Compact pupil-expansion AR-HUD based on surface-relief grating.

Augmented reality head-up display (AR-HUD) using diffractive waveguide is a challenging research field. It can drastically reduce the system volume compared with AR-HUD based on freeform mirror. However, one of the remaining challenges that affects the performance of the diffractive waveguide is to expand the eye-box while maintaining the illuminance uniformity. In this paper, a one-dimensional pupil expansion diffractive optical waveguide system for AR-HUD is presented. The optimization of grating parameters is based on scalar diffraction theory and rigorous coupled wave analysis (RCWA). Then, the illuminance uniformity is optimized through non-sequential ray tracing. We simulate and construct a waveguide-based AR-HUD. The presented AR-HUD realized an exit pupil size of 80 mm × 15 mm and a field of view of 10° × 5° at the wavelength of 532 nm.

Uniform nucleation and growth of Cs3Cu2I5 nanocrystals with high luminous efficiency and structural stability and their application in white light-emitting diodes.

Copper-based ternary halide composites have attracted great attention due to their superior chemical stability and optical properties. Herein, we developed an ultrafast high-power ultrasonic synthesis strategy to realize the uniform nucleation and growth of highly luminescent and stable Cs3Cu2I5 nanocrystals (NCs). The as-synthesized Cs3Cu2I5 NCs show uniform hexagonal morphology with an average mean size of 24.4 nm and emit blue light with a high photoluminescence quantum yield (PLQY) of ∼85%. Moreover, the Cs3Cu2I5 NCs exhibit a remarkable stability during continuous eight times heating/cooling cycling tests (303-423 K). We also demonstrated an efficient and stable white light-emitting diode (WLED) with a high luminous efficiency (LE) of 41.5 lm W-1 and a Commission Internationale de l'Eclairage (CIE) color coordinate of (0.33,0.33).

Protection against light-induced retinal degeneration via dual anti-inflammatory and anti-angiogenic functions of thrombospondin-1.

BACKGROUND AND PURPOSE: Retinal photodamage is a high-risk factor for age-related macular degeneration (AMD), the leading cause of irreversible blindness worldwide. However, both the pathogenesis and effective therapies for retinal photodamage are still unclear and debated. EXPERIMENTAL APPROACH: The anti-inflammatory effects of thrombospondin-1 on blue light-induced inflammation in ARPE-19 cells and in retinal inflammation were evaluated. Furthermore, the anti-angiogenic effects of thrombospondin-1 on human microvascular endothelial cells (hMEC-1 cells) and a laser-induced choroidal neovascularisation (CNV) mouse model were evaluated. in vitro experiments, including western blotting, immunocytochemistry, migration assays and tube formation assays, as well as in vivo experiments, including immunofluorescence, visual electrophysiology, spectral-domain optical coherence tomography, and fluorescein angiography, were employed to evaluate the anti-inflammatory and anti-angiogenic effects of thrombospondin-1. KEY RESULTS: Specific effects of blue light-induced retinal inflammation and pathological angiogenesis were reflected by up-regulation of pro-inflammatory factors and activation of angiogenic responses, predominantly regulated by the NF-κB and VEGFR2 pathways respectively. During the blue light-induced pathological progress, THBS-1 derived from retinal pigment epithelium down-regulated proteomics and biological assays. Thrombospondin-1 treatment also suppressed inflammatory infiltration and neovascular leakage. The protective effect of Thrombospondin-1 was additionally demonstrated by a substantial rescue of visual function. Mechanistically, thrombospondin-1 reversed blue light-induced retinal inflammation and angiogenesis by blocking the activated NF-κB and VEGFR2 pathways, respectively. CONCLUSION AND IMPLICATIONS: Thrombospondin-1, with dual anti-inflammatory and anti-neovascularisation properties, is a promising agent for protection against blue light-induced retinal damage and retinal degenerative disorders which are pathologically associated with inflammatory and angiogenic progress. LINKED ARTICLES: This article is part of a themed issue on Inflammation, Repair and Ageing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.9/issuetoc.

Photogenerated charge separation and recombination path modification in monocline Lu2WO6via lattice transition and Bi-O antibonding states.

Monoclinic Lu2WO6 undergoes diphase-to-perovskite BiLuWO6 transition via selective occupancy of Bi in three Lu sites. The transformation mechanism, process, and structure stabilities are revealed by variable cell nudged elastic band method, video, and phonon spectrum. Lattice transition brings about photogenerated charge separation in BiLuWO6. This is verified by indirect band gap transition, high electron migration rate, weak exciton binding energy, large photocurrent response, and small impedance. The electron-hole life time is elongated to produce abundant superoxide and hydroxyl radicals for the degradation of rhodamine B and phenol molecules. Bi-O antibonding states serve as immediate energy levels to change the recombination path, inducing 340 nm excitation band and 510 nm green light emission of Lu2WO6. Furthermore, multicolor emission of 1 at% Bi3+ + RE3+ (RE = Sm/Eu/Dy)-codoped Lu2WO6 is acquired via synergistic modification of the Bi-O antibonding state and RE3+ 4f states. Thus, the photogenerated charge motion in Lu2WO6 is tuned to expand application fields.

Effects of blue light-exposed retinal pigment epithelial cells on the process of ametropia.

Ametropia is one of the most common ocular disorders worldwide, to which almost half of visual impairments are attributed. Growing evidence has linked the development of ametropia with ambient light, including blue light, which is ubiquitous in our surroundings and has the highest photonic energy among the visible spectrum. However, the underlying mechanism of blue light-mediated ametropia remains controversial and unclear. In the present study, our data demonstrated that exposure of the retinal pigment epithelium (RPE) to blue light elevated the levels of the vital ametropia-related factor type Ⅰ collagen (COL1) via ß-catenin inhibition in scleral fibroblasts, leading to axial ametropia (hyperopic shift). Herein, our study provides evidence for the vital role of blue light-induced RPE dysfunction in the process of blue light-mediated ametropia, providing intriguing insights into ametropic aetiology and pathology by proposing a link among blue light, RPE dysfunction and ametropia.

Full-color fluorescent carbon quantum dots.

Quantum dots have innate advantages as the key component of optoelectronic devices. For white light-emitting diodes (WLEDs), the modulation of the spectrum and color of the device often involves various quantum dots of different emission wavelengths. Here, we fabricate a series of carbon quantum dots (CQDs) through a scalable acid reagent engineering strategy. The growing electron-withdrawing groups on the surface of CQDs that originated from acid reagents boost their photoluminescence wavelength red shift and raise their particle sizes, elucidating the quantum size effect. These CQDs emit bright and remarkably stable full-color fluorescence ranging from blue to red light and even white light. Full-color emissive polymer films and all types of high-color rendering index WLEDs are synthesized by mixing multiple kinds of CQDs in appropriate ratios. The universal electron-donating/withdrawing group engineering approach for synthesizing tunable emissive CQDs will facilitate the progress of carbon-based luminescent materials for manufacturing forward-looking films and devices.

Transparent Nanostructured BiVO4 Double Films with Blue Light Shielding Capabilities to Prevent Damage to ARPE-19 Cells.

The hazards posed by blue light to human eyes are attracting significant attention owing to increasing exposure to electronic devices as well as artificial illumination. Therefore, in this study, nanostructured BiVO4 (BVO) double films were developed using an economical and environmentally friendly sol-gel spin-coating method; the films exhibited excellent blue light shielding capabilities. They could block 65.25% of the blue light in the 415-455 nm wavelength range while simultaneously maintaining an average transmittance greater than 85% in the 500-800 nm wavelength range. Moreover, the damp heat test (85 °C, 85% relative humidity) showed the excellent stability of the BVO filters as their transmittances remained unchanged for 15 days. Importantly, cell experiments were performed to further confirm the protective effects of the BVO filters against the hazards posed by blue light to ARPE-19 cells (human retinal pigment epithelium cell line). Furthermore, the blue light weighted radiance LB decreased by 34.32%, and the color rendering index showed negligible differences after applying an upscaled BVO filter to a phone screen. These cost-efficient, ecofriendly, highly reliable, and large-area nanostructured BVO films with high blue light shielding efficiency have potential applications in various areas.

White luminescent single-crystalline chlorinated graphene quantum dots.

A new class of white luminescent materials, white-light-emitting graphene quantum dots (WGQDs), have attracted increasing attention because of their unique features and potential applications. Herein, we designed and synthesized a novel WGQDs via a solvothermal molecular fusion strategy. The modulation of chlorine doping amount and reaction temperature gives the WGQDs a single-crystalline structure and bright white fluorescence properties. In particular, the WGQDs also exhibit novel and robust white phosphorescence performance for the first time. An optimum fluorescence quantum yield of WGQDs is 34%, which exceeds the majority of reported WGQDs and other white luminescent materials. The WGQDs display broad-spectrum absorption within almost the entire visible light region, broad full width at half maximum and extend their phosphorescence emission to the entire white long-wavelength region. This unique dual-mode optical characteristic of the WGQDs originates from the synergistic effect of low-defect and high chlorine-doping in WGQDs and enlarges their applications in white light emission devices, cell nuclei imaging, and information encryption. Our finding provides us an opportunity to design and construct more advanced multifunctional white luminescent materials based on metal-free carbon nanomaterials.

Yellow fluorescent graphene quantum dots as a phosphor for white tunable light-emitting diodes.

In recent decades, quantum dots have been considered to be highly promising photoluminescent materials for white light devices. During the application of quantum dots in the fabrication of white LEDs, the spectrum and color temperature of the devices are modulated; these devices often involve quantum dots with different emission wavelengths. In this study, yellow-green emitting graphene quantum dots (GQDs) were fabricated using a simple, low-cost and eco-friendly method. The obtained GQDs were cast in UV-curable siloxane. Then, a polymer film with superior optical transparency and excellent monodisperse properties of GQDs was formed. Via the simple adjustment of thickness and the GQD concentration of the color convert matrix, tunable color temperatures (3196-10 870 K) of the GQD-based white light-emitting diodes (LEDs) were achieved. The CIE (Commission Internationale de L'Eclairage) coordinates of the GQD-based white light-emitting diodes matched well with the blackbody radiation curve. Using the fluorescent polymeric matrix in white LEDs, good quality emission and gratifying stability could be obtained. Moreover, this indicates that this technology has the potential for applications in high-end lighting.

One-step hydrothermal synthesis and optical properties of self-quenching-resistant carbon dots towards fluorescent ink and as nanosensors for Fe3+ detection.

In our work, blue photoluminescent N-doped carbon dots (CDs) were developed via a green and simple hydrothermal method with citric acid and polyvinyl pyrrolidone (PVP K-30) as the carbon source and the nitrogen source, respectively. The as-prepared CDs have a high fluorescent quantum yield of 30.21% and considerable luminescence stability. The fluorescence intensity of the CDs was found to be effective quenched when adding Fe3+ ions to the CDs solution. The quenching phenomenon can be used to detect Fe3+ ions within a linear range of 0-300 µM with a detection limit of 45.5 nmol L-1, which suggested its potential application in the detection of Fe3+ ions. At the same time, we also noted the excellent self-quenching-resistant property of the as-prepared CDs in the solid state, and bright blue fluorescence was observed under UV excitation. What's more, the as-prepared CDs can also be used as fluorescent ink and were presented under UV excitation.

Monoclinic Lu2-xSmxWO6-Based White Light-Emitting Phosphors: From Ground-Excited-States Calculation Prediction to Experiment Realization.

Through ground state and constrained density function calculations, Sm3+ ions luminescence in self-activated monoclinic Lu2WO6 was originated from intra 4f → 4f transitions, not inter 5d → 4f transitions. Theoretically the white luminescence was obtained by combining red and blue-green emissions of 4f energy levels and W-O charge transfer transitions. Experimentally, pure and Sm3+ doping Lu2WO6 powders were synthesized using solid phase reaction calcined in air atmosphere. By the analysis of X-ray photoelectron spectroscopy and Rietveld refinement, element Sm charge state was trivalent, and Sm3+ doping was concentration-dependent selectively doping in three Lu sites. With the increase of Sm3+ concentrations, the color coordinates changed gradually from blue (0.17, 0.17) through white light (0.33, 0.25) toward orange (0.44, 0.32) in the visible spectral under 325 nm excitation. On the basis of the theoretical prediction and experimental preparation, a white emission LED lamp was produced using a 365 nm ultraviolet chip and Lu1.99Sm0.01WO6 phosphor. The present design method can be applied to select excellent activators from a large number of rare-earth (Re) ions like Sm3+ and Eu3+/2+ or non-Re ions like Bi3+ and Mn4+ in various matrixes.

Scalable synthesis of organic-soluble carbon quantum dots: superior optical properties in solvents, solids, and LEDs.

Carbon quantum dots (CQDs) have attracted much attention owing to their unique optical properties and a wide range of applications. The fabrication and control of CQDs with organic solubility and long-wavelength emission are still urgent issues to be addressed for their practical use in LEDs. Here, organic-soluble CQDs were produced at a high yield of ∼90% by a facile solvent engineering treatment of 1,3,6-trinitropyrene, which were simultaneously used as the nitrogen and carbon sources. The optical properties of the organic-soluble CQDs (o-CQDs) were investigated in nonpolar and polar solvents, films, and LED devices. The CQDs have a narrow size distribution around 2.66 nm, and can be dispersed in different organic solvents. Significantly, the as-prepared CQDs present an excitation-independent emission at 607 nm with fluorescence quantum yields (QYs) up to 65.93% in toluene solution. A pronounced solvent effect was observed and their strong absorption bands can be tuned in the whole visible region (400-750 nm) by changing the solvent. The CQDs in various solvents can emit bright, excitation-independent, long-wavelength fluorescence (orange to red). Furthermore, benefiting from the unique oil-solution properties, the as-prepared CQDs can be processed in thin film and device forms to meet the requirements of various applications, such as phosphor-based white-light LEDs. The color coordinate for these CQD modified LEDs is realized at (0.32, 0.31), which is close to pure white light (0.33, 0.33).

[Research on the Highly Stable White LED with CdSe/ZnS Quantum Dot as Light Conversion Layer].

In accordance with the one-step synthesis, in this paper, we synthesized 510, 550 and 630 nm three emission peaks CdSe/ZnS core-shell quantum dots with high stability and high quantum yield whose quantum yield were 82%, 98% and 97%. We used the quantum dot material to replace the phosphor material, and mixed QDs with the silicone uniformly, then dispersed the QDs/silicone composites onto the blue InGaN LEDs to fabricate the QDs-WLEDs. By successively adding different colors of quantum dots for the preparation of quantum dot light converting layer, We investigated that how does the ratio of the three kind of quantum dots whose peaks were 510, 550 and 630 nm effect on the properties of the white LED devices. This paper also studied the mechanism of energy conversion between different colors of quantum dots. We also utilized the mechanism that the quantum dots effect on the white spectrum and color coordinates; we got the results of the optimization of the white device and the ratio of three-color quantum dots. The results show that when the quantum dot ratio is 24:7:10, white LED devices with high stability and high efficiency can be obtained, in the current range of 20-200 mA, the range of color temperature is from 4 607 to 5 920 K, the CIE-1931 coordinates is from (0.355 1,0.348 3) to (0.323 4, 0.336 1), the color rendering index is from 77. 6 to 84. 2, and the highest power efficiency of the devices achieves to 31.69 lm · W⁻¹ @ 20 mA. In addition, in order to further investigate the reason of stable device performance, We studied the effects of time, temperature, UV treatment on the stability of CdSe/ZnS QDs/silicone light conversion material, the results show that the excellent stability of the devices attributes to the stability of the one-step synthesis of core-shell structure of the quantum dot material, the final optimized device is a low-power high-quality white light source and the device has good application prospects in the field of standard white light source which can truly perceive the color and original features of objects.