Commercial Blue LED Research Articles

A High-efficiency blue-LED-excitable NIR-II-emitting MgO:Cr3+,Ni2+ phosphor for future broadband light source toward multifunctional NIR spectroscopy applications

The development of phosphor-converted light-emitting diodes (pc-LEDs) in the second near-infrared window (NIR-II, 1000–1700 nm) represents an important, newly emerging, and dynamic field in NIR spectroscopy. Unfortunately, lacking efficient NIR-II phosphors that can be excited by commercial blue LED chips impedes NIR spectroscopy applications. Herein, a donor–acceptor strategy is developed by introducing Cr3+ sensitizers to greatly enhance the blue-light excitation efficiency of NIR-II-emitting MgO:Cr3+,Ni2+ phosphor. Consequently, a high-efficiency blue-light-excitable MgO:Cr3+,Ni2+ phosphor that gives a NIR-II emission at 1335 nm with a full width at half-maximum (FWHM) of 235 nm, is demonstrated. The product has a high internal quantum efficiency of 92.7 % and excellent thermal stability, maintaining 83.0 % of the room temperature emission intensity at 150 °C. Excitingly, the fabricated NIR-II pc-LED device shows a high NIR-II optical power (27.4 mW@350 mA). The performances of the achieved NIR-II pc-LED are almost the best results until now. Additionally, multifunctional applications including nondestructive detection and anti-counterfeiting of the NIR-II light source are demonstrated. These results are pretty crucial for the further development of NIR-II spectroscopy and imaging technology.

Flexible, Free-Standing Polymer Membranes Sensitized by CsPbX3 Nanocrystals as Gain Media for Low Threshold, Multicolor Light Amplification.

Lead halide perovskite nanocrystals (NCs) are highly suitable active media for solution-processed lasers in the visible spectrum, owing to the wide tunability of their emission from blue to red via facile ion-exchange reactions. Their outstanding optical gain properties and the suppressed nonradiative recombination losses stem from their defect-tolerant nature. In this work, we demonstrate flexible waveguides combining the transparent, bioplastic, polymer cellulose acetate with green CsPbBr3 or red-emitting CsPb(Br,I)3 NCs in simple solution-processed architectures based on polymer-NC multilayers deposited on polymer micro-slabs. Experiments and simulations indicate that the employment of the thin, free-standing membranes results in confined electrical fields, enhanced by 2 orders of magnitude compared to identical multilayer stacks deposited on conventional, rigid quartz substrates. As a result, the polymer structures exhibit improved amplified emission characteristics under nanosecond excitation, with amplified spontaneous emission (ASE) thresholds down to ∼95 μJ cm–2 and ∼70 μJ cm–2 and high net modal gain up to ∼450 and ∼630 cm–1 in the green and red parts of the spectrum, respectively. The optimized gain properties are accompanied by a notable improvement of the ASE operational stability due to the low thermal resistance of the substrate-less membranes and the intimate thermal contact between the polymer and the NCs. Their application potential is further highlighted by the membrane’s ability to sustain dual-color ASE in the green and red parts of the spectrum through excitation by a single UV source, activate underwater stimulated emission, and operate as efficient white light downconverters of commercial blue LEDs, producing high-quality white light emission, 115% of the NTSC color gamut.

Lanthanide-doped Mn2+-based perovskite-like single crystals: Switching on highly thermal-stable near-infrared emission and LED device

Metal halide perovskites (MHPs) have sparked ongoing research interest due to their high-performance optoelectronic properties. However, blue-light excitable near-infrared (NIR) emitting MHPs is still inaccessible and the achievement of robust thermal-quenching resistance so far remains a huge challenge. In this work, we report on the synthesis of lead-free all-inorganic Mn2+-based perovskite-like single crystals using the designed nonstoichiometric precursor ratio. The special crystal structure endows Mn2+ with efficient blue light excitation and red emission, which enables the capabilities of a good matching with commercial blue LED chips and an efficient sensitization for Ln3+ emitters. The incorporations of Yb3+, Er3+, and Ho3+ functionalize the CsMnCl3 single crystals with multiple NIR emissions by virtue of feeding the energy from Mn2+ to Ln3+ via multi-channels. Most remarkable is the achievement of the robust thermal-quenching resistance, exhibiting (near-) zero-thermal-quenching and even anti-thermal quenching, of the Ln3+ NIR emissions above room temperature. Finally, as a proof-of-concept study, a prototype of an NIR-LED device was fabricated. This work not only provides a general strategy to unlock the blue-light excitable NIR emission from f-f transitions of Ln3+ ions, and a fundamental understanding of the sensitization-activation mechanisms in Ln3+-functionalized manganese (Ⅱ)-based perovskite-like phosphor, but also endows the MHPs with optical functionalities for the future high-potential applications, such as NIR phosphor-converted LEDs, and optical telecommunication.

Novel one-dimensional Ga2O3:Cr3+ nanofibers with broadband emission for near infrared LED sources

NIR phosphor-converted light-emitting diodes (pc-LEDs) are of great importance for the next-generation smart light sources, while the performances of pc-LEDs are highly dependent on the NIR phosphors. In present study, one-dimensional (1D) Ga2O3:xCr (x = 0, 0.25%, 0.5%, 0.75%, 1.0%, 1.25%) nanofibers with diameters about 250 nm were synthesized via an electrospinning route at low temperature of 700 °C and the nanoscale size paves a way for the Ga2O3:xCr nanofibers used in miniature electronic devices. The photoluminescence excitation (PLE) spectrum exhibits two strong absorptions in the regions of 400–500 nm and 600–700 nm, which matches exceptionally well with the commercial blue light chips. Under 440 nm excitation, nanofibrous Ga2O3:xCr samples show a broad emission from 650 to 840 nm, and the optimized Cr3+ concentration is x = 0.5% with a peak at 730 nm and a full width at half maximum (FWHM) of 140 nm. A NIR pc-LED was fabricated by combining the Ga2O3:0.5%Cr with a commercial blue LED chip. Furthermore, the blood vessels of the hand and the clearer images of flowers and cosmetics were captured by NIR camera under illuminating of the fabricated NIR pc-LED, which demonstrates the promise of the Ga2O3:xCr nanofibers in NIR pc-LED applications.

Single-step hydrothermal synthesis of ZnO/NiO hexagonal nanorods for high-performance supercapacitor application

The single-step hydrothermal technique was used to synthesize nickel (II) oxide-zinc nitrate hexahydrate (NZ), hexagonal-shaped nanorods for high-performance supercapacitors applications (SC). The structural morphology and physical properties of the NZ nanocomposite were investigated via XRD, FESEM, HRTEM, XPS, and Raman spectroscopy. Among the prepared nanocomposite, NZ-10 shows the most significant properties, which were used for the fabrication of all-solid-state symmetric supercapacitors (SSC). Electrochemical analysis of the Galvano charging-discharging (GCD) curves achieved a high specific capacitance (Csp) of 665.4 Fg-1 at a current density (CD) of 1 Ag-1. The cyclic Voltammetry (CV) curve for the electrode shows a high Csp of 514.4 Fg-1 at a scan rate of 10 mV/s. Even after 5000 repeated cycles, it maintains strong cyclic stability, with capacitance retention of 73.43% and a coulombic efficiency of 96.12%. In addition, the NZ-10 composite has a high energy density (ED) of 26.73 Whkg−1 and a power density (PD) of 641.5 Wkg-1. In addition, the SSC device is connected in series to switch on a commercial blue LED that lasts 2–3 min and has a voltage drop of 2.71 V. As a result, these electrochemical performances are the highest in these materials, and they may be a good aspirant to fabricate advanced active materials for high-performance SC applications.

Embedding red-emitting dyes in robust hydrogen-bonded organic framework for application in warm white light-emitting diodes

Broadband yellow-emitting phosphors are very attractive for warm white light-emitting diodes (WLEDs) used in solid-state lighting, backlight display, and related fields. In this work, we describe a room temperature, solution processable yellow-emitting phosphors for warm WLEDs using the chemically stable nanoscale hydrogen-bonded organic framework (HOF) PFC-1 as the host. By embedding the red-emitting dyes of rhodamine B (RhB), rhodamine 6G (Rh6G), 4-( p -dimethylaminostyryl)-1-methylpyridinium (DSM), and 4-(dicyanomethylene)-2-methyl-6-( p -dimethylaminostyryl)-4H-pyran (DCM) in the green-emitting nano PFC-1, respectively, four types of single-matrix yellow-emitting nanocomposites were obtained. Due to the spectral combination of host PFC-1 and guest dyes, the obtained nanocomposites show broader emission spectra than that of the commercial yellow phosphor. Specifically, RhB@PFC-1 has a promising quantum yield of 17.8%. By coating the nanophosphors on the commercial blue LED chips (450 nm), bright sources of warm-white light were realized. It was found that the RhB@PFC-1 coated LED has an excellent color rendering index (CRI) of 85.6 and a correlated color temperature (CCT) of 4669 K at a drive current of 300 mA, while Rh6G@PFC-1 coated LED shows warm white light with a low CCT of 3100 K and a promising CRI of 75.4 K. This Dye@HOF strategy opens an avenue to developing yellow-emitting phosphors for the use in high color rendering warm WLEDs. • A series of yellow-emitting Dye@PFC-1 nanophosphors were reported. • The Dye@PFC-1 nanocomposites show a broader emission band than that of YAG:Ce 3+ . • Bright sources of warm white light were achieved by coating the nanocomposites on blue LED chips. • The WLED coated with RhB@PFC-1 exhibits a CRI of 85.6 and a CCT of 4669 K at a 300 mA driven current.

An efficient garnet-structured Na3Al2Li3F12:Cr3+ phosphor with excellent photoluminescence thermal stability for near-infrared LEDs

The emerging applications of near-infrared (NIR) spectroscopy technology in medicine and food security call for compact and efficient NIR light source such as NIR phosphor converted LEDs (pc-LED). Currently, most of the NIR phosphors suffer from low photoluminescence (PL) quantum yield and poor thermal or chemical stability. Herein, a fluoride garnet NIR Na3Al2Li3F12:Cr3+ phosphor was successfully synthesized via coprecipitation method. It can be excited efficiently by blue or red light and shows a broad emission band covering 650–1000 nm (bandwidth of ~110 nm) with a PL quantum yield of 78%. The fine electronic structure of Cr3+ ions in the host was revealed by the measurement of temperature-dependent (8–300 K) excitation and emission spectra analysis. Particularly, at 423 K, the Na3Al2Li3F12:5%Cr3+ sample retained ~99% of the PL intensity at room temperature, exhibiting excellent PL thermal stability. A NIR pc-LED was fabricated by combining the Na3Al2Li3F12:5%Cr3+ phosphor with a commercial blue LED chip, and radiant flux of 14.3 mW in NIR region was obtained at 60 mA drive current. Furthermore, the penetration of NIR light generated by this pc-LED in chicken breast was reached. The results suggested that Na3Al2Li3F12:Cr3+ is a promising candidate for broadband pc-LED in NIR spectroscopy applications.

Efficient near‐infrared pyroxene phosphor LiInGe2O6:Cr3+for NIR spectroscopy application

AbstractBroadband near‐infrared phosphors are essential to realize nondestructive analysis in food industry and biomedical areas. Efficient long‐wavelength (>830 nm) phosphors are strongly desired for practical applications. Herein, we demonstrate an efficient broadband NIR phosphor LiInGe2O6:Cr3+, which exhibits a broad NIR emission peaking at ~880 nm with a full width at half maximum of 172 nm upon 460 nm excitation. The internal/external quantum efficiencies of LiInGe2O6:Cr3+are measured to be 81.2% and 39.8%, respectively. The absorption of the phosphor matches well with commercial blue LEDs. Using the fabricated phosphor converted LED illuminating human palm, distribution of blood vessels can be clearly recognized under a NIR camera. These results indicate that LiInGe2O6:Cr3+is a promising candidate to be used in future non‐destructive biological applications.

The construction and modulation of responsive fluorescent materials and nano-assembly with luminescence in solid state

The supramolecular assembly was prepared by combining 16-alkyl (ferrocenyl-methyl) ammonium bromide (Fc16AB) and fluorescein sodium (FS) via the ionic self-assembly (ISA) strategy. The obtained Fc16AB-FS assembly performed multiple responsiveness and hierarchical fluorescence intensity to varied modulation, including redox and β-CD inclusion. The mechanisms of fluorescence quenching triggered by photo-induced electron transfer (PET) and fluorescence enhancement led by aggregation-induced emission enhancement (AIEE) were analyzed in detail. At the same time, The Fc16AB-FS/SiO2 nanoparticles prepared by water-in-oil reverse microemulsion method showed luminescence behaviors in solid state with fluorescence emission at 523 nm, which could be used to prepare fluorescent film to obtain white-luminescence by combining commercial blue LED. By combining ISA strategy with reverse microemulsion method, a novel synthesis method of fluorescent nanoparticles was presented, which broadened the application of template method in preparing fluorescence nanomaterials.

BaY1·95Al2Ga2SiO12:0.05Ce3+: A novel green-emitting phosphor with extra-high quantum yield, small thermal quenching and excellent water resistance for high-color-rendering white LEDs

It is well known that green-emitting phosphor plays a key role in a phosphor-converted white LED with high color rendering index. Here, a novel green phosphor BaY1·95Al2Ga2SiO12:0.05Ce3+ with high quantum yield, low thermal quenching and excellent water resistance is reported. The green phosphor can be easily prepared by the conventional solid-state reaction method at 1325 °C for 4 h in a reducing atmosphere. The compound is cubic and crystallizes in space group Ia3‾d with refined lattice parameters of a = 12.1451(3) Å. The phosphor can be effectively excited by the mainstream commercial blue LEDs (445–465 nm), its emission peak is observed at 517 nm and the absolute quantum yield under 450 nm excitation is as high as 96.2% at 25 °C. The green phosphor exhibits good resistance toward thermal quenching, with the luminescence intensity at 150 °C only decreasing by 11% of the value at 25 °C. In addition, the green phosphor has a very good water resistance, and its luminescence intensity remains almost unchanged when it is soaked in water for more than 300 h. The white LED fabricated by employing the green phosphor shows excellent optical properties with Ra = 92.4, CCT = 3304 K and CIE 1931 chromaticity coordinates as (x = 0.4178, y = 0.3985). All experimental results indicate that BaY1·95Al2Ga2SiO12:0.05Ce3+ is an outstanding green phosphor which has great potential to be used for the phosphor-converted white LEDs with excellent color rendering.

Selective C-C Bond Scission of Ketones via Visible-Light-Mediated Cerium Catalysis

Summary Here, we report a general catalytic manifold for the selective C–C bond scission of ketones via the exploitation of the ligand-to-metal charge transfer (LMCT) excitation mode. Through a cooperative utilization of Lewis acid catalysis and LMCT catalysis, the C–C bond of ketones could be selectively and effectively cleaved, enabling the installation of different functionalities at each carbon of the cleaved C–C bond through a sequential and orthogonal manner. This reaction manifold serves as a photocatalytic alternative to the Norrish type I reaction with the combination of visible light and inexpensive cerium salts. Under operationally simple conditions, a wide range of acyclic and cyclic ketones, from simple strained cyclobutanones to complex androsterone with less strained cyclopentanone moiety, could be successfully transformed into versatile chemical building blocks.

Sulfinates and sulfonates as high performance co-initiators in CQ based systems: Towards aromatic amine-free systems for dental restorative materials

ObjectiveThe aim of our study is to develop amine-free photoinitiating systems (PISs) for the polymerization of representative dental methacrylate resins under blue light irradiation. PISs based on camphorquinone (CQ)/sulfinate and CQ/sulfonate, eventually in combination with an iodonium salt, are proposed and compared to the well-established CQ/amine system. The polymerization performances of thick (1.4 mm) samples of different methacrylate blends upon exposure to a commercial blue LED centered at 477 nm under air are described. Finally, the performances of the new developed PISs are evaluated for dental composites application. MethodsFTIR is used to monitor the photopolymerization profiles. ESR spectroscopy and electrochemical experiments are used to identify the radicals generated. Mechanical properties measurements and color stability measurements are carried out to determine the key properties of the dental composites prepared. Results and SignificianceThe performances of the new proposed PISs for the photopolymerization of thick (1.4 mm) samples of methacrylate upon exposure to a blue dental LED under air are excellent. Similar or better performances and bleaching properties are obtained with the new proposed amine-free systems compared to those reached with the CQ/amine reference system. Dental composites with excellent mechanical properties and exceptional color stability are obtained. The involved chemical mechanisms for the initiation step were also established.

A Sensitive, Specific and Simple Loop Mediated Isothermal Amplification Method for Rapid Detection of Campylobacter spp. in Broiler Production

Campylobacteriosis is one of the most common foodborne diseases worldwide. Two Campylobacter species – C. jejuni and C. coli in poultry and poultry products are considered to be the main source of human campylobacteriosis. Therefore, studying Campylobacter status in poultry flocks is needed to prevent transmission of disease and reduce human risk, health cost, and economic losses. In this study, we adapted and used a Loop-Mediated Isothermal Amplification (LAMP) assay for specific, sensitive, simple and cost-effective rapid detection of C. jejuni and C. coli in the poultry production chain. Amplified LAMP products were detected using a small, low-cost portable commercial blue LED transilluminator and a direct visual detection strategy was demonstrated. By using optimized conditions for amplification a limit of detection (LOD) of 50 CFU/ml was achieved for testing of C. jejuni and C. coli in spiked chicken feces without enrichment. The method took 60–70 min from receiving the samples to the final results (including 30 min for amplification). The optimized LAMP showed a relative accuracy of 98.4%, a specificity of 97.9%, and a sensitivity of 100% in comparison to real-time PCR method. Cohen’s kappa index also showed an excellent agreement (0.94) between the two methods. The results showed that the method is specific, sensitive and is suitable to develop for rapid detection of Campylobacter spp. at poultry production.

Come to light: Detailed analysis of thermally treated Phenyl modified Carbon Nitride Polymorphs for bright phosphors in lighting applications

Carbon Nitride and its polymorphs have recently gained large interests for their huge properties and applications in different fields, from lighting to photocatalysis. Further, several attempts were recently devoted to tune and control its optical and electrical properties. In this report we analyze phenyl modified Carbon Nitride structures obtained by simple thermal polymerization at different temperatures (250–400 °C) of the starting precursor: 2,4-diamino-6-phenyl-1,3,5-triazine. A multi-technique experimental data (XRD patterns, Raman, TGA and DTG, steady- time and time resolved Luminescence, Photoluminescence Excitation spectra, Reflectivity spectra) was applied to analyze the relationship between structural and optical properties and to give more insight on the effect of synthesis procedure on the final polymer. The optical properties evidenced an interesting shift towards the visible region of the absorption spectrum of the phenyl modified g-C3N4 polymer that, associated with the high optical quantum yield (about 60%) and to a broad emission in the green-red spectral region, makes the samples very suitable for lighting applications. Indeed, we report a first prototype of white LED emission by assembly of a commercial blue LED and the Phenyl modified g-C3N4 powders as phosphor, verifying the structural and optical stability over about 10,000 working hours.

Visible‐Light Facilitated Fluorescence “Switch‐On” Labelling of 5‐Formylpyrimidine RNA

AbstractLabelling and detecting 5‐formylpyrimidine is essential to understand its biological function. Herein, we describe a visible‐light triggered and catalyst‐free reaction in which 5‐formylcytidine RNA can be selectively labelled with 2‐thioaniline under the irradiation of a commercial blue LED light to generate fluorogenic 5‐(benzothiazol‐2‐yl) cytidine.magnified image

Introduction of Triboelectric Positive Bioplastic for Powering Portable Electronics and Self-Powered Gait Sensor

Triboelectric nanogenerators (TENGs) are in the center of alternative energy scavenger technologies because of numerous possible applications in remote energy harvesting and self-powered sensing. Although there exists a large number of triboelectric negative polymers, the choice of triboelectric positive polymers is indeed limited. Here we report for the first time the use of thermoplastic starch (TPS) as a triboelectric positive material for designing TENGs. Our bioplastic-based highly durable TENG (b-TENG) can generate open-circuit peak-to-peak output voltage of ∼560 V with output current density of ∼120 mA m–2 and instantaneous output power density of 17 W m–2. We demonstrate b-TENG as a portable power source by powering more than 100 commercial blue LEDs, LED strips, and seven segment LCD screens. Additionally, the b-TENG can be used as a self-powered pedometer for step counter, a speedometer for human walking and running, and a human gait analysis sensor to assess physical activity breeding its futuristic biomedical applications for healthcare purposes. The introduction of eco-friendly bioplastic TPS as a triboelectric positive component has great potential for biomedical applications because of the abundance, biodegradability, low cost, and ease in fabrication process.

A triboelectric nanogenerator based on cosmetic fixing powder for mechanical energy harvesting

In this work, we use commercial powder particulates (a cosmetic fixing powder) as triboelectric materials for constructing a triboelectric nanogenerator (CFP-TENG). Through finger pressing, the CFP-TENG generated approximate open-circuit voltage, short-circuit current, and maximum power density values of 1141 V, 521 µA, and 570.96 μW/cm2, respectively. Thirty-seven commercial blue LEDs can be easily lit up by the CFP-TENG. Moreover, this TENG, which was designed as a novel palette structure for harvesting mechanical energy from bicycle motion, serves as a self-powered bicycle speed sensor. In addition, the cosmetic fixing powder can be used as an effective material to enhance the triboelectric property of skin. This study provides an effective method for developing a cost-effective TENG without the use of complex surface micro-/nano-texturing.

Warm‐white light performance of Dy3+, Eu3+: NaLa(WO4)2 phosphors excited with a 450‐nm LED

AbstractDy3+, Eu3+: NaLa(WO4)2 phosphors are successfully synthesized through the solid‐state reaction technique. The phase‐structure and morphology are measured via X‐ray diffraction and energy dispersive spectrometry. The concentrations of Dy3+, Eu3+, La3+, and W6+ are measured via ICP. The absorption and excited spectra are presented, which indicate that a blue band ranging from 430 to 480 nm is suitable for excitation. Using a commercial blue LED with a wavelength of 450 nm as the excitation light source, emission spectra for samples with varying dopant concentration ratios of Dy3+ to Eu3+ are obtained, which show good tunable yellow and red emission. For the purpose of investigating white LED performance, CIE spectra and a white light photo are also presented. The results reveal that varying the dopant concentration ratio of Dy3+ to Eu3+ plays a key role in the warm‐white performance. With increasing concentration of Eu3+, the correlated color temperature decreases from 4069 to 3172 K, which indicates good warm‐white performance.

Large enhancement of transduction coefficient in PZN-PZT energy harvesting system through introducing low-εr PIN relaxor

Designing piezoceramics with a large transduction coefficient (d33×g33) is key to improving the power generation of piezoelectric energy harvesters (PEHs). However, in popular PEH materials such as Pb(Zn1/3Nb2/3)O3-Pb(Zr1/2Ti1/2)O3 (PZN-PZT), the same trend in the variation of d33 and εr makes it difficult to achieve a large d33 × g33. In this work, we introduced low-εr Pb(In1/2Nb1/2)O3 (PIN) into the PZN-PZT matrix to pull down the εr of the quaternary system. This simultaneously stabilized d33 in a certain range due to the refinement of the domain structure and increased the electrostrictive coefficient (Q33), and consequently the d33 × g33 value increased to 16081 × 10−15 m2/N for the optimal composition. We assembled a cantilever beam type PEH from the preferred material with a power density up to 3.37 μW/mm3 at 1 g acceleration, and demonstrated its use to charge an electrolytic capacitor to drive commercial blue LEDs and a speed sensor.

A flexible self-poled piezoelectric nanogenerator based on a rGO–Ag/PVDF nanocomposite

A self-poled rGO–Ag/PVDF nanocomposite based nanogenerator is shown with proper material characterization that can light twenty commercial blue LEDs, charge capacitors and harvest biomechanical energy.