Z. Vértesy

Photonic nanoarchitectures occurring in butterfly scales as selective gas/vapor sensors

Photonic band gap material type nanoarchitectures occurring in the wing scales of butterflies possessing structural color were investigated as selective gas/vapor sensors. From 20 examined butterfly species all showed selective sensing when various volatile organic compounds were introduced as additives in ambient air. Four butterflies species: Chrysiridia ripheus (Geometridae), Pseudolycena marsyas, Cyanophrys remus (both Lycaenidae) and Morpho aega (Nymphalidae) were selected to demonstrate the possibilities of selective sensing offered by these natural nanoarchitectures. Each butterfly species gives characteristic response both for species, i.e., for its typical nanoarchitecture, and for the seven test vapors used. Fast response time, reproducible and concentration dependent signals are demonstrated.

Wing scale microstructures and nanostructures in butterflies − natural photonic crystals

The aim of our study was to investigate the correlation between structural colour and scale morphology in butterflies. Detailed correlations between blue colour and structure were investigated in three lycaenid subfamilies, which represent a monophylum in the butterfly family Lycaenidae (Lepidoptera): the Coppers (Lycaeninae), the Hairstreaks (Theclinae) and the Blues (Polyommatinae). Complex investigations such as spectral measurements and characterization by means of light microscopy, scanning electron microscopy and transmission electron microscopy enabled us to demonstrate that: (i) a wide array of nanostructures generate blue colours; (ii) monophyletic groups use qualitatively similar structures; and (iii) the hue of the blue colour is characteristic for the microstructure and nanostructure of the body of the scales.

Recording of transmission phase gratings in glass by ion implantation

Transmission phase gratings of grating constants of 4–12 μm have been designed and fabricated in glass via implantation of helium and nitrogen ions of energies in the 500 keV–1.6 MeV range, through photoresist masks of thickness of 3.3 μm. Multienergy implantations were applied, too. Phase profiles of the gratings were measured via interference and phase contrast microscopy and scanning electron microscopy. Quasisinusoidal profiles were obtained for the finest gratings. The highest first order diffraction efficiencies were around 20%. Dependence of the efficiencies of the gratings on the energy and dose of the implantation have been determined.

Kinetic shape formation during Gd thin film and Si(100) solid phase reaction

The initial stage of the solid phase reaction between gadolinium thin film and Si(100) substrate was investigated by x-ray diffraction and scanning electron microscopy. The interdiffusion was retarded by deliberate contamination of the Gd/Si interface to slow down the extremely rapid reaction. The surface of the reacted film showed pattern formation in separate spots. The fractal-like development of this rare-earth silicide indicates a kinetic-type process—modified by the structure of the Gd film and by the emerging stresses—rather than a previously proposed nucleation-controlled growth.

Polarized light microscopy of chemical-vapor-deposition-grown graphene on copper

Linearly polarized light microscopy (PM) revealed that graphene grown by chemical vapor deposition (CVD) on stepped Cu substrate may appear colored. The coloration is associated with the coupling of the light of 450–600 nm into propagating mode in the graphene layer when the electric vector (E→) of polarized light is parallel with the step edges and with the scattering when the E→ is normal to the step edges. PM is an inexpensive, fast, and contamination free method to efficiently visualize graphene and to map the step structure of Cu substrates used for large area CVD growth of graphene.

Fabrication of phase gratings in glass by ion implantation

Transmission phase gratings of grating constants of 4, 6, 8 and 12 micrometers have been designed and fabricated in glass samples via implantation of helium and nitrogen ions of energies in the 500 keV - 1.6 MeV range, through photoresist masks of thickness of 3.3 micrometers . Both mono- and multienergy implantations have been applied. The gratings have been studied by measuring the diffraction efficiencies. The phase profiles of the lines of the gratings have also been measured directly via interference and phase contrast microscopy and scanning electron microscopy. It was found that the profile of the implanted gratings differed significantly from the quasi rectangular profile of the mask, especially in case of the two finest gratings. The highest first order diffraction efficiencies were around 20%. The dependence of the efficiencies of the gratings on the energy and dose of the implantation have been measured.

Quasiordered photonic band gap materials of biologic origin: butterfly scales

Individual, unsupported scales of two male butterflies with dorsal blue and ventral green color were compared by microscpectrometric measurements, optical and electronic microscopy. All the scales are colored by photonic band gap type materials built of chitin (n = 1.58) and air. The different scales are characterized by different degrees of order from fully ordered single crystalline blue scales of the Cyanophrys remus butterfly through polycrystalline green scales on the ventral side of the same butterfly, to the most disordered dorsal blue scales of the Albulina metallica, where only the distance of the first neighbors is constant. The different scale nanoarchitectures and their properties are compared.

Photonic crystal type nanoarchitectures in butterfly wing scales

Photonic crystals also called Photonic Band Gap (PBG) materials — are periodic dielectric composite structures, which affect the propagation of the light. These materials are intensively studied since two decades [1, 2], because of perspectives of their applications in optical devices, textiles and colorants. The diversity of photonic crystal type nanoarchitectures found in Nature is also in the focus of researchers’ attention. Living organisms, during millennia of evolution, achieved very complex and highly optimized micro- and nanostructures not only for interaction with visible light but also for other specified functions as for example UV protection, thermal regulation or adhesion. A very remarkable attribute is that these nanostructures are produced by a limited range of materials, which offers only a moderate refractive index contrast (1/1.6). The investigation of natural nanostructures leads to the knowledge that can be applied in the design of artificial biomimetic materials with photonic properties and can reduce the engineering effort in designing these materials and costs of their fabrication.

Phase grating fabrication in glass via ion implantation

Transmission phase gratings have been designed and fabricated in glass samples via implantation of helium and nitrogen ions of energies in the 500 keV - 1.6 MeV range, through photoresist masks. Both mono- and multienergy implantations have been applied. Diffraction efficiencies of the gratings as function of the energy and dose of the ion implantation were measured.The phase profiles of the lines of the gratings have also been measured directly via interference and phase contrast-microscopy and scanning electron microscopy. Diffraction efficiencies up to 20 % have been obtained.