of the original manuscript:Hedayati, M.K.; Javaherirahim, M.; Mozooni, B.; Abdelaziz, R.; Tavassolizadeh, A.; Chakravadhanula, V.S.K.; Zaporojtchenko, V.; Strunkus, T.; Faupel, F.; Elbahri, M.: Design of a Perfect Black Absorber at Visible Frequencies Using Plasmonic MetamaterialsIn: Advanced Materials (2011) Submitted to 2 ((During the course of the last decade, trends to achieve perfect absorbers increased tremendously due to the huge interest in development of the materials for harvesting solar energy. However up to date all of the applied methods (perforated metallic films, [1][2][3] grating structured systems [4][5][6][7] , and metamaterials [8][9][10][11][12][13][14] ) are costly and suffer from a lack of flexibility.Furthermore their absorbance is limited to a narrow spectral range which makes their application for a broad range of frequencies impossible.Here we demonstrate design, fabrication and characterization of a perfect plasmonic absorber in a stack of metal and nanocomposite showing almost 100% absorbance spanning a broad range of frequencies from ultraviolet to the near infrared. The fabrication technique of our metamaterial is pretty simple, cost effective and compatible with current industrial methods of MEMS which make our proposed system an outstanding candidate for high efficiency absorber materials.Thick metallic film are known as an excellent mirror but when they are structured, the reflectance fades away because the light gets absorbed by the excitation of the conduction electrons by electromagnetic waves which is generally known as plasmon resonance.[1] This concept has been used in the last few decades to realize highly absorbing systems in diverse areas of the electromagnetic spectrum but these works were either successful only for a very narrow range of frequencies [7,[14][15][16] or the absorbance was distant from that of blackbody materials [11] .Not only the metallic film supports plasmon resonances but also the metallic nanoparticles show high absorption due to its localized particle plasmon resonance (Mie resonance) [17][18] Indeed, the resonance of these particles embedded in different matrices has been extensively studied within the last decade and it is well known that the resonance bandwidth depends on the size, shape, density and distribution of the nanoparticles. [17][18] Indeed, a highly dense nanocomposite gives rise to a very broad-band absorption due to the excitation of the localized plasmon resonance of the nanoparticles by visible light. [19] In contrast to the Submitted to 3 expectation for the absorption behavior of a metal/polymer nanocomposite, we have recently shown that nanocomposites with low filling factor in a proximity to a thin metallic film can even enhance the optical transmission of the system due to the plasmonic coupling of the film and the nanoparticles which mainly result in a reflection/scattering reduction of the system by dipole/image interaction. [20] However, rising the distance between the metallic film and the nanoparticles by adding a space...

Green nanotechnology focuses on the development of new and sustainable methods of creating nanoparticles, their localized assembly and integration into useful systems and devices in a cost-effective, simple and eco-friendly manner. Here we present our experimental findings on the use of the Leidenfrost drop as an overheated and charged green chemical reactor. Employing a droplet of aqueous solution on hot substrates, this method is capable of fabricating nanoparticles, creating nanoscale coatings on complex objects and designing porous metal in suspension and foam form, all in a levitated Leidenfrost drop. As examples of the potential applications of the Leidenfrost drop, fabrication of nanoporous black gold as a plasmonic wideband superabsorber, and synthesis of superhydrophilic and thermal resistive metal–polymer hybrid foams are demonstrated. We believe that the presented nanofabrication method may be a promising strategy towards the sustainable production of functional nanomaterials.

With increasing production and applications of nanostructured zinc oxide, e.g., for biomedical and consumer products, the question of safety is getting more and more important. Different morphologies of zinc oxide structures have been synthesized and accordingly investigated. In this study, we have particularly focused on nano-micro ZnO tetrapods (ZnO-T), because their large scale fabrication has been made possible by a newly introduced flame transport synthesis approach which will probably lead to several new applications. Moreover, ZnO-T provide a completely different morphology then classical spherical ZnO nanoparticles. To get a better understanding of parameters that affect the interactions between ZnO-T and mammalian cells, and thus their biocompatibility, we have examined the impact of cell culture conditions as well as of material properties on cytotoxicity. Our results demonstrate that the cell density of fibroblasts in culture along with their age, i.e., the number of preceding cell divisions, strongly affect the cytotoxic potency of ZnO-T. Concerning the material properties, the toxic potency of ZnO-T is found to be significantly lower than that of spherical ZnO nanoparticles. Furthermore, the morphology of the ZnO-T influenced cellular toxicity in contrast to surface charges modified by UV illumination or O2 treatment and to the material age. Finally, we have observed that direct contact between tetrapods and cells increases their toxicity compared to transwell culture models which allow only an indirect effect via released zinc ions. The results reveal several parameters that can be of importance for the assessment of ZnO-T toxicity in cell cultures and for particle development.

In this study, we devised a novel nanofibrous adsorbent made of polyethersulfone (PES) for removal of methylene blue (MB) dye pollutant from water. The polymer shows a low isoelectric point thus at elevated pHs and, being nanofibrous, can offer a huge highly hydroxylated surface area for adsorption of cationic MB molecules. As an extra challenge, to augment the adsorbent’s properties in terms of adsorption capacity in neutral and acidic conditions and thermal stability, vanadium pentoxide (V2O5) nanoparticles were added to the nanofibers. Adsorption data were analyzed according to the Freundlich adsorption model. The thermodynamic parameters verified that only at basic pH is the adsorption spontaneous and in general the process is entropy-driven and endothermic. The kinetics of the adsorption process was evaluated by the pseudo-first- and pseudo-second-order models. The latter model exhibited the highest correlation with data. In sum, the adsorbent showed a promising potential for dye removal from industrial dyeing wastewater systems, especially when envisaging their alkaline and hot conditions.

Plasmonic dipoles are famous for their strong absorptivity rather than their reflectivity. Here, the as-yet unknown specular reflection and the Brewster effect of ultrafine plasmonic dipoles, metaparticles, are introduced and exploited as the basis of new design rules for advanced applications. A configuration of "Plasmonic metaparticles on a blackbody" is demonstrated and utilized for the design of a tailored perfect-colored absorber and for visual detection of environmental dielectrics that is not readily done by extinction plasmonics. Moreover, the Plasmonic Brewster Wavelength (PBW) effect is introduced as a new platform for the naked-eye and bulk biodetection of analytes. The technique operates based on slight changes of molecular polarizability which is not detectable via conventional plasmon resonance techniques. As a specific highlight, the clinical applicability of the PBW method is demonstrated while addressing the transduction plasmonic techniques' challenge in detection of bulk refractive index changes of the healthy and diseased human serum exosomes. Finally, the sputtering-based fabrication method used here is simple, inexpensive, and scalable, and does not require the sophisticated patterning approach of lithography or precise alignment of light coupling for the biodetection.

Here, we introduce the first experimental proof of coherent oscillation and coupling of photoswitchable molecules embedded randomly in a polymeric matrix and acting cooperatively upon illumination with UV light. In particular, we demonstrate the specular reflection and Brewster phenomenon alteration of photochromic molecular dipole antennas. We successfully demonstrate the concept of Brewster wavelength, which is based on the dipolar interaction between radiating dipoles and the surrounding matrix possessing a net dipole moment, as a key tool for highly localized sensing of matrix polarity. We also introduce the concept of 'tailored molecular photonic coupling' while highlighting the role of interferences for the design of optically active media by adjusting the photonic response of the medium with the real and imaginary refractive index of photoswitchable molecules in the 'ON' state. Our results enhance our fundamental understanding of coherent dipole radiation and open a new vein of research based on glassy disordered dipolar composites that act as macroscopic antenna with cooperative action; furthermore, these results have important implications for new design rules of tailored photonics.

Here, we introduce the first smart plasmonic absorber based on metal-polymer bionanocomposites performing via conformational changes of the biological functional agent i.e. a protein. Such a progress was done through bridging the gaps between nanofluid filtration, plasmonics and bioswitching. Initially, a biofunctionalized nanofibrous membrane was developed that could filter out metal nanoparticles (<100 nm) from an aqueous stream with a high separation efficiency (97%). This approach brings about a breakthrough in applicability of the macroporous nanofibrous membranes for rejection of suspended nanosolids and extends the application area beyond Microfiltration (MF) to Ultrafiltration (UF). This operative filtration in next step leads to a novel synthesis route for plasmonic materials as formation of a smart freestanding metal-polymer bionanocomposite able to act as an omnidirectional black absorber. M. Elbahri thanks the initiative and networking fund of the Helmholtz Associations for providing the financial base of the start-up of his research group. The authors would like to acknowledge Prof. Dr. Gorb for Cryo-SEM imaging of the samples, Stefan Rehders for drawing the 3-D sketch of the membranes, Kristian Bühr for design of water flux measurement setup , Heinrich Böttcher for tensile tests, and Karen-Marita Prause for SEM measurements.

Plasmonics, as an emerging field, aims to exploit the unique optical properties of metallic nanostructures to enable routing and active manipulation of light on the nanoscale. Plasmonic heating is a phenomenon, which is recently recognized for its potential in photothermal therapy. Here we show the first proof-of-concept experiment based on plasmonic heating for selective and precise embedding of nanoparticles in a polymeric matrix. We demonstrate a unique way for in situ fabrication of nanocomposites in different forms including patterning, writing, and defect healing in a controlled manner along with crystallinity control through light irradiation.