demonstrate that the color can be tuned either by varying the spacing between the melanin particles [ 38 ] or the degree of interaction and stratification between melanin and its nonabsorbing counterpart (i.e., silica) in the case of binary mixtures. [ 39 ] These results [ 38,39 ] contradict the idea that melanin solely enhances color saturation/purity and suggest that melanin's structural arrangement can be varied to generate specific hues. These observations highlight the need to quantify the effect of melanin's broadband absorption on structural coloration and to delineate the influence of melanin's design parameters, both in one‐component system (degree of absorption, packing order, and size dispersity) and in a binary mixture with a nonabsorbing component (the extent of phase separation and stratification), on color generation.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Structural Color Production in Melanin‐Based Disordered Colloidal Nanoparticle Assemblies in Spherical Confinement

Patil

Heil

Vanthournout

et al. 2021

Advanced Optical Materials

Self Cite

View full text Add to dashboard Cite

Melanin is a ubiquitous natural pigment that exhibits broadband absorption and high refractive index. Despite its widespread use in structural color production, how the absorbing material, melanin, affects the generated color is unknown. Using a combined molecular dynamics and finite‐difference time‐domain computational approach, this paper investigates structural color generation in one‐component melanin nanoparticle‐based supraparticles (called supraballs) as well as binary mixtures of melanin and silica (nonabsorbing) nanoparticle‐based supraballs. Experimentally produced one‐component melanin and one‐component silica supraballs, with thoroughly characterized primary particle characteristics using neutron scattering, produce reflectance profiles similar to the computational analogs, confirming that the computational approach correctly simulates both absorption and multiple scattering from the self‐assembled nanoparticles. These combined approaches demonstrate that melanin's broadband absorption increases the primary reflectance peak wavelength, increases saturation, and decreases lightness factor. In addition, the dispersity of nanoparticle size more strongly influences the optical properties of supraballs than packing fraction, as evidenced by the production of a larger range of colors when size dispersity is varied versus packing fraction. For binary melanin and silica supraballs, the chemistry‐based stratification allows for more diverse color generation and finer saturation tuning than does the degree of mixing/demixing between the two chemistries.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structural Color Production in Melanin‐Based Disordered Colloidal Nanoparticle Assemblies in Spherical Confinement

Patil

Heil

Vanthournout

et al. 2021

Advanced Optical Materials

Self Cite

View full text Add to dashboard Cite

show abstract

“…They demonstrated that melanin nanoparticles can preferentially enrich at the outermost layer of supraballs when mixing with pure silica nanoparticles, leading to a unique way to control structural colors. [ 106 ] In addition, some polymer‐coated melanin nanoparticles have been used to produce structural colors, for example, hairy particles made from polyHEMA brushes grafted on the polydopamine nanoparticles. [ 107 ]…”

Section: Bioinspired Optics‐related Applicationsmentioning

confidence: 99%

Bioinspired Melanin‐Based Optically Active Materials

Xiao

Shawkey

Dhinojwala

2020

Advanced Optical Materials

Self Cite

View full text Add to dashboard Cite

the properties and functions of melanin, the synthesis of melanin-like nanoparticles, and its versatile applications in catalysis, energy, and biomedical fields. Over the last 5 years, more than 1000 papers on melanin have been published annually, based on data from the Web of Science. Quite a few of these papers have reviewed melanin's chemical structure, physiochemical properties, and biomedical applications. [4-6] However, a critical review focusing on optical functions of melanin is still lacking, despite tremendous emerging work on melaninbased photonic materials. The purpose of this review is to summarize current advances in bioinspired melanin-based optically active materials. Specifically, we will cover inherent optical properties of melanin, and then summarize melanin's optical functions in nature and its optics-related applications. 2. Melanin Structure and Optical Properties Melanin has complex chemical structures that is not yet fully understood, however, it does not hinder the exploration of their optical properties. In this section, we will first discuss classifications of melanin and then summarize unique optical properties of melanin, which will be important for both understanding its biological function in nature and synthetic applications. 2.1. Classification and Structure Conventionally, all black pigments are called melanin. Recently, d'Ischia et al. suggested that any phenolic polymers that have broadband light absorption, antioxidant, and intrinsic free radical character should be characterized as melanin. [5] Exact chemical structures of melanin remain elusive, mainly due to their insolubility in solvents, close binding with other cellular tissues, and an amorphous structure. Here, we do not elaborate on the complexities of melanin's chemical structures, [7] but rather focus on its classification. Melanin can be categorized as either natural or synthetic depending on whether it was synthesized in vivo or in vitro. Both have similar macroscopic properties, but their structures are likely quite different. Natural melanin, including eumelanin, pheomelanin, and neuromelanin, is produced from a series of enzymatic reactions starting from L-tyrosine in biological systems (Figure 1). [1] In cells (commonly melanocytes), the tyrosinase oxidizes L-tyrosine to dopaquinone (DQ). If cysteine concentration in Melanin is a widespread multifunctional biological pigment that has emerged as a promising platform for applications in coating, catalysis, energy, drug delivery, and medical therapy. Melanin is also a compelling material for photonic applications because of its favorable material characteristics, including broadband absorption, high refractive index, tunable fluorescence, and UV blocking capabilities. However, there is not yet a critical review focusing on optical functions of melanin. This review summarizes current advances in bioinspired melanin-based optically active materials, covering melanin's inherent optical properties and functions both in nature and in optics-related applications. It is ...

show abstract

“…In addition, by discussing the bi-disperse colloidal particles assembled with reverse emulsion and the evaporative assembled membranes, Xiao and coworkers demonstrated that small-sized colloidal particles tended to stay on the surface of microspheres while the synthetic melanin particles preferred the microsphere surface over silica particles. 148 That work offered a new pathway to the assembly of colloidal particles with different particle sizes and different particle chemistries. The structure of APCs can be created by controlling the coefficient of variation (CV) of colloidal particle diameters.…”

Section: Assembly Of Bi-disperse-suspensionmentioning

confidence: 99%