Self-assembled plasmonics for angle-independent structural color displays with actively addressed black states.

Nanostructured plasmonic materials can lead to the extremely compact pixels and color filters needed for next-generation displays by interacting with light at fundamentally small length scales. However, previous demonstrations suffer from severe angle sensitivity, lack of saturated color, and absence of black/gray states and/or are impractical to integrate with actively addressed electronics. Here, we report a vivid self-assembled nanostructured system which overcomes these challenges via the multidimensional hybridization of plasmonic resonances. By exploiting the thin-film growth mechanisms of aluminum during ultrahigh vacuum physical vapor deposition, dense arrays of particles are created in near-field proximity to a mirror. The sub-10-nm gaps between adjacent particles and mirror lead to strong multidimensional coupling of localized plasmonic modes, resulting in a singular resonance with negligible angular dispersion and ∼98% absorption of incident light at a desired wavelength. The process is compatible with arbitrarily structured substrates and can produce wafer-scale, diffusive, angle-independent, and flexible plasmonic materials. We then demonstrate the unique capabilities of the strongly coupled plasmonic system via integration with an actively addressed reflective liquid crystal display with control over black states. The hybrid display is readily programmed to display images and video.

Multi-spectral frequency selective mid-infrared microbolometers.

Frequency selective detection of low energy photons is a scientific challenge using natural materials. A hypothetical surface which functions like a light funnel with very low thermal mass in order to enhance photon collection and suppress background thermal noise is the ideal solution to address both low temperature and frequency selective detection limitations of present detection systems. Here, we present a cavity-coupled quasi-three dimensional plasmonic crystal which induces impedance matching to the free space giving rise to extraordinary transmission through the sub-wavelength aperture array like a "light funnel" in coupling low energy incident photons resulting in frequency selective perfect (~100%) absorption of the incident radiation and zero back reflection. The peak wavelength of absorption of the incident light is almost independent of the angle of incidence and remains within 20% of its maximum (100%) up to θi≤45˚. This perfect absorption results from the incident light-driven localized edge "micro-plasma" currents on the lossy metallic surfaces. The wide-angle light funneling is validated with experimental measurements. Further, a super-lattice based electronic biasing circuit converts the absorbed narrow linewidth (Δλ/λ0< 0.075) photon energy inside the sub-wavelength thick film (< λ/100) to voltage output with high signal to noise ratio close to the theoretical limit. Such artificial plasmonic surfaces enable flexible scaling of light funneling response to any wavelength range by simple dimensional changes paving the path towards room temperature frequency selective low energy photon detection.

Cavity-induced hybrid plasmon excitation for perfect infrared absorption.

Photonic microcavity coupling of a subwavelength hole-disk array, a two-element metal/dielectric composite structure with enhanced extraordinary transmission, leads to 100% coupling of incident light to the cavity system and subsequent absorption. This light-funneling process arises from the temporal and spatial coupling of the broadband localized surface plasmon resonance on the coupled hole-disk array and the photonic modes of the optical cavity, which induces spectral narrowing of the perfect absorption of light. A simple nanoimprint lithography-based large-area fabrication process paves the path towards practical implementation of plasmonic cavity-based devices and sensors.

Hybrid coupling mechanism in a system supporting high order diffraction, plasmonic, and cavity resonances.

The interactions between plasmonic and photonic modes of a cavity-coupled plasmonic crystal are studied in diffraction and diffractionless regimes, which lead us to the understanding of coherent interactions between electron plasma, higher order cavity, and diffraction modes. The strong interaction between plasmonic and photonic modes is shown to enhance as well as suppress surface plasmon resonance based on cavity phase relation. Numerical and analytical approaches are developed to accurately explain the physics of the interactions evident in their characteristic dispersion graphs. Further experimental measurements confirm the theoretical predictions.

The antidepressant effect of combined extracts of Hypericum perforatum and Echium amoenum supplementation in patients with depression symptoms: A randomized clinical trial.

Objective: Echium amoenum and Hypericum perforatum dried flowers have been used for therapy of mental disorders in Iranian traditional medicine. In this study, we assessed the efficacy of the E. amoenum and H. perforatum extracts in patients with mild to moderate depression. Materials and Methods: In an 8-week double-blind, parallel-group trial, 51 patients randomly consumed 20 mg of fluoxetine or 350 mg of herbal medicine twice daily. The Hamilton Rating Scale for Depression (HAM-D) was used to assess depression severity in patients at weeks 0, 4, and 8. Results: According to the Hamilton score, there were no significant differences between the fluoxetine- and herbal medicine-treated groups after 4 and 8 weeks (p>0.05). Dry mouth was the only reported side effect which was significantly lower in the herbal group (p<0.05) in weeks 2 and 4. Conclusion: E. amoenum and H. perforatum have anti-depressant properties similar to fluoxetine and they can be used to treat depression as an alternative to fluoxetine.

Prevalence of Depression, Anxiety and Stress Among Patients Discharged from Critical Care Units.

INTRODUCTION: The widespread use of advanced technology and invasive intervention creates many psychological problems for hospitalized patients; it is especially common in critical care units. METHODS: This cross-sectional study was conducted on 310 patients hospitalized in critical care units, using a non-probability sampling method. Data were collected using depression, anxiety, and stress scale (DASS-21) one month after discharge from the hospital. Data analysis was performed using descriptive and inferential statistics. RESULTS: 181 males and 129 females with a mean age (SD) of 55.11(1.62) years were enrolled in the study. The prevalence of depression, anxiety and stress were 46.5, 53.6 and 57.8% respectively, and the depression, anxiety and stress mean (SD) scores were 16.15(1.40), 18.57(1.46), 19.69(1.48), respectively. A statistically significant association was reported between depression, anxiety and stress with an increase in age, the number of children, occupation, education, length of hospital stay, use of mechanical ventilation, type of the critical care unit, and drug abuse. CONCLUSION: The prevalence of depression, anxiety and stress in patients discharged from critical care units was high. Therefore, crucial decisions should be made to reduce depression, anxiety and stress in patients discharged from critical care units by educational strategies, identifying vulnerable patients and their preparation before invasive diagnostic-treatment procedures.

Wide Angle Dynamically Tunable Enhanced Infrared Absorption on Large-Area Nanopatterned Graphene.

Enhancing light-matter interaction by exciting Dirac plasmons on nanopatterned monolayer graphene is an efficient route to achieve high infrared absorption. Here, we designed and fabricated hexagonal planar arrays of nanoholes and nanodisks with and without optical cavity to excite Dirac plasmons on patterned graphene and investigate the role of plasmon lifetime, extinction cross-section, incident light polarization, angle of incident light, and pattern dimensions on the light-absorption spectra. By incorporating a high-k Al2O3 layer as the gate dielectric for dynamic electrostatic tuning of the Fermi level, we demonstrate peak absorptions of 60% and 90% for the nanohole and nanodisk patterns, respectively, in the atmospheric transparent 8-12 µm infrared imaging band with high spectral tunability. Finally, we theoretically and experimentally demonstrate angular dependence of both s- and p-polarized light absorption in monolayer graphene. Our results showcase the practical usability of low carrier mobility CVD-grown graphene for wide angle infrared absorption, which is suitable for next-generation optoelectronic devices such as photodetectors, optical switches, modulators, etc.

Dirac plasmon-assisted asymmetric hot carrier generation for room-temperature infrared detection.

Due to the low photon energy, detection of infrared photons is challenging at room temperature. Thermoelectric effect offers an alternative mechanism bypassing material bandgap restriction. In this article, we demonstrate an asymmetric plasmon-induced hot-carrier Seebeck photodetection scheme at room temperature that exhibits a remarkable responsivity of 2900 VW-1, detectivity of 1.1 × 109 Jones along with a fast response of ~100 ns in the technologically relevant 8-12 µm band. This is achieved by engineering the asymmetric electronic environment of the generated hot carriers on chemical vapor deposition grown large area nanopatterned monolayer graphene, which leads to a temperature gradient of 4.7 K across the device terminals for an incident power of 155 nW, thereby enhancing the photo-thermoelectric voltage by manifold compared to previous reports. The results presented outline a strategy for uncooled, tunable, and multispectral infrared detection.

Improved high-performance liquid chromatography (HPLC) method for qualitative and quantitative analysis of allantoin in Zea mays.

A high-performance liquid chromatography (HPLC) method for the qualitative and quantitative analysis of allantoin in silk and seed of Zea mays has been developed. Allantoin separation in crude extract was achieved using a C 18 column and phosphate buffer solution (pH 3.0) as a mobile phase at ambient temperature at a flow rate of 1.0 mL/min and detected at 210 nm. The results showed that the amount of allantoin in samples was between 14 and 271 mg/100 g of dry plant material. A comprehensive validation of the method including sensitivity, linearity, repeatability, and recovery was conducted. The calibration curve was linear over the range of 0.2-200 microg/mL with a correlation coefficient of r2>0.999. Limit of detection (LOD, S/N=3) and limit of quantification (LOQ) values of the allantoin were 0.05 and 0.2 microg/mL (1.0 and 4.0 ng) respectively. The relative standard deviation (RSD) value of the repeatability was reported within 1.2%. The average recovery of allantoin added to samples was 100.6% with RSD of 1.5%.

Covert infrared image encoding through imprinted plasmonic cavities.

Functional surfaces that can control light across the electromagnetic spectrum are highly desirable. Plasmonic nanostructures can assume this role by exhibiting dimension-tunable resonances that span multiple electromagnetic regimes. However, changing these structural parameters often impacts the higher-order resonances and spectral features in lower-wavelength domains. In this study, we discuss a cavity-coupled plasmonic system with resonances that are tunable across the 3-5 or 8-14 µm infrared bands while retaining near-invariant spectral properties in the visible domain. This result is accomplished by regime-dependent resonance mechanisms and their dependence on independent structural parameters. Through the identification and constraint of key parameters, we demonstrate multispectral data encoding, where images, viewable in the infrared spectral domain, appear as uniform areas of color in the visible domain-effectively hiding the information. Fabricated by large area nanoimprint lithography and compatible with flexible surfaces, the proposed system can produce multifunctional coatings for thermal management, camouflage, and anti-counterfeiting.