Yellow Emission Research Articles

Optical characterization of rare-earth activated La2-xLnx (MoO4)3 (Ln=Dy, Sm) phosphors

Dysprosium and Samarium doped Lanthanum molybdate (La2-xLnx(MoO4)3, Ln=Dy/Sm) powders were synthesized by the conventional solid-state ceramic route. X-ray diffraction studies confirmed the monoclinic phase of the samples with space group c2/c. Diffuse reflectance and photoluminescence spectrum revealed the optical properties of La2-xLnx(MoO4)3 samples. The band gap of doped La2-x(MoO4)3:x(Dy/Sm) shows a linear dependence on the doping concentration of rare-earth up to an optimum concentration. Low-symmetry site of Dy3+within the La2(MoO4)3 host resulted in a sharp yellow emission peak (575 nm) that dominates over blue emission (481 nm). Sm3+ doped samples showed intense orange-red emissions under an excitation wavelength of 404 nm. The variation of the lifetime of the luminescence peaks was studied in detail and the CIE colour coordinates and correlated colour temperature were calculated for varying rare-earth concentration as well as excitation wavelength to ascertain their suitability in phosphor applications. Dy3+ doped La2(MoO4)3 powders showed near white light emission and Sm3+ doped La2(MoO4)3 powders showed sharp emission in the orange-red region. Sharp excitation bands in near-UV (NUV) region in the luminescence spectra of La2-xDyx(MoO4)3 and La2-xSmx(MoO4)3 compounds establish the prospects of using these samples in NUV -LED applications. To investigate the effect of Sm3+ and Dy3+ co-doping on Lanthanum molybdate, a series of compounds of composition La1.8-xDy0.2Smx(MoO4)3 (x = 0.005, 0.02, 0.04 and 0.06) and La1.925-xSm0.075Dyx(MoO4)3 (x = 0.005, 0.02 and 0.04) were synthesized by the solid-state ceramic route. The effect of co-doping on the luminescence, CIE colour coordinates, correlated colour temperature and colour purity were studied.

Surface-dependent quenching of Qdot emission can be a new tool for high resolution measurements

Single quantum dots (Qdots) are often used in the field of single-molecule imaging. Qdots are sensitive to changes in the physical interactions between the Qdots and the surrounding materials. However, the spectral changes in a single Qdot emission have not been studied in detail. Low-temperature plasma treatment of glass surfaces reduced the intensity of the 655 nm emission peak of Qdot655 on glass surfaces, but did not significantly change the intensity of the 580 nm emission. Silanization of the glass surface increases the thickness of the silane layer, and the 655 nm emission peak increased. When single Qdots on the untreated glass were imaged, plasma treatment decreased the intensity of red emission and increased yellow emission. When Qdots were brought close to the glass surface in the range of 28–0 nm, the red emission intensity decreased and the yellow emission intensity increased slightly. When single actin filaments were labeled with Qdots, fluctuations of the yellow and red emission of the Qdot were detected, which reflected the very small distance changes. Our results indicate that the local interaction of Qdots with the glass surface improves the spatial and temporal resolution of optical measurements of biomolecules labeled with Qdots.

Cyanopyridone-cored fluorophores with triphenylamine peripheries: From molecular design to OLED fabrication studies

• Seven novel cyanopyridone-based D-A-D type molecules with a fixed triphenylamine donor, were synthesized. • Theoretical, optical, solvatochromic, thermal, electrochemical, electrical, and EL studies were performed to evaluate structure-property relationships. • Doped OLEDs using novel fluorophores as dopants outperform non-doped devices. • OLEDs emit yellow light with maximum efficiencies of 10.72 cd/A, 7.87 lm/W, and 5.32%. Amongst many types of fluorescent organic materials, compounds with π-conjugation between an electron donor (D) and electron acceptor (A) have been intensively investigated as effective organic electroluminescence (EL) device components. Herein, we report the synthesis and structural characterization of a new series of D-A-D configured small molecule-based fluorophores ( TPA-CyP1-7 ) having triphenylamine ( TPA ) as a donor unit and 3-cyanopyridine-2-one ( CyP ) as an acceptor core with different architects for use as efficient yellow light emitters in fluorescent organic light-emitting diodes (OLED). The detailed photophysical, solvatochromic, thermal, electrochemical, and EL properties, including quantum chemical calculations, were systematically investigated to study their relation between structure and properties. All the fluorophores show high fluorescent quantum yields in the solid film state and display high thermal stability with decomposition temperatures above 350 o C. The study reveals that they possess appropriate HOMO and LUMO energies level for effective charge injection. Finally, these yellow luminogens were employed to fabricate new OLED devices as sole emitters and dopants with CBP host materials. Interestingly, the host-guest devices doped with CBP host emitters show a remarkable improvement in the overall device performance. Among them, the TPA-CyP3 -based doped device has achieved a maximum current efficiency ( η c ), high power efficiency ( η p ), and good external quantum efficiency ( η EQE ) of 10.72 cd/A, 7.87 lm/W, and 5.32%, respectively.

Dual-state emission and mechanofluorochromic properties of coumarin derivatives containing α-cyanostilbene

Four novel coumarin derivatives (CM-H, CM-F, CM-CH3 and CM-CF3) functionalized by α-cyanostilbene unit were designed and synthesized. The molecular spatial structure and photophysical performances were systematically studied and discussed. The fluorescent spectra indicate that these coumarin derivatives display dual-state emission (DSE) characteristic. In dilute organic solutions, strong fluorescent emissions originated from intramolecular charge transfer (ICT) process, and in aggregated states, the bright fluorescent emissions are attributed to the collective effects of restriction of intramolecular motions and J-aggregation stacking. Meanwhile, these coumarin derivatives all exhibited mechanofluorochromic (MFC) property, in particular, compound CM-CF3 exhibit the reversible conversion between yellow and red emission. The XRD and SEM experimental results confirm that the MFC mechanism is based on the conversion of degree of crystallinity. Our study provides a reasonable approach for designing DSE materials with the MFC property.

Effect of the Host Lattice Environment on the Expression of 5s2 Lone-Pair Electrons in a 0D Bismuth-Based Metal Halide.

ns2-Metal halide perovskites have attracted wide attention due to their fascinating photophysical properties. However, achieving high photoluminescence (PL) properties is still an enormous challenge, and the relationship between the lattice environment and ns2-electron expression is still elusive. Herein, an organic-inorganic Bi3+-based halide (C5H14N2)2BiCl6·Cl·2H2O (C5H14N22+ = doubly protonated 1-methylpiperazine) with a six-coordinated structure has been successfully prepared, which, however, exhibits inferior PL properties due to the chemically inert expression of Bi3+-6s2 lone-pair electrons. After reasonably embedding Sb3+ with 5s2 electrons into the lattice of (C5H14N2)2BiCl6·Cl·2H2O, the host lattice environment induces the Sb-Cl moiety to change from the original five-coordinated to six-coordinated structure, thereby resulting in a broad-band yellow emission with a PL efficiency up to 50.75%. By utilizing the host lattice of (C5H14N2)2BiCl6·Cl·2H2O, the expression of Sb3+-5s2 lone-pair electrons is improved and thus promotes the radiative recombination from the Sb3+-3P1 state, resulting in the enhanced PL efficiency. This work will provide an in-depth insight into the effect of the local structure on the expression of Sb3+-5s2 lone-pair electrons.

Dual Lewis Acid- and Base-Responsive Terpyridine-Based Hydrogel: Programmable and Spatiotemporal Regulation of Fluorescence for Chemical-Based Information Security.

A huge amount of data inundated in our daily life; there is an ever-increasing need to develop a new strategy of information encryption-decryption-erasing. Herein, a polymeric DCTpy/PAM hydrogel has been fabricated to store information via controllable Eu3+/Zn2+ ionoprinting for hierarchical and multidimensional information decryption. Eu3+ and Zn2+ have a competition and dynamic interaction toward DCTpy under NH3 stimuli in the polymeric DCTpy/PAM hydrogel network. The Eu(III)/Zn(II)@DCTpy/PAM hydrogel exhibits light red fluorescence of Eu3+ due to the antenna effect. Upon the addition of NH3, dissociation of the Eu3+-DCTpy complex takes place, and the Zn(II)/DCTpy/NH3 complex is formed with both ICT (intramolecular charge-transfer) and PET (photo-induced electron-transfer) process characteristics that exhibits yellow emission color. Subsequently, HCl can quench the fluorescence of the resulting hydrogel. By integrating transparency, adhesiveness, and programmable stimuli responsiveness of the hydrogel blocks in to one system, complex, multistage, and time-controlled information storage-encryption-decryption-erasing in sequence with multidimensions is illustrated via the molecule diffusion method. This work provides a novel and representative strategy in fabricating information encryption-decryption-erasing materials with high capacity and complexity by a simple terpyridine-based hydrogel.

Effect of pH on the secondary structure and thermostability of beetle luciferases: structural origin of pH-insensitivity.

Beetle luciferases were classified into three functional groups: (1) pH-sensitive yellow-green-emitting (fireflies) which change the bioluminescence color to red at acidic pH, high temperatures and presence of heavy metals; (2) the pH-insensitive green-yellow-emitting (click beetles, railroad worms and firefly isozymes) which are not affected by these factors, and (3) pH-insensitive red-emitting. Although the pH-sensing site in firefly luciferases was recently identified, it is unclear why some luciferases are pH-insensitive despite the presence of someconserved pH-sensing residues. Through circular dichroism, we compared the secondary structural changes and unfolding temperature of luciferases of representatives ofthese three groups: (1) pH-sensitive green-yellow-emitting Macrolampis sp2 (Mac) and Amydetes vivianii (Amy) firefly luciferases; (2) the pH-insensitive green-emitting Pyrearinus termitilluminans larval click beetle (Pte) and Aspisoma lineatum (Al2) larval firefly luciferases, and (3) the pH-insensitive red-emitting Phrixotrix hirtus railroadworm (PxRE) luciferase. The most blue-shifted luciferases, independently of pH sensitivity, are thermally more stable at different pHs than the red-shifted ones. The pH-sensitive luciferases undergo increases of α-helices and thermal stability above pH 6. The pH-insensitive Pte luciferase secondary structure remains stable between pH 6 and 8, whereas the Al2 luciferase displays an increase of the β-sheet at pH 8. The PxRE luciferase also displays an increase of α-helices at pH 8. The results indicate that green-yellow emission in beetle luciferases can be attained by: (1) a structurally rigid scaffold which stabilizes a single closed active site conformation in the pH-insensitive luciferases, and (2) active site compaction above pH 7.0 in the more flexible pH-sensitive luciferases.

Photonic crystal induced multi-color luminescence of one AIEgen and its dual-mode anticounterfeiting application

The aggregation-induced emission luminogens (AIEgens) have attracted extensive attention and have been rapidly applied in various fields, such as optical sensors, display, and bioimaging. Usually, AIEgens present a broad-band emission and are potential to obtain multi-color luminescence by separating and filtering partial emission ranges, which will make one AIEgen emit different colors. Here, photonic crystal (PC) structures are employed as tunable filters to construct AIEgens-embedded luminescent PCs (LPCs) with variable color outputs. The designed LPC structure consists of polystyrene (PS) spheres and TVP AIEgens. By matching the photonic band gaps (PBG) of PCs with the emission band of AIEgens, the full width at half maximum can be reduced and the emission wavelength becomes tunable. Based on the changeable PBGs of PCs which can be controlled by the lattice constant, the TVP AIEgens are combined with PCs built by PS spheres with diameters of 230, 254, and 273 nm to fabricate LPCs. As a result, red, green, and yellow emission colors were realized respectively under the same viewing angle (0°). Moreover, owing to the angle-dependence of PBG, the emission color of a single LPC (D = 260 nm) displayed green, yellow, red, and orange emission colors at different viewing angles (0°-60°). The modulation effect of PCs provides the same AIE molecule with tunable luminescence. Besides the tunable emission colors, the LPCs also show bright angle-dependent structural colors under natural light. The tunable emission and reflected structural colors provide LPCs with great potential in the fields of display, information encryption, and anti-counterfeiting.

Spectroscopic characterizations and investigation of Judd-Ofelt intensity parameters of Dy3+-doped Ba2La8(SiO4)6O2 near white light emitting phosphor

A series of Dy3+-activated Ba2La8(SiO4)6O2 phosphors were synthesized using the solid-state method with the objective of developing single host white light emitting phosphors for use in solid state lighting applications. The Dy3+ concentration varied between 0.01 and 0.05 mol%. The as-prepared phosphors crystal structure, optical, and photoluminescent properties (PL), along with energy transfer mechanism and luminescence decay, were investigated. The production of a single-phase Ba2La8(SiO4)6O2 with hexagonal symmetry was verified by the findings of the X-ray diffraction analysis. When the Ba2La8(SiO4)6O2: Dy3+ phosphors are exposed to ultraviolet light, they emit the characteristic yellow PL emissions caused by the 4F9/2 → 6H13/2 transition. The Judd-Ofelt (J-O) parameters (Ω2, Ω4, Ω6) were computed using the excitation spectra. The characteristics of the Dy3+ transition indicate that the asymmetric environment around the ligand was suggested by the trend, which was followed by J-O parameters. Due to the dominance of the electric-dipole transition in the luminescence spectrum, the Ba2La8(SiO4)6O2:0.03Dy3+ phosphor displayed yellowish white emission with CIE coordinates of (0.358, 0.398) and a CCT of 4724 K. The synthesized phosphor may be a useful material in the fabrication of white-emitting phosphor for LEDs application.

Synthesis of a fluorescent, single-benzene-based molecule for rapid detection of HCl gas

A deprotonated 2,5-dihydroxyterephthalic acid (DHT) was synthesized to obtain a water-soluble, fluorescent molecule (DHT-K). The deprotonated DHT-K was converted to DHT upon exposure to acidic gas, changing fluorescence color from yellow to blue. DHT-K was incorporated to poly(vinyl alcohol) to form a film, and the film showed the same fluorescence change when exposed to HCl gas. The blue fluorescence of HCl-exposed DHT-K film was returned to yellow emission by simple treatment with NH3 gas, showing effective regeneration. Using detectable fluorescence changes by the naked eye, DHT-K can be a potential candidate for a fluorescent indicator toward HCl gas.

Excitation wavelength-dependent multi-emission in Sb3+/Bi3+/Er3+ codoped perovskite toward optical anti-counterfeiting and information storage

Inorganic lead-free halide perovskites are quite desirable for various applications due to their outstanding optoelectronic performances. However, excitation wavelength-dependent multi-emission in a single luminophore is less reported. In this study, Sb3+/Bi3+/Er3+ codoped Cs2Ag0.1Na0.9InCl6 lead-free double perovskite with upconversion and downshifting luminescence modes has been developed. The double perovskite displays a dual-emission band located at 450 nm and 580 nm under excitation of 355 nm. The blue emission originates from self-trapped excitons (STEs) in [SbCl6]3- octahedrons, while the yellow emission comes from STEs between states localized in the BiCl6 and AgCl6 octahedra. Interestingly, the phosphor’s emission can be dynamically adjusted by excitation wavelength and Sb3+ doping concentration. Not only that, the phosphor can also generate upconversion green light upon the irradiation of 980 nm lasers. The multi-excitation wavelength characteristics of this perovskite make it very suitable as a material for anti-counterfeiting and encoded information storage, and the excellent temperature stability and moisture resistance of this perovskite also make it more promising.

A smart ratiometric fluoresence and colorimetry dual-responsive sensor for morin determination based on the complex between carbon quantum dots and polyethyleneimine

As a representative flavonoid, morin exhibits multi-biological activities, but its abuse endangers human health. Developing advanced technology for morin determination is urgently needed. In this study, a dual-responsive approach was reported for morin based on the complexing of carbon quantum dots (CQDs) and polyethyleneimine (PEI). The CQDs were fabricated via an improved hydrothermal method employing tyrosine and malic acid. Binding with PEI induced an 8-fold emission enhancement and a slight red-shift to 445 nm of CQDs because of the complexing of PEI and CQDs. Further morin introduction led to the blue emission (445 nm) quenching of CQDs-PEI and a yellow emission (560 nm) generation, which contributed a ratiometric fluorescence approach for morin determination between 2.0 and 32 μM, with a limit of detection (LOD) of 45 nM. Meanwhile, under sunlight the color of CQDs-PEI became yellow upon morin addition, which developed a colorimetric method for morin determination in a wide range between 2.0 and 100 μM (LOD = 69 nM). The developed dual-responsive method either displayed accurate results for morin in diluted human and bovine serum, being potential for actual sample analysis. Finally, a visual detection based on the smartphone was constructed and applied for the real-time determination of morin.

Dual-template molecularly surface imprinted polymer on fluorescent metal-organic frameworks functionalized with carbon dots for ascorbic acid and uric acid detection

In this work, dual-template molecularly imprinted polymer surfaces imprinted on blue fluorescent Cr-based MOF (Cr-MOF) functionalized with yellow emissive carbon dots (Y-CDs) were prepared using l-ascorbic acid (AA) and uric acid (UA) as templates for simultaneous selective recognition of AA and UA. The as-prepared nanocomposite probe (Y-CDs/Cr-MOF@MIP) contains two recognition site cavities and emits a dual well-resolved fluorescence spectra when excited at 390 nm; blue emission (λem 450 nm) is due to Cr-MOF, and yellow emission (λem 560 nm) is due to Y-CDs. The yellow fluorescence emission of Y-CDs was quenched upon the addition of ascorbic acid, while Cr-MOF’s emission remained unaffected. In the same way, the blue fluorescence emission of the Cr-MOFs was quenched in the presence of uric acid, while the yellow emission remained constant. Both emissions were quenched in a sample containing both AA and UA. This can be exploited to design a dual-template biosensor to detect UA and AA simultaneously. The Y-CDs/Cr-MOF@MIP sensor displayed a dynamic linear response for AA in the range 25.0 µM – 425.0 µM with a detection limit of 1.30 µM, and for UA in the range 25.0 µM – 425.0 µM with a detection limit of 1.10 µM. The dual-target probe Y-CDs/Cr-MOF@MIP was highly selective and sensitive for the detection of UA and AA in human urine samples due to the selectivity of the two recognition sites.

Rational Design of a Super-Alkali Compound with Reversible Photoluminescence

The zero-dimensional (0D) (H5O2)(C4H14N2S2)2BiCl8: Sb3+ single crystal is obtained by the cooling crystallization method. Surprisingly, this compound shows reversible photoluminescence (PL) upon H5O2+Cl- removal and insertion. To be specific, the release of H5O2+Cl- resulted in red-orange emission with a very low photoluminescence quantum yield (PLQY). While on the reuptake of it, a bright yellow emission with a nearly 10-fold increase of PLQY was observed. Density functional theory (DFT) calculations and temperature-dependent PL experiments reveal that significant [SbCl6]3- octahedron distortion induced by guest (H5O2+Cl-) removal at the ground state, especially at the excited state, is responsible for the disparate PL performance. Encouragingly, we also found that (C4H14N2S2)2BiCl7: Sb3+ exhibits a fast response (<3 s) to dilute hydrochloric acid with naked-eye perceivable PL color changes, rendering it a potential sensing material for hydrochloric acid.

Substituent-Dependent Azide Addition to Isocyanides Generates Strongly Luminescent Iridium Complexes.

Ligand-centered functionalization reactions offer diverse strategies to prepare luminescent organometallic compounds. These compounds can have unique structures that are not accessible via traditional coordination chemistry and can possess enhanced or unusual photophysical properties. Here we show that bis-cyclometalated iridium bis-isocyanide complexes (1) react with azide (N3-) to form novel luminescent structures. The fate of the reaction with azide is determined primarily by the substituent on the aryl isocyanide. Those with electron-withdrawing substituents (CF3 or NO2) react with 1 equiv of azide followed by N2 extrusion, forming aryl cyanamido products (2). With electron-donating groups on the aryl isocyanide the reactivity is more diverse, and three outcomes are possible. In two cases, the isocyanide and azide undergo a [3 + 2] cycloaddition to form a C-bound tetrazolato structure (3). In three other cases, 2 equiv of azide are involved in the formation of a previously unobserved structure, where a tetrazolato and aryl cyanamido couple and rearrange to form a chelating ligand comprised of an N-bound tetrazolato and an acyclic diaminocarbene (4). Finally, a bimetallic aryl cyanamido complex (5) is isolated in one case. All compounds are luminescent, some with exceptional photoluminescence quantum yields as high as 0.81 in solution for sky-blue emission, and 0.87 for yellow emission and 0.65 for orange-red emission in polymer films.

Achievement of full-visible-spectrum lighting in Bi3+-activated strontium gallates via lattice site occupancy engineering toward WLEDs applications

Achieving full-visible-spectrum lighting in a single component is highly desired but still challenging for high-quality phosphor-converted white light emitting diodes (pc-WLEDs). Herein, a broadband emission of Sr3Ga4O9: Bi3+, Yb3+ phosphor covering full-visible-spectrum from 400 to 800 nm is explored via the lattice site occupancy engineering strategy. The Bi3+ singly doped Sr3Ga4O9 phosphor exhibits warm yellow emission for the 3P1→1S0 transition of Bi3+ at Sr1 and Sr3 sites. While the introduction of Yb3+ contributes to the emerge of an extra blue emission band at 445 nm accompanied with a significant enhancement of the integral photoluminescence intensity. It is demonstrated that the chemical substitution of Yb3+ into Sr sites induces the lattice disorder and the increased concentration of Sr vacancies, and the local chemical environment change dominates the occupation of Bi3+ into Sr2 sites, resulting in the remarkable blue emission. Moreover, the WLED device as-fabricated by combining the broadband cyan-emitting Sr3Ga4O9: Bi3+, Yb3+ and the red-emitting CaAlSiN3: Eu2+ phosphors exhibits a high color-rendering index (CRI) of 89.6 and a correlated color temperature (CCT) of 5382 K. This work provides a feasible strategy for regulating the Bi3+occupation in Sr3Ga4O9 matrix and boosts the photoluminescence performance of the corresponding phosphor with broadband emission covering the full visible spectrum.

High‐Efficiency Solid‐State Luminescence from Hydrophilic Carbon Dots with Aggregation‐Induced Emission Characteristics

AbstractCarbon dots (CDs) have excellent properties and have made great progress in synthesis and applications. However, it is still a challenge to realize convenient preparation and highly emissive solid‐state luminescence without the assistance of matrix. In this study, high‐efficiency hydrophilic yellow emissive CDs (Y‐CDs) with aggregation‐induced emission (AIE) characteristics are synthesized by a one‐pot microwave method. Y‐CDs show weak yellow emission with a photoluminescence quantum yield (PLQY) of 6.14% in aqueous solutions, but exhibit a significantly enhanced PLQY of 58.35% in the solid state. The AIE characteristic is confirmed by the phenomenon that the fluorescence emission intensity of Y‐CDs continues to increase with the gradual increase of the poor solvent fraction. The AIE phenomenon of Y‐CDs is derived from the suppression of surface piperazine groups motions and decrease of the non‐radiative rate, as is verified by a series of experiments. Finally, based on the high PLQY and AIE property, Y‐CDs are applied as a color‐converting layer on blue‐light‐emitting chips to fabricate white‐light‐emitting diodes with color coordinates of (0.31, 0.35), while Y‐CDs are also explored for their potential applications in anti‐counterfeiting, encryption and bioimaging.

Zero-dimensional organic–inorganic hybrid zinc halide with broadband yellow light emission

[N-EPD]2ZnBr4produces strong yellow broadband luminescence with a promising quantum yield of 8.28%. This is the first report about yellow light emission in 0D hybrid zinc halides.

Highly efficient yellow emission and abnormal thermal quenching in Mn2+-doped Rb4CdCl6.

In this paper, Mn2+-doped Rb4CdCl6 metal halide single crystals were prepared by a hydrothermal method. The Rb4CdCl6:Mn2+ metal halide exhibits yellow emission with photoluminescence quantum yields (PLQY) as high as 88%. Due to the thermally induced electron detrapping, Rb4CdCl6:Mn2+ also displays good anti-thermal quenching (ATQ) behavior with thermal quenching resistance (131% at 220 °C). The increase in the photoionization and the detrapping of the captured electrons from the shallow trap states were appropriately attributed to this exceptional phenomenon based on thermoluminescence (TL) analysis and density functional theory (DFT) calculations. The relationship between the fluorescence intensity ratio (FIR) of the material and temperature change was further explored using the temperature-dependent fluorescence spectrum. It was used as a temperature measuring probe based on absolute sensitivity (Sa) and relative sensitivity (Sb) with the change in temperature. The phosphor-converted white light emitting diodes (pc-WLEDs) were fabricated using a 460 nm blue chip with a yellow phosphor, which has a color rendering index (CRI = 83.5) and a low correlated color temperature (CCT = 3531 K). Because of this, finding new metal halides with ATQ behavior for high-power optoelectronic applications may be made possible by our findings.

One-pot reaction derived multicolor nitrogen-doped graphene quantum dots for LED applications

Multicolor nitrogen-doped graphene quantum dots (NGQDs) were prepared via one-pot method and purified by column chromatography to obtain three NGQDs with different emission colors, i.e. blue emission (B-NGQDs), cyan emission (C-NGQDs), and yellow emission (Y-NGQDs). The multicolor NGQDs were combined with InGaN chip to fabricate light-emitting diode (LED) that emitted blue, cyan, and yellow light, respectively. Moreover, reducing the amount of Y-NGQDs used could construct a white LED (WLED) with color coordinate of (0.324, 0.334).