High CRI Research Articles

Cellulose nanocrystal extraction from tissue paper wastes using different extraction methods and cellulose acetate production

ABSTRACT This paper examines the feasibility of extracting cellulose from tissue paper wastes (TPW’s) using several methods: sonication (SC), subcritical (SU), microwave (MC), and microwave with diluted acid (MA). The chemical characterisation and morphological properties of nanocrystal cellulose were investigated using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and scanning electron microscopy with energy dispersive X-Ray analysis (SEM-EDX). TPW’s have a relatively high crystallinity index (CrI = 61.02%). It was found to be lower than that for cellulose extracted using SU and SC MC, MA methods, where CrI to 65.65%, 68.07%, 69.21% and 73.42%, respectively. The MA method yielded cellulose with the highest CrI and altered surface morphology. This cellulose was selected for cellulose acetate synthesis. After acetylation, the CrI decreased to 61.45%, and the morphological aspect was changed. In conclusion, nanocrystal cellulose was successfully extracted from TPW’s and effectively changed to its esterified form.

High thermally stable and efficient rare-earth celsian by phase transformation of Ba2+-Exchanged SOD zeolite

The white LEDs with high performance and excellent luminous quality is of high importance for developing the current lighting industry, and high thermally stable blue phosphors play a critical role in the preparation of white LEDs. Herein, we reported a facile way to obtain highly efficient blue Eu2+-doped celsian phosphor with excellent thermal stability by a phase transformation of Ba2+-exchanged SOD Zeolite strategy. The structure of phosphors changed from nepheline to celsian with the doping of Ba2+, and the maximum emission intensity blue-shifts from 550 nm to 450 nm under the excitation of 370 nm. The PLQY is determined to be 56 %, 96 % and 82 % for the phosphor with Ba2+ doping concentration being 0, 1.49 and 1.86, respectively, and the luminescence intensity at 423 K is can be 80 %, 102 % and 93 % of its intensity at room temperature. Finally, the package of the LED device based on our yellow and blue phosphors together with the commercial red CaAlSiN3:Eu2+ phosphor is constructed to show warm white light with the CCT of 3705 K and a high CRI of 97.7. This study provides a facile way for obtaining satisfactory phosphors for high-quality lighting.

Novel White Phosphor Bi3+ co-doped SrCeO3: 2 wt% Sm3+ Synthesized via Fuel Excess Gel Combustion Synthesis for wLED Applications.

Co-doping strategy is done if the emission from the activator is relatively low with existing excitation energy. Thus, to enrich the emission from an activator, the sensitizer like Bi3+ is co-doped onto the host and this intermediator transfers its emission energy to the activator. Prior to the study, no investigations had been conducted, marking the foundational exploration of the sensitizer effect within the rare earth-doped SrCeO3 matrix aimed at enhancing luminescence properties. The current study focuses on the innovation of single-phase robust white phosphors, SrCeO3: 2wt% Sm3+: xBi3+ (x = 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%) to coat near UV LED chips for high CRI wLED applications. The novel perovskites were synthesized using a low-temperature fuel excess gel combustion method, utilizing citric acid as the fuel and ammonium nitrate as an extra oxidizer. Upon co-doping SrCeO3: 2wt% Sm3+ with bismuth, the impact of changing sensitizer concentration on both the development of crystalline phases, morphology, elemental composition, band gap energy, and the luminescent properties of ceramic powders were explored through X-ray diffraction, FE-SEM, Energy dispersive spectra, UV-visible absorption spectra, and photoluminescence characterization methods. The experimental results revealed the orthorhombic single-phase formation of SrCeO3: 2wt% Sm3+: xBi3+perovskites yielding high crystallinity and luminescence maximum at critical sensitizer concentration 1 wt% Bi3+. Also, the bright white light emission of all the perovskites was confirmed using the CIE color diagram. Thus, nano-perovskite SrCe0.97Sm0.02O3: 1wt% Bi3+ acts as an inevitable direct phosphor coating the near UV chip in LEDs, which can be a great revolution in energy savings applications.

A novel orange-red emitting K5Y(MoO4)4:Sm3+ phosphor with excellent color purity for temperature sensing and high CRI WLEDs

The novel orange-red emitting K5Y(MoO4)4:xSm3+ (KYMO:xSm3+) (1 mol% ≤ x ≤ 35 mol%) phosphors were synthesized through solid-phase reaction. The KYMO:Sm3+ phosphors were mainly analyzed for purity phase, luminescence properties, and thermostability. Under 403 nm excitation, KYMO:10 mol%Sm3+ possesses four distinct emission peaks. The dominant emission peak is situated at 645 nm, corresponding to the 4G5/2 → 6H7/2 electron transitions. With x = 10 mol%, the KYMO:xSm3+ phosphor has the optimal doping concentration. The color purity reaches as high as 99.9 %. KYMO:10 mol%Sm3+ presents good thermostability with T0.5 > 480 K and resistance to color drift (ΔE = 0.012 at 420 K). The lifetime for KYMO:10 mol%Sm3+ is 1.16 ms. The internal quantum efficiency (IQE) reaches 62.74 %. At 480 K, the maximum temperature sensing sensitivities of the FIR of I564/I599 are 5.19 × 10−4 (Sa) and 18 % (Sr). The assembled WLED displays an excellent color rendering index (CRI, Ra) of 94, Commission International de L′ Eclairage (CIE) coordinates (0.333, 0.346), and a correlated color temperature (CCT) of 5464 K. In summary, KYMO:Sm3+ phosphors possess great promise for high CRI white-light-emitting diodes (WLEDs) and potential feasibility for temperature sensing.

Phosphor Ceramic Composite for Tunable Warm White Light.

Composite phosphor ceramics for warm white LED lighting were fabricated with K2SiF6:Mn4+ (KSF) as both a narrowband red phosphor and a translucent matrix in which yellow-emitting Y3Al5O12:Ce3+ (YAG) particles were dispersed. The emission spectra of these composites under blue LED excitation were studied as a function of YAG loading and thickness. Warm white light with a color temperature of 2716 K, a high CRI of 92.6, and an R9 of 77.6 was achieved. A modest improvement in the thermal conductivity of the KSF ceramic of up to 9% was observed with the addition of YAG particles. In addition, a simple model was developed for predicting the emission spectra based on several parameters of the composite ceramics and validated with the experimental results. The emission spectrum can be tuned by varying the dopant concentrations, thickness, YAG loading, and YAG particle size. This work demonstrates the utility of KSF/YAG composite phosphor ceramics as a means of producing warm white light, which are potentially suitable for higher-drive applications due to their increased thermal conductivity and reduced droop compared with silicone-dispersed phosphor powders.

Efficient white light-emitting electrochemical cells based on quantum-dot color conversion layers with high EQE >20 %

Solid-state light-emitting electrochemical cells (LECs) offer promising benefits, including simple device architecture, low operating voltage, and insensitivity to electrode work functions. These advantages make them highly suitable for low-cost display and lighting applications, with significant potential for widespread adoption. However, great challenges remain in realizing stable and efficient white LECs. In this work, the blue LECs integrated with red or yellow/red quantum-dot (QD) color conversion layers (CCLs) are shown to achieve efficient and stable white emissions. When the blue LECs are combined with red QD CCLs, they achieve an external quantum efficiency (EQE) exceeding 20 % at a low current density of 0.003 mA cm−2. Alternatively, the blue LECs integrated with yellow/red QD CCLs deliver white emissions with a low CCT <2500 K and a high CRI up to 93 while the peak EQE at a low current density of 0.005 mA cm−2 still remains high (>16 %). The data effectively showcase that efficient and stable white emission can be achieved through partial energy down-conversion from the blue LECs to the QD CCLs, and the proposed white light sources are potential candidates for lighting applications.

Binary Host-induced Exciplex Enabled High Color-Rendering Index of 94 for Carbon Quantum Dot-Based White Light-Emitting Diodes.

White light-emitting diodes (WLEDs) with high color-rendering index (CRI, >90) are important for backlight displays and solid-state lighting applications. Although the well-developed colloidal quantum dots (QDs) based on heavy metals such as cadmium and lead are promising candidates for WLEDs, the low CRI still remains a significant limitation. In addition, the severe toxicity of heavy metals greatly limits their widespread use. Herein, the study demonstrates low-cost and environmentally friendly carbon quantum dots (CQDs)-based WLEDs that exhibit a high CRI of 94.33, surpassing that of conventional cadmium/lead-containing QD-based WLEDs. This achievement is attained through the employment of a binary host-induced exciplex strategy. The high hole/electron mobility and suitable energy levels of the donor and acceptor give rise to a broadband orange-yellow emission stemming from the exciplex. As the host, the binary exciplex is capable of contributing blue and orange-yellow emission components while efficiently mitigating the aggregation-induced quenching of CQDs. Meanwhile, CQDs effectively address the deep-red emission gap, enabling the realization of CQDs-based WLEDs with high CRI. These WLEDs also exhibit a remarkably low turn-on voltage of 2.8V, a maximum luminance exceeding 2000cd m- 2, a correlated color temperature of 4976 K, and Commission Internationale de l'Eclairage coordinates of (0.34, 0.32).

High-Color-Rendition White QLEDs by Balancing Red, Green and Blue Centres in Eco-Friendly ZnCuGaS:In@ZnS Quantum Dots.

White light-emitting diodes (WLEDs) are the key components in the next-generation lighting and display devices. The inherent toxicity of Cd/Pb-based quantum dots (QDs) limits the further application in WLEDs. Recently, more attention is focused on eco-friendly QDs and their WLEDs, especially the phosphor-free WLEDs based on mono-component, which profits from bias-insensitive color stability. However, the imbalanced carrier distribution between red-green-blue luminescent centers, even the absence of a certain luminescent center, hinders their balanced and stable photoluminescence/electroluminescence (PL/EL). Here, an In3+-doped strategy in Zn-Cu-Ga-S@ZnS QDs is first proposed, and the balanced carrier distribution is realized by non-equivalent substitution and In3+ doping concentration modulation. The alleviation of the green emitter by the In3+-related red emitter and the compensation of blue emitter by the Zn-related electronic states contribute to the balanced red-green-blue emitting with high PL quantum yield (PLQY) of 95.3% and long lifetime (T90) of over 1100 h in atmospheric conditions. Thus, the In3+-doped WLEDs can achieve exceedingly slight proportional variations between red-green-blue EL intensity over time (∆CIE = (0.007, 0.009)), and high champion CRI of 94.9. This study proposes a single-component QD with balanced and stable red-green-blue PL/EL spectrum, meeting the requirements of lighting and display.

Application of Artificial Intelligence in Stimulating Plant Growth Using Electric Lighting

This paper highlights the role of artificial intelligence (AI) in electric lighting for enhancing smart agriculture. The use of electric lighting in greenhouses is widely practiced in the present time, as sunlight is poorly available in some parts of the world. Different plants have different growth in different spectrum of light. The spectrum of light in which the plant grows maximum is coined as optimum growth spectrum (OGS). Hence, this study aims to choose artificial intelligence in assessing the optimum spectrum of light for a given plant. RGB based LEDs are used and its luminous efficacy is interpreted, considering different blend of mechanisms and the yield current and temperature. Rapid light fluctuations offered by pulse amplitude modulation causes a loss in the output of the LEDs. Hence, there lies a finite gap in the light provided and the light reaching the plant. Since, LEDs are the source of light here, hence, light sources complying with higher CRI should be deployed, as used in this experiment. The overall system was so designed such that when a plant is cultivated, using image processing, AI identifies the specific plant and implements all the available data, like the optimum growth spectrum, temperature, humidity, etc. The experiment clearly emphasizes on the results which were impressive. The OGS of the given plant has been figured out and trained the system through AI to execute the growth functions for the given plant.

Optimizing the White Light Emission of Pr3+ Activated SrCeO3 Perovskite by Controlling the Excitation Wavelength for High CRI wLED Applications.

The current research illustrates excitation energy-triggered photoluminescent characteristics of Pr3+ions in SrCeO3 providing a practical approach for developing high CRI wLED and its applications. SrCeO3: xPr3+ (x = 0, 0.005, 0.01, 0.02, 0.03 wt) perovskites synthesized by fuel excess gel combustion method generate high CRI (~98) for wLED applications. Crystalline phosphors with orthorhombic structures having space group Pnma were confirmed by XRD. The unit cell volume expansion occurred with an increase in Pr3+ concentration was verified through the Rietveld refinement technique. Surface morphology, particle distribution, and size were observed via FE-SEM imaging, and detected a well-defined regular distorted spherical structure with average grain size 0.826μm for Pr3+ doped SrCeO3. Elemental mapping and EDS analysis identified the uniform distribution and elemental purity of SrCeO3: 0.01 Pr3+. Further, the molecular vibrations and modes were analyzed from the Raman spectrum. Moreover, the average particle size assessed via TEM analysis was found to be ~83.2nm, consistent with XRD analysis. UV-visible absorption spectra for optical energy-band gap analysis showed a decrease in band gap energy with an increase in Pr3+ concentration, realizing an effective energy transfer from Ce4+ to Pr3+. PL measurements showed a huge variety of emission transitions, corresponding to excitations 290nm, 321nm, 373nm, and 449nm. The critical dopant concentration instigated by concentration quenching was 1 wt% Pr3+, ascribed to dipole-dipole interaction. The fluorescence lifetime of the optimal sample was 4.835μs. Commission International de I'Eclairage (CIE) diagram exposes the white light emanation of SrCeO3: Pr3+. Among which white light with high CRI (~98) and comparably low CCT (~6311K) was obtained for SrCeO3: 0.01 Pr3+ at 373nm excitation. The obtained results recommend that SrCeO3: Pr3+ perovskite as an efficient white phosphor for fabricating high-performance wLEDs.

Mn4+-activated (K1-xCsx)2NbF7 red phosphors with high color purity and excellent moisture resistance for WLEDs

Recently, Mn4+-activated fluoride red phosphors have received intensive attention due to their excellent luminescence properties. However, poor moisture resistance hinders their commercial application. Herein, (K1-xCsx)2NbF7:Mn4+ phosphors were designed and synthesized. All the obtained samples are rod-like microcrystals with monoclinic phase structure, Cs+-doping concentration has little influence on the microstructure while significantly impacts their luminescence properties. Specially, the composition optimized (K1-xCsx)2NbF7:Mn4+ (x = 0.3) phosphor has the color purity of 94.20 %, the quantum yield of 53.90 % and the decay lifetime of 3.59 ms. More importantly, the optimized phosphor can maintain 83.20 % of the initial emission intensity after being immersed in distilled water for 1440 min, showing the excellent moisture resistance. A warm WLED with high CRI of 85 and low CCT of 4362 K is achieved by coating the obtained optimized red phosphor in chip. Our work demonstrates that the (K1-xCsx)2NbF7:Mn4+red phosphors possess a great potential application in warm WLEDs.

Unravelling the white light emission in the single-phase new stochiometric vanadate phosphor synthesized by the rapid low-temperature one-pot synthesis and its W-LED prototype with high CRI and luminous efficacy

A vacancy-activated intrinsic white light emitting phosphor- a new stoichiometric single-phase Ba3V4O13, has been synthesized by rapid and efficient microwave synthesis in 15 min at 200ºC. The phosphor exhibits long-range...

Performance Evaluation of Low Attracting Insects between Sunlight Type LEDs, High CRI LEDs and White LEDs

Performance Evaluation of Low Attracting Insects between Sunlight Type LEDs, High CRI LEDs and White LEDs

Enhancement of photoluminescence quantum yield in lead-free inorganic copper based halide perovskites via zinc doping

Zn doped Cs3Cu2Cl5 exhibited green luminesce with an enhanced photoluminescence quantum yield (PLQY) (70.19%), nearly twice the PLQY of Cs3Cu2Cl5. The corresponding WLED exhibits high CRI (95.8) and suitable CCT (4573 K).

Thermally-stable AlN-based green and red composite ceramic phosphor wheel for LD lighting with high CRI

Phosphor conversion materials with excellent thermal stability and broad-spectrum is critical to obtaining laser lighting devices with high luminous flux and CRI. In this paper, high thermally stable green AlN-Lu3Al5O12:Ce (ASL) and red AlN–CaAlSiN3:Eu (ASR) composite phosphor ceramics were prepared by embedding phosphor into AlN ceramic matrix. With mass ratio of phosphor increasing, luminescence intensity and quantum efficiency gradually increased, and the maximum internal quantum efficiency reached 62.8 % and 78.9 % for ASL and ASR, respectively. Under laser exciting in reflection mode, ASL-20 and ASR-50 got the max luminous emittance of 2827.5 lm/mm2 and 268.7 lm/mm2 with a saturation laser power density of 60.4 W/mm2 and 16.7 W/mm2, respectively. The diffusion coefficient of Ca, Al, Si between AlN and CASN grains was 2–4 magnitude higher than that of Lu, O, N between AlN and LuAG grains, confirming facile solid solubility of AlN and CASN. Finally, luminescence performances of green-red color wheel fabricated by ASL and ASR were evaluated. When the area ratio of green to red was 2:1, the color wheel yielded the biggest CRI of 82.6. This work presents a facile strategy for fabricating high thermally stable AlN-based composite phosphor ceramic and its application in high-quality laser lighting and display devices.

Screening and characterization of Bacillus thuringiensis isolates for high production of Vip3A and Cry proteins and high thermostability to control Spodoptera spp

Bacillus thuringiensis (Bt) is an entomopathogenic bacterium that produces crystalline (Cry and Cyt) and soluble (vegetative insecticidal proteins or Vips) proteins during the sporulation and vegetative growth phases, respectively. Combining Cry and Vip proteins could delay insect resistance development and exhibit synergistic activity against various insect pests. This study aims to screen Bt isolates collected from Thailand for high Vip3A and Cry protein production levels and high thermostability to control Spodoptera spp. Among the selected Bt isolates with high target protein synthesis, Bt isolate 506 was found to be safe for further biopesticide formulation due to the absence of non-specific metabolite, as determined by the detection of thermo-stable β-exotoxin I based on biological assays and PCR analysis. Bt isolate 506 showed the presence of Cry1A, Cry2A, and Vip3A-type proteins identified as Cry1Aa45, Cry2Aa22, and Vip3A87, respectively. The insecticidal activity of whole culture extracts containing Vip3A and Cry mixtures and culture supernatants containing secreted Vip3A protein was evaluated against the second-instar larvae of S. exigua and S. frugiperda. The Bt isolate 506 showed high toxicity against both insects, and the insecticidal proteins produced by this isolate retained their activity after heating at 50 °C. This Bt isolate is a promising candidate for further development as a biopesticide against lepidopteran pests.

Evaluating the Phosphorescence duration of Zn2P2O7 glass–ceramic activated by Dy3+/Pr3+ for LED applications

The present study focuses on investigating the phosphorescence efficiency of binary zinc–phosphate glasses co-doped with dysprosium and/or praseodymium oxides together with their corresponding glass ceramics. The studied glass series was prepared directly by the conventional melting and quenching method. Differential thermal analysis (DTA) indicated an exothermic peak at 550 °C that was applied to yield glass-ceramic samples. The major monoclinic phase of Zn2P2O7 was detected by X-ray diffraction (XRD). FTIR and SEM–EDAX were applied to identify the structural morphology of the prepared samples. The optical efficiency was characterized through UV–Visible–NIR absorption spectra and photoluminescence analysis. Both light emissions and their corresponding lifetimes were enhanced significantly in glass–ceramic. These samples display high CRI, low color temperature, and CIE values comparable to those expected for pure white-light and warm yellow emitting diodes.

The developments of cyan emitting phosphors to fulfill the cyan emission gap of white-LEDs.

Future generations of solid-state lighting (SSL) will prioritize the development of innovative luminescent materials with superior characteristics. The phosphors converted into white light-emitting diodes (white LEDs) often have a blue-green cavity. Cyan-emitting phosphor fills the spectral gap and produces "full-visible-spectrum lighting." Full-visible spectrum lighting is beneficial for several purposes, such as light therapy, plant growth, and promoting an active and healthy lifestyle. The design of cyan garnet-type phosphors, like Ca2LuHf2Al3O12 (CLHAO), has recently been the subject of interest. This review study reports a useful cyan-emitting phosphor based on CLHAO composition with a garnet structure to have a cyan-to-green emitting color with good energy transfer. It could be employed as cyan filler in warm-white LED manufacturing. Due to its stability, ability to dope with various ions suitable for their desired qualities, and ease of synthesis, this garnet-like compound is a great host material for rare-earth ions. The development of CLHAO cyan-emitting phosphors has exceptionally high luminescence, resulting in high CRI and warm-white LEDs, making them a viable desire for LED manufacturing. The development of CLHAO cyan-emitting phosphors with diverse synthesis techniques, along with their properties and applications in white LEDs, are extensively covered in this review paper.

A double perovskite structure Ca2InTaO6:Sm3+ orange-red phosphor with high thermal stability for high CRI w-LEDs and plant growth lighting

A novel Sm3+-doped Ca2InTaO6 (CITO:Sm3+) phosphor was produced through a high-temperature solid-state reaction. The Rietveld refinement of the CITO:Sm3+ phosphors were carried out, and its successful synthesis was demonstrated. The phosphor is a member of the Pnma space group (No.62) and features a double perovskite structure. The excitation spectrum of CITO:5 mol%Sm3+ revealed a suitable excitation at 407 nm. The emission spectrum exhibited four distinct peaks. The most intense emission peak is at 601 nm, attributed to the 4G5/2-6H7/2 radiative transition of Sm3+ ions. The emission spectra at different doping concentrations indicated the optical doping concentration of 5 mol%. Dipole-dipole interactions are the reason for the concentration quenching. The internal and external quantum efficiency of CITO:5 mol%Sm3+ is 73.52 % and 38.73 %, respectively. In the range of 300–480 K, CITO:5 mol%Sm3+ phosphor demonstrated high thermal stability and had almost no thermal quenching phenomenon. The CITO:5 mol%Sm3+ phosphor has an activation energy (Ea) of 0.289 eV. The electroluminescence spectra of the fabricated orange-red light-emitting diode (LED) can match the absorption spectra of PR, PFR, chlorophyll b, phycocyanin, and allophycocyanin. The white LED (w-LED) prepared with this phosphor has Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.339, 0.331) and a correlated color temperature of 5184 K, as well as an excellent color rendering index (Ra = 94). These indicate the promising usage of CITO:Sm3+ in plant-growth and w-LED illumination.

Comparative investigation on luminescence properties of red-emitting KLiSnF6:Mn4+ phosphors and the fluorescent sheet for high-power LEDs

New red-emitting phosphors KLiSnF6:xMn4+ (KLSFM, x = 4%, 6%, 8%, 10%, and 12%) for LED lighting were synthesized by an ion-exchange method at room temperature. Among these phosphors, the KLSFM (8 mol%) sample exhibits the strongest excitation in the blue region and emission in the red region. The corresponding translucent fluorescent sheet prepared by the pressure method shows similar luminescent properties which are identical to the powders with the strongest absorption at 467 nm and narrow emission around 632 nm. The fluorescent sheet offers high transmittance in UV–Vis region (close to 100% beyond 550 nm) and better thermal stability and color stability. For comparison, the white pc-LEDs based on the KLSFM (8 mol%) phosphor and fluorescent sheet all emit intense white light with an ideal color rendering index (CRI >93) and a good correlated color temperature (CCT <3500 K). However, the white pc-LED based on the fluorescent sheet have more advantage in application for high-power devices. Working at 200 mA, the LED fabricated with the translucent sheet still keeps excellent performance with a high CRI of 90.1 and a low CCT of 3874 K. The working temperature for this device is only 90 °C after working for 40 min, which is lower than that of the device with the KLSFM (8 mol%) powder, furtherly proving that the translucent sheet has excellent heat dispersion. Therefore, the KLSFM (8 mol%) translucent sheet could be used for high-power pc-LEDs as a red component.