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Nanoscale Characterization of Surface Plasmon-Coupled Photoluminescence Enhancement in Pseudo Micro Blue LEDs Using Near-Field Scanning Optical Microscopy
摘要： The microcave array with extreme large aspect ratio was fabricated on the p-GaN capping layer followed by Ag nanoparticles preparation. The coupling distance between the dual-wavelength InGaN/GaN multiple quantum wells and the localized surface plasmon resonance was carefully characterized in nanometer scale by scanning near-field optical microscopy. The effects of coupling distance and excitation power on the enhancement of photoluminescence were investigated. The penetration depth was measured in the range of 39–55 nm depending on the excitation density. At low excitation power density, the maximum enhancement of 103 was achieved at the optimum coupling distance of 25 nm. Time-resolved photoluminescence shows that the recombination life time was shortened from 5.86 to 1.47 ns by the introduction of Ag nanoparticle plasmon resonance.
关键词： near-field scanning optical microscopy,micro-LEDs,localization surface plasmon
更新于2025-09-23 15:19:57
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Photochemical Synthesis of Silver Nanodecahedrons under Blue LED Irradiation and Their SERS Activity
摘要： Silver nanodecahedrons were successfully synthesized by a photochemical method under irradiation of blue light-emitting diodes (LEDs). The formation of silver nanodecahedrons at different LED irradiation times (0–72 h) was thoroughly investigated by employing different characterization methods such as ultraviolet–visible spectroscopy (UV–Vis), transmission electron microscopy (TEM), and Raman spectroscopy. The results showed that silver nanodecahedrons (AgNDs) were formed from silver nanoseeds after 6 h of LED irradiation. The surface-enhanced Raman scattering (SERS) effects of the synthesized AgNDs were also studied in comparison with those of spherical silver nanoparticles in the detection of 4-mercapto benzoic acid. Silver nanodecahedrons with a size of 48 nm formed after 48 h of LED irradiation displayed stronger SERS properties than spherical nanoparticles because of electromagnetic enhancement. The formation mechanism of silver nanodecahedrons is also reported in our study. The results showed that multihedral silver nanoseeds favored the formation of silver nanodecahedrons.
关键词： LEDs,photochemical synthesis,SERS,silver nanodecahedron
更新于2025-09-23 15:19:57
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A novel Mn4+ doped red phosphor composed of MgAl2O4 and CaAl12O19 phases for Light-Emitting Diodes
摘要： The red emitters based on CaAl12O19:Mn4+ have been attracting extensive attentions due to their advantages of rare-earth-free and chemical stability. However, their relatively low luminescent efficiencies will seriously hinder their application for light-emitting diodes (LEDs). In this regard, one of promising red phosphors of CaAl12O19:Mn4+ was synthesized with enhanced luminous efficiency by introducing the coexistence phase of MgAl2O4. Importantly, an approximately 5 times enhancement of integrated intensity on emission spectrum was observed in the coexistence phase comparing of these single one. Their crystalline structures, morphologies, photoluminescence as well as the mechanism of improved luminescence were systematically investigated. Exciting them by using near-ultraviolet or blue LEDs, an efficient red emission was achieved with a maximum peak at ~ 658 nm. In order to evaluate the potential application, a warm white LED and a plant-growth LED are fabricated by using the prepared phosphors in combination with YAG:Ce3+ and InGaN-based blue chips.
关键词： MgAl2O4,LEDs,CaAl12O19,red phosphor,Mn4+
更新于2025-09-23 15:19:57
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New, highly versatile bimolecular photoinitiating systems for free-radical, cationic and thiola??ene photopolymerization processes under low light intensity UV and visible LEDs for 3D printing application
摘要： 1-Amino-4-methyl-naphthalene-2-carbonitrile derivatives are proposed for the role of photosensitizers of iodonium salt during the photopolymerization processes upon near UV-A and visible ranges. Remarkably, 1-amino-4-methyl-naphthalene-2-carbonitrile derivatives are highly versatile allowing access to photoinitiating systems for (i) the cationic photopolymerization of epoxide monomers with a ring opening mechanism and vinyl ether monomers with chain growth mechanisms (ii) the free-radical photopolymerization of acrylate monomers, (iii) the photopolymerization of interpenetrated polymer networks (IPNs) based on epoxide and acrylate monomers under air and under laminate in an oxygen-free atmosphere (iv) the thiol–ene photopolymerization processes. Excellent polymerization pro?les are obtained during all types of photopolymerization processes. The initiation mechanisms are analyzed through steady state photolysis, cyclic voltammetry and ?uorescence experiments. Moreover, the newly developed bimolecular photoinitiating systems were investigated by applying an additive manufacturing process under visible light sources. Furthermore, vat photopolymerization processes using IPN compositions, which are polymerizable by using new photoinitiating systems, provide high resolution and speeds. For these reasons, new bimolecular photoinitiating systems are promising initiators for photopolymerization-based 3D printing process to fabricate 3D structures.
关键词： visible LEDs,photopolymerization,photoinitiating systems,3D printing,UV-LED
更新于2025-09-23 15:19:57
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LED&Paper-based Analytical Device for Phosphatemia/Calcemia Diagnostics
摘要： In this communication a prototype of paper-based analytical device designed for simultaneous determination of orthophosphate and calcium ions, which levels are significant for hyperphosphatemia diagnostics, is presented. The laboratory-on-paper structure for two analytes detection was wax-printed on the surface of filter paper. These two-analyte disposable paper strips are combined with two paired LED-based fluorescence detectors and simple voltmeter used as recorder of analytical signal, what makes the developed device miniature, extremely low-cost, portable and user-friendly. Thus the developed device allows usage at the patient’s bed or by patients themselves. Moreover, each paper strip is disposable and its utilization is easy and fast and, additionally, burnt strip tests ensure waste non-infectious. The presented LED&Paper-based analytical device provides low detection limits: 1.4 μM and 7.4 μM for orthophosphate and calcium ions, respectively. The practical utility of the developed device for calcemia/phosphatemia diagnostics is demonstrated using control serum standards and real human serum.
关键词： Paper-based device,Orthophosphate,Fluorescence,LEDs,Calcium
更新于2025-09-23 15:19:57
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Indoor Visible Light Communications, Networking, and Applications
摘要： Light-emitting diodes (LEDs) are changing indoor wireless communications. Visible light communications (VLC) that use LEDs as transmitters is an emerging research area and has significant commercial potential. The light emitted from LEDs can simultaneously carry information and provide illumination. Due to the intrinsic characteristics of light, VLC is more secure, more power efficient, and can provide higher network data transmission rates than radio frequency (RF) communications. This paper describes state-of-the-art VLC systems including transmitters, receivers, and channel models. Modulation and networking algorithms for physical layer and cross-layer designs are discussed. These algorithms are designed considering practical constraints, such as the bandlimited channel, illumination requirements, and transmitted power limitations. Indoor localization algorithms are proposed, with a particular focus on fingerprinting. In addition, this paper introduces practical applications of VLC in many fields such as national defense, healthcare, robotics, and vehicle-to-vehicle communications. The paper concludes with a discussion of the challenges, opportunities, and future of VLC.
关键词： Visible light communications,modulation,optical wireless communications,visible light positioning,LEDs,networking
更新于2025-09-23 15:19:57
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Mn <sup>4+</sup> -activated BaLaMgSbO <sub/>6</sub> double-perovskite phosphor: a novel high-efficiency far-red-emitting luminescent material for indoor plant growth lighting
摘要： In the present work, novel high-efficiency Mn4+-activated BaLaMgSbO6 (BLMS) far-red-emitting phosphors used for plant growth LEDs were successfully synthesized via a solid-state reaction method. X-ray diffraction (XRD), photoluminescence (PL), temperature-dependent PL, CIE color coordinates, and lifetimes as well as internal quantum efficiency (IQE) were used to characterize the phosphor samples. The excitation spectrum of the as-obtained BLMS:Mn4+ phosphors presented two wide bands covering 250–550 nm and the emission spectrum exhibited a far-red emission band in the range of 650–800 nm peaked at 700 nm. Concentration-dependent PL properties of BLMS:Mn4+ phosphors were studied. The optimal doping concentration of Mn4+ ions was 0.6 mol%, and the concentration quenching mechanism was determined to be the nonradiative energy transfer among the nearest-neighbor Mn4+ activators. Impressively, the BLMS:0.6%Mn4+ sample showed an outstanding IQE of 83%. In addition, the luminescence thermal quenching characteristics were also analyzed. Furthermore, the PL spectrum of BLMS:0.6%Mn4+ sample was compared with the absorption spectrum of phytochrome PFR. Finally, after combining BLMS:0.6%Mn4+ phosphors with a 365 nm near-UV LED chip, a far-red light-emitting diode (LED) device was successfully achieved to demonstrate its possible applications in plant growth LEDs.
关键词： far-red-emitting,solid-state reaction,Mn4+-activated,internal quantum efficiency,plant growth LEDs,phosphor,BaLaMgSbO6
更新于2025-09-19 17:15:36
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2D perovskite hybrid with both semiconductive and yellow light emission properties
摘要： Owing to the structural diversity and potential applications in optoelectronic devices, inorganic-organic hybrid materials have attracted great attentions in recent years. They have potential applications in the fields of fluorescence, photoconductivity, ferroelectricity and solar cells. A new inorganic-organic hybrid, [H2(dmen)]PbCl4 (dmen = N,N-Dimethylethylenediamine), was solvothermally synthesized using [H2(dmen)]2+ as templates and balance cations. The inorganic structure is two-dimensional (2D) single layer perovskite. This compound exhibits typical semiconductive behavior, whose conductivity increases along with the raising of temperature. The compound also shows yellow light emission property, which indicates great potential application in light-emitting diodes.
关键词： Semiconductor,Perovskite,Functional motifs,Inorganic-organic hybrid,LEDs
更新于2025-09-19 17:15:36
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Enhanced deep-red emission from Mn <sup>4+</sup> /Mg <sup>2+</sup> co-doped CaGdAlO4 phosphors for plant cultivation
摘要： Mn4+ doped oxide phosphors are under intensive investigation owing to their low manufacture cost and attractive luminescent features for indoor plant cultivation applications. However, it is still a challenge to develop Mn4+ doped oxides with high luminescence efficiency and thermal stability. Herein, Mn4+-Mg2+ pairs are incorporated into a CaGdAlO4 host to reduce non-radiative channels formed by Mn4+-Mn4+-O2- clusters. The photoluminescence and quantum efficiency are significantly enhanced after the introduction of Mg2+ ions to the host. A prolonged Mn4+ decay time is also obtained from the Mn4+/Mg2+ co-doped samples. Intense red emission with a narrow peak at 712 nm due to the 2Eg → 4A2g transition of Mn4+ ions is observed under 335 nm excitation. The LED fabricated by coating the synthesized phosphor on a 365 nm near-UV chip exhibit intense deep red emission with CIE chromaticity coordinates of (0.712, 0.285). The results indicate the Mn4+/Mg2+ co-doped CaGdAlO4 phosphors may be applied to the plant cultivation fields.
关键词： red phosphors,plant cultivation,LEDs,photoluminescence,Mn4+
更新于2025-09-19 17:15:36
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Rare earth-free composites of carbon dots/metal-organic framework as white light-emitting phosphor
摘要： Over the last few years, numerous efforts have been made to develop white light-emitting metal-organic frameworks (MOFs), due to the useful features of MOFs such as ultrahigh surface areas and tunable pore architecture. However, rare earth (RE) ions are most commonly applied as phosphors in these materials so far, raising device cost and environmental concerns. Here, we designed a new type of RE-free material capable of white light-emission upon excitation at 365 nm, with the photoluminescence quantum yield in solid state reaching 37%, fabricated by compositing carbon dots (CDs) with Zr(IV)-based MOF. WLEDs constructed by depositing the CDs/Zr-MOF nanocomposite on a commercial UV LED chip feature a CIE chromaticity coordinate at (0.31, 0.34), high color rendering index (CRI) of 82, and luminous efficiency of 1.7 lm/W.
关键词： carbon dots,rare-earth-free luminophores,white-light-emission,Zr-MOFs,down-conversion LEDs
更新于2025-09-19 17:15:36