Commercial LED Research Articles

Enhancement of 1532 nm emission in Ce3+, Er3+ co-doped Ca1.5Y1.5Al3.5Si1.5O12

Near-infrared emission material, C e 3 + , E r 3 + co-doped C a 1.5 Y 1.5 A l 3.5 S i 1.5 O 12 has been synthesized via a high-temperature solid-state reaction method. The luminescence intensity of 1532 nm emission excited with 455 nm increases 4.2 times after the introduction of C e 3 + ions because of C e 3 + → E r 3 + radiation-reabsorption energy transfer and nonradiative energy transfer sensitization as well as the 4 I 11 / 2 ( E r 3 + ) + 2 F 5 / 2 ( C e 3 + ) → 4 I 13 / 2 ( E r 3 + ) + C e 3 + ( 2 F 7 / 2 ) cross relaxation between C e 3 + and E r 3 + ions. The result shows that the developed material is convenient to obtain high-efficiency, near-infrared emission using a commercial blue GaN LED as a pumping source.

Self-templated one-step hydrothermal synthesis of hierarchical actinomorphic flower-like SnO2-ZnO nanorods for high-performance supercapacitor application

• A unique actinomorphic flower-like SnO 2 nanostructure was synthesized via the one-step hydrothermal method. • Achieved high specific capacitance is 797.23 F/g at 1 A/g current density and capacitance retention is 88.2% and coulombic efficieny is 98.7 %. In this paper, we demonstrate the unique actinomorphic flower-like morphology of a tin oxide -zinc oxide (SZ) nanocomposite that has been synthesized using a one-step hydrothermal method and investigated for supercapacitor (SC) application. The optical, morphological and elemental composition features of pure SnO 2 and SZ nanocomposite were carried out by using different characterization techniques such as XRD, FTIR, FESEM, HRTEM, and XPS. The SZ-10 nanocomposite was the most significant one and was used in the fabrication of all solid-state symmetric supercapacitor. Electrochemical analysis of the Galvano charging-discharging (GCD) curves achieved a high specific capacitance (Csp) of 797.23 Fg −1 at a current density (CD) of 1 Ag −1 . The cyclic voltammetry (CV) curve for the SZ-10 electrode shows the high Csp of 548.56 Fg −1 at a scan rate of 10 mV/s. It has superior cyclic stability with capacitance retention of 88.2% and coulombic efficiency of 98.7%, even after 5000 repetitive cycles. The SZ-10 electrode also shows a high energy density (ED) of 45.72 Whkg −1 and a power density (PD) of 406 Wkg −1, at a CD of 1 Ag −1 . Furthermore, the fabricated SC device is linked in series to turn on a commercial red LED that glows for 1 to 2 min. These investigations demonstrate that the SZ-10 nanocomposite is an excellent electrode material for high-energy storage devices for SC applications.

A novel polarization-free 3D printing strategy for fabrication of poly (Vinylidene fluoride) based nanocomposite piezoelectric energy harvester

The preparation of piezoelectric materials could provide the new opportunities for capturing the attractive green energy. In this work, a novel polarization-free fused filament fabrication (FFF) 3D printing strategy was proposed for fabrication of a high piezoelectric poly(vinylidene fluoride) (PVDF)/tetraphenylphosphonium chloride (TPPC) nanocomposite energy harvester . It was experimentally found that after incorporating with TPPC nanoparticles , a high β-based polar phase concentration of approximately 83.8% could be achieved for the prepared PVDF/TPPC nanocomposites. In addition, combined with the FFF 3D printing technology, the complex porous structures of the energy harvester was realized, thus resulting in the desired excellent flexibility and piezoelectricity . Typically, for the smart 3D printed nanocomposite energy harvester with incorporation of only 5 wt% TPPC, the obtained open-circuit voltage could be up to 6.62 V, which is approximately 5 times higher than that of neat PVDF and could even successfully drive five commercial green LED lights to normally work. Encouragingly, this novel technique provides a new idea for design and fabrication of piezoelectric energy harvester, and opens up some new possibilities for the FFF 3D printed piezoelectric parts to be applied in various fields such as wireless sensor networks , health care, environmental monitoring and industries. The piezoelectric poly(vinylidene fluoride) (PVDF)/tetraphenylphosphonium chloride (TPPC) nanocomposite energy harvester with complex porous structures was successfully fabricated by FFF 3D printing, which exhibited an excellent piezoelectric performance with maximum output voltage of 6.62 V and could drive five green LEDs. • The piezoelectric PVDF/TPPC energy harvester was fabricated via a novel polarization-free FFF 3D printing strategy. • The effective combination of TPPC nanoparticles incorporation and FFF 3D printing could result in 83.8% β-based polar phase. • The FFF 3D printed complex porous structures could amplify the stress–strain effect and lead to the desired piezoelectricity. • Application of FFF 3D printed piezoelectric parts in the field of energy harvesting can be expected.

Design of a novel LED bulb with entire surface thermally activated for passive cooling

• A novel LED bulb was proposed to thermally activate the lampshade for cooling. • The novel design contained a chimney inside the bulb and an external heat sink. • Two parallel heat dissipating paths within the bulb were revealed. • The chimney structure and chip distribution were optimized. • Cooling capacity of the optimal bulb was 1.6 times larger than conventional design. LED lightings have made significant contributions to global energy saving, where one major challenge is the overheating of LED chips since the light output and lifespan of LED chips decrease exponentially with increasing operating temperature. Restricted by cooling capacity, the power input and light output of a LED bulb is limited. At present the luminous flux of commercial LED bulbs (A19 size) is usually limited to 800 lm with the related power consumption within 9 W. Therefore, there is an urgent market need for high-lumen bulbs while maintaining the size and shape as conventional incandescent bulbs. We report herein a novel design which could make full use of the entire outer surface of LED bulb as heat dissipating surface under passive cooling conditions. The novel design contains a chimney inside the bulb and an external heat sink, enabling two parallel heat dissipating paths, i.e. , chips - heat sink - environment and chips – chimney – lampshade - environment . In conventional design with an external heat sink for cooling, the lampshade functions only to transmit light rather than dissipate heat. However, in the novel design the chimney inside the bulb could thermally activate the lampshade to dissipate heat as well. Upon properly distributing thermal loads to the two heat dissipating paths, cooling capacity of the novel bulb was optimized. With this design strategy, the passive cooling capacity was significantly improved to be 1.57 times higher than the conventional design and the commercially available bulbs of the same size and shape. Most importantly, the design strategy may be extended to other passive cooling scenarios such as indoor small cells for 5G communication.

Enhanced Kevlar-based triboelectric nanogenerator with anti-impact and sensing performance towards wireless alarm system

An enhanced Kevlar-based triboelectric nanogenerator (EK-TENG) with excellent safeguarding and stable sensing capability in harsh loading environments was developed by integrating shear thickening materials and graphene on Kevlar fabric. EK-TENG, whose maximum peak power density reached as high as 25.8 mW/m2 under oscillator loadings of 40 N and 10 Hz, could directly power commercial LEDs, capacitors and supercapacitors. In addition, the 30-layer EK-TENG with the greatest fiber friction dissipated drop hammer impact force from 1820 N to 439 N under low-speed impact. EK-TENG with anti-ballistic property enabled to resist 126.6 m/s bullet shooting which was higher than 90.1 m/s of neat Kevlar. Besides, EK-TENG effectively absorbed and dissipated 87.4% of the explosion wave energy under blast loading which exhibited excellent safeguarding properties. Furthermore, EK-TENG could generate voltage signals under various impact loadings which could act as self-powered sensor to monitor external stimuli. Finally, a smart TENG-based wireless passive sensor alarm system with high sensitivity was designed to monitor and warn impact dangers, which opened up a new avenue for the development of next generation intelligent protective clothing.

Development of a Sustainable and Biodegradable Sonchus asper Cotton Pappus Based Piezoelectric Nanogenerator for Instrument Vibration and Human Body Motion Sensing with Mechanical Energy Harvesting Applications.

Energy harvesting from natural resources has gained much attention due to the huge increase in the demand for portable electronic devices and the shortage of conventional energy resources in general. In the present work, the fabrication and realistic applications of a piezoelectric nanogenerator (PENG) using polydimethylsiloxane (PDMS) and the abundantly available, environment-friendly natural fiber Sonchus asper (SA) have been discussed. The biocompatible, low-cost SA fibers were flexible enough and showed high piezoelectric properties as active materials in the study. The SA pappus based piezoelectric nanogenerator demonstrated its ability to convert the harvested biomechanical energy into electrical energy from the various mechanical energy sources available in our environment. The SA pappus/PDMS thin film based piezoelectric nanogenerator (SPENG) fabricated in the laboratory showed colossal output performances (open circuit output voltage, VOC ∼81.2 V; short circuit current, ISC ∼1.0 μA) by continuous finger impartation. Uniform output performance was also obtained by the application of uniform force on the devices (e.g., ∼42 V for 5 N force at 10 Hz frequency). The SPENG was capable to charge a 2.2 μF capacitor to 3.2 V within a short time span (16 s) under continuous finger impartation and illuminate 39 commercial high-power blue LEDs that were connected in series. Thus, the fabricated SPENG can be used as a green and portable energy source to power up portable electronic devices. Apart from this, the SPENG may also be used as a self-powered energy supply for pacemakers or different types of health care units if properly improvised.

White light-emitting ZnO nanoparticles exhibiting color temperature tunability with near UV excitation and high color rendering

The development of high-quality white-light phosphor for lighting and their facile synthesis is highly desired. Achieving white-light emission in undoped metal-oxides is in great demand, and hence ZnO being a potential phosphor was explored. However, tailoring defect-oriented emissions that mainly depend on processing conditions is challenging. Annealing effects on ZnO to obtain white-light with completely diminished near band-edge emission is detailed here. A systematic variation of processing temperature, ambient pressure, and ambient gas helped tailor the white-light emission. Optimized ZnO nanophosphors emitted white-light with the near-ideal Commission International de l’Eclairage (CIE) coordinates (x = 0.32, y = 0.33 at λex = 325 nm) and correlated color temperature (CCT) of 6200 K (corresponding to day white-light). Optimized processing conditions achieved neutral white-light (x = 0.33, y = 0.33 at λex = 340 nm) and CCT 5645 K. ZnO nanoparticles exhibit excellent color rendering index (CRI) of >90 and high R9 values up to 97%, essential in efficiently rendering object colors compared to that under sunlight. Phosphor-converted white light-emitting diodes (pc-WLEDs) were fabricated on commercial LEDs using the prepared ZnO nanophosphors. pc-WLEDs emitted neutral and day white-light, well-suited for indoor solid-state lighting devices.

Flexible pillar-base structured piezocomposite with aligned porosity for piezoelectric energy harvesting

Flexible piezoelectric energy harvesters have attracted significant attention in recent years due to their ability to convert strain energy associated with bending into electrical energy for low-power wearable electronic devices. Compared with 0–3 type piezoelectric composites, where the piezoelectric phase is isolated within the material, flexible piezoelectric energy harvesters based on a three-dimensional interconnected ceramic skeleton are of particular interest due to their high stress transfer capability and high piezoelectric coefficients. Herein, a three-dimensional interconnected porous barium calcium zirconate titanate (BCZT) pillar-based structure is created via freeze casting, where polydimethylsiloxane (PDMS) is impregnated into the aligned pore channels to form a flexible piezoelectric energy harvester. The effect of porosity on piezoelectric coefficients, ferroelectric properties and energy harvesting performance is investigated in detail. The piezoelectric coefficient and energy harvesting figure of merit are significantly enhanced due to the presence of an aligned pore structure which leads to a high transfer of applied stress into the piezoelectric phase. The highly aligned porosity leads to the creation of a piezoelectric composite with 60 vol% of polymer that exhibits a high output voltage of 30.2 V and current of 13.8 μA. Moreover, the peak power density can reach up to 96.2 μW cm −2 , which is significantly higher than that of nanoparticle-based piezoelectric composites. This work demonstrates a promising prospect of utilizing flexible piezoelectric composites for energy harvesting applications. A flexible piezoelectric energy harvester based on BCZT pillar-base composite with aligned porosity is achieved via a freeze casting technique. Enhanced piezoelectric properties and energy harvesting performance ( V = 30.2 V, I = 13.8 μA at a porosity of 60 vol%) are realized due to the high poling efficiency and improved stress transfer, which is capable of charging capacitors and illuminating commercial LEDs. • Flexible pillar-base structured piezocomposite with highly aligned porosity is developed via freeze casting. • The piezoelectric energy harvesting performance is significantly enhanced due to the presence of an aligned pore structure. • Piezoelectric composite with 60 vol% of polymer exhibits a maximum power density of 96.2 μWcm −2 . • It is demonstrated to have the ability to charge capacitors and illuminate commercial LED bulbs.

Green triboelectric nanogenerator based on waste polymers for electrophoretic deposition of titania nanoparticles

Nowadays, with the development of electronic devices and the internet of things (IoT), there is a growing demand for an available, eco-friendly and endless power supply. Triboelectric nanogenerator (TENG), which converts wasted mechanical energy to electricity, is an alternative to batteries for power generation. TENGs are usually fabricated from polymers, and there are already great quantities of waste polymers in the environment that concern animals, wildlife and humans. Therefore, in this work, several eco-friendly, simple and low-cost TENGs were crafted using waste polymers like polyurethane foam (PU), expanded polystyrene (PS), polypropylene (PP), polyethylene foam (PE) and melamine formaldehyde foam (MF) without performing any physical or chemical functionalization on them. Finite element analysis was performed for each TENG and simulation results supported our experimental findings. Among these TENGs, voltage and power density of 1830 V and 96.68 mW/cm2 were achieved over a 3 × 3 cm2 area of M-TENG. This TENG could turn on 100 commercial blue light LED. The TENG with Melamine formaldehyde foam as a tribo-positive layer (M-TENG) also showed high mechanical robustness and its output did not change after 10,000 contact and separation cycles. To examine M-TENG utilization for high voltage practical application, M-TENG was used as a power source of electrophoretic deposition. The obtained high-quality titanium dioxide coating was uniform with no microcracks.

Investigating the role of chalcogen atom in the piezoelectric performance of PVDF/TMDCs based flexible nanogenerator

The current work shows first of its kind, where the systematic effect of the chalcogen atom of the Transition metal dichalcogenides (TMDCs) (MoS2, MoSSe, MoSe2) and polyvinylidene fluoride (PVDF) based composites on the piezoelectric performance of the fabricated piezonanogenerator has been investigated. Flexible PVDF/TMDCs composite thin films have been synthesized to check the effect of TMDCs as a filler in the PVDF matrix. Raman and FTIR spectroscopy revealed the enhancement of piezoelectric behavior due to increase in the polar β-phase content of PVDF after addition of TMDCs in PVDF. Out of all the fabricated piezonanogenerator, the PVDF/MoSSe based nanogenerator showed the maximum peak to peak open circuit voltage of 31.2 V and short circuit current of 1.26 μA. This enhancement was achieved just by adding TMDCs without any further treatment. The enhanced piezoelectric performance is attributed to the synergistic contributions from inherent piezoelectricity of synthesized TMDCs and intensified β-phase for the PVDF/TMDCs composites. The highest output voltage for the PVDF/MoSSe device is ascribed to the lack of reflection symmetry in MoSSe structure. The generated voltage was also used for lightning a commercial LED and for charging of a capacitor of 4.7 μF.

Self-Powered Smart Arm Training Band Sensor Based on Extremely Stretchable Hydrogel Conductors.

The development of elastic electronic technology has promoted the application of triboelectric nanogenerators (TENGs) in flexible wearable electronics. However, most of the flexible electronics cannot achieve the requirements of being extremely stretchable, transparent, and highly conductive at the same time. Herein, we report a TENG constructed using a double-network polymer ionic conductor sodium alginate/zinc sulfate/poly acrylic-acrylamide (SA-Zn) hydrogel, which exhibited outstanding stretchability (>10,000%), high transparency (>95%), and good conductivity (0.34 S·m-1). The SA-Zn hydrogel TENG (SH-TENG) could harvest energy from typical human movements, such as bending, stretching, and twisting, which could light up 234 green commercial LEDs easily. Additionally, the SH-TENG can be used to prepare a self-powered smart training band sensor for monitoring arm stretching motion. This work may provide an innovative platform for accessing the next generation of sustainable wearable and sports monitoring electronics.

Anti-stress ball energy harvester

Advances in flexible energy harvesters, via converting the ambient energy into electricity, have highly motivated to realize self-powered flexible electronics. However, the requirements for higher current output have been still an urgent challenge for soft energy harvesters. Herein, we present a new type of magnetoelectric soft sphere (MSS) with a portable pluggable interface, which is capable of mechano-electrical conversion via external forces in arbitrary directions, such as hand pressing or gripping. The MSS is composed of liquid metals, magnetic Nd2Fe14B particles and Ecoflex elastomer. Notably, the MSS can break the limitation of saturated surface charge density, resulting in a current density as high as ~10 A/m2. As an anti-stress ball generator, the handheld MSS when repeated compression not only successfully triggers the luminescence of a commercial red LED and the display of an LCD, but also enables the normal working of a calculator. Our study provided here will open new avenues for the design of fully-flexible energy harvesters to convert surrounding mechanical energy to electricity.

Self-assembled 3D graphene-based aerogel with Au nanoparticles as high-performance supercapacitor electrode

Construction of porous three-dimensional (3D) heterostructured materials is promising for establishing high-performance energy-storage devices, enabling large surface area, facilitated ion and electron transport, and synergistic effects between multi-components. Here, we report a simple and cost-efficient freeze-casting method to improve the electrochemical performance of porous 3D graphene aerogel (GA) embedded with gold nanoparticles (3D Au/GA). The as-synthesized 3D Au/GA was broadly characterized by XRD, Raman, XPS, SEM, and TEM. Morphology observations show that 3D-porous cellular structure of GA with uniform distribution of 20 nm Au nanoparticles on the surface of GA. Based on structural merits, the electrochemical performance of as-synthesized porous 3D Au/GA was exemplified as electrode materials for supercapacitor with a high specific capacitance of 554 F g−1 at 5 mVs−1, excellent cycling stability with capacitance retention of 91.06% after 10,000 cycles, and exhibits significantly specific energy of 10.7 W h kg−1 at a specific power of 203.5 W kg−1. This could be ascribed to the synergetic effect of conducting Au and the unique 3D porous, cellular structure of GA. In addition, the developed electrode materials are used to fabricate a symmetric solid-state supercapacitor (SSC) device for demonstrating the practical applicability, and it was able to light a commercial LED. Our method opened a new direction to synthesize porous 3D GA with various nanoparticle decorations for numerous applications as energy storage devices, catalysis, sensors, biomedical, and environmental applications.

Mechanochemical Preparation and Self-Assembly of Protein:Dye Hybrids for White Luminescence.

Protein nanofibrils (PNFs) functionalized with multiple dyes are prepared by a combination of mechanochemistry and liquid-phase self-assembly. The three employed dyes are Fluorescent Brightener 378 (F378), 2-butyl-6-(butylamino)-1H-benzo[de]isoquinoline-1,3(2H)-dione (Fluorol 555), and Nile red (NR). F378 acts as the donor with Fluorol 555 as the acceptor. F555 in turn acts as the donor and NR as the acceptor. This enables a FRET cascade that enables conversion of UV light to white light. The efficiency of FRET can be influenced by the details of the self-assembly process. If proteins milled with different dyes are mixed prior to self-assembly, nanofibrils are formed containing all three dyes, thus favoring FRET processes. By tuning the ratio of the three luminescent dyes, PNF dispersions are obtained that display bright white light emission. Moreover, the PNF dispersions can be converted into white luminescent films and gels where the PNFs may help to organize dye molecules. Additionally, the PNF materials can be employed as coatings on commercial LEDs, enabling emission of white light.

From carbon nanotubes to highly adaptive and flexible high-performance thermoelectric generators

Flexible thermoelectric generators (TEGs) provide a sustainable solution for directly harvesting low-grade heat from various curved surfaces, presenting a promising potential for feeding energy to personal-electronics or internet-of-things systems. Nevertheless, the room-temperature millivolt output of the cutting-edge all-solid-state flexible material-based TEGs (AF-TEGs) is still unappeasable for flexible electronics in practical applications. Here, we report on an AF-TEG consisting of a 3-level structure based on thin-film carbon nanotube (CNT) assemblies that can generate a high voltage (1.05 V) and sufficient outpower (0.95 mW) at moderate ΔT (~44 and 39 K, respectively) for powering an electrochromic device. The advanced nature of the AF-TEG is that conformation is highly adaptive and programmable, showing the surface suitability which can capture waste heat in both in-plane and out-of-plane direction. Moreover, an AF-TEG power management scheme is proposed for powering a commercial LED and an electronic thermometer, which indicate promising potential for practical applications.

A Hybrid Materials Approach for Fabricating Efficient WLEDs Based on Di‐Ureasils Doped with Carbon Dots and a Europium Complex

AbstractWhite light‐emitting diodes (WLEDs) revolutionized the lighting industry providing high energy efficiency and a long lifetime. The recent development of efficient ultraviolet (UV) LEDs pushed forward the development of WLEDs based on mixtures of down‐shifting phosphors and the current challenges are focused on the design of sustainable light converting materials with tunable correlated color temperature (CCT) and high color rendering index (CRI). Here the authors report a simple route to design sustainable WLEDs with tunable and enhanced color features through the assembly of a commercial LED chip (400 nm) and flexible films of a di‐ureasil hybrid comprising a mixture of a cyan component originating from amorphous carbon dots and a red one resulting from the Eu(tta)3(bpyO2) (tta−: 2‐thenoyltrifluoroacetonate and bpyO2: 2,2′‐dipyridyl‐1,1′‐dioxide) complex. This red emission is responsible for high CRI arising from an unprecedented efficient energy bridge between bpyO2 and tta− excited states mediated by the hybrid host, as modeled by theoretical calculations based on the density functional theory and intramolecular energy transfer. WLED prototypes were fabricated with a tunable CCT from cold (5796 K) to warm (4228 K) white‐light with high CRI values of 89 and 84, respectively, outperforming the state‐of‐the‐art of UV‐based WLEDs.

Defects engineering of Fe2O3@Sn2O3 nanosheet arrays for high-performance hybrid supercapacitor

Developing new-type electrode materials with high surface area, stable microstructure and high performance is important to global sustainability. Herein, we successfully fabricate an oxygen-deficient Fe2O3@Sn2O3 nanocomposite composed of Fe2O3 and Sn2O3 nanosheet-arrays on Ni foam. Benefiting from this kind of binder-free nanosheet-arrays microstructure and the oxygen vacancy, the electrode oxygen-deficient Fe2O3@Sn2O3 (VO-Fe2O3@Sn2O3) nanocomposite possesses an excellent specific capacity (694.8 C g−1) at a current density of 1 mA cm−2, superior rate capability (it still maintains 477.6 C g−1 at 10 mA cm−2), and long cycle stability. The hybrid supercapacitor, assembled with VO-Fe2O3@Sn2O3 nanosheet arrays as the cathode, active carbon (AC) as the anode and polyvinyl alcohol (PVA)/KOH as the gel electrolyte, delivers a high energy density of 39.1 W h kg−1 at a power density of 1.28 kW kg−1 and a retention rate of 81.4% even after 10,000 cycles at 1.6 A g−1. Furthermore, two assembled devices in series can power a commercial LED for a long time.

Effect of repeated heating and cooling cycles on the degree of conversion and microhardness of four resin composites.

This study evaluated the effect of repeatedly heating and cooling four resin-based composites (RBCs) for up to six cycles. Four commercial RBCs were heated to 68°C and cooled to room temperature for up to six cycles before photocuring at 30°C. Specimens spent a total of 0, 30, 60, 90, 120, 150 min, or 7 days at 68°C. The degree of conversion (DC) was measured at the bottom of the specimens immediately after photocuring. The Vickers microhardness was measured at the top and bottom of the RBC surfaces 24 h after photocuring. The data were analyzed using one-way analysis of variance, Dunnett's or Bonferroni post-hoc tests, and Spearman correlation analysis (α=0.05). For two brands of RBC, the DC decreased at various time points; however, these decreases were small, and there was no correlation (negative or positive) between the number of heating cycles and the DC for any of the RBCs. Repeated heated and cooling resulted in small changes in the hardness (compared to the control) in both directions (Dunnett; p < 0.05). Two of the RBCs showed a significant, positive correlation between the number of heating cycles and their hardness at the bottom surface. Repeated heating, cooling, and then reheating the RBCs for up to 1 week had little overall effect on their DC and microhardness values. The 2 mm thick specimens of all four RBCs achieved a bottom: top hardness ratio exceeding 0.8 after a 20 s exposure to light from a commercial LED curing light CLINICAL SIGNIFICANCE: Six repeated dry heating and cooling cycles of up to 1 week in duration had little effect on the DC and the microhardness of four commercial resin-based composites.

Sm3+-doped niobate orange-red phosphors with a double-perovskite structure for plant cultivation and temperature sensing

Sm3+-activated niobate double-perovskite orange-red emitting Ca2LaNbO6 (CLNO) phosphors were prepared using a solid-state reaction at 1300 °C. The purity of the powder phase, crystal structure, morphology, elemental composition, luminescent properties, thermal stability, electroluminescence and temperature sensing properties of the phosphors were comprehensively analyzed. The photoluminescence spectrum obtained under excitation of 407 nm exhibited four intense emissions ascribed to the 4f–4f transitions of Sm3+ ions. The electroluminescence spectrum of an LED device fabricated using a commercial 395-nm LED chip and the optimal CLNO:5%Sm3+ phosphor overlapped with the absorption band of the PR phytochrome state, indicating its potential for use in a plant growth lamp. Furthermore, the systematic variations in the intensity ratios of the two emission or excitation bands of Sm3+ with temperature suggested the potential of the synthesized sample for temperature sensing.

Pulsed LED line light for large-scale PIV—development and use in wave load measurements

In this paper the development of a high-power pulsed LED line light and its use to apply particle image velocimetry (PIV) during wave impact measurements are described. An electrical circuit that generates high-current pulses is designed and built, which is used to overdrive a number of commercially available LEDs. The limit for this overdrive-capacity is determined as function of pulse duration for various commercial available LEDs. Two systems of cylindrical convex lenses are designed to act as a collimator and reduce divergence of the LED bundle and the resulting light sheet properties (maximum light intensity and sheet thickness) are investigated. An array of LEDs of 60 cm length (referred to as the LED line light) is designed and manufactured. For the two lens systems, the LED line light provides proper light sheet conditions to illuminate measurement regions in the order of either 0.3 × 0.3 m2, or 1 × 1 m2, at a sufficiently constant light sheet thickness of 5 mm. The application of the LED line light is demonstrated by quantifying the instantaneous flow field of a wave impacting on a blunt object in a wave flume. PIV measurements are conducted at an acquisition rate of 25 frame pairs per second, quantifying maximum flow velocities in the order of 1.0 m s−1 at a LED pulse width of 200 μs. The system, consisting of the LED line light, a CMOS camera and open source PIV processing software provides the possibility to perform 2D planar PIV measurements for a fraction of the costs of a commercially available laser based PIV system.