Phase-change Fano resonator for active modulation of thermal emission.

Optical modulation of heat emission using spectrally selective infrared (IR) metasurface nanoantenna designs has found potential applications in various fields, including radiative cooling and thermal camouflage. While radiative cooling requires emitters to emit within atmospheric transmissive windows (mainly located at 8-14 µm), thermal camouflage structures have to operate within the non-transmissive window (5-8 µm) to hide an object from thermal imaging systems and cameras. Therefore, a passive nanoantenna structure cannot satisfy both conditions simultaneously. In this paper, we propose an adaptive nanoantenna emitter made of samarium nickelate (SmNiO3) phase change material to cover both functionalities with a single Fano resonator-based design. As the temperature rises, the thermal signature of the nanoantenna at the transmissive window is suppressed; therefore, a better camouflage performance is achieved. The dynamic tunability of switching from radiative cooling to thermal camouflage of the proposed Fano resonator-based design is quantitatively demonstrated using emissive power calculations under different conditions.

The relationship between organizational ethical climate and components of nursing error reporting in selected hospitals of Tehran University of Medical Sciences in 2020.

AIM: The aim of this study was to investigate the relationship between organizational ethical climate and components of nursing error reporting in selected hospitals of Tehran University of Medical Sciences in 2020. BACKGROUND: Error reporting is considered as a strategic indicator for error prevention. METHOD: This is a cross-sectional and correlational study that was conducted on 336 samples who had been selected by stratified random sampling method. Data were analysed by SPSS-16 software, using descriptive and inferential statistics such as Mann-Whitney U and Kruskal-Wallis tests. RESULTS: The results of this study showed a significant and direct relationship between the organizational ethical climate and components of nursing error reporting (p < .05). CONCLUSION: It is imperative for nursing managers in all management levels to remove barriers to nursing error reporting by using ethical climate strategies. IMPLICATIONS FOR NURSING MANAGEMENT: It is difficult to obtain accurate statistics on medical errors and their causes in developing countries; therefore, nursing managers should provide the necessary conditions for formal, principled, and complete reporting of nursing errors for nurses without causing fear of punishmnet.

Fano resonance in a dolomite phase-change multilayer design for dynamically tunable omnidirectional monochromatic thermal emission.

In this Letter, we unveil the unprecedented optical phonon response of CaMg(CO3)2 (dolomite) thin film in the design of a planar ultra-narrowband mid-infrared (MIR) thermal emitter. Dolomite (DLM) is a carbonate mineral composed of calcium magnesium carbonate, which can inherently accommodate highly dispersive optical phonon modes. Utilizing strong interference in the Al-DLM bilayer, a lithography-free planar thermal emitter is realized with near-unity omnidirectional emission at a specific resonance wavelength of 7.12 µm. Further incorporation of embedded vanadium dioxide (VO2) phase change material (PCM) enables the excitation of hybrid Fano resonances with dynamic spectral tunability. The findings of this study can have multiple applications, ranging from biosensing and gas sensing to thermal emission.

Adaptive visible and short-wave infrared camouflage using a dynamically tunable metasurface.

In this Letter, a dynamically tunable metasurface, which is based on antimony trisulfide, is introduced. In this structure, first a metal-insulator-metal (MIM) nanocavity is optimized in a way that, upon phase change, the visible response switches from a transmissive colored window into a reflective mirror. Later, an indium tin oxide nanoantenna is integrated on the MIM cavity to provide antireflection in the short-wave infrared (SWIR) range for SWIR mode thermal camouflage. The MIM host acts as a thermally tunable substrate to tune the SWIR response of the design.

Multi-spectral infrared camouflage through excitation of plasmon-phonon polaritons in a visible-transparent hBN-ITO nanoantenna emitter.

In an ideal platform for camouflage compatible cooling, the thermal emitter should be a spectrally selective antenna to radiate its heat buildup without being detected by thermal cameras. Moreover, to keep its visual appearance and to minimize solar induced heating, the structure should be visibly transparent. In this Letter, to achieve the visually invisible mid-infrared (MIR) camouflage-cooling feature, a metasurface design based on an indium-doped tin oxide (ITO)-hexagonal boron nitride (hBN) heterostructure is proposed. The proposed ITO-hBN nanoantenna shows spectrally selective broadband absorptions in near-infrared (NIR) and non-transmissive (MIR) windows, while it is dominantly non-emissive in other ranges. The camouflage ability of the structure in the targeted wavelengths is demonstrated using power calculations.

Generation of additive colors with near unity amplitude using a multilayer tandem Fabry-Perot cavity.

In this paper, the generation of additive red-green-blue (RGB) colors in reflectance mode with near unity amplitude is demonstrated. For this purpose, a multilayer structure made of metal-insulator-metal-semiconductor-insulator stacks is designed to achieve >0.9 reflection peaks with full-width-at-half-maximum values <0.3λpeak. The proposed design also shows near zero reflection in off-resonance spectral ranges, and this, in turn, leads to high color purity. The optimized designs are fabricated, and simulation and theoretical results are verified with characterization findings. This work demonstrates the potential of multilayer tandem cavity designs in the realization of lithography-free large-scale compatible functional optical coatings.

Building an Iron Chromophore Incorporating Prussian Blue Analogue for Photoelectrochemical Water Oxidation.

Invited for the cover of this issue is the Ferdi Karadas and Ekmel Ozbay groups at Bilkent University and co-workers. The image presents an utopic city in Iron Age, which is powered by an iron photosensitizer that bridges semiconductor buildings (TiO2 nanowires) and the catalyst (cobalt site). Read the full text of the article at 10.1002/chem.202100654.

Strong light emission from a defective hexagonal boron nitride monolayer coupled to near-touching random plasmonic nanounits.

In this Letter, we demonstrate strong light emission from defective hexagonal boron nitride (hBN) defect centers upon their coupling with disorder near-touching plasmonic units. Based on numerical simulations and characterization results, the plasmonic design at thin layer thicknesses of 20 nm can provide above 2 orders of magnitude enhancement in photoluminescence (PL) spectra. Moreover, this plasmonic platform shortens the luminescence lifetime of the emitters. The proposed design can be easily extended to other plasmonic-emitter combinations where strong light-matter interaction can be achieved using large-scale compatible routes.

Building an Iron Chromophore Incorporating Prussian Blue Analogue for Photoelectrochemical Water Oxidation.

The replacement of traditional ruthenium-based photosensitizers with low-cost and abundant iron analogs is a key step for the advancement of scalable and sustainable dye-sensitized water splitting cells. In this proof-of-concept study, a pyridinium ligand coordinated pentacyanoferrate(II) chromophore is used to construct a cyanide-based CoFe extended bulk framework, in which the iron photosensitizer units are connected to cobalt water oxidation catalytic sites through cyanide linkers. The iron-sensitized photoanode exhibits exceptional stability for at least 5 h at pH 7 and features its photosensitizing ability with an incident photon-to-current conversion capacity up to 500 nm with nanosecond scale excited state lifetime. Ultrafast transient absorption and computational studies reveal that iron and cobalt sites mutually support each other for charge separation via short bridging cyanide groups and for injection to the semiconductor in our proof-of-concept photoelectrochemical device. The reorganization of the excited states due to the mixing of electronic states of metal-based orbitals subsequently tailor the electron transfer cascade during the photoelectrochemical process. This breakthrough in chromophore-catalyst assemblies will spark interest in dye-sensitization with robust bulk systems for photoconversion applications.

Lithography-free disordered metal-insulator-metal nanoantennas for colorimetric sensing.

The colorimetric detection of bio-agent targets has attracted considerable attention in nanosensor designs. This platform provides an easy to use, real-time, and rapid sensing approach, as the color change can be easily distinguished by the naked eye. In this Letter, we propose a large scale compatible fabrication route to realize colorimetric optical nanosensors with a novel configuration. For this purpose, we design and fabricate a tightly packed disordered arrangement of Fabry-Perot based metal-insulator-metal nanoantennas with a resonance frequency at visible light wavelengths. In this design, the adsorbed bio-agent changes the effective refractive index of the cavity, and this causes a shift in the resonance wavelength. The experimental data show that the proposed design can have sensitivity values >70nm/refractive index unit. Unlike other optical sensing schemes that rely mainly on hot spot formation and field enhancement, this design has a large active area with relatively uniform patterns that make it a promising approach for low-level and reliable bio-detection.

Numerical analysis of a thermally tunable spectrally selective absorber enabled by an all-dielectric metamirror.

In this Letter, we numerically propose a temperature-tunable, ultra-narrowband one-way perfect near-infrared radiation absorber with high transmission in the longer wavelength neighboring spectral range. We obtained this functionality by using a guided-mode resonance-based grating-waveguide metamirror that is comprised of silicon, a spacer dielectric, an absorbing semiconductor, and germanium. Within the ultra-narrow bandwidth of the guided-mode resonance excited at 1.16 µm with a full width at half-maximum of 3.3 nm, we confirmed perfect absorption when light is incident from one of the two opposite directions. Excitation from the opposite direction resulted in perfect reflection. The thickness of the entire structure is limited to about one third the operating wavelength. Furthermore, due to the temperature tunability of silicon and germanium the thermo-optical sensitivity was found to be approximately 0.068 nm/K. In addition to this spectral tunability, our proposed device supports transparency windows with 80% transmission in the higher wavelength ranges. Our device is highly promising in the applications of thermo-tunable modulators and obtaining single frequency near-infrared signals from broadband sources.

Strong Light-Matter Interactions in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO4 for Photoelectrochemical Water Splitting.

Invited for this month's cover is the group of Ferdi Karadas and Ekmel Ozbay at Bilkent University. The image proposes a hybrid architecture, in which the semiconductor photoactive host is coupled to a plasmonic particle and a catalyst, to significantly substantiate the photoactivity of the cell. The Full Paper itself is available at 10.1002/cssc.202000294.

One-way and near-absolute polarization insensitive near-perfect absorption by using an all-dielectric metasurface.

In this Letter, we numerically propose the one-way perfect absorption of near-infrared radiation in a tunable spectral range with high transmission in the neighboring spectral ranges. This functionality is obtained by using a two-dimensional, guided-mode resonance-based grating-waveguide metasurface that acts as a frequency-selective reflector, a spacer dielectric, and an absorbing oxide layer. Within the bandwidth of the excited guided-mode resonance excited at 1.82 µm (with a full-width at half-maximum of 19 nm), we confirmed perfect absorption when light was incident from one of the two opposite directions, whereas in the other direction, perfect reflection was observed. The forward-to-backward absorption ratio reached as high as 60, while the thickness of the entire structure was on the order of the operating wavelength. In addition to the spectral tunability of the excited resonances and their bandwidths, our proposed device supports transparency windows with 65% transmission in the adjacent frequency bands. Our 2D grating is also verified to enable near-absolute insensitivity to the polarization state of incident light. Geometrical parameter modification also gives our design great tunability, as we also designed a device with a 300 nm absorption/reflection linewidth.

Strong Light-Matter Interactions in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO4 for Photoelectrochemical Water Splitting.

A facial and large-scale compatible fabrication route is established, affording a high-performance heterogeneous plasmonic-based photoelectrode for water oxidation that incorporates a CoFe-Prussian blue analog (PBA) structure as the water oxidation catalytic center. For this purpose, an angled deposition of gold (Au) was used to selectively coat the tips of the bismuth vanadate (BiVO4 ) nanostructures, yielding Au-capped BiVO4 (Au-BiVO4 ). The formation of multiple size/dimension Au capping islands provides strong light-matter interactions at nanoscale dimensions. These plasmonic particles not only enhance light absorption in the bulk BiVO4 (through the excitation of Fabry-Perot (FP) modes) but also contribute to photocurrent generation through the injection of sub-band-gap hot electrons. To substantiate the activity of the photoanodes, the interfacial electron dynamics are significantly improved by using a PBA water oxidation catalyst (WOC) resulting in an Au-BiVO4 /PBA assembly. At 1.23 V (vs. RHE), the photocurrent value for a bare BiVO4 photoanode was obtained as 190 µA cm-2 , whereas it was boosted to 295 µA cm-2 and 1800 µA cm-2 for Au-BiVO4 and Au-BiVO4 /PBA, respectively. Our results suggest that this simple and facial synthetic approach paves the way for plasmonic-based solar water splitting, in which a variety of common metals and semiconductors can be employed in conjunction with catalyst designs.

Bismuth plasmonics for extraordinary light absorption in deep sub-wavelength geometries.

In this Letter, we demonstrate an ultra-broadband metamaterial absorber of unrivaled bandwidth (BW) using extraordinary optical response of bismuth (Bi), which is the material selected through our novel analysis. Based on our theoretical model, we investigate the maximum metal-insulator-metal (MIM) cavity BW, achievable by any metal with known n-k data. We show that an ideal metal in such structures should have a positive real permittivity part in the near-infrared (NIR) regime. Contrary to noble and lossy metals utilized by most research groups in the field, this requirement is satisfied only by Bi, whose data greatly adhere to the ideal material properties predicted by our analysis. A Bi nanodisc-based MIM resonator with an absorption above 0.9 in an ultra-broadband range of 800 nm-2390 nm is designed, fabricated, and characterized. To the best of our knowledge, this is the broadest absorption BW reported for a MIM cavity in the NIR with its upper-to-lower absorption edge ratio exceeding best contenders by more than 150%. According to the findings in this Letter, the use of proper materials and dimensions will lead to realization of deep sub-wavelength efficient optical devices.

Unveiling the optical parameters of vanadium dioxide in the phase transition region: a hybrid modeling approach.

The phase change behavior of vanadium dioxide (VO2) has been widely explored in a variety of optical and photonic applications. Commonly, its optical parameters have been studied in two extreme regimes: hot (metallic) and cold (insulating) states. However, in the transition temperatures, VO2 acts like an inherent metamaterial with mixed metallic-insulating character. In this range, the portions of metallic and insulating inclusions are tuned by temperature, and therefore a gradual change of optical parameters can be achieved. In this paper, a universal hybrid modeling approach is developed to model VO2 in the intermediate region. For this aim, the measured reflectivity data, is analyzed and matched through the transfer matrix method (TMM) simulations where an effective medium theory (EMT) is employed. Based on the findings of this approach, not only the relative portions of inclusions are tailored but also their grain shapes are significantly altered in the transition range. Finally, the modeling approach is testified by experimental findings through dynamic device applications operating at short and mid infrared wavelengths. In addition, the hysteretic behaviors on electrical, optical, and structural parameters of the VO2 film along the heating and cooling cycles are demonstrated by the experiments and scrutinized by the simulations.

A Robust, Precious-Metal-Free Dye-Sensitized Photoanode for Water Oxidation: A Nanosecond-Long Excited-State Lifetime through a Prussian Blue Analogue.

Herein, we establish a simple synthetic strategy affording a heterogeneous, precious metal-free, dye-sensitized photoelectrode for water oxidation, which incorporates a Prussian blue (PB) structure for the sensitization of TiO2 and water oxidation catalysis. Our approach involves the use of a Fe(CN)5 bridging group not only as a cyanide precursor for the formation of a PB-type structure but also as an electron shuttle between an organic chromophore and the catalytic center. The resulting hetero-functional PB-modified TiO2 electrode demonstrates a low-cost and easy-to-construct photoanode, which exhibits favorable electron transfers with a remarkable excited state lifetime on the order of nanoseconds and an extended light absorption capacity of up to 500 nm. Our approach paves the way for a new family of precious metal-free robust dye-sensitized photoelectrodes for water oxidation, in which a variety of common organic chromophores can be employed in conjunction with CoFe PB structures.

Lithography-Free Planar Band-Pass Reflective Color Filter Using A Series Connection of Cavities.

In this article, a lithography-free multilayer based color filter is realized using a proper series connection of two cavities that shows relatively high efficiency, high color purity, and a wide view angle. The proposed structure is a metal-insulator-metal-insulator-semiconductor (MIMIS) design. To optimize the device performance, at the first step, transfer matrix method (TMM) modeling is utilized to find the right choices of materials for each layer. Simulations are carried out later on to optimize the geometries of the layers to obtain our desired colors. Finally, the optimized devices are fabricated and experimentally characterized to evaluate our modelling findings. The characterization results of the fabricated samples prove the successful formation of efficient and wide view angle color filters. Unlike previously reported FP based designs that act as a band-stop filter in reflection mode (absorbing a narrow frequency range and reflecting the rest of the spectrum), this design generates a specific color by reflecting a narrow spectral range and absorbing the rest of the spectrum. The findings of this work can be extended to other multilayer structures where an efficient connection of cavities in a tandem scheme can propose functionalities that cannot be realized with conventional FP resonators.

Publisher Correction: Near-absolute polarization insensitivity in graphene based ultra-narrowband perfect visible light absorber.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.