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Highly efficient near-UV-excitable Ca2YHf2Al3O12:Ce3+,Tb3+ green-emitting garnet phosphors with potential application in high color rendering warm-white LEDs
摘要： Inorganic phosphors with broadband near-ultraviolet (near-UV) excitation and efficient visible emissions are highly important for fabricating high-performance near-UV-pumped white light-emitting diodes (LEDs). Herein, we reported on novel efficient near-UV-excitable Ce3+/Tb3+ ions co-activated Ca2YHf2Al3O12 (CYHA) green-emitting garnet phosphors, which were successfully prepared through a high-temperature solid-state reaction process. X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, photoluminescence, CIE color coordinates, internal and external quantum efficiency, and temperature-dependent emission spectra were used to characterize the samples. Interestingly, due to the efficient energy transfer from Ce3+ to Tb3+ ions in CYHA, the CYHA:Ce3+,Tb3+ samples presented a wide excitation band in the 370-470 nm region peaking around 408 nm owing to the 4f-5d transition of Ce3+ ions, and under 408 nm excitation they showed intense characteristic sharp green emissions around 543 nm corresponding to the 5D4→7F0-6 transitions of Tb3+ ions. The energy transfer mechanism from Ce3+ to Tb3+ ions was ascribed to the quadruple-quadruple interaction, and the energy transfer efficiency reached as high as 93.2%. Notably, the composition-optimized CYHA:0.03Ce3+,0.6Tb3+ sample exhibited high internal quantum efficiency (IQE) of 78.5% and external quantum efficiency (EQE) of 56%, which were much higher than those of the Tb3+ singly-activated CYHA:0.6Tb3+ sample (IQE = 8%, EQE = 2.2%). Finally, a prototype white LED device was made by combining a 400 nm near-UV-emitting LED chip with the phosphor blend of the as-prepared CYHA:0.03Ce3+,0.6Tb3+ green phosphors, commercial BaMgAl10O17:Eu2+ blue phosphors and commercial CaAlSiN3:Eu2+ red phosphors, which emitted bright warm-white light with good CIE chromaticity coordinates of (0.391, 0.356), low correlated color temperature of 3528 K and high color rendering index of 92.3 under 120 mA driven current. This work opens up new opportunities for the development of efficient color converters toward near-UV-pumped warm-white LEDs with high color rendering index.
关键词： white LEDs,green-emitting garnet phosphors,Ce3+/Tb3+ co-activated,near-UV-excitable,energy transfer
更新于2025-09-19 17:13:59
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Efficient green-emitting Ca2GdZr2Al3O12:Ce3+,Tb3+ phosphors for near-UV-pumped high-CRI warm-white LEDs
摘要： In this work, we reported novel efficient Ce3+/Tb3+ co-doped Ca2GdZr2Al3O12 (CGZA) green-emitting phosphors by traditional solid state method. The phase purity, crystal structure, morphology, photoluminescence properties, internal quantum efficiencies (IQEs), and thermal stability of the samples were systematically investigated. The obtained results revealed that there was an obvious spectral overlap between the emission spectrum of Ce3+ singly doped CGZA phosphors and excitation spectrum of Tb3+ singly doped CGZA phosphors, and efficient energy transfer from Ce3+ to Tb3+ ions existed in Ce3+ and Tb3+ co-doped CGZA phosphors. The Ce3+→Tb3+ energy transfer mechanism was ascribed to the dipole-dipole interaction. The CGZA:Ce3+,Tb3+ phosphors exhibited a broad excitation spectrum in the wavelength range of 370-470 nm with a maximum at 408 nm corresponding to the spin-allowed 4f-5d transition of Ce3+ ions. Upon near-ultraviolet (near-UV) excitation at 408 nm, the composition-optimized CGZA:0.02Ce3+,0.8Tb3+ sample showed intense sharp narrow-line emissions at 485, 543, 591, 629, 643, 663, and 679 nm due to the 5D4→7FJ (J = 6-0) transitions of Tb3+ ions, along with a good IQE of 51%. Lastly, a white LED device was fabricated by using as-prepared CGZA:0.02Ce3+,0.8Tb3+ green phosphors, commercial BaMgAl10O17:Eu2+ blue phosphors, and CaAlSiN3:Eu2+ red phosphors, and under 300 mA driven current it gave bright warm-white light with a low correlated color temperature of 3969 K and a high color rendering index (Ra = 91.2). Our work provides a new perspective for the design and fabrication of efficient color conversion materials toward near-UV LED-based warm-white LEDs.
关键词： Garnet,Ce3+ ions,White LEDs,Phosphors,Tb3+ ions,Photoluminescence
更新于2025-09-16 10:30:52
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Immediate effect of pulsed high-intensity neodymium-doped yttrium aluminum garnet (Nd: YAG) laser on staphylococcus aureus and pseudomonas aeruginosa growth: an experimental study
摘要： The aim of this study was to evaluate the effect of pulsed high intensity neodymium-doped yttrium aluminum garnet (Nd: YAG) laser on staphylococcus aureus (S. aureus) and pseudomonas aeruginosa (P. aeruginosa) bacterial growth, which cause many health problems and establish which doses are effective in bacterial inhibition. Five samples of S. aureus and five samples of P. aeruginosa were prepared in the microbiology lab, one used as control sample and the other 4 samples acted as experimental samples. The experimental samples received pulsed high intensity Nd: YAG laser with a total dose of 500, 600, 700 and 800 joules. The primary measures are colony count and the percentage decrease in colony count, the colony count was assessed at baseline and after 24 h of laser application. There was significant decrease in colony count and the percentage decrease in colony count after pulsed high intensity Nd: YAG laser application in all experimental samples of S. aureus and P. aeruginosa after 24 h of application for all doses (500, 600, 700 and 800 j) as compared with the control sample, with the most effect in higher doses of pulsed high intensity Nd: YAG laser than lower doses in both types of bacteria. pulsed high intensity Nd: YAG laser was found to be an effective modality for inhibition of S. aureus and P. aeruginosa growth after a single application.
关键词： Bacterial growth,Pulsed high intensity neodymium-doped yttrium aluminum garnet (Nd: YAG) laser,Colony count
更新于2025-09-16 10:30:52
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Using erbium-doped yttrium aluminum garnet laser irradiation in different energy output levels versus ultrasonic in removal of root canal filling materials in endodontic retreatment
摘要： Objectives: The objective of this study was to evaluate the efficacy of erbium?doped yttrium aluminum garnet (Er:YAG) laser irradiation in different energy outputs versus ultrasonic in gutta-percha removal during the endodontic retreatment. Materials and Methods: A total of 21 extracted human lower premolars were divided into three groups (n = 7). Following the standardized preparation of the root canals with Wave One Rotary system and obturation with gutta-percha: Group I was treated with ultrasonic, Group II by Er:YAG laser with 40 mJ/Pulse, and Group III by Er:YAG laser with 50 mJ/Pulse for the removal of gutta?percha from the canals. Two extra teeth were treated by Er:YAG laser with 135 mJ/Pulse as control group. For all groups, time for gutta-percha removal was recorded. Samples were then splited into two halves and tested by scanning electron microscope and stereomicroscopic evaluation under different magnification power to observe the efficacy of each method used in the removal of gutta-percha. Results: Statistical analysis of Kruskal–Wallis suggested that there are significant difference between the groups in relation to removal time (P < 0.05) and 2 × 2 Mann–Whitney U-test among the groups revealed that there is no significant difference between 40 and 50 mJ laser outputs (P > 0.05), but ultrasonic versus 40 and/or 50 mJ laser outputs were significantly different (P < 0.05). Conclusions: Er:YAG laser beam was not so efficient when compared to ultrasonic to reach the deeper parts of the canals as it was asserted, thermal side effects and burning damages were observed on the root canal dentinal walls. Moreover, the delivery system was not flexible enough to compensate the curvature of the canal system even though we used more straight canals as the sample ones as well as more time-consuming than the ultrasonic and more clinical time, rendering it to be less efficient in the removal of the obturation material during endodontic retreatment procedures.
关键词： gutta-percha removal,erbium-doped yttrium aluminum garnet lasers,Endodontics,retreatment,lasers
更新于2025-09-16 10:30:52
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Malpositioned canine treatment with autotransplantation and laser
摘要： Children and young adults often have tooth loss due to congenital tooth deficiency, trauma, or caries. Autotransplantation has many benefits. The transplanted tooth can be moved orthodontically, maintains alveolar bone growth potential during eruption, and functional periodontal ligament function also permits tooth eruption, allows the defected areas to be filled with the bones; gingival contour is much more successful than the one obtained with prosthesis. In this paper, treatment steps and follow?up results of autotransplantation case supported with biostimulation are mentioned. A 14?year?old female patient was admitted to the clinic with a complaint of decayed tooth 53 and malposed tooth 13. Mobile primary tooth was pulled out, and the socket was shaped with surgical drills. By performing transplantation of ectopic canine, splint was applied with steel wire and composite. Diode laser was used to provide deep disinfection of canals. The patient underwent low-dose laser therapy for biostimulation immediately after these procedures. We did not encounter any ankylosis, root resorption, periodontal, or functional problems in our evaluation with computed tomography after 3 years follow-up of the patient.
关键词： erbium,biostimulation,Autotransplantation,diode laser,chromium:yttrium-scandium-gallium-garnet
更新于2025-09-16 10:30:52
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Effect of Er:YAG laser on debonding strength of laminate veneers
摘要： Objective: The purpose of this study was to evaluate the debonding strength of laminate veneers after using erbium?doped: yttrium aluminium garnet (Er:YAG) laser. Materials and Methods: A total of 60 bovine mandibular incisor teeth were divided into two groups (n = 30). Cylindrical specimens (0.7 mm × 5 mm) were fabricated from Empress II ceramic. Then, they were cemented to incisors using dual?cured resin cement (Variolink II). In the first group, no laser application was performed. The Er:YAG laser was applied on each laminate veneer at the test group for 9 s by using the scanning method. Shear force to remove the laminate veneers were applied with universal testing machine at a crosshead speed of 1 mm/min. Results: Results of this study exhibited significant differences between the control (27.28 ± 2.24 MPa) and test group (3.44 ± 0.69 MPa) (P < 0.05). Conclusion: This study shows that application of Er:YAG laser decreased the bond strength of laminate veneers.
关键词： Debonding,shear bond strength,scanning method,erbium-doped:yttrium aluminium garnet laser,laminate veneers
更新于2025-09-16 10:30:52
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Ionic occupation sites, luminescent spectra, energy transfer behaviors in Y3MgAl3SiO12: Ce3+, Mn2+ phosphors for warm white LED
摘要： The Ce3t and Mn2t doped Y3MgAl3SiO12 (YMAS) phosphors were synthesized by the high-temperature solid-state reaction in 5%H2–95%N2 reduced atmosphere. Rietveld refinement of X-ray diffraction data indicated that co-doped YMAS phosphors had a garnet type cubic structure with the Ia3d space group. Ce3t occupies the lattice sites of Y3t. Mn2t occupies both lattice sites of MgO6 octahedron and AlO4 tetrahedron, emitting optical lights centered at 613 nm (Mn2t (I)) and 723 nm (Mn2t (II)), respectively. The orange-yellow light with the range of 450 nm–750nm was obtained by the energy transfer of Ce3t(cid:0) Mn2t with a maximum value of 69.2% of energy transfer efficiency. The integrated warm white LED produced white light with CRI of 85.4, CCT of 4502 K, and a CIE color coordinate (0.3542, 0.3269). It indicated that the phosphor might be suitable for blue light-excited white LEDs.
关键词： Phosphor,Y3MgAl3SiO12,White LED,Energy transfer,Garnet
更新于2025-09-16 10:30:52
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Successful Treatment of Cosmetic Eyebrow Tattoos in Fitzpatrick III‐IV With Picosecond (1,064, 532‐nm) Neodymium‐Doped Yttrium Aluminum Garnet Laser With a Perfluorodecalin‐Infused Patch: A Pilot Study
摘要： Background and Objectives: Nanosecond Q‐switched lasers have been used for the removal of traditional and cosmetic tattoos. Picosecond lasers utilize pulse durations of 10?12 and provide more efficient clearance of tattoos. Safe and effective removal of tattoos is especially important in cosmetically sensitive areas such as the face. We report four patients with skin types (III–IV) who have had successful removal of eyebrow tattoos with the picosecond (1,064‐, 532‐nm) laser using a perfluorodecalin‐infused patch (PFD). Study Design/Materials and Methods: Patients with eyebrow tattoos underwent treatment with dual‐wavelength picosecond Nd:YAG laser at 1,064‐nm with a 3 mm spot size and fluence of 4–4.6 J/cm2. The 532‐nm wavelength was also used during treatment #1 (patient 2 only) with a 4 mm spot size and fluence of 0.5 J/cm2. Patient 1 had a total of three treatments (6–8 weeks apart). The remaining patients, each had only one treatment. Patients were photographed prior to treatment and subsequently at each follow‐up. Results: Immediately following each laser treatment, only mild and transient localized erythema and edema was observed. Some epidermal crusting was noted for 3–5 days following each treatment. Eyebrow hair growth was not affected and no adverse events were reported. There was 75% clearance in patient 1 after three treatments over a period of 2.5 months, 75% clearance in patient 2 after one treatment, 90% clearance in patient 3 after one treatment, and 100% clearance in patient 4 after one treatment. Conclusions: The 532‐ and 1,064‐nm wavelength of the picosecond Nd:YAG laser was safely used to clear brown and black ink eyebrow tattoos in four patients, three of whom were skin type IV, and one of whom underwent eyebrow tattoo via microblading, a novel and popular technique for cosmetic tattoos. The use of picosecond laser provides several treatment advantages to Q‐switched laser when treating eyebrow tattoos. In our experience, it required less number of treatments and lower fluences. This, along with use of the perfluorodecalin‐infused patch resulted in excellent outcomes for our patients with no significant side effects.
关键词： microblading,Nd:YAG,permanent makeup,picosecond,cosmetic tattoos,eyebrow tattoo,neodymium‐doped yttrium aluminum garnet
更新于2025-09-12 10:27:22
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Femtosecond Laser Written Depressed-Cladding Waveguide 2 × 2, 1 × 2 and 3 × 3 Directional Couplers in Tm3+:YAG Crystal
摘要： Ion-doped crystal-based compact devices capable of beam splitting and coupling are enthralling for a broad range of classical and quantum integrated photonics applications. In this work, we report on the fabrication of depressed-cladding waveguide 2D 2×2, 1×2 and 3D 3×3 directional couplers in Tm3+:YAG crystal by femtosecond laser writing. The performances of the couplers are characterized at 810 nm, showing single-mode guidance, polarization independence, ?nely matched splitting ratios. These results open up new opportunities in the bene?cial fabrication of 3D circuits and devices in crystals.
关键词： crystal,femtosecond laser writing,directional coupler,depressed-cladding waveguide,integrated photonics,yttrium aluminum garnet,quantum memory
更新于2025-09-12 10:27:22
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Green emitting Ba1.5Lu1.5Al3.5Si1.5O12: Ce3+ phosphor with high thermal emission stability for warm WLEDs and FEDs
摘要： By hetero-valence substituting Ba2+-Si4+ for Lu3+-Al3+ pair in Lu3Al5O12: Ce3+, a new green phosphor Ba1.5Lu1.5Al3.5Si1.5O12: Ce3+ (BLAS: Ce3+) has been obtained. It crystallizes in garnet structure with space group Ia-3d (230). In the structure, Ba2+ ions are incorporated into both dodecahedral Lu3+ and octahedral Al3+ sites while Si4+ ions only occupy tetrahedral Al3+ sites. Under the blue light irradiation of 450 nm, an intense green light peaking at 520 nm was observed and the PL spectrum can be fitted in two Gaussian components, due to the crystal field splitting of Ce3+ 5d states under D2 symmetry constrains. The optical doping concentration of BLAS: Ce3+ is 6% mol, of which the IQE and EQE are 89.1% and 51.8%, respectively. Furthermore, this sample exhibits an extremely good thermal stability, i.e. the integrated emission intensity is still more than 90% of the initial intensity at 480 K. Then, a w-LED device was fabricated from this new green phosphor BLAS: Ce3+ and commercial red phosphor (Ca,Sr)AlSiN3: Eu2+, which shows a quite high color rendering (Ra = 88.2) and a relatively low color temperature 4772 K. Besides, the phosphor exhibits a stable chromaticity under different acceleration voltages. The phosphor may be promising material for the development of solid-state lighting and display systems.
关键词： quantum efficiency,thermal stability,luminescence,garnet structure,lighting and display
更新于2025-09-12 10:27:22