Yellow-orange Region Research Articles

Tuning the emission of anti-rigidochromic fluorophore by alternating the polymer matrices for advanced data encryption

Anti-rigidochoromic fluorophores with bathochromic emission in rigidifying polymer matrix offer advantages such as high fluorescent contrast, broadly tunable emissions, and versatile stimuli-responsive behaviors. In this work, we systematically investigated the impact of polymer chemical structure on the emission of the anti-rigidochromic fluorophore. By precisely tuning intermolecular polar-π and π-π interactions between the polymer matrix and fluorophore, a range of emission colors could be achieved, spanning from deep blue (450 nm) to the yellow-orange region (600 nm). Notably, the emission of polymer/fluorophore composites can be precisely adjusted over temperature. Leveraging the distinctive features, we showcase advanced fluorescence encryption using the non-emissive polymers as an information carrier and the fluorophore as the decryption key, which efficiently addresses issues of conventional fluorophores such as photo-bleaching and low adhesive force. This work establishes the structure-fluorescence relationship for the anti-rigidochromic system and extends its application for advanced data encryption with a high level of security.

Dicyanorhodanine-Pyrrole Conjugates for Visible Light-Driven Quantitative Photoswitching in Solution and the Solid State.

Small molecule photoswitches capable of toggling between two distinct molecular states in response to light are versatile tools to monitor biological processes, control photochemistry, and design smart materials. In this work, six novel dicyanorhodanine-based pyrrole-containing photoswitches are reported. The molecular design avails both the Z and E isomers from synthesis, where each can be isolated using chromatographic techniques. Inter- and intramolecular hydrogen bonding (H-bonding) interactions available to the E and Z isomers, respectively, uniquely impart thermal stability to each isomer over long time periods. Photoisomerization could be assessed by solution NMR and UV-vis spectroscopic techniques along with complementary ground- and excited-state computational studies, which show good agreement. Quantitative E → Z isomerization occurs upon 523 nm irradiation of the parent compound (where R = H) in solution, whereas Z → E isomerization using 404 nm irradiation offers a photostationary state (PSS) ratio of 84/16 (E/Z). Extending the π-conjugation of the pyrrole unit (where R = p-C6H4-OMe) pushes the maximum absorption to the yellow-orange region of the visible spectrum and allows bidirectional quantitative isomerization with 404 and 595 nm excitation. Comparator molecules have been prepared to report how the presence or absence of H-bonding affects the photoswitching behavior. Finally, studies of the photoswitches in neat films and photoinactive polymer matrices reveal distinctive structural and optical properties of the Z and E isomers and ultimately afford reversible photoswitching to spectrally unique PSSs using visible light sources including the Sun.

The orange light emitting luciferase from the rare Euryopa clarindae adult railroadworm (Coleoptera:Phengodidae): structural/functional and evolutionary relationship with green and red emitting luciferases.

Railroadworms luciferases emit the widest range of bioluminescence colors among beetles, ranging from green to red, being model enzymes to investigate the structure and bioluminescence colors relationships. Only three active railroadworms luciferases from the larval stage have been cloned and investigated: the Phrixothrix hirtus head lanterns red-emitting luciferase (PhRE); the Phrixothrix vivianii lateral lanterns green emitting luciferases (PvGR) and the Phengodes sp. dorsal lanterns yellow-green emitting luciferase (Ph). No activeluciferase emitting in the yellow-orange region, however, has been cloned yet. Here we report the cloning and characterization of the orange emitting luciferase from the adult males of a rare Brazilian Cerrado railroadworm, Euryopa clarindae, and the transcriptional identification of two isozymes from the Amazon forest Mastinomorphus sp. railroadworm. The luciferase of E. clarindae has 548 residues, emits orange bioluminescence (600nm), and displays intermediate kinetic values [KM(luciferin) = 50µM, KM(ATP) ~ 170µM] between those reported for green-emitting lateral lanterns and red emitting head lanterns luciferases. It displays 74-78% identity with the lateral lanterns luciferases of other railroadworms and 70% with the head lantern PhRE luciferase, and 96% with the larval Mastinomorphus sp. Mast-1, suggesting that this larva could be from the Euryopa genus. The phylogenetic analysis and kinetic/functional properties, place this orange-emitting enzyme as an intermediate form between the green-emitting lateral lanterns and red-emitting head lanterns luciferases. Major structural differences that could be associated with bioluminescence color determination are a relatively larger cavity size, and substitutions in the loops 223-235 and 311-316, especially N/C/T311, and their interactions which may help to close the bottom of LBS.

Broadband yellow-orange light generation based on a step-chirped PPMgLN ridge waveguide.

Yellow-orange lights, valuable in photodynamic therapies, spectroscopy, and optogenetics, are limited by the narrow bandwidth and bulky setup via the conventional Raman or optical parametric oscillation processes. Moreover, flatness in the broad-band spectrum is also important for the aforementioned applications with extended functions. In this paper, by carefully designing grating-periods of a step-chirped PPMgLN ridge waveguide for sum frequency generation (SFG), we report a compact broad-band yellow-orange light with bandwidth of 5.6 nm and an un-reported flatness (<1.5 dB). Correspondingly, the optical conversion efficiency is 232.08%/W, which is the best SFG efficiency for PPMgLN at the yellow-orange region, to the best of our knowledge. The results could also be adopted for other broad-band SFG process toward the vis-infrared region in an integrated structure.

Structure and defects-related optical properties of highly (002)-oriented zinc oxide thin films

We report on the highly (002)-oriented ZnO thin films deposited on glass substrates at different substrate temperatures using the recently developed pulsed laser deposition (PLD) facility at our institution. Effects of the substrate temperature on the structural, compositional, morphological, and optical properties of the ZnO thin films are studied. The XRD studies revealed the deposition of high-quality ZnO thin films with preferred hexagonal wurtzite structure along the (002) plane above 200 °C substrate temperatures. An increase in the crystallite size estimated using the Scherrer formula from 9.58 nm to 13.25 nm of the deposited thin films reflects the enhancement of the crystallinity with the increasing substrate temperature. Scanning electron microscope (SEM) micrographs revealed a smooth surface morphology with small grains for the thin film deposited at room temperature. The thin films deposited at high substrate temperatures showed agglomeration of nanoparticles resulting in nano rod-like structures. The optical band gap energy was found to be increased with an increase in the crystallinity of the thin films. In the photoluminescence (PL) spectra; near band edge (NBE) emissions were observed in all of the deposited thin films. The deep-level emissions of ZnO thin films were found to be highly dependent on the substrate temperature during film deposition. The thin films grown at 500 °C showed the visible emission in blue, green, and yellow-orange regions, which corresponded to zinc vacancy (VZn), oxygen vacancy (VO), and oxygen interstitial (Oi) defect levels, respectively. These crystal defects in the deposited ZnO thin films are responsible for the deep level emission linked to the visible emission.

IMPACT OF Mn2+ IONS ON MICRO-STRUCTURAL, LUMINESCENCE PROPERTIES OF ZnS-MoS2 NANOCOMPOSITES FOR OPTOELECTRONICS

Bottom-up hydrothermal synthesis was used to prepare semiconducting natured undoped and Mn2+ doped nanocomposites of ZnS-MoS2. XRD -X-ray diffraction analysis, DRS- diffuse reflection spectroscopy spectrophotometer, FT-IR-Fourier transform infrared spectroscopy, SEM-scanning electron microscopy, and PLphotoluminescence techniques were used to characterize the structural, optical absorption, morphological, IR spectral, and luminescence properties of prepared powder samples. The average crystallite size of prepared nanocomposites ranged between 12 and 20 nm. The FT-IR spectra were used to examine the molecular vibrations and various functional groups contained in the prepared samples. Surface morphology analyses show the presence of spherical-shaped ZnS flakes and hexagonal MoS2 flakes. The energy bandgap decreases as the quantity of Mn2+ doping in the host lattice increases, showing the quantum confinement of prepared samples. The PL data indicates a characteristic luminescence peak in the yellow-orange region at 585 nm.

Morphological and Physiological Responses of Pinus massoniana Seedlings to Different Light Gradients

Light intensity is a critical factor regulating photosynthetic capacity in plants. However, the effects of varying light intensity on morphological and photoprotective mechanisms in Pinus massoniana seedlings have not been explored in depth, especially those in the first seedling growing season. We measured the growth, photosynthetic physiology, biochemistry, and chlorophyll fluorescence of P. massoniana seedlings at four light gradients: 100% relative irradiance (RI, full sunlight), 70% RI, 50% RI, and 20% RI. The seedling height at 70% RI was 9.27% higher than that at 100% RI. However, seedling height was inhibited under low light intensity; at 20% RI, all seedlings died. The decreasing light intensity inhibited ground diameter growth but increased the height-diameter ratio. The secondary needle emergence rate was 53.4% higher at 70% RI than at 100% RI but was only 2% at 50% RI. The chlorophyll and carotenoid contents increased significantly with decreasing light intensity. The increased Chl b and Car contents promoted the photoreceptor potential of the violet (400~420 nm), blue (440~480 nm), and yellow-orange (597~655 nm) regions in leaves. Among the chlorophyll fluorescence parameters, Fv/Fm, Fv′/Fm′, Y(II), qp, and ETR all reached maximum values at 70% RI but were significantly lower at 50% RI than at 100% RI. However, decreasing the light intensity caused a reduction in NPQ. The 70% RI level increased POD and SOD activity and the contents of osmotic regulation substances and slowed MDA accumulation. Seedlings at 70% RI had a higher growth rate, higher photosynthetic activity and potential, and significantly greater stress resistance than the other seedlings. Therefore, appropriate shading measures were beneficial to the cultivation of vigorous seedlings. Furthermore, spectral reflectance indexes were found to be a suitable tool for monitoring the photosynthetic physiological characteristics, stress resistance characteristics, and growth status of P. massoniana seedlings in real time.

Photophysical Properties and Kinetic Studies of 2-Vinylpyridine-Based Cycloplatinated(II) Complexes Containing Various Phosphine Ligands.

A series of cycloplatinated(II) complexes with general formula of [PtMe(Vpy)(PR3)], Vpy = 2-vinylpyridine and PR3 = PPh3 (1a); PPh2Me (1b); PPhMe2 (1c), were synthesized and characterized by means of spectroscopic methods. These cycloplatinated(II) complexes were luminescent at room temperature in the yellow–orange region’s structured bands. The PPhMe2 derivative was the strongest emissive among the complexes, and the complex with PPh3 was the weakest one. Similar to many luminescent cycloplatinated(II) complexes, the emission was mainly localized on the Vpy cyclometalated ligand as the main chromophoric moiety. The present cycloplatinated(II) complexes were oxidatively reacted with MeI to yield the corresponding cycloplatinated(IV) complexes. The kinetic studies of the reaction point out to an SN2 mechanism. The complex with PPhMe2 ligand exhibited the fastest oxidative addition reaction due to the most electron-rich Pt(II) center in its structure, whereas the PPh3 derivative showed the slowest one. Interestingly, for the PPhMe2 analog, the trans isomer was stable and could be isolated as both kinetic and thermodynamic product, while the other two underwent trans to cis isomerization.

Investigation on Physical and Optical of Praseodymium Doped Sodium Aluminium Barium Phosphate Glasses

Sodium aluminium barium phosphate glasses doped with different concentration of Pr2O3 were synthesized by melt quench technique. These glasses were varied concentrations of Pr2O3 at 0, 0.05, 0.10, 0.50, 1.00 and 2.00 mol%. Their physical properties like density (ρ) and refractive index (n) were measured at room temperature. Also, optical absorption and photoluminescence spectra of these glasses have been acquired at room temperature. It was found that the intensity were increase with increasing concentration of Pr2O3. UV-Vis and NIR (250-2500 nm) spectra have been measured for all studied glass samples and discussed. The photoluminescence spectra recorded under 445 nm excitation exhibited the emission bands at 528, 598 and 639 nm corresponding to the emission transitions 3P1 → 3H5, 1D2 → 3H4, and 3P0 → 3F2 respectively. The Judd-Ofelt (JO) parameters Ωλ (λ = 2, 4 and 6) have been calculated to explore the bonding environment around the Pr3+ ions. The CIE chromacity color coordinates (x,y) are calculated from the emission spectra which indicates the located in the yellow-orange region. The prepared glasses are potential candidates for laser applications.

Eu3+ and Cu2+ ions doped ZnS microspheres emission in the yellow–orange region

Photoluminescence (PL) emission properties of hydrothermally synthesized zinc sulfide (ZnS) and doped (Cu2+, Eu3+, Cu2+ and Eu3+) zinc sulfide microspheres were studied. The samples were characterized by X‐ray diffraction, energy‐dispersive X‐ray analysis, field emission scanning electron microscopy, ultraviolet–visible and photoluminescence spectrophotometers. Hydrothermally synthesized ZnS microspheres give a broad emission in the 405–750 nm range. The quenching of broad PL intensity was observed in the Cu2+ ions and Eu3+ ions separately doped ZnS samples. ZnS microspheres codoped with Eu3+ and Cu2+ ions gives narrow and enhanced yellow–orange emission (530–650 nm) that desired for the bioimaging applications and fabrication of white light-emitting sources.

Enhancement of room temperature ferromagnetic behavior of Co-doped ZnO nanoparticles synthesized via sol–gel technique

Zn1−xCoxO (x = 0, 0.001, 0.005, 0.01, 0.02, 0.04, and 0.06) nanoparticles (NPs) were synthesized by sol–gel method. Ingestion of Co2+ ions in the ZnO crystal lattice created defects without disturbing the original crystal structure of ZnO. This is confirmed by the X-ray diffraction (XRD) studies and is also observed in the photoluminescence (PL) emission study where the Co-doped ZnO NPs have shown emissions in the green and yellow-orange regions of visible spectrum. XRD and transmission electron microscopic (TEM) analysis showed reduction in crystallite size from 29 to 14.5 nm and from 51 to 36 nm, respectively, with increase in Co2+ ions concentration. Optical absorption spectroscopic studies (UV-visible spectroscopy) of these samples show significant peak shift towards higher energy (blue shift), which is in accordance with the Kubo’s theory. Magnetic properties were studied using quantum designed vibrating sample magnetometry (VSM), which confirmed that Co-doped ZnO NPs exhibit room temperature ferromagnetism (RTFM) for the samples having high Co concentration. With these notable properties, this study suggests that Co-doped ZnO NPs may be useful in the field of optoelectronic devices and memory-storage devices as well.

Investigations on structural and spectral properties of undoped and Mn2+ doped SrZn2(PO4)2 nanophosphors for light emitting devices

SrZn2(PO4)2 (SZP) and Mn2+ doped SrZn2(PO4)2 (SZP: Mn) nanophosphors are prepared through solution combustion synthesis at a moderate temperature of 823 K. The nanophosphors are characterized by structural and spectral investigations systematically. X-ray diffraction (XRD) analysis confirms the monoclinic phase of SrZn2(PO4)2 with average crystallite size around 60–65 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the samples have shown irregular morphology. The fundamental vibrational modes of different phosphate groups are confirmed by Fourier transform infrared (FT-IR) spectroscopic analysis. Optical absorption spectrum exhibits Mn2+ characteristic bands are in visible region. Electron paramagnetic resonance (EPR) study describes octahedral environment of Mn2+ ions around the ligands in the host. Photoluminescence (PL) spectra show peaks in blue and yellow–orange region. Commission Internationale de l’Eclairage (CIE) and color correlation temperature (CCT) values indicate that SZP and SZP:Mn nanophosphors are potentially good for solid state lightening and white light emitting diodes (WLEDs).

Luminescence properties of near-UV excitable yellow-orange light emitting warm CaSrAl2SiO7:Sm3+ phosphors

Single-phase CaSrAl2SiO7:Sm3+ phosphors were synthesized by traditional high temperature solid state reaction method. Formation of samples and phase analysis were confirmed by X-ray diffraction technique. Morphology was done by field emission scanning electron microscopy and elemental compositions were confirmed by energy dispersive X-ray analysis. Present phosphors have tetragonal crystallography with space group P4¯21m. Average crystallite size was calculated by using Scherrer and Williamson-Hall method. Photoluminescence study of CaSrAl2SiO7:Sm3+ phosphor was investigated. Under different excitation wavelengths, PL spectra consist of four emission bands at 564, 570, 601 and 650 nm. The emission bands located at 564 and 570 nm are associated with the transition 4G5/2 → 6H5/2 while emission bands at 601 and 650 nm are due to 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2, respectively. Intense emission was obtained when phosphor was excited under 404 nm wavelength. Non-radiative energy transfer process involved in concentration quenching, was also discussed. CIE coordinate is found in yellow-orange region, hence CaSrAl2SiO7:Sm3+ phosphors emit yellow-orange light when efficiently excited by near UV (∼400 nm) LED chip. Color purity and CCT of the phosphor were determined; CCT suggests that present phosphor is a good candidate as a warm yellow-orange color emitting phosphor. Effect of different heating rates and different UV exposure time on the TL glow curve of the phosphor was investigated. Activation energies and kinetic parameters for different traps were calculated by using peak shape method. TL emission spectrum was also recorded. Present article explains all the possible mechanisms associated with luminescence process in CaSrAl2SiO7:Sm3+ phosphors.

Up-conversion luminescence of GdVO4:Nd3+/Er3+ and GdVO4:Nd3+/Ho3+ phosphors under 808 nm excitation

In recent years, there exists a tendency in research of up-conversion materials to shift excitation from 980 nm to shorter wavelengths. Here, in order to produce up-conversion luminescence emission of GdVO4-based materials under 808 nm excitation, polycrystalline powders of GdVO4:Er3+/Nd3+ and GdVO4:Ho3+/Nd3+ were successfully prepared by a high-temperature solid-state reaction technique. The prepared powders were highly crystalline with a single-phase zircon-type GdVO4 structure and consisted of micrometer-sized irregular spherical particles (2–6 μm in diameter). In all studied samples, visible up-conversion luminescence was successfully achieved under 808 nm illumination. Near-infrared pumping produced emission bands in the green, yellow-orange and green regions of the visible spectrum. The bands in the green and red regions of GdVO4: Er3+/Nd3+ as well as GdVO4:Ho3+/Nd3+ were, respectively, characteristic of Er3+ and Ho3+ ions. The dominant band originating from the 4G7/2 → 4I11/2 transition in Nd3+ ions was observed around 597 nm in all samples.

Insights on the solvatochromic effects in N-doped yellow-orange emissive carbon dots

We have demonstrated a rapid and facile synthetic method to prepare N-doped Cdots that has excitation independent-emission in yellow-orange region. The Cdots showed solvatochromic behavior in different solvents due to change in solvent polarity illustrating n → π* transition (edge band).

The Autofluorescence Response of Flower Cells from Saintpaulia Ionantha as the Biosensor Reaction to Ozone

Anthocyanin-containing cells from blue petals of flowers of Saintpaulia ionantha Wendl have been considered as models for the fluorescent analysis (by luminescence microscopy including confocal microscopy technique) in the indication damages arisen under the action of various ozone concentrations. Laser-scanning confocal microscopy permitted to observe the changes in images of autofluorescence and the fluorescence spectra of individual cells of petal and multicellular secretory hairs. First alterations were fixed in the emission spectra of some petal cells just after 2.5 h -exposure in O 3 (total dose 0.005 μl/l) – missing of maxima 620-630, 640-650 and 665 nm, peculiar to anthocyanins. Although at the ozone concentrations 0.005 μl/l under luminescence microscope any changes in the fluorescence images were not seen yet. Acute experiments during 25 h-50 h-exposures with O3 (doses 0.05 -0.1 μl/l) led to changes both in common fluorescence images (quenching of the emission in main cells of the petal surface and stalks of the secretory hair) and in the spectral position of maxima at region 620 - 660 nm, peculiar to anthocyanins, that disappeared in main petal cells. The chlorophyll maximum 675-680 nm has seen up to 25 h of the exposure, and disappeared to 50 h of the ozonation. In the secretory hairs, similar picture was registered in some cells of stalk, whereas head of the trichome differencing from main cells fluoresced with maximum 480-500 nm, and here additional emission in yellow-orange region have also seen. Experiments with individual phenols and chlorophyll treated with ozone showed that only anthocyanins in vacuole and chlorophyll in chloroplasts are targets of O 3 even in smallest concentrations. The sensitive cells of flowers have been recommended as possible ozone bioindicators both outdoors and indoors.

Enhanced Power-Conversion-Efficiency of Silicon Solar Cells Via Energy-Down-Shift Using Energy Tuning Effect for Mn Doped Cd0.5Zn0.5s/ZnS Core/Shell Quantum Dots

In recent study, silicon solar cell performance has been greatly progressed due to mature understanding about silicon material properties and fabrication process optimization. However, the power-conversion-efficiency (PCE) of silicon solar cells has increased slowly for last 10 years. In order to overcome the current limitation of the PCE of silicon solar-cells, our group has introduced the silicon-solar-cells implemented with core/shell quantum dots for energy conversion. According to our previous work on enhancing the efficiency of silicon solar cells via energy-down-shift using undoped CdSe/ZnS and Cd0.5Zn0.5S/ZnS core/shell QDs1-3, the Stockes’s shift was relatively small (52 – 127 nm) and that led probably to partial self-reabsorption between core/shell QDs. For that reason, we employed the doping QDs systems in this work in order to increase the Stocks’s shift to be higher than 200 nm, called energy-down-shift using energy-tuning-effect. It is known that Mn2+ doped QDs usually have large Stokes’s shift and that will help to limit the self-quenching and self-reabsorption phenomenon and, hence, increase the quantum yield of QDs4. We investigated the enhanced PCE effect of Mn2+-doped Cd0.5Zn0.5S/ZnS core/shell QD via energy-down-shift using energy-tuning-effect. The Mn2+ doped Cd0.5Zn0.5S/ZnS core/shell QDs layer was deposited on the textured pyramid-like SiNX film of p-type silicon solar-cells, as shown in the schematic view of Fig. 1(a), and it was confirmed that the as-synthesized Mn doped Cd0.5Zn0.5S/ZnS core/shell QDs had a Mn doped Cd0.5Zn0.5S core diameter of 6.83 nm and ZnS shell thickness of 2.40 nm, as shown in Fig. 1(b). It was also confirmed that the Mn2+ doped Cd0.5Zn0.5S/ZnS core/shell QDs, absorbed UV-visible region (250–450 nm in wavelength) and emitted yellow-orange visible region (583 nm in wavelength). For p−type silicon solar−cells coated with the QDs layer, in particular, it was observed that the p-type silicon solar-cells coated with 0.064M Mn2+ doped Cd0.5Zn0.5S/ZnS core/shell QDs demonstrated better photovoltaic performance. The JSC increased abruptly from 35.34 to 36.76 mA/cm2 at 0.3-wt% QDs concentration, and which was a 4.02% increase compared to the reference without the QDs layer. Finally, the PCE of 0.55 % in the solar-cell coated with Mn2+ doped QDs layer were achieved at the 0.3-wt% of core–shell QDs doped with 0.064 M, compared with those of solar-cells with uncoated QDs layers. These results indicate that the coating of Mn doped Cd0.5Zn0.5S/ZnS core/shell QDs on the SiNX film textured surface for p−type silicon solar−cells affect JSCdue to the energy−down−shift using energy-tuning-effect of the QDs. * This work was financially supported by the Brain Korea 21 plus Project in 2016, Korea. Reference [1] Baek, S W. et al., Journal of Materials Chemistry A2014. [2] Baek, S W. et al., Phys. Chem. Chem. Phys.2014, 16, 18205-18210. [3] Baek, S. W.; Shim, J. H.; Seung, H. M.; Lee, G. S.; Hong, J. P.; Lee, K. S.; Park, J. G. Nanoscale 2014. [4]. Zeng, R.; Rutherford, M.; Xie, R.; Zou, B.; Peng, X. Chem. Mater. 2010, (22), 2107-2113. Figure 1

Luminescence properties of the Ca-alpha-sialon:Eu solid solution

The Ca,Eu-α-sialon powders with the mixed solid solution composition have been manufactured via the solid-state reaction process in flowing nitrogen in a graphite furnace at a relatively low temperature of 1650°C without an external overpressure. XRD data with Rielveld refinement and XPS measurements were used for characterization of the lattice constants and the surface chemical composition. The monophase Ca-Eu-α-sialon was obtained with the nominal composition of Eu0.048Ca0.702Si7.75Al2.25O0.75N15.25. The highest emission intensity in a yellow-orange region at 590nm and quantum efficiency of 66% was found for this pure Ca,Eu-α-sialon. Estimation of m,n values from the lattice constant and EDS results showed a small deviation from the nominal composition of designed α-sialon. XPS results demonstrated significant changes of the chemical composition in the oxidized surface of phosphor particles. Possible reasons of emission redshift and relationship between the actual solid solution composition and luminescence properties are discussed in terms of simultaneous presence of Eu2+ and Eu3+ ions in the sialon crystal lattice and residual oxynitride glass.

Optical and spectral analysis of Pr3+ doped lithium zinc fluoro telluro phosphate glasses

Optical and spectroscopic characteristics of Pr3+ doped lithium zinc fluoro telluro phosphate glasses synthesised via melt quench method for 1.3 μm emission are investigated. The thermal stability of LZTP glass is examined from DSC profile. A prominent emission at 604 nm assigned to (1D2→3H4) on exciting with λexci = 442 nm and a broad NIR emission band at 1.35μm (1G4→3H5) on pumping at 514.5 nm (Ar+ laser) for Pr3+: LZTP glasses are observed. At lower concentrations of Pr3+, emission intensity found to increase while at higher concentrations, a sudden fall in luminescence intensity has been noticed in Visible and NIR regions due to concentration quenching. The influence of Pr3+ ion concentration on fluorescence quenching due to interaction with OH group, multiphonon and energy transfer relaxation mechanisms. Therefore, cross-relaxation channels responsible for non-radiative energy transfer has been realized from the energy level diagram and emission decay curves. From emission spectra CIE chromaticity coordinates were located in the yellow-orange region. Based on the emission properties, Pr3+doped glasses can be used as fiber amplifiers operating in second window telecommunication.

A series of color tunable yellow–orange–red-emitting SrWO4:RE (Sm3+, Eu3+–Sm3+) phosphor for near ultraviolet and blue light-based warm white light emitting diodes

A series of wide-range-tunable light emissive SrWO4:Sm3+, SrWO4:Sm3+,Eu3+ phosphors were synthesized via the simple co-precipitation method. The charge compensation can greatly improve SrWO4: Sm3+ phosphors luminous intensity. The critical distance, ηT and energy transfer mechanism of SrWO4:0.01Sm3+,0.12Eu3+ were studied. These obtained phosphors exhibit a high luminous efficiency, purity and lower color temperature of the comfortable warm white LEDs. Hues varying have been generated by appropriately tuning the Sm3+ ions concentration, excitation wavelength or Sm3+, Eu3+ co-doping, which have the color tunable wide gamut light covering the yellow–green, greenish-yellow, yellow, yellow orange, orange, reddish orange and red chromaticity region. In particular, SrWO4:0.01Sm3+,0.12Eu3+ phosphors excited at 404 and 480 nm have higher color saturation than commercially available Y2O2S:Eu3+ red phosphor. These phosphors can be excited efficiently using commercial ultraviolet, blue laser diodes and LEDs, and can be used for developing new color light sources, fluorescent display devices, ultraviolet-sensors and tunable visible lasers.