Bright Yellow Emission Research Articles

Optical properties of Sr3WO6:Dy3+ phosphors applying for white LEDs

A series of novel Sr3WO6:xDy3+ (0.01 ≤ x ≤ 0.35) yellow emitting phosphors are synthesized using the conventional high-temperature solid-state method. The phase analysis and optical properties are discussed in detail. Through the X-ray diffraction (XRD) analysis, the obtained phosphors are identified to be pure phases. The Sr3WO6:Dy3+ phosphors emit bright yellow emission light at 578 nm under 352 nm excitation, which is ascribed to the 4F9/2-6H13/2 transitions. The optimum doping concentration is 0.02 mol. The activation energy Ea is calculated to be 0.154 eV. The Commission International de L'Eclairage (CIE) coordinates and correlated color temperature (CCT) of the Sr3WO6:xDy3+ (0.01 ≤ x ≤ 0.35) is located in the yellow region. All results indicate that the Sr3WO6:Dy3+ phosphors have the potential to be applied in the white light-emitting diode (w-LED) field.

Visible-light-triggered fluorescence “turn-on” diarylethenes: Computational molecular design and photophysical studies

Fluorescence “turn-on” diarylethenes (DAEs) have emerged as promising materials for super-resolution fluorescence imaging. However, all visible-light-triggered such fluorescence “turn-on” DAEs are still rare. Herein, with the assistance of DFT and time dependent DFT theoretical calculation, we design and synthesize two visible-light triggered fluorescence “turn-on” molecules, DMAC-BTTO4 and Cz-BTTO4. The introduction of strong electron-donating 9,9-dimethyl-9,10-dihydroacridine (DMAC) and Carbazole (Cz) shifts the absorption edge of the open-isomer of control molecule Ph- BTTO4 to the visible region, thus enabling visible-light-driven cyclization. The closed isomers of DMAC-BTTO4 and Cz-BTTO4 exhibit bright yellow intramolecular charge transfer emission with a fluorescence lifetime on the nanosecond scale. Moreover, the two molecules show excellent thermal stability, fatigue resistance, and photostability. Particularly, only 10% of absorbance intensity reduction was observed for closed Cz- BTTO4 upon continuing irradiation with 405 nm light for 190 min. This work provides visible-light-triggered fluorescence “turn-on” diarylethenes with good photostability for super-resolution fluorescence imaging in biological cells.

Tunable Dual Emission in Bi3+/Te4+-Doped Cs2HfCl6 Double Perovskites for White Light-Emitting Diode Applications.

Multicolor-emission-based single-phase white light derived from different luminescence centers is an effective way to manipulate the optical properties of halide perovskites. In this work, we developed a codoping strategy to incorporate Bi3+ and Te4+ emission centers into all-inorganic lead-free Cs2HfCl6 perovskite by a hydrothermal method. The as-prepared Bi3+/Te4+-doped Cs2HfCl6 microcrystals show bright blue (Bi3+), yellow (Te4+), and warm-white emissions (Bi3+/Te4+), respectively. The broad efficient dual emission in Bi3+/Te4+ co-doped Cs2HfCl6 is assigned to the typical 3P1 → 1S0 transition emission from Bi3+ originating from [BiHf + VCl] and self-trapped excitons (STEs) from Te4+. Moreover, the concentration-optimized Cs2HfCl6:Te4+ shows excellent antiwater stability and high photoluminescence quantum yield (PLQY) of ∼70%. Meanwhile, a white light-emitting diode (WLED) fabricated using Bi3+/Te4+ co-doped Cs2HfCl6 is close to warm white with a color rendering index (CRI) of 75.4, CIE color coordinate of (0.370, 0.393), and a correlated color temperature (CCT) of 4380 K. These results suggest that Bi3+/Te4+ co-doped all-inorganic lead-free Cs2HfCl6 is a potential single-phase white light-emitting phosphor candidate for solid-state lightings.

Construction of sublimable pure organic ionic material with high solid luminescence efficiency based on anion-π+ interactions tuning strategy

Charged species with π-conjugated moieties play a vital role in the development of organic electronic field, but the executable strategy of attaining high luminescent efficiency with sublimable pure organic salts is rare due to their inherent ionic nature and low vapor pressure, extremely restricting their application in the field of organic optoelectronics via common vacuum evaporation method. In this work, a series of central-type organic salts based polycyclic aromatic hydrocarbon (PAH) core are developed because of their potential higher luminescence efficiency than that of reported terminal-type organic salts like protonated pyridine framework, and they are equipped with aggregation-induced emission enhancement performance and tunable emission. The analyses of spectral data, crystal packing, and theoretical simulation demonstrate that rationally dispersing surface charge of large π cation by regulating donor–acceptor (D-A) distribution facilitates to increase anion-π+ interactions and suppress the free rotation of phenyl groups, contributing to the fluorescence enhancement in the solid state. Notably, after tuning counter-ions’ steric hindrance and dispersed charges (BArF24−), the sublimable pure organic ionic materials are obtained with high solid luminescence efficiency, and its vacuum-evaporated organic light-emitting diode (OLED) is prepared based on pure organic salt with bright yellow emission. Such inspiring results offer us new alternative material system for the organic optoelectronics.

Metal Free Synthesis of Coumarin Containing Hetero[n]helicene like Molecules with TICT and AIE Properties

AbstractCoumarin containing hetero[n]helicene like molecules were synthesized using three component Povarov reaction followed by two dehydrogenation steps in good yields. Synthesis and photophysical properties of coumarin containing multifunctional helicene like molecules were found to be affected by substitution on pendant phenyl ring. Coumarin containing hetero[6]helicene like derivative 10 f showed bright yellow emission in solution, thin film, and solid state. Coumarin containing hetero[6]helicene like compound 13 e showed bright blue emission in solution, thin film, and solid state. The structures of intermediate compounds were confirmed by a single crystal X‐ray analysis. These structures were compared with DFT optimized structures for the helicity parameters. DFT calculations provided good correlation with observed photophysical properties of compounds 10 f and 13 e.

A fast-responsive fluorescent probe based on a styrylcoumarin dye for visualizing hydrogen sulfide in living MCF-7 cells and zebrafish.

As a vital antioxidant molecule, H2S can make an important contribution to regulating blood vessels and inhibiting apoptosis when present at an appropriate concentration. Higher levels of H2S can interfere with the physiological responses of the respiratory system and central nervous system carried out by mammalian cells. This is associated with many illnesses, such as diabetes, mental decline, cardiovascular diseases, and cancer. Therefore, the accurate measurement of H2S in organisms and the environment is of great significance for in-depth studies of the pathogenesis of related diseases. In this contribution, a new coumarin-carbazole-based fluorescent probe, COZ-DNBS, showing a rapid response and large Stokes shift was rationally devised and applied to effectively sense H2S in vivo and in vitro. Upon using the probe COZ-DNBS, the established fluorescent platform could detect H2S with excellent selectivity, showing 62-fold fluorescence enhancement, a fast-response time (<1 min), high sensitivity (38.6 nM), a large Stokes shift (173 nm), and bright-yellow emission. Importantly, the probe COZ-DNBS works well for monitoring levels of H2S in realistic samples, living MCF-7 cells, and zebrafish, showing that COZ-DNBS is a promising signaling tool for H2S detection in biosystems.

Te4+-doped zero-dimensional Cs2ZnCl4 single crystals for broadband yellow light emission

Bright broadband yellow light emission peaking at 570 nm has been successfully obtained via incorporating Te4+ ions into Cs2ZnCl4 single crystals, and this is attributed to self-trapped exciton (STE) emission from the distorted tetrahedral units.

Achieving a near-unity quantum yield from yellow emitting metal halide double perovskites toward human-centric warm white LED lighting

A novel strategy in pursuit of “human-centric” lighting for adjusting excitation to match commercial NUV-LED chips by adding Te4+ ions, producing a zero-blue radiation and showing bright broadband yellow emission with a maximum PLQY of 95.26%.

Realizing Near-Unity Quantum Efficiency of Zero-Dimensional Antimony Halides through Metal Halide Structural Modulation.

Zero-dimensional (0D) organic metal halides have attracted significant attention because of their exceptional structure tunability and excellent optical characteristics. However, controllable synthesis of a desirable configuration of metal halide species in a rational way remains a formidable challenge, and how the unique crystal structures affect the photophysical properties are not yet well understood. Here, a reasonable metal halide structural modulation strategy is proposed to realize near-unity photoluminescence quantum efficiency (PLQE) in 0D organic antimony halides. By carefully controlling the reaction conditions, both 0D (C12H28N)2SbCl5 and (C12H28N)SbCl4 with different metal halide configurations can be prepared. (C12H28N)2SbCl5 with pyramid-shaped [SbCl5]2- species exhibits yellow emission with a near-unity PLQE of 96.8%, while (C12H28N)SbCl4 with seesaw-shaped [SbCl4]- species is not emissive at room temperature. Theoretical calculations indicate that the different photophysical properties of these two crystals can be attributed to the different symmetries of their crystal structures. (C12H28N)2SbCl5 adopts a triclinic structure with P-1 symmetry, while (C12H28N)SbCl4 possesses a monoclinic structure with P21/c symmetry, which has an inversion center, and thus the optical transitions between their band-edge states give a minimal dipole intensity because of their similar parity character. In addition, we also successfully synthesized (C12H28N)2SbCl5 nanocrystals for the first time, which are particularly appealing for their solution processibility and excellent optical properties. Furthermore, (C12H28N)2SbCl5 nanocrystals flexible composite film shows bright yellow emission under β-ray excitation, suggesting a strong potential of (C12H28N)2SbCl5 for β-ray detection.

Dynamic Manipulating Space‐Resolved Persistent Luminescence in Core–Shell MOFs Heterostructures via Reversible Photochromism

AbstractPhoto‐controllable persistent luminescence at the single crystal level can be achieved by the integration of long‐lived room temperature phosphorescence (RTP) and photochromism within metal–organic frameworks (MOFs) for the first time. Moreover, the multiblock core–shell heterojunctions have been prepared utilizing the isostructural MOFs through an epitaxial growth process, in which the shell exhibits bright yellow afterglow emission that gradually disappears upon further irradiation, but the core does not show such property. Benefitting from combined persistent luminescence and photochromic behavior, a multiple encryption demo can be facilely designed based on the dynamic manipulating RTP via reversible photochromism. This work not only develops new types of dynamically photo‐controllable afterglow switch, but also provides a method to obtain MOFs‐based optical heterojunctions towards potential space/time‐resolved information encryption and anti‐counterfeiting applications.

Dynamic Manipulating Space-Resolved Persistent Luminescence in Core-Shell MOFs Heterostructures via Reversible Photochromism.

Photo-controllable persistent luminescence at the single crystal level can be achieved by the integration of long-lived room temperature phosphorescence (RTP) and photochromism within metal-organic frameworks (MOFs) for the first time. Moreover, the multiblock core-shell heterojunctions have been prepared utilizing the isostructural MOFs through an epitaxial growth process, in which the shell exhibits bright yellow afterglow emission that gradually disappears upon further irradiation, but the core does not show such property. Benefitting from combined persistent luminescence and photochromic behavior, a multiple encryption demo can be facilely designed based on the dynamic manipulating RTP via reversible photochromism. This work not only develops new types of dynamically photo-controllable afterglow switch, but also provides a method to obtain MOFs-based optical heterojunctions towards potential space/time-resolved information encryption and anti-counterfeiting applications.

Highly phosphorescent dinuclear Cu(I) complexes with iminephosphine tetradentate chelating ligand (PNNP): Structures and luminescence properties

Two dinuclear copper(I) iodide complexes [Cu(μ-I)]2L (1) and [CuIPPh3]2L (2), based on a new iminephosphine tetradentate chelating ligand (PNNP), have been synthesized and characterized. The crystal structures of the complexes display distorted tetrahedron configurations around Cu(I) centers. In powder at 298 K, these complexes exhibit bright orange-red and yellow emissions with excellent photo-luminescent quantum yields of 54.6% (1) and 66.8% (2), and short lifetimes of 2.26 μs (1) and 2.32 μs (2), respectively. The reversible mechanochromic luminescent (MCL) properties of complex 2 have been confirmed by monitoring the changes in emission spectra and X-ray diffraction patterns. X-ray crystallography analysis reveals that the unique pore structure filled with CHCl3 molecule is considered to be the origin of MCL properties of 2.

Highly Emissive and Stable Five‐Coordinated Manganese(II) Complex for X‐Ray Imaging

AbstractNowadays, the development of X‐ray imaging has promoted the demand for new‐type scintillators, among which low‐toxic manganese(II) complexes have attracted burgeoning research interest. Herein, a highly stable manganese(II) complex with peculiar five‐coordinated modes is reported, which exhibits strong yellow emission peaked at 583 nm originating from d‐d transition of Mn2+ with high photoluminescence quantum yield (PLQY) up to 93%. The five‐coordinated manganese(II) complex has been rarely reported so far which is an innovative spot in the field of photofunctional metal complex. Thanks to the high PLQY and relatively large stokes shift, the manganese(II) complex yields bright yellow emission under low‐dose X‐ray irradiation and delivers excellent linear response to X‐ray, highlighting its suitability for X‐ray contrast imaging. Based on this, highly resolved X‐ray imaging is successfully achieved that can meet the requirements of many application scenarios. In addition, this manganese(II) complex demonstrates excellent radiation hardness, humidity resistance, and heat stability, indicating the application potential of scintillators in harsh environments. This research not only provides guidance for the design and fabrication of highly luminescent manganese(II)‐based complexes, but also demonstrates the potential of manganese(II)‐based complexes as scintillators for X‐ray imaging technology.

Modulation of mechanofluorochromism based on carboxylic acid esters compounds bearing triphenylamine and pyrene with different substituents

Two new three-armed and four-armed carboxylic acid esters derivatives TPT and TBT have been developed and characterized. The two D-A type compounds (different substituents including triphenylamine and pyrene) exhibit intramolecular charge transfer (ICT) emission process from electron donor (aromatic group) to electron-withdrawing (methyl naphthoate moiety). Interestingly, it was found that TPT and TBT exhibit reversible mechanofluorochromic (MFC) properties with fluorescence color switches from initial cyan and bright yellow light to final bright yellow emissions under mechanical force stimuli. Upon the treatment of grinding, heating or exposure to organic vapor, the emission peak of TPT in as-synthesized solid powder exhibited bathochromic shift from 472 nm to 499 nm, but TBT showed hypsochromic shift from 541 nm to 498 nm, respectively. The X-ray diffraction and DSC measurements suggested that the MFC-chromism of TPT and TBT originated from the reversible different phase morphs between the crystalline (ordered accumulation) and amorphous states (disordered accumulation). The mechanochromic mechanism was given based on the spectral results. Therefore, the carboxylic acid esters derivatives might have potential applications in mechanofluorochromic materials.

One-step synthesis of nitrogen-doped multi-emission carbon dots and their fluorescent sensing in HClO and cellular imaging.

Tunable multicolor carbon dots (CDs) with a quantum yield reach up to 35% were generated directly from rhodamine and urea via one-step hydrothermal approach and purified through silica gel column chromatography. Transmission electron microscopy images reveal that the as-prepared CDs possess a small size distribution below 10nm with bright blue, green, and yellow color emission, designated as b-CDs, g-CDs, and y-CDs, respectively. The in-depth investigations reveal that the multicolor emission CDs with different fraction displays fluorescence emission wavelength ranges from 398nm (b-CDs), 525nm (g-CDs), to 553nm (y-CDs) which could be well modulated by controlling the amount of heteroatom nitrogen especially amino nitrogen onto their surface structures. Further experiments verify the important role of nitrogen content by using rhodamine solely or substituting urea with sulfur containing compounds as precursors to produce corresponding CDs since the performance is lower than that of urea incorporation. Theoretical calculation results also reveal that the increasing amount of amino nitrogen into their surface structures of b-CDs, g-CDs to y-CDs is responsible for reduced band gaps energy, which result in the redshifted wavelength. Benefiting from the excellent photoluminescence properties, wide pH variation range, high photo stability, and low toxicity, these CDs were employed for HClO sensing at 553nm within the range 5 to 140μM with a limit of detection (LOD) of 0.27 ± 0.025μM (n = 3) and multicolor cellular imaging in HeLa cells. Tunable multicolor carbon dots (CDs) were generated directly from rhodamine and urea via one-step hydrothermal approach and purified through silica gel column chromatography. The as-prepared CDs exhibit bright blue, green, and yellow color emission which could be well modulated by controlling the increasing incorporation of heteroatom nitrogen especially amino nitrogen into their surface structures. These CDs were employed for HClO sensing and demonstrated to multicolor cellular imaging in HeLa cells.

Lead-Free Halide Light-Emitting Diodes with External Quantum Efficiency Exceeding 7% Using Host–Dopant Strategy

Lead-free halide light-emitting diodes (LEDs) are fabricated using nontoxic and earth-abundant CsCu2I3 with a strong yellow emission at a peak wavelength of 568 nm. CsCu2I3-based host–dopant emitters are formed by vacuum thermal evaporation (VTE) film codeposition process instead of the commonly used solution-based film deposition process. Using the VTE process, extremely thin (30 nm) host–dopant emitters have successfully been formed with the CsCu2I3 dopant and various organic host molecules. A bright yellow emission with a photoluminescence quantum yield value of 84.8% is achieved in the 0.5% CsCu2I3-doped halide emitter film due to the successful spatial localization of charge carriers and excitons using an organic host with appropriate energy levels to CsCu2I3. With the further enhancement in charge balance using the cohost system, a record-breaking lead-free halide LED has been fabricated with an EQE of 7.4%. The lead-free halide LEDs are also highly stable in the device operation with LT70 of 20 h at 100 cd/m2.

Fluorene‐based donor‐acceptor‐type multifunctional polymer with bicarbazole pendant moiety for optoelectronic applications

AbstractSince limited examples are in the literature in which both organic light‐emitting diodes (OLEDs) and electrochromic (EC) applications were performed using the same conjugated polymer, we presented comprehensive EC and electroluminescence (EL) studies of fluorene‐based electroactive polymer (e.g., CFP6) consisting of a bicarbazole pendant moiety with quinoxaline as an acceptor bridge. CFP6 was synthesized by a Suzuki cross‐coupling polymerization reaction and utilized as an active and emissive layers of the electrochromic device (ECD) and OLED, respectively, due to its high photoluminescence quantum yield intensity and fine thin film forming capability. The optical, electrochemical, cyclic voltammetry measurements, and density functional theory calculations were realized. Electrochemical cross‐linking process was applied over the electroactive carbazole subunit of the CFP6 polymer. After the crosslinking process, EC performance was greatly improved. On the other hand, light emission and EL characteristics of OLEDs based on CFP6 emissive layer were realized in detail with six different device architectures to understand light output profile behavior. As a result, CFP6 emitted bright greenish yellow emission with a maximum brightness of 1777 cd/m2 at 215 mA/cm2 in the indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/CFP6:%10 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP)/Alq3/LiF/Al device architecture.

Solvent-controlled synthesis strategy of multicolor emission carbon dots and its applications in sensing and light-emitting devices

Carbon dots (CDs), as a new kind of carbon-based luminescent nanomaterials, have drawn widespread attention in the fields of fluorescence sensing, optoelectronic devices, and biological imaging. This work uses citric acid (CA) and Nile Blue A (NBA) as precursors. By simply changing the solvent in the reaction, their bandgaps were systematically controlled, thereby successfully obtaining bright blue, yellow and red fluorescence emission CDs (B-, Y- and RCDs). The higher quantum yield (QY) of B-, Y- and RCDs are 64%, 57% and 51%, respectively. The selected precursors and different solvents are the key to the formation of three emission CDs. Detailed characterization and density functional theory (DFT) calculations further indicate that the difference in emission color of CDs is due to the size of the sp2 conjugate domain. In addition, we used multicolor CDs as fluorescent probes to investigate their performance in detection. Among them, BCDs and YCDs can detect Sudan Red I with high selectivity and sensitivity. In the concentration range of 0 to 80 µM, the detection limits are 56 and 41 nM, respectively. Multicolor emitting phosphors and fluorescent films are also obtained by mixing CDs with other matrices. Using Ultraviolet (UV) chip as the excitation source and combining with multicolor fluorescent film and a certain proportion of B-, Y-, and RCDs/epoxy resin composites, bright monochromatic light-emitting diodes (LEDs) and white LED (WLED) with high color rendering index (CRI) were prepared. The above results indicate that the multicolor CDs prepared by us have great application potential in the fields of food safety control and optical devices.

Luminescent heteroleptic copper(I) complexes with polydentate benzotriazolyl-based ligands

Bis(benzotriazol-1-yl)phenylmethane CHPh(btz)2 and tris(benzotriazol-1-yl)methane CH(btz)3 were used as N-donor ligands to prepare luminescent heteroleptic copper(I) complexes. [Cu{CHPh(btz)2}(PPh3)2][BF4] and [Cu{CHPh(btz)2}(DPEphos)][BF4] (DPEphos = bis[(2-diphenylphosphino)phenyl] ether) were obtained from the corresponding borohydride complexes [Cu(BH4)(PPh3)2] and [Cu(BH4)(DPEphos)] and tetrafluoroboric acid. [Cu{CH(btz)3}(PPh3)][BF4] and [Cu{CH(btz)3}(PiPr3)][BF4] were prepared from the acetonitrile complex [Cu(NCCH3)4][BF4]. The complexes exhibited bright yellow or orange emissions upon excitation with near-UV and violet light. The photoluminescent properties were attributed to metal-to-ligand charge transfer transitions on the basis of experimental data and DFT calculations.

The Phase Transition and Photoluminescence Properties of (Ca9−x Sr x )Mg1.5(PO4)7:Eu2+ Solid-Solution Phosphors

A series of color-tunable (Ca9−x Sr x )Mg1.5(PO4)7:Eu2+ (0 ≤ x ≤ 9) phosphors are designed by using mineral-inspired structural design strategy and synthesized by solid-state reaction. The mineral structure β-Ca3(PO4)2-type compounds, Ca9Mg1.5(PO4)7 and Sr9Mg1.5(PO4)7 are chosen as structural prototypes. Both of them are hexagonal structure but have different space groups. The former has R3c space group, while the latter possesses R3m space group. When Ca9Mg1.5(PO4)7 compound is used as maternal materials, the powder X-ray diffraction results demonstrate that the successive substitution of Ca2+ with Sr2+ ions expands and distorts the lattice parameters and unit cell volume of Ca9Mg1.5(PO4)7 compound, rendering phase transition from the (Ca9−x Sr x )Mg1.5(PO4)7:Eu2+ (phase 1, 0 ≤ x < 3) with R3c space group to (Ca9−x Sr x )Mg1.5(PO4)7:Eu2+ (phase 2, 5 < x ≤ 9) with R3m space group. The phase transition causes noticeable spectral redshift from the original blue-violet emission of x = 0 to bright yellow emission of x = 9 sample. Importantly, at x = 1, a bright white-light emission with a full width at half maximum of ∼255 nm is discovered in Ca8SrMg1.5(PO4)7:Eu2+ phosphor, which is beneficial to achieve phosphor-converted white-light-emitting diodes with high color-rendering index. These findings indicate that the mineral-inspired structural design strategy is very helpful for the development of new phosphors.