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Updated: Jan 21, 2026
07:23
Light-induced Patterning and Grafting for Slippery Surfaces based on Silane-coated Nanoporous Structures
Published on: November 14, 2025
317
Transparency induced in opals via nanometer thick conformal coating.
Guoliang Shang1, Kaline Pagnan Furlan2,3, Robert Zierold3
1Institute of Optical and Electronic Materials, Hamburg University of Technology, Eissendorfer Strasse 38, 21073, Hamburg, Germany. guoliang.shang@tuhh.de.
Scientific Reports
|August 8, 2019
Summary
A nanometer-thin coating on opals can eliminate their photonic band gap, making them transparent. This discovery enables new in-situ sensing applications for thin film growth and refractive index measurement.
Area of Science:
- Materials Science
- Optics
- Nanotechnology
Background:
- Opals are self-assembled 3D photonic crystals made of monodisperse spherical particles.
- Their optical properties are governed by their periodic structure and refractive index.
Purpose of the Study:
- To investigate how thin conformal coatings affect the photonic band gap of opals.
- To demonstrate a method for controlling the reflection properties of photonic crystals.
Main Methods:
- Theoretical modeling of permittivity distribution in core-shell particles.
- Atomic Layer Deposition (ALD) to apply TiO2 coatings.
- Optical characterization and simulations.
Main Results:
- A nanometer-thin TiO2 coating on polystyrene opals eliminated the first photonic band gap.
- The coated opals exhibited nearly full transparency in a previously reflective wavelength range.
- The effect was explained by a zero-value of the motif function at Bragg peak positions.
Conclusions:
- Conformal nanocoatings can drastically alter the optical properties of 3D photonic crystals.
- This phenomenon enables novel in-situ sensing applications, including real-time monitoring of ALD growth and refractive index changes.
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