Disorder explains dual‐band reflection spectrum in spherical colloidal photonic supraparticle assemblies. Issue 12 (31st October 2021)

• Record Type: Journal Article
• Authors: Kuhn, Eduard; Röhlig, David; Sowade, Enrico; Rittrich, Dirk; Willert, Andreas; Schulz, Stefan E.; Baumann, Reinhard R.; Thränhardt, Angela; Blaudeck, Thomas
• Is Part Of: Nano select. Volume 2:Issue 12(2021)
• Page Start: 2461
• Page End: 2472
• Publication Date: 2021-10-31
• Subjects: colloids -- optical properties -- photonic crystals -- reflection spectroscopy -- self‐assembly; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.5
• DOI: 10.1002/nano.202100263
• Languages: English
• ISSNs: 2688-4011

Abstract

Abstract: Spherical colloidal photonic supraparticle systems or assemblies (SCAs) are investigated as a model system for confined optical and photonic components. Simulations of the reflection spectrum to calculate their photonic and optical properties for different parameter constellations are compared with experimental studies by microreflectance spectroscopy ( μ RS) on SCAs fabricated by inkjet in‐flight deposition, proving the existence of a dual‐band reflection spectrum originating from the supraparticle system. Finite‐difference time‐domain (FDTD) calculations are employed to verify these findings as a function of structural parameters. Both, theory and experiment, show a double reflection peak for the SCAs and agree well in the variation of position and shape, scaling clearly with the packing density of the SCAs. Reducing this parameter from 0.6 to 0.3, the higher‐wavelength reflection maximum decreases in intensity and increases in width but keeps its spectral position. The lower‐wavelength reflection maximum decreases in intensity, increases in width and shows a red shift. The results clearly indicate that aspects of disorder decisively contribute to the particular spectral photonic properties of the supraparticle system which are usually related to order in photonic crystals. This finding can stipulate novel, tailor‐made nanostructured optical components such as low‐dimensional micro resonators and waveguides. Abstract : Assemblies from colloidal nanoparticles are known for their interesting photonic applications such as structural colors and optical waveguides. However, both bionic inspiration and manufacturing tolerances urge to clarify the roles of order versus disorder on the desired optical properties. This research article presents a complete finite‐difference time‐domain (FDTD) simulation of the microreflectance spectra of spherical colloidal nanoassemblies (SCAs) deposited by an in‐flight inkjet self‐assembly technique. It concludes that even a disordered morphology of the SCAs can explain a dual‐band reflection spectrum which are usually assigned to a crystalline structure.