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Facile, Gram-Scale and Eco-friendly Synthesis of Multi-Color Graphene Quantum Dots by Thermal-Driven Advanced Oxidation Process
摘要： Graphene quantum dots (GQDs) have been demonstrated of great potential and benefits in the fields of bioimaging and white light-emitting-diodes (WLEDs). However, it is still highly demanding at the current level to solve the dilemma of achieving high-yield GQDs of good quality and superior fluorescent property using low-cost sustainable and industrializable production procedure. In this work, we for the first time report the gram-scale synthesis of well-crystalline GQDs with ultra-small size based on thermal-driven Advanced Oxidation Process (AOP) under facile green hydrothermal conditions. The average yield calculated from 20 trials reached up to 60%, and the average size of the dots was measured to be ~3.7 nm. Furtherly, GQDs with the photoluminescence (PL) emission of blue, green, yellow, orange, and red have been prepared by expanding the π-conjugation and introducing graphite nitrogen in the carbon skeleton based on chemical structure engineering. The PL-tunable GQDs have an average size distribution of 2~5 nm and a lamellar structure of 2~6 layers. Structure analysis results have indicated that the red shift of PL emission is attributed to bandgap narrowing. This approach successfully converts the easily available and cheap precursor into high-valued products with great application potentials. The PL-tunable GQDs have been successfully used as fluorescent probes of good biocompatibility for in vitro/ in vivo bio-imaging and to produce highly-photostable white-light-emitting composite film with a quantum yield (QY) of 24%.
关键词： Gram-scale synthesis,White light-emitting-diodes,Photoluminescence,Bioimaging,Advanced Oxidation Process,Graphene quantum dots
更新于2025-09-19 17:13:59
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Highly Efficient Cyan-Green Emission in Self-Activated Rb <sub/>3</sub> RV <sub/>2</sub> O <sub/>8</sub> (R = Y, Lu) Vanadate Phosphors for Full-Spectrum White Light-Emitting Diodes (LEDs)
摘要： Phosphor-converted white-light-emitting diodes (pc-WLEDs) rely on combining a near-ultraviolet (n-UV) or blue chip with trichromatic and yellow-emitting phosphors. It is challenging to discover cyan-green-emitting (480?520 nm) phosphors for compensating the spectral gap and producing full-spectrum white light. In this work, we successfully discovered two unprecedented bright cyan-green emitting Rb3RV2O8 (R = Y, Lu) phosphors that gives emission bands centered at 500 nm upon 362 nm n-UV light excitation. Interestingly, the both self-activated compounds exhibit high internal quantum e?ciencies (IQEs) of 71% for Rb3YV2O8 and 85% for Rb3LuV2O8, respectively. Moreover, controllable emission color can be successfully tuned from cyan-green to orange-red across the warm white light region by design strategy of VO4 3? → Eu3+ energy transfer. The thermal quenching of as-prepared phosphors could be e?ectively mitigated by this design strategy. Finally, the as-fabricated n-UV (λ ex = 370 nm) pumped phosphor-converted (pc) W-LED devices utilizing Rb3RV2O8 (R = Y, Lu) along with commercial phosphors demonstrate well-distributed warm white light with high color-rendering index (CRI) of 91.9 and 93.5, and a low correlated color temperature (CCT) of 5095 and 4946 K. It suggests that the both vanadate phosphors have potential applications in full-spectrum pc-WLEDs.
关键词： cyan-green emission,self-activated,full-spectrum white light-emitting diodes,energy transfer,vanadate phosphors
更新于2025-09-19 17:13:59
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Highly Elastic and >200% Reversibly Stretchable Downa??Conversion White Lighta??Emitting Diodes Based on Quantum Dot Gel Emitters
摘要： Combining the characteristics of different materials offers exciting new opportunities for advanced applications in various fields. Herein, white light-emitting diodes (WLEDs) with >200% reversible stretchability are fabricated using six-color quantum dots (QDs) gel emitters. Stable aqueous-phase alloy core/shell QDs with high quantum yield are obtained via ligand exchange using a ternary solvent system. Transparent and highly stretchable gels with large pores are created by binary-solvent-based gelation at low temperatures. Importantly, the QDs and the gel originate from the same two solvents, which make the QDs highly compatible with the gelation process. Consequently, QDs of six different colors are incorporated into the gel without any property degradation. The excellent optical properties of the QDs in the liquid phase (e.g., 17% higher photoluminescence (PL) intensity) are retained in the gel phase. The QD gel (QDG) exhibits elastic deformation up to 200%, with uniform PL over the entire gel. A down-conversion WLED built using the QDG emitter produces cool white light with a color temperature of 6100 K, a color rendering index of 94, and a luminous efficacy of 72 lm W?1. In addition, the performance of the QDG-based WLED remains unchanged even after more than 1000 bending/stretching cycles.
关键词： white light emitting diodes,gels,mechanical reliability,form factors,quantum dots
更新于2025-09-19 17:13:59
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Ca(Mg <sub/>0.8</sub> Al <sub/>0.2</sub> )(Si <sub/>1.8</sub> Al <sub/>0.2</sub> )O <sub/>6</sub> :Ce <sup>3+</sup> ,Tb <sup>3+</sup> Phosphors: Structure Control, Density-Functional Theory Calculation, and Luminescence Property for pc-wLED Application
摘要： A modified structure Ca(Mg0.8Al0.2)(Si1.8Al0.2)O6 (denoted as CMASO) from the evolution of CaMgSi2O6 (denoted as CMSO) codoped with Ce3+ and Tb3+ ions was designed successfully by solid reaction method for application in phosphor-converted white-light-emitting diode (pc-wLED). The Rietveld refinement of these two structures verified the changes derived from the replacement of some of the Mg2+ and Si4+ ions by Al3+ ions. The band gaps were calculated by density-functional theory (DFT) calculation method to verify the change of Al3+ ions replacing further, and the diffuse reflectance spectra (DRS) proved the veracity of the calculation result. The phosphors CMASO:Ce3+ showed blue emission excited by a wider excitation wavelength from 280 nm to 370 nm. The change of structure lead to the absorbable range broaden and the emission peak shifted to longer wavelength, compared with CMSO:Ce3+, although the amount of emitting center was the same. The reason for these phenomena was discussed in detail. The codoped phosphors CMASO:Ce3+,Tb3+ exhibited different emission colors from blue to green as the concentration of Tb3+ ions increased. Combined with commercial red phosphor CaAlSiN3:Eu2+ and ultraviolet LED (UV-LED) chips, the selected appropriate samples achieved white emission. The correlated color temperature (CCT) was 6137 K and the color rendering index (Ra) was 80.5, indicating that they could act as potential phosphors for possible applications in pc-wLED.
关键词： Ce3+,pc-wLED,DFT,luminescence property,Tb3+,Ca(Mg0.8Al0.2)(Si1.8Al0.2)O6,phosphor-converted white-light-emitting diode,density-functional theory
更新于2025-09-19 17:13:59
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Facile Preparation of Stable Solid-State Carbon Quantum Dots with Multi-Peak Emission
摘要： Aggregation-caused quenching (ACQ) effect, known as the main cause to restrain solid-state luminescence of carbon quantum dots (CQDs), hinders further application of CQDs in white light-emitting diodes (WLED). Here, a complex of CQDs and phthalimide crystals (CQDs/PC) was prepared through a one-step solvothermal method. CQDs/PC prevented CQDs from touching directly by embedding the CQDs in phthalimide crystal matrix in situ, which effectively reduced the ACQ effect. Furthermore, CQDs/PC exhibited multi-peak fluorescence spectra that span the green, yellow and orange spectral regions. Finally, a WLED fabricated based on CQDs/PC achieved a color-rendering index of 82 and a correlated color temperature of 5430 K. This work provides a quick and effective strategy to apply CQDs to WLED.
关键词： solid-state luminescence,multi-peak emission,yellow carbon quantum dots,white light-emitting diode
更新于2025-09-19 17:13:59
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Preparation of CdTe superparticles for white light-emitting diodes without F?rster resonance energy transfer
摘要： Due to many unique and excellent optical properties, quantum dots (QDs) have been seen as one of the most promising color conversion materials in light-emitting diodes (LEDs). However, the F¨orster resonance energy transfer (FRET) among di?erent colored QDs always causes a signi?cant red-shift of the ?uorescence emission, impeding the fabrication of LEDs with predicted photoluminescence (PL) emission spectra. In this work, we take advantage of CdTe superparticles (SPs), which are assembled by CdTe QDs, as the color conversion materials for the fabrication of WLEDs. Because of their submicron size, the distance between QDs with di?erent emissions can be large enough to avoid the FRET process. More importantly, this method provides us with an opportunity to precisely design and regulate the PL emission spectra of LEDs. By easily overlapping the individual PL spectra of CdTe SPs with di?erent emissions, the certain ratio of their usage for fabricating LEDs with desired PL emission spectra is identi?ed. According to this idea, a WLED with a color rendering index (CRI) of 81, luminous e?cacy of 27 lm W(cid:1)1, and color coordinate at (0.33, 0.34) with the color temperature of 5742 K is achieved.
关键词： F¨orster resonance energy transfer,white light-emitting diodes,quantum dots,color conversion materials,CdTe superparticles
更新于2025-09-16 10:30:52
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A simple and green synthesis of carbon quantum dots from coke for white light-emitting devices
摘要： Coke is a by-product of coal. This paper reports a simple and green chemical oxidation method for carbon quantum dots (CQDs) from coke for use in novel applications. The CQDs emit blue fluorescence and have a fluorescence quantum yield of 9.2% and blue-green-red spectral composition of 48%. A light-emitting diode (LED) was fabricated by combining the CQDs as a white-light converter with an ultraviolet chip. The Commission Internationale de L'Eclairage chromaticity coordinate (0.31, 0.35) and correlated color temperature (5125 K) of the LED are located in a cool white light zone, suggesting that they have superior potential application in lighting devices.
关键词： carbon quantum dots,white light-emitting devices,fluorescence,coke,chemical oxidation
更新于2025-09-16 10:30:52
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Bright emission and high photoluminescence CsPb <sub/>2</sub> Br <sub/>5</sub> NCs encapsulated in mesoporous silica with ultrahigh stability and excellent optical properties for white light-emitting diodes
摘要： All-inorganic cesium lead halide perovskite CsPb2Br5 nanocrystals (NCs) have attracted tremendous attention owing to their unique optoelectronic properties. However, their tolerance to atmospheric moisture is limited by their corresponding poor stability, which has drastically prevented the broad application of the materials in lasers, light-emitting diodes (LED) and, most recently, photocatalysis. To address this issue, we have successfully demonstrated the design and synthesis of a nanocomposite material, CsPb2Br5 NCs coated in mesoporous silica (NCs-MS), with high photoluminescence (PL) intensity, bright emission and enhanced water stability, thermal stability and photostability versus naked CsPb2Br5 NCs. The components and structure of the prepared CsPb2Br5 NCs-MS nanocomposite were investigated in detail by PL, XRD, TEM and HAADF-STEM studies. Furthermore, the mechanism behind the outstanding stability and optical properties of the prepared NCs-MS nanocomposite is discussed. Owing to the ultrahigh stability of the NCs-MS nanocomposite, the white LED (WLED) assembled by coating the CsPb2Br5 NCs-MS nanocomposite and commercial red CaAlSiN3:Eu2+ phosphor powder on an InGaN blue chip showed CIE chromaticity coordinates of (0.3377, 0.3309) and presented excellent optical parameters with a CRI of 82.9, a CCT of 5035 K and an LE of 64.9 lm W?1. This work provides a new pathway for the synthesis and application of all-inorganic cesium lead halide perovskite materials in WLEDs and display devices.
关键词： stability,white light-emitting diodes,mesoporous silica,photoluminescence,CsPb2Br5 NCs
更新于2025-09-16 10:30:52
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A novel multi-center activated single-component white light-emitting phosphor for deep UV chip-based high color-rendering WLEDs
摘要： Single-component white light-emitting phosphors for phosphors-converted WLEDs are a hot spot of solid-state lighting field. Dy3+ is a promising candidate for white light generation in single-component hosts; however, the inappropriate ratio of yellow light to blue and the lack of red light restrict its applications in full-color display and indoor lighting. Here, a novel multi-center activated single-component white light-emitting phosphor, Sr2LaGaO5:Dy3+,Sm3+, has been designed and synthesized. It is surprisingly found that there is no evident energy transfer between the host and the dopants even though they satisfy the rule of spectral overlap, which can be explained from the special structure of the phosphor. The co-excitation of the host and the dopants would be a facile strategy to finely tune the luminescent spectra of phosphors. By adjusting the doping concentrations of Dy3+ and Sm3+, we can control the relative intensities of the emissions peaked at 493 nm and 574 nm from Dy3+, 604 nm from Sm3+ and the broadband within the range of 400 - 500 nm from the host. Therefore, the emission color of the co-doped phosphors can be tuned from white light to orangish red region with correlated color temperature decreasing from 5708 K to 1971 K. A WLED device with extremely high color-rendering index (Ra) up to 91.4 was fabricated by coating the synthesized phosphor with a deep UV LED chip. And it is the first time to use a single-component white light-emitting phosphor co-activated with Dy3+ and Sm3+ in deep UV chip excited WLEDs with high Ra.
关键词： Co-excitation,Sr2LaGaO5:Dy3+,Sm3+,Deep UV-LED chip,White light-emitting phosphor,High color-rendering index
更新于2025-09-16 10:30:52
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White-light/tunable emissions in single-phased BaLa2Si3O10:Eu3+, Bi3+ phosphor for the simultaneous applications in white light-emitting diodes and luminous cement
摘要： In this work, we report the single-phased BaLa2Si3O10:Eu3+, Bi3+ phosphor with white-light/tunable emissions under UV excitations. We find the emissions of Bi3+-doped BaLa2Si3O10 samples are dependent on the excitation spectral wavelength, where exciting by the wavelength from 240 to 410 nm range can lead to the tunable Bi3+ emissions owing to the intensity change of three emission bands (i.e., 367 nm, 423 nm, and 516 nm). After co-doping the Eu3+ ions into Bi3+-doped BaLa2Si3O10, the energy transfer from Bi3+ to Eu3+ ions dominated by a dipole–quadrupole (d–q) interaction mechanism is proved. Typically, by exciting with 365 nm and varying the Eu3+ content, the tunable emissions from blue, white to red are observable in the BaLa2Si3O10:Eu3+, Bi3+. By coating the white BaLa2Si3O10:Eu3+, Bi3+ sample with a commercial 365-nm UV LED chip or mixing it with the cement, we not only achieve the white-light LEDs device with the desirable color rendering index (CRI) of 95, excellent luminescent efficiency of 80 lm/W, and good excellent color temperature (CT) of 4215 K at the CIE chromaticity of (0.338, 0.357), but also achieve the luminous cement.
关键词： white light-emitting diodes,single-phased phosphor,white-light/tunable emissions,luminous cement,BaLa2Si3O10:Eu3+,Bi3+
更新于2025-09-12 10:27:22