Hybrid Amino Acid Ligand-Regulated Excited Dynamics of Highly Luminescent Perovskite Quantum Dots for Bright White Light-Emitting Diodes.

Organic-inorganic hybrid perovskite quantum dots (QDs) have garnered significant research interest owing to their unique structure and optoelectronic properties. However, their poor optical performance in ambient air remains a significant limitation, hindering their advancement and practical applications. Herein, three amino acids (valine, threonine and cysteine) were chosen as surface ligands to successfully prepare highly luminescent CH3NH3PbBr3 (MAPbBr3) QDs. The morphology and XRD results suggest that the inclusion of the amino acid ligands enhances the octahedral structure of the QD solutions. Moreover, the observed blue-shifted phenomenon in the photoluminescence (PL) aligns closely with the blue-shifted phenomenon observed in the ultraviolet-visible (UV-Vis) absorption spectra, attributed to the quantum confinement effect. The time-resolved spectra indicated that the introduction of the amino acid ligands successfully suppressed non-radiative recombination, consequently extending the fluorescence lifetime of the MAPbBr3 QDs. The photoluminescence quantum yields (PLQYs) of the amino acid-treated MAPbBr3 QDs are increased by 94.8%. The color rendering index (CRI) of the produced white light-emitting diode (WLED) is 85.3, with a correlated color temperature (CCT) of 5453 K. Our study presents a novel approach to enhancing the performance of perovskite QDs by employing specially designed surface ligands for surface passivation.

Stability Enhancement in All-Inorganic Perovskite Light Emitting Diodes via Dual Encapsulation.

Addressing the challenge of lighting stability in perovskite white light emitting diodes (WLEDs) is crucial for their commercial viability. CsPbX3 (X = Cl, Br, I, or mixed) nanocrystals (NCs) are promising for next-generation lighting due to their superior optical and electronic properties. However, the inherent soft material structure of CsPbX3 NCs is particularly susceptible to the elevated temperatures associated with prolonged WLED operation. Additionally, these NCs face stability challenges in high humidity environments, leading to reduced lighting performance. This study introduces a two-step dual encapsulation method, resulting in CsPbBr3@SiO2/Al2SiO5 composite fibers (CFs) with enhanced optical stability under extreme conditions. In testing, WLEDs incorporating these CFs, even under prolonged operation at high power (100 mA for 9 h), maintain consistent electroluminescence (EL) intensity and optoelectronic parameters, with surface temperatures reaching 84.2 °C. Crucially, when subjected to 85 °C and 85% relative humidity for 200 h, the WLEDs preserve 97% of their initial fluorescence efficiency. These findings underscore the efficacy of the dual encapsulation strategy in significantly improving perovskite material stability, marking a significant step toward their commercial application in optoelectronic lighting.

Excitation-Selective and Double-Emissive Lead-Free Binary Hybrid Metal Halides for White Light-Emitting Diode and X-Ray Scintillation.

Zero-dimensional (0D) organic metal halides comprising heterogeneous metal cations in single phase can achieve multiple luminous emissions enabling them toward multifunctional light-emitting applications. Herein, A novel single crystal of (C8H20N)4SbMnCl9 containing two luminescent centers of [SbCl5]2- pentahedrons and [MnCl4]2- tetrahedrons is reported. The large distance between Sb-Sb, Mn-Mn, and Sb-Mn as well as theory calculation indicate negligible interaction between individual centers, thus endowing (C8H20N)4SbMnCl9 with excitation-dependable and efficient luminescence. Under near-UV excitation, only orange emission originates from self-trapped excitons recombination in [SbCl5]2- pentahedron occurs with photoluminescence quantum yield (PLQY) of 91.5%. Under blue-light excitation, only green emission originating from 4T1-6A1 transition of Mn2+ in [MnCl4]2- tetrahedrons occurs with PLQY of 66.8%. Interestingly, upon X-ray illumination, both emissions can be fully achieved due to the high-energy photon absorption. Consequently, (C8H20N)4SbMnCl9 is employed as phosphors to fabricate white light-emitting diodes optically pumped by n-UV chip and blue-chip thanks to its excitation-dependable property. Moreover, it also shows promising performance as X-ray scintillator with low detection limit of 60.79 nGyair S-1, steady-state light yield ≈54% of commerical scintillaotr LuAG:Ce, high resolution of 13.5 lp mm-1 for X-ray imaging. This work presents a new structural design to fabricate 0D hybrids with multicolor emissions.

Linkages Make a Difference in the Photoluminescence of Covalent Organic Frameworks.

Covalent organic frameworks (COFs) with structural designability and tunability of photophysical properties enable them to be a promising class of organic luminescent materials by incorporating well-designed fluorescent units directly into the periodic skeletons. The photophysical properties of COFs are mainly affected by the structural features, which determine the conjugation degree, charge delocalization ability, and exciton dynamics of COFs. To understand the relationship between COF structures and their photophysical properties, two COFs with the same pyrene chromophore units but different linkages (imine or vinylene) were designed and synthesized. Interestingly, different linkages endow COFs with huge differences in solid-state photoluminescence quantum yield (PLQY) for imine- and vinylene-linked pyrene-based COFs, which possess PLQY values of 0.34 % and 15.43 %, respectively. The femtosecond-transient absorption spectra and time-dependent density functional theory reveal the different charge-transfer pathways in imine- and vinylene-linked COFs, which influence the exciton relaxation way and fluorescence intensity. In addition, an effective white-light device was obtained by coating the vinylene-linked COF on a light-emitting diode strip.

Highly thermostable mixed lanthanide organic frameworks with high quantum yield for warm white light-emitting diodes.

A mixed lanthanide organic framework was prepared via hydrothermal methods using m-phthalic acid (m-H2BDC), 1,10-phenanthroline (1,10-Phen), and Ln3+ ions, formulated as [HNMe2][Eu0.095Tb1.905(m-BDC)3(phen)2] (ZTU-6). The structure and stability of ZTU-6 were characterised by X-ray diffraction (XRD) and thermogravimetric analysis (TGA), which revealed a three-dimensional pcu topology with high thermal stability. Fluorescence tests showed that ZTU-6 emitted orange light with a high quantum yield of 79.15%, and it can be effectively encapsulated in a light-emitting diode (LED) device emitting orange light. In addition, ZTU-6 was found to be compatible with BaMgAl10O17:Eu2+ (BAM) blue powder and [(Sr,Ba)2SiO4:Eu2+] silicate yellow and green powder to create a warm white LED with a high colour rendering index (CRI) of 93.4, a correlated colour temperature (CCT) of 3908 K, and CIE coordinates of (0.38, 036).

(Sr, Ca)AlSiN3:Eu2+ Phosphor-Doped YAG:Ce3+ Transparent Ceramics as Novel Green-Light-Emitting Materials for White LEDs.

In this work, based on Y3Al5O12:Ce3+ (YAG:Ce3+) transparent ceramic and (Sr, Ca)AlSiN3:Eu2+ phosphors, novel green-light-emitting materials were systematically studied. YAG:Ce3+ transparent ceramics with different doping-concentrations, from 0% to 1% (Sr, Ca)AlSiN3:Eu2+ phosphors, were fabricated by dry pressing and vacuum sintering. The serial phosphor ceramics had 533 nm green-light emission when excited by 460 nm blue light. The PL, PLE, and chromaticity performances were measured, indicating that more of the green-light component was emitted with the increase in doping concentration. The addition of (Sr, Ca)AlSiN3:Eu2+ phosphor increased the green-light wavelength area and improved the quantum yield (QY) of the YAG:Ce3+ ceramic matrix. The phase composition, microstructure, crystal-field structure and phosphor distribution of (Sr, Ca)AlSiN3:Eu2+ phosphor-doped YAG:Ce3+ transparent ceramics were investigated, to explore the microscopic causes of the spectral changes. Impressively, (Sr, Ca)AlSiN3:Eu2+ phosphors were distributed homogeneously, and the pinning effect of phosphor caused the suppression of grain growth. The novel materials could provide an effective strategy for full-spectrum white lighting and displaying applications in the future.

Imperceptible Flicker Noise Reduction Using Pseudo-Flicker Weight Functionalized Derivative Equalization in Light-Fidelity Transmission Link.

A new technique to reduce flicker noise generated in light-fidelity (Li-Fi) transmission links based on the white light-emitting diode (LED) is proposed. Here, flicker noise with a frequency of 120 Hz, which is twice the frequency of AC power (60 Hz), is generated. The proposed technique is implemented in the receiver of the Li-Fi link. It can reduce flicker noise regardless of various digital modulation formats. In addition, there is no need to change the structure of the electrical circuit driving the LED to reduce the flicker noise. As a result, the non-return to-zero-on-off-keying (NRZ-OOK) signal waveform is tilted according to the flicker noise waveform. We implement the derivative equalization with a pseudo-flicker weight function to reduce the flicker noise. The derivative value of the NRZ-OOK signal mixed with flicker noise becomes larger than that without the flicker noise. In the proposed technique, the derivative value between adjacent sampling points is suppressed below the preset thresholds when it is greater than the preset threshold. Furthermore, a pseudo-flicker weight function is applied to accelerate the flicker noise reduction. As a result, using the proposed technique, a 2 dB signal-to-noise ratio (SNR) gain is obtained based on the bit error rate (BER) threshold (3.5 × 10-5) corresponding to 10% flicker modulation, which is known to have no serious effect on human health. This means that it is possible to implement a Li-Fi transmission link based on an illumination environment with a flicker modulation reduced from 10% to 7%.

Automatic Illumination Control Method for Indoor Luminaires Based on Multichromatic Quantum Dot Light-Emitting Diodes.

Energy saving and visual comfort are two main considerations in designing of automatic illumination control systems. However, energy-saving-oriented illumination control always causes optical spectra drifting in light-conversion-material-based white light-emitting diodes (WLEDs), which are conventionally used as artificial luminaires in indoor areas. In this study, we propose a method for InP quantum dot (QD)-based WLEDs to minimize optical energy consumption by considering the influence caused by the outdoor environment and neighboring WLED units. Factors of (a) dimensions of room window and WLED matrix, (b) distance between WLED units, lighting height, species of InP QDs, and (c) user distribution are taken into consideration in calculation. Parameters of correlated color temperature (CCT) and color rendering index (Ra) of the WLED matrix are optimized according to the lighting environment to improve user visual comfort level. By dynamically controlling the light ingredients and optical power of WLEDs, we optimize the received illuminance distribution of table tops, improve the lighting homogeneity of all users, and guarantee the lowest energy consumption of the WLED matrix. The proposed approach can be flexibly applied in large-scale WLED intelligent controlling systems for industrial workshops and office buildings.

Improvement in white light emission of Dy3+doped CaMoO4via Zn2+co-doping.

The research in developing a single ingredient phosphor for white-light emission is progressively increasing. It is well known that the4F9/2 â†’ 6H13/2(yellow) and4F9/2 â†’ 6H15/2(blue) transitions of Dy3+ions give near-white light emission. The white light emission of Dy3+ions can be enhanced via improving the crystallinity of the host phosphor via co-doping of transition metal ions. In this paper, we report a significant improvement in the white light emission of Dy3+doped CaMoO4by co-doping Zn2+ions. The x-ray diffraction pattern confirms the tetragonal phase of pure and doped CaMoO4phosphor. The peak broadening and a red-shift in the absorption peak are observed by UV-vis absorption analysis of Zn2+/Dy3+doped CaMoO4. From Photoluminescence studies, we have observed that in Dy3+doped CaMoO4, the 4% Dy3+doped CaMoO4exhibits maximum emission. The Zn2+ions are co-doped to further increase the luminescence intensity of CaMoO4:4%Dy3+and the maximum luminescence is obtained for 0.25% Zn2+concentration. Two intense emission peaks centered at 484 nm and 574 nm related to transitions4F9/2 â†’ 6H15/2and4F9/2 â†’ 6H13/2of Dy3+ion are observed for Dy3+doped phosphor. The4F9/2 â†’ 6H13/2transition is the forced electric dipole transition which is affected by its chemical environment. After Zn2+co-doping, the4F9/2 â†’ 6H13/2transition is affected due to a change in asymmetricity around the Dy3+ions. The 0.25% co-doping of Zn2+gives 34% enhancement in luminescence emission of 4% Dy3+doped CaMoO4. As a result, the CIE coordinates of chromaticity diagram and the color purity of the 0.25% Zn2+co-doped CaMoO4:4Dy3+show improvement in the overall white light emission. We have shown that with Zn2+co-doping, the non-radiative relaxations are reduced which results in improved white light emission of Dy3+ions.

Sunlike White Light-Emitting Diodes Based on Rare-Earth-Free Luminescent Materials.

Solid-state lighting (SSL) sources based on light-emitting diodes represent the new generation of highly efficient illumination systems that significantly impact energy-saving. The development of white light-emitting diodes (WLEDs) with a combination of high color rendering index (CRI) and high deep-red color rendering R9 is an important challenge in the field of solid-state lighting. On the other hand, most WLEDs use rare-earth inorganic luminescent materials. The annual demand for rare-earth metals has doubled to 125,000 tons in 15 years, and the demand is projected to reach 315,000 tons in 2030. The explosion in demand for these materials, combined with a monopolistic supply source, represents a real risk for the development of WLEDs in the next few years. Luminescent organic materials are a relevant and promising alternative. Here, we report a WLED with a very high CRI of 95.7 and R9 of 78.7, obtained using a combination of a blue LED chip (excitation source) and two organic luminescent dyes (Coumarin 6 and Lumogen Red) acting as spectral converters in a multilayer remote phosphor configuration. To the best of our knowledge, this is the first rare-earth-free WLED with such high values of CRI and R9.

Light Pollution and Circadian Misalignment: A Healthy, Blue-Free, White Light-Emitting Diode to Avoid Chronodisruption.

Sunlight has participated in the development of all life forms on Earth. The micro-world and the daily rhythms of plants and animals are strongly regulated by the light-dark rhythm. Human beings have followed this pattern for thousands of years. The discovery and development of artificial light sources eliminated the workings of this physiological clock. The world's current external environment is full of light pollution. In many electrical light bulbs used today and considered "environmentally friendly," such as LED devices, electrical energy is converted into short-wavelength illumination that we have not experienced in the past. Such illumination effectively becomes "biological light pollution" and disrupts our pineal melatonin production. The suppression of melatonin at night alters our circadian rhythms (biological rhythms with a periodicity of 24 h). This alteration is known as chronodisruption and is associated with numerous diseases. In this article, we present a blue-free WLED (white light-emitting diode) that can avoid chronodisruption and preserve circadian rhythms. This WLED also maintains the spectral quality of light measured through parameters such as CRI (color reproduction index).

Embedded growth of colorful CsPbX3(X = Cl, Br, I) nanocrystals in metal-organic frameworks at Room Temperature.

Herein, we develop a novel strategy for preparing all-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals (NCs)@Zn-based metal-organic framework (MOF) composites through interfacial synthesis. The successful embedding of fluorescent perovskite NCs in Zn-MOFs is due to thein situconfined growth, which is attributed to the re-nucleation of water-triggered phase transformation from Cs4PbBr6to CsPbBr3. The controllable synthesis of mixed-halide based composites with various emission wavelength can be achieved by adding the desired amount of halide (Cl or I) salts in the re-nucleation process. More importantly, the anion exchange reaction is inhibited among various composites with different halogen atoms by being trapped in MOFs. Besides, a white light-emitting diode (WLED) is produced using a blue LED chip with the green-emitting and red-emitting composites, which has a color coordinate of (0.3291, 0.3272) and a wide color gamut. This work provides a novel route to achieving perovskite NCs growth in MOFs, which also can be extended to the other NCs embedded in frames as well.

Melatonin counteracts oxidative damage in lens by regulation of Nrf2 and NLRP3 inflammasome activity.

Oxidative stress, generated because of an imbalance between reactive oxygen species (ROS) generation and elimination, is associated with lens damage and cataract progression. ROS generation is known to activate NLRP3 (nucleotide-binding oligomerization domain-like receptor family, pyrin domain-cointaining 3) inflammasome, and is believed to be an important link between oxidative stress and inflammation, that is also related to cataract development. Potential oxidative hazard to the lens by white light-emitting diode (LED) light, a source of illumination commonly used nowadays, has been suggested, although available information is limited. In this work, we evaluated the cytotoxicity induced by hydrogen peroxide (an oxidative stressor agent) and white LED light in lens epithelial cells as well as melatonin ability to counteract the effects induced by them. Melatonin is a neurohormone secreted by different ocular structures that could be useful to alleviate oxidative damage induced by different oxidative stressors in lens. Particularly, the modulation of Nrf2 (nuclear erythroid 2-related factor)/Keap 1 (Kelch-like ECH-associated protein 1), an essential oxidative stress regulator, and NLRP3 activity by melatonin was evaluated in lens epithelial cells. ROS levels rose after white LED light exposure and cell viability was reduced after challenge with oxidative stressor agents. Melatonin prevented cell death triggered by hydrogen peroxide and white LED light, precluded ROS generation induced by white LED light and promoted antioxidant lens capacity through upregulation of Nrf2 protein levels and SOD activity. NLRP3, caspase-1 and IL1-ß expression significantly increased in human lens cells exposed to H2O2 or irradiated with white LED light. Activation of NLRP3 inflammasome triggered by oxidative stressors was also abrogated by melatonin. Attenuation of inflammatory and cytotoxic effects induced by oxidative stressors provided by melatonin in lens indicate the interest of this molecule as a potential therapeutic agent for cataract prevention/management.

White Light Afterglow in Carbon Dots Achieved via Synergy between the Room-Temperature Phosphorescence and the Delayed Fluorescence.

Carbon dot (CD) based long-lived afterglow emission materials have attracted attention in recent years, but demonstration of white-light room-temperature afterglow remains challenging, due to the difficulty of simultaneous generation of multiple long-lived excited states with distinct chromatic emission. In this work, a white-light room-temperature long-lived afterglow emission from a CD powder with a high efficiency of 5.8% and Commission International de l'Eclairage (CIE) coordinates of (0.396, 0.409) is realized. The afterglow of the CDs originates from a synergy between the phosphorescence of the carbon core and the delayed fluorescence associated with the surface CN moieties, which is accomplished by matching the singlet state of the surface groups of the CDs with the long-lived triplet state of the carbon core, resulting in an efficient energy transfer. It is demonstrated how the long-lived afterglow emission of CDs can be utilized for fabrication of white light emitting devices and in anticounterfeiting applications.

Multi-Emission from Single Metal-Organic Frameworks under Single Excitation.

Multi-emission materials have come to prominent attention ascribed to their extended applications other than single-emission ones. General and robust design strategies of a single matrix with multi-emission under single excitation are urgently required. Metal-organic frameworks (MOFs) are porous materials prepared with organic ligands and metal nodes. The variety of metal nodes and ligands makes MOFs with great superiority as multi-emission matrices. Guest species encapsulated into the channels or pores of MOFs are the additional emission sites for multi-emission. In this review, multi-emission MOFs according to the different excitation sites are summarized and classified. The emission mechanisms are discussed, such as antenna effect, excited-state intramolecular proton transfer (ESIPT) and tautomerism for dual-emission. The factors that affect the emissions are revealed, including ligand-metal energy transfer and host-guest interaction, etc. Multi-emission MOFs could be predictably designed and prepared, once the emissive factors are controlled rationally in combination with the different multi-emission mechanisms. Correspondingly, new and practical applications are realized, including but not limited to ratiometric/multi-target sensing and bioimaging, white light-emitting diodes, and anti-counterfeiting. The design strategies of multi-emission MOFs and their extensive applications are reviewed. The results will shed light on other multi-emission systems to develop the structure-derived functionality and applications.

Efficient Perovskite White Light-Emitting Diode Based on an Interfacial Charge-Confinement Structure.

Perovskite light-emitting diodes (LEDs) show great potential for next-generation lighting and display technology. Despite intensive studies on single-color devices, there are few reports on perovskite-based white LEDs (Pe-WLEDs). Here, an efficient Pe-WLED based on a blue perovskite and an orange phosphorescent emitter is reported for the first time. It is found that using a simple perovskite/phosphor bilayer emitting structure, there is inefficient energy transfer from the blue perovskite to the orange phosphor, leading to low efficiency and a significant color shift with driving voltage. We address this issue by introducing a quantum-well-like charge-confinement structure for enhancing carrier trapping and thus exciton formation in the phosphorescent emitter. As a result, a high external quantum efficiency of 10.81% is obtained. More interestingly, by tuning the dopant concentration of the phosphorescent emitter using this simple device structure, we can controllably get Pe-WLEDs with very stable white light for display applications or tunable color from warm white to daylight for lighting applications.

Alloyed Green-Emitting CdZnSeS/ZnS Quantum Dots with Dense Protective Layers for Stable Lighting and Display Applications.

Alloyed green-emitting CdZnSeS/ZnS quantum dots (QDs) demonstrate potential applications in solid-state lighting and displays owing to their various advantages, such as high color purity, light conversion efficiency, and color rendering index. However, their applications in white light-emitting diodes (WLEDs) are limited by their poor photostabilities on blue-emitting gallium nitride (GaN) LED chips. In this study, the effect of the specific surface area (SSA) in the coating layers on the photostabilities of QDs was investigated. SSA was adjusted by controlling the proportions of dense aluminum oxide (AlOX) layers and porous silica dioxide (SiO2) layers to fabricate QD protective layers via a catalyst-free sol-gel method. The results showed that the synthesized AlOX possessing the lowest SSA among the synthesis protective layers presented the best QD photostabilities on the LED chips. Moreover, they exhibited a 9.9-fold increase in the operational lifetime (T80) compared to that of pristine QDs. In addition, the QD-based WLED achieved an excellent display performance with a wide color gamut (115%) of the National Television System Committee (NTSC) color gamut standard. This approach offers a promising strategy for enhancing the QD photostabilities for applications in solid-state lighting and displays by coating the protective layers on the QD surface.

Modulation of aqueous humor melatonin levels by yellow-filter and its protective effect on lens.

Melatonin is mainly secreted by the pineal gland, and it is also produced by various ocular structures such as the lens. It has been recently demonstrated that melatonin ocular synthesis can be induced by blocking the blue component of white light by means of filters. Melatonin exhibits antioxidant properties that can be useful to face light-induced oxidative stress as well as oxidative events associated to ocular pathologies like cataracts. Moreover, as oxidative stress is a main event in cataract development, changes in melatonin levels could happen and be relevant in the progression of this pathology, a subject that remains uncertain. The goal of this work was to analyze the ability of a short wavelength light blocking (yellow) filter to modulate endogenous melatonin concentration and the antioxidant and cytoprotective actions induced by yellow filter's use in lens. Furthermore, we evaluated the potential changes in aqueous humor melatonin concentration from patients with cataracts. In human lens epithelial cells, white light-emitting diode (LED) light challenge reduced melatonin secretion, protein levels of the enzymes involved in melatonin synthesis (hydroxyindole-O-methyltransferase and unphosphorylated and phosphorylated forms of arylalkylamine N-acetyltransferase) and cell viability whereas increased reactive oxygen species production. Yellow filter exposure precluded melatonin secretion reduction and protected cells from oxidative damage. Consistent with cataract patient's results, significantly lower levels of melatonin were observed in aqueous humor of alloxan-induced diabetic cataract rabbits as compared to those of control rabbits. In contrast, aqueous humor melatonin levels of diabetic cataract animals maintaining in cages covered with a yellow filter resembled control values. This recovery seems to be mediated by the induction of melatonin biosynthetic enzymes protein expression. Yellow filter also preserved Nrf2 lens protein expression and superoxide dismutase protein levels and activity in diabetic animals. Modulation of endogenous ocular melatonin concentration using blocking filters might be a promising approach to prevent premature lens opacification.

Recent advances in process engineering and upcoming applications of metal-organic frameworks.

Progress in metal-organic frameworks (MOFs) has advanced from fundamental chemistry to engineering processes and applications, resulting in new industrial opportunities. The unique features of MOFs, such as their permanent porosity, high surface area, and structural flexibility, continue to draw industrial interest outside the traditional MOF field, both to solve existing challenges and to create new businesses. In this context, diverse research has been directed toward commercializing MOFs, but such studies have been performed according to a variety of individual goals. Therefore, there have been limited opportunities to share the challenges, goals, and findings with most of the MOF field. In this review, we examine the issues and demands for MOF commercialization and investigate recent advances in MOF process engineering and applications. Specifically, we discuss the criteria for MOF commercialization from the views of stability, producibility, regulations, and production cost. This review covers progress in the mass production and formation of MOFs along with future applications that are not currently well known but have high potential for new areas of MOF commercialization.

Color inconstancy of natural teeth measured under white light-emitting diode illuminants.

OBJECTIVE: To evaluate color and whiteness changes of natural teeth under nine white LED illuminants recently proposed by CIE. METHODS: From spectral reflectance factors of 36 caries-free upper central incisors, corresponding colors under illuminant D65 and CIE 1931 standard colorimetric observer were computed for all tested illuminants, using the chromatic adaptation transform CAT16. Color differences (CIELAB and CIEDE2000 units) and whiteness (WID and WIO indices) from teeth illuminated by CIE standard illuminants (D65 and A) and white LED illuminants were calculated. The appearance of 630 pairs of teeth under all illuminants was also evaluated. RESULTS: Color gamuts from 36 teeth under tested illuminants showed similar volume and shape in CIELAB color space, but their centers of gravity changed in many different directions with respect to colors under D65 or A illuminants: Considering colors under D65/A, color shifts produced by white LED illuminants were in the ranges 2.0-8.6/1.1-7.0 CIELAB units (1.4-8.2/0.6-6.8 CIEDE2000 units). Average WID and WIO values for the 36 teeth under different illuminants ranged from -5.8 to +19.3 and from -7.7 to +11.1, respectively. Considering 630 pairs of teeth, average color differences (mainly lightness differences) were below 0.5 CIELAB units (0.3 CIEDE2000 units), and average whiteness differences ranged from 8.1 to 10.7 for WID (23.4-25.1 for WIO). SIGNIFICANCE: Using CIE LED illuminants, most changes in color and whiteness for individual teeth were above typical threshold values of perceptibility and acceptability in dentistry. However, considering pairs of teeth, the average color and whiteness differences under all tested illuminants were very similar.