High Energy Transfer Efficiency Research Articles

Energy transfer and thermal stability of novel green-emitting Ca3Y(PO4)3:Ce3+, Tb3+ phosphors for white LEDs

A novel thermally high-stable and high-efficiency green-emitting Ce3+/Tb3+ co-doped Ca3Y(PO4)3 phosphor has been successfully synthesized via a conventional solid-state reaction. The energy transfer and thermal quenching of Ca3Y(PO4)3:Ce3+, Tb3+ samples were investigated for the first time. The emission spectra of as-prepared samples presented a blue emission band deriving from the 5d-4f transition of Ce3+ and green emission peaks stemmed from 5D4-7FJ (J = 6, 5, 4, 3) of Tb3+ upon 325 nm excitation. By adjusting Tb3+ concentration, the chromaticity coordinates of as-prepared samples could be tuned from (0.165, 0.028) to (0.301, 0.529) because of the energy transfer of Ce3+→Tb3+ ions. It was demonstrated that the energy transfer mechanism from Ce3+ to Tb3+ ions in Ca3Y(PO4)3 host is the electric dipole-dipole interaction by the energy level diagram and the spectral overlap between the emission spectrum of the donor and the excitation spectrum of the acceptor. The energy transfer efficiency from Ce3+ to Tb3+ ions in Ca3Y(PO4)3 was up to 81%. Beyond that, it affirmed that the emission intensity at 423 K was about 82% of that measured at room temperature (298 K) according to the temperature-dependent emission spectra. Basing on the above analyses shows that the as-synthesized green-emitting Ce3+/Tb3+ co-doped Ca3Y(PO4)3 phosphors with high energy transfer efficiency and excellent thermal stability could be used in phosphor-converted white light-emitting-diodes (LEDs).

Quadruple hydrogen bonded hyperbranched supramolecular polymers with aggregation-induced emission for artificial light-harvesting

In the present work, a tetraphenylethylene (TPE) derivative with four ureidopyrimidinones (TPE-tetraUPy) was synthesized through a two-step reaction, which could make up supramolecular hyperbranched polymers in CHCl3 through quadruple hydrogen bonding interactions with aggregation-induced emission (AIE). The supramolecular hyperbranched polymers were characterized by Fourier transformed infrared (FT-IR), viscosity measurement, 1H NMR spectra, and steady-state spectra. The as-prepared supramolecular hyperbranched polymers can further self-assemble to form nanoparticles in CHCl3/hexane mixture (1:99, v/v) or form nanoparticles in uniform shape and size using the miniemulsion method with cetyltrimethyl ammonium bromide (CTAB) as a surfactant. From the supramolecular nanoparticles prepared in the miniemulsion method, we construct a light-harvesting system to study the excitation energy transfer properties by using the electrostatic assembly of negatively charged sulforhodamine 101 (SR101) on the nanoparticles, which exhibited a high energy transfer efficiency (37.2%) and antenna effect (30.7).

Enhanced mid-infrared emission in Er3+/Tm3+ co-doped tungsten-tellurite glasses

Transparent Er3+/Tm3+ co-doped tungsten-tellurite (TWL) glasses with variable Er3+ concentration were prepared by the conventional melt-quenching method. The samples prepared were investigated by differential scanning calorimetry (DSC), absorption spectra, up-conversion, near and mid-infrared emission and lifetime decays. DSC analyses indicates a high transition temperature (Tg) and a large value of △T. Enhanced 2.7 μm emission in Er3+/Tm3+ co-doped TWL glasses presents its superiority in mid-infrared application. Based on above emission spectra and lifetime decays, the energy transfer mechanism between Er3+ and Tm3+ ions was discussed. Tm3+ ions are an effective sensitization for 2.7 μm emission of Er3+ ions in this glass for its high energy transfer efficiency (83.6%). A comparative study on emission performance suggests that this Er3+/Tm3+ codoped TWL glass is a competent candidates for mid-infrared laser materials.

Sandwich-Structured Upconversion Nanoprobes Coated with a Thin Silica Layer for Mitochondria-Targeted Cooperative Photodynamic Therapy for Solid Malignant Tumors

Upconversion nanoparticles-based photodynamic nanotheranostic agents (UCNPs-PDT) have received great interest due to improved tissue penetration, weak autofluorescence, and low biotoxicity. However, conventional UCNPs-PDT are often limited by low energy transfer efficiency from UCNPs to photosensitizer (PS) molecules and insufficient generation and limited diffusion distance of reactive oxygen species (ROSs). Herein, an "all in one" nanotheranostic agent has been developed which has multicolor sandwich-structured UCNPs (SWUCNPs) as the core, a thin silica layer with a mitochondria-targeted group for loading dual PS as the medium layer, and polyethylene glycol-folic acid (PEG-FA) chains as the outer layer. Multicolor SWUCNPs simultaneously achieve two-photon fluorescence imaging and serve as energy donor for dual PS molecules. The thin luminescence layer and silica layer control most UCNPs activators and PS molecules in the effective energy transfer distance to guarantee a high energy transfer efficiency. Via FA-mediated endocytosis, the nanotheranostic agent is selectively endocytosed by cancer cells, is released from the endosome/lysosome, targets the mitochondria, and in situ produces ROSs under excitation from NIR, leading to significant mitochondria-mediated cell apoptosis. Furthermore, the established nanotheranostic agent shows tumor targetability, increased generation of ROSs, high PDT efficacy, significant cell apoptosis, minimal systemic cytotoxicity, and efficacious in vivo tumor inhibition.

Innovative silicon compatible materials for light emitting devices

The paper reports the potentialities of innovative silicon compatible materials for light emitting devices. In particular thin films of Er doped yttrium oxide have been synthesized by a technique totally compatible with ULSI processes. Through the structural characterization, we will verify the high stability of the film and the good dopant dissolution. Moreover, by the investigation of the optical properties, we will demonstrate that the use of this compound is effective to introduce more than 10 21 Er/cm 3 in optically active state, value that cannot be reached in other Si compatible materials. The influence of Er content on the optical properties will be described in details. Moreover, we will propose the introduction of a proper sensitizer for Er, bismuth, in the same thin film. In particular, we will show that the (Er+Bi) co-doped yttrium oxide is a perfect host to overcome another important drawback of Er doped materials that is its low absorption cross section. The influence of Bi and Er contents on optical properties will be extensively discussed along the paper. Through the optimization of ratio between Bi and Er concentrations, high energy transfer efficiency will be reached with simultaneously a consistent increase of the effective Er cross section. A factor of more than three orders of magnitude have been obtained with respect to the direct excitation of Er.

Sr2LiScB4O10:Ce3+/Tb3+: A Green-Emitting Phosphor with High Energy Transfer Efficiency and Stability for LEDs and FEDs.

Exploring new, efficient, and stable phosphors is important and meaningful work for both LEDs and FEDs. Here, the new Ce3+/Tb3+-codoped green-emitting phosphor Sr2LiScB4O10 with high energy transfer efficiency and outstanding stability was designed and prepared by a solid-state reaction. The phosphors show a broad excitation spectrum in the range of 235-375 nm and a narrow green emission spectrum around 544 nm. The strong Tb3+ emission with weak Ce3+ emission and the decreasing lifetime of Ce3+ indicate that the samples have high energy transfer efficiency up to more than 90%. The green emission intensity at 250 °C can keep 75% of its intensity at room temperature with changeless color coordinates, which reveals that the phosphors have excellent thermal stability and color stability. The CL performance indicates that the phosphor possesses high saturation current and saturation voltage with good color stability, and a related luminescence mechanism was proposed to explain the remarkable CL properties. On the basis of the outstanding luminescence performance and thermal and color stability in PL and CL, the phosphor shows promise for applications in LEDs and FEDs.

Highly bright multicolor-tunable KSrLu(PO4)2:Ce3+, Tb3+, Mn2+ phosphors via efficient energy transfer.

Research hotspots about Ce3+-Tb3+ and Ce3+-Mn2+ codoped multicolor-tunable materials, has grown rapidly and is still growing. However, few feasible strategies can be employed to achieve the multicolor-tunable luminescence under the premise of maintaining high QE. In this paper, KSrLu(PO4)2:0.25Ce presents a high luminescence efficiency with approximately 78% quantum efficiency. Furthermore, Ce3+-Tb3+ and Ce3+-Mn2+ codoped optimal samples give a green and red luminescence, which corresponds to a high 61% and 55% quantum efficiency due to a high energy transfer efficiency of Ce3+→Tb3+ and Ce3+→Mn2+. Besides, we achieved the precise adjustment of blue, green, orange and pink emissions of KSrLu(PO4)2:Ce3+, Tb3+, Mn2+ samples. Meanwhile, KSrLu(PO4)2:Ce3+, Tb3+ and KSrLu(PO4)2:Ce3+, Mn2+ phosphors present a weak thermal quenching: their integrated emission intensity at 500K still keep more than 80% of their initial intensity at room temperature. Therefore, the results might provide a novel multicolor-tunable phosphor for backlight display application.

Joule-Level High-Efficiency Energy Transfer to Subpicosecond Laser Pulses by a Plasma-Based Amplifier

Laser plasma amplification of sub-picosecond pulses above the Joule level is demonstrated, a major milestone for this scheme to become a solution for the next-generation of ultra-high intensity lasers. By exploring over 6 orders of magnitude the influence of the incident seed intensity on Brillouin laser amplification, we reveal the importance of a minimum intensity to ensure an early onset of the self-similar regime, and a large energy transfer with a very high efficiency, up to 20%. Evidence of energy losses of the seed by spontaneous backward Raman is found at high amplification. The first three-dimensional envelope simulations of the sub-picosecond amplification were performed, supplemented by one-dimensional PIC simulations. Comparisons with the experimental results demonstrate the capability of quantitative predictions on the transferred energy. The global behavior of the amplification process, is reproduced, including the evolution of the spatial profile of the amplified seed.

Tunable white-light emission of Dy3+ or/and Eu3+ co-doped single-phase LiY(PO3)4 phosphors for NUV-WLEDs

A series of Dy3+ and Dy3+/Eu3+ co-doped LiY(PO3)4 phosphors are prepared by sol-gel combustion method, followed by annealing treatment at 700 °C for 10 min. XRD patterns and TEM images show that the LiY1-m-nDymEun(PO3)4 phosphors are characterized by monoclinic phase and regular short rod or nearly spherical granules. Excited at 363 nm, the Dy3+ single doped LiY(PO3)4 phosphors have two intense emission peaks at 482 nm and 574 nm. Its chromaticity coordinate point is centred at (0.305 ± 0.003, 0.33 ± 0.015) and its CCT is higher than 6700 K. By introducing Eu3+ ions to LiY0.96Dy0.04(PO3)4 phosphors, chromaticity coordinate point and CCT of LiY0.96-nDy0.04Eun(PO3)4 phosphors can be adjusted almost linearly due to energy transfer between Dy3+ ions and Eu3+ ions. The corresponding CCT of 4927–6052 K and chromaticity coordinate point of (0.3334 ± 0.0136, 0.3492 ± 0.0014) can be achieved for LiY0.96-nDy0.04Eun(PO3)4 (n = 0.03–0.05) phosphors with high luminescence thermal stabilities and energy transfer efficiency of more than 18.99%. These results indicate that Dy3+/Eu3+ co-doped LiY(PO3)4 phosphors are expected to be a promising single matrix white emitting phosphors with tunable white-light emission for NUV-WLEDs.

Real-Time Mapping of Ultratrace Singlet Oxygen in Rat during Acute and Chronic Inflammations via a Chemiluminescent Nanosensor.

Sensing nonradiation-induced singlet oxygen (1 O2 ) in whole-animal is deemed as one of the most challenging tasks in noninvasive techniques due to the µs level lifetime of 1 O2 and quenching by numerous reductants in tissues. Here a distinct chemiluminescent (CL) nanosensor (NTPE-PH) that boasts ultrahigh concentrated CL units in one nanoparticle is reported. Taking advantage of the intramolecular energy transfer mechanism that promises high energy transfer efficiency and the aggregation-induced emission behavior that guarantees high CL amplification, the NTPE-PH sensor is sensitive to a nm level 1 O2 . Experiments demonstrate that the NTPE-PH yields a highly selective CL response toward 1 O2 among common reactive oxygen species. With proved low cytotoxicity and good animal compatibility, real-time mapping of ultratrace 1 O2 in whole-animal during acute and chronic inflammations is first achieved. It is anticipated that the NTPE-PH sensor can be a useful tool for monitoring 1 O2 variation during immune response and pathological processes corresponding to different stimuli, even with drug treatment included.

A novel strategy for markedly enhancing the green upconversion emission in Er3+/Yb3+ co-doped VO2

There is a growing interest in developing upconversion nanocrystals at the forefront of promising applications. However, insufficient energy transfer between lanthanide ions still limited the practical application. In this work, a new class of welded-structure upconversion nanoparticles which emits bright green emission upon 980 nm near-infrared (NIR) laser excitation is presented. Importantly, this unique welded-structure arrangement enables the high-efficient energy transfer between different nanocrystals, leading to 65-folds enhancement for green upconversion emission. A continuous wave 980 nm laser is used to reduce interparticle distance followed by structure welding. The experiment findings show that the controlling distance of nanosheets enables readily manipulation the intensity ration of green and red emission, thereby allowing us to achieve the emission color purity tuning from pea green to bright green. And the green and red ratio achieved 11 folds enhancement, leading to a purer green light emission. The result not only provide an upfront experimental design for constructing welded-nanostructures with efficient energy transfer and color purity tunability, but also suggests a new pathway to build high-efficiency upconversion systems.

Achieving high energy transfer efficiency in Sr6Ca4(PO4)6F2:Ce3+, Mn2+ by regulating the occupation of activator

Series of color tunable Sr6Ca4(PO4)6F2:Ce3+, Mn2+ were achieved. In the way of energy transfer, the activator Mn2+ should get large energy from sensitizer Ce3+ and show high efficiency. However, with increasing Mn2+ concentration the emission intensity of Ce3+ decreases rapidly, the emission intensity of Mn2+ shows unapparent increase. It indicates that there are lots of energy losses in the process of energy transfer from Ce3+ to Mn2+. With the high concentration of Mn2+, the severe concentration quenching effect of Mn2+ occurs in Sr6Ca4(PO4)6F2:Ce3+, Mn2+. In order to reduce the energy loss owing to the concentration quenching effect, Mg2+ ions are introduced into Sr6Ca4(PO4)6F2:Ce3+, Mn2 to regulate the occupation of Mn2+. Consequently, the distance between Mn2+ increases and the energy loss between Mn2+ is effectively reduced. Therefore the emission intensity of Mn2+ increases greatly, and high energy transfer efficiency of Ce3+→Mn2+ is achieved.

A ratiometric fluorescence probe based on a novel recognition mechanism for monitoring endogenous hypochlorite in living cells

A ratiometric fluorescence probe (named ZOC) for the fast detection of HClO/ClO− was constructed by coumarin (donor) and pyridinium (acceptor) based on Forster resonance energy transfer (FRET) and intramolecular charge transfer (ICT) platform. ZOC possessed red emission signal (610 nm), large Stocks shift (190 nm), high energy transfer efficiency (95.3%), high selectivity and sensitivity, low detection limit (25 nM), wider detection range (from 25 nM to 30 μM), rapid response (within 13 S), and good biocompatibility. It was very interesting that the recognition mechanism involved a new organic reaction in which olefin double bond reacted first with HClO/ClO− regioselectively, followed by cyclization. ZOC was successfully used to the real time detection of endogenous HClO/ClO− in RAW 264.7 cells.

Microemulsion-Assisted Self-Assembly and Synthesis of Size-Controlled Porphyrin Nanocrystals with Enhanced Photocatalytic Hydrogen Evolution.

Design and engineering of highly efficient light-harvesting nanomaterial systems to emulate natural photosynthesis for maximizing energy conversion have stimulated extensive efforts. Here we present a new class of photoactive semiconductor nanocrystals that exhibit high-efficiency energy transfer for enhanced photocatalytic hydrogen production under visible light. These nanocrystals are formed through noncovalent self-assembly of In(III) meso-tetraphenylporphine chloride (InTPP) during microemulsion assisted nucleation and growth process. Through kinetic control, a series of uniform nanorods with controlled aspect ratio and high crystallinity have been fabricated. Self-assembly of InTPP porphyrins results in extensive optical coupling and broader coverage of the visible spectrum for efficient light harvesting. As a result, these nanocrystals display excellent photocatalytic hydrogen production and photostability under the visible light in comparison with the commercial InTPP porphyrin powders.

Antenna arrangement and energy transfer pathways of a green algal photosystem-I-LHCI supercomplex.

During oxygenic photosynthesis, photosystems I and II (PSI and PSII) are essential for light-driven electron transport. Excitation energy transfer in PSI occurs extremely quickly, making it an efficient energy converter. In the alga Chlamydomonas reinhardtii (Cr), multiple units of light-harvesting complex I (LHCI) bind to the PSI core and function as peripheral antennae, forming a PSI-LHCI supercomplex. CrPSI-LHCI shows significantly larger antennae compared with plant PSI-LHCI while maintaining highly efficient energy transfer from LHCI to PSI. Here, we report structures of CrPSI-LHCI, solved by cryo-electron microscopy, revealing that up to ten LHCIs are associated with the PSI core. The structures provide detailed information about antenna organization and pigment arrangement within the supercomplexes. Highly populated and closely associated chlorophylls in the antennae explain the high efficiency of light harvesting and excitation energy transfer in CrPSI-LHCI.

Sensitization effect between Ln3+ ions in zinc fluoride glasses for MIR applications

A system of zinc fluoride glasses were synthesized to analyse the sensitization mechanism between doped Ln3+ ions under 808 or 980 nm excitation. Differential scanning calorimetry (DSC) curve and Raman spectra indicate the favourable thermal stability and a low maximum phonon energy of the host. Judd-Ofelt (J-O) theory together with the absorption spectra were utilized to compute the Ωt for predicting radiative features of each sample which coincide with the later measured emission spectra. Broadband emission ranging from 2400 to 3300 nm with a half-width of 361 nm in Er3+/Dy3+ codoped zinc fluoride glasses under 980 nm pumping has been investigated, which may be applicated in mid-infrared fiber amplifier and broadband tunable lasers field. On the other hand, the efficient sensitization effect mechanism between Er3+ and Dy3+ around 3 μm band with an extremely high energy transfer efficiency Ƞ (96.1%) of Er3+:4I13/2→Dy:6H11/2 has been researched under 808 nm excitation. Hence, Er3+ and Dy3+ doped zinc fluoride glasses may be potential optical candidates of great development foreground in the fields of mid-infrared applications.

Synthesis and photoluminescence of double perovskite La2LiSbO6:Ln3+ (Ln= Eu, Tb, Tm, Sm, Ho) phosphors and enhanced luminescence of La2LiSbO6:Eu3+ red phosphor via Bi3+ doping for white light emitting diodes

La2LiSbO6: Ln3+ (Ln = Eu, Ho, Dy, Sm, Tm) and La2LiSbO6: Eu3+, Bi3+ phosphors were synthesized by conventional solid state reaction method. They were characterized by X-ray diffraction patterns, SEM, photoluminescence spectra, diffuse reflectance spectra and temperature-dependent luminescence spectra. Among these doping Ln3+ ions, Eu3+ was found to be most suitable for La2LiSbO6 host because of the relatively high energy transfer efficiency from host La2LiSbO6 and the high quenching concentration. By co-doping Bi3+ ions, the fluorescent intensity of La2LiSbO6:Eu3+ could be further significantly increased. The energy transfer efficiency and the energy transfer mechanism in La2LiSbO6: Ln3+and La2LiSbO6:Eu3+, Bi3+ were procured. The good thermal stability of the composition optimized La1.63Bi0.01Eu0.36LiSbO6 phosphor was also illustrated by the temperature-dependent luminescence spectra. These merits demonstrated this material could be a potential candidate as the red light component in the field of phosphor – converted LEDs.

Gold nanostructures for the sensing of pH using a smartphone.

Recently, metal nanostructures have been found to be capable of recognizing small changes in their surrounding environment, which can be utilized as significant sensing tools. In this study, we demonstrated colorimetric sensing of pH by gold nanostructures (GNs) using a simple smartphone. An indigenously developed Android app based on the CIELab 1931 analysis, which could run in a smartphone, was used for the precise determination of the pH value of liquid media. The pH value of an unknown solution obtained from the developed Android app was also compared with that obtained from the conventional ratiometric technique and a commercial pH meter. In another endeavor, it was found that the synthesized GNs demonstrated a high energy transfer efficiency from a donor (namely, the rhodamine 6G, (Rh 6G)) dye. This property of the GNs can be utilized further in the future for studying different bimolecular activities within the human body. It was found that the photoluminescence (PL) of Rh 6G was quenched when it was kept in the vicinity of the synthesized GNs, which was explained in terms of the Förster energy transfer mechanism. Thus, the present study will open up a plethora of opportunities for researchers to employ the nanostructures of gold and other metals in developing low-cost and Internet of Things (IoT)-based sensing devices using only a smart phone.

Realizing Bright Blue-Red Color-Tunable Emissions from Gd <sub>2</sub>GeO <sub>5</sub>:Bi <sup>3+</sup>Eu3+ Phosphors Through Energy Transfer Toward Light-Emitting Diodes

Novel Bi3+/Eu3+ ions co-doped Gd2GeO5 (GGO) phosphors were prepared by a high-temperature solid-state reaction method. X-ray diffraction, photoluminescence, and CIE chromaticity coordinates were applied to analyze the as-obtained phosphors. The as-prepared GGO:Bi3+,Eu3+ phosphors showed color-tunable emissions from blue (Bi3+) to red (Eu3+) with increasing the Eu3+ doping concentration via a high-efficiency energy transfer process. Moreover, the mechanism of energy transfer from Bi3+ to Eu3+ ions was the dipole-quadrupole interaction. All these meaningful results demonstrated that blue-red color-tunable GGO:Bi3+,Eu3+ phosphors have potential applications in white light-emitting diodes (LEDs) and plant growth LEDs.

3D GaN-based betavoltaic device design with high energy transfer efficiency

A combined GaN 3D core-shell and planar pin structure is being developed and demonstrated to achieve the highest potential to increase energy transfer efficiency from the source (ηsrc) and power generated per cm2 (PGaN/cm2) in a betavoltaic (BV) device configuration. Physics-based Sentaurus TCAD and Monte Carlo N-Particle extended (MCNPX) software are employed to obtain the maximum ηsrc and PGaN/cm2 by a parametric study of device dimensions coupled with a 63NiCl2 source. Idealized structure dimensions are determined to be 2 µm wide, 4 µm tall GaN pin core-shell mesas, with 63Ni source conformally surrounding the structure with a 2 µm gap for maximum efficiency of energy transfer. For maximizing power deposited (10 µm mesa separation) a 3.75x increase in PGaN/cm2 at approximately half the activity density compared to a planar device is achieved for 4 µm mesa height, with 5.82x improvement in ηsrc.