Blue Light Excitation Research Articles

On the luminance saturation of phosphor-in-glass (PiG) films for blue-laser-driven white lighting: Effects of the phosphor content and the film thickness

To investigate the luminance saturation in high-power blue-laser-driven solid state lighting, the Y3Al5O12: Ce (YAG)-based PiG films was co-fired with a high thermally conductive sapphire substrate. When the PtG ratio or the thickness of the PiG film increases, the luminance saturation becomes worse and both of the luminous flux and luminous efficacy decrease. With an additional sapphire substrate coated with an anti-reflection layer on one side and a blue-pass filter on another side attached to the PiG film, the film shows an improvement in luminous flux and efficacy, and produces the white light with a luminous flux of 1709 lm, a luminous efficacy of 211 lm W−1 and a correlated color temperature of 6602 K under the maximum (10.3 W mm−2) blue laser light excitation. It indicates that the PiG film could be applied in high power laser-driven solid state lighting when its microstructure is carefully tailored.

Synthesis and luminescence enhancement of Eu3+/Sm3+ co-doped Ca9Bi(VO4)7 phosphor for white-light-emitting diodes

A series of Ca9Bi(VO4)7:Eu3+ and Ca9Bi(VO4)7:Eu3+, Sm3+ red-emitting phosphors were prepared via a citric acid-assisted sol combustion method. X-Ray diffraction profiles illustrated that all the samples were well matched to the rhombohedral crystal structure of pure Ca9Bi(VO4)7 phase with the R3c space group. The excitation spectra showed two effective excitation peaks, which are located near-ultraviolet light (393 nm) and blue light (464 nm) respectively. It can be concluded from the emission spectrum that the strongest emission peak was located at 618 nm at the excitation of 464 nm, which is due to the 5D0→7F2 transition of Eu3+. The Eu3+/Sm3+ co-doped Ca9Bi(VO4)7 sample exhibited stronger emission intensity at 618 nm owing to the energy transfer between Sm3+ and Eu3+. By analyzing the energy level diagram, the energy transfer process between is Sm3+ and Eu3+ explained. Moreover, the chromaticity coordinates of Ca9Bi(VO4)7:0.07Eu3+, 0.08Sm3+ was located near the standard red light region, and it also exhibited higher color purity than the blue-light-excited commercial SrS:Eu2+. Under the excitation of blue light, the excellent luminescence properties of Ca9Bi(VO4)7:Eu3+, Sm3+ makes it a potential red phosphor which can be used in white-light-emitting diodes.

Structure, luminescence and energy transfer in Ce3+ and Mn2+ codoped γ-AlON phosphors

Upon UV or blue light excitation, the codoped γ-AlON phosphor has higher luminescence intensity, quantum efficiency and thermal stability than the Mn2+-doped γ-AlON due to energy transfer and low total concentration of Ce3+ and Mn2+ ions.

A red-emitting Sr3La(1-x)Eu x (AlO)3(BO3)4 phosphor with high thermal stability and color purity for near-UV-excited wLEDs.

A high efficiency red-emitting Eu3+ doped Sr3La(AlO)3(BO3)4 phosphor has been calcined successfully through a traditional solid-state method, and the photoluminescence and cathode-luminescence properties of samples are investigated in detail. The result of density functional theory (DFT) calculation shows that the Sr3La(AlO)3(BO3)4 host lattice has an indirect band gap. The broad excitation ranges from 200 nm to 500 nm, especially the strongest excitation located in the near ultraviolet (near-UV) region, suggests that the phosphor can match well with not only blue LED chips but also near-UV LED chips. Besides, the phosphor can emit bright red light peaking at 596, 618, 655 and 706 nm under either near-UV or blue light excitation and the internal quantum efficiency can reach 40%. The temperature-dependent PL properties and calculation of color purity show that the phosphor has an excellent thermal stability and outstanding color stability. Ultimately, by employing Sr3La(AlO)3(BO3)4:Eu3+ phosphor as a red light component, a stable warm white light emission is obtained with Ra = 80, CIE = (0.3443, 0.2903) and CCT = 4680 K. These results indicate that red Sr3La(AlO)3(BO3)4:Eu3+ phosphor may have a great potential for wLEDs with fantastic properties.

A thermally stable narrow-band green-emitting phosphor MgAl2O4:Mn2+for wide color gamut backlight display application

A stable narrow-band green phosphor MgAl2O4:Mn2+peaking at 525 nm with a full-width at half-maximum of 35 nm and a quantum efficiency of 45% upon 450 nm blue-light excitation is demonstrated, and which has good promising for wide color gamut backlight display.

Dual-mode downconversion luminescence with broad near-ultraviolet and blue light excitation in Tm3+/Yb3+ codoped oxy-fluoride glasses for c-Si solar cells

In this work, we demonstrated an efficient dual-mode solar spectral converter Tm3+/Yb3+ co-doped oxy-fluoride glasses synthesized using high temperature melt-quenching method. The transmittance, photoluminescence emission (PL) and photoluminescence excitation (PLE) spectra and decay dynamics have been systematically investigated. The experimental results revealed that two distinct solar spectral converting processes, quantum cutting (QC) and down-shifting (DS) were achieved through the sensitization of Tm3+ excited multiplets and a broad band attributing to Yb3+-O2− charge transfer state (CTS), respectively. The prepared materials could convert the UV (250–370 nm) and blue (450–490 nm) photons into broad NIR emission (900–1100 nm), which coincides well with the most efficient spectral response of Si-based solar cells. The resultant Tm3+/Yb3+ co-doped oxy-fluoride glasses with dual-mode solar spectral modification indicate its potential application in improving the energy conversion efficiency of Si-based solar cells.

Photoluminescence and cathodoluminescence properties of novel rare-earth free narrow-band bright green-emitting ZnB2O4:Mn2+ phosphor for LEDs and FEDs

A novel rare-earth free narrow-band green-emitting Mn2+ doped ZnB2O4 phosphor has been synthesized successfully through solid-state method, and the photoluminescence and cathodoluminescence properties of samples were investigated in detail. The phosphor can emit bright green light peaking at 541 nm with FWHM about 41 nm under both UV and blue light excitation. The broad excitation ranges from 235 nm to 535 nm, especially the strongest excitation locates in blue region, which indicates that the phosphor can match well with not only UV LED chips but also blue LED chips. The temperature-dependent PL properties show that the phosphor has good thermal stability and outstanding color stability. From the CL spectra, it is obvious that the phosphor also exhibits intense green emission with high color purity and good color stability under low-voltage excitation, and the results indicate that the phosphor owns high saturation voltage and saturation current. In view of the outstanding performance in the PL and CL, the ZnB2O4:Mn2+ can be considered to apply in both LED and FED devices.

Rapid detection of papillary thyroid carcinoma by fluorescence imaging using a \u03b3-glutamyltranspeptidase-specific probe: a pilot study

BackgroundNodular lesions of the thyroid gland, including papillary thyroid carcinoma (PTC), may be difficult to diagnose by imaging, such as in ultrasonic echo testing, or by needle biopsy. Definitive diagnosis is made by pathological examination but takes several days. A more rapid and simple method to clarify whether thyroid nodular lesions are benign or malignant is needed. Fluorescence imaging with γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) uses γ-glutamyltranspeptidase (GGT), a cell-surface enzyme, to hydrolyze the γ-glutamyl peptide and transfer the γ-glutamyl group. GGT is overexpressed in several cancers, such as breast, lung, and liver cancers. This imaging method is rapid and useful for detecting such cancers. In this study, we tried to develop a rapid fluorescence detection method for clinical samples of thyroid cancer, especially papillary carcinoma.MethodsFluorescence imaging with gGlu-HMRG was performed to detect PTC using 23 surgically resected clinical samples. A portable imaging device conveniently captured white-light images and fluorescence images with blue excitation light. Hematoxylin-eosin (HE) staining was used to evaluate which fluorescent regions coincided with cancer, and immunohistochemical examination was used to detect GGT expression.ResultsAll 16 PTC samples exhibited fluorescence after topical application of gGlu-HMRG, whereas the normal sections of each sample showed no fluorescence. HE staining revealed that each fluorescent region corresponded to a region with carcinoma. The PTC samples also exhibited GGT expression, as confirmed by immunohistochemistry.ConclusionsAll PTC samples were detected by fluorescence imaging with gGlu-HMRG. Thus, fluorescence imaging with gGlu-HMRG is a rapid, simple, and powerful detection tool for PTC.

A Photomagnetic Sponge: High-Temperature Light-Induced Ferrimagnet Controlled by Water Sorption.

"Converting" light energy to magnetization is the attribute of molecule-based compounds called photomagnets and is inaccessible for conventional magnetic solids. The design and synthesis of such compounds, however, is a formidable challenge, and only a few examples are known, all with rather low magnetic ordering temperatures well below the boiling point of liquid nitrogen. Herein, a cyanide-bridged coordination polymer, {[MnII(imidazole)]2[WIV(CN)8]} n, exhibiting the highest light-induced magnetic ordering temperature ever observed and a magnetic hysteresis loop up to 90 K is reported. The photomagnetic effect results from the blue light excitation (450nm) of the constituent octacyanotungstate(IV) moiety, which then couples magnetically with manganese(II), resulting in light-induced ferrimagnetic ordering. The reported coordination framework shows also outstanding water sorption properties that are strongly correlated with the photomagnetic functionality. The photoswitching observed in the anhydrous state is completely quenched by the reversible capture of water, with the fully hydrated phase becoming practically non-photomagnetic.

Photophysics of color centers in visible-light-active rutile titania. Evidence of the photoformation and trapping of charge carriers from advanced diffuse reflectance spectroscopy and mass spectrometry

• The photoformation and separation of charge carriers in traps in VLA titania ceramics and titania powder were examined. • Thermoprogrammed annealing (TPA) spectra of Ti 3+ color centers photoinduced in VLA TiO 2 displayed temperature dependencies. • Highest rate of recombination of holes released into the valence band with Ti 3+ centers was due to extra charged centers. • Rate of photodesorption of O 2 occurrence in specific channel to activate VLA TiO 2 by photoexcitation of Ti 3+ centers. We herein report on the photophysics of color centers in visible-light-active (VLA) rutile titania ceramics and titania powder resulting from the photoformation and separation of charge carriers explored by a diffuse reflectance (DR) spectroscopic and kinetic study using a cryostat-type accessory for a Cary 5000 spectrophotometer after exposure of the titanias to UV radiation and Vis-light illumination. The action spectrum of the photoformation of Ti 3+ at 90 K accorded fully with the absorption spectrum of intrinsic defects in the as-synthesized TiO 2 . The photoinduced absorption spectra consisted of a set of individual absorption bands attributable to several different Ti 3+ centers. Analysis of the dependencies of the photoformation of separate centers on the wavelength of illumination and light exposure provided extraction of specific Ti 3+ centers putatively attributed to centers with excess negative charge {2Ti 3+ + V o 2+ } ⟵→ {Ti δ+ + V o 2+ } with 3 > δ > 2 formed at significantly high concentration upon maximal exposure to Vis-light illumination. Thermoprogrammed annealing (TPA) spectra of Ti 3+ color centers photoinduced in VLA TiO 2 displayed temperature dependencies of the rate of detrapping of the photoinduced holes observed optically through annihilation of the Ti 3+ centers. The TPA spectra in the range 90–500 K consisted of a set of first-order peaks corresponding to the traps, whose depths ranged from ∼0.2 eV (peak at 130 K in powder specimen) to 1.06 eV (peak at 455 K in the ceramics). The highest rate of recombination of holes released to the valence band with Ti 3+ centers, an event attributable to the Ti δ+ centers, provided TPA spectra that clearly manifested the existence of shallow traps. We also report mass spectrometric evidence of the photoformation of electrons and holes in VLA TiO 2 under Vis-light illumination through an examination of the photoadsorption of molecular oxygen and the photodesorption of photoadsorbed oxygen from the surface of powdered VLA titania specimens. Moreover, kinetics of the photodesorption of O 2 under orange light illumination, after the photoadsorption of O 2 stimulated by blue light excitation, provided experimental proof of the occurrence of an additional specific channel toward the photoactivation of VLA TiO 2 via the photoexcitation of photoinduced Ti 3+ color centers.

Subgram-Scale Synthesis of Biomass Waste-Derived Fluorescent Carbon Dots in Subcritical Water for Bioimaging, Sensing, and Solid-State Patterning.

Fluorescent carbon dots (FCDs) have received considerable attention because of the great potential for a wide range of applications, from bioimaging to optoelectronic devices. In this work, we reported the synthesis of nitrogen-doped FCDs with an average size of 2 nm in a subcritical water apparatus by using biomass waste (i.e., expired milk) as the precursor. The obtained FCDs were highly dispersed in aqueous solution because of the presence of O-containing functional groups on their surfaces. Under the excitation of ultraviolet and blue light, the FCDs exhibited excitation wavelength-dependent fluorescence in the emission range of 400–550 nm. The FCDs could be easily taken up by HeLa cells without additional surface functionalization, serving as fluorescent nanoprobes for bioimaging. The applications of FCDs as sensing agents for the detection of Fe3+, solid-state fluorescent patterning, and transparent hybrid films were also performed, demonstrating their potential for solid-state fluorescent sensing, security labeling, and wearable optoelectronics.

Reprint of Efficient fungal UV-screening provides a remarkably high UV-B tolerance of photosystem II in lichen photobionts

Lichen photobionts in situ have an extremely UV-B tolerant photosystem II efficiency (Fv/Fm). We have quantified the UV-B-screening offered by the mycobiont and the photobiont separately. The foliose lichens Nephroma arcticum and Umbilicaria spodochroa with 1: intact or 2: removed cortices were exposed to 0.7 Wm-2 UV-BBE for 4 h. Intact thalli experienced no reduction in Fv/Fm, whereas cortex removal lowered Fv/Fm in exposed photobiont layers by 22% for U. spodochroa and by 14% for N. arcticum. We also gave this UV-B dose to algal cultures of Coccomyxa and Trebouxia, the photobiont genera of N. arcticum and U. spodochroa, respectively. UV-B caused a 56% reduction in Fv/Fm for Coccomyxa, and as much as 98% in Trebouxia. The fluorescence excitation ratio (FER) technique comparing the fluorescence from UV-B or UV-A-excitation light with blue green excitation light using a Xe-PAM fluorometer showed that these photobiont genera did not screen any UV-B or UV-A The FER technique with a Multiplex fluorometer estimated the UV-A screening of isolated algae to be 13–16%, whereas intact lichens screened 92–95% of the UV-A. In conclusion, the cortex of N. arcticum and U. spodochroa transmitted no UV-B and little UV-A to the photobiont layer beneath. Thereby, the upper lichen cortex forms an efficient fungal solar radiation screen providing a high UV-B tolerance for studied photobionts in situ. By contrast, isolated photobionts have no UV-B screening and thus depend on their fungal partners in nature.

Transparent Sialon phosphor ceramic plates for white light emitting diodes applications

Wide visible light emitting Sialon phosphor ceramic plates (PCPs) have been reported for Eu2+ doped, and Gd3+ and Pr3+ co-doped systems fabricated by hot press sintering technique. The phase dependent luminescence for Eu2+ doped PCPs is also presented in this work. Intense greenish-yellow luminescence at 552 nm wavelength under blue light excitation with the highest luminous efficacy of 58.78 lm/W was observed for β-Sialon PCP. Whereas, α-Sialon phase containing PCPs with Eu2+ show orange luminescence at 590 nm wavelength under 460 nm wavelength excitation. The co-doping of Gd3+ with Eu2+ cations enhance the α-Sialon phase as well as transparency and even with a minimum content of Eu2O3 (2 wt%) shows intense orange luminescence with luminous efficacy of 46.10 lm/W which is the highest among the orange emitting PCPs. The Gd3+ co-doped with Pr3+ without Eu2+ PCP shows wide visible emission from cyan to red excited by 460 nm wavelength. Further, Gd3+and Pr3+ were co-doped with Eu2+ shows orange emission with a red shoulder emission. The PCPs coupled with 450 nm blue LED produces cool white light, day light and warm light corresponding to their phases and co-dopants.

Autofluorescence in embryos and larvae of the giant clam Tridacna noae: challenges and opportunities for epifluorescence microscopy

Epifluorescence microscopy has numerous applications in molluscan research. Methods rely on distinguishing target fluorescent signals from natural fluorescence, termed autofluorescence, of a specimen. Limited research has been conducted on the autofluorescence of marine bivalves, which hinders development of epifluorescence microscopy techniques in this sector. We examined autofluorescence in larvae of the giant clam Tridacna noae to identify challenges and opportunities in applying epifluorescence microscopy to the study of giant clams. Under blue-light excitation (λex = 460–490 nm) three sources of autofluorescence were identified in larvae of T. noae: (1) green autofluorescence of the gut region; (2) green autofluorescence of the ‘dark bodies’ anatomical structure; and (3) red autofluorescence of ingested zooxanthellae, Symbiodinium species. Each of these sources of autofluorescence varied in prevalence and relative intensity over the course of larval development. The multiple sources and varied wavelengths of the observed autofluorescence presents challenges for applying fluorescent labelling techniques. However, our study identifies epifluorescence microscopy as a novel means of examining larval ontogeny and the uptake of zooxanthellaein giant clams.

Temperature Measurements using Thermal Sensitive Paint

Abstract Article highlights practical issues concerning temperature measurements using thermal sensitive paint (abbrev. TSP). TSP paint after blue light excitation emits red light with intensity dependent on its temperature. Temperature measurements are preceded with paint calibration, according to exact experiment conditions. Purpose of calibration is to find transfer function between intensity of emitted radiation and surface temperature. To achieve this goal, special computational procedure is implemented. Devices and methodology used for paint calibration are briefly described as well as measuring sample preparation process. Short description is devoted to the procedure for calculation temperature using recorded intensity. Results obtained during calibration are presented. Final conclusions about perspective of using thermal sensitive paint in laboratory are presented, as well as advantages and disadvantages of TSP method versus other methods currently used in temperature measurements.

Synthesis and performance of green-luminescent graphene oxide modified aluminum organic composite materials under blue-light excitation

Herein, we have successfully prepared graphene oxide sheets (GOSs)/1,10-Phenanthroline monohydrate (Phen) -8-hydroxyquinoline (HQ) -Al3+ by non-covalent bonds interaction. The composite is characterized by Fourier transform infrared (FI-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), fluorescence spectroscopy and Thermogravimetric analysis studying its structure and properties. The optimal excitation wavelength of Phen-HQ-Al is 398 nm, which is red-shifted to blue light (438 nm–450) after doping the appropriate amount of GOSs. Moreover, the GOSs/Phen-HQ-Al possesses stronger fluorescence intensity, long life decay and favorable the thermal stability.

Efficient fungal UV-screening provides a remarkably high UV-B tolerance of photosystem II in lichen photobionts

Lichen photobionts in situ have an extremely UV-B tolerant photosystem II efficiency (Fv/Fm). We have quantified the UV-B-screening offered by the mycobiont and the photobiont separately. The foliose lichens Nephroma arcticum and Umbilicaria spodochroa with 1: intact or 2: removed cortices were exposed to 0.7 Wm-2 UV-BBE for 4 h. Intact thalli experienced no reduction in Fv/Fm, whereas cortex removal lowered Fv/Fm in exposed photobiont layers by 22% for U. spodochroa and by 14% for N. arcticum. We also gave this UV-B dose to algal cultures of Coccomyxa and Trebouxia, the photobiont genera of N. arcticum and U. spodochroa, respectively. UV-B caused a 56% reduction in Fv/Fm for Coccomyxa, and as much as 98% in Trebouxia. The fluorescence excitation ratio (FER) technique comparing the fluorescence from UV-B or UV-A-excitation light with blue green excitation light using a Xe-PAM fluorometer showed that these photobiont genera did not screen any UV-B or UV-A The FER technique with a Multiplex fluorometer estimated the UV-A screening of isolated algae to be 13–16%, whereas intact lichens screened 92–95% of the UV-A. In conclusion, the cortex of N. arcticum and U. spodochroa transmitted no UV-B and little UV-A to the photobiont layer beneath. Thereby, the upper lichen cortex forms an efficient fungal solar radiation screen providing a high UV-B tolerance for studied photobionts in situ. By contrast, isolated photobionts have no UV-B screening and thus depend on their fungal partners in nature.

Novel Mn4+-activated oxyfluoride Cs2NbOF5:Mn4+ red phosphor for warm white light-emitting diodes

Novel red-emitting phosphor Cs2NbOF5:Mn4+ was prepared via the ion exchange method, and its crystal structure, composition and morphology were characterized by powder X-ray diffraction, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Meanwhile, the influence of Mn4+ molar ratio on luminescence properties of Cs2NbOF5:Mn4+ has been investigated. The phosphor prepared with the Nb2O5/K2MnF6 molar ratio of 20:1 can emit intense red light under blue light excitation and improve the performances of white light-emitting diode with high color rendering index of 88.4 and low correlated color temperature of 3631 K, so this new red-emitting phosphor could find application on solid-state emitting diode.

Preparation, crystal structure and luminescence properties of red-emitting Lu3Al5O12: Mn4+ ceramic phosphor

A series of red-emitting Mn4+ doped Lu3Al5O12 (LuAG) ceramic phosphors were successfully prepared by a simple solid-state reaction method in a high-temperature muffle. MgO was co-doped as sintering aids and Mg2+ ions helped to realize the charge balance. The relations between the luminescence properties, crystal structures and the microstructures were well established. Results indicated that MgO promoted the densification of the ceramics as the specimens’ relative densities were up to 99%. Moreover, the substitution of Al3+ with Mg2+ have changed crystal structures and further affected the luminescent properties. Overall, the obtained ceramic phosphors showed strong red-light emission under excitation of ultraviolet and blue light. By optimizing the Mg2+ and Mn4+ concentration, a quantum efficiency (QE) as high as 47.8% can be achieved under the excitation of 460 nm light, indicating that the LuAG: Mn4+ ceramic phosphors are promising candidates for WLEDs applications.

Non-Covalently Pre-Assembled High-Performance Near-Infrared Fluorescent Molecular Probes for Cancer Imaging.

New fluorescent molecular probes, which can selectively target specific cell surface receptors, are needed for microscopy, in vivo imaging, and image guided surgery. The preparation of multivalent probes using standard synthetic chemistry can be a laborious process due to low reaction yields caused by steric effects. In this study, fluorescent molecular probes were prepared by a programmed non-covalent pre-assembly process that used a near-infrared fluorescent squaraine dye to thread a macrocycle bearing a cyclic arginine-glycine-aspartate peptide antagonist (cRGDfK) as a cancer targeting unit. Cell microscopy studies using OVCAR-4 (ovarian cancer) and A549 (lung cancer) cells that express high levels of the integrin αvβ3 or αvβ5 receptors, respectively, revealed a multivalent cell targeting effect. That is, there was comparatively more cell uptake of a pre-assembled probe equipped with two copies of the cRGDfK antagonist than a pre-assembled probe with only one appended cRGDfK antagonist. The remarkably high photostability and low phototoxicity of these near-infrared probes allowed for acquisition of long-term fluorescence movies showing endosome trafficking in living cells. In vivo near-infrared fluorescence imaging experiments compared the biodistribution of a targeted and untargeted probe in a xenograft mouse tumor model. The average tumor-to-muscle ratio for the pre-assembled targeted probe was 3.6 which matches the tumor targeting performance reported for analogous cRGDfK-based probes that were prepared entirely by covalent synthesis. The capability to excite these pre-assembled near-infrared fluorescent probes with blue or deep-red excitation light makes it possible to determine if a target site is located superficially or buried in tissue, a probe performance feature that is likely to be very helpful for eventual applications such as fluorescence guided surgery.