Spectral tuning of biotemplated ZnO photonic nanoarchitectures for photocatalytic applications

Abstract

The photocatalytic activity of a flat surface can be increased by micro- and nanostructuring the interface to increase the area of the contact surface between the photocatalyst and the solute, and moreover, to optimize charge carrier transfer. Further enhancement can be achieved by using photonic nanostructures, which exhibit photonic band gap (PBG). Structurally coloured butterfly wings offer a rich ‘library’ of PBGs in the visible spectral range which can be used as naturally tuned sample sets for biotemplating. We used conformal atomic layer deposition of ZnO on the wings of various butterfly species ( Arhopala asopia , Hypochrysops polycletus , Morpho sulkowskyi , Polyommatus icarus ) possessing structural colour extending from the near UV to the blue wavelength range, to test the effects arising from the nanostructured surfaces and from the presence of different types of PBGs. Aqueous solutions of rhodamine B were used to test the enhancement of photocatalytic activity that was found for all ZnO-coated butterfly wings. The best reaction rate of decomposing rhodamine B when illuminated with visible light was found in 15 nm ZnO coated M. sulkowskyi wing, the reflectance of which had the highest overlap with the absorption band of the dye and had the highest reflectance intensity.

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

“…Atomic layer deposition of 10, 15, and 20 nm thick ZnO layers onto the butterfly wings was carried out as it was described in [21]. A Picosun Sunale R-100 ALD reactor was used for the deposition with diethylzinc (DEZ) precursor and water vapor as oxidant.…”

“…The distance between the lamp and the catalytic surface immersed in the cuvette was 6 cm (corresponding to ~100 mW/cm 2 light power). The emission spectrum of the light source and the transmittance of the glass cuvette are found in our preliminary work, see Figures 1a and S1 within [21]. The dye degradation was followed by an Agilent Cary 60 UV-visible spectrophotometer equipped with an immersion probe (l = 1 cm) that was placed inside the solution, out of the illumination area.…”

“…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].…”

Effect of Plasmonic Au and Ag/Au Nanoparticles and Sodium Citrate on the Optical Properties of Chitin-Based Photonic Nanoarchitectures in Butterfly Wing Scales

“…This could be achieved by physical means, such as short time oxygen plasma treatment or conformal atomic layer deposition [54] of suitable chemical compounds, such as ZnO or TiO 2 , which could contribute to enhancing the photocatalytic effect too [55,56]. Recently, an enhanced photocatalytic effect was reported on butterfly wings possessing structural color and conformally coated by ZnO [57].…”

Structural, spectroscopic and morphology studies on green synthesized ZnO nanoparticles

“…The size and shape of the ZnO NPs strongly modulate the physical properties of ZnO. ZnO NPs find applications in diverse fields like solar cells [4], gas sensor [5], spintronics [6], biomedicines [7], photocatalysis [8], and luminescence [9]. A variety of physical and chemical methods (e.g., hydrothermal, solvothermal, sonochemical, sol-gel, microemulsion method, thermal decomposition, microwave irradiation, direct precipitation, laser ablation) are employed for the synthesis of ZnO NPs [10] which can alter the shape, size and characteristics and hence, control the properties of the obtained ZnO nanostructures.…”