Luminous Color Research Articles

Tunable luminous color of LEDs achieved through integrating reliable multilevel RRAM

We developed a color-modulated light-emitting device (LED) by the integration of a p-GaN/n-ZnO heterojunction with reliable resistive random access memory (RRAM) and demonstrated a multi-function integrated device with the adjustable electroluminescence (EL) color by modulating the injection current according to the multiple resistance states. As a critical foundation of an integrated device, reliable operation was achieved by introducing an AlOx layer into HfOx RRAM as an adjustment of the resistive switching endurance. Eventually, the EL color of LED was effectively regulated by modulating the compliance current of RRAM. Thanks to the high uniformity, this modulated LED may be a promising candidate for the application of low-cost and high-density LED displays without complicated structures and techniques, and it can provide a feasible approach for the realization of multilevel resistance state feedback from varied EL color in the future.

Thermal response color-tunable electroluminescent device for real-time visual temperature monitoring

Alternating current electroluminescent (ACEL) devices have attracted tremendous attention due to their significant applications in bioinspired electronics, smart wearables, and human-machine interfaces. However, it still faces limitations in real-time visual temperature sensing. Herein, a universal strategy is established to achieve real-time temperature dynamic visualization by integrating a thermochromic layer through a simple spin coating procedure. Such elaborate integration permits the device to display a wide array of luminous colors and achieve high-contrast color transitions in response to ambient temperature variations. More importantly, a quantitative relationship can be established between the temperatures and the luminous color changes. This advancement not only enhances multi-color emission capabilities but also enables the display of diverse information, marking a significant stride in the development of dynamic temperature sensing in ACEL devices.

신분증 OCR 인식 확률을 높일 수 있는 인공조명환경 연구

While the number of uses for ID(Identification) OCR(Optical Character Recognition) is increasing and the scope of its use is increasing, it has limitations in increasing the probability due to the problem of not being able to controlexternal conditions. The feedback currently being provided is not scientific, so it is unable to provide appropriate guidance to users. This study created a formula to avoid veiling reflection, which is the main cause of poor OCR, and allowed the angle of lighting to be adjusted according to the distance between the ID card and the camera. In addition, the BRDF(Bidirectional Reflectance Distribution Function) of the ID card was measured and simulated, and the point where the color luminance contrast was greatest was presented at an angle of 36 degrees between the light and the ID card, and this was verified in an actual situation. Through this, points where OCR can be good in an artificial lighting environment were presented in a scientific way, and machine learning was additionally conducted to provide a way for users to conveniently find places with a high OCR probability.

Characterization of GaN‐Based Nanopillar Light‐Emitting Diodes on Multicrystalline Si Substrates: Insights into Emitting‐Color Distribution Characteristics

In a previous study, GaN‐based nanopillars are grown vertically on a multicrystalline Si substrate by inserting (In)GaN steering crystals. In addition, blue‐green and white light‐emitting diodes (LEDs) are prepared on this substrate for the first time using a double heterotype p–n junction. Herein, the emission‐color distribution characteristics of this type of LED are analyzed in depth, and a related luminescence principle is proposed. Each nanopillar plus an electrode is considered a nanopillar LED, and the emission color of each nanopillar LED is inferred. The indium distribution in the InGaN active region is predicted based on the luminous color and corresponding spectra. Simultaneously, the morphology of related materials, electrical properties of LEDs, and chromaticity coordinates of luminous colors are analyzed and discussed.

Effects of Rare-Earth Elements Doping on Micro-Structure and Fluorescence Performances of Fluorapatite

For purposes of optimizing the microstructure and fluorescence properties of rare-earth elements (REEs)-doped fluorapatites (FAps), various kinds of REEs (La, Pr, Sm, Eu, Gd, Ho, Er, and Yb) with the concentration of 2~20 mol.% have been inserted into the FAps framework via hydrothermal method, in order to investigate the influential mechanism of the REEs on the crystal structure, morphology, and fluorescence under the excitation of the near-ultraviolet light of the FAps. Experimental results show that the wavelength of the emitted light of the REEs-doped FAps is decided by the type of REEs. Unlike the Pr/Yb- and Ho-doped FAps and with the fluorescence of red and green emitted light, respectively, the Er-doped FAps show a blue light emission with wavelengths of 296, 401, and 505 nm, which is, moreover, different with the Eu-doped Faps, showing an orange light emission with wavelengths of 490, 594, and 697 nm. The emission luminous color is related to the lattice defects of the FAps doped with the various types and the effective doping concentration of the REEs. The luminous intensity increases with the increase in the effective doping concentration of the REEs. Nevertheless, the formation of rare-earth fluoride results in the decrease in the effective doping concentration of the REEs and the luminous intensity. The FAps with an effective doping concentration of 7 mol.% Er and 3 mol.% Eu show relative excellent fluorescence properties.

Mechanofluorochromic Properties of 1,4-Diphenylanthracene Derivatives with Hypsochromic Shift.

Several types of 1,4-diphenylanthracene derivatives 1-4 were prepared, and their photophysical properties were observed in the solid and solution states. Interestingly, the CN-group-substituted 1,4-diphenylanthracene derivative 2 was found to exhibit a higher fluorescence quantum yield (ϕf = 0.71) in the solid state than in the solution state, probably due to the formation of an intermolecular Ar-CN⋯H-Ar hydrogen bond and antiparallel type locked packing structure in the solid state. Furthermore, for some derivatives, an increase in the fluorescence quantum yield was observed in the PMMA film (1 wt%) over both the solid state and the solution state. More interestingly, some of the 1,4-diphenylanthracene derivatives exhibited unusual mechanofluorochromic properties with a "hypsochromic shift" in luminous color depending on the substituents of the phenyl group, and with the derivatives having CF3, OMe, CN, and two F substituents (1d-1f, 2-4) showing a significant luminous color change with a "hypsochromic shift" after grinding. However, no change in the luminous color was observed for the derivatives having H, Me, and one F substituent (1a-1c), and especially for some of the CN-substituted derivatives, a reversible luminous color change with a "hypsochromic shift" was observed, probably due to the formation of an antiparallel type packing structure. These "hypsochromic" anthracene derivatives could probably be utilized as new mechanofluorochromic materials.

Preparation and luminescence properties of Tb3+-Sm3+ co-doped K3Gd(PO4)2 crystalline glass ceramics

In this paper, Tb3+-Sm3+ co-doped glass ceramics with K3Gd(PO4)2 crystal phase were successfully prepared by methods of melting curing crystallization. The optimal heat treatment conditions for the samples were determined to be held for 1.5 h at 750 °C by combining differential scanning calorimeter (DSC), x-ray diffraction (XRD) and scanning electron microscope (SEM). Under this condition, glass ceramics still have a high transmittance in the range of 400∼700 nm, up to 80 %. It was calculated that the optical band gap value of glass ceramic is smaller than that of glass, indicating that the sample structure was changed by heat treatment. Fluorescence lifetime and Dexter's theory demonstrate that Tb3+ transfers energy to Sm3+. By fixing the concentration of Tb3+ and changing the doping concentration of Sm3+, the luminous color of glass ceramics can be adjusted. At 458 K, the fluorescence intensity of Tb3+ and Sm3+ decreased to 89 % and 85 % of that at 298 K. Study shows that the prepared glass ceramics have potential applications in white light emitting diodes (WLEDs).

A study on the analysis and understanding of art works based on graph neural networks

Abstract With the development of the Internet, many art works are uploaded for people to enjoy. To make it more convenient for viewers to understand and analyze the content of art works. In this paper, we use the GNN graph neural network analysis model to extract the art style, creation period, color expression and other features of the works through the work feature saliency attention module, and classify them using the similarity metric. At the same time, we put forward the GNNMMVisRe model to explore the works from the visual multimodality. The analysis results concluded that the Impressionist style of art works had its heyday in the 18th-19th centuries, when the number of works reached 11,674. The Baroque classicism style reached its heyday in the mid-18th century with 5,921 pieces. In terms of color use, low saturation and low luminance color palettes were selected, with average values of 81.3% and 83.4%, respectively. Using the GNN model to categorize, analyze and study the art works improves the understanding and appreciation of the works. It is also significant for the further development of art.

Spatial Intelligent Design and Innovation for Indoor Environment - Visualization and Analysis of Web3D Technology

Abstract Along with the popularization and expanding influence of Internet applications, Web 3D is born from various mature technologies driven by the demand for commercial interests in the Internet. This study designs an interactive intelligent design method for indoor environment space based on Web 3D, which has cross-platform and high-performance graphic drawing capability and covers indoor lighting material transformation, smooth switching of viewpoints, zooming of areas, and other interactive modes. It has cross-platform and high-performance graphic drawing capabilities and covers indoor lighting material change, smooth switching of viewpoints, area zoom, and other features. Based on the visual perception characteristics of the human eye, we obtain the user’s most realistic experience of the color of the indoor space and then construct the virtual indoor environmental space through the Web 3D system, and carry out a visual analysis of the indoor space under different materials and colors. The results show that under the visual analysis of Web 3D, the optimal distribution of color luminance values affecting the visual psychology of indoor environmental space is between 30.5 and 68.9nit, with a mean value of 49.59nit. The results can establish a favorable basis for the later indoor color configuration, which is in line with the visual characteristics of the human eye in indoor color configuration design practice.

Electroluminescence, Mechanoluminescence, and Triboelectric from Superior Multimode Systems Based on Flexible Hydrogels for Human Motion Sensing

AbstractFlexible sensors have attracted extensive research interest due to their great application potential in biodetection, flexible display, and wearable devices. However, they still have a lot of room for improvement in terms of luminous color, flexibility, and self‐powered systems. A wearable, antifreeze, and discoloration sensing system based on electroluminescence, mechanoluminescence, and tribo‐power generation is developed in this paper. Triboelectric nanogenerator systems can harvest biomechanical energy from hand clapping and knee/elbow bending to generate real‐time electrical signals. The use of dielectric materials reduces the initial voltage and frequency of light‐emitting devices, enabling them to be driven by Triboelectric nanogenerators. At the same time, the device can produce red, blue, white, and other multicolor light. In addition, the system can produce an optical signal output due to external mechanical stimulation. As a result, the sensor system is simple to manufacture and unique to operate, proving its potential applications in areas such as cold‐resistant displays, wearable optoelectronics, soft robotics, and electronic skin.

Synthesis of Multicolor Carbon Dots Catalyzed by Inorganic Salts with Tunable Nonlinear Optical Properties.

The nonlinear optical properties of carbon dots have been in the spotlight in recent years. In light of the complexity and diversity of factors affecting the nonlinear optical properties of carbon dots, how to reveal the origin and physical mechanism of the nonlinear optical properties of carbon dots accurately has become a problem. In this work, a template-free method was designed to prepare carbon dots via solid-phase reaction with phloroglucinol as a single carbon source and sodium bisulfate as the catalyst. This method is simple, green, safe, and easy to be prepared on a large scale. Three carbon dots with different luminous colors were obtained by simply adjusting the reaction temperature. The rise of reaction temperature affects the surface functional groups, and then hinders the luminescence of surface states, leading to the change of luminescence properties. The nonlinear optical properties of carbon dots were analyzed by the Z-scan technique. Surprisingly, all carbon dots have nonlinear optical responses, but there are differences in performance. Results prove the increase in sp2 domains may contribute to the significant improvement of the nonlinear optical properties of carbon dots, indicating a direction to improve the nonlinear optical properties of carbon dots.

Thermally Reversible Luminescence in Ferroelastic Phase Transition Materials

AbstractThe thermally reversible luminescent materials with information encryption are important and widely used in the information age. However, it is challenging to obtain such materials. In this work, a 0D In‐based hybrid compound [(CH3)3NCH2CHCH2]2InCl5 ((TAMAC)2InCl5) is synthesized and undergoes a high‐temperature ferroelastic phase transition with an Aizu notation of mmF2/m at 333 K. In the room temperature phase (RTP), it shows a weak blue glow with a photoluminescent quantum yield (PLQY) of 0.32% under the UV lamp at 365 nm. By using a metal ion doping strategy to improve the photophysical properties, a series of compounds is obtained: (TAMAC)2In1‐xCl5:xSb3+ (x = 0.1%,0.5%,1%, and 1.5%, x represents the actual amount) with the same ferroelastic phase transition as that found in (TAMAC)2InCl5. When x = 0.5%, the PLQY reaches 50.66% with the luminous color change from blue to orange. Interestingly, it is found that the orange luminescence of the doped materials can rapidly and reversibly quench and recover between heating and cooling cycles, where the thermally induced phase transition results in this thermally reversible luminescence phenomenon. This discovery reveals the mechanism of luminescence quenching and phase transition, and provides a new pathway for the construction of new thermal‐sensitive luminescent materials with information encryption.

Excitation Wavelength‐Dependent Fluorescence of a Lanthanide Organic Metal Halide Cluster for Anti‐Counterfeiting Applications

AbstractThe achievement of significant photoluminescence (PL) in lanthanide ions (Ln3+) has primarily relied on host sensitization, where energy is transferred from the excited host material to the Ln3+ ions. However, this luminous mechanism involves only one optical antenna, namely the host material, which limits the accessibility of excitation wavelength‐dependent (Ex‐De) PL. Consequently, the wider application of Ln3+ ions in light‐emitting devices is hindered. In this study, we present an organic–inorganic compound, (DMA)4LnCl7 (DMA+=[CH3NH2CH3]+, Ln3+=Ce3+, Tb3+), which serves as an independent host lattice material for efficient Ex‐De emission by doping it with trivalent antimony (Sb3+). The pristine (DMA)4LnCl7 compounds exhibit high luminescence, maintaining the characteristic sharp emission bands of Ln3+ and demonstrating a high PL quantum yield of 90–100 %. Upon Sb3+ doping, the compound exhibits noticeable Ex‐De emission with switchable colors. Through a detailed spectral study, we observe that the prominent energy transfer process observed in traditional host‐sensitized systems is absent in these materials. Instead, they exhibit two independent emission centers from Ln3+ and Sb3+, each displaying distinct features in luminous color and radiative lifetime. These findings open up new possibilities for designing Ex‐De emitters based on Ln3+ ions.

Mechanofluorochromic properties of 1-phenylanthracene derivatives with extremely simple structures

Several types of 1-phenylanthracene derivatives 1–4 were prepared and their photophysical properties were observed in the solution and solid states. Interestingly, the fluorine-substituted 1-phenylanthracene derivative 1c was found to exhibit a higher fluorescence quantum yield (Φf=0.57) in the solid state than in the solution state, probably due to the formation of intermolecular Ar–F•••H–Ar hydrogen bonds. Additionally, some of the 1-phenylanthracene derivatives exhibited mechanofluorochromic properties depending on the substituents of the phenyl group, with the derivatives having CF3, OMe, and CN substituents (1d-1f, 2, 3) showing a significant change in luminous color from a bluish to greenish color at “room temperature” after grinding. However, no change in the luminous color was observed for the derivatives having H, Me, and F substituents (1a-1c) at “room temperature” but luminous color change was observed with low temperature grinding (−78 °C), especially for the CN substituent, in which a significant change in the luminous color was observed at “room temperature” probably due to the formation of Ar-CN•••H–Ar hydorogen bond interactions. Interestingly, for the 1-phenylanthracene derivative 3 substituted with two CN groups, which exhibited a solvatochromic phenomenon, the luminous color recovered with controllable rate from green to bluish when heated and fumed with solvent vapor in the solid state, and the luminous color change with controllable recovery rate was repeatedly successfully observed. These anthracene derivatives have extremely simple structures and could probably be applied as new mechanofluorochromic materials.

Eu3+ doped CaWO4 nanophosphor for high sensitivity optical thermometry

Eu3+ doped calcium tungstate phosphors were obtained by using sodium citrate as chelating agent in hydrothermal process. The structure and morphology of the samples were indicated by XRD and the FE-SEM. The samples prepared by us are scheelite structure. In addition, the particle size of sample decreases with sodium citrate dosage increasing, and finally reaches the nanoscale. The average particle size is 90 nm. The temperature measurement properties of phosphors were tested. It can be seen from test results that the thermal quenching behavior of Eu3+ and WO42- luminescence has obvious difference. Hence, the FIR of Eu3+ and WO42- can be used to express temperature. The maximum relative sensitivity increases with the decrease of particle size and the maximum is 4.3% K−1 (303 K, 90 nm). Moreover, the color of sample luminescence altered continuously from blue to pink-red as the temperature increased. The luminous color of the sample can be used to roughly estimate the temperature. Therefore, the CaWO4: Eu3+ nanophosphor are promising materials for optical thermometry.

Synthesis of a lanthanide-based bimetallic-metal-organic framework for luminescence sensing anthrax biomarker

Lanthanide luminescence sensors have attracted extensive attention in the detection of 2, 6-pyridinedicarboxylic acid (DPA), the main biomarker of anthrax. In previous reports detecting DPA, luminescence probes may not have high selectivity and high specificity for identification. In the present study, a highly specific and sensitive luminescence probe was synthesized. In this paper, [TbxGd1-x (PBA)2NO3·2H2O]n is synthesized by solvothermal method using HPBA = 3.5-bis(triazol-1-yl)benzoic acid and Ln (NO3)3·6H2O (Ln = Tb, Gd). Through modulating the molar ratio of Tb3+ ions and Gd3+ ions, the distance between Ln3+ ions is changed, leading to a change in the energy transfer from the ligand to Tb3+, which in turn leads to an increase in luminescence intensity. Meanwhile the luminous colour is regulated by the ratio of Tb/Gd, which changes from green to white as the Gd ion gradually increases. The bimetallic ratiometric luminescence sensor realized accurate, high sensitivity (LOD is 1.03 × 10−6 M) and high selectivity detection of DPA. Due to the simple synthesis method and low technical requirements, this work provides a good strategy for the development of simple and effective bimetallic ratiometric luminescence sensors.

Facilely Direct Construction, White-Light Emission, and Color-Adjustable Luminescence of LaF3 :Pr3+ @SiO2 Yolk-Shell Nanospheres with Moisture Resistance.

Poor water stability and single luminous color are the major drawbacks of the most phosphors reported. Therefore, it is important to realize multicolor luminescence in a phosphor with single host and single activator as well as moisture resistance. LaF3 :Pr3+ @SiO2 yolk-shell nanospheres are facilely obtained by a designing new technology of a simple and cost-effective electrospray ionization combined with a dicrucible fluorating technique without using protective gas. In addition, tunable photoluminescence, especially white-light emission, is successfully obtained in LaF3 :Pr3+ @SiO2 yolk-shell nanospheres by adjusting Pr3+ ion concentrations, and the luminescence mechanism of Pr3+ ion is advanced. Compared with the counterpart LaF3 :Pr3+ nanospheres, the water stability of LaF3 :Pr3+ @SiO2 yolk-shell nanospheres is improved by 15% after immersion in water for 72h, and the fluorescence intensity can be maintained at 86% of the initial intensity. Furthermore, by treating the yolk-shell nanospheres with hydrofluoric acid, it is not only demonstrated that the shell-layer is SiO2 but also core-LaF3 :Pr3+ nanospheres are obtained. Particularly, only fluorination procedure among the halogenation can produce such special yolk-shell nanospheres, the formation mechanism of yolk-shell nanospheres is proposed detailedly based on the sound experiments and a corresponding new technology is built. These findings broaden practical applications of LaF3 :Pr3+ @SiO2 yolk-shell nanospheres.

FAPbBr3@PbBr(OH) phosphor with high stability for anti-counterfeiting application via water induction

Organic–inorganic hybrid perovskite nanocrystals have become a very widely used as semiconductor light-emitting materials. However, perovskite nanocrystals face stability challenges, which is a key factor hindering their application. In this paper, by introducing water into the synthesis of formamidinium lead bromide (FAPbBr3) perovskite, ultra-stable FAPbBr3@PbBr(OH) fluorescent material was prepared. The photoluminescence intensity of the material after the addition of water increased 2.9 times compared with that before the addition of water. The excellent green fluorescence emission was still maintained after four cycles of wash–dry treatment. Meanwhile, it also exhibits good ultraviolet and thermal stability. The above enhanced performance of FAPbBr3 nanocrystals is attributed the protection of PbBr(OH). In addition, the prepared material can be used in anti-counterfeit patterns. The anti-counterfeit patterns have good color rendering and the luminous color has a high dependence on temperature. Both of these features make it very valuable for various fluorescent anti-counterfeiting labels.

Optimal Design of Multilayer Optical Color Filters for Building‐Integrated Photovoltaic (BIPV) Applications

Herein, the application of a comprehensive modeling framework that can help optimize the design of multilayered optical filters for coloring photovoltaic (PV) modules is presented based on crystalline silicon solar cells. To overcome technical issues related to the implementation of color filters (CFs) on PV modules, like glare and color instability, colorimetry metrics, such as the hue, chroma, luminance color space, and the quantitative concept of difference between two colors are extensively deployed. It is showcased in this work that designing colored modules with high hue and chroma stability is possible by using a front‐side texturing with edged geometry, like V‐shaped grooves and inverted pyramids, while obtaining colors with relatively high luminance values, indicating good brightness. Furthermore, it is argued that adapting the rear surface of the front glass with a random textured layout where the CF is applied can improve color and luminance stability without significant loss of chroma while eliminating glare. Finally, the models can be used to optimize the number of layers for a given CF, reducing unnecessary optical losses. Compared to a standard PV module, performance simulation of optimized, bright‐colored PV modules predicts relative energy yield losses ranging from 7% to 25%.

HPLC–HR-ESI–MS/MS identification of fluorescent dyes and optical brighteners and their degradation products in daylight fluorescent paints

Daylight fluorescent paints are luminous colors that are increasingly used in contemporary art. The pigments consist of a synthetic resin in which fluorescent dyes and optical brighteners are embedded. In the recent years, several research articles have been published on the composition of daylight fluorescent pigments. Despite the growing research on the aging behavior of daylight fluorescent paints, little is known to date about the chemical processes involved in aging. In the research presented here, we used dialysis to separate the colorants from the resin. HPLC–HR-ESI–MS/MS was used to extend the elucidation of the dye composition. A variety of rhodamines and coumarins, an aminonaphthalimide dye and another optical brightener were determined. NMR was used to elucidate the structure of an additional hemicyanine dye not listed in the Colour Index. Furthermore, reference substances were artificially aged under visible light and UV radiation and the degradation products were analyzed accordingly. N-deethylation, hydroxylation and higher oxidation processes were found to be the main degradation pathways for all colorants. For most dyes and optical brighteners, there was no difference between aging under visible light and aging under UV radiation. When the results were checked on samples of aged paint mock-ups, it was found that only a few of the degradation products can still be detected in the case of very advanced aging even with the smallest sample quantities.