Nanomaterials
·
2019
·Vol. 9
·期 5
·725
·
IF 4.034
Xiangyu Feng,Kai Jiang,Haibo Zeng,Hengwei Lin
Large-scale applications of conventional rare-earth phosphors in white light-emitting diodes (W-LEDs) are restricted by the non-renewable raw material sources and high energy consumption during the production process. Recently, carbon dots (CDs) have been proposed as promising alternatives to rare-earth phosphors and present bright prospects in white lighting. However, the use of CDs in W-LEDs still has two major obstacles, i.e., solid-state quenching and lack of single-component white emissive products. In this work, a facile, rapid, and scalable method for the preparation of solid-state white emissive CDs (W-CDs) is reported via microwave-irradiation heating of L-aspartic acid (AA) in the presence of ammonia. The W-CDs exhibit blue photoluminescence (PL) in dilute aqueous dispersion and their emission spectra gradually broaden (emerging new emissions at orange-yellow regions) with concentration increases. Interestingly, the W-CDs powder displays a very broad PL spectrum covering nearly the whole visible-light region under ultraviolet (UV) excitation, which is responsible for the observed white emission. Further studies revealed that the self-quenching-resistance feature of the W-CDs is probably due to a covering of polymer-like structures on their surface, thus avoiding the close contact of nanoparticles with each other. PL emission of the W-CDs is reasonably ascribed to a cross-linked enhanced effect (CEE) of the sub-fluorophores contained in the material (e.g., –NH2and C=O). Finally, applications of the W-CDs in fabricating single-component-based W-LEDs using commercially available UV chips were attempted and shown to exhibit satisfactory performances including high white light-emitting purity, high color rendering index (CRI), and tunable correlated color temperature (CCT), thus rendering great promise for W-CDs in the field of white lighting.Keywords:carbon dots;photoluminescence;solid state emission;white light-emitting diodes
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ACS Photonics
·
2023
·
IF 7
Mingjun Chen,Li Guan,Haotian Ma,You Zhang,Yufeng Chang,Fenghe Wang,Zhenyang Liu,Xu Li
As a new emerging ecofriendly light-emitting material, carbon dots (CDs) have been a research hotspot in the past decade. However, the synthesis of new types of CDs and the realization of multicolor solid-state emission remains challenging. Herein, we successfully synthesized a new type of N,Cl-doped CDs. The structure, morphology, composition, and optical properties, were well studied. The emission peak of fluorescent CDs solution can be modulated in the range of 512 to 613 nm by varying the concentration of CDs and the solvent type. To obtain a better emission of solid-state CDs, the as-prepared CDs are loaded on silica gel particles. Surprisingly, the solid-state CDs@silica can realize multicolor emission in the region of 521 to 600 nm by adjusting the ratio of CDs and silica. In addition, the single-component solar-simulated white light-emitting diode (WLED) was fabricated by using the CDs@silica particles as phosphor. The high quality of electroluminescence (EL) demonstrated the great potential of the CDs in the next generation of applications.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
高影响因子
Nanomaterials
·
2020
·Vol. 10
·期 7
·1249
·
IF 4.324
Jun Xiao,Cong Wang,Xin Min,Xiaowen Wu,Yangai Liu,Zhaohui Huang,Minghao Fang
Advances in solid-state white-light-emitting diodes (WLEDs) necessitate the urgent development of highly efficient single-phase phosphors with tunable photoluminescence properties. Herein, the Tm3+, Dy3+, and Sm3+ions are incorporated into the orthorhombic NaGdTiO4(NGT) phosphors, resulting in phosphors that fulfill the aforementioned requirement. The emission spectrum of Tm3+ions overlaps well with the adsorption spectra of both Dy3+and Sm3+ions. Under the excitation at 358 nm, the single-phase NaGdTiO4: Tm3+, Dy3+, Sm3+phosphor exhibits tunable emission peaks in the blue, yellow, and red regions simultaneously, resulting in an intense white-light emission. The coexisting energy transfer behaviors from Tm3+to Dy3+and Sm3+ions and the energy transfer from Dy3+to Sm3+ions are demonstrated to be responsible for this phenomenon. The phosphors with multiple energy transfers enable the development of single-phase white-light-emitting phosphors for phosphor-converted WLEDs.
研究领域:
材料科学
·
光学
✓ 已验证
DOI
高影响因子
ACS Photonics
·
2018
·
IF 6.88
Zuobin Tang,Gangyi Zhang,Yuhua Wang
A dipotassium hafnium trisilicate K2HfSi3O9 with wadeite structure was synthesized by solid-state reaction for the first time. Its detailed crystal structure and electronic structure were determined using XRD Rietveld refinement and density functional theory (DFT), respectively. An expected asymmetric emission band was observed in K2HfSi3O9:Eu2+ due to Eu2+ ions occupying the two symmetrically inequivalent K+ (K1 and K2) ion sites in the host lattice. The K2HfSi3O9:Eu2+ has obvious heat-sensitive luminescent features (25 °C, blue emission; 250 °C, green emission), which can be rationalized by the energy transfer from Eu1 to Eu2 under thermal stimulation. Moreover, we developed promising phosphor K2HfSi3O9:Eu2+,Sc3+ by employing the crystal-site engineering method, and tuned the emission color from blue to green with the variation of Sc3+ ions. The target phosphor K2HfSi3O9:2%Eu2+, 6%Sc3+ shows strong absorption in the spectral range of ∼250–490 nm and a narrow green-emitting band (fwhm ∼59 nm) peaking at ∼507 nm with zero emission loss at ambient temperature up to 200 °C. Such robust thermal performance was explained by possible transfer energy from the defect levels to the 5d band of Eu2+, and certified by the thermoluminescence spectrum and the decay curves in the temperature range of 25 to 250 °C. Combing this excellent green phosphor with n-UV (395 nm) or blue chips (450 nm), pc-WLEDs with high luminance, adequate color rendering index, and correlated color temperature were obtained.
研究领域:
材料科学
·
光学工程
✓ 已验证
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2021
·
IF 4.527
Lei Zhang,Xuefeng Zhang,Chaoyong Zhao,Xuan Xiao
Eu 3+ -activated Sr 3 −x Ca x La(VO 4 ) 3 phosphors were fabricated via citric-acid-assisted sol combustion. Characterization of the Sr 3 −x Ca x La(VO 4 ) 3 :Eu 3+ samples with different concentrations of Ca 2+ revealed a hexagonal crystal structure belonging to the R -3 m space group. The amount of Ca 2+ added ( x ) was controlled within 0 ≤ x ≤ 2 to yield high-purity phosphors. Scanning electron microscopy results showed that an increase in Ca 2+ concentration resulted in a decrease in the particle size of Sr 3 −x Ca x La(VO 4 ) 3 :Eu 3+ , with the shape gradually changing from nearly equiaxed to lath-shaped. The Sr 2 CaLa(VO 4 ) 3 :Eu 3+ phosphor (denoted as SCLVO:Eu 3+ ) exhibited the strongest photoluminescence (PL) intensity at 618 nm among the samples under excitation of 394-nm near-UV (NUV) light. The study of Eu 3+ doping concentration confirmed that Eu 3+ could enter the lattice of the SCLVO matrix without altering its crystal structure. SCLVO:Eu 3+ was found to strongly absorb 394 nm NUV light and 464 nm blue light. The optimal concentration of the Eu 3+ dopant in the SCLVO host was 0.11, which resulted in the phosphor achieving an excellent PL intensity and a color purity of 98.68%. Tunable luminescence from the orange area (0.5280, 0.4522) of Commission Internationale de l'éclairage (CIE) to the red area (0.6313, 0.3650) was achieved by adjusting the concentration of Eu 3+ . Under 394 nm excitation, SCLVO:0.11Eu 3+ phosphor has a quantum yield (QY) of 28.2% and excellent thermal stability with 0.383 eV activation energy . Consequently, White-light-emitting diode (WLED) based on SCLVO:0.11Eu 3+ phosphor yielded a high color rendering index (CRI), low correlated color temperature (CCT), and CIE coordinates of 91.8, 5196 K, and (0.3407, 0.3612), respectively, under the 20 mA driven current. These results indicated the tremendous potential of SCLVO:0.11Eu 3+ phosphors for application in WLEDs excited by NUV or blue light.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
Materials Today Advances
·
2023
·
IF 10
Xiao Gong,Wenjing Li,Yongzhong Wu,Xiaoyan Li,Yan Ma,Hangxiang Wang,Min Wu
Carbon nanodots (CDs) have received huge attention of researchers due to their good optical properties. However, CDs generally suffer from severely fluorescence self-quenching once they are aggregated or in solid state, limitating their applications in light-emitting devices. In this work, we report a rational strategy for synthesis of yellow fluorescent carbon nanodots (Y-CDs)-based microparticles with a high solid-state photoluminescence quantum yield (32.02%). It is the first report on designing a lamellar structured matrix to disperse CDs to realize long-wavelength solid fluorescence. The matrix is confirmed as p-phenylenediamine dihydrochloride by X-ray diffraction (XRD). 3-glycidyloxypropyltrimethoxysilane (KH-560) acts as a bridge to connect CDs to the matrix based on epoxy-amine reaction and silane hydrolysis condensation for uniform dispersion of CDs and high solid-state luminescence can be easily achieved. Meanwhile, through adjusting the amount of KH-560, the morphology of Y-CDs-based microparticles can be controlled from cube to layered structure and the fluorescence intensity can be significantly improved. Importantly, the optimal Y-CDs particles can be combined with blue chips (450 nm) to fabricate high-performance white light-emitting diodes (WLEDs) without using commercial phosphor, and the constructed WLEDs exhibit a high color rendering index (CRI) of 84.2.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2019
·
IF 4.175
Dandan Ju,Feng Song,Yingdong Han,Jun Zhang,Feifei Song,Aihua Zhou,Wei Huang,Victor Zadkov
Intense white-light color emission of lanthanide-doped core-shell structured particles at microscale level was presented under 980 nm excitation. The prepared NaYF 4 :Yb/Er@ NaYF 4 :Yb/Tm microcrystals not only can effectively prevent the deleterious cross-relaxation that occurs between the Er 3+ and Tm 3+ due to the location of the activator ions within different layers, but also possess a high luminescence efficiency due to dimensions of the micro-scale structure. The core-shell structured microcrystals presented satisfactory capacity for color control in the white region. The results show great potential in attaining white light-emitting diodes within the field emission display on specific device applications. Furthermore, the core-shell microcrystals emit white-light that presents obvious and distinct lifetimes of green, red, and blue emissions, which could achieve multicolor emissions by setting a suitable delay time. This feature demonstrates that the core-shell structured microrods offer practical use as security ink to prevent forgery, such as in identifying currency.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2018
·
IF 3.779
Rongzhi Gu,Mengyuan Guan,Na Jiang,Tianyu Yuan,Guoquan Ma,Chao Wang,Zhiping Yang,Panlai Li,Zhijun Wang
Series of Ca 9- w Ce 0.5 Y 0.5- x - y - z (PO 4 ) 7 : x Tb 3+ , y Eu 3+ , z Sm 3+ , w Mn 2+ phosphors are synthesized by a high temperature solid state method. The spectral property and fluorescence decay curves are measured and used to demonstrate the energy transfer effect in Ce 3+ -Tb 3+ , Ce 3+ -Sm 3+ , Ce 3+ -Eu 3+ , Tb 3+ -Sm 3+ , Tb 3+ -Eu 3+ and Tb 3+ -Mn 2+ . For Ca 9 Ce 0.5 Y 0.5 (PO 4 ) 7 , the concentration of Ce 3+ is higher and it can act as activator and sensitizer simultaneously. Ce 3+ and Tb 3+ can emit blue and green light under near ultraviolet excitation, respectively. Sm 3+ , Eu 3+ and Mn 2+ can produce red emission. In order to generate white light, Ce 3+ /Tb 3+ /Sm 3+ , Ce 3+ /Tb 3+ /Eu 3+ and Ce 3+ /Tb 3+ /Mn 2+ doped phosphors are investigated, and Ca 8.8 Ce 0.5 Y 0.33 (PO 4 ) 7 :0.17Tb 3+ ,0.20Mn 2+ can create high quality white light. Its color rendering index can be high up to 80.2 and correlated color temperature is 4735 K, and its thermal stability is high. The result indicates that the acquired phosphors can be potential for the use of ultraviolet excited white light emitting diodes .
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2018
·
IF 3.779
Baochen Wang,Ziyao Wang,Yangai Liu,Tao Yang,Zhaohui Huang,Minghao Fang
Crystal structure tailoring is a commonly used method for tuning the luminescence of phosphors. This study mainly aims at luminescent spectra tuning of Sr 1− x Ba x Al 2 Si 2 O 8 :Eu 2+ phosphors by substitution of Ba for Sr ions. The phase composition was characterized by X-ray powder diffraction and the crystal structure was determined by using the Rietveld refinement method. The excitation and emission spectra, diffuse reflectance spectra, and thermal quenching were also investigated in detail. The results show that Sr 1− x Ba x Al 2 Si 2 O 8 :Eu 2+ phosphors can form a series of continuous solid solutions in the range from 0 to 0.75. With the increase in x value, the emission spectra show an obvious redshift from 415 to 450 nm. The emission redshift plays an important role in enabling Sr 1− x Ba x Al 2 Si 2 O 8 :Eu 2+ to be used as a standard blue phosphor for application in white-light-emitting diodes.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Wenbin Shi,Xiao Zhang,Cong Xie,Hsueh Shih Chen,Ping Yang
To overcome the poor stability of metal halide perovskite nanocrystals (NCs) prepared in organic solvents, a solid reaction method at high temperature was developed using sol–gel porous SiO 2 as a reactor. Sol-gel SiO 2 powders were used to encapsulate CsPbX 3 NCs at high temperatures (600–800 °C) in air to get SiO 2 /CsPbX 3 glass by dispersing growth cites in advance and no ligands added. After NaOH etching, a thin dense SiO 2 shell was remained on the surface of CsPbX 3 NCs (named as CsPbX 3 @SiO 2 ).The photoluminescence (PL) quantum yield of the CsPbX 3 @SiO 2 was 86.7 %, in which their PL peak wavelengths were adjusted from 410-707 nm by changing halogen components. The dense SiO 2 shell on CsPbX 3 NCs blocked the connection of CsPbX 3 cores with water and oxygen in the external environment, resulting in CsPbX 3 @SiO 2 revealed extraordinary high stability. After immersing in water for half year, the PL intensity of CsPbX 3 @SiO 2 composites was remained unchanged and the composites still revealed bright PL after heat-treating in boiling water for 14 h. These highly stable composites were used to fabricate a white light-emitting diode, in which the color coordinates are located at (0.36, 0.33), and the color temperature reaches 5169 K which belongs to the warm white light range.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Materials Chemistry C
·
2022
·Vol. 10
·期 6
·2095-2102
·
IF 8.067
Guojun Zhou,Jialiang Ding,Xingxing Jiang,Jian Zhang,Maxim S. Molokeev,Qiqiong Ren,Jun Zhou,Shili Li,Xian-Ming Zhang
Organic–inorganic metal halides have become a multifunctional platform for manipulating photoluminescence due to highly efficient and tunable emissions, especially for lead-free Mn2+-based halides. Herein, the zero-dimensional (0D) bromides of (C5H14N3)2MnBr4 and (CH6N3)2MnBr4 with different coordination environments were designed and synthesized by a solvent evaporation method. They exhibit green and red broadband emission peaks at 528 nm and 627 nm with high photoluminescence quantum yields of 86.83% and 61.91%, respectively, which are attributed to the d–d transition (4T1(G) → 6A1(S)) of [MnBr4]2− tetrahedral and [Mn3Br12]6− octahedral units. The cases emphasize the effect of organic ligands on the intrinsic emissions of Mn2+ ions, thereby revealing the luminescence mechanism of Mn2+ ions in 0D isolated structures through the Tanabe–Sugano (TS) energy diagram. Thanks to their bright and stable emissions, the fabricated white light-emitting diode (LED) based on (C5H14N3)2MnBr4 and (CH6N3)2MnBr4 provides an outstanding color rendering index (Ra) of 90.8 at a correlated color temperature (CCT) of 3709 K, along with the CIE chromaticity coordinates of (0.3985, 0.3979) and a luminous efficacy of 51.2 lm W−1. This work aims at clarifying the relationship between the coordination units of Mn2+ and tunable emissions, and in particular, proposes a new strategy to explore phosphors excited by blue light for white LEDs.
研究领域:
材料科学
·
光学
✓ 已验证
DOI
高影响因子
Advanced Optical Materials
·
2021
·Vol. 9
·期 19
·2100688
·
IF 9.926
Yuxin Zheng,Kamile Arkin,Jiawei Hao,Siyi Zhang,Wei Guan,Lingling Wang,Yingna Guo,Qingkun Shang
In a reaction system of asparagine and p-phenylenediamine, blue, green, orange, and red carbon dots (CDs) are successfully prepared by adjusting the ratio of the two reactants. The obtained multicolor CDs have excellent stable properties and high fluorescence quantum yields (up to 74%). Clarifying the luminescence mechanism of multicolor CDs is based on the investigation of the composition, structure, and fluorescence properties of the CDs combined with quantum chemistry calculations. A high-quality white light-emitting diode (LED) with CIE color coordinates (0.33, 0.33) is successfully fabricated using a multicolor CD-epoxy resin composite, and its color temperature and color rendering index are 5612 K and 94, respectively. It is of great significance to prepare multicolor CDs with high fluorescence quantum yields by single-factor control. Using multicolor CDs to fabricate standard white LEDs close to sunlight will significantly increase the practical application value of CDs.
研究领域:
材料科学
·
光学工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）