Good Luminescence Properties Research Articles

Fluorescent Tetraphenylethylene-Based Cerium Metal-Organic Frameworks for White-Light-Emitting Diodes.

Discovery of highly efficient and thermal stable phosphors is the focus of the studies in phosphor-converted white light-emitting diodes (LEDs). Herein, a tetraphenylethylene-based cerium metal-organic framework (SYNU-2) was synthesized and characterized. The intricate architecture of SYNU-2 shows an overall 3D → 3D 2-fold interpenetration framework. SYNU-2 exhibited good luminescence properties, and its latent fingerprint developer was prepared, which showed good fluorescence and stability under ultraviolet (UV) radiation. It is worth noting that a prototype WLED device can be designed using SYNU-2 and red phosphors (Ca,Sr)AlSiN3:Eu2+ with CIE coordinates of (0.33, 0.33) at an applied 3 V bias.

Multifunctional Organometallic Compounds: An Interesting Luminescent NLO‐active Alkynylplatinum(II) Complex

Reaction of 4‐methylphenylacetylide with the known chlorido platinum(II) complex bearing the cyclometalated 1,3‐bis(pyridin‐2‐yl)‐4,6‐difluoro‐benzene ligand afforded a novel alkynyl platinum(II) complex, 1, that was fully characterized by elemental analysis, NMR and UV‐visible spectroscopies, and by photoluminescence measurements. Its structure was determined by X‐ray diffraction studies on a single crystal whereas its second‐order nonlinear optical (NLO) properties were determined in solution by the Electric‐Field Induced Second Harmonic generation method. The novel multifunctional complex 1 is characterized by good luminescence properties, like the related chlorido Pt(II) complex, but by a much higher second‐order NLO response.

Formation mechanism and luminescence properties of silicon carbide nanowires with core-shell structure

For the preparation of SiC nanowires (SiC NWs) by carbothermal reduction, it is of great significance to study the formation mechanism of sic nanowires for process optimization and the controllable preparation. Although first-principles molecular dynamics (FPMD) can simulate systems of hundreds of atoms on a picosecond time scale, the results of FPMD are still insufficient to elucidate the formation mechanism of core-shell SiC nanowires. To make up this deficiency, this article has conducted Deep Potential Molecular Dynamics (DPMD) simulation on nanoseconds timescales with near FPMD accuracy for systems containing thousands of atoms, the results more concretively show the formation process of core-shell SiC nanowires. DPMD simulation results show when CO molecules react with SiO molecules, CO molecules are wrapped by SiO molecules to form agglomerates, SiO molecules in the agglomerates that can come into contact with the wrapped CO molecules will react with wrapped CO molecules to form the SiC core, and SiO molecules that in the outer layer of the agglomerates will disproportionate into the amorphous SiO2 shell. Furthermore, the formation mechanism of SiC nanowires was validated in combination with thermodynamics and experimental methods. Thermodynamic results show that vacuum conditions are favorable for the formation of SiO and CO and lower the temperature of SiC preparation. Finally, the core-shell structure of SiC NWs with good luminescence properties were successfully prepared by carbothermal reduction method using carbon black and silicon dioxide as raw materials under the pressure of less than 5 kPa.

The Effects of Pore Defects in π-Extended Pentadecabenzo[9]helicene.

The introduction of precise pore defects into nanocarbon structures results in the emergence of distinct physicochemical characteristics. However, there is a lack of research on non-planar chiral nanographene involving precise pore defects. Herein, we have developed two analogues to the π-extended pentadecabenzo[9]helicene (EP9H) containing embedded pore defects. Each molecules, namely extended dodecabenzo[7]helicene (ED7H; 1) or extended nonabenzo[5]helicene (EN5H; 2), exhibits dual-state emission. Significantly, the value of |glum| of 1 is exceptionally high at 1.41×10-2 in solution and BCPL as 254 M-1 cm-1. In PMMA film, |glum| of 1 is 8.56×10-3, and in powder film, it is 5.00×10-3. This study demonstrates that nanocarbon molecules with pore defects exhibit dual-state emission properties while maintaining quite good chiral luminescence properties. It was distinguished from the aggregation-caused quenching (ACQ) effect corresponding to the nanocarbon without embedded defect. Incorporating pore defects into chiral nanocarbon molecules also simplifies the synthesis process and enhances the solubility of the resulting product. These findings suggest that the introduction of pore defects can be a viable approach to improve nanocarbon molecules.

The Effects of Pore Defects in π‐Extended Pentadecabenzo[9]helicene

AbstractThe introduction of precise pore defects into nanocarbon structures results in the emergence of distinct physicochemical characteristics. However, there is a lack of research on non‐planar chiral nanographene involving precise pore defects. Herein, we have developed two analogues to the π‐extended pentadecabenzo[9]helicene (EP9H) containing embedded pore defects. Each molecules, namely extended dodecabenzo[7]helicene (ED7H; 1) or extended nonabenzo[5]helicene (EN5H; 2), exhibits dual‐state emission. Significantly, the value of |glum| of 1 is exceptionally high at 1.41×10−2 in solution and BCPL as 254 M−1 cm−1. In PMMA film, |glum| of 1 is 8.56×10−3, and in powder film, it is 5.00×10−3. This study demonstrates that nanocarbon molecules with pore defects exhibit dual‐state emission properties while maintaining quite good chiral luminescence properties. It was distinguished from the aggregation‐caused quenching (ACQ) effect corresponding to the nanocarbon without embedded defect. Incorporating pore defects into chiral nanocarbon molecules also simplifies the synthesis process and enhances the solubility of the resulting product. These findings suggest that the introduction of pore defects can be a viable approach to improve nanocarbon molecules.

Achieving Ultrahigh Thermal Stability in Cr3+-Activated Garnet Phosphors through Electron Migration between Thermally Coupled Levels.

Recently, Cr3+-activated near-infrared (NIR) phosphors have received much more attention due to their excellent photoluminescence (PL) properties. However, most of them suffer from poor thermal stability which limits further application. Herein, a novel Lu2CaGa4SnO12:Cr3+ phosphor with broadband NIR emission (λem = 750 nm) is synthesized successfully. Despite the good luminescence property, its PL intensity decreases obviously with temperature (I425K = 79%). To improve the thermal stability, a series of Lu2+xCa1-xGa4+xSn1-xO12:Cr3+ (x = 0-1.0) solid solutions with tunable thermal quenching performance have been designed. It is found that the fluorescence intensity ratio (FIR) of 4T2 → 4A2 to 2E → 4A2 [I(4T2)/I(2E)] transitions (i.e. electron occupation) decreases monotonously with increasing [Lu3+-Ga3+] co-substitution, resulting from a strengthened crystal field strength and increased energy difference between 4T2 and 2E energy levels. Benefiting from the various thermal population and energy difference Δ', the PL thermal quenching behavior of Lu2+xCa1-xGa4+xSn1-xO12:Cr3+ can be adjusted easily, and the corresponding mechanism is explored in detail. Most notably, the emission intensity of Lu2+xCa1-xGa4+xSn1-xO12:Cr3+ at 425 K can reach up to 142% compared with that at 300 K, which may be the best for Cr3+-activated NIR phosphors. This work may provide an alternative path for the development of thermally stable broadband NIR phosphors.

Enhanced stability of perovskite CsPbBr3 QDs via Synergetic encapsulation with ZnO nanocrystals and commercial polymer

Lead halide perovskite nanocrystals with attractive optical properties and low-cost production have emerged as a reliable and promising candidate for next-generation display applications. However, the preparation of optical devices while maintaining high performance in complex environments poses a prominent challenge. Herein, a flexible, stretchable and stable nanocomposite was fabricated through embedding CsPbBr3 QDs (PeQDs) into ZnO nanocrystals and polymer, leading to the enhancements of both stability and luminescence efficiency. This simple approach allows PeQDs own a uniform size of ∼14 nm. Optical characterization showed that the PeQDs size did not change after embedding ZnO nanocrystals, while these QDs exhibit a distinct green emission, with emission centering at 518 nm and narrow bandwidth of ∼20 nm. It was also found that the PeQDs/ZnO/EPDM nanocomposite maintained sufficient stability even after being left in an outdoor environment for 27 days, soaked in water for 60 h, and placed on a hot plate at 90 °C for 60 min. Besides, nanocomposite still maintain good luminescent properties even when stretched four times its original length. Furthermore, using this PeQDs/ZnO/EPDM nanocomposite, the synthesized white light emitting diode (WLED) exhibits a color gamut coverage rate of 129 % under standard NTSC, and 97 % under standard Rec.2020. By using this PeQDs/ZnO/EPDM encapsulation adhesive film, the absolute efficiency of solar cell can be improved by 0.23 %. This work highlights a new insight into defect passivation techniques for PeQDs by the utilization of heterogeneous structures provided by metal oxides.

Preparing Coordination Polymers with Acentric-Centric Structural Arrangements Related to SHG Response.

Three coordination polymers were successfully constructed in this work by applying biligands and were distinctly characterized through single crystal X-ray diffraction. The compounds crystallized in acentric and centric space groups under the direction of coordination bonds and adopted 1-dimensional link and 2-dimensional layer structures, as well as different coordination geometries for metal atoms. All compounds exhibited good thermal stability and luminescence properties, and compound 2 exhibited a good second harmonic generation (SHG) response. The method used in this work offers a feasible approach to using biligand and changing metal salt to obtain the microstructures of coordination materials with specific properties.

An ultrawide-range photochromic molecular fluorescence emitter

Photocontrollable luminescent molecular switches capable of changing emitting color have been regarded as the ideal integration between intelligent and luminescent materials. A remaining challenge is to combine good luminescence properties with wide range of wavelength transformation, especially when confined in a single molecular system that forms well-defined nanostructures. Here, we report a π-expanded photochromic molecular photoswitch, which allows for the comprehensive achievements including wide emission wavelength variation (240 nm wide, 400–640 nm), high photoisomerization extent (95%), and pure emission color (<100 nm of full width at half maximum). We take the advantageous mechanism of modulating self-assembly and intramolecular charge transfer in the synthesis and construction, and further realize the full color emission by simple photocontrol. Based on this, both photoactivated anti-counterfeiting function and self-erasing photowriting films are achieved of fluorescence. This work will provide insight into the design of intelligent optical materials.

Структура, ріст та оптичні характеристики монокристалів сульфанілату гуанідинію (GSA)

Guanidine Sulphanilate (GSA) single crystal was grown by slow evaporation growth method. Single crystal X-ray diffraction studies show that the crystal grows in a centro symmetric monoclinic system and its space group is P21/c. Optical studies were carried out using UV visible spectroscopy and the grown crystal shows the the lower cutoff wavelength of 220 nm. Photoluminescence studies show that GSA crystals have good luminescence properties. Laser damage threshold was found to be 0.24GW/cm2. Nonlinear optical studies show green light emission.

Synthesis of high quality green phosphors by co-precipitation and induction heating

With the development of light-emitting diodes (LEDs) display and lighting industry, new requirements have been put forward for phosphors. Traditional syntheses of phosphors face the problems of slow temperature increase, long holding time and corresponding larger particle size. In this work, a co-precipitation combined with induction heating method was developed for the fast and efficient synthesis of Lu2.97Al5O12:0.03Ce3+ (LuAG:0.03Ce) phosphors. The effects of calcination temperature and holding time on the morphology and luminescence properties were investigated. The phosphor synthesized at 1600 °C for 10 min (10 min@1600 °C) has an average particle size of 500 nm, and exhibits good luminescence properties and thermal stability (maintaining 92.04 % of room temperature light intensity at 200 °C). The luminescence intensity and the external quantum efficiency (EQE) of the phosphor (60 min@1500 °C) are higher than those of a commercial phosphor. The light source fabricated with phosphor ceramic prepared by the phosphor (10 min@1500 °C) shows a luminous efficacy (LE) of 193 lm/W. Therefore, co-precipitation combined with induction heating is an energy-saving and promising method for the synthesis of phosphor.

Aromatimide tetracarboxylate metal-framework materials: Fluorescence sensing application towards NACs and small drug molecules

Three multifunctional fluorescent Metal-Organic Framework (MOF) sensors are synthesized based on N, N’-bis(3, 5-dicarboxyphenyl)isophthalic diimide (H4BDCPPI) with Zn, Cu, and Cd ions. Structural analysis shows that although using the same organic conjugated aromatic imide tetracarboxylic acids ligand, their corresponding structures are different. Based on luminescence characteristics of the organic components, they exhibit good luminescent properties. They can sensitively detect nitro aromatic compounds (p-nitrophenol (PNP), 2,4-dinitrophenol (DNP) and 2,4,6-trinitrophenol (TNP)) and small drug molecules (colchicine and balsalazide disodium) with low limit of detection. The complex 1 is more sensitive for detection of TNP, compared to the other complexes. The mechanism of fluorescence sensing is proposed in detail based on analyses of PXRD, fluorescence lifetimes, and UV–vis spectra. This study explores the potential of MOFs based on H4BDCPPI in the field of fluorescence sensing for the first time, laying the theoretical foundation for application of complexes with conjugated aromatic imide tetracarboxylic acids.

Study on Artificial Light‐Harvesting System Based on Polymer Organogels

AbstractHerein, a simple method for developing an artificial light‐harvesting system (ALHS) based on polymer organogels using benzimidazole carboxylic acid derivatives (RJ) is introduced. The prepared polymer organogels (RJZ) exhibited good luminescence and mechanical properties. The involved energy transfer was obtained by employing RJZ as a donor and the dyes Nile red and SR101 as receptors. The findings of this research will aid in advancing the field of ALHSs. Moreover, the prepared ALHS has application potential in the field of agricultural greenhouse light‐transfer films and energy.

Two Birds with One Stone: Polymerized Thermally Activated Delayed Fluorescence Small Molecules.

Thermally activated delayed fluorescence (TADF) polymers show a great potential in low-cost, large-area and flexible full-color flat-panel displays. One of the most promising design rules is based on TADF+Linker, where a small molecular TADF unit is bonded to each other by a simple linker. Unlike the expensive vacuum deposition for small molecules, these polymerized TADF small molecules (Poly-TADF-SMs) are capable of cost-effective solution processing. Meanwhile, the good luminescent property of small molecular TADF emitters can be well inherited by Poly-TADF-SMs so as to bridge the efficiency gap between small molecules and polymers. Herein, we will highlight the recent progress of Poly-TADF-SMs, together with emphasis on their molecular design, photophysical and electroluminescence properties.

Temperature-dependent photoluminescence down to 77 K of organotin molecular rotors: eco-friendly synthesis, photophysical characterization, X-ray structures, and DFT studies.

Fluorescent organotin compounds are useful in sensing, optoelectronic devices, and in vitro bioimaging. Although in vitro fluorescence bioimaging shows low resolution at room temperature, a better resolution is possible at cryotemperatures. Therefore, the search for new cryoluminescent materials with potential application in high-resolution fluorescence bioimaging remains a great challenge. Herein, we report the cryoluminescence properties of two fluorescent bis-organotin compounds, namely, BisNTHySnBu2 (5) and BisNTHySnPh2 (6), synthesized via microwave irradiation. All compounds were fully characterized using 1H, 13C, and 119Sn NMR spectroscopy, Raman spectroscopy, IR spectroscopy, and HR-MS. The 119Sn δ and 3J(1H,119Sn) of 5 and 6 indicate that two Sn-ligands are chemically and electronically equivalent, as confirmed by cyclic voltammetry. The crystal structure of 6 showed pentacoordinate tin atoms with skeleton ligands. The study of self-assembled monolayers of both Sn-complexes via STM microscopy revealed a similar supramolecular packing in lamella-like patterns, adopting a face-on arrangement, where molecules stay flat lying on HOPG in accordance with the height profile of closely packed monolayers on graphite of about 0.33 nm thickness. However, only the Sn complex 6, which bears phenyls, covers large surface areas. The photophysical properties of bis-organotin compounds were also investigated in solution (room and low temperatures) and in the solid state. Good luminescence properties in solutions with fluorescence quantum yields (Φ) of approximately 35% and 50% were found. Despite this, Φ is quenched in the solid state because of aggregation, as supported by solvent/non solvent fluorescence studies, which is in agreement with STM and AFM investigation.

Theoretical Study on Spectrum and Luminescence Mechanism of Cy5.5 and Cy7.5 Dye Based on Density Functional Theory (DFT).

Cy5.5 and 7.5 are the most commonly used NIR 2-region fluoresceins, which have good luminescence properties and important biomedical tracer applications. In this paper, their molecular non-covalent interactions, UV-Vis absorption spectra, main bond lengths, electrostatic potential distributions, frontier molecular orbitals (HOMO and LUMO) and energy gaps were calculated by density functional theory (DFT). We found that the differences in the luminescence properties and energy gaps of Cy5.5 and Cy7.5 molecules may be caused by the length of the conjugated chains between the two aromatic rings in the molecule. By calculating the relevant molecular characteristics, this paper can provide ideas and theoretical basis for the relevant modification and application, as well as the development of new fluorescent dyes.

A new 3D Cd-MOF with 2fold interpenetrated as “turn-on/turn-off” fluorescent sensor for selective and sensitive detection of Cu2+, Al3+ and Fe3+ ions

The quantitative research with high sensitivity of metal ions has been increasingly important due to the influence to the environment and human health. In this work, a new luminescent Cd-MOF has successfully been constructed by one-dimensional spiral chain-shaped CdO6 clusters, H2O and 1-(4-carboxyphenyl)-5-methyl-4-oxo-1,4-dihydropyridazine-3-carboxylic acid ligands (H2(4-PDCA)), namely [Cd2(H2O)(4-PDCA)2]n (SNUT-19), which were further characterized by single crystal X-ray diffraction, PXRD, FT-IR and TGA. Single crystal X-ray analysis revealed that SNUT-19 exhibits unique 1D [Cd–O–Cd]∞ chain, further bridging by the ligand to form a three-dimensional (3D) structure with a 2-fold interpenetrated structure. SNUT-19 exhibits excellent water stability and good solid luminescence properties. In addition, the luminescence sensing experiments show that SNUT-19 as a fluorescent sensor for “turn on” and “turn off” luminescence sensitive detection of Cu2+, Al3+ and Fe3+ ions in aqueous media, which sensing mechanisms also have been investigated.

Lanthanide doped Cs2Ag1-xNaxBiCl6 as an efficient anti-counterfeiting and information encryption material

Luminescent anti-counterfeiting materials based on double perovskite has attracted people's attention due to its low cost, high stability, easy preparation, and environmental friendliness. However, advanced anti-counterfeiting and information encryption call for materials with multi-color emission and multimode excitation to avoid being imitated and replaced. In this study, upconversion luminescence of lanthanide Cs2Ag1-xNaxBiCl6 were investigated through adjusting the feed ratio of Ag + to Na+ and controlling the types and concentrations of the lanthanide ions. Cs2Ag0.4Na0.6BiCl6-Yb-Er emits green light under excitation at 980 and 1540 nm. Cs2Ag0.4Na0.6BiCl6-Yb-Tm and Cs2Ag0.4Na0.6BiCl6-Yb-Ho show purple and white light under excitation at 980 nm, respectively. Under excitation at 365 nm, the Cs2Ag0.4Na0.6BiCl6-Yb-Er presents yellow light, while both Cs2Ag0.4Na0.6BiCl6-Yb-Tm and Cs2Ag0.4Na0.6BiCl6-Yb-Ho exhibit orange-red light. Additionally, Yb ions doping make three samples present good near-infrared luminescent properties. At last, the high level anti-counterfeiting and information encryption applications based on lanthanide doped Cs2Ag1-xNaxBiCl6 were designed and implemented, using the characteristics of the material's luminescence properties that differ with the type of doping, excitation wavelength, and excitation power. This work indicates that lanthanide doped double perovskite has the potential to obtain more efficient anti-counterfeiting materials and information encryption materials.

Study on photoluminescence of integrated nano-calcium carbonate (CaCO3) enhanced with dysprosium (Dy) doped calcium borophosphate (CBP) phosphor

Purpose There is a strong inducement to develop new inorganic materials to substitute the current industrial pigments, which are known for their poor ultraviolet absorbent and low photoluminescence (PL) properties. The purpose of this paper is to invent a better rare-earth-based pigment material as a spectral modifier with good luminescence properties to enhance the spectral response for photovoltaic panel application. Design/methodology/approach Different phosphor samples made of nano-calcium carbonate (CaCO3) with varied wt.% of the dopant Dysprosium doped calcium borophosphate (CBP/Dy) as (W0 – 0%, W1 – 3,85%, W2 – 7.41%, W3 –10.71% and W4 –13.79%) were prepared via the solid-state diffusion method at 600 °C for 6 h using a muffle furnace. The structural, morphological and luminescence properties of the CaCO3:CBP/Dy powder samples were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and PL test. Findings The XRD, SEM and FTIR results verified the crystalline formation, morphological behaviour and vibration bonds of synthesized CBP/Dy-doped CaCO3 powder samples. XRD pattern revealed that the synthesized powder samples exhibit crystalline structured materials, and SEM results showed irregular shape and porous-like structured morphologies. FTIR spectrum shows prominent bands at 712, 874 and 1,404 cm−1, corresponding to asymmetric stretching vibrations of CO32− groups and out-of-plane bending. PL characterization of CBP/Dy-doped CaCO3 (sample W) shows emission at 427 nm (λmax) under the excitation of 358 nm. The intensity of PL emission spectra drops due to the concentration quenching effect, while the maximum PL intensity is observed in the W3 phosphor powder system. Research limitations/implications This phosphor powder is expected to find out the potential application such as a spectral modifier which is applied to match the energy of photons with solar cell bandgap to improve spectral absorption and lead to better efficiency. Originality/value The introduction of a nano-CaCO3:CBP/Dy hybrid powder system with good luminescence properties to be used as spectral modifiers for solar cell application has been synthesized in the lab, which is a novel attempt.

Enhanced luminescence stability of high-entropy dual-phase Cs(Pb1/5Mn1/5Ni1/5Zn1/5Cd1/5)Br3/Cs(Pb1/5Mn1/5Ni1/5Zn1/5Cd1/5)2Br5 perovskite nanocrystals coated with SiO2 and EVA

All-inorganic halide perovskite nanocrystals (NCs) have attracted much attention in many fields. However, the poor stability of NCs and the toxicity of Pb have greatly hindered their practical applications. Reducing the proportion of Pb with the concept of high-entropy and coating NCs with an outer layer have been regarded as effective strategies to solve the problems. Herein, We have successfully synthesized the all-inorganic high-entropy dual-phase Cs(Pb1/5Mn1/5Ni1/5Zn1/5Cd1/5)Br3/Cs(Pb1/5Mn1/5Ni1/5Zn1/5Cd1/5)2Br5(Cs‘B’Br3/Cs‘B’2Br5) perovskite NCs with good luminescence properties by a high-energy ball milling method; On the basis of which, Cs‘B’Br3/Cs‘B2’Br5 NCs are coated with SiO2 and EVA resin. Due to the amorphous SiO2 protection, the Cs‘B’Br3/Cs‘B2’Br5@SiO2 NCs maintained 93% of their emission intensity after 90 days compared to their uncoated counterparts. The PL intensity of Cs‘B’Br3/Cs‘B2’Br5 NCs /EVA was significantly enhanced by a factor of 4.7 for compared to the uncoated NCs. In addition, the PL emission intensity of the Cs‘B’Br3/Cs‘B2’Br5 NCs /EVA remained 93.7% after 90 days, and the emission peak intensity remained approximately 63% after 8 h of placement in an enclosed environment at 80% humidity through the dense polymer chains and the hydrophobic nature of the film. Finally, the film could expand its application prospects in the field of flexible device.