Absolute Photoluminescence Quantum Yield Research Articles

Interlaboratory Comparison on Absolute Photoluminescence Quantum Yield Measurements of Solid Light Converting Phosphors with Three Commercial Integrating Sphere Setups.

Scattering luminescent materials dispersed in liquid and solid matrices and luminescent powders are increasingly relevant for fundamental research and industry. Examples are luminescent nano- and microparticles and phosphors of different compositions in various matrices or incorporated into ceramics with applications in energy conversion, solid-state lighting, medical diagnostics, and security barcoding. The key parameter to characterize the performance of these materials is the photoluminescence/fluorescence quantum yield (Φf), i.e., the number of emitted photons per number of absorbed photons. To identify and quantify the sources of uncertainty of absolute measurements of Φf of scattering samples, the first interlaboratory comparison (ILC) of three laboratories from academia and industry was performed by following identical measurement protocols. Thereby, two types of commercial stand-alone integrating sphere setups with different illumination and detection geometries were utilized for measuring the Φf of transparent and scattering dye solutions and solid phosphors, namely, YAG:Ce optoceramics of varying surface roughness, used as converter materials for blue light emitting diodes. Special emphasis was dedicated to the influence of the measurement geometry, the optical properties of the blank utilized to determine the number of photons of the incident excitation light absorbed by the sample, and the sample-specific surface roughness. While the Φf values of the liquid samples matched between instruments, Φf measurements of the optoceramics with different blanks revealed substantial differences. The ILC results underline the importance of the measurement geometry, sample position, and blank for reliable Φf data of scattering the YAG:Ce optoceramics, with the blank's optical properties accounting for uncertainties exceeding 20%.

Chiral Canoe-Like Pd0 or Pt0 Alloyed Copper Alkynyl Nanoclusters Display Near-Infrared Luminescence.

Alloying nanoclusters (NCs) has emerged as a widely explored and versatile strategy for tailoring tunable properties, facilitating in-depth atomic-level investigations of structure-property correlations. In this study, we have successfully synthesized six atomically precise copper NCs alloyed with Group 10 metals (Pd or Pt). Notably, the Pd0 or Pt0 atom situated at the center of the distorted hexagonal antiprism Pd0/Pt0@Cu12 cage, coordinated with twelve Cu+ and two tBuC≡C- ligands. Moreover, ligand exchange strategies demonstrated the potential for Cl- and Br- to replace one or two alkynyl ligands positioned at the top or side of the NCs. The chirality exhibited by these racemic NCs is primarily attributed to the involvement of halogens and a chiral (Pd/Pt)@Cu18 skeleton. Furthermore, all the NCs exhibit near-infrared (NIR) luminescence, characterized by emission peaks at 705-755 nm, lifetimes ranging from 6.630 to 9.662 μs, and absolute photoluminescence quantum yields (PLQYs) of 1.75 %-2.52 % in their crystalline state. The experimental optical properties of these NCs are found to be in excellent agreement with the results of theoretical calculations. These alloy NCs not only offer valuable insights into the synthesis of Pd0/Pt0-Cu alloy NCs, but also bridge the gap in understanding the structure-luminescence relationships of Pd0/Pt0-Cu molecules.

Chiral Canoe‐Like Pd0 or Pt0 Alloyed Copper Alkynyl Nanoclusters Display Near‐Infrared Luminescence

AbstractAlloying nanoclusters (NCs) has emerged as a widely explored and versatile strategy for tailoring tunable properties, facilitating in‐depth atomic‐level investigations of structure‐property correlations. In this study, we have successfully synthesized six atomically precise copper NCs alloyed with Group 10 metals (Pd or Pt). Notably, the Pd0 or Pt0 atom situated at the center of the distorted hexagonal antiprism Pd0/Pt0@Cu12 cage, coordinated with twelve Cu+ and two tBuC≡C− ligands. Moreover, ligand exchange strategies demonstrated the potential for Cl− and Br− to replace one or two alkynyl ligands positioned at the top or side of the NCs. The chirality exhibited by these racemic NCs is primarily attributed to the involvement of halogens and a chiral (Pd/Pt)@Cu18 skeleton. Furthermore, all the NCs exhibit near‐infrared (NIR) luminescence, characterized by emission peaks at 705–755 nm, lifetimes ranging from 6.630 to 9.662 μs, and absolute photoluminescence quantum yields (PLQYs) of 1.75 %–2.52 % in their crystalline state. The experimental optical properties of these NCs are found to be in excellent agreement with the results of theoretical calculations. These alloy NCs not only offer valuable insights into the synthesis of Pd0/Pt0‐Cu alloy NCs, but also bridge the gap in understanding the structure‐luminescence relationships of Pd0/Pt0‐Cu molecules.

Polymer Microspheres Copolymerized with Deep Red Fluorescent Molecules as a Label for Lateral Flow Immunochromatography.

The development of fluorescently labeled microspheres is a critical aspect of advancing the technology of lateral flow immunochromatography (LFIA) for biological detection. Nevertheless, potential interference posed by the background fluorescence originating from the nitrocellulose (NC) membrane would significantly impact the sensitivity and accuracy of microsphere-based detection in LFIA. In this work, an attempt was made to extend the π-conjugated system and asymmetric structure of rhodamine fluorophore, resulting in the synthesis of dye molecules (RB2) incorporating double bonds, which can reach an absolute photoluminescence quantum yield (PLQY) of 30.01% in EtOH. Subsequently, carboxyl group functionalized fluorescent microspheres were prepared in a two-step copolymerization via soap-free emulsion polymerization. The obtained microspheres were characterized by scanning electron microscopy, transmission electron microscopy, DLS, Fourier transform infrared spectroscopy, ultraviolet spectrophotometry, and fluorescence spectrophotometry. The results showed that RB2 was successfully copolymerized into the microspheres, and the resulting microspheres had good dispersion and stability with high red fluorescence intensity (λabs ∼ 610 nm, λem ∼ 660 nm). Utilizing these microspheres, the resulting lateral flow immunoassay was successfully found to detect SARS-CoV-2 N protein with a detection limit of 2.5 pg/mL and the linear concentration spanning from 2.5 pg/mL to 10 ng/mL. The results confirm the effectiveness of the synthetic fluorescent microspheres as the label for LFIA.

Ultra-stable and highly-bright CsPbBr3 perovskite/silica nanocomposites for miRNA detection based on digital single-nanoparticle counting

Single-nanoparticle counting (SNPC) based on fluorescent tag (FT) stands out for its capacity to achieve amplification-free and sensitive detection of biomarkers. The stability and luminescence of FT are important to the sensitivity and reliability of SPNC. In this work, we developed novel perovskite/silica nanocomposites by in-situ nanoconfined growth of CsPbBr3 nanocrystals inside mesoporous structure of silica nanoparticles. PbBr(OH) was formed in an alkaline-assisted reaction triggered by water on the surface of CsPbBr3 nanocrystals. The as-obtained nanocomposites, featuring dual protection from silica matrix and PbBr(OH), exhibited high absolute photoluminescence quantum yield (PLQY) of 86.5% and demonstrated outstanding PL stability confronting with water, heat, ultrasound and UV-irradiation, which is desired by SNPC-based biosensor. Thereafter, these nanocomposites were used to construct an operationally friendly SNPC assay for the amplification-free quantification of cancer-associated miRNA. Quantitative detection of miRNA could be accomplished by directly counting the number of nanocomposites using a flow cytometer in this assay. This strategy did not ask for multiple washing steps and demonstrated specific and sensitive detection of miRNA 21, which exhibited a dynamic range of 1–1000 pM and limit of detection of 79 amol. The employment of highly stable perovskite/silica nanocomposites improved the test reliability and stability of SNPC, revealing the vast potential of perovskites in biosensing.

Extremely Enhanced Photoluminescence in MoS2-Derived Quantum Sheets.

Molybdenum disulfide (MoS2) quantum sheets (QSs) are attractive for applications due to their tunable energy band structures and optical and electronic properties. The photoluminescence quantum yield (PLQY) of MoS2 QSs achieved by mechanical and liquid exfoliation and chemical vapor deposition is low. Some studies have reported that chemical treatment and elemental doping can improve the PLQY of transition metal dichalcogenides (TMDs), but this is limited by complex instruments and reactions. In this study, a heat treatment method based on a polar solvent is reported to improve the PLQY and photoluminescence (PL) intensity of MoS2 QSs at room temperature. The absolute PLQY of treated MoS2 QSs is increased to 18.5%, and the PL intensity is increased by a factor of 64. This method is also effective for tungsten disulfide (WS2) QSs. The PL enhancement of QSs is attributed to oxidation of the edges. Such passivation/deformation of MoS2 QSs facilitates the radiative route rather than the nonradiative route, resulting in extreme enhancement of the PL. Our work could provide novel insights/routes toward the PL enhancement of TMD QSs.

Solid-State Emissive Pillar[6]arene Derivative Having Alternate Methylene and Nitrogen Bridges.

Macrocyclic arenes show conformational adaptability, which allows host-guest complexations with the size-matched guest molecules. However, their emission properties are often poor in the solid states due to the self-absorption. Herein, we newly synthesized pillar[6]arene derivatives having alternate methylene and nitrogen bridging structures. Solvatochromic study reveals that the nitrogen-embedding into the cyclic structures can strengthen the intramolecular charge transfer (CT) nature compared to that of the linear nitrogen-bridged precursor. Owing to the large Stokes shift in the solid state, one of the nitrogen-embedded pillar[6]arenes shows high absolute photoluminescence quantum yield (ΦPL=0.36). Furthermore, it displays a turn-off sensing ability toward nitrobenzene (NB) vapor; a fluorescence quenching is observed when exposed to the NB vapor. From the structural analysis before and after the exposure of NB vapor, the amorphous nitrogen-embedded pillar[6]arene efficiently co-crystallize with NB and formed non-emissive intermolecular CT complexes with NB.

The Narrow Synthetic Window for Highly Homogenous InP Quantum Dots toward Narrow Red Emission.

Low-toxicity InP-based quantum dots (QDs) exhibit potential for replacing Cd/Pb-containing QDs in the visible and near-infrared regions. Despite advancements, further improvement relies on synthesizing homogeneous InP QDs to achieve a high color purity. In a commonly employed two-step "seed-mediated" synthetic approach, we demonstrate the high sensitivity of InP seed sizes and size distribution to the quantities of trioctylphosphine (TOP) and tris(trimethylsilyl)phosphine [(TMS)3P], attributed to the process of "self-focusing of size distribution" and enhanced reactivity of In-oleate through coordination with TOP. During growth, the processes of size focusing and defocusing are modulated by the accumulation of oleic acid and TOP molecules, as well as the amount of (TMS)3P in the growth precursor, which may relate to the dissolution process of InP magic size clusters. Through precise control, the best valley/depth ratio of InP QDs was 0.52 at the first absorption peak at 571 nm, resulting in luminescence with a full width at half-maximum of 35 at 620 nm with an absolute photoluminescence quantum yield around 90% after heteroepitaxial growth with ZnSe and ZnS shells.

High Mobility Emissive Excimer Organic Semiconductor Towards Color-Tunable Light-Emitting Transistors.

Organic light-emitting transistors (OLETs) are highly integrated and minimized optoelectronic devices with significant potential superiority in smart displays and optical communications. To realize these various applications, it is urgently needed for color-tunable emission in OLETs, but remains a great challenge as a result of the difficulty for designing organic semiconductors simultaneously integrating high carrier mobility, strong solid-state emission, and the ability for potential tunable colors. Herein, a high mobility emissive excimer organic semiconductor, 2,7-di(2-anthryl)-9H-fluorene (2,7-DAF) was reasonably designed by introducing a rotatable carbon-carbon single bond connecting two anthracene groups at the 2,7-sites of fluorene, and the small torsion angles simultaneously guarantee effective conjugation and suppress fluorescence quenching. Indeed, the unique stable dimer arrangement and herringbone packing mode of 2,7-DAF single crystal enables its superior integrated optoelectronic properties with high carrier mobility of 2.16 cm2 ⋅ V-1 ⋅ s-1 , and strong excimer emission with absolute photoluminescence quantum yield (PLQY) of 47.4 %. Furthermore, the voltage-dependent electrically induced color-tunable emission from orange to blue was also demonstrated for an individual 2,7-DAF single crystal based OLETs for the first time. This work opens the door for a new class of high mobility emissive excimer organic semiconductors, and provides a good platform for the study of color-tunable OLETs.

High Mobility Emissive Excimer Organic Semiconductor Towards Color‐Tunable Light‐Emitting Transistors

AbstractOrganic light‐emitting transistors (OLETs) are highly integrated and minimized optoelectronic devices with significant potential superiority in smart displays and optical communications. To realize these various applications, it is urgently needed for color‐tunable emission in OLETs, but remains a great challenge as a result of the difficulty for designing organic semiconductors simultaneously integrating high carrier mobility, strong solid‐state emission, and the ability for potential tunable colors. Herein, a high mobility emissive excimer organic semiconductor, 2,7‐di(2‐anthryl)‐9H‐fluorene (2,7‐DAF) was reasonably designed by introducing a rotatable carbon–carbon single bond connecting two anthracene groups at the 2,7‐sites of fluorene, and the small torsion angles simultaneously guarantee effective conjugation and suppress fluorescence quenching. Indeed, the unique stable dimer arrangement and herringbone packing mode of 2,7‐DAF single crystal enables its superior integrated optoelectronic properties with high carrier mobility of 2.16 cm2 ⋅ V−1 ⋅ s−1, and strong excimer emission with absolute photoluminescence quantum yield (PLQY) of 47.4 %. Furthermore, the voltage‐dependent electrically induced color‐tunable emission from orange to blue was also demonstrated for an individual 2,7‐DAF single crystal based OLETs for the first time. This work opens the door for a new class of high mobility emissive excimer organic semiconductors, and provides a good platform for the study of color‐tunable OLETs.

Thermally activated delayed fluorescence Au‐Ag‐oxo nanoclusters: From photoluminescence to radioluminescence

AbstractThermally activated delayed fluorescence (TADF) materials have numerous applications in energy conversion and luminescent imaging. However, they are typically achieved as metal‐organic complexes or pure organic molecules. Herein, we report the largest Au‐Ag‐oxo nanoclusters to date, Au18Ag26(R1COO)12(R2C≡C)24(μ4‐O)2(μ3‐O)2 (Au18Ag26, where R1 = CH3‐, Ph‐, CHOPh‐ or CF3Ph‐; R2 = Ph‐ or FPh‐). These nanoclusters exhibit exceptional TADF properties, including a small S1‐T1 energy gap of 55.5 meV, a high absolute photoluminescence quantum yield of 86.7%, and a microseconds TADF decay time of 1.6 μs at ambient temperature. Meanwhile, Au18Ag26 shows outstanding stability against oxygen quenching and ambient conditions. Atomic level analysis reveals the strong π⋯π and C‐H⋯π interactions from the aromatic alkynyl ligands and the enhancement of metal‐oxygen‐metal interactions by centrally coordinated O2−. Modeling of the electronic structure shows spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital, which promote charge transfer from the ligand shell, predominantly carboxylate ligands, to O2−‐embedded metal core. Furthermore, TADF Au‐Ag‐oxo nanoclusters exhibit promising radioluminescence properties, which we demonstrate for X‐ray imaging. Our work paves the way for the design of TADF materials based on large metal nanoclusters for light‐emission and radioluminescence applications.

(Invited) Calibration of Upconverting Materials and Nanoprobes

Upconversion has attracted much attention for the potential applications of nanomaterials and bulk materials. Upconversion nanoprobes and sensors rely on the non-linear emission of the reporters, which present a low efficiency due to their anti-Stokes nature. For these two reasons, the materials require accurate and contrastable efficiency measurements, typically by measuring the absolute upconversion quantum yield (UCQY). The methodology for such measurements will vary from traditional photoluminescence quantum yield techniques that have been applied for downshifting materials [1]. Effects like the scattering, broadband absorption and reemission, inner-filter effects, thickness, self-absorption, and temperature, have to be considered [2].This presentation will focus on some of these effects. The scattering has usually been neglected, however systems with scattering can increase the power density and subsequently the UCQY, as demonstrated both experimentally and via simulations [3]. Furthermore, this energy concentration also provides a new method for identifying the refractive index of phosphors, which is useful since some phosphors cannot be produced in macroscopic sizes. Broadband characterisation enables a route for characterisation exploiting the wide energy levels at the near-infrared. However, it introduces new challenges such as reemission [4]. In the case of applications that use a thick upconverted, the thickness is also a key parameter that can be responsible up to 50% of the emission [5].Finally, one of the applications that is been intensively researched is the use of upconverting and downshifting nanoparticles as temperature reporters. Absolute upconversion photoluminescence quantum yield characterisation for different probes will be presented with a modified integrating sphere that allows in-situ absorption and emission measurements.

Creation of an oxygen-enriched environment during synthesis as an effective way to improve luminescent properties of Y2O3:Eu3+☆

The growing demand for luminescent nanomaterials intended for various applications increases the necessity to develop and improve approaches to the creation of highly efficient nanosized phosphors. In current study, an approach to enhancing the efficiency of red luminescence of monoclinic Y2O3:Eu3+ with the particle size of ∼20 nm by creating the oxygen-enriched environment during the gas-phase synthesis was developed. To investigate the effect of oxygen amount during the synthesis on characteristics of the phosphor, a series of nanostructured Y2O3:Eu3+ with the addition of 0–40 vol% O2 to the main buffer gas Ar was synthesized by laser vaporization. It is shown that the amount of added O2 exerts virtually no effect on the phase composition and particle size, but significantly improves the luminescent characteristics of Y2O3:Eu3+. Thus, the addition of 30 vol% O2 leads to virtually a 20-fold growth in the photoluminescence (PL) intensity caused by 5D0→7F0–4 transitions in Eu3+ and an increase in the absolute PL quantum yield from 3% to 53% (λex = 395 nm) compared to the sample synthesized without O2. The addition of oxygen also improves the emission color coordinates from (0.571, 0.320) to (0.630, 0.322) due to the removal of a considerable fraction of oxygen vacancies. The synthesized nanopowders are shown to be highly stable: upon storage under ambient conditions for two years. Quantum yield (QY) of the samples decreases by less than 2%. It is expected that the key features underlying the proposed approach will be useful for various methods used to synthesize oxide nanophosphors.

Multi‐Color Pure Organic Room Temperature Phosphorescent Materials with Long Lifetime and High Efficiency

AbstractOrganic room temperature phosphorescent (ORTP) materials have garnered significant interest in the fields of anti‐counterfeiting, optical display, and bio‐imaging owing to their distinctive optical properties. However, a major drawback of most existing ORTP materials is their short phosphorescence lifetime and low quantum yields (QYs), which greatly limit their applicability across multiple fields. In this paper, a covalently assisted host‐guest doping strategy that involves embedding three aminobenzoic acids with different carboxylate substitution positions into a cyanuric acid (CA) matrix through covalent bonding using microwave heating is proposed. All three prepared ORTP materials exhibit long phosphorescence lifetime exceeding 600 ms and high phosphorescence quantum yields (PhQYs) surpassing 20%. Among them, the composite of 2‐aminoterephthalic acid (2‐A) anuric acid stands out with its unique blue phosphorescence, boasting an exceptional absolute photoluminescence quantum yield (PLQY) of 98.95% and remarkable phosphorescence quantum yield (PhQY) of 76.42%, along with a long lifetime of 800 ms. Importantly, these high‐performance ORTP materials have been successfully utilized in anti‐counterfeiting and display applications.

Enhancing Circularly Polarized Luminescence in Quantum Dots through Chiral Coordination-Mediated Growth at the Liquid/Liquid Interface.

Here, we develop a novel methodology for synthesizing chiral CdSe@ZnS quantum dots (QDs) with enhanced circularly polarized luminescence (CPL) by incorporating l-/d-histidine (l-/d-His) ligands during ZnS shell growth at the water/oil interface. The resulting chiral QDs exhibit exceptional absolute photoluminescence quantum yield of up to 67.2%, surpassing the reported limits of 40.0% for chiral inorganic QDs, along with absorption dissymmetry factor (|gabs|) and luminescence dissymmetry factor (|glum|) values of 10-2, exceeding the range of 10-5-10-3 and 10-4-10-2, respectively. Detailed investigations of the synthetic pathway reveal that the interface, as a binary synthetic environment, facilitates the coordinated ligand exchange and shell growth mediated by chiral His-Zn2+ coordination complexes, leading to a maximum fluorescent brightness and chiroptical activities. The growth process, regulated by the His-Zn2+ coordination complex, not only reduces trap states on the CdSe surface, thereby enhancing the fluorescence intensity, but also significantly promotes the orbital hybridization between QDs and chiral ligands, effectively overcoming the shielding effect of the wide bandgap shell and imparting pronounced chirality. The proposed growth pathway elucidates the origin of chirality and provides insights into the regulation of the CPL intensity in chiral QDs. Furthermore, the application of CPL QDs in multilevel anticounterfeiting systems overcomes the limitations of replication in achiral fluorescence materials and enhances the system's resistance to counterfeiting, thus opening new opportunities for chiral QDs in optical anticounterfeiting and intelligent information encryption.

Sulfone/Carbonyl-Based Donor-Acceptor Fluorescent Dyes: Synthesis, Structures, Photophysical Properties and Cell Imaging.

Electron-accepting units play vital roles in constructing donor-acceptor (D-A) conjugated organic optoelectronic materials; the electronic structures and functions of the acceptors need to be carefully unveiled to controllably tailor the optoelectronic properties. We have synthesized two D-A conjugated organic fluorophores, TPA-SO and TPA-CO, with similar molecular skeletons based on sulfone- or carbonyl-containing polycyclic aromatic acceptors. Both TPA-SO and TPA-CO display obvious solvent polarity-dependent photophysical properties and large Stokes shift of over 100 nm for strong intramolecular charge transfer processes. Experimental evidence indicates that the sulfone group in TPA-SO merely serves as a strong electron-withdrawing unit. TPA-SO shows yellowish-green emission with a peak at 542 nm and an absolute photoluminescence quantum yield (PLQY) of 98 % in solution, whereas the carbonyl group in TPA-CO can act as both an electron-withdrawing unit and spin transition convertor, so TPA-CO displays red emission with a low absolute PLQY of 0.32 % in solution. Impressively, upon going from solution to aggregate state, TPA-SO nanoparticles keep a high PLQY of 9.5 % and moderate biocompatibility, thus they are good nano-agents for cellular fluorescence imaging. The results reveal that the inherent acceptor characteristic acts as a crucial effect in the photophysical properties and applications of the organic fluorophores.

Enhancing blue phosphorescence in matrix-free carbon dots through covalent crosslinking

Room temperature phosphorescence (RTP) of carbon dots (CDs) has received extensive attention due to its excellent performance and promising application. Here, a novel kind of matrix-free CDs with blue phosphorescence emission was synthesized by a simple one-step hydrothermal method of heating (3-Aminopropyl) trimethoxysilane (APTMS) and phosphoric acid in aqueous solution. The obtained CDs show a phosphorescence lifetime of 315.73 ms, and the absolute photoluminescence quantum yield (PLQY) and the phosphorescence quantum yield (PQY) can reach up to 37.8 % and 12.4 %, respectively. From the experimental results, we speculate that the generation of RTP is attributed to the restriction effect of the covalent crosslinking structure of SiOSi, SiOC, or SiC bonds formed on the CDs surface. In addition, phosphoric acid as a crosslinking agent and heteroatom dopant can promote the formation of cross-linked structures and facilitate the intersystem crossing (ISC) process, thus enhancing room temperature phosphorescence. Finally, the CDs were successfully used in information encryption and anti-counterfeiting.

Single Molecular Persistent Room-Temperature Phosphorescence and Circularly Polarized Luminescence from Binaphthol-Decorated Optically Innocent Cyclotriphosphazenes.

Circularly polarized luminescence (CPL) features of BINOL-decorated cyclotriphosphazenes (CPs) are reported for the first time. The luminescence dissymmetry factor (glum ) of these compounds in chloroform solutions and polymethyl methacrylate (PMMA) thin films with wt 1 % doping concentrations are found to be 1.0×10-3 , and 2.9×10-3 , respectively. However, no CPL signal is observed for the pristine solids. The enantiomers (CP-(R)/CP-(S)) show ultraviolet photoluminescence (~350-360 nm) in solution and the solid state. These compounds show ~10 times larger absolute photoluminescence quantum yield (PLQY) than the simple BINOLs in the solutions state. In the solid state, CP-(R) shows larger PLQY than binaphthol-(R); in contrast, the S enantiomer shows lower PLQY than binaphthol-(S); this indicates that the isomer-dependent solid-state packing of these compounds plays a crucial role in controlling the PL. Thin films with more than 1 % doping concentration and pristine solids of these compounds do not show persistent room-temperature phosphorescence (pRTP) due to concentration-caused quenching. However, thin films with wt 1 % of these chiral emitters exhibit pRTP characteristics with a ~159-343 ms lifetime under vacuum. Theoretical calculations reveal that the cyclophosphazene acts as an optically innocent dendritic core, and the optical features of these compounds are dictated by the pendent BINOL chromophore.

Effect of SiO2 shell on photoluminescence enhancement of Eu3+ doped nanophosphor based on monoclinic Y2O3

Surface SiO2 coating strategy was used to enhance the photoluminescent properties of Eu3+ doped nanophosphor based on monoclinic Y2O3. Laser-synthesized m-Y2O3:Eu3+ spherical nanoparticles with high crystallinity and diameter of ca. 18 nm were used as a core for the preparation of m-Y2O3:Eu3+@SiO2 core-shell structures. According to HRTEM and HAADF-STEM data, a thin SiO2 shell uniformly encapsulated the crystal core with a thickness of about 1.5 nm. The SiO2 shell increases the absolute photoluminescence quantum yield of Eu3+ at λ = 395 nm excitation from 14 % to 68 %. To the best of our knowledge, the obtained quantum yield exceeds the known values for Eu3+ doped oxide-based nanophosphors and is comparable to those of some other commercial red microphosphors. The SiO2 coating was shown to reduce the luminescence quenching effect associated with the annealing-induced migration of Eu3+ from the bulk to the surface of nanoparticles. The obtained results demonstrate that m-Y2O3:Eu3+@SiO2 core-shell nanoparticles with intense red luminescence have significant potential for use in LEDs, high resolution displays, bioimaging technologies and in other solid-state lighting applications.

Spectroscopy and absolute photoluminescence quantum yield of Eu3-doped zinc-tellurite glasses for solid state lightning applications

Spectroscopic properties of Eu3+-doped tellurite glass composed of 74 TeO2 + 15 ZnO +5 Nb2O5 + 5 TiO2 + 1.0 Eu2O3(mol %) have been investigated. Phonon energy of the host glass constituents that are linked up with the Eu3+ ions have been evaluated from the photoluminescence excitation spectrum which is found to be 760 cm−1. By utilizing the emission spectrum, the Judd-Ofelt (JO) intensity parameters (Ωλ, λ = 2 and 4) are calculated. The obtained JO parameters are utilized for evaluating the emission cross-sections (σ(λp)) of 5D0 → 7FJ (J = 1, 2 and 4) transitions. An intense emission at 613 nm due to the transition5D0 → 7F2is observed upon 465 nm excitation. Among these, the 5D0 → 7F2 (613 nm) transition has been exhibited the highest (σ(λp)) value and it found to be 2.11 × 10−22 cm2. For the 5D0 level, quantum efficiency (η) is corroborated theoretically as 58.4% and it is in line with absolute quantum yield of 56.7% obtained by Integrating sphere method. The results of Eu3+-doped TZNTEu1.0 glass are significant for the development of solid-state lighting devices at around 613 nm under the excitation of 465 nm.