scholarly journals Application of fluorescence technique in studying dental caries

2015 ◽  
Vol 18 (2) ◽  
pp. 49-58
Author(s):  
Mien Thi Mai Pham ◽  
Tien Van Tran ◽  
Linh Quang Huynh
Keyword(s):  
Low Cost ◽  
Red Light ◽  
Emission Spectra ◽  
Rapid Test ◽  
Test Time ◽  
Fluorescence Technique ◽  
Light Emitting ◽  
Near Ultraviolet ◽  
Different Types ◽  
Carious Teeth

The aim of the present study was to investigate the fluorescence properties of sound teeth and teeth with different types of lesions. Using light-emitting diodes operating in the near ultraviolet (UVA) spectral regions for excitation, the obtained fluorescence images and spectra of carious teeth were different from sound teeth spectra due to the presence of bacteria Streptococcus mutans producing metabolites called porphyrins. The sound teeth showed the blue fluorescence with broad emission spectra from 410 nm to 650 nm (maxima at 450 nm, 500 nm and 520 nm), while the carious regions illuminated the red light with three new peaks at 625 nm, 650 nm and 690 nm. The intensity of the red fluorescent signal depends on the density of the bacteria. Based on the red fluorescence emitted by porphyrins, not only the surface lesions but also the caries hiding under the enamel layer can be detected by UVA exciting. These results provide the ability to apply fluorescence technique in the development of an early dental diagnostic tool with a number of advantages such as safety, mobility, low cost and rapid test time.

scholarly journals Luminescence properties of novel red-emitting phosphor InNb1-xPxO4:Eu3+ for white light emitting-diodes

2015 ◽  
Vol 33 (2) ◽  
pp. 331-334 ◽  
Author(s):  
An Tang ◽  
Tao Ma ◽  
Liduo Gu ◽  
Yongtao Zhao ◽  
Junhui Zhang ◽  
...  
Keyword(s):  
White Light ◽  
Luminescence Intensity ◽  
Light Emitting Diodes ◽  
Red Light ◽  
Emission Spectra ◽  
Luminescence Properties ◽  
Potential Candidate ◽  
Light Emitting ◽  
Near Ultraviolet ◽  
White Light Emitting Diodes

AbstractInNb1-xPxO4:Eu3+ red phosphors were synthesized by solid-state reaction and their luminescence properties were also studied through photoluminescence spectra. The excitation and emission spectra make it clear that the as-prepared phosphors can be effectively excited by near-ultraviolet (UV) 394 nm light and blue 466 nm light to emit strong red light located at 612 nm, due to the Eu3+ transition of 5D0 → 7F2. The luminescence intensity is dependent on phosphorus content, and it achieves the maximum at x = 0.4. Excessive phosphorus in the phosphors can result in reduction of luminescence intensity owing to concentration quenching.With the increasing content of phosphorus, the phosphors are prone to emit pure red light. This shows that the InNb1.6P0.4O4:0.04Eu3+ phosphor may be a potential candidate as a red component for white light emitting-diodes.

scholarly journals Enhanced Optical Output of Near-Ultraviolet Light-Emitting Diodes by a Monolayer of Nanospheres

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Wei Wan ◽  
Zhanxu Chen ◽  
Yongzhu Chen ◽  
Gengyan Chen
Keyword(s):  
Indium Tin Oxide ◽  
Light Emitting Diodes ◽  
Low Cost ◽  
Incident Light ◽  
Light Extraction Efficiency ◽  
Light Emitting ◽  
Hexagonal Close Packed ◽  
Exit Surface ◽  
Near Ultraviolet ◽  
Optical Output

The optical output of near-ultraviolet (NUV) light-emitting diodes (LEDs) was improved by including a monolayer of hexagonal close-packed polystyrene (PS) nanospheres. PS nanospheres with different sizes were deposited on the indium tin oxide layer of the NUV LEDs. The electroluminescence results showed that the light extraction efficiency of the NUV LEDs was increased by the inclusion of PS nanospheres, and the maximum optical output enhancement was obtained when the size of the nanospheres was close to the light wavelength. The largest enhancement of the optical output of 1.27-fold was obtained at an injection current of 100 mA. The enhanced optical output was attributed to part of the incident light beyond the critical angle being extracted when the exit surface of the NUV LEDs had a PS nanosphere monolayer. This method may serve as a low-cost and effective approach to raise the efficiency of NUV LEDs.

Synthesis and luminescence properties of red-emitting K2MgSiO4:Eu3+ phosphors

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744058
Author(s):  
Rong Yang ◽  
Huidong Tang
Keyword(s):  
Decay Curve ◽  
Emission Spectra ◽  
Solid State Reaction Method ◽  
Excitation Spectra ◽  
Red Phosphor ◽  
Light Emitting ◽  
X Ray ◽  
Dipole Interactions ◽  
Near Ultraviolet ◽  
White Light Emitting Diodes

A novel phosphor, K2MgSiO4:Eu[Formula: see text], was synthesized by a solid-state reaction method. The phase formation was checked by X-ray powder diffraction. The photoluminescence excitation, emission spectra, decay curve and CIE coordinates of samples with different Eu[Formula: see text] ion concentrations were investigated in detail. The excitation spectra show a broad wavelength range of 225–470 nm. The K2MgSiO4:Eu[Formula: see text] phosphors exhibit highly red emission peaking at about 616 nm which is assigned to the 5D[Formula: see text]F2 transition of Eu[Formula: see text]ions under the excitation of near-ultraviolet (NUV) (394 nm) light. The critical quenching concentration of Eu[Formula: see text] doped in the K2MgSiO4: Eu[Formula: see text] phosphors was about 10 mol.% and the concentration quenching mechanism was dipole–dipole interactions between Eu[Formula: see text] ions. The results indicate that K2MgSiO4:Eu[Formula: see text] is a potential red phosphor candidate for NUV-pumped white light emitting diodes.

Synthesis and luminescence properties of the red phosphor CaZrO3:Eu3+ for white light-emitting diode application

Open Physics ◽  
2011 ◽  
Vol 9 (4) ◽  
Author(s):  
Junli Huang ◽  
Liya Zhou ◽  
Yuwei Lan ◽  
Fuzhong Gong ◽  
Qunliang Li ◽  
...  
Keyword(s):  
White Light ◽  
Light Emitting Diode ◽  
Red Light ◽  
Average Diameter ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Solid State Method ◽  
Light Emitting ◽  
Near Ultraviolet ◽  
Light Region

AbstractEu3+-doped CaZrO3 phosphor with perovskite-type structure was synthesized by the high temperature solid-state method. The samples were characterized by X-ray diffraction, scanning electron microscopy, fluorescence spectrophotometer and UV-vis spectrophotometer, respectively. XRD analysis showed that the formation of CaZrO3 was at the calcinations temperature of 1400°C. The average diameter of CaZrO3 with 4 mol% doped-Eu3+ was 2µm. The PL spectra demonstrated that CaZrO3:Eu3+ phosphor could be excited effectively in the near ultraviolet light region (397 nm) and emitted strong red-emission lines at 616 nm corresponding to the forced electric dipole 5 D 0 → 7 F 2 transitions of Eu3+. Meanwhile, the light-emitting diode was fabricated with the Ca0.96ZrO3:Eu0.043+ phosphor, which can efficiently absorb ∼ 400 nm irradiation and emit red light. Therefore Ca0.96ZrO3:Eu0.043+ may have applications for a near ultraviolet InGaN chip-based white light-emitting diode.

A novel orange-red phosphor Ca3B2O6:Sm3+, A+(A = Li, Na, K) for white light emitting diodes

2014 ◽  
Vol 07 (03) ◽  
pp. 1450033 ◽  
Author(s):  
Qingbo Liu ◽  
Yufeng Liu ◽  
Fu Yang ◽  
Bing Han ◽  
Hao Feng ◽  
...  
Keyword(s):  
Emission Spectrum ◽  
Integral Intensity ◽  
Red Light ◽  
Red Phosphor ◽  
Light Emitting ◽  
Red Phosphors ◽  
Near Ultraviolet ◽  
Bright Orange ◽  
Cie Chromaticity ◽  
White Light Emitting Diodes

A novel orange-red phosphor Ca 3 B 2 O 6: Sm 3+, A+( A = Li , Na , K ) has been synthesized by solid-state reaction at 950°C. The phase purity and photoluminescence (PL) behavior of the phosphor are studied in detail using the powder X-ray diffraction (XRD) technique and PL measurements. Ca 3 B 2 O 6: Sm 3+ phosphor can be efficiently excited by near ultraviolet (n-UV) and blue light, and the emission spectrum consists of four emission peaks at 563, 599, 646 and 709 nm, generating bright orange-red light. When a cation A+ is introduced into Ca 3 B 2 O 6: Sm 3+ as charge compensator, the emission intensity of Ca 3 B 2 O 6: Sm 3+ is evidently enhanced, but the PL spectral profile is unchanged. The integral intensity of the emission spectrum of Ca 2.96 Sm 0.02 Na 0.02 B 2 O 6 excited at 401 nm is about 1.2 times than that of Y 2 O 2 S : Eu 3+ commercial red phosphor. The CIE chromaticity coordinates of Ca 2.96 Sm 0.02 Na 0.02 B 2 O 6 phosphor were (0.608, 0.365), which are close to that of the commercial red phosphors Y 2 O 3: Eu 3+ (0.655, 0.345), Y 2 O 2 S : Eu 3+ (0.622, 0.351) and Sr 2 Si 5 N 8: Eu 2+ (0.620, 0.370).

scholarly journals Synthesis and Photoluminescence Properties of Eu3+-Doped Na2YMg2V3O12: A Novel Red-Emitting Phosphor for White-Light-Emitting Diodes

2021 ◽  
Author(s):  
Weiyi Zhang ◽  
Yanqiu Shao ◽  
Ying Zhu ◽  
Yingying Shao ◽  
Zhaohui Huang ◽  
...  
Keyword(s):  
Solid State ◽  
White Light ◽  
Emission Band ◽  
Red Light ◽  
Solid State Reactions ◽  
Broad Emission Band ◽  
Light Emitting ◽  
Near Ultraviolet ◽  
Broad Emission ◽  
Red Emitting Phosphor

Abstract The fabrication and luminescent properties of novel Na2YMg2V3O12:Eu3+ phosphors produced by conventional solid-state reactions were investigated. Self-activated emission of the Na2YMg2V3O12 host produces a broad emission band ranging from 400 to 700 nm with a maximum peak at 530 nm, ascribed to the charge transfer in the (VO4)3− groups. Excitation with near-UV (365 nm) light causes the Na2YMg2V3O12:Eu3+ phosphors to emit bright red light, including both the broad emission band of the (VO4)3− groups and the sharp emission peaks of Eu3+ ions. At a quenching concentration of 0.03 mol, the Eu3+ ion emission peaks were located at 597, 613, 654 and 710 nm. As-prepared Na2YMg2V3O12:Eu3+ phosphors also exhibited stable emission at high temperatures. Furthermore, a designed and packaged white-light-emitting diode (WLED) lamp, including the obtained phosphors, commercial (Ba,Sr)2SiO4:Eu2+ green phosphors, BaMgAl10O17:Eu2+ blue phosphors and a near-ultraviolet (n-UV) chip, emitted bright white light with a good chromaticity coordinate of (0.3068, 0.3491), a satisfactory colour rendering index of 88.20 and a properly correlated colour temperature of 4460.52 K. These results indicate the potential of this Na2YMg2V3O12:Eu3+ phosphor as a red-emitting phosphor for solid-state illumination.

scholarly journals Fricke Dosimetry as a Tool to Quality Control of Photodynamic Therapy

2019 ◽  
Vol 7 (3) ◽  
Author(s):  
SUZANA OLIVEIRA SANTOS ◽  
Vivianne L. B. Souza
Keyword(s):  
Quality Control ◽  
Photodynamic Therapy ◽  
Low Cost ◽  
Red Light ◽  
Green Light ◽  
Yellow Light ◽  
Light Emitting ◽  
Low Toxicity ◽  
Cellular Necrosis ◽  
Photosensitizing Agent

Photodynamic therapy (PDT) consists of the association of a photosensitizing agent with a light source in order to cause cellular necrosis. Methylene blue, toluidine blue and malachite green are photosensitizers derived from dyes that are widely accepted in medicine, as they have low toxicity and are low cost. PDT is an alternative treatment for cancer, with significant advantages over procedures such as surgery/chemotherapy. Our laboratory has studied the Fricke solution doped with photosensitizers in an approach to obtain a quality control for PDT. The Fricke solution was prepared with ammoniacal ferrous sulfate, sodium chloride and sulfuric acid in water. The solutions modified with photosensitizers were prepared by adding 0.1 g/100 mL of the dyes. A volume of 2.6 ml of the Fricke solution modified with photosensitizers were transferred to test tubes and irradiated. The irradiated solutions had their optical densities measured in a spectrophotometer. The samples were irradiated with LED (Light Emitting Diodes) in acrylic phantoms. The FATA samples irradiated with LED showed the sensitivity of the dosimeters to red, blue, green and yellow light. A calibration curve with correlation coefficient of 0.9884 for the red light was obtained; 0.9752 for blue light; 0.9644 for the green light and 0.9768 for the yellow light. The fact that a sensitivity of the dosimeters to the LED has been occurred indicates that the PDT could be realized with LED, with lower costs than with laser. This work suggested that FATA dosimeters can be used for quality control of PDT.

A novel stibium phosphate, LiBa(SbO)2(PO4)3: synthesis, crystal structure and RE3+-activated (RE = Tb3+ and Eu3+) fluorescence performance

2019 ◽  
Vol 75 (9) ◽  
pp. 1234-1242
Author(s):  
Shi-Rui Zhang ◽  
Dan Zhao ◽  
Rui-Juan Zhang ◽  
Lin-Ying Shi ◽  
Shao-Jie Dai ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Red Light ◽  
Three Dimensional ◽  
Emission Spectra ◽  
Antimony Oxide ◽  
Molten Salt Method ◽  
X Ray Diffraction ◽  
Host Matrix ◽  
Rietveld Refinements ◽  
Light Emitting

A new stibium phosphate, lithium barium bis(antimony oxide) tris(phosphate), LiBa(SbO)2(PO4)3, was prepared by the molten salt method with LiF as the flux. The crystal structure consists of an original three-dimensional anionic framework of [(SbO)2(PO4)3]∞ built from PO4 tetrahedra sharing their corners with SbO6 octahedra. This framework delimits one-dimensional tunnels where the lithium(I) and barium(II) ions are located. The UV–Vis spectrum shows that LiBa(SbO)2(PO4)3 was transparent from 350 to 800 nm, and is thus suitable as a luminescent host matrix. We then used Tb3+ and Eu3+ activators to test its luminous performance and the purities of the prepared phosphors were studied by powder X-ray diffraction analysis with Rietveld refinements. Photoluminescence (PL) studies reveal that the emission spectra of 1 mol% RE3+-doped (RE = Tb and Eu) samples can be excited by 371 and 394 nm light, emitting green and orange–red light, respectively, for Tb3+ and Eu3+. The CIE coordinates were measured to be (0.295, 0.571) and (0.6027, 0.3967), and the luminescent lifetimes were calculated as 0.178 and 1.159 ms, respectively.

Synthesis and luminescence properties of (Lu0.95−xCe0.05)2Ca1+2xMg2Si3O12 silicate garnet phosphors and its applications

2016 ◽  
Vol 09 (03) ◽  
pp. 1650049
Author(s):  
Wei Xia ◽  
Xiyan Zhang ◽  
Liping Lu
Keyword(s):  
Light Emitting Diode ◽  
Red Light ◽  
Emission Spectra ◽  
Peak Wavelength ◽  
Excitation Peak ◽  
Light Emitting ◽  
White Leds ◽  
Reducing Atmosphere ◽  
Color Rendering ◽  
Silicate Garnet

Silicate garnet phosphors (Lu[Formula: see text]Ce[Formula: see text]Ca[Formula: see text]Mg2Si3O[Formula: see text] with [Formula: see text], 0.05, 0.1, and 0.15 were prepared by high-temperature solid-state reaction in a reducing atmosphere. The crystal structure, photoluminescence and luminescence of the phosphors were investigated. The optimum excitation peak wavelength of the phosphors ranged from 450[Formula: see text]nm to 490[Formula: see text]nm, matching the emission spectra of a blue light-emitting diode chip. The phosphors emit orange-red light after excitation that can be tuned from 589[Formula: see text]nm to 597[Formula: see text]nm by changing the concentration of calcium ions. In addition, their emission made them suitable for use in warm-white LEDs with a high-color rendering index.

scholarly journals A broadband cyan-emitting Ca2LuZr2(AlO4)3:Ce3+ garnet phosphor for near-ultraviolet-pumped warm-white light-emitting diodes with an improved color rendering index

2020 ◽  
Vol 8 (3) ◽  
pp. 1095-1103 ◽  
Author(s):  
Liangling Sun ◽  
Balaji Devakumar ◽  
Jia Liang ◽  
Shaoying Wang ◽  
Qi Sun ◽  
...  
Keyword(s):  
White Light ◽  
Light Emitting Diodes ◽  
Emission Spectra ◽  
Light Emitting ◽  
White Leds ◽  
Near Ultraviolet ◽  
Warm White Light ◽  
Color Rendering Index ◽  
White Light Emitting Diodes ◽  
Color Rendering

Broadband cyan-emitting Ca2LuZr2(AlO4)3:Ce3+ garnet phosphors enabled to fill the cyan gap in the emission spectra of near-ultraviolet-pumped warm-white LEDs, thus resulting in improved color rendering index.

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