Red Spectral Region Research Articles

A Broadband Green-Red Vegetation Index for Monitoring Gross Primary Production Phenology

The chlorophyll/carotenoid index (CCI) is increasingly used for remotely tracking the phenology of photosynthesis. However, CCI is restricted to few satellites incorporating the 531 nm band. This study reveals that the Moderate Resolution Imaging Spectroradiometer (MODIS) broadband green reflectance (band 4) is significantly correlated with this xanthophyll-sensitive narrowband (band 11) ( R 2 = 0.98 , p < 0.001 ), and consequently, the broadband green-red vegetation index GRVI—computed with MODIS band 1 and band 4—is significantly correlated with CCI—computed with MODIS band 1 and band 11 ( R 2 = 0.97 , p < 0.001 ). GRVI and CCI performed similarly in extracting phenological metrics of the dates of the start and end of the season (EOS) when evaluated with gross primary production (GPP) measurements from eddy covariance towers. For EOS extraction of evergreen needleleaf forest, GRVI even overperformed solar-induced chlorophyll fluorescence which is seen as a direct proxy of plant photosynthesis. This study opens the door for GPP and photosynthetic phenology monitoring from a wide set of sensors with broadbands in the green and red spectral regions.

Transcatheter Intracerebral Laser Photobiomodulation Therapy Reduces Dementia and Cognitive Impairment in Patients with Various Stages of Alzheimer's disease

Background: Alzheimer's disease (AD) is the leading neurodegenerative disease associated with dementia and cognitive impairment. A major achievement in AD treatment was the use of lasers with low output power of the red or near-infrared spectral region, which was named Photobiomodulation Therapy (PBMT). Aims: This study investigates the effect of PBMT on regression of dementia and cognitive impairment among patients with various AD stages. Methods: For the study, 97 patients with previously diagnosed AD, aged 34-80 (mean age 67.5), 34 (35.05%) men, 63 (64.95%) women, were selected. According to AD severity, the patients were subdivided: preclinical stage TDR-0 - 10 (10.31%), mild stage TDR-1 - 28 (28.87%), moderately severe stage TDR-2 - 42 (43.30%), severe stage TDR-3 - 17 (17.52%). Test Group - 48 (49.48%) patients, 17 (35.42%) men, 31 (54.58%) women, underwent Transcatheter Intracerebral Laser Photobiomodulation Therapy (PBMT). Control Group - 49 (50.32%) patients, 16 (32.65%) men, 33 (67.35%) women, underwent conservative treatment with Memantine and Rivastigmine. Results: Test Group. Due to angiogenesis and neurogenesis stimulation with Transcatheter Intracerebral Laser Photobiomodulation Therapy (PBMT), all the patients had an improvement in cerebral blood supply and microcirculation and a decrease in cerebral involutive changes. Consequently, all the patients showed reduced dementia and improved cognitive abilities. The vast majority of the patients began to correspond to the group of a milder AD stage. Control Group. No persistent expressed positive dynamics. Partial improvement was obtained only among patients with early AD stages. Conclusion: Transcatheter Intracerebral Laser Photobiomodulation Therapy (PBMT) is an effective, physiologically based method of stimulating cerebral angiogenesis and neurogenesis. As a result of such a complex impact, patients with various AD stages have cerebral capillary collateral revascularization, their tissue metabolism improves, and regenerative processes develop in the cerebral tissue. Tissue regeneration leads to an increase in the volume of the temporal and frontoparietal sections. Clinically, this leads to a stable decrease in dementia level, cognitive functions restoration, and improved quality of patients’ life. The resulting clinical effect lasts for many years. Conservative treatment with Memantine and Rivastigmine is not effective enough.

Highly sensitive temperature reading from intensity ratio of Eu3+ And Mn4+emissions in Y3Al5O12 nanocrystals

Potential of Eu3+, Mn4+ co-doped YAG for dual-activated luminescence intensity ratio thermometry is investigated. The samples were prepared by modified Pechini method and cubic structure confirmed by X-ray diffraction with average crystallite size of ∼ 20 nm. Scanning electron microscopy revealed different sized chunks composed of ellipsoidal-shaped particles bellow 50 nm. Temperature-dependent photoluminescent emission spectra (λex = 465 nm, 98–473 K temperature range) of co-doped samples consist of emission bands in the red spectral region originating from both Eu3+and Mn4+transitions. Concentration of Mn4+ and Eu3+ is optimized to be 0.5mol% and 3mol%. Observed suppression of Eu3+ emission indicate an efficient (∼97%) energy transfer from Eu3+ to Mn4+. Using luminescence intensity ratio as the ratio between the integrated intensities of the Eu3+ 5D0→7F1 transition and the Mn4+ 2E→4A2manyfold, maximal absolute and relative sensitivities of SAmax = 19.2mK−1 at 351 K and SRmax = 5.06%K − 1 at 321 K were calculated.

The role of gold metallic particles on improving green and NIR emissions of Ho3+ ions in non-conventional SeO2 based glass ceramics

This study is devoted to investigate the role of Au0 particles on the improvement of luminescence efficiency of Ho3+ ions in a non-conventional lead boroselenate glass ceramic. Characterization by different spectroscopic techniques indicated that the samples consist of [SeO3]2− and [SeO4]2− structural groups. Among them, the fraction of [SeO3]2− groups exhibited an increasing trend with increase of Au2O3 content. These studies have further revealed that a part of Au3+ ions reduced in to gold nano particles during ceramicization process. Optical absorption (OA) spectra of these samples exhibited a wide absorption band with gradual growth with the Au2O3 concentration. This band is attributed to the surface plasmon resonance (SPR) of gold nanoparticles. Additionally, the OA spectra exhibited several characteristic bands of Ho3+ ions in the spectral region of 450–2000 nm. Photoluminescence (PL) spectra of (Ho free samples) containing gold particles exhibited a broad band in the green to red spectral region, identified due to the transition of electrons from sp → d energy bands of gold nanoparticles. PL spectra of co-doped samples exhibited the emission bands in the green, orange and red regions with enhanced intensities as Au2O3 content is increased. OA and PL spectra were characterized using Judd-Ofelt theory and various radiative parameters were estimated. The impact of Au0 particles on the PL efficiency of holmium ions is comprehensively discussed using kinetic rate equations. The crucial role of gold particles as sensitizers in enhancing the luminescence efficiency especially the green emission is quantitatively explained.

Seawater-cultured Spirulina subsalsa as a more promising host for phycocyanin production than Arthrospira platensis

C-phycocyanin produced from Arthrospira platensis is of great commercial interest in healthcare industries but adoption is challenged by low quality and productivity. To find a high-quality alternative to Arthrospira platensis, this study compares C-phycocyanin production by Spirulina subsalsa and Arthrospira platensis in chemically defined freshwater medium and seawater with added monosodium glutamate residue. In the two media, Spirulina subsalsa showed higher content and first-extraction efficiency of C-phycocyanin than Arthrospira platensis did. Absorption maxima in red and blue spectral regions were observed for the first time to shift toward longer wavelengths for methanolic extracts of the cyanobacteria grown in seawater. Tightly coiled Spirulina subsalsa remained unaffected and exhibited stronger adaptation in a seawater environment than loosely spiralled Arthrospira platensis. These results preliminarily demonstrate the feasibility of cultivating Spirulina subsalsa in seawater with low-cost nutrient supplements as a promising candidate to produce C-phycocyanin as well as to reduce nutritional and freshwater investments. Overall, more research can be performed redarding culture conditions and extraction process to optimize C-phycocyanin production and extraction.

Red Light-Emitting Water-Soluble Luminescent Iridium-Containing Polynorbornenes: Synthesis, Characterization and Oxygen Sensing Properties in Biological Tissues In Vivo.

New water-soluble polynorbornenes P1–P4 containing oligoether, amino acid groups and luminophoric complexes of iridium(III) were synthesized by ring-opening metathesis polymerization. The polymeric products in organic solvents and in water demonstrate intense photoluminescence in the red spectral region. The polymers P1 and P3 with 1-phenylisoquinoline cyclometalating ligands in iridium fragments reveal 4–6 fold higher emission quantum yields in solutions than those of P2 and P4 that contain iridium complexes with 1-(thien-2-yl)isoquinoline cyclometalating ligands. The emission parameters of P1–P4 in degassed solutions essentially differ from those in the aerated solutions showing oxygen-dependent quenching of phosphorescence. Biological testing of P1 and P3 demonstrates that the polymers do not penetrate into live cultured cancer cells and normal skin fibroblasts and do not possess cytotoxicity within the concentrations and time ranges reasonable for biological studies. In vivo, the polymers display longer phosphorescence lifetimes in mouse tumors than in muscle, as measured using phosphorescence lifetime imaging (PLIM), which correlates with tumor hypoxia. Therefore, preliminary evaluation of the synthesized polymers shows their suitability for noninvasive in vivo assessments of oxygen levels in biological tissues.

Formation of holographic diffraction gratings in thin films of chalcogenide glassy semiconductors

The paper presents a study of the formation of holographic diffraction gratings in thin films of chalcogenide glassy semiconductors. The recording process of holographic gratings at the argon-laser radiation wave length 488 nm and the process of chemical etching that enables the formation of а relief holographic grating are analysed. The optimum conditions for the formation of diffraction gratings in films of arsenic sulfide As2S3 are defined. It is shown that at the 488 nm wave length of an argon laser the optimum exposure comes to ∼5–8 J/cm2. At the recording stage a quasi-phase (relief-phase) grating is formed, with the diffraction efficiency on the order of a few per cent. Etching of the exposed sample with a solution of NaOH alkali in deionised water and isopropanol makes it possible to increase considerably the relief depth and to improve the diffraction efficiency of a thin diffraction grating approximately up to 20 % for the red spectral region, and to approach the maximal value ∼34 % for the near infra-red region. The results of the study considered look promising for the creation of relief holographic gratings which are essential in present-day optical instrument building (production of spectral devices, holographic sights, and the like).

Plasmon-Enhanced Photoresponse of Self-Powered Si Nanoholes Photodetector by Metal Nanowires.

In this work, we report the development of self-powered photodetectors that integrate silicon nanoholes (SiNHs) and four different types of metal nanowires (AgNWs, AuNWs, NiNWs, PtNWs) applied on the SiNHs’ surface using the solution processing method. The effectiveness of the proposed architectures is evidenced through extensive experimental and simulation analysis. The AgNWs/SiNHs device showed the highest photo-to-dark current ratio of 2.1 × 10−4, responsivity of 30 mA/W and detectivity of 2 × 1011 Jones along with the lowest noise equivalent power (NEP) parameter of 2.4 × 10−12 WHz−1/2 in the blue light region. Compared to the bare SiNHs device, the AuNWs/SiNHs device had significantly enhanced responsivity up to 15 mA/W, especially in the red and near-infrared spectral region. Intensity-modulated photovoltage spectroscopy (IMVS) measurements revealed that the AgNWs/SiNHs device generated the longest charge carrier lifetime at 470 nm, whereas the AuNWs/SiNHs showed the slowest recombination rate at 627 nm. Furthermore, numerical simulation confirmed the local field enhancement effects at the MeNWs and SiNHs interface. The study demonstrates a cost-efficient and scalable strategy to combine the superior light harvesting properties of SiNHs with the plasmonic absorption of metallic nanowires (MeNWs) towards enhanced sensitivity and spectral-selective photodetection induced by the local surface plasmon resonance effects.

Formation of Multicolor Nanogels Based on Cationic Polyfluorenes and Poly(methyl vinyl ether-alt-maleic monoethyl ester): Potential Use as pH-Responsive Fluorescent Drug Carriers.

In this study, we employed the copolymer poly(methyl vinyl ether-alt-maleic monoethyl ester) (PMVEMA-Es) and three fluorene-based cationic conjugated polyelectrolytes to develop fluorescent nanoparticles with emission in the blue, green and red spectral regions. The size, Zeta Potential, polydispersity, morphology, time-stability and fluorescent properties of these nanoparticles were characterized, as well as the nature of the interaction between both PMVEMA-Es and fluorescent polyelectrolytes. Because PMVEMA-Es contains a carboxylic acid group in its structure, the effects of pH and ionic strength on the nanoparticles were also evaluated, finding that the size is responsive to pH and ionic strength, largely swelling at physiological pH and returning to their initial size at acidic pHs. Thus, the developed fluorescent nanoparticles can be categorized as pH-sensitive fluorescent nanogels, since they possess the properties of both pH-responsive hydrogels and nanoparticulate systems. Doxorubicin (DOX) was used as a model drug to show the capacity of the blue-emitting nanogels to hold drugs in acidic media and release them at physiological pH, from changes in the fluorescence properties of both nanoparticles and DOX. In addition, preliminary studies by super-resolution confocal microscopy were performed, regarding their potential use as image probes.

Quantification of Phycocyanin in Inland Waters through Remote Measurement of Ratios and Shifts in Reflection Spectral Peaks

This study introduces a semi-empirical algorithm to estimate the extent of the phycocyanin (PC) concentration in eutrophic freshwater bodies; this is achieved by studying the reflectance characteristics of the red and near-red spectral regions, especially the shifting of the peak near 700 nm towards longer wavelengths. Spectral measurements in a darkroom environment over the pure-cultured cyanobacteria Microcystis showed that the shift is proportional to the algal biomass. A similar proportional trend was found from extensive field measurement data. The data also showed that the correlation of the magnitude of the shift with the PC concentration was greater than that with chlorophyll-a. This indicates that the characteristic can be a useful index to quantify cyanobacterial biomass. Based on these observations, a new PC algorithm was proposed that uses the remote sensing reflectance of the peak band around 700 nm and the trough band around 620 nm, and the magnitude of the peak shift near 700 nm. The efficacy of the algorithm was tested with 300 sets of field data, and the results were compared to select algorithms for the PC concentration prediction. The new algorithm performed better than the other algorithms with respect to most error indices, especially the mean relative error, indicating that the algorithm can reduce errors when PC concentrations are low. The algorithm was also applied to a hyperspectral dataset obtained through aerial imaging, in order to predict the spatial distribution of the PC concentration in an approximately 86 km long reach of the Nakdong River.

Robust thermal performance and color purity of samarium based deep red emitting phosphor for near-UV chip-based high-color-rendering

In the progress of LED phosphors, the chemical stability, thermal stability, and color purity was not usually given due attention. However, the most critical problems of WLEDs are the deficit in the red-spectral region, stability, low color-rendering index (CRI) and high correlated color temperature (CCT) limit its efficiency for vivid application. Herein, the Ca3YGa3B4O15:xSm3+ (CYGB:xSm3+) were prepared by a solid-state route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), diffuse reflection spectroscopy (DRS), and as well as photoluminescence (PL) spectra are used to exemplify the resulting samples. The structure and the Sm3+ dopants in the cation-borate phosphors were quantified, signifying the importance at Ca and Y sites. Under ultraviolet radiation-induced bright deep-red emissions with high color-purity up to 97.5%. The energy-migration (EM) between the Sm3+ ion was investigated both empirically and theoretically in the region of Sm3+ contents. Several theoretical-models were employed to simulate the lifetime of Sm3+ at various-concentrations, and the processes were investigated as a forced-electric dipole. The chemical-stability of CY0.95GB:0.05Sm3+ has also been investigated in this work. Interestingly, the CY0.95GB:0.05Sm3+ showed exceptional thermal-quenching resistance of>91.2% intensity at 400 K. The WLED containing CY0.95GB:0.05Sm3+ blended with the BAM:Eu2+ and CYAB:Tb3+ phosphor demonstrated low CCT ≈ 3843 K and high CRI ≈ 91.9. These findings were healthier than the industrial WLED having Y3Al5O12:Ce3+ and blue-LED.

A novel Eu3+-doped ScCaO(BO3) red phosphor for tricolor-composited high color rendering white light

Exploration of novel red emitting phosphors containing Eu3+ ions is an everlasting topic in the field of luminescent materials due to the application requirement of warm white light-emitting diodes. In this work, the Eu3+-doped ScCaO(BO3) phosphors were synthesized though the high temperature solid-state reaction method. The phase purity and detail information on crystal structure were obtained by X-ray diffraction (XRD) and the technology of Rietveld XRD refinement. Scanning electron microscopy (SEM) was applied to check the particle morphology and EDS mapping was taken to analyze element distributions. Optical properties of the phosphors were studied by measuring the steady-state excitation and emission spectra and also the transient luminescence decays. The emission spectra of ScCaO(BO3):Eu3+ majorly consisted of 5D0-7F1, 7F2 and 7F4 transitions, covering the orange (582–605 nm), red (605–635 nm) and deep red (690–720 nm) spectral regions. The doping concentration of Eu3+ ions was optimized to 12% to maximize the optical performance of the red emitting phosphors, whose CIE coordinate and fluorescent lifetime were (0.6458, 0.3537) and 1.516 ms, respectively. The investigation of the thermal quenching behavior of the ScCaO(BO3):0.12Eu3+ phosphor reveals that the emission intensity of Eu3+ at 400 K can maintain 68.98% of that at room temperature due to the existence of the thermal activation energy of 0.258 eV. Using such a red-emitting material, the prototype warm white LED device with the CIE coordinate of (0.3262, 0.3363), color rendering index of 86.1 and correlated color temperature of 5871 K can be obtained by combining with the blue emitting BaMgAl10O17:Eu2+ and green emitting Zn2SiO4:Mn2+ phosphors and coating all three on a near-UV LED chip. All the results demonstrate that the ScCaO(BO3):0.12Eu3+ phosphor can sever as a potential red emitting candidate for near-UV excited warm WLEDs.

Technological aspects of borate glass–ceramics preparation doped with transition metals for optoelectronic applications

Chromium-doped borate glass-ceramics are prepared at different temperatures via bulk crystallization of the borate glass matrix. The temperature influence on the spectral and operational characteristics of the material is observed. Rod-shaped LiAl7B4O17 crystals nucleate in a glassy matrix during two stage heat treatment. Borate glass-ceramics possess luminescence in the 650–800 nm region when excited with “green” light. An increase in the annealing temperature of glass-ceramics lead to several changes: (1) the luminescence quantum yield increase from 13% to 50%, (2) color coordinates of glass-ceramics luminescence shift towards to the red spectral region, (3) hardness and resistance to acid solutions of glass-ceramics increase. XRD experiments are carried out within the direct heating of a glass sample. The results show that the maximum size of nanocrystals was reached at a temperature of 600 °C, which coincided with the maximum of the exothermic region on the DSC curve. Thus, the spectral and operational properties of borate glass-ceramics exceed those of the initial borate glass, which makes borate glass-ceramics doped with chromium ions promising material for creating red and near infra-red emitters .

Seasonal Spectral Separation of Western Snowberry and Wolfwillow in Grasslands with Field Spectroradiometer and Simulated Multispectral Bands

Woody plant encroachment (WPE), the expansion of native and non-native trees and shrubs into grasslands, has led to degradation worldwide. In the Canadian prairies, western snowberry and wolfwillow shrubs are common encroachers, whose cover is currently unknown. As the use of remote sensing in grassland monitoring increases, opportunities to detect and map these woody species are enhanced. Therefore, the purpose of this study is to identify the optimal season for detection of the two shrubs, to determine the sensitive wavelengths and bands that allow for their separation, and to investigate differences in separability potential between a hyperspectral and broadband multispectral approach. We do this by using spring, summer, and fall field-based spectra of both shrubs for the calculation of spectral separability metrics and for the simulation of broadband spectra. Our results show that the summer offers higher discrimination between the two species, especially when using the red and blue spectral regions and to a lesser extent the green region. The fall season fails to provide significant spectral separation along the wavelength spectrum. Moreover, there is no significant difference in the results from the hyperspectral or broadband approach. Nevertheless, cross-validation with satellite imagery is needed to confirm the current results.

Assessment of Polymer Atmospheric Correction Algorithm for Hyperspectral Remote Sensing Imagery over Coastal Waters.

Spaceborne imaging spectroscopy, also called hyperspectral remote sensing, has shown huge potential to improve current water colour retrievals and, thereby, the monitoring of inland and coastal water ecosystems. However, the quality of water colour retrievals strongly depends on successful removal of the atmospheric/surface contributions to the radiance measured by satellite sensors. Atmospheric correction (AC) algorithms are specially designed to handle these effects, but are challenged by the hundreds of narrow spectral bands obtained by hyperspectral sensors. In this paper, we investigate the performance of Polymer AC for hyperspectral remote sensing over coastal waters. Polymer is, in nature, a hyperspectral algorithm that has been mostly applied to multispectral satellite data to date. Polymer was applied to data from the Hyperspectral Imager for the Coastal Ocean (HICO), validated against in situ multispectral (AERONET-OC) and hyperspectral radiometric measurements, and its performance was compared against that of the hyperspectral version of NASA’s standard AC algorithm, L2gen. The match-up analysis demonstrated very good performance of Polymer in the green spectral region. The mean absolute percentage difference across all the visible bands varied between 16% (green spectral region) and 66% (red spectral region). Compared with L2gen, Polymer remote sensing reflectances presented lower uncertainties, greater data coverage, and higher spectral similarity to in situ measurements. These results demonstrate the potential of Polymer to perform AC on hyperspectral satellite data over coastal waters, thus supporting its application in current and future hyperspectral satellite missions.

Si nanopillar arrays as possible electronic device platforms

This paper explores the possible use of silicon nanopillars as electronic devices. The silicon nanopillars studied in this work were fabricated by electron beam lithography and by plasma ion etching of silicon wafers. The electrical and physical properties of these pillars with full width at half maximum ranging from few nanometers to 100 nm and length of few hundreds of nanometer have been investigated by time-resolwed photoluminescence, infrared spectroscopy and current-voltage characteristics. An ultrafast blue luminescence component competing with non-radiative recombination at surface defects was quantified as originating from the no-phonon recombination. This component involved two decay processes with a peak energy at around 500 nm, which have the fast component close to femtosecond time scale. The emission exhibits also a slow component in the red spectral region with a time constant in the nanosecond regime. The nanopillars have been smoothened in an attempt to passivate surface defects. The results are indicative of an increase in the lifetimes-of carriers and an enhancement in the red component of the emission with much slower sates. The presence of ultrafast decay at blue-green spectral region is suggestive of the possibility of using the silicon nanopillars as ultrafast switching devices. Silicon nanopillar arrays can also be an ideal platform in trapping and sensing chemical or biological species using diamond NV centers.

Dominant UV emission and n-type conductivity in manganese doped Zinc Telluride quantum dots

A dominant UV emission at 397 nm and an n-type conductivity in the manganese (Mn) doped Zinc Telluride (ZnTe) quantum dots (QDs) are reported in this article. Energy Dispersive X-ray analysis (EDAX) is used to confirm the composition of the undoped and Mn2+ doped ZnTe QDs. High Resolution Transmission Electron Microscopic (HRTEM) images depict the systematic and homogeneously distributed QDs. Selected Area Electron Diffraction (SAED) patterns exemplify the crystalline nature of the as synthesized QDs. From the X-ray Photoelectron Spectroscopic (XPS) analysis, Mn is found to be present in its divalent state of Mn2+. Tauc plots confirm the blue shift for the Mn2+ doped ZnTe QDs and the energy band gap is found to vary between 3 and 3.3 eV. The photoluminescence spectra in the red spectral region depicts the quenching effect when doped with Mn2+ and this may be attributed to the F-center like defects. The absence of the peak at about 525 nm wavelength (2.369 eV) indicates the suppressed Zn vacancy defects, in both undoped and Mn2+ doped ZnTe QDs. From the van der Pauw method of Hall measurements, Mn2+ doping in an n-type ZnTe QDs is found to increase the mobility and conductivity of the carriers than that is observed in the undoped ZnTe QDs. From the photoluminescence and van der Pauw Hall measurement studies, it can be said that Mn2+ is a worthy dopant for ZnTe QDs and can be used in the fabrication of p-n homo–junction diode.

A new solid solution Bi1.48Eu0.52Pb0·5Sr0·5B2O7 and luminescent properties of the Bi2-xPb0.5Sr0·5B2O7:xEu3+ phosphors

A new solid solution Bi1.48Eu0.52Pb0·5Sr0·5B2O7 was prepared by the high-temperature solid state reaction at 850 °C and its crystal structure was determined by single-crystal XRD analysis with following crystal data: R3¯c, a = 9.0085(2) Å, c = 38.8910(9) Å, V = 2733.26(13) Å3 and Z = 18. It has a layered structure in which alternating [BO3]3- triangles and [(Pb/Sr)O6]10− trigonal prisms are connected via common O vertexes to generate a 2D layer, with [(Bi/Eu)2O]4+ groups located in the six-membered ring channels within the layer. Two 3¯ axis related layers are stacked rhombohedrally along the c-axis to build a unit cell and held together by weak (Bi/Eu)-O bonds. The existence of BO3 groups was confirmed by vibrational spectroscopy, the optical band gap was determined with the UV–vis absorption measurements, and the chemical states of the elements were analyzed by XPS spectroscopy. Furthermore, the Bi2-xPb0.5Sr0·5B2O7:xEu3+ (0.10 ≤ x ≤ 0.50) phosphors were synthesized via the solid-state reaction method and their photoluminescence properties were studied. The emission spectra consist of groups of peaks in the red spectral region due to 5D0→7Fj (j = 0, 1, 2, 3) electronic transitions of Eu3+ ions and the optimal Eu3+ content was found to be x = 0.3. The CIE coordinates of the Bi1.70Eu0.30Pb0·5Sr0·5B2O7 phosphor was obtained to be (0.640, 0.359) and the QE value was equal to 15.41%. Moreover, its synthetic temperature is low. The characteristics make the Bi2-xPb0.5Sr0·5B2O7:xEu3+ (0.10 ≤ x ≤ 0.50) compounds to be promising reddish-orange phosphors for white LEDs.

Photomorphogenesis in the Picocyanobacterium Cyanobium gracile Includes Increased Phycobilisome Abundance Under Blue Light, Phycobilisome Decoupling Under Near Far-Red Light, and Wavelength-Specific Photoprotective Strategies.

Photomorphogenesis is a process by which photosynthetic organisms perceive external light parameters, including light quality (color), and adjust cellular metabolism, growth rates and other parameters, in order to survive in a changing light environment. In this study we comprehensively explored the light color acclimation of Cyanobium gracile, a common cyanobacterium in turbid freshwater shallow lakes, using nine different monochromatic growth lights covering the whole visible spectrum from 435 to 687 nm. According to incident light wavelength, C. gracile cells performed great plasticity in terms of pigment composition, antenna size, and photosystem stoichiometry, to optimize their photosynthetic performance and to redox poise their intersystem electron transport chain. In spite of such compensatory strategies, C. gracile, like other cyanobacteria, uses blue and near far-red light less efficiently than orange or red light, which involves moderate growth rates, reduced cell volumes and lower electron transport rates. Unfavorable light conditions, where neither chlorophyll nor phycobilisomes absorb light sufficiently, are compensated by an enhanced antenna size. Increasing the wavelength of the growth light is accompanied by increasing photosystem II to photosystem I ratios, which involve better light utilization in the red spectral region. This is surprisingly accompanied by a partial excitonic antenna decoupling, which was the highest in the cells grown under 687 nm light. So far, a similar phenomenon is known to be induced only by strong light; here we demonstrate that under certain physiological conditions such decoupling is also possible to be induced by weak light. This suggests that suboptimal photosynthetic performance of the near far-red light grown C. gracile cells is due to a solid redox- and/or signal-imbalance, which leads to the activation of this short-term light acclimation process. Using a variety of photo-biophysical methods, we also demonstrate that under blue wavelengths, excessive light is quenched through orange carotenoid protein mediated non-photochemical quenching, whereas under orange/red wavelengths state transitions are involved in photoprotection.

Spectral Detection Enables Multi-Color Fluorescence Fluctuation Spectroscopy Studies in Living Cells

Fluorescence fluctuation spectroscopy techniques provide a powerful toolbox to quantify transport dynamics and interactions of biomolecules in living cells. Cross-correlation analysis of spectrally well-separated fluctuations allows to investigate hetero-interactions between different biomolecules. This analysis is conventionally limited to two fluorescent species that are excited with one or two laser lines and detected in two non-overlapping spectral channels. However, signaling pathways in biological systems often involve interactions between multiple biomolecules, e.g. formation of ternary or quaternary protein complexes. Here, we implement a methodology to investigate such interactions at the plasma membrane (PM) of living cells, in the context of e.g. viral assembly or receptor-ligand interactions. To this aim, we introduce scanning spectral fluorescence correlation spectroscopy (SSFCS), a combination of scanning FCS with spectrally resolved detection and decomposition, inspired by fluorescence lifetime correlation spectroscopy. We first demonstrate that SSFCS allows cross-talk free cross-correlation analysis on cells expressing spectrally highly overlapping fluorescent proteins (FPs) such as mEGFP and mEYFP at the PM, with a single excitation line. We then verify the performance of SSFCS for the quantification of diffusion dynamics and protein oligomerization (based on molecular brightness analysis) of two protein species tagged with spectrally overlapping FPs. Adding a second laser line, we show the possibility of three- and four-species (cross-) correlation analysis using mApple and mCherry2 as overlapping FP tags in the red spectral region. Using this set of fluorophores, we furthermore extend the recently presented raster spectral image correlation spectroscopy (RSICS) approach to four species, and successfully demonstrate multiplexed RSICS measurements of protein interactions in cellular cytoplasm. Finally, we apply SSFCS and RSICS to investigate the assembly of the Influenza A virus matrix proteins and ternary polymerase complex at the PM and in the nucleus of living cells, respectively.