Green Radiation Research Articles

Photosensitive free-standing ultra-thin carbyne–gold films

In the article we introduce the experiment of the photostimulation effect in the tunneling conductivity of free-standing thin carbyne-gold films. We observe a sharp increase of the conductivity of hybrid film due to the electromagnetic exciting at the frequencies which are close to the plasmon resonance of gold nanoparticles. The use of carbyne threads as a stabilizing matrix makes it possible to obtain free-standing thin films that demonstrate a good structural stability. The tunnel current–voltage measurements demonstrate a strong dependence of the current value on the intensity of green laser radiation used to photostimulate thin C–Au in area of the measuring experiment.

Laser-induced optically modified Se58Ge27Pb15 and Se58Ge24Pb18 thin films

ABSTRACTAmorphous samples of Se58Ge27Pb15 and Se58Ge24Pb18 glasses were prepared using the melt quenching method. Thin films of samples were deposited using the vacuum evaporation method. These films were illuminated with Nd: YAG 532 nm green laser radiation. The samples were structurally characterised using X-ray Diffraction (XRD) and Energy-dispersive X-ray analysis. XRD indicated an increase in the crystallinity of samples on laser irradiation. The samples were optically tested through absorption, reflection and transmission spectra recorded on UV-vis spectrophotometer. The obtained values of energy band gap, refractive index, extinction coefficient and Urbach energy of the films were compared both before and after laser exposure. Furthermore, it was found that sample thickness also changes on laser irradiation. The band gap of the samples was found to decrease laser irradiation in Se58Ge27Pb15thin films, while for Se58Ge24Pb18 thin film samples, an unexpected increase in band gap was observed at a laser irradiation time of 8 min. The variable behaviour of band gap has been explained on the basis of Mott and Davis model and heteropolar bond formation.

Visible light photocatalytic activity of Cu, N co-doped carbon dots/Ag3PO4 nanocomposites for neutral red under green LED radiation

In current investigation, we synthesized a new Cu, N co-doped carbon dots/Ag3PO4 (Cu, N-CDs/Ag3PO4) nanocomposite by one-step thermolysis and precipitation method. In addition, we evaluated the activity of Ag3PO4 and Cu,N-CDs/Ag3PO4 nanomaterials in degrading an environmental pollutant called neutral red under visible radiations. Compared to the pure Ag3PO4, Cu, N-CDs/Ag3PO4 had shown high degradation efficiency by more than 25% and shown good recyclability. The synthesized nanocomposite was characterized by XRD, HRTEM, FT-IR, Raman and XPS techniques. The optical property of Cu, N-CDs/Ag3PO4 nanocomposite was examined with UV–vis DRS (Diffuse Reflectance Spectroscopy). And the excellent photocatalytic performance of this Cu, N-CDs system was ascribed to the increased conversion of ·O2− under visible light irradiations and effective separation of electron-hole pairs, results in inhibited photocorrosion of the system. Also, this nanocomposite could successfully degrade the neutral red dye (mention the concentration) about 95.5% under LED irradiations within 60 min.

Features of measuring the brightness of the screens

The situation with the metrological assurance of brightness measurements in Ukraine is analyzed. The main regulatory documents for the characterization of lux meters are considered. It was noted, that the components of the uncertainty of brightness due to the difference in the spectral composition of radiation, during calibration and measurement, as well as uncertainties due to spatial heterogeneity of the screens, are not fully considered. The characteristic values of these uncertainties are calculated by the method of mathematical modeling, using generally accepted calculation methods. To calculate the spectral errors, the literature data on the spectra of CCFL and LED monitors were used, as well as the modeling of the spectra of blue, green and red radiation sources, using Gaussian distribution with varying widths. It is shown, that for а brightness meter calibrated by а type A source, the use of white screens for measuring the brightness will result in errors, less than 7%. It is shown, that when calibrating the brightness meter using the CCFL screen and then using the LED for the screen, the errors will be about 1%. Simple formulas are given to evaluate the effect of screen heterogeneity. For а refined assessment of the influence of spatial inhomogeneity, mathematical modeling was carried out — 3 types of brightness distribution, were used with decreasing radiation distribution density and two types of viewing area — а circle (imitation of brightness measurement, using а diaphragm) and а Gaussian distribution (imitation of brightness measurement with а lens) equal widths. It is shown, that for the field of sight in the form of а Gaussian distribution, the influence of the inhomogeneity of the distribution of screen illumination, when moving and changing the width of the field of sight is insignificant. Two approaches have been proposed for building the material base for metrological assurance of brightness measurements.

Up-conversion photoluminescence properties and energy transfer process of Ho3+,Yb3+ Co-doped BaY2F8 fine fibers

An intermediate product was obtained by sintering PVP/[Ba(CH3COO)2+Y(NO3)3+Ho(NO3)3+Yb(NO3)3] fine fibers prepared by electrospinning. The Ho3+,Yb3+:BaY2F8 fine fibers were obtained by sintering the above products using a double-crucible reduction atmosphere fluorination technology. X-ray diffraction data analysis showed that pure monoclinic phase of Ho3+,Yb3+:BaY2F8 fine fibers was C2/m space group. Scanning electron microscopy (SEM) was used to test the morphology, indicating the size of the fine fibers is near 269 nm. By analyzing the up-conversion fluorescence spectrum, strong green and weak red up-conversion radiation at 536 nm and 658 nm were obtained with the optimal doping concentrations of Ho3+ and Yb3+ ions of 1% and 8%, respectively. The up-conversion luminescence mechanism of Ho3+,Yb3+:BaY2F8 fine fibers and the fluorescence lifetime at 536 nm have also been studied in detail.

Substituting green or far-red radiation for blue radiation induces shade avoidance and promotes growth in lettuce and kale

Although red (R; 600–700 nm) and blue (B; 400–500 nm) radiation can be sufficient for plants grown indoors, other wavebands such as green (G; 500–600 nm) and far red (FR; 700–800 nm) can also regulate photosynthesis, plant morphology, and secondary metabolism. The objective of this study was to determine how substitutions of B radiation with G and/or FR radiation influence growth of leafy greens grown indoors under light-emitting diodes (LEDs). We postulated G and/or FR radiation (and low B radiation) would trigger shade-avoidance responses and thus promote biomass accumulation through increased radiation interception. We grew lettuce (Lactuca sativa ‘Rex’ and ‘Rouxai’) and kale (Brassica oleracea var. sabellica ‘Siberian’) under warm-white (WW) LEDs at 180 μmol·m–2·s–1 (400–800 nm) for 9–11 days and then transplanted seedlings into a hydroponic system with ten different lighting treatments. The air temperature (20 °C), photoperiod (20 h), total photon flux density (180 μmol·m–2·s–1; 400–800 nm), and fertility were maintained the same across treatments. In addition to WW and equalized-white (EQW) controls, combinations of B (peak =449 nm), G (peak =526 nm), and FR (peak =733 nm) LEDs, each at 0, 20, 40, or 60 μmol·m–2·s–1, were delivered in a R background (peak =664 nm) of 120 μmol·m–2·s–1. One month after seed sow, we collected data on shoot mass, leaf morphology, and pigmentation. Substituting G or FR radiation for B radiation promoted leaf expansion and increased shoot mass but decreased chlorophyll concentrations in all crops. For example, lettuce ‘Rex’ grown under 60 μmol·m–2·s–1 of G +120 μmol·m–2·s–1 of R radiation was 38% greater in plant diameter and 54% greater in shoot dry mass compared to those under 60 μmol·m–2·s–1 of B +120 μmol·m–2·s–1 of R radiation. Substituting B radiation with G radiation at 60 μmol·m–2·s–1 also reduced red coloration of lettuce ‘Rouxai’. At the same photon flux density, FR radiation increased leaf expansion and decreased red foliage coloration more than G radiation. We conclude that substituting G and/or FR radiation for B radiation triggers shade-avoidance responses, accelerating plant growth while decreasing pigment concentrations.

Synthesis, structural, photoluminescence, thermal, mechanical, dielectric, nonlinear optical and laser damage threshold studies of 2,3-dimethylquinoxalinium-4-chlorobenzenesulphonate

2,3-Dimethylquinoxaline-4-chlorobenzenesulphonate (DMQPCS) was synthesized successfully and grown as single crystals from 1:1 MeOH and water solvent mixture using slow evaporation method. Single crystal XRD analysis confirms that the molecular salt crystallizes in orthorhombic system with non-centrosymmetric space group, Pca21 and the crystal is stabilized by N+-H…O, O–H…O, N–H…O and C–H…O hydrogen bonding interactions. The presence of expected functional groups and the molecular structure were identified by FT-IR and NMR spectroscopic studies. Lower cut-off wavelength, % transmittance and optical band-gap value were determined by UV-Vis-NIR spectral analysis. The photoluminescence studies confirm green emission radiation. The thermal and mechanical behaviour were analyzed by TG-DTA analyses and Vickers microhardness tester, respectively. The SHG efficiency and laser damage threshold were measured using an Nd:YAG laser of wavelength 1064 nm. Variation of the dielectric response of the grown crystal was studied at different temperatures.

Wavelength dispersion phenomena observed for emitted optical radiation from a p+nn+ silicon avalanche mode light-emitting device in a radio frequency bipolar-integrated circuitry

A two-junction micro p+np+ silicon avalanche-mode light-emitting device (Si AMLED) is analyzed for its dispersion characteristics, which generally resulted in different wavelengths of light (colors) being emitted at different angles from the surface of the device. The SiAMLED is integrated into on-chip bipolar radio frequency-integrated circuitry at micron dimensions. LEDs have high-frequency modulation frequencies reaching into the GHz range. Such devices, which are of micron dimension, operate at 8 to 10 V, 1 μA to 2 mA. The emission wavelength is in the 450- to 850-nm range, emission spot sizes are about 1 μm2, and emission intensities are up to 200 nW . μm − 2. The observed geometrical-chromatic dispersion characteristics range from 0.01 deg / nm wavelength for green radiation at a 5 deg exit angle to the normal of the device to 0.16 deg / nm wavelength for blue radiation at a 60 deg exit angle to the normal of the surface of the device. The high dispersion characteristics of the emitted radiation are attributed to the positioning of the optical source ∼1 μm subsurface to the silicon–silicon oxide interface, as well as to the high-refractive index differences between silicon and the surrounding lower refractive index silicon oxide layers. It is believed that the identified dispersion characteristics will have interesting and futuristic on-chip electro-optic applications for on-chip micro-optical wavelength dispersers, futuristic optical communication demultiplexers, along with on-chip microgas and biosensor applications.

The Physiotherapy in the treatment of alveolitis and localized osteomyelitis of the jawbones

Alveolitis and localized osteomyelitis of the jawbones still remain the most common conditions among the post-operative complications associated with tooth extraction. The objective of the present study was to evaluate the antibacterial and clinical effectiveness of ozone therapy and radiation of various wavelengths emitted by the light-emitting diodes (LED) applied for the treatment of alveolitis and localized osteomyelitis of the jawbone with a view to improving the effectiveness of the treatment and shortening the duration of the rehabilitation period. A total of 100 patients presenting with alveolitis and localized osteomyelitis of the jawbones at the age varying from 18 to 65 years have been examined and treated. All the patients were divided into four equal groups. The first group (1) was comprised of the patients who were treated with the combination of the measures which included the course of ozone therapy and LED-emitted red light radiation (630 nm); the patients of the second group (2) were treated using ozone therapy in the combination with LED-emitted green light radiation (530 nm); in the third group (3), ozone therapy in the combination with LED-emitted (470 nm) blue light radiation was used. The patients of the fourth group (4) were managed without the application of the physiotherapeutic factors. To study the effects of ozone therapy and LED-emitted radiation of different wavelengths on the microflora of the extracted tooth socket, the bacteriological analysis was carried out three times - before the treatment, within three and five days after its initiation. The present study has demonstrated that the combination of ozone therapy with LED-emitted (630 nm) red light radiation provides the most efficient tool for the treatment of alveolitis whereas ozone therapy in the combination with LED-emitted (470 nm) blue light radiation should be preferred for the treatment of localized osteomyelitis of the jawbone. The results of this study are of primary importance as giving evidence of the significant reduction in the duration of the rehabilitation period in the patients presenting with alveolitis and localized osteomyelitis of the jawbones.

Wavelength-Dependent Efficiency of Sequential Photooxygenation: C=C Bond Cleavage on Open-Cage C60 Derivatives.

We have studied the efficiency of the C=C double bond cleavage on open-cage fullerene C60 derivatives by singlet oxygen using four different LED lamps including UV, blue, green, and red radiation. The results indicate that red radiation is the most efficient for this photochemical oxidation owing to the sufficient penetration of the longer-wavelength light. By applying this method to a 2-methoxyethoxymethyl-substituted azafulleroid derivative, we demonstrated the sequential double photooxygenation which provides a symmetric diketo imide derivative having a 15-membered-ring opening via stepwise cleavage of two C=C double bonds. Using a H2 -encapsulating derivative, we further examined the size of the opening by comparison with the structural isomer, based on H2 -release experiments and theoretical calculations.

FEASIBILITY INVESTIGATION ON SINGLE PHOTON LIDAR BASED WATER SURFACE MAPPING

Abstract. The recent advent of single photon sensitive airborne LiDAR (Light Detection And Ranging) sensors has enabled higher areal coverage performance at the price of an increased outlier rate and a lower ranging accuracy compared to conventional Multi-Photon LiDAR. Single Photon LiDAR, in particular, uses green laser light capable of penetrating clear shallow water. Although primarily designed for large area topographic mapping, the technique can also be used for mapping the water surface and shallow water bathymetry. In this contribution we investigate the capability of Single Photon LiDAR for large area mapping of water surface heights. While interface returns from conventional green-only bathymetric sensors generally suffer from water level underestimation due to the water penetration capabilities of green laser radiation, the specific questions are, if Single Photon LiDAR (i) is less affected by this well known effect due to the high receiver sensitivity and (ii) consequently delivers a higher number of water surface echoes. The topic is addressed empirically in a case study by comparing the water surface responses of Single Photon LiDAR (Navarra, Spain) and Multi-Photon Topo-Bathymetric LiDAR (Neubacher Au, Austria) for selected water bodies with a horizontal water surface (reservoirs, ponds). Although flown at different altitudes, both datasets are well comparable as they exhibit the same strip point density of ca. 14 points/m2. The expected superiority of Single Photon LiDAR over conventional green-only bathymetric LiDAR for mapping water surfaces could not be verified in this investigation. While both datasets show good agreement compared to a reference water level when aggregating points into cells of 10 × 10 m2 (mean deviations < 5 cm), higher resolution Single Photon LiDAR based water surface models (grid size 1–5 m) show a systematic water level underestimation of 5–20 cm. However, independently measured ground truth observations and simultaneous data acquisition of the same area with both techniques are necessary to verify the results.

Effect of green, yellow and purple radiation on biomass, photosynthesis, morphology and soluble sugar content of leafy lettuce via spectral wavebands “knock out”

Abstract Spectral composition of artificial light is an important environmental factor for plants cultivated in controllable environment, eg., plant factory. In an attempt to explore the influence of different spectral wavebands on leaf lettuce growth and development, a new way of light treatment with turning off the specific narrow-wavebands from the wide spectrum was established. And leaf lettuce was cultivated under different light spectra with the spectral wavebands of green (LG), yellow (LY) and purple (LP) “knockout” respectively in controllable environment. Then changes in biomass, morphological indexes, photosynthetic gas exchange, chlorophyll content and soluble sugar content of lettuce were examined. Our results revealed that, compared with plants grown under wide-spectral LED light (CK), LG treatment showed significantly reduction of fresh shoot weight at 25 days after planting (DAP) comparing to CK. LY and LP obtained obviously higher fresh shoot weight and moisture content at 15 DAP, in contrast, significantly lower ratio of root to shoot than CK. And A/Ci in LG were significantly reduced by about 33.3% and 36.1% at 20 DAP and 25 DAP respectively compared with CK. In addition, LY showed significant increases in soluble sugar content compared to other treatments at three sampling stages, while the lowest values were obtained in CK. These results indicated that green, yellow and purple light had significant regulations on the biomass, photosynthesis and soluble sugar content in lettuce, depending on the different growth period.

Enhanced upconversion emission and temperature sensor sensitivity in presence of Bi3+ ions in Er3+/Yb3+ co-doped MgAl2O4 phosphor

Mg0(.95-x)ErxYb0.05Al2O4 (x = 0.3, 0.5, 0.7, 1.0, and 1.5 mol%) and Mg(0.943-y)Er.007Yb0.05BiyAl2O4 (y = 2, 5, 7, 10, and 15 mol%) phosphor samples have been synthesized by solid state reaction method. The X-ray diffraction (XRD) measurements confirm the cubic phase formation and shift in peaks position due to Bi3+ ions doping. The surface morphology of the prepared samples has been studied by scanning electron microscopy (SEM) measurement. The FTIR spectra reveal the information about the vibrational bands arising due to different molecules or species/groups. The Mg(0.943-y)Er0.007Yb0.05Al2O4 phosphor sample gives an intense upconversion (UC) green emission peaks centered at ~ 521 and 543 nm due to (4S3/2, 2H11/2)→4I15/2 transitions and the weak red emission at 660 nm due to 4F9/2→4I15/2 transition. The emission intensity of green bands is enhanced by 30 times and the red band by 10 times on addition of Bi3+ in Mg (0.943) Er0.007Yb0.05Al2O4 phosphor. This increase in emission intensity also enhances the fluorescence intensity ratio (FIR) of two thermally coupled levels emitting green radiation (i.e. FIR = I521/I543). The large variations of FIR with temperature clearly suggest that the material can be used as temperature sensor. The temperature sensing sensitivity is found to be quite high in presence of Bi3+ ions. The laser induced optical heating with pump power has also been observed in this material.

Mineral inclusions in diamonds from Chapada Diamantina, Bahia, Brazil: a Raman spectroscopic characterization

Abstract The Chapada Diamantina, located in the central region of the State of Bahia, is of important historical significance due to its diamond occurrences. Discovered in the nineteenth century, comprehensive research about the regional diamonds and their origins are still limited, demanding more investigation in the matter. Looking for insights about their genesis, mineral inclusions in 23 alluvial diamonds from 4 garimpos located in the Chapada Diamantina were analyzed through the use of Raman micro spectroscopy. Additionally, the characteristics of nitrogen aggregation of the host diamonds were measured using Fourier-transform infrared spectroscopy (FTIR). The diamonds from Chapada Diamantina consist mainly of well-formed crystals, with dominant dodecahedral habits, characterized by faint to very light yellow body colors, typically with green and brown radiation spots on their surface. The main surface textures observed are related to processes that took place in the late stage resorption and during the residence of the diamonds in placer environments. The diamonds are predominantly type IaAB, with a significant occurrence of poorly aggregated nitrogen (Type IaA diamond). The main mineral assemblages of the studied peridotitic inclusions refer to a harzburgitic paragenesis.

Synthesis of nanotubes under carbon environment at low temperature using hydrothermal method

Carbon nanotubes (CNTs) are new birth in nanotechnology which becomes a pillar for scientific research due to its vast application in the feild of spintronics, optical and optoelectronics materials. In the present days, CNT are highly synthesized by various popular methods which are carried out under high temperature. So, here in present work CNTs are synthesised by low temperature at 160 °C with familiar hydrothermal method using precursors as Ethanol, Polyethylene Glycol (PEG) and Sodium hydroxide with reaction time of 20 h. Here nanotubes are formed by decomposition of PEG using activating agent NaOH which enhances the decomposition of PEG. From X-ray diffraction (XRD) crystalline nature, crystal structure, average nanotube size, dislocation density are found out. And also, by Williamson hall plot strain is calculated. The presence of different functional groups and the metallic transmittance are confirmed by Fourier Transform Infra Red (FTIR) spectrum. The destination point of absorbance is found out by Ultra-Violet Visible (UV–vis) spectral analysis. And also by Tauc plot direct and indirect band gap are calculated. CNTs are readily emits green radiations which confirmed by Photoluminescence (PL) spectrum. The morphological surveys are done using Scanning Electron Microscope (SEM).

Green's Function and Radiation over a Periodic Surface: Reciprocity and Reversal Green's Function

Green's Function and Radiation over a Periodic Surface: Reciprocity and Reversal Green's Function

Laser welding of copper using a high power disc laser at green wavelength

The trend towards renewable energies and electromobility is increasing the demand for copper. Laser welding as a flexible and fully automatable process is being more frequently employed to join copper materials. The use of green laser radiation compared to infrared laser radiation has the advantage of a significantly higher absorption coefficient for copper materials. Therefore, high power laser sources emitting at a green wavelength promise a more stable and a more efficient process. In this paper, experimental investigations with a green continuous wave laser radiation at a maximum power of 1 kW are presented. Using design of experiments, the process limits are determined depending on the laser power and the welding velocity. Furthermore, the potential of heat conduction welding using this laser source is investigated.

Multiline Operation from a Single Plasmon-Assisted Laser

The demonstration of plasmon-assisted lasing by associating optical gain media with plasmonic nanostructures has led to a new generation of nanophotonic devices with unprecedented performances. However, despite the variety of designs demonstrated so far, the operation of these systems is in most cases limited to a single output wavelength, and some reports on multiline emission refer to mixing single nanolasers with the subsequent limitation in compactness. Here, we show multiline operation from a single plasmon-assisted nonlinear solid-state laser on which a linear chain of Ag nanoparticles is deposited. The system provides lasing at 1.08 µm, which is self-converted to the visible range through different parametric frequency-mixing processes generated at metal-dielectric interfaces. Near infrared and simultaneously green and tunable blue radiation with a sub-wavelength confinement in the direction perpendicular to the nanoparticle chain, are obtained at room temperature in CW regime. The results demonstr...

Efficient generation of linearly polarized Cerenkov radiation in a photonic crystal fiber with suspended rectangle core

We report high efficiency linearly polarized Cerenkov radiation (CR) generation in a photonic crystal fiber with suspended rectangle core. The frequency up-conversion via the Cerenkov radiation upon pumping of Yb-doped femtosecond fiber laser is discussed in details. Experiment results show that the output spectrum contains, besides the infrared supercontinuum, intense green Cerenkov radiation around 536 nm, which carry about 43% of the pump energy at best. The influence of the high birefringence and dispersion character on the Cerenkov radiation generation is discussed. Experiment and simulation results indicate that the rectangle core photonic crystal fiber acts like single-mode single-polarization fiber at the pump wavelength. Only the pulse component along with the slow axis could be confined in the rectangle core well and release Cerenkov radiation efficiently. The Output green Cerenkov radiation is also demonstrated to be linearly polarized. Experiments results agree well with the theoretical predictions.

Thermo-plasmonic effects on E7 nematic liquid crystal

ABSTRACTThe photo-induced heating from a layer of uniformly distributed gold nanoparticles has been characterized to investigate the impact of a direct interaction of the metallic nanostructures with a drop of E7 nematic liquid crystal. A double effect is obtained: an increase of the photo-induced heating due to a change in the refractive index of the medium surrounding the nanoparticles (from air to E7) and a new way of exploiting this heating to induce a phase transition of the E7 NLC (from anisotropic to isotropic phase), with a significant decrease of the necessary energy density in the case of an impinging green radiation.