Spectral Engineering of Hybrid Biotemplated Photonic/Photocatalytic Nanoarchitectures

Abstract

Solar radiation is a cheap and abundant energy for water remediation, hydrogen generation by water splitting, and CO2 reduction. Supported photocatalysts have to be tuned to the pollutants to be eliminated. Spectral engineering may be a handy tool to increase the efficiency or the selectivity of these. Photonic nanoarchitectures of biological origin with hierarchical organization from nanometers to centimeters are candidates for such applications. We used the blue wing surface of laboratory-reared male Polyommatus icarus butterflies in combination with atomic layer deposition (ALD) of conformal ZnO coating and octahedral Cu2O nanoparticles (NP) to explore the possibilities of engineering the optical and catalytic properties of hybrid photonic nanoarchitectures. The samples were characterized by UV-Vis spectroscopy and optical and scanning electron microscopy. Their photocatalytic performance was benchmarked by comparing the initial decomposition rates of rhodamine B. Cu2O NPs alone or on the butterfly wings, covered by a 5 nm thick layer of ZnO, showed poor performance. Butterfly wings, or ZnO coated butterfly wings with 15 nm ALD layer showed a 3 to 3.5 times enhancement as compared to bare glass. The best performance of almost 4.3 times increase was obtained for the wings conformally coated with 15 nm ZnO, deposited with Cu2O NPs, followed by conformal coating with an additional 5 nm of ZnO by ALD. This enhanced efficiency is associated with slow light effects on the red edge of the reflectance maximum of the photonic nanoarchitectures and with enhanced carrier separation through the n-type ZnO and the p-type Cu2O heterojunction. Properly chosen biologic photonic nanoarchitectures in combination with carefully selected photocatalyst(s) can significantly increase the photodegradation of pollutants in water under visible light illumination.

Hybrid Bio-Nanocomposites by Integrating Nanoscale Au in Butterfly Scales Colored by Photonic Nanoarchitectures

“…The amplitude of the reflectance maximum has dropped to about half of its value measured after the ethanol pretreatment. These tendencies are in good agreement with our earlier findings when the incorporation of Cu 2 O nanoparticles in similar pristine P. icarus wings was carried out [30]. As shown by the spectra in Figure 6b, even the incorporation in the bio-hybrid nanoarchitecture of the larger amount of Au nanoparticles either by in situ growth (Gr), or by drop-drying (Dr) still leads to the formation of a new photonic nanoarchitecture with spectral properties borrowed both form the pristine chitin photonic nanoarchitecture and the Au nanoparticles as modificatory components.…”

Breeding Polyommatus icarus Serves as a Large-Scale and Environmentally Friendly Source of Precisely Tuned Photonic Nanoarchitectures

“…As we reported recently in several papers, various butterfly wings possessing structural colour were successfully used as biotemplates with complex nanoarchitecture for the deposition of thin films with photocatalytic properties [ 49 , 50 ]. The use of butterfly wings for building hybrid photocatalytic platforms based on biological architectures with complex, hierarchic structures from the nanometre to centimetre scale opens a wide route to combine various photocatalytic nanoparticles with thin films conformally deposited by atomic layer deposition that allows spectral engineering of the optical properties of the photocatalyst in order to tune them to the specific absorption of the substances to be eliminated [ 55 , 56 ]. All over the world, numerous butterfly families possess intense colours of structural origin; for example, we recently investigated several species from the genus Arhopala that covers the spectral range from the UV to green [ 19 ].…”

Investigating the Effect of Reflectance Tuning on Photocatalytic Dye Degradation with Biotemplated ZnO Photonic Nanoarchitectures Based on Morpho Butterfly Wings

“…None of the species used in this study were subjected to any restrictions. The flattest and most homogeneous 15 × 15 mm square samples were cut from butterfly wings and fixed on 20 × 20 mm glass substrates using heated polylactic acid (PLA) adhesive and 20 × 20 mm polytetrafluoroethylene (PTFE) frames with a 15 × 15 mm opening, similarly as the schematic image of Figure 1 in [22].…”

“…Therefore, by modifying the material properties or ratio of the constituents, the spectral characteristics of reflected light can be changed [19]; both additive and subtractive modification of butterfly wing scale nanostructures result in a color shift of the wings when atomic layer deposition of thin films or oxygen plasma etching is applied, respectively [20]. If a suitable semiconductor thin film coating is deposited onto the photonic nanoarchitecture in butterfly wing scales, they can be used even in heterogeneous photocatalysis for the controlled decomposition of substances dissolved in water by sunlight [9,19,21,22].…”