Utilizing Energy Transfer Research Articles

Photocatalytic Unsymmetrical Diamination of Styrenes, Indoles, and Benzofurans Facilitated by Benzotriazolyl and Iminyl Radicals.

Utilizing energy transfer catalysis, this research employed the bifunctional reagents benzotriazole carboxylic acid oxime esters to simultaneously generate benzotriazole and imine radicals. The synthesis of two distinct C-N bonds in a single conversion is showcased through radical addition and radical-radical cross-coupling processes between benzotriazole carboxylic acid oxime ester and olefins. This process facilitates the intermolecular two-component unsymmetrical diamination reaction of olefins. Using this approach, more than 40 benzotriazole-containing molecules were successfully synthesized using styrene, indole, and benzofuran as acceptors, with yields ranging from moderate to excellent.

Device parameter to evaluate exciton energy transfer in organic whispering-gallery-mode microresonators and its dependence on the amplified spontaneous emission threshold.

Exciton energy transfer in organic whispering-gallery-mode (WGM) resonators and its effect on the amplified spontaneous emission (ASE) threshold have been investigated using the stilbene-based energy donor 4,4'-bis[(N-carbazole)styryl]biphenyl (BSB-Cz) and the coumarin-based energy acceptor 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5H,11H-10-(2-benzothiazolyl)quinolizino[9,9a,1gh]coumarin (C545T). Using the stacked-layer structure of BSB-Cz/C545T/BSB-Cz, we fabricated bowl-shaped microresonators on silica microspheres with a total thickness of 250 nm fixing the thickness of the C545T layer to 1 nm. The ASE threshold depended on the thicknesses of the top and bottom BSB-Cz layers, which affect the magnitude of the energy transfer. To assess the relationship between the ASE threshold and energy transfer, we developed a device parameter to evaluate the magnitude of the energy transfer by formulating the rate equations. We found that ASE easily occurs under the condition that the C545T molecules become unable to accept energy from the BSB-Cz excitons owing to the high exciton density of C545T, and that the ASE threshold decreases with decreasing device parameter. The device parameter is useful for optimizing microresonator structures in multi-component organic WGM resonators that utilize energy transfer.

(Invited) Organic Polymer Dots for Photocatalysis

Organic polymeric photocatalysts have been attracted scientists’ interests during past years due to their low-cost, tunable bandgaps and energy levels, and promising photocatalytic performance. Making the traditional hydrophobic polymeric photocatalyst into nano-particles with size less than 100 nm, so-called polymer dots (Pdots), has shown significantly enhanced photocatalytic activity. Rational design of organic polymers is one of strategies to improve photocatalytic performance for hydrogen production. Moreover, making heterojunction Pdots can efficiently separate photogenerated charges within Pdots as well as utilize energy transfer process to enhance the light harvesting efficiency. In this talk, I will discuss our research achievements in optimization of polymer structures on Pdots photocatalysis, study of photocatalytic mechanism in heterojunction Pdots systems and applications of Pdots in bio-hybrid photocatalytic systems.Relevant publications:[1] Wang L., et al., Angew. Chem., 2016, 128 (40), 12494-12498[2] Pati P., et al., Energy Environ. Sci., 2017 10 (6), 1372-1376[3] Liu A., et al., J. Am. Chem. Soc., 2021, 143 (7), 2875-2885[4] Pavliuk M., et al., J. Am. Chem. Soc. 2022, 144(30) 13600–13611[5] Wang S., et al., Angew. Chem. Int. Ed., 2022, 61(23), e202202733

Optical Thermometer Based on Efficient Near‐Infrared Dual‐Emission of Cr3+ and Ni2+ in Magnetoplumbite Structure

AbstractRecently, an optical thermometer based on the dual‐emitting fluorescent intensity ratio (FIR) in the visible light (VIS) region has achieved great development. However, there is very little progress in thermometers from NIR light. In this work, a novel optical thermometer based on highly efficient NIR dual‐emission of Cr3+ and Ni2+ in LaZnGa11O19 (LZG) with a magnetoplumbite structure is designed. Utilizing energy transfer from Cr3+ to Ni2+, the dual‐emission shows a wide coverage in the 650–1600 nm region, covering the NIR I and II windows, respectively. The as‐reported LZG:0.3Cr3+ and LZG:0.3Cr3+,0.01Ni2+ phosphors can reach internal/external quantum efficiency (IQE/EQE) of 94%/64% and 77%/53%, respectively. The electroluminescence property and potential applications in spectroscopic analysis, night‐vision, and bioimaging of fabricated NIR‐LED with LZG:0.3Cr3+,0.01Ni2+ have also been investigated. In addition, the designed ratiometric optical thermometer responds to wide temperature ranges (100‐175 K, 200–475 K) and shows a maximum relative sensitivity value (Sr) of 2.4% K−1 at 475 K. The optical performance of absorption in the red region and emission in the NIR region enables the LZG:0.3Cr3+,0.01Ni2+ to become a candidate for NIR optical thermometers in biotechnological applications.

Utilizing Energy Transfer in Mn2+/Ho3+/Yb3+ Tri-doped ZnAl2O4 Nanophosphors for Tunable Luminescence and Highly Sensitive Visual Cryogenic Thermometry.

Lanthanide (Ln3+)-doped upconversion (UC) phosphors converting near-infrared (NIR) light to visible light hold very high promise toward biomedical applications. The scientific findings on luminescent thermometers revealed their superiority for noninvasive thermal sensing. However, only few reports showcase their potential for applications in extreme conditions (temperatures below -70 °C) restricted by low thermal sensitivity. Here, we demonstrate the tailoring of luminescence properties via introducing Ho3+-Mn2+ energy transfer (ET) routes with judicious codoping of Mn2+ ions in ZnAl2O4/Ho3+,Yb3+ phosphor. Preferentially, a singular red UC emission is required to improve the bioimaging sensitivity and minimize tissue damage. We could attain UC emission with 94% red component by a two-photon UC process. Higher temperature annealing brings the color coordinates to the green domain, highlighting the potential for color-tunable luminescence switch. Moreover, this work investigates the thermometric properties of ZnAl2O4/Yb3+, Ho3+ in the range of 80-300 K and influence of inducing extra ET pathways by Mn2+ codoping. Interestingly, the luminescence intensities for nonthermally coupled (5F4,5S2) and the 5F5 radiative transitions of Ho3+ ions display opposite behavior at 80 and 300 K, which revealed competition between temperature-sensitive decay pathways. The codoping of Mn2+ ions is fruitful in causing a fourfold increase of absolute sensitivity. Notably, the color tunability from green through yellow to red is helpful in rough temperature estimation by naked eyes. The maximum relative (Sr) and absolute sensitivities (Sa) were estimated to be 1.89% K-1 (140 K) and 0.0734 K-1 (300 K), respectively. Even at 80 K, a Sa of 0.00447 K-1 and Sr of 0.6025% K-1 were achievable in our case, which are higher than most of the other Ln3+-based systems. The above-mentioned results demonstrate the potential of ZnAl2O4/Yb3+,Ho3+ for cryogenic optical thermometry and a strategy to design new Ln3+-based UC thermometers by taking advantage of ET routes.

Greenhouse heating by energy transfer between greenhouses: System design and implementation

Multi-span greenhouses consume enormous amounts of energy for heating in northern China, resulting in poor profitability and unsustainability. A greenhouse heating system, utilizing energy transfer between greenhouses based on a dual source heat pump, was designed to remedy this issue. The system collects surplus air heat inside Chinese solar greenhouses (CSGs) for heating multi-span greenhouses. Through enabling a greenhouse energy transfer in time and space, improved utilization efficiency of surplus air heat in CSGs is achievable, resulting in an overall reduction of heating costs. This study defines the heating approach and describes the overall system design. The dual source heat pump acts as the core component, with two separate evaporators placed in the CSG and ambient air. Calculations for system sizing are then presented, including a heating load model of multi-span greenhouses, a surplus air heat model of CSGs, the selection of required equipment (dual source heat pump, heat storage tank, and surface air cooler of the combined air conditioning unit), and the area matching. Finally, a case study illustrates the implementation processes of the heating system. The available CSG surplus air heat ranged 100.8–112.6 W m−2 for system sizing, and the minimum area of CSGs was suggested to be twice the multi-span greenhouse area. The pilot test showed that the running status and heating effect of the system was stable. The coefficient of performance (COP) of the heat pump reached 4.3–4.8 when using CSG surplus air heat as the heat source, performing 23–26 % higher than when using ambient air over the same periods. Throughout the entire course of heat collection, dual source heat pumps, switching sources based on their setting, achieved a total COP of 3.4–4.2, increased by 6–11 % compared with air source heat pumps. This study provides a novel heating approach and an energy-saving system for multi-span greenhouses.

Luminescent solar concentrator utilizing energy transfer paired aggregation‐induced emissive fluorophores

Luminescent solar concentrator utilizing energy transfer paired aggregation‐induced emissive fluorophores

Utilizing energy transfer strategy to produce efficient green luminescence in Ca2LuHf2Al3O12:Ce3+,Tb3+ garnet phosphors for high-quality near-UV-pumped warm-white LEDs

White light-emitting diodes (LEDs) are widely used in lighting and display devices, and the exploration of phosphors with excellent luminescence performance and good stability is the key to the development of white LEDs. In this work, we reported novel near-UV-excited green-emitting Ca2LuHf2(AlO4)3:Ce3+,Tb3+ garnet phosphors with efficient Ce3+ → Tb3+ energy transfer. The CLHA:Ce3+,Tb3+ green phosphors were successfully synthesized by a high-temperature solid-state method, and the phosphors were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, photoluminescence excitation and photoluminescence spectra, the Commission International de I’Eclairage (CIE) chromaticity coordinates, quantum efficiency and temperature-dependent emission spectra. Due to the spin-allowed 4f → 5d transition of Ce3+ ions, the CLHA:Ce3+,Tb3+ phosphors exhibited a strong broad excitation band in the 300–470 nm near-ultraviolet (near-UV) range. Under 408 nm excitation, the CLHA:Ce3+,Tb3+ phosphors showed strong green light with emission center at 543 nm. The mechanism of energy transfer from Ce3+ to Tb3+ ions was attributed to quadruple-quadruple interaction. Impressively, the internal quantum efficiency and external quantum efficiency of the optimal CLHA:0.02Ce3+,0.5Tb3+ green phosphors were measured to be 77.1% and 55.8%, respectively. Finally, using the CLHA:0.02Ce3+,0.5Tb3+ phosphors as green-emitting color converter, a near-UV-pumped white LED device was fabricated, and under 80 mA driving current the LED device demonstrated bright warm-white light with high color rendering index (93.7), low correlated color temperature (3574 K), CIE chromaticity coordinates (0.3922, 0.3633), and high luminous efficacy (29.35 lm/W).

Discrimination and Detection of Oxygenated Volatile Organic Compounds Utilizing Energy Transfer Cataluminescence of La2O2CO3:Eu3+

The discrimination and detection of oxygenated volatile organic compounds (OVOCs) is one of the most serious subjects in chemical sensing because OVOCs as a class of substances in volatile organic compounds (VOCs) are far more reactive than alkanes in the atmosphere. Herein, a novel ratio method based on cataluminescence (CTL) intensity on the surface of La2O2CO3 (I460) and La2O2CO3:Eu3+ (I620) was reported and used for simultaneous discrimination and detection of OVOCs within different concentrations. To confirm the feasibility of the proposed method, six kinds of common OVOCs, including isomers and similar substances were selected as representatives. Results show that the CTL intensity ratios (R620/460) at 620 nm and 460 nm were distinctive and notable (from 3.55 to 72.7), and the limits of detection (LOD) could be as low as 17.29 ng/mL (propanol). In addition, the principle of discrimination and detection was discussed briefly and the factors for energy transfer were preliminarily discussed to help explore energy transfer process between gas and solid interfaces.

Highly efficient yellow nondoped thermally activated delayed fluorescence OLEDs by utilizing energy transfer between dual conformations based on phenothiazine derivatives

The nondoped thermally activated delayed fluorescence (TADF) devices are increasingly attracting attention due to the superior performances and simple fabrication process. By incorporating two acceptors with phenothiazine, two materials 2-(10H-phenothiazine-10-yl)-10-phenyl-10H-phenothiazine-5,5-dioxide (PTZ-2PTO) and 3-(10H-phenothiazin-10-yl)-10-phenylacridin-9(10H)-one (PTZ-AD) are designed and investigated. Both the two materials possess dual conformations, whereas the quasi-axial conformer is the main configuration of PTZ-2PTO and quasi-equatorial conformer of PTZ-AD is more stable. The quasi-axial conformers show classical fluorescence emission, and the quasi-equatorial conformers exhibit TADF characteristic. Fascinatingly more, efficient energy transfer can be achieved between quasi-axial conformers and quasi-equatorial conformers, exhibiting similar mechanism to the traditional host-guest system. Based on this characteristic, yellow nondoped TADF-OLED device of PTZ-AD has realized the efficiency of up to 17.08%, 50.48 cd A−1 and 60.04 lm W−1. Meanwhile, the PTZ-AD based nondoped device exhibits low turn-on voltage and low efficiency roll-off, which is among the best performance for yellow nondoped TADF devices. In addition, PTZ-AD based doped device realizes high efficiency of 20.23%, 61.04 cd A−1 and 68.45 lm W−1. This dual conformations forming host-guest system provides a new strategy for obtaining highly efficient nondoped OLEDs devices.

Efficient white-light-emission from a heterometallo-supramolecular polymer with Eu(III) and Zn(II) ions introduced alternately

By utilizing energy transfer from ligands to metal ions, efficient white-light-emission (ΦPL: 0.54, x = 0.31, y = 0.33) was realized in a heterometallo-supramolecular polymer with Eu(III) and Zn(II) ions introduced alternately. The polymer showed strong white-light-emission even in the film state as well as in solution.

Simultaneous luminescence in Ⅰ, Ⅱ and III biological windows realized by using the energy transfer of Yb3+ → Er3+/Ho3+ → Cr3+

Until now, the emissions of most biological phosphors were located at a single biological window. By utilizing energy transfer of Yb3+ → Ln3+ → Cr3+, we have successfully developed a phosphor emitting in the first, second and third biological windows simultaneously. The luminescences have good thermal stability because of forming the thermal cycle among Ho3+ and Cr3+. And temperature measurement can be realized in NIR-3.

Remarkable enhancement of the photocatalytic activity of ZnO nanorod array by utilizing energy transfer between Eosin Y and Rose Bengal for visible light-driven hydrogen evolution

In this work, we suggested that an efficient ZnO-based photocatalyst can be prepared utilizing energy transfer among organic dyes for visible light-driven hydrogen evolution. Followed this idea, a photocatalytic system containing Eosin Y, Rose Bengal, ZnO nanorod array and Pt was fabricated. Meanwhile, photocatalytic H2 evolution over the as-prepared photocatalytic system was explored. The results indicate that the visible photocatalytic activity of ZnO nanorod array can be obviously enhanced utilizing the energy transfer between Eosin Y and Rose Bengal. This photocatalytic system possesses high activity for visible light-driven H2 evolution. A rate of H2 evolution of approximate 0.52 L m−2 h−1 was achieved under optimal condition, which is 130% and 58% higher than those of the photocatalytic systems containing individual dye, respectively. The present results may reveal a new strategy for preparation of efficient visible photocatalyst.

High-efficiency and color-stable warm white organic light-emitting diodes utilizing energy transfer from interface exciplex

Abstract We demonstrate high-efficiency warm white organic light-emitting diodes (WOLEDs) with an interface-exciplex-forming structure of hole-transporting 1,3-Bis(carbazol-9-yl)benzene (mCP) as electron-donor and electron-transporting 4,6-Bis(3,5-di(pyridin-3-yl)phenyl)-2-(pyridin-3-yl)pyrimidine (B3PyMPM) as electron-acceptor. The exciplex can be formed effectively at the interface of mCP/B3PyMPM due to the excellent charge-transporting properties of mCP and B3PyMPM and the large energy-levels offset of mCP/B3PyMPM interface, and then its energy transfers to the low-lying triplet states of the blue TADF fluorophors or yellow phosphors. As a result, a maximum power efficiency (PE) of 79.2 lm/W and maximum external quantum efficiency (EQE) of 22.3% were achieved from the warm WOLED. The key factor for such high efficiency WOLED is believed to be from the effective harvest of triplet excitons of the interface-exciplex via reverse intersystem crossing process (RISC).

Two-photon actuation of crosslinked liquid-crystalline polymers utilizing energy transfer system

ABSTRACTWe prepared crosslinked azotolane liquid-crystalline polymer (LCP) films doped with a stilbene derivative (two-photon chromophore) utilizing an interpenetrating polymer network (IPN) structure. The IPN films bend toward the light source upon irradiation with femtosecond laser pulses at 600 nm, which can excite the stilbene derivative by two-photon absorption. The bending speed of the IPN films increases with the square of the laser pulse intensity, which is compelling evidence for the two-photon processes.

Utilizing Energy Transfer in Binary and Ternary Bulk Heterojunction Organic Solar Cells.

Energy transfer has been identified as an important process in ternary organic solar cells. Here, we develop kinetic Monte Carlo (KMC) models to assess the impact of energy transfer in ternary and binary bulk heterojunction systems. We used fluorescence and absorption spectroscopy to determine the energy disorder and Förster radii for poly(3-hexylthiophene-2,5-diyl), [6,6]-phenyl-C61-butyric acid methyl ester, 4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine (DIBSq), and poly(2,5-thiophene-alt-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3',2'-h][1,5]naphthyridine-5,10-dione). Heterogeneous energy transfer is found to be crucial in the exciton dissociation process of both binary and ternary organic semiconductor systems. Circumstances favoring energy transfer across interfaces allow relaxation of the electronic energy level requirements, meaning that a cascade structure is not required for efficient ternary organic solar cells. We explain how energy transfer can be exploited to eliminate additional energy losses in ternary bulk heterojunction solar cells, thus increasing their open-circuit voltage without loss in short-circuit current. In particular, we show that it is important that the DIBSq is located at the electron donor-acceptor interface; otherwise charge carriers will be trapped in the DIBSq domain or excitons in the DIBSq domains will not be able to dissociate efficiently at an interface. KMC modeling shows that only small amounts of DIBSq (<5% by weight) are needed to achieve substantial performance improvements due to long-range energy transfer.

Synthesis and tunable blue–green color emission and energy transfer of Ce3+, Tb3+ co-doped BaZrSi3O9 phosphors

Utilizing energy transfer process, Ce3+, Tb3+ co-doped BaZrSi3O9 (BZS) phosphors have been successfully prepared via solid state reaction process. The phase structure, photoluminescence properties, decay curves, thermal stability, and the energy transfer mechanism were investigated in this paper. The critical distance calculated by quenching concentration method was 8.84 A, and the energy transfer process from Ce3+ to Tb3+ in BZS:Ce3+/Tb3+ phosphors had been demonstrated to be a resonant type via a dipole–quadrupole mechanism. The emission colors of the phosphors could be tuned from blue (0.1625, 0.1261) to green (0.2979, 0.5473) through the corresponding Ce3+ to Tb3+ energy transfer. Moreover, thermal quenching luminescence results revealed that BZS:Ce3+, Tb3+ exhibited good thermal stability. The Tb3+ intensity of BZS:0.04Ce3+, 0.02Tb3+ sample showed about 60.88 % of its initial emission intensity at room temperature. The above results indicate that the phosphors may be potentially used as single-component blue–green emission phosphors for application in light emitting device.

Highly efficient orange fluorescent OLEDs based on the energy transfer from bilayer interface exciplex

We demonstrated highly efficient traditional orange emission fluorescent OLEDs with simple device structure by utilizing energy transfer from bilayer interface TADF exciplex to dopant. With rubrene as the dopant, under the optimized concentration of 1.5%, the device achieved maximum current efficiency, power efficiency and EQE of 25.3 cd/A, 22.6 lm/W and 8.1%, respectively. Even at the luminance of 1000 cd/m2, the EQE also remained 6.9%. The obtainment of so high efficiency could be attributed to highly efficient RISC efficiency of triplet excitons and energy transfer efficiency from TADF exciplex to dopant. The more detailed working mechanism was also argued.

Emission mechanism in phosphorescent and fluorescent OLED utilizing energy transfer from exciplex to emitter

This paper discusses the effectiveness of energy transfer from an exciplex to an emitter in both phosphorescent and fluorescent organic light‐emitting diodes. This energy transfer enhances the efficiency, lowers the drive voltage, and extends the lifetime. The increase in the quantum efficiency of a fluorescent organic light‐emitting diode using this mechanism is also analyzed.

40.2: Efficiency Enhancement in Phosphorescent and Fluorescent OLEDs Utilizing Energy Transfer From Exciplex to Emitter

This paper discusses the effectiveness of energy transfer from an exciplex to an emitter in both phosphorescent and fluorescent OLEDs. This energy transfer enhances the efficiency, lowers the drive voltage, and extends the lifetime. The increase in the quantum efficiency of a fluorescent OLED using this mechanism is also analyzed.