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1.
Three NIR‐emitting neutral IrIII complexes [Ir(iqbt)2(dpm)] ( 1 ), [Ir(iqbt)2(tta)] ( 2 ), and [Ir(iqbt)2(dtdk)] ( 3 ) based on the 1‐(benzo[b]thiophen‐2‐yl)‐isoquinolinate (iqtb) were synthesized and characterized (dpm=2,2,6,6‐tetramethyl‐3,5‐heptanedionate; tta=2‐thienoyltrifluoroacetonate; dtdk=1,3‐di(thiophen‐2‐yl)propane‐1,3‐dionate). The compounds emit between λ=680 and 850 nm with high luminescence quantum yields (up to 16 %). By combining electrochemistry, photophysical measurements, and computational modelling, the relationship between the structure, energy levels, and properties were investigated. NIR‐emitting, solution‐processed phosphorescent organic light‐emitting devices (PHOLEDs) were fabricated using the complexes. The devices show remarkable external quantum efficiencies (above 3 % with 1 ) with negligible efficiency roll‐off values, exceeding the highest reported values for solution‐processible NIR emitters.  相似文献   

2.
Full control on the valence of the active ions in solids to improve properties is the central topic of chemistry and materials. Cr3+ and Cr4+ ions generally emit wavelength-different near-infrared (NIR) light. Here, we have developed a chromium valence-controllable single-phase phosphor, Mg2GeO4:Cr3+,Cr4+ to achieve super-broad NIR luminescence. High Li + content charge compensators can stabilize Cr3+, whereas high-temperature sintering tends to facilitate the formation of Cr4+. Through fine adjusting the synthesis conditions, pure Cr3+ or Cr4+ luminescence can be obtained with peak emission locating at 935 nm and 1190 nm, respectively. Super broad band dual emission spanning from 650 nm to 1600 nm is realized via fully controlling the concentration ratio of Cr3+ to Cr4+ in a single host. By measuring the transmission spectra of several foodstuff illuminated by our phosphors, non-destructive analysis in food safety areas can be realized. This study provides a new strategy for exploiting super broad band NIR luminescent materials.  相似文献   

3.
Ultra‐small ZnGa2O4:Cr3+ nanoparticles (6 nm) that exhibit near‐infrared (NIR) persistent luminescence properties are synthesized by using a non‐aqueous sol–gel method assisted by microwave irradiation. The nanoparticles are pegylated, leading to highly stable dispersions under physiological conditions. Preliminary in vivo studies show the high potential for these ultra‐small ZnGa2O4:Cr3+ nanoparticles to be used as in vivo optical nanotools as they emit without the need for in situ excitation and, thus, avoid the autofluorescence of tissues.  相似文献   

4.
Lanthanide (Ln3+)‐doped luminescent nanoparticles (NPs) with emission in the second near‐infrared (NIR‐II) biological window have shown great promise but their applications are currently limited by the low absorption efficiency of Ln3+ owing to the parity‐forbidden 4f→4f electronic transition. Herein, we developed a strategy for the controlled synthesis of a new class of NIR‐II luminescent nanoprobes based on Ce3+/Er3+ and Ce3+/Nd3+ co‐doped CaS NPs, which can be effectively excited by using a low‐cost blue light‐emitting diode chip. Through sensitization by the allowed 4f→5d transition of Ce3+, intense NIR‐II luminescence from Er3+ and Nd3+ with quantum yields of 9.3 % and 7.7 % was achieved, respectively. By coating them with a layer of amphiphilic phospholipids, these NPs exhibit excellent stability in water and can be exploited as sensitive NIR‐II luminescent nanoprobes for the accurate detection of an important disease biomarker, xanthine, with a detection limit of 32.0 nm .  相似文献   

5.
Despite the success of thermally activated delayed fluorescent (TADF) materials in steering the next generation of organic light‐emitting diodes (OLEDs), effective near infrared (NIR) TADF emitters are still very rare. Here, we present a simple and extremely high electron‐deficient compound, 5,6‐dicyano[2,1,3]benzothiadiazole (CNBz), as a strong electron‐accepting unit to develop a sufficiently strong donor‐acceptor (D?A) interaction for NIR emission. End‐capping with the electron‐donating triphenylamine (TPA) unit created an effective D?A?D type system, giving rise to an efficient NIR TADF emissive molecule (λem=750 nm) with a very small ΔEST of 0.06 eV. The electroluminescent device using this NIR TADF emitter exhibited an excellent performance with a high maximum radiance of 10020 mW Sr?1 m?2, a maximum EQE of 6.57% and a peak wavelength of 712 nm.  相似文献   

6.
Carbazole and fluorene‐based random and alternating copolycondensates were synthesized to develop high‐performance blue light‐emitting polymers by improving electron injection ability of poly(N‐aryl‐2,7‐carbazole)s that showed intense blue electroluminescence (EL) with good hole‐injection and ‐transport ability. These copolycondensates absorbed light energy at about λmax = 390 nm in CHCl3 and 400 nm in film state, and fluoresced at about λmax = 417 nm in CHCl3 and 430 nm in the thin film state. Energy gaps between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of them were about 2.9 eV, and the energy levels of LUMO situated lower than that of corresponding polycarbazole. Polymer light‐emitting diode devices having configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate)/polymer/CsF/Al using the copolycondensates, poly(N‐arylcarbazole‐2,7‐diyl), and poly(9,9‐dialkylfluorene‐2,7‐diyl), emitted bluish EL at operating voltages lower than 7 V. The device embedded the random copolycondensate showed notably higher performance with maximum luminance of 31,200 cd m?2 at 11.0 V, and the current efficiencies observed under operating voltages lower than 7 V were higher than those of the other devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

7.
《印度化学会志》2023,100(9):101071
Rare earth (RE) activated nanophosphors are the prime elements employed to manufacture light emitting diodes (LEDs) for the current solid state lighting (SSL) industry. The apparent lack of reddish orange emitting nanophosphors is proving to a constraint in the commercialization of the white light emitting diodes (WLEDs). Herein, the size of BaTiO3 (BTO): Sm3+ and K+ co-activated BTO: Sm3+ nanophosphor, with an average particle size of 80 nm, have been produced by a modified sol gel technique. The synthesized nanophosphors emit a brilliant reddish-orange light when excited at 406 nm. The relative photoluminescence (PL) studies of Sm3+ doped BTO and Sm3+ doped BTO with K+ nanophosphor show that adding K+ doubles the intensity of the emitted light and improves the thermal stability in a significant way. The results of the research indicated that using the aforementioned nanophosphor in the future may be advantageous for solid-state lighting systems, including warm LEDs with cyan light chips.  相似文献   

8.
New deep‐red light‐emitting phosphorescent dendrimers with hole‐transporting carbazole dendrons were synthesized by reacting tris(2‐benzo[b]thiophen‐2‐yl‐pyridyl) iridium (III) complex with carbazolyl dendrons by DCC‐catalyzed esterification. The resulting first‐, second‐, and third‐generation dendrimers were found to be highly efficient as solution‐processable emitting materials and for use in host‐free electrophosphorescent light‐emitting diodes. We fabricated a host‐free dendrimer EL device with configuration ITO/PEDOT:PSS (40 nm)/dendrimer (55 nm)/BCP (10 nm)/Alq3 (40 nm)/LiF (1 nm)/Al (100 nm) and characterized the device performance. The multilayered devices showed luminance of 561 cd/m2 at 383.4 mA/cm2 (12 V) for 15 , 1302 cd/m2 at 321.3 mA/cm2 (14 V) for 16 , and 422 cd/m2 at 94.4 mA/cm2 (18 V) for 17 . The third‐generation dendrimer, 17 (ηext = 6.12% at 7.5 V), showed the highest external quantum efficiency (EQE) with an increase in the density of the light‐harvesting carbazole dendron. Three dendrimers exhibited considerably pure deep‐red emission with CIE 1931 (Commission International de L'Eclairage) chromaticity coordinates of x = 0.70, y = 0.30. The CIE coordinates remained very stable with the current density. The integration of rigid hole‐transporting dendrons and phosphorescent complexes provides a new route to design highly efficient solution‐processable materials for dendrimer light‐emitting diode (DLED) applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7517–7533, 2008  相似文献   

9.
Establishing an effective design principle in solid‐state materials for a blue‐light‐excited Eu2+‐doped red‐emitting oxide‐based phosphors remains one of the significant challenges for white light‐emitting diodes (WLEDs). Selective occupation of Eu2+ in inorganic polyhedra with small coordination numbers results in broad‐band red emission as a result of enhanced crystal‐field splitting of 5d levels. Rb3YSi2O7:Eu exhibits a broad emission band at λmax=622 nm under 450 nm excitation, and structural analysis and DFT calculations support the concept that Eu2+ ions preferably occupy RbO6 and YO6 polyhedra and show the characteristic red emission band of Eu2+. The excellent thermal quenching resistance, high color‐rendering index Ra (93), and low CCT (4013 K) of the WLEDs clearly demonstrate that site engineering of rare‐earth phosphors is an effective strategy to target tailored optical performance.  相似文献   

10.
In this paper, the electroluminescent properties of a new partially‐conjugated hyperbranched poly (p‐phenylene vinylene) (HPPV) were studied. The single layer light‐emitting device with HPPV as the emitting layer emits blue‐green light at 496 nm, with a luminance of 160 cd/m2 at 9 V, a turn‐on voltage of 4.3 V and an electroluminescent efficiency of 0.028 cd/A. By doping an electron‐transport material [2‐(4‐biphenylyl)‐5‐phenyl‐1,3,4‐oxadiazole, PBD] into the emitting layer and inserting a thin layer of tris(8‐hydroxy‐quinoline)aluminum (Alq3) as electron transporting/hole blocking layer for the devices, the electroluminescent efficiency of 1.42 cd/A and luminance of 1700 cd/m2 were achieved. The results demonstrate that the devices with the hyperbranched polymers as emitting material can achieve high efficiency through optimization of device structures. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

11.
A phosphor emitting both white light and broad near-infrared (NIR) radiation can simultaneously provide visual inspection and early signs of rotting of food products. The broad NIR emission is absorbed by the vibrational overtones of water molecules present in food items, providing the non-invasive image contrast to assess the food freshness. Here we design a phosphor, namely, Cr3+-Bi3+-codoped Cs2Ag0.6Na0.4InCl6, that simultaneously emit warm white light and broad NIR (1000 nm) radiation with quantum yield 27 %. This dual emitter is designed by combining the features of s2-electron (Bi3+) and d3-electron (Cr3+) doping in a weak crystal field of the halide perovskite host. excitation of Bi3+, using a commercial 370 nm ultraviolet light-emitting-diodes (UV-LED), yields both the emissions. A fraction of the excited Bi3+ dopants emit the warm white light, and the other fraction transfers its energy non-radiatively to Cr3+. Then the Cr3+ de-excites emitting broad NIR emission. Temperature dependent (6.4–300 K) photoluminescence in combination with Tanabe-Sugano diagram show that the Cr3+ experiences a weak crystal field ( =2.2), yielding the NIR emission. As a proof of concept, we fabricated a panel containing 122 phosphor-converted LEDs, demonstrating its capability to inspect food products.  相似文献   

12.
Chromium is a very important analyte for environmental monitoring, and developing biosensors for chromium is a long‐standing analytical challenge. In this work, in vitro selection of RNA‐cleaving DNAzymes was carried out in the presence of Cr3+. The most active DNAzyme turned out to be the previously reported lanthanide‐dependent Ce13d DNAzyme. Although the Ce13d activity was about 150‐fold lower with Cr3+ than that with lanthanides, the activity of lanthanides and other competing metals was masked by using a phosphate buffer; this left Cr3+ as the only metal that could activate Ce13d. With 100 μm Cr3+, the cleavage rate is 1.6 h?1 at pH 6. By using a molecular beacon design, Cr3+ was measured with a detection limit of 70 nm , which was significantly lower than the United States Environmental Protection Agency (EPA) limit (11 μm ). Cr4+ was measured after reduction by NaBH4 to Cr3+, and it could be sensed with a similar detection limit of 140 nm Cr4+; this value was lower than the EPA limit of 300 nm . This sensor was tested for chromium speciation analysis in a real sample, and the results supported its application for environmental monitoring. At the same time, it has enhanced our understanding of the interactions between chromium and DNA.  相似文献   

13.
A series of blue light‐emitting hyperbranched polymers comprising poly(fluorene‐co‐dibenzothiophene‐S,S‐dioxide) as the branch and benzene, triphenylamine, or triphenyltriazine as the core were synthesized by an “A2 + A2' + B3” approach of Suzuki polymerization, respectively. All resulted copolymers exhibited quite comparable thermal properties with the glass transition temperatures in the range of 59–68 °C and relatively high decomposition temperatures over 420 °C. Photoluminescent spectra exhibited slight variation with the molar ratio of the dibenzothiophene‐S,S‐dioxide unit and the size of the core units. Polymer light‐emitting devices demonstrated blue emission with excellent stability of electroluminescence. Copolymers based on smaller core units of benzene and triphenylamine exhibited enhanced device performances regarding to that of triphenyltriazine. With the device configuration of ITO/PEDOT:PSS/polymer/CsF/Al, a maximum luminous efficiency of 4.5 cd A?1 was obtained with Commission Internationale de L'.Eclairage (CIE) coordinates of (0.16, 0.19) for the copolymer PFSO15B. These results indicated that hyperbranched structure can be a promising strategy to attain spectrally stable blue‐light‐emitting polymers with high efficiency. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1043–1051  相似文献   

14.
Production of hybrid organic/inorganic complexes such as lanthanide phosphors in the nanodomain for human fingerprint visualization and anti‐counterfeiting ink under biocompatible UVA and blue light has not yet been studied that thoroughly. This paper presents the preparation of novel, bifunctional, green and red nanophosphors based on Eu3+ and Tb3+ complexes with quinolinone ligand (H2L). They have been prepared and characterized for latent fingerprint detection and anti‐counterfeiting ink applications. The analytical data confirm that the ligand acts in a monoanionic bidentate manner through OO donor sites, forming mononuclear complexes, formulated as [Ln(HL)3(C2H5OH)3] (Ln = Eu3+ or Tb3+; L = 1‐ethyl‐4‐hydroxy‐3‐(nitroacetyl)quinolin‐2‐(1H)‐one). The Eu3+ and Tb3+ complexes have nanospherical morphologies with average particle sizes of 17 and 5 nm, respectively. Pure red and green photoluminescence with long lifetime values has been obtained from the Eu3+ and Tb3+ complexes, respectively, under non‐harmful UVA and blue illumination. Latent fingerprint details, including their characteristic three levels, have been clearly identified from various forensic (non‐porous, semi‐porous, highly fluorescent porous) substrates using red (Eu3+) and green (Tb3+) nanophosphors. The green nanophosphor powder has a greater capability for visualizing latent fingerprints from highly fluorescent porous surfaces as compared to the red one. Both nanophosphor complexes have been used to develop luminescent ink for anti‐counterfeiting applications.  相似文献   

15.
Highly efficient phosphor‐converted light‐emitting diodes (pc‐LEDs) are popular in lighting and high‐tech electronics applications. The main goals of present LED research are increasing light quality, preserving color point stability and reducing energy consumption. For those purposes excellent phosphors in all spectral regions are required. Here, we report on ultra‐narrow band blue emitting oxoberyllates AELi2[Be4O6]:Eu2+ (AE=Sr,Ba) exhibiting a rigid covalent network isotypic to the nitridoalumosilicate BaLi2[(Al2Si2)N6]:Eu2+. The oxoberyllates’ extremely small Stokes shift and unprecedented ultra‐narrow band blue emission with fwhm ≈25 nm (≈1200 cm?1) at λem=454–456 nm result from its rigid, highly condensed tetrahedra network. AELi2[Be4O6]:Eu2+ allows for using short‐wavelength blue LEDs (λem<440 nm) for efficient excitation of the ultra‐narrow band blue phosphor, for application in violet pumped white RGB phosphor LEDs with improved color point stability, excellent color rendering, and high energy efficiency.  相似文献   

16.
1,4‐butanediamine (BEA) is incorporated into FASnI3 (FA=formamidinium) to develop a series of lead‐free low‐dimensional Dion–Jacobson‐phase perovskites, (BEA)FAn?1SnnI3n+1. The broadness of the (BEA)FA2Sn3I10 band gap appears to be influenced by the structural distortion owing to high symmetry. The introduction of BEA ligand stabilizes the low‐dimensional perovskite structure (formation energy ca. 106 j mol?1), which inhibits the oxidation of Sn2+. The compact (BEA)FA2Sn3I10 dominated film enables a weakened carrier localization mechanism with a charge transfer time of only 0.36 ps among the quantum wells, resulting in a carrier diffusion length over 450 nm for electrons and 340 nm for holes, respectively. Solar cell fabrication with (BEA)FA2Sn3I10 delivers a power conversion efficiency (PCE) of 6.43 % with negligible hysteresis. The devices can retain over 90 % of their initial PCE after 1000 h without encapsulation under N2 environment.  相似文献   

17.
We report a new dicalcium silicate phosphor, Ca2?xEuxSiO4, which emits red light in response to blue‐light excitation. When excited at 450 nm, deep‐red emission at 650 nm was clearly observed in Ca1.2Eu0.8SiO4, the external and internal quantum efficiencies of which were 44 % and 50 %, respectively. The red emission from Ca2?xEuxSiO4 was strongly related to the peculiar coordination environments of Eu2+ in two types of Ca sites. The red‐emitting Ca2SiO4:Eu2+ phosphors are promising materials for next‐generation, white‐light‐emitting diode applications.  相似文献   

18.
The influence of Ca2+ doped into the holmium sublattice on the magnetically active surrounding of Sn4+ ions located in the chromium sublattice of Ho1–x Ca x Cr0.997Sn0.003O3 (x = 0, 0.003, and 0.1) compounds was studied by 119Sn Mössbauer spectroscopy. At concentrations [Ca] = [Sn] = 0.3 mol %, an increase was observed in the spectral contribution of Sn4+ sites, having the full number of nearest-neighbor Cr3+cations (n = 6), where they perceived a magnetic field H(Sn)4.2 K = 82 kOe, compared to the contribution of the relevant sites in the undoped chromite (x = 0). This observation was interpreted as resulting from a reduced probability of appearance of Cr3+ vacancies in the nearest surrounding of heterovalent Sn4+ ions. For x = 0.1, on the contrary, the 119Sn spectrum revealed a reduced contribution from the Sn4+ sites with n = 6. This evolution is shown not to be due neither to the appearance of Cr4+ nor Cr6+ ions in the nearest neighborhood of Sn4+ in the chromium sublattice to balance the charge deficiency of the Ca2+ ions doped into the holmium sublattice. This allowed us to suggest that the observed effect was due to the onset of Sn4+ segregations in the structure of Ho0.9Ca0.1Cr0.997Sn0.003O3, which contained a far greater amount of Ca2+ ions whose charge deficiency was balanced mostly by Cr4+ formation. Studies of samples that were prepared under a hydrogen atmosphere revealed the reduction of Sn4+ to the oxidation state +2, with the concomitant stabilization of the formed Sn2+ ions on crystallite surfaces on sites having low coordination numbers.  相似文献   

19.
All inorganic CsPbBr3 perovskite quantum dots (QDs) are potential emitters for electroluminescent displays. We have developed a facile hot‐injection method to partially replace the toxic Pb2+ with highly stable Sn4+. Meanwhile, the absolute photoluminescence quantum yield of CsPb1−x Snx Br3 increased from 45 % to 83 % with SnIV substitution. The transient absorption (TA) exciton dynamics in undoped CsPbBr3 and CsPb0.67Sn0.33Br3 QDs at various excitation fluences were determined by femtosecond transient absorption, time‐resolved photoluminescence, and single‐dot spectroscopy, providing clear evidence for the suppression of trion generation by Sn doping. These highly luminescent CsPb0.67Sn0.33Br3 QDs emit at 517 nm. A device based on these QDs exhibited a luminance of 12 500 cd m−2, a current efficiency of 11.63 cd A−1, an external quantum efficiency of 4.13 %, a power efficiency of 6.76 lm w−1, and a low turn‐on voltage of 3.6 V, which are the best values among reported tin‐based perovskite quantum‐dot LEDs.  相似文献   

20.
Ag/mesoporous black TiO2 nanotubes heterojunctions (Ag‐MBTHs) were fabricated through a surface hydrogenation, wet‐impregnation and photoreduction strategy. The as‐prepared Ag‐MBTHs possess a relatively high specific surface area of ≈85 m2 g?1 and an average pore size of ≈13.2 nm. The Ag‐MBTHs with a narrow band gap of ≈2.63 eV extend the photoresponse from UV to the visible‐light and near‐infrared (NIR) region. They exhibit excellent visible‐NIR‐driven photothermal catalytic and photocatalytic performance for complete conversion of nitro aromatic compounds (100 %) and mineralization of highly toxic phenol (100 %). The enhancement can be attributed to the mesoporous hollow structures increasing the light multi‐refraction, the Ti3+ in frameworks and the surface plasmon resonance (SPR) effect of plasmonic Ag nanoparticles favoring light‐harvesting and spatial separation of photogenerated electron–hole pairs, which is confirmed by transient fluorescence. The fabrication of this SPR‐enhanced visible‐NIR‐driven Ag‐MBTHs catalyst may provide new insights for designing other high‐performance heterojunctions as photocatalytic and photothermal catalytic nanomaterials.  相似文献   

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