Blue-green Light Research Articles

Impact of led lighting color on productive and behavioral characteristics of the broiler chickens

The present study was conducted to investigate the effect of color (white and blue-green) of LED lighting on the productive, carcass and behavior traits of Cobb broiler chickens. Total of 200 one- day-old unsexed chicks were used, and divided into two pens/groups (100 birds of each with 25 birds of each replicate), at stocking density of 8.7 bird/ square meters. First pen used for LED white color and second pen for LED blue- green mix color light. The results showed that the birds exposed to blue-green light had significant higher (P≤0.01) BW, DBWG and FC values of the whole experimental period compared to those exposed to white color. However, the light color had no significant effect on FCR and MR measurements with average values 1.44 and 0.50%, respectively. The birds exposed to blue-green light had significant higher pre-slaughter live BW and carcass weights (P≤0.01) compared to those exposed to white color. The birds exposed to blue-green light had higher insignificant dressing percentage compared to those exposed to white color. The weekly behavior results showed highly significant differences (P≤0.01) among weeks for aggressiveness and immobility activities, while it being insignificant for pecking activity. The correlation value between immobility and five-week BW of birds reared under blue-green light was the only significant value (0.42) among all studied values. In conclusion, the results indicated that Cobb broilers were calmer under blue-green light compared to those reared under white light, which contributed in more better performance traits.

An unexpected hydratase synthesizes the green light-absorbing pigment fucoxanthin.

The ketocarotenoid fucoxanthin and its derivatives can absorb blue-green light enriched in marine environments. Fucoxanthin is widely adopted by phytoplankton species as a main light-harvesting pigment, in contrast to land plants that primarily employ chlorophylls. Despite its supreme abundance in the oceans, the last steps of fucoxanthin biosynthesis have remained elusive. Here, we identified the carotenoid isomerase-like protein CRTISO5 as the diatom fucoxanthin synthase that is related to the carotenoid cis-trans isomerase CRTISO from land plants but harbors unexpected enzymatic activity. A crtiso5 knockout mutant in the model diatom Phaeodactylum tricornutum completely lacked fucoxanthin and accumulated the acetylenic carotenoid phaneroxanthin. Recombinant CRTISO5 converted phaneroxanthin into fucoxanthin in vitro by hydrating its carbon-carbon triple bond, instead of functioning as an isomerase. Molecular docking and mutational analyses revealed residues essential for this activity. Furthermore, a photophysiological characterization of the crtiso5 mutant revealed a major structural and functional role of fucoxanthin in photosynthetic pigment-protein complexes of diatoms. As CRTISO5 hydrates an internal alkyne physiologically, the enzyme has unique potential for biocatalytic applications. The discovery of CRTISO5 illustrates how neofunctionalization leads to major diversification events in evolution of photosynthetic mechanisms and the prominent brown coloration of most marine photosynthetic eukaryotes.

Hyaluronic acid-poly(lactic-co-glycolic acid) nanoparticles with a ruthenium photosensitizer cargo for photokilling of oral cancer cells

• Enhanced photodynamic effect by Ru(II) complex through both Type I and II mechanisms. • Synthesis of Ru(II) complex with 2,2’-biimidazole for PDT of oral cancer. • Ru(II) complex encapsulation in HA-PLGA NPs for improved solubility and selectivity. • High intracellular uptake of Ru(II) complex mediated by HA targeting of CD44. • Preferential accumulation of Ru(II) complex in the mitochondria. Photodynamic therapy (PDT), a combination of light, molecular oxygen and a photosensitizing dye, has gained attention as a promising technique to treat various types of cancers. Among all the photosensitizers reported so far, ruthenium(II) polypyridyl complexes exhibit unique photophysical and photobiological features owing to their photostability, μs triplet excited states, and ability to undergo both ‘type I’ and ‘type II’ reactions in their photodynamic action. We report the synthesis of a novel Ru(II) complex containing one 2,2'-biimidazole (bim) and two tetramethylphenanthroline (tmp) ligands that sensitizes the simultaneous production of superoxide anion (O 2 • - ) and singlet oxygen ( 1 O 2 ) upon irradiation with blue-green light. To improve its solubility and bioavailability, a zero-order degradation-controlled release formulation based on self-assembled hyaluronic acid (HA)–poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) was prepared for its topical application in oral cancer cells (TR146 cell line). These NPs (152 nm diameter) showed 70% Ru-complex encapsulation efficiency, high physiological stability, low polydispersity index (0.12), and a sensitizer release enhanced by the hyaluronidase enzyme overexpressed in many cancer cells. Both the free complex and its nanocarrier are internalized by the TR146 cells, displaying >90% in vitro cytotoxicity under 470 nm activation (50 J cm -2 ), highlighting their potential as PDT agents. The Ru(II) complex loaded nanocarrier developed in this study can be potentially effective in the treatment of oral cancers.

Light-induced infrared difference spectroscopy on three different forms of orange carotenoid protein: focus on carotenoid vibrations.

Orange carotenoid protein (OCP) is a photoactive carotenoprotein involved in photoprotection of cyanobacteria, which uses a keto-catorenoid as a chromophore. When it absorbs blue-green light, it converts from an inactive OCPO orange form to an activated OCPR red form, the latter being able to bind the light-harvesting complexes facilitating thermal dissipation of the excess of absorbed light energy. Several research groups have focused their attention on the photoactivation mechanism, characterized by several steps, involving both carotenoid photophysics and protein conformational changes. Among the used techniques, time-resolved IR spectroscopy have the advantage of providing simultaneously information on both the chromophore and the protein, giving thereby the possibility to explore links between carotenoid dynamics and protein dynamics, leading to a better understanding of the mechanism. However, an appropriate interpretation of data requires previous assignment of marker IR bands, for both the carotenoid and the protein. To date, some assignments have concerned specific α-helices of the OCP backbone, but no specific marker band for the carotenoid was identified on solid ground. This paper provides evidence for the assignment of putative marker bands for three carotenoids bound in three different OCPs: 3'-hydroxyechineone (3'-hECN), echinenone (ECN), canthaxanthin (CAN). Light-induced FTIR difference spectra were recorded in H2O and D2O and compared with spectra of isolated carotenoids. The use of DFT calculations allowed to propose a description for the vibrations responsible of several IR bands. Interestingly, most bands are located at the same wavenumber for the three kinds of OCPs suggesting that the conformation of the three carotenoids is the same in the red and in the orange form. These results are discussed in the framework of recent time-resolved IR studies on OCP.

Interstitial Zinc Boosted Light Tunability, Afterglow, and Ultrabright White Emission in Zinc Germanate (Zn2GeO4)

To reduce the burden of solid-state lighting and phosphor-converted light-emitting diode technologies on rare earth (RE) and avoid their potential supply risks, we have developed a RE-free Zn2GeO4 (ZGeO) microcrystalline phosphor. It was synthesized by a simple and scalable solid-state reaction of ZnO and GeO2 at 1200 °C. High-temperature synthesized ZGeO demonstrated color tunable emission from bluish-white to green on changing the excitation wavelength from 265 to 335 nm with a photoluminescence quantum yield of 42 and 9%, respectively. They could also convert highly energetic X-ray to bluish-green light emission. First-principles calculations showed that bluish-white and green light emissions are linked to zinc interstitials present, respectively, in zinc (Zni2) and zinc–germanium rings (Zni1). These defects generated in large numbers via high-temperature annealing along with antisites boosted the generation of trapping centers leading to dual persistent luminescence (PerL) of white and green light for more than 60 min as well as exhibited radioluminescence. Luminescent ink based on ZGeO was fabricated and successfully tested for anticounterfeiting applications. An extra effort has been vested on making this solid-state processed ZGeO dispersible in water-soluble deep eutectic solvent which could be a game changer for its marketability. This material has great potential to become an efficient RE and dopant-free phosphor synthesized by a simple, scalable, and cost-efficient route for applications in solid-state lighting, display, and anticounterfeiting, having multifunctionalities such as PerL, tunability, and RL.

Membrane Targeted Azobenzene Drives Optical Modulation of Bacterial Membrane Potential.

Recent studies have shown that bacterial membrane potential is dynamic and plays signaling roles. Yet, little is still known about the mechanisms of membrane potential dynamics regulation-owing to a scarcity of appropriate research tools. Optical modulation of bacterial membrane potential could fill this gap and provide a new approach for studying and controlling bacterial physiology and electrical signaling. Here, the authors show that a membrane-targeted azobenzene (Ziapin2) can be used to photo-modulate the membrane potential in cells of the Gram-positive bacterium Bacillus subtilis. It is found that upon exposure to blue-green light (λ=470nm), isomerization of Ziapin2 in the bacteria membrane induces hyperpolarization of the potential. To investigate the origin of this phenomenon, ion-channel-deletion strains and ion channel blockers are examined. The authors found that in presence of the chloride channel blocker idanyloxyacetic acid-94 (IAA-94) or in absence of KtrAB potassium transporter, the hyperpolarization response is attenuated. These results reveal that the Ziapin2 isomerization can induce ion channel opening in the bacterial membrane and suggest that Ziapin2 can be used for studying and controlling bacterial electrical signaling. This new optical tool could contribute to better understand various microbial phenomena, such as biofilm electric signaling and antimicrobial resistance.

Structure and luminescence properties of Cu+ doped glasses prepared by ion exchange

Doped Cu+ glass was prepared by ion exchange method. It was found that the accumulation zone of copper ions would be formed on the glass surface during the process of ion exchange, and there was an extreme point of copper ion distribution concentration about 10 µm inside the glass surface after ion exchange. The exchange depth of copper ions in the sample increased with the increase of ion exchange time. At low ion exchange temperatures, the Cu elements exchanged into the vitreous body exists in the form of Cu+ and Cu2+. With the exchange of Cu+ into the glass, the degree of polymerization of the glasses continued to increase. By raising the ion exchange temperature, a large number of spherical Cu2O grains formed on the surface of the sample, continuing to raise the temperature, these spherical grains agglomerated and adhered to form lamellae structure, mainly composed of oxides of Cu2O and CuO. The PL spectra showed that the ion-exchanged glass exhibited broadband blue-green emission light with a central wavelength of 468 nm and half-height width of 154 nm under 290 nm excitation. The luminescence intensity appeared to increase firstly and then decrease with increasing the ion exchange time. Dispersed spherical Cu2O grains were generated on the surface of the sample exchanged at 410 °C for 16 h. Co-composite luminescence of the spherical Cu2O semiconductor and the Cu+ doped in the glass effectively increased the luminescence intensity of the samples. In addition, the samples showed a favorable thermal stability of luminescence.

Aqueous degradation and atomic layer deposition (ALD) stabilization of BaAl2O4: Eu2+, Dy3+ long afterglow phosphors

This paper presents the aqueous degradation mechanisms of BaAl2O4:Eu2+, Dy3+ phosphors and demonstrates an ability to prevent degradation via Al2O3 nano encapsulation of powders by atomic layer deposition (ALD) technique. Phosphor powder is synthesized from the solid-state reaction method. The aqueous degradation of this phosphor is systematically studied. This phosphor is found to hydrolyze and degrade within just 30 min of exposure in water. The degradation of BaAl2O4 host lattice directly affects the blue-green light emission at 497 nm, producing blue- and red-emissions that are peaked at 429 nm and 687 nm, respectively. Hydrated and structural decomposed BaAl2O4 reveals a continuous change in the phase assemblage over 30 days of immersion. To prevent this rapid degradation, use of a protective nanocoating was investigated. 10 nm Al2O3 coatings were applied to the surface of the phosphor powder via ALD. ALD coated BaAl2O4:Eu2+,Dy3+ phosphor retains its phosphorescence for at least 7 days of water exposure. Successful encapsulation of such phosphor particles will make them possible to use in aqueous applications or store in long-term humid environments.

An efficient blue-excitable broadband Y3ScAl4O12:Ce3+ garnet phosphor for WLEDs.

Most commercial phosphor-converted white light-emitting diodes (pc-WLEDs) are manufactured with blue LED chips and yellow-emitting Y3Al5O12:Ce3+ (YAG:Ce3+) garnet phosphor, but the lack of blue-green light in the spectrum results in a low color rendering index (CRI). In this paper, we synthesized Y3ScAl4O12:Ce3+ (YSAG:Ce3+) by replacing Al3+ in YAG:Ce3+ with Sc3+. The introduction of Sc3+ with a larger ionic radius through a cation substitution strategy causes lattice expansion, elongation of the Y-O bond, and ultimately a decrease in Ce3+ 5d level crystal field splitting. As a consequence, the emission spectrum undergoes a blue-shift of 10 nm. Furthermore, the YSAG:Ce3+ phosphor exhibits good thermal stability, and its emission intensity at 423 K is about 58% of that at 303 K. Moreover, the analysis of Eu3+ emission spectra demonstrates that the introduction of Sc3+ resulted in a slight reduction of the dodecahedral lattice symmetry. YSAG:Ce3+ effectively compensates for the lack of the blue-green region, and WLEDs with high color rendering index (90.1), low color temperature (4566 K) and high luminous efficiency (133.59 lm W-1) were prepared using the combination of YSAG:0.08Ce3+, CaAlSiN3:Eu2+ and 450 nm blue chips. These findings indicate that YSAG:Ce3+ garnet phosphor has potential to be used in high quality WLEDs.

Blue-Green (~480 nm) versus Blue (~460 nm) Light for Newborn Phototherapy—Safety Considerations

We have previously shown that the phototherapy of hyperbilirubinemic neonates using blue-green LED light with a peak wavelength of ~478 nm is 31% more efficient for removing unconjugated bilirubin from circulation than blue LED light with a peak wavelength of ~452 nm. Based on these results, we recommended that the phototherapy of hyperbilirubinemic newborns be practiced with light of ~480 nm. Aim: Identify and discuss the most prominent potential changes that have been observed in the health effects of phototherapy using either blue fluorescent- or blue LED light and speculate on the expected effects of changing to blue-green LED light phototherapy. Search the phototherapy literature using the terms neonate, hyperbilirubinemia, and phototherapy in the PubMed and Embase databases. Transitioning from blue fluorescent light to blue-green LED light will expose neonates to less light in the 400-450 nm spectral range, potentially leading to less photo-oxidation and geno-/cytotoxicity, reduced risk of cancer, and decreased mortality in extremely low-birthweight neonates. The riboflavin level may decline, and the increased production and retention of bronze pigments may occur in predisposed neonates due to enhanced lumirubin formation. The production of pre-inflammatory cytokines may rise. Hemodynamic responses and transepidermal water loss are less likely to occur. The risk of hyperthermia may decrease with the use of blue-green LED light and the risk of hypothermia may increase. Parent-neonate attachment and breastfeeding will be positively affected because of the shortened duration of phototherapy. The latter may also lead to a significant reduction in the cost of phototherapy procedures as well as the hospitalization process.

Diboraanthracene-Doped Polymer Systems for Colour-Tuneable Room-Temperature Organic Afterglow.

Organic ultralong room temperature phosphorescence (RTP), or organic afterglow, is a unique phenomenon, gaining widespread attention due to its far-reaching application potential and fundamental interest. Here, two laterally expanded 9,10-dimesityl-dihydro-9,10-diboraanthracene (DBA) derivatives are demonstrated as excellent afterglow materials for red and blue-green light emission, which is traced back to persistent thermally activated delayed fluorescence and RTP. The lateral substitution of polycyclic DBA scaffold, together with weak transversal electron-donating mesityl groups, ensures the optimal molecular properties for (reverse) intersystem crossing and long-lived triplet states in a rigid poly(methyl methacrylate) matrix. The achieved afterglow emission quantum yields of up to 3 % and 15 %, afterglow lifetimes up to 0.8 s and 3.2 s and afterglow durations up to 5 s and 25 s (for red and blue-green emitters, respectively) are attributed to the properties of single molecules.

Recognition of Underwater Materials of Bionic and Natural Fishes Based on Blue-Green Light Reflection.

Thanks to the advantages of low disturbance, good concealment and high mobility, bionic fishes have been developed by many countries as equipment for underwater observation and data collection. However, differentiating between true and bionic fishes has become a challenging task. Commonly used acoustic and optical technologies have difficulty in differentiating bionic fishes from real ones due to their high similarity in shape, size, and camouflage ability. To solve this problem, this paper proposes a novel idea for bionic fish recognition based on blue-green light reflection, which is a powerful observation technique for underwater object detection. Blue-green light has good penetration under water and thus can be used as a signal carrier to recognize bionic fishes of different surface materials. Three types of surface materials representing bionic fishes, namely titanium alloy, carbon fiber, and nylon, are investigated in this paper. We collected 1620 groups of blue-green light reflection data of these three kinds of materials and for two real fishes. Following this, three machine learning algorithms were utilized for recognition among them. The recognition accuracy can reach up to about 92.22%, which demonstrates the satisfactory performance of our method. To the best of our knowledge, this is the first work to investigate bionic fish recognition from the perspective of surface material difference using blue-green light reflection.

A phenomenon thermal denaturation of Copper(I) complexes with blue-to-red emission transition for white color displays

Here we report two luminescent copper complexes with different structures and luminescent properties, the blue-green [CuI(dmpyHS) (PPh3)2]⸱CH3CN (CuPy-PPh3) and the red [Cu6(dmpyS)6]⸱H2O (CuPy). When the blue-green light (CuPy-PPh3) is heated to above 147 °C, it loses the phosphine-containing ligand, PPh3, and turns into CuPy and instead emits red light. Many luminescent complexes show the change of luminescence properties when the temperature is lower than room temperature, while the luminescence change of CuPy-PPh3 occurs during the heating process above room temperature. Even more interesting, the luminescence wavelength transition span is large, from blue-green light emission at 490 nm to red light at 676 nm. The luminescence of the two copper complexes covers the three primary colors of red, green and blue required for the formation of white light emitting diodes WLEDs, which has potential in the development of non-rare earth phosphor white color displays. The integration of CuPy-PPh3 and CuPy on a 395 nm near-ultraviolet chip can assemble WLEDs with good white light properties, which provides a new way for the construction of rare earth-free phosphor WLEDs. The synthesis of the two luminescent copper complexes is simple and environmentally friendly. Even though the structures of two copper complexes have been reported, the synthesis methods are different from those in the related literature and the luminescence properties of these complexes have never been described previously. The red emission copper complex CuPy is obtained by the thermal conversion of the blue-green emission copper complex CuPy-PPh3, which is a new phenomenon discovered for the first time in this work.

Studies on Rare-Earth Co-Doped: Calcium Tungstate Nano-Crystals

Abstract: We report the synthesis of co-doped Calcium tungstate (CaWO4) nano-crystals with Gadolinium (Gd) and Neodymium (Nd) rare earth ions by hydrothermal synthesis method for the first time. The synthesized nano-crystals were characterized by Xray diffraction (XRD) with energy dispersive analysis of the X-rays (EDAX) and Field-emission scanning electron microscopy (FESEM), and photo-luminescence excitation studies. The phase of the nano-crystals under study was identified by X-ray diffraction (XRD). The Field-Emission Scanning Electron Microscope (FESEM) image shows that the synthesized nano-crystals are in the size range of 51nm – 80nm. The presence of Gd and Nd rare earth ions in the GD-Nd co-doped CaWO4 nano-crystals was confirmed by the energy dispersive analysis of the X-rays (EDAX). The photoluminescence properties of the Gd-Nd co-doped CaWO4 nano-crystals were compared with the undoped CaWO4 nano-crystals and are reported. The synthesized nano-crystals exhibit emissions at (i) 369nm, 392nm, 435nm and 477nm for an excitation wavelength of 280 nm and (ii) 540nm and 669nm for an excitation wavelength of 490nm. The emission wavelengths clearly indicate the blue light and green light generation, which is significant for developing luminescent materials of tungstate systems.

Single-Mode-Tuned Tricolor Emissions of Upconversion/Afterglow Hybrids for Anticounterfeiting Applications.

This work presents a highly secure anticounterfeiting strategy based on upconversion/afterglow hybrids with tricolor emissions tuned by a single 975 nm laser. The hybrids are composed of NaYF4:Yb/Tm and NaYF4:Yb/Er microrods and CaS:Eu2+ afterglow phosphors. Under 975 nm excitation, the hybrids exhibit multicolor emissions from green to white by adjusting laser power and then emit red afterglow light when the 975 nm laser is off. Under synergistic excitation of the blue-green light emitted by Tm/Er microrods, the red afterglow emission not only has a strong initial intensity but also lasts for 3 s. Obvious trichromatic changes from green to white to red can be observed by the naked eye. A pattern printed by the hybrid ink exhibits tricolor emissions by laser adjustment and switch. This proves that upconversion/afterglow hybrids are an excellent candidate for anticounterfeiting applications with high-level security but a simple recognition method.

Proton-transporting heliorhodopsins from marine giant viruses.

Rhodopsins convert light into signals and energy in animals and microbes. Heliorhodopsins (HeRs), a recently discovered new rhodopsin family, are widely present in archaea, bacteria, unicellular eukaryotes, and giant viruses, but their function remains unknown. Here, we report that a viral HeR from Emiliania huxleyi virus 202 (V2HeR3) is a light-activated proton transporter. V2HeR3 absorbs blue-green light, and the active intermediate contains the deprotonated retinal Schiff base. Site-directed mutagenesis study revealed that E191 in TM6 constitutes the gate together with the retinal Schiff base. E205 and E215 form a PAG of the Schiff base, and mutations at these positions converted the protein into an outward proton pump. Three environmental viral HeRs from the same group as well as a more distantly related HeR exhibited similar proton-transport activity, indicating that HeR functions might be diverse similarly to type-1 microbial rhodopsins. Some strains of E. huxleyi contain one HeR that is related to the viral HeRs, while its viruses EhV-201 and EhV-202 contain two and three HeRs, respectively. Except for V2HeR3 from EhV-202, none of these proteins exhibit ion transport activity. Thus, when expressed in the E. huxleyi cell membranes, only V2HeR3 has the potential to depolarize the host cells by light, possibly to overcome the host defense mechanisms or to prevent superinfection. The neuronal activity generated by V2HeR3 suggests that it can potentially be used as an optogenetic tool, similarly to type-1 microbial rhodopsins.

Study about photoinduction-based technology for trapping small brown planthopper

To provide a theory to guide the selection of the illumination parameters of light emitting diode (LED)-based light sources used for trapping Laodelphax striatellus, we used LED light sources and devices built in-house to detect L. striatellus phototactic behavior. Through phototaxis screening experiments of different light sources and the comparative experimental method, we analyzed the response patterns of L. striatellus to wavelength, light intensity, layout, flash frequency of monochromatic light sources, as well as combined color light sources, and discussed the mechanisms of the phototactic behavior of L. striatellus under different light sources. The results of the monochromatic light experiment showed that the trapping rate of the L. striatellus to the linear blue light source of 460 nm was the highest and was also significantly affected by the light intensity. The results of the experiments with the combined color light sources showed that compared with the linear 460 nm blue light source, the trapping rate of the L. striatellus was significantly improved by the polychromatic light, and the blue–green light led to the best improvement, reaching 1.5 times that of the trapping rate in the case of monochromatic light sources. The wavelength composition, light intensity, shape, and flash frequency of the light source used in this study can provide a theoretical basis for the development of LED-based light traps specifically for L. striatellus.

Underwater wireless optical communications links: perspectives, challenges and recent trends

AbstractUnderwater wireless optical communication (UOWC) systems have lately garnered a significant amount of attention for both academic purposes and trial applications. Although the idea is not new, the fact that seawater has a smaller window of absorption for blue-green light has reawakened interest in it, and it has grown an essential attraction because of its high bandwidth, it can cover a wide variety of underwater activities as compared to radio frequency and acoustic technologies. To monitor pollution, maintain oil pipelines, monitor climate change, conduct offshore investigations, and conduct oceanography research, the wireless transmission of information underwater technology is of importance to the military, industrial, and scientific organizations all around the world. The use of wavelengths of visible light to transmit secure data across point-to-point connections in underwater optical wireless communication (UOWC) compares well with the usage of free-space optical (FSO) communications. However, UWOC systems also have a huge amount of absorption and scattering introduced by the aquatic channels. Different from standard terrestrial free-space optical communication, many unique system design strategies have been investigated in recent years to solve these technological issues. This article presents a vision as well as various obstacles in the domain of underwater optical wireless communication, a detailed overview, and comparison of underwater communications techniques (UOWC) links, basic modulation technique techniques, and c pursuits on UWOC.

Enhanced blue and broadband near-infrared emission of Pr3+/Yb3+ co-doped PbF2 single crystal

High quality Pr3+ single-doped PbF2 and Pr3+/Yb3+ co-doped PbF2 single crystals were grown by temperature gradient technique (TGT). By co-doping Yb3+ ion as Pr3+ ions sensitizer, the visible light emission can be regulated and the largest luminescence branching ratio can be switched from red-orange to blue-green light. Besides, when Pr3+ ions doping concentration is as low as possible, the blue light self-absorption effect can be weakened, which is beneficial to high-efficiency blue laser output. Moreover, the broad band emission around 1.3 μm from 1G4 energy level can be observed in the Pr3+/Yb3+:PbF2 crystal with the low maximum phonon energy for the first time. Absorption, emission spectra and luminescence mechanism are well analyzed by the energy transfer process and J-O theory. The laser upper energy level lifetime of Pr3+ ions has a great increase by Yb3+ ion effect. These advantageous spectroscopic characteristics show that the Pr3+/Yb3+:PbF2 crystal might be potential laser gain materials for blue-green and ∼1.3 μm near-IR laser operation.

Liquid crystal behaviors of micron and submicron-sized black phosphorus nanosheets

In this study, liquid crystal behaviors of black phosphorus (BP) nanosheets were investigated. A birefringence of approximately 10−4 was achieved for BP owing to its anisotropy, compared to that of 10−5 for graphene oxide. The submicron-sized BP nanosheets (S-BPNS) showed larger birefringence than the micron-sized BP nanosheets (M-BPNS) in blue–green light. The birefringence of both types increased with the incident wavelength; however, that of the S-BPNS remained a constant of approximately 3.8 × 10−4 near 672 nm, whereas that of the M-BPNS reached 4.8 × 10−4 before 753 nm. This inversion in red–yellow light was caused by the layer-dependent bandgap of BP. The anisotropy and tunable bandgap endow BP unique two-dimensional liquid crystal behaviors.