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Ultraviolet to blue blocking and wavelength convertible films using carbon dots for interrupting eye damage caused by general lighting
摘要： Our eyes are regularly exposed to ultraviolet (UV) and blue light emitting diode (LED) light-based devices. However, the blue light induces macular degeneration, optic nerve crush, eye strain, and increases reactive oxygen species, which negatively influence eye-related cells (photoreceptor and retinal pigmented epithelial cells). UV light is also harmful to humans. It induces photokeratitis, cataract, and ocular surface squamous neoplasia. Here, we present carbon dot films with different carbon dot contents, prepared by a simple method. The films exhibit strong UV and blue light absorption. The transmittance of carbon dot films is >70% in the visible region (>500 nm). The UV light blocking ratio of commercial blue blocking filter and carbon dot film using UV LED chips is 94.1% and 95.9% (40 wt%), respectively. The blue light blocking ratio of commercial blue blocking filter and carbon dot film using blue LED chips is 10.2% and 82.3% (40 wt%), respectively. These results indicate that the prepared carbon dot films have a UV blocking rate similar to that of commercial blue blocking filters and a much better blue blocking rate than commercial blue blocking filters. Therefore, they can be effectively used as UV and blue blocking films in various applications.
关键词： White LED,Eye damage,UV blocking film,Carbon dot,blue blocking film
更新于2025-11-14 15:15:56
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Enhanced absorption of Sr3Lu2(BO3)4:Ce3+,Tb3+ phosphor with energy transfer for UV-pumped white LEDs
摘要： A series green emission phosphors Sr3Lu2(BO3)4:Ce3+,Tb3+ (denoted as SLBO:Ce3+,Tb3+) with broad absorption band matching well with UV LED chip were synthesized by the solid–state reaction method. The phase and structure were analyzed with XRD, EDX, FT-IR measurements. The energy transfer between Ce3+ and Tb3+ in SLBO was proved by spectra and decay curves detailedly. The emission colors vary from blue to green by adjusting the ratio of Ce3+/Tb3+ doped concentration. With temperature increasing, SLBO:Ce3+,Tb3+ phosphor shows well thermal stability that emission intensity retains 70% of its initial at 25 oC even temperature rising to 150 oC. The internal and external quantum efficiency of SLBO:3%Ce3+,8%Tb3+ are 77.5% and 34.8% under 340 nm excitation, respectively. Combining the as-synthesized SLBO:Ce3+,Tb3+ and red emission phosphor CaAlSiN3:Eu2+ coated on a 365 nm UV chip, a warm white LEDs device with CRI of 83 was achieved. All the results indicate that the SLBO:Ce3+,Tb3+ phosphor has potential application in UV pumped white LEDs.
关键词： phosphor,thermal stability,energy transfer,UV LED
更新于2025-10-22 19:38:57
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[IEEE 2018 International Conference on Advanced Technologies for Communications (ATC) - Ho Chi Minh City, Vietnam (2018.10.18-2018.10.20)] 2018 International Conference on Advanced Technologies for Communications (ATC) - Keynote talk #2: Visible light communications for 5G-and-beyond wireless telecommunications networks
摘要： Artificial general lighting sources are currently evolving through the traditional fluorescent and incandescent sources to the modern energy saving light bulbs and now white light emitting diodes (LEDs). This trend has been spurred on through global awareness of the necessity for reducing the size of our carbon footprint. The introduction of solid state LED lighting has attracted the attention of communications engineer's worldwide, enabling the achievement of the dual functionality of room illumination whilst simultaneously transmitting wireless data via visible light communication (VLC), or Light Fidelity (LiFi), in optical spectrum regime. Although the existing wireless networks are primely dominated by radio-based technology, the emerging VLC will play increasingly important role in future wireless telecommunications landscape. It is anticipated that both spectrum regimes, radio and optical, will eventually contribute equally for the next network generation, especially in nanocell and picocell network structures. This talk will outline the growth of optical wireless communications including VLC, and present the challenges and roadmap of the technology for the future generation of wireless networks.
关键词： Visible Light Communications,Networks,LED,LiFi
更新于2025-09-23 15:23:52
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Spectral Optimization to Minimize Light Absorbed by Artwork
摘要： Light is needed to appreciate artwork, but visible radiation causes damage by photochemical action. Photons trigger photochemical action only when they are absorbed by the object. Damage to sensitive materials can be reduced by optimizing the spectrum of a light source to the reflectance factor of a museum artifact. Absorption minimization approaches can be utilized to quantify and optimize typically conflicting parameters, such as damage due to light absorption, color quality of artwork, and energy consumption. In this project, seven narrowband light emitting diodes (LEDs) are optimized using a multi-objective genetic algorithm to reduce light absorption and energy consumption, while maintaining the color appearance of five paints (blue, green, yellow, orange, red). Results indicate that optimized test spectra can reduce light absorption between 18% and 48%, without causing perceptible color or hue shifts in the paintings. Parallel to absorption, energy consumption is almost halved for all of the paints (between 42% and 48%). Optimizing the light source spectrum can aid in conservation of art collections in museums by reducing damage caused by optical radiation while preserving color fidelity.
关键词： color perception,LED sources and systems,Art conservation,museum lighting,color rendition
更新于2025-09-23 15:23:52
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Dehydrogenation-driven to synthesize high-performance Lu2Si4N6C:Ce3+- a broad green-emitting phosphor for full-spectrum?lighting
摘要： Green phosphor Lu2Si4N6C:Ce3+ (LSNC:Ce3+) shows an ideal feasibility to the near ultraviolet LED (n-UV LED) for “Full-Spectrum Lighting” (FSL). However, it is complex to synthesize pure Lu2Si4N6C phase. Herein, we prepared LSNC:Ce3+ via a novel dehydrogenation-driven high temperature solid-state reaction method, which distinctly optimized the morphology, and then significantly enhanced the photoluminescent performance of LSNC:Ce3+. The improving mechanism ascribed to the stepwise dehydrogenation of LuH3 which was beneficial to further shear LuH3 particles. The LSNC:Ce3+ phosphor obtained by the optimized process exhibits excellent thermal stability, and its external quantum efficiency is 57.3 %. Interestingly, the intensities of excitation peaks decrease at 375 nm while it increases at 425 nm gradually with the Ce3+ concentration. It is reasonably ascribed to the different ability of photo-ionization in different 5d levels. Finally, the constructed w-LED with the titled phosphor exhibits a well-distributed warm white light with high color rendering index (Ra = 96.6, R9 = 96, R12 = 82). It indicates that the LSNC:Ce3+ gives assistance to compensation for the “spectrum chasm” in blue-green region, as well as contributes to the improvement of Ra and R9, that is beneficial for full-spectrum lighting.
关键词： Carbonitride,n-UV LED,Reaction mechanism,Full-Spectrum,Green phosphor Lu2Si4N6C:Ce3+
更新于2025-09-23 15:23:52
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Highly efficient and thermally stable of a novel red phosphor Sr3NaSbO6:Mn4+ for indoor plant growth
摘要： Far red-emitting Mn4+-activated oxide phosphor based on the substitution of Mn4+ for Sb5+ in the lattice of Sr3NaSbO6 (SNSO) was prepared via solid state reaction process. The crystal structure of the host was carefully discussed and studied. The resultant phosphors were characterized by X-ray powder diffraction, fluorescence spectra, ultraviolet-visible diffuse reflectance spectra, temperature-dependent emission spectra (298–548 K), luminescence decay curves and electroluminescence spectra. Excitation and emission spectra indicated that the sample had a wide excitation band in UV(250–400 nm) and exhibited the strong emission band centered at 695 nm. The band structure for SNSO was calculated based on the density functional theory, and the bandgap value of SNSO host is ～2.92 eV. In addition, the mechanism of quenching concentration and energy-transfer of SNSO:Mn4+ were explored and analyzed in detail through calculation. The UV–Vis diffusion reflectance spectra demonstrated that samples had strong absorption (200–550 nm) in the ultraviolet(UV) and near-ultraviolet (NUV) region. The thermal stability of SNSO:Mn4+ was excellent (I423K/I273K = 39.84%). The internal quantum efficiency is 56.2%. In brief, the prepared phosphors had potential application in indoor plant growth as a LED lamp.
关键词： Sr3NaSbO6:Mn4+,Far red-emitting LED,Photoluminescence,Optical properties,Plant growth
更新于2025-09-23 15:23:52
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Structure variation and luminescence enhancement of BaLaMg(Sb, Nb)O6:Eu3+ double perovskite red phosphors based on composition modulation
摘要： A series of BaLaMgSb1-xNbxO6:Eu3+ double perovskite red phosphors was successfully obtained. X-ray diffraction and Rietveld refinement analyses were conducted to determine the phase information and the detailed structure parameters. The coordinate variations of both La3+/Eu3+ and Sb5+/Nb5+ were discussed to elucidate the influence of B-site ion doping on the lattice variation. Luminescence properties, excitation and emission spectra, were presented to show the advantages of doping with Nb5+ ion. Ultraviolet-vis diffuse reflectance spectra were performed to reveal the reason for the decreased emission intensity under the charge transfer band excitation. Moreover, band gap energy was estimated to clarify the relationship between the increased intensity (λex = 395 and 465 nm) and Nb5+ concentration. Intensity ratios of I(615)/I(590) were performed to show the symmetry variation of the lattice. Thermal quenching property was also investigated and the quenching mechanism was discussed in detail based on the ionization process.
关键词： White LED,Structure variation,Thermal quenching mechanism,Double perovskite
更新于2025-09-23 15:23:52
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[IEEE 2018 24rd International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Stockholm, Sweden (2018.9.26-2018.9.28)] 2018 24rd International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Structural analysis and modelling of packaged light emitting devices by thermal transient measurements at multiple boundaries
摘要： The paper presents a comprehensive methodology for modeling the electrical, optical, and thermal domains of high-power LEDs, focusing on the XPE2 type from Cree. It introduces optimization algorithms (OPT1 and OPT2) to extract parameters such as series resistance (RS), ideality factor (m), and saturation current (I0) from forward voltage (VF) measurements. A quadratic model for radiant voltage (Vrad) is developed to describe the optical output, and thermal modeling is addressed through structure functions derived from transient thermal measurements. The approach enables accurate prediction of LED performance across varying currents and temperatures, with applications in thermal management and design optimization.
关键词： ideality factor,thermal management,structure function,LED modeling,radiant flux,forward voltage,saturation current,series resistance
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE XXVII International Scientific Conference Electronics (ET) - Sozopol, Bulgaria (2018.9.13-2018.9.15)] 2018 IEEE XXVII International Scientific Conference Electronics - ET - Performance of the Front-End Electronics of the PADME charged particle detector system
摘要： The PADME charged particle detector system should detect positrons and electrons with efficiency better than 99 % and time resolution below 1 ns. The system hosts about 200 readout electronics channels whose operation has to be verified and commissioned. A custom based test system allowing to perform qualitative check of the produced front-end electronics has been developed and was used to test a total of 256 channels. The obtained time resolution was found to be consistent with the requirements and better than 500 ps for all the channels.
关键词： scintillation detectors,front-end electronics,LED driver
更新于2025-09-23 15:23:52
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Power spectral density-based nearinfrared sub-band detection for noninvasive blood glucose prediction in both <i>in-vitro</i> and <i>in-vivo</i> studies
摘要： Diabetes is a widespread and serious disease and noninvasive measurement has been in high demand. To address this problem, a power spectral density-based method was offered for determining glucose sensitive sub-bands in the nearinfrared (NIR) spectrum. The experiments were conducted using phantoms of different optical properties in-vitro conditions. The optical bands 1200–1300 nm and 2100–2200 nm were found feasible for measuring blood glucose. After that, a photoplethysmography (PPG)-based low cost and portable optical system was designed. It has six different NIR wavelength LEDs for illumination and an InGaAs photodiode for detection. Optical density values were calculated through the system and used as independent variables for multiple linear regression analysis. The results of blood glucose levels for 24 known healthy subjects showed that the optical system prediction was nearly 80% in the A zone and 20% in the B zone according to the Clarke Error Grid analysis. It was shown that a promising easy-use, continuous, and compact optical system had been designed.
关键词： Noninvasive,led,blood glucose,power density.,nearinfrared,photoplethysmography
更新于2025-09-23 15:23:52