Photonic Nanoarchitectures Research Articles

Pretreated Butterfly Wings for Tuning the Selective Vapor Sensing.

Photonic nanoarchitectures occurring in the scales of Blue butterflies are responsible for their vivid blue wing coloration. These nanoarchitectures are quasi-ordered nanocomposites which are constituted from a chitin matrix with embedded air holes. Therefore, they can act as chemically selective sensors due to their color changes when mixing volatile vapors in the surrounding atmosphere which condensate into the nanoarchitecture through capillary condensation. Using a home-built vapor-mixing setup, the spectral changes caused by the different air + vapor mixtures were efficiently characterized. It was found that the spectral shift is vapor-specific and proportional with the vapor concentration. We showed that the conformal modification of the scale surface by atomic layer deposition and by ethanol pretreatment can significantly alter the optical response and chemical selectivity, which points the way to the efficient production of sensor arrays based on the knowledge obtained through the investigation of modified butterfly wings.

Substance specific chemical sensing with pristine and modified photonic nanoarchitectures occurring in blue butterfly wing scales.

Butterfly wing scales containing photonic nanoarchitectures act as chemically selective sensors due to their color change when mixing vapors in the atmosphere. Based on butterfly vision, we built a model for efficient characterization of the spectral changes in different atmospheres. The spectral shift is vapor specific and proportional with the vapor concentration. Results were compared to standard principal component analysis. The modification of the chemical properties of the scale surface by the deposition of 5 nm of Al(2)O(3) significantly alters the character of the optical response. This is proof of the possibility to purposefully tune the selectivity of such sensors.

Plasmonic enhancement in BiVO4 photonic crystals for efficient water splitting.

Photo-electrochemical water splitting is a very promising and environmentally friendly route for the conversion of solar energy into hydrogen. However, the solar-to-H2 conversion efficiency is still very low due to rapid bulk recombination of charge carriers. Here, a photonic nano-architecture is developed to improve charge carrier generation and separation by manipulating and confining light absorption in a visible-light-active photoanode constructed from BiVO4 photonic crystal and plasmonic nanostructures. Synergistic effects of photonic crystal stop bands and plasmonic absorption are observed to operate in this photonic nanostructure. Within the scaffold of an inverse opal photonic crystal, the surface plasmon resonance is significantly enhanced by the photonic Bragg resonance. Nanophotonic photoanodes show AM 1.5 photocurrent densities of 3.1 ± 0.1 mA cm−2 at 1.23 V versus RHE, which is among the highest for oxide-based photoanodes and over 4 times higher than the unstructured planar photoanode.

DNA-programmed self-assembly of photonic nanoarchitectures

Rational design and self-assembly of photonic nanoarchitectures with well-defined structures and geometries allows precisely manipulating light on the nanoscale, which has been the focus of nanophotonics in recent decades. DNA self-assembly is a powerful strategy in constructing desired photonic nanoarchitectures owing to the unique structural features of DNA, such as programmable sequence, predictable structure and precise molecule length (0.34 nm bp−1). The high addressability of DNA nanoscaffolds enables fine control over the locations of the photonic building blocks and thus the structure and geometry of the assembled photonic nanoarchitectures, which facilitates the quantitative study of the interactions among these photonic building blocks that are precisely organized on the DNA nanoscaffolds. This review summarizes the recent achievements in DNA-programmed self-assembly of photonic nanoarchitectures, where metallic nanocrystals and semiconductor quantum dots act as building blocks and are assembled into homo- and hetero-nanoarchitectures from one to two and three dimensions. In this review, we highlight the recent achievements in the DNA-programmed self-assembly of homo- and/or hetero-photonic nanoarchitectures comprising gold nanoparticles, gold nanorods and quantum dots in one, two and three dimensions, and overview their optical properties and potential photonic functionalities. The assembly of photonic nanodevices with the help of DNA molecules offers an unprecedented level of control over optical properties on the nanoscale. Xiang Lan and Qiangbin Wang from the Suzhou Institute of Nano-Tech and Nano-Bionics in China review progress made toward the creation of one-, two- and three-dimensional assemblies of metal nanoparticles or semiconductor quantum dots using DNA molecules. The size and shape - as well as the environment - of such nanoparticles significantly influence their optical properties. The precision that can be obtained in the construction of DNA assemblies, unmatched by conventional lithography techniques, is therefore crucial for the realization of more complex device architectures that can be used, for example, to guide light. Nevertheless, remaining challenges must be overcome to achieve controlled assembly of architectures containing mixed particles or more complex structures, which require an asymmetric surface patterning of the nanoparticles with DNA.

Temperature and saturation dependence in the vapor sensing of butterfly wing scales

The sensing of gasses/vapors in the ambient air is the focus of attention due to the need to monitor our everyday environment. Photonic crystals are sensing materials of the future because of their strong light-manipulating properties. Natural photonic structures are well-suited materials for testing detection principles because they are significantly cheaper than artificial photonic structures and are available in larger sizes. Additionally, natural photonic structures may provide new ideas for developing novel artificial photonic nanoarchitectures with improved properties. In the present paper, we discuss the effects arising from the sensor temperature and the vapor concentration in air during measurements with a photonic crystal-type optical gas sensor. Our results shed light on the sources of discrepancy between simulated and experimental sensing behaviors of photonic crystal-type structures. Through capillary condensation, the vapors will condensate to a liquid state inside the nanocavities. Due to the temperature and radius of curvature dependence of capillary condensation, the measured signals are affected by the sensor temperature as well as by the presence of a nanocavity size distribution. The sensing materials used are natural photonic nanoarchitectures present in the wing scales of blue butterflies.

Photonic Crystals for Chemical Sensing and Biosensing

This Review covers photonic crystals (PhCs) and their use for sensing mainly chemical and biochemical parameters, with a particular focus on the materials applied. Specific sections are devoted to a) a lead-in into natural and synthetic photonic nanoarchitectures, b) the various kinds of structures of PhCs, c) reflection and diffraction in PhCs, d) aspects of sensing based on mechanical, thermal, optical, electrical, magnetic, and purely chemical stimuli, e) aspects of biosensing based on biomolecules incorporated into PhCs, and f) current trends and limitations of such sensors.

Vapor Sensing of Pristine and ALD Modified Butterfly Wings

Butterfly wing scales containing three-dimensional photonic nanoarchitectures exhibit measurable color change when adding to the ambient air different types of volatile vapors. This allows their use as optical vapor sensors. The sensing mechanism is based on the capillary condensation of the vapors into the nanoarchitecture. Using principal component analysis we show that the spectral shift is vapor specific and proportional with the vapor concentration both in the case of pristine and ALD modified butterfly wings.

Color Changes Upon Cooling of Lepidoptera Scales Containing Photonic Nanoarchitectures, and a Method for Identifying the Changes

The effects produced by the condensation of water vapor from the environment in the various intricate nanoarchitectures occurring in the wing scales of several Lepidoptera species were investigated by controlled cooling (from 23° C, room temperature to -5 to -10° C) combined with in situ measurements of changes in the reflectance spectra. It was determined that all photonic nanoarchitectures giving a reflectance maximum in the visible range and having an open nanostructure exhibited alteration of the position of the reflectance maximum associated with the photonic nanoarchitectures. The photonic nanoarchitectures with a closed structure exhibited little to no alteration in color. Similarly, control specimens colored by pigments did not exhibit a color change under the same conditions. Hence, this method can be used to identify species with open photonic nanoarchitectures in their scales. For certain species, an almost complete disappearance of the reflectance maximum was found. All specimens recovered their original colors following warming and drying. Cooling experiments using thin copper wires demonstrated that color alterations could be limited to a width of a millimeter or less. Dried museum specimens did not exhibit color changes when cooled in the absence of a heat sink due to the low heat capacity of the wings.

Booming biophotonics and the recent impact factor 2012

Over the last years biophotonics has developed into a major discipline within photonics and the optical sciences. With this issue, Laser & Photonics Reviews sets a focus on “Biophotonics Techniques & Applications” informing about recent developments and topics within this field. The content is split in two sections. Section one is devoted to the biophotonics topic (pp. 605–796), whereas the second part consists of regular content of mixed topics (pp. 797–L65). Laser & Photonics Reviews publishes biophotonic content on a regular basis, for example there has been a special issue “Light and Life: Biophotonics Special” in 2011 1. In that past issue you will find highly cited articles from P. U. Jepsen et al. about terahertz spectroscopy and imaging 2, C. Maurer et al. about spatial light modulators in optical microscopy 3, P.J. Campagnola et al. about second harmonic generation microscopy 4, L. P. Biro et al. about photonic nanoarchitectures in butterflies and beetles 5 and many more. In January 2009 the journal published a special section “Biophotonics for Biology” 6. Our regular issues contain plenty of biophotonics content, too, as evidenced by D.A. Schmidt et al. reporting about far- and near-field microscopy 7, Wang et al. reviewing apodization and near field diffraction structures 8, R. Brunner et al. writing about biomimetic subwavelength structures 9, and D.D. Arslanov et al. discussing OPO based IR spectroscopy for molecular gas sensing 10. Now let's have a look at the recent Thomson Reuters impact factors (IF) 2012 released in June this year. Laser & Photonics Reviews received an IF of 7.976 – thus closely scratching the 8. This increase is a very positive sign which nicely confirms our journal's position among the very best optics journals. Since its beginning Laser & Photonics Reviews has seen a nearly constant rise in impact factor values (see figure) – except for the year 2010 where it got an even better IF. According to Thomson Reuters Journal Citation Report® the journal ranks second in the field of optics and is among the top 10 in the fields of applied and condensed matter physics. This is remarkable and puts us in an excellent position to develop this journal further towards better and more content. Last year the journal opened up for original papers and letter articles (see Editorial in 11). We now have a ratio of about 45% review articles, 35% original papers and 20% letters. Since the beginning of 2013 we see an increase in article submissions of high quality and look forward to even more manuscripts coming in. As outlined in [11] we apply strict selection rules to keep the journal's level of quality high. Still, the number of accepted manuscripts has increased, and as we aim for an organic growth, i.e. only a modest increase in published articles, we will have to increase our quality standards even further. While this will inevitably result in a higher rejection rate, it should not dissuade anyone to submit his or her article to Laser & Photonics Reviews. We believe that a successful journal in terms of impact and quality is of great value to its authors and hence worth the effort. Now, stay with us, enjoy this issue and have a pleasant reading. Best regards, Guido W. Fuchs (Editor-in-Chief)

Optical Properties of Bioinspired Disordered Photonic Nanoarchitectures

Bioinspired 1+2D nanoarchitectures inspired by the quasi-ordered structures occurring in photonic nano-architectures of biological origin, like for example butterfly scales, were produced by depositing a layer of SiO2 nanospheres (156 nm and 292 nm in diameter) on Si wafers, over which a regular multilayer composed from three alternating layers of SiO2 and TiO2 was deposited by physical vapor deposition. Flat multilayers were deposited in the same run on oxidized Si (324 nm SiO2 thickness) for comparison. Different types of disorder (in plane and out of plane) were purposefully allowed in the 1+2D nanoarchitectures. The positions of the specular reflection maxima for the flat multilayer and for the two different bioinspired nanoarchitectures were found to be similar. Additionally to this, the bioinspired nanoarchitectures exhibited angle independent diffuse reflection too, which was absent in the flat multilayer. Different model calculations were made to explain the specular and diffuse optical properties...

Color Changes upon Cooling of Lepidoptera Scales Containing Photonic Nanoarchitectures

Photonic crystal type nanoarchitectures have an important advantage over conventional displays: they do not fade under solar illumination; on the contrary, more intense illumination generates more intense color. We present a simple method based on cooling in ambient air - to observe the color change of several butterfly wings colored by various photonic nanoarchitectures. The color change can be attributed to the condensation of atmospheric humidity in the nanocavities of the photonic nanoarchitecture. The effects were investigated by controlled cooling combined with the in-situ measurement of the changes in the reflectivity spectra. For certain species the reflectivity maximum (color) has almost completely disappeared. A correlation was also found between the openness of the nanostructure and the time of the color change. Cooling experiments, using thin copper wires showed that color alteration could be limited to millimeters; this may offer a possible alternative for display technology.

Color change of Blue butterfly wing scales in an air – Vapor ambient

Photonic crystals are periodic dielectric nanocomposites, which have photonic band gaps that forbid the propagation of light within certain frequency ranges. The optical response of such nanoarchitectures on chemical changes in the environment is determined by the spectral change of the reflected light, and depends on the composition of the ambient atmosphere and on the nanostructure characteristics. We carried out reflectance measurements on closely related Blue lycaenid butterfly males possessing so-called “pepper-pot” type photonic nanoarchitecture in their scales covering their dorsal wing surfaces. Experiments were carried out changing the concentration and nature of test vapors while monitoring the spectral variations in time. All the tests were done with the sample temperature set at, and below the room temperature. The spectral changes were found to be linear with the increasing of concentration and the signal amplitude is higher at lower temperatures. The mechanism of reflectance spectra modification is based on capillary condensation of the vapors penetrating in the nanostructure. These structures of natural origin may serve as cheap, environmentally free and biodegradable sensor elements. The study of these nanoarchitectures of biologic origin could be the source of various new bioinspired systems.

The well-tuned blues: the role of structural colours as optical signals in the species recognition of a local butterfly fauna (Lepidoptera: Lycaenidae: Polyommatinae).

The photonic nanoarchitectures responsible for the blue colour of the males of nine polyommatine butterfly species living in the same site were investigated structurally by electron microscopy and spectrally by reflectance spectroscopy. Optical characterization was carried out on 110 exemplars. The structural data extracted by dedicated software and the spectral data extracted by standard software were inputted into an artificial neural network software to test the specificity of the structural and optical characteristics. It was found that both the structural and the spectral data allow species identification with an accuracy better than 90 per cent. The reflectance data were further analysed using a colour representation diagram built in a manner analogous to that of the human Commission Internationale de l'Eclairage diagram, but the additional blue visual pigment of lycaenid butterflies was taken into account. It was found that this butterfly-specific colour representation diagram yielded a much clearer distinction of the position of the investigated species compared with previous calculations using the human colour space. The specific colours of the investigated species were correlated with the 285 flight-period data points extracted from museum collections. The species with somewhat similar colours fly in distinct periods of the year such that the blue colours are well tuned for safe mate/competitor recognition. This allows for the creation of an effective pre-zygotic isolation mechanism for closely related synchronic and syntopic species.

Bioinspired photonic nanoarchitectures from graphitic thin films

Bioinspired, regular, rectangular (with periodicities of 600 nm and 700 nm), and random (with average characteristic distances of 600 nm and 750 nm) two dimensional (2D) photonic nanoarchitectures of 60 nm thickness were produced in graphite by Focused Ion Beam (FIB) nanomachining and subsequent controlled oxidation. The color of the nanoarchitectures was modified by the conformal deposition of 90 nm Al 2O 3. The regular patterns generate iridescent colors, while the random ones exhibit a remarkably constant color with the variation of the illumination and viewing conditions.

Color based discrimination of chitin-air nanocomposites in butterfly scales and their role in conspecific recognition.

The self-assembled photonic nanoarchitectures occurring in the wing scales of the blue colored males of nine Lycaenid butterfly species, living in the same habitat, were investigated by reflectance measurements followed by automated data processing. The spectral signatures of the nine species analyzed using an artificial neural network software show that despite the fact that all possess similar "pepper pot" type structure, the spectral signatures exhibit enough characteristic differences to allow the unambiguous identification of conspecific individuals. By cross-correlating the position of the individuals of each species in the CIE chromaticity diagram with their flying period it was possible to show that relatively similarly looking, closely related species fly in distinct periods. The spectral identification method may prove useful in the investigation of museum exemplars which cannot be harmed. As the self-assembled, quasiordered, "pepper pot" type photonic nanoarchitectures of various colors seem to pose milder constraints on the production process as compared with perfect photonic crystals, such nanoarchitectures may find practical applications in a wide range from the textile industry to environmentally friendly colorants.

Photonic nanoarchitectures in butterflies and beetles: valuable sources for bioinspiration

AbstractNature began developing photonic nanoarchitectures millions of years before humankind. Often, in the living world, color is a communication channel that may influence the chance of the individual surviving as well as the chance to reproduce. Therefore, natural color‐generating structures are highly optimized by many millennia of evolution. In this review, a survey is presented of the development of natural photonic crystal‐type nanoarchitectures occurring in butterflies and beetles from the standpoint of physics and materials science, covering the past ten years. One‐, two‐, and three‐dimensional structures are reviewed, emphasizing the role that disorder, or irregularity, may play in natural nanoarchitectures to achieve certain visual effects. The characterization, modeling methods, and rapidly growing number of bioinspired or biomimetic applications are discussed.

Bioinspired artificial photonic nanoarchitecture using the elytron of the beetleTrigonophorus rothschildi variansas a ‘blueprint’

An unusual, intercalated photonic nanoarchitecture was discovered in the elytra of Taiwanese Trigonophorus rothschildi varians beetles. It consists of a multilayer structure intercalated with a random distribution of cylindrical holes normal to the plane of the multilayer. The nanoarchitectures were characterized structurally by scanning electron microscopy and optically by normal incidence, integrated and goniometric reflectance measurements. They exhibit an unsaturated specular and saturated non-specular component of the reflected light. Bioinspired, artificial nanoarchitectures of similar structure and with similar properties were realized by drilling holes of submicron size in a multilayer structure, showing that such photonic nanoarchitectures of biological origin may constitute valuable blueprints for artificial photonic materials.

Photonic nanoarchitectures of biologic origin in butterflies and beetles

Abstract Photonic nanoarchitectures occurring in butterflies and beetles, which produce structural color in the visible range of the electromagnetic spectrum by the selective reflection of light, are investigated under the aspect of being used as possible “blueprints” for artificial, bioinspired nanoarchitectures. The role of order and disorder and of regularity/irregularity in photonic nanoarchitectures of biologic origin is discussed. Three recent case studies are briefly reviewed for butterflies (Albulina metallica, Cyanophrys remus, Troides magellanus) and three for beetles (Hoeplia coerulea, Chrysochroa vittata, Charidotella egregia). The practical realization of bioinspired artificial structures is discussed for the A. metallica butterfly and for the C. vittata beetle.

Living Photonic Crystals: Nanostructure of the Scales ofCyanophrys RemusButterfly

The complex photonic crystal type nanoarchitectures found in the wing scales of the male butterfly Cyanophrys remus were investigated structurally by electron microscopy and optically by reflectance spectroscopy. Both the vivid metallic blue of the dorsal scales and the matt, pea-green coloration of the ventral scales are attributed to photonic crystal type structures composed of chitin and air. The dorsal scales are single crystalline, while the ventral ones contain a large number of randomly oriented micron size single crystalline grains of face centered cubic inverse opal. The remarkable complexity and efficiency of biologic photonic crystals may provide clues in designing artificial structures with similar parameters.