Optimization Design of a Multi-slot Nanoantenna Based on Genetic Algorithm for Energy Harvesting

A new genetic algorithm (GA)-based multi-slot nanoantenna is proposed for energy harvesting, which consists of two element nanoantennas with rectangular shape and with double bowtie double ring (DBDR) slot. The DBDR slot structure can enhance the electric field to increase the absorptivity of nanoantennas; however, the larger parameter space of multi-slot is more hardly controlled. Therefore, we use GA to optimize the parameters of the DBDR slot nanoantenna and the Finite-Difference Time-Domain method to calculate the absorptivity. It is found that absorptivity of the optimized nanoantenna is over 77% in 400–1800 nm waveband. We attribute the better absorbing property of the nanoantenna to the synergistic effect of the localized surface plasmon resonance enhancement and coupling between slots.

     

Functional characteristics of a fruticose type of lichen, Stereocaulon foliolosum Nyl. in response to light and water stress

Stereocaulon foliolosum a fruticose type of lichen under its natural habitat is subjected to low temperature, high light conditions and frequent moisture stress due its rocky substratum. To understand as to how this lichen copes up with these stresses, we studied the reflectance properties, light utilization capacity and the desiccation tolerance under laboratory conditions. S. foliolosum showed light saturation point for photosynthesis at 390 μmol CO₂ m^?2 s^?1 and the light compensation point for photosynthesis at 64 μmol CO₂ m^?2 s^?1. Our experiments show that S. foliolosum has a low absorptivity (30–35 %) towards the incident light. The maximum rates of net photosynthesis and apparent electron transport observed were 1.9 μmol CO₂ m^?2 s^?1 and 45 μmol e^? m^?2 s^?1, respectively. The lichen recovers immediately after photoinhibition under low light conditions. S. foliolosum on subjecting to desiccation results in the decrease of light absorptivity and the reflectance properties associated with water status of the thalli show a change. During desiccation, a simultaneous decrease in photosynthesis, dark respiration and quenching in the fluorescence properties was observed. However, all the observed changes show a rapid recovery on rewetting the lichen. Our study shows that desiccation does not have a severe or long-term impact on S. foliolosum and the lichen is also well adapted to confront high light intensities.     

Individual Split Au Square Nanorings for Surface-Enhanced Raman and Hyper-Raman Scattering

In this paper, individual split Au square nanorings were numerically proposed as novel substrates for surface-enhanced Raman and hyper-Raman scattering (SERS and SEHRS) simultaneously. The peak wavelengths of their localized surface plasmon resonance (LSPR) fall in the near-infrared and visible light regions, respectively, which are able to be finely tuned to match well with the wavelengths of the incident laser and hyper-Raman scattered light beams. Their SEHRS and SERS performances along with electromagnetic (EM) field distributions are numerically investigated by finite element method. With the enhancement of near electric-fields generated by LSPRs, the maximum SEHRS and SERS enhancement factors are demonstrated to reach 1.22?×?10¹² and 10⁸, respectively. Meanwhile, the corresponding SERS-based refractive index (RI) sensitivity factor reaches as high as 258 nm/RIU and 893 nm/RIU, at visible and near-infrared wavelengths, respectively. The proposed structure holds great promise both for developing SEHRS- and SERS-based RI sensing substrates, which shows strong potential applications in nanosensing and enhanced Raman scattering.

     

Importance of the green color,absorption gradient,and spectral absorption of chloroplasts for the radiative energy balance of leaves

Terrestrial green plants absorb photosynthetically active radiation (PAR; 400–700 nm) but do not absorb photons evenly across the PAR waveband. The spectral absorbance of photosystems and chloroplasts is lowest for green light, which occurs within the highest irradiance waveband of direct solar radiation. We demonstrate a close relationship between this phenomenon and the safe and efficient utilization of direct solar radiation in simple biophysiological models. The effects of spectral absorptance on the photon and irradiance absorption processes are evaluated using the spectra of direct and diffuse solar radiation. The radiation absorption of a leaf arises as a consequence of the absorption of chloroplasts. The photon absorption of chloroplasts is strongly dependent on the distribution of pigment concentrations and their absorbance spectra. While chloroplast movements in response to light are important mechanisms controlling PAR absorption, they are not effective for green light because chloroplasts have the lowest spectral absorptance in the waveband. With the development of palisade tissue, the incident photons per total palisade cell surface area and the absorbed photons per chloroplast decrease. The spectral absorbance of carotenoids is effective in eliminating shortwave PAR (<520 nm), which contains much of the surplus energy that is not used for photosynthesis and is dissipated as heat. The PAR absorptance of a whole leaf shows no substantial difference based on the spectra of direct or diffuse solar radiation. However, most of the near infrared radiation is unabsorbed and heat stress is greatly reduced. The incident solar radiation is too strong to be utilized for photosynthesis under the current CO₂ concentration in the terrestrial environment. Therefore, the photon absorption of a whole leaf is efficiently regulated by photosynthetic pigments with low spectral absorptance in the highest irradiance waveband and through a combination of pigment density distribution and leaf anatomical structures.     

Three-Step Photoconversion of Only Three Subunits of the Water-Soluble Chlorophyll-Binding Protein Tetramer from Chenopodium album

Water-soluble chlorophyll (Chl)-binding proteins (WSCPs) have been found in various plants. WSCPs are categorized into two classes based on their photoconvertibility: Class I (photoconvertible) and Class II (non-photoconvertible). Based on their absorption peaks, which occur in the red wavelengths, the pre- and post-photoconverted forms of Chenopodium album WSCP (CaWSCP) are called CP668 and CP742, respectively. Although various biochemical and biophysical properties of CaWSCP have already been characterized, questions remain regarding the structural dynamics of the photoconversion from CP668 to CP742, and the relationship between the photoconversion activity and incident light wavelength. To address how the wavelength of incident light affects the photoconversion, we performed time-course analyses of CaWSCP photoconversion by using light-emitting diodes that emit either white light, or at the discrete wavelengths 670, 645, 525, 470, or 430 nm. The most efficient photoconversion was observed under irradiation at 430 nm. Less efficient photoconversion was observed under irradiation with 670, 645, 470, or 525 nm light, in that order. The relationship between photoconversion activity and wavelength corresponded with the absorption peak intensities of Chls in the CaWSCP complex. The observed time dependence of the A₇₄₂/A₆₆₈ ratio during photoconversion of the CaWSCP complex indicated that the photoconversion from CP668 to CP742 occurs in a three-step reaction, and that only three subunits in the complex could be photoconverted.     

A Novel Diamond Ring Fiber-Based Surface Plasmon Resonance Sensor

We propose a highly sensitive novel diamond ring fiber (DRF)-based surface plasmon resonance (SPR) sensor for refractive index sensing. Chemically active plasmonic material (gold) layer is coated inside the large cavity of DRF, and the analyte is infiltrated directly through the fiber instead of selective infiltration. The light guiding properties and sensing performances are numerically investigated using the finite element method (FEM). The proposed sensor shows a maximum wavelength and amplitude interrogation sensitivity of 6000 nm/RIU and 508 RIU^?1, respectively, over the refractive index range of 1.33–1.39. Additionally, it also shows a sensor resolution of 1.67 × 10^?5 and 1.97 × 10^?5 RIU by following the wavelength and amplitude interrogation methods, respectively. The proposed diamond ring fiber has been fabricated following the standard stack-and-draw method to show the feasibility of the proposed sensor. Due to fabrication feasibility and promising results, the proposed DRF SPR sensor can be an effective tool in biochemical and biological analyte detection.     

Effects of various LED light spectra on circadian rhythm during starvation in the olive flounder (Paralichthys olivaceus)

In aquaculture, feeding is essential for the maintenance of metabolic processes and homoeostasis of fish. However, fasting acts as a stressor. In this study, we investigated the effect of circadian rhythm under various LED wavelengths [blue (460 nm), green (520 nm) and red (630 nm)] and two light intensities (0.3 and 0.6 W m^?2) over a 9-days period in the olive flounder (Paralichthys olivaceus). We analysed clock genes like period 2 (Per 2) and cryptochrome 1 (Cry 1), and serotonin and arylalkylamine-N-acetyltransferase 2 (AANAT 2), which control circadian rhythms. Per 2, Cry 1, serotonin and AANAT 2 were significantly decreased during the starvation period compared to the normal feeding group. Nevertheless, their levels increased in the groups exposed to green- and blue LED light during the experimental period. These results confirmed that green and blue wavelengths are effective in maintaining the circadian rhythm in olive flounder.     

Spectrally Tunable Optical Transmission of Titanium Nitride Split Ring Resonators

In this paper, the optical properties of titanium nitride split ring resonators as an intermetallic metamaterial nanostructure were studied. Our simulation shows the presence of plasmon and LC resonances in the transmission spectrum of a cell consists of four u-shape split ring resonators. The effect of different parameters of resonator such as size, periodic constant, and the material between arms in addition to the polarization of incident beam was examined on the resonance behavior of the system. Also, the optical properties of a cell consist of four complementary split ring resonators within titanium nitride thin film were investigated. An excited mode was observed at λ = 840 nm that was attributed to the plasmon resonance. Changing the arrangement and configuration of the system from C _1v to C _2v symmetry led to the presence of the LC mode beside the plasmon mode in the transmission spectrum. Also, we explored a connection between the complementary split ring resonators and orderly perforated surface plasmon systems. It was determined that a transition occurred from resonator-type to surface plasmon behavior by increasing the size of resonator above 170 nm.     

Dual-Band Infrared Perfect Absorber Based on a Ag-Dielectric-Ag Multilayer Films with Nanoring Grooves Arrays

In this paper, we demonstrate a dual-band metamaterial perfect absorber based on a Ag-dielectric-Ag multilayer nanostructure. The structure of top metal film covers nanoring grooves array. A dielectric layer has a function of confining electromagnetic fields. Theoretical analysis shows that two absorption peaks (1059 nm and 1304 nm) with the absorption of 99.2% and 99.9% have been achieved, respectively. The physical origin of perfect absorption peaks are related to the Fabry-Perot resonance effect and localized surface plasmon resonance (LSPR) of the nanoring grooves. Its perfect absorption and resonance wavelength can be well regulated by adjusting the relevant structural parameters. Additionally, the absorber demonstrates good operation angle-polarization-tolerance at wide incident angles (0–60°). We believe that our design has a promising application in plasmon-enhanced photovoltaic, optical absorption switching, and modulator optical communications in the infrared regime.

     

Light intensity and wavelength influence development, reproduction and locomotor activity in the predatory flower bug Orius sauteri (Poppius) (Hemiptera: Anthocoridae)

Light wavelength and intensity are physical factors that can affect arthropod development and reproduction. The present study examined the development, reproduction and locomotor activity of the predatory flower bug, Orius sauteri (Poppius) (Hemiptera: Anthocoridae), under five light intensities (1000, 2000, 3000, 4000 and 5000 lux) and five wavelengths [red (678.5 nm), green (620.0 nm), yellow (581.7 nm), blue (478. 1 nm) and white (all wavelengths)] at constant temperature (25 °C) and RH (70 %). The duration of nymphal development was extended at lower light intensities, primarily due to effects on the first three instars. Under white, yellow and green light, O. sauteri completed development in 18.0 days, but blue light extended development by 3.2 days and red light extended it by 7.4 days. Although lower light intensities extended the preoviposition period and reduced fecundity, they improved egg fertility. Both red and blue light negatively affected preoviposition period, fecundity and egg fertility. Whereas adult female mean walking speed over a five min period was reduced at lower light intensities, longer wavelengths (yellow and red) increased it, ostensibly reflecting an avoidance response. The respiration quotient of adult O. sauteri females was also elevated under red light conditions. These findings are informative for optimizing O. sauteri mass-rearing procedures and maximizing its efficacy as a biological control agent in greenhouse cultures.     

Influence of MLS laser radiation on erythrocyte membrane fluidity and secondary structure of human serum albumin

The biostimulating activity of low level laser radiation of various wavelengths and energy doses is widely documented in the literature, but the mechanisms of the intracellular reactions involved are not precisely known. The aim of this paper is to evaluate the influence of low level laser radiation from an multiwave locked system (MLS) of two wavelengths (wavelength = 808 nm in continuous emission and 905 nm in pulsed emission) on the human erythrocyte membrane and on the secondary structure of human serum albumin (HSA). Human erythrocytes membranes and HSA were irradiated with laser light of low intensity with surface energy density ranging from 0.46 to 4.9 J cm^?2 and surface energy power density 195 mW cm^?2 (1,000 Hz) and 230 mW cm^?2 (2,000 Hz). Structural and functional changes in the erythrocyte membrane were characterized by its fluidity, while changes in the protein were monitored by its secondary structure. Dose-dependent changes in erythrocyte membrane fluidity were induced by near-infrared laser radiation. Slight changes in the secondary structure of HSA were also noted. MLS laser radiation influences the structure and function of the human erythrocyte membrane resulting in a change in fluidity.     

Variations spectroscopiques induites par illumination et par action chimique observées à—196°C dans la chlorophylle a de Porphyridium

Spectroscopic Changes in the Chlorophyll a of Porphyridium Induced by Illumination and Chemical Action and Observed at ?196°C. Photo-oxidation of P700 by 708 nm light can take place under weak intensity (10^?6 W × cm^?2) when the medium is frozen. Spectral characteristics of “700 nm” and “690 nm” variations are accurately measured. The amplitude of the photoinduced changes of absorption are similar to those induced by chemical action. In the case of Porphyridium, an apparent increase of the extinction power of P700 at ?196°C is observed. This fact seems to be due to a diminution of the bandwith of the neighbouring pigments. Irradiation with red light (685 nm), of a relatively high intensity (10^?2 W × cm^?2), in the presence of oxygen at ?196°C, induces a slight shift (0.5 nm) of the red absorption band maximum towards longer wavelengths. This change is similar to the one promoted by ferricyanide in the dark. The origin and the functional significance of the phenomenon is discussed.     

Adaptations in Pigment Composition and Photosynthesis by Far Red Radiation in Chlorella pyrenoidosa

Chlorella pyrenoidosa has been cultivated in radiation of wavelengths between 690–975 nm for several months. Absorption spectra and action spectra of photo-synthesis have been determined for far red and “white” light brown cultures, In vivo spectrophotometric analyses and action spectra showed that fur red growth Chlorella adapted to the extreme light conditions by an increase both in absorption and photosynthesis above 700 nm. It is proposed that som of the in vivo normal chlorophyll a forms were converted to a far red absorbing chlorophyll a form, giving the far red exposed suspension an increased photosynthetic activity between 700–740 nm. The analyses of far red grown Chlorella have also shown an increased photosynthesis in the blue part of the spectrum, presumably due to a decrease in photosynthetically inactive carotenoid content. By culturing Chlorella in a “white” light gradient between 0.5 × 10⁴ and 3.7 × 10⁴ erg cm^?2 s^?1, it has been demonstrated that light intensity did not influence pigment ratios between 500–750 nm. In the blue part, however, high light levels caused increased absorption because of increased carotenoid content. Some ecological aspects of this far red effect have also been discussed.     

Two-photon conversion of a bacterial phytochrome

In nature, sensory photoreceptors underlie diverse spatiotemporally precise and generally reversible biological responses to light. Photoreceptors also serve as genetically encoded agents in optogenetics to control by light organismal state and behavior. Phytochromes represent a superfamily of photoreceptors that transition between states absorbing red light (Pr) and far-red light (Pfr), thus expanding the spectral range of optogenetics to the near-infrared range. Although light of these colors exhibits superior penetration of soft tissue, the transmission through bone and skull is poor. To overcome this fundamental challenge, we explore the activation of a bacterial phytochrome by a femtosecond laser emitting in the 1 μm wavelength range. Quantum chemical calculations predict that bacterial phytochromes possess substantial two-photon absorption cross sections. In line with this notion, we demonstrate that the photoreversible Pr ↔ Pfr conversion is driven by two-photon absorption at wavelengths between 1170 and 1450 nm. The Pfr yield was highest for wavelengths between 1170 and 1280 nm and rapidly plummeted beyond 1300 nm. By combining two-photon activation with bacterial phytochromes, we lay the foundation for enhanced spatial resolution in optogenetics and unprecedented penetration through bone, skull, and soft tissue.     

Wet Chemical Colorimetric Estimation of CO: An Update on the Reduced Silver Sol Spectral and Kinetic Transformations to Silver nanoparticle

Measurements of ppm (v/v) level CO_g concentration is conveniently performed by its preconcentration in alkaline absorber solution of Ag⁺-(4)- HCO₂-C₆H₄-SO₂NH₂ complex, followed by a spectral measurement of the reduced silver sol. In this study, the transitory nature of this latter species and its subsequent real-time transformation to silver nanoparticle are presented. These results were based on spectral measurements made under varying concentrations of alkali, (4)-HCO₂-C₆H₄-SO₂NH₂, and Ag⁺ in the absorber solution, and in the presence of a wide range of sampled CO_g concentration. The initially created light yellow colored sol with its broad absorption profile peaking at 380 nm and absorption coefficient 3500?±?300 cm^?1 M^?1 (related to the amount of sampled [CO_g] as standardized by gas chromatographic analysis) changed into the characteristic yellow orange nanoparticle with its plasmon band peak absorption at 425 nm and absorption coefficient 6350?±?300 cm^?1 M^?1. Under different sampling conditions, the respective first-order conversion rates varied between 0.03 and 0.15 h^?1, whereas simultaneous dynamic light scattering measurements revealed steady growth of the averaged particle size ranging from 60 to 300 nm.     

Contribution of LSP Effect to Light Absorption in Thin-Film Crystalline Silicon Solar Cells

Introducing periodic Ag gratings in the rear side of thin-film silicon excites localized surface plasmon (LSP) and Fabry-Perot (FP) effect. These two effects as well as an intrinsic one pass through absorption overlay together and all contribute to the light absorption in silicon. On the basis of electromagnetic field’s linear superposition, the absorptivity caused by LSP effect is separated from the overall absorptivity of a 500-nm-thick silicon and quantized by short current density. Finite difference time domain (FDTD) calculations were performed to obtain the absorptivity of silicon with different Ag grating parameters. The contribution of LSP effect to the light absorption is evaluated by photocurrent ratio and investigated under different Ag grating parameters. It is found that, as LSP effect is excited most intensively, the light absorption of silicon will also be enhanced extremely. By careful design, the overall short current density of silicon is optimized up to 25.4 mA/cm², where the contribution of LSP effect accounts for 38.6 %. Comparing to 14.5 mA/cm² for a reference silicon stack, it increases up to almost 75 %. These results may give design suggestions in implementation of plasmonic solar cell as high efficiency devices.     

Why is chlorophyll <Emphasis Type="Italic">b</Emphasis> only used in light-harvesting systems?

Chlorophylls (Chl) are important pigments in plants that are used to absorb photons and release electrons. There are several types of Chls but terrestrial plants only possess two of these: Chls a and b. The two pigments form light-harvesting Chl a/b-binding protein complexes (LHC), which absorb most of the light. The peak wavelengths of the absorption spectra of Chls a and b differ by c. 20 nm, and the ratio between them (the a/b ratio) is an important determinant of the light absorption efficiency of photosynthesis (i.e., the antenna size). Here, we investigated why Chl b is used in LHCs rather than other light-absorbing pigments that can be used for photosynthesis by considering the solar radiation spectrum under field conditions. We found that direct and diffuse solar radiation (PAR_dir and PAR_diff, respectively) have different spectral distributions, showing maximum spectral photon flux densities (SPFD) at c. 680 and 460 nm, respectively, during the daytime. The spectral absorbance spectra of Chls a and b functioned complementary to each other, and the absorbance peaks of Chl b were nested within those of Chl a. The absorption peak in the short wavelength region of Chl b in the proteinaceous environment occurred at c. 460 nm, making it suitable for absorbing the PAR_diff, but not suitable for avoiding the high spectral irradiance (SIR) waveband of PAR_dir. In contrast, Chl a effectively avoided the high SPFD and/or high SIR waveband. The absorption spectra of photosynthetic complexes were negatively correlated with SPFD spectra, but LHCs with low a/b ratios were more positively correlated with SIR spectra. These findings indicate that the spectra of the photosynthetic pigments and constructed photosystems and antenna proteins significantly align with the terrestrial solar spectra to allow the safe and efficient use of solar radiation.     

Spectral downwelling irradiance in an Antarctic lake

Summary Spectral downwelling irradiance (400–700 nm) was determined in the ice-covered Lake Hoare located in the dry valleys near McMurdo Sound, Antarctica. Full waveband PAR beneath the ice was <44E·m^-2·s^-1 or <3% of surface downwelling irradiance. Maximum light transmission just beneath the 2.6–4 m ice cover, which contained sediments and air bubbles, occurred between 400–500 nm. In the water column below, attenuation of light by phytoplankton in the 400–500 nm region and between 656–671 nm suggested absorption of light by algal pigments.     

Optical Properties of Noncontinuous Gold Shell Engineered on Silica Mesosphere

The optical properties of individual noncontinuous shells with different gold coverage are investigated by the single-particle dark field scattering measurements and single-particle surface-enhanced Raman scattering (SERS) measurements at different excitation wavelengths. By controlling the growth of gold seeds, multi-metallic nanogaps/crevices with different optical responses are assembled on silica mesospheres forming noncontinuous shells that can be confirmed through the transmission electron microscope images. We find the surface plasmon resonance of single shell red-shifts from 510 to 680 nm with the increase of gold coverage. At the excitation of 532 and 785 nm, the best enhancements about 2.0?×?10⁵ and 1.1?×?10⁷ are obtained on spheres with ～60 and 83 % gold coverage, respectively. The weak polarization-dependent SERS indicates that the enhancement is from the multi-gaps on single noncontinuous shell. This optical tunable and SERS active noncontinuous gold shell can be applied in biosensing, ultra trace detection, and molecule analysis needing multi-wavelengths excitation.     

The emission of floral scent from Lilium ‘siberia’ in response to light intensity and temperature

Floral scent is an important part of volatile compounds emitted from plants, and is influenced by many environmental factors. In this study, the floral scent emitted from Lilium ‘siberia’, a common breed of lily, was collected by dynamic headspace at different levels of light intensity (0, 100, 300, 600, 1,000, and 1,500 μmol m^?2 s^?1) and temperature (10, 20, 30, and 40 °C). Using the automated thermal desorption-gas chromatography/mass spectrometry (ATD-GC/MS) technique, the components and release amounts were subsequently identified to investigate the influence of light and temperature on the emission of floral scent. The results revealed that the numbers and release amounts of floral scent components were significantly influenced by light intensity and temperature, showing the similar pattern: first increasing and then decreasing. After light intensity treatment, the maximum numbers and release amounts mainly appeared at 600 and 1,000 μmol m^?2 s^?1. For temperature treatment, 30 °C resulted in the highest numbers and release amounts of the floral scent components. At different levels of light intensity and temperature, terpenoid compounds showed the highest numbers and release amounts among the component categories. α-Ocimene and linalool were the two terpenoid compounds with the highest release amounts, and accounted for the highest proportion. The results obtained provide evidence that both light intensity and temperature trigger the emission of floral scent. The particular response mechanisms must be investigated in future research.