Microspectroscopy on Thin Films of Colloidal Mixture Gradients for Data-Driven Optimization of Optical Properties

摘要

Thin films comprising mixtures of different colloids provide a simpleapproach to materials with tunable optical properties. However, the predictionof UV–vis spectra for different compositions in colloidal crystals and glassesis difficult. The degree of disorder, for example, determines whether theoptical response is dominated by incoherent scattering, coherent scattering,or Bragg diffraction. Both the volume ratio, as well as the morphology of theindividual constituents, influence the properties of the ensemble, whichnecessitates extensive screening procedures. Here, a method for expeditingsuch a screening approach by means of gradient colloidal crystals and glassesis shown. Continuous composition gradients, combined with localmicrospectroscopy, allow for the characterization of the entire compositionrange with high reproducibility, thereby reducing the experimental effort. Thisis shown for a system of spherical polymer particles with different radii. Anoptimum of the scattering efficiency in the visible wavelength range is shownclose to the order/disorder transition at the edge of the composition range.The high-throughput screening method presented here can generate largedata sets that may contribute to machine-learning-enabled optimization ofself-assembled optical materials.