Cyan Emission Research Articles

A green and facile synthesis of lead-free hybrid organic-inorganic bismuth halides quantum dots for nanophotonics applications

There has been an urgent need to eliminate toxic lead from the popular halide perovskite for various photonics and optoelectronics applications. This is added by the use of dangerous and environment unfriendly chemical during the wet synthesis route. Herein we demonstrate the synthesis of lead-free halide perovskite – (PhA)BiI4 (phenylammonium tetraiodobismates) and PhABiBr4 (phenylammonium tetrabromobismates) quantum dots (QDs) in room ambient environment using eco-friendly solvent - Ethanol. FESEM-EDX analysis of PhABiI4 and PhABiBr4 confirm the 1:4 atomic ratio of Bi:I and Bi:Br. As revealed by HRTEM, the as-prepared PhABiI4 indicate the formation of QDs with sizes smaller than 10 nm. Similar morphology was observed for PhABiBr4 QDs, but smaller in size compared to PhABiI4. High optical transparency was observed, and optical bandgap was measured for both PhABiI4 and PhABiBr4 QDs at 2.25 eV for and 3.07 eV, respectively. Chromaticity studies under 365 nm irradiation reveal a bright cyan emission for the PhABiI4 and bright blue emission for the PhABiBr4 QDs. Large magnitude of nonlinear optical susceptibility, |χ(3)| were calculated in the order of 10−6 esu. The green and facile synthesis approach reported here represents an alternate avenue for the new applications of Bi-based perovskite particularly towards the next-generation nanophotonics technologies.

Visible Helicity Induction and Memory in Polyallene toward Circularly Polarized Luminescence, Helicity Discrimination, and Enantiomer Separation.

Inspired by biological helices (e.g., DNA), artificial helical polymers have attracted intense attention. However, precise synthesis of one-handed helices from achiral materials remains a formidable challenge. Herein, a series of achiral poly(biphenyl allene)s with controlled molar mass and low dispersity were prepared and induced into one-handed helices using chiral amines and alcohols. The induced one-handed helix was simultaneously memorized, even after the chiral inducer was removed. The switchable induction processes were visible to naked eye; the achiral polymers exhibited blue emission (irradiated at 365 nm), whereas the induced one-handed helices exhibited cyan emission with clear circularly polarized luminescence. The induced helices formed stable gels in various solvents with helicity discrimination ability: the same-handed helix gels were self-healing, whereas the gels of opposite-handed helicity were self-sorted. Moreover, the induced helices could separate enantiomers via enantioselective crystallization with high efficiency and switchable enantioselectivity.

Visible Helicity Induction and Memory in Polyallene toward Circularly Polarized Luminescence, Helicity Discrimination, and Enantiomer Separation

AbstractInspired by biological helices (e.g., DNA), artificial helical polymers have attracted intense attention. However, precise synthesis of one‐handed helices from achiral materials remains a formidable challenge. Herein, a series of achiral poly(biphenyl allene)s with controlled molar mass and low dispersity were prepared and induced into one‐handed helices using chiral amines and alcohols. The induced one‐handed helix was simultaneously memorized, even after the chiral inducer was removed. The switchable induction processes were visible to naked eye; the achiral polymers exhibited blue emission (irradiated at 365 nm), whereas the induced one‐handed helices exhibited cyan emission with clear circularly polarized luminescence. The induced helices formed stable gels in various solvents with helicity discrimination ability: the same‐handed helix gels were self‐healing, whereas the gels of opposite‐handed helicity were self‐sorted. Moreover, the induced helices could separate enantiomers via enantioselective crystallization with high efficiency and switchable enantioselectivity.

Strongly Confined CsPbBr3 Quantum Dots as Quantum Emitters and Building Blocks for Rhombic Superlattices.

The success of the colloidal semiconductor quantum dots (QDs) field is rooted in the precise synthetic control of QD size, shape, and composition, enabling electronically well-defined functional nanomaterials that foster fundamental science and motivate diverse fields of applications. While the exploitation of the strong confinement regime has been driving commercial and scientific interest in InP or CdSe QDs, such a regime has still not been thoroughly explored and exploited for lead-halide perovskite QDs, mainly due to a so far insufficient chemical stability and size monodispersity of perovskite QDs smaller than about 7 nm. Here, we demonstrate chemically stable strongly confined 5 nm CsPbBr3 colloidal QDs via a postsynthetic treatment employing didodecyldimethylammonium bromide ligands. The achieved high size monodispersity (7.5% ± 2.0%) and shape-uniformity enables the self-assembly of QD superlattices with exceptional long-range order, uniform thickness, an unusual rhombic packing with an obtuse angle of 104°, and narrow-band cyan emission. The enhanced chemical stability indicates the promise of strongly confined perovskite QDs for solution-processed single-photon sources, with single QDs showcasing a high single-photon purity of 73% and minimal blinking (78% "on" fraction), both at room temperature.

Dual-Color Photoluminescent Functionalized Nanoparticles for Static-Dynamic Anticounterfeiting and Encryption: First Collaboration of Spiropyran and Coumarin.

Increasing the security of anticounterfeiting materials has been the most important challenge in recent years, and the development of dual-color photoluminescent inks with multi-level security, static/dynamic emission, and dynamic color change is an important solution to overcome this problem. In this study, the multi-functionalized copolymer nanoparticles containing different functional groups (with a concentration of 20 wt %), including ester, carboxylic acid, hydroxyl, epoxide, amide, and amine groups were synthesized successfully by the emulsion polymerization method. The results showed that the particle size and morphology of nanoparticles are affected by the polarity of functional groups. The prepared multi-functionalized copolymer nanoparticles were modified physically with spiropyran (photochromic and red fluorescence emission) and coumarin (cyan emission) derivatives to develop dual-color photoluminescent polymer nanoparticles with application in static-dynamic photoluminescent anticounterfeiting inks, which have multi-level security. The investigation of optical properties indicates that the kinetics of photochromism and photoluminescence properties of samples containing spiropyran is dependent on the local polarity on the surface of polymer nanoparticles. Hence, an increase in the polarity (functionalization with amide, carboxylic acid, and hydroxyl groups) has resulted in fast photochromism, high-intensity photoluminescence emission and increased the efficiency of the photoswitchable color change of emission from cyan to pink. Dual-color photoluminescent anticounterfeiting inks were prepared by mixing polymer nanoparticles containing spiropyran with polymer nanoparticles containing coumarin, in different ratios (1:1, 1:3, 1:5, 1:8, and 1:10). Obtained results showed that prepared samples have cyan emission under UV light of 254 nm (static mode), and a dynamic photoswitching of fluorescence emission from cyan to pink (as a function of irradiation time) was also observed under UV-light irradiation of 365 nm, which is well known as a dynamic mode of emission. The responsivity and intensity of dynamic photoluminescence emission are dependent on the local polarity of the surface functional groups, in which the samples based on amide functionalized copolymer nanoparticles displayed high-intensity emission in the static mode and high-intensity photoswitchable dual-color emission in the dynamic mode, in the case of all ratios of colloid solution mixtures. Printing security tags on cellulose paper by dual-color photoluminescent inks indicates advantages such as maximum printability, resolution, brightness, and static-dynamic photoluminescence emission with high intensity for inks based on amide functionalized nanoparticles. The static-dynamic dual-color photoluminescent anticounterfeiting ink with unique properties and multi-level security was reported for the first time by the collaboration of spiropyran and coumarin. This study can open a new approach and window to the future of advanced and high-security anticounterfeiting technologies.

Deep blue, cyan, orange-red, and white multicolor emissions generated by Bi3+/Eu3+ activated KBaYSi2O7 luminescent materials for white light-emitting diodes

A variety of Bi3+ and/or Eu3+ doped KBaYSi2O7 phosphors with deep blue, cyan, orange-red, and white light multicolor emissions have been fabricated by a Pechini sol-gel (PSG) method. The KBaYSi2O7:Bi3+ phosphors exhibit an intense cyan emission or a unique narrow deep blue emission when excited by different wavelengths, which may bridge the cyan gap or act as a promising deep blue phosphor for white light-emitting diodes (WLEDs). The tunable multicolor emissions can be achieved by changing the Bi3+ doping concentrations. The Bi3+/Eu3+ co-doped KBaYSi2O7 phosphors display intrinsic emissions of Bi3+ and Eu3+ and an energy transfer process between Bi3+ and Eu3+ can be detected. The luminescence colors of KBaYSi2O7:Bi3+,Eu3+ regularly shift from blue, through cold and warm white, finally toward orange-red by adjusting the relative doping concentrations of Bi3+ and Eu3+. The single-phase white light-emitting material can be generated in both cold and warm white regions by simply varying the Eu3+ doping concentrations. Furthermore, three kinds of WLEDs devices are fabricated by KBaYSi2O7:Bi3+ or KBaYSi2O7:Bi3+,Eu3+ phosphors, which can exhibit dazzling white light emissions with eminent CIE coordinates, correlated color temperature, and color rendering index. The result offers direct evidence that the as-synthesized phosphors may be potentially applied in WLEDs and solid-state lighting.

Moisture-Induced reversible structure conversion of Zero-Dimensional organic cuprous bromide hybrids for multiple photoluminescent anti-Counterfeiting, information encryption and rewritable luminescent paper

With social development and the technology advancement, the demand for high-security photoluminescence (PL) anti-counterfeiting and information encryption materials is increasing constantly. Herein, two organic cuprous bromide hybrids, namely (TPA)CuBr2 and (TPA)2Cu4Br6, with variable coordination geometries were synthesized via a facile solution method. (TPA)CuBr2 shines bright cyan emission with a photoluminescence quantum efficiency (PLQE) of 81 % under 254 nm excitation, while (TPA)2Cu4Br6 exhibits orange emission with a PLQE of 95 % upon 365 nm irradiation. Interestingly, a reversible structural conversion could be triggered by water or heat between (TPA)CuBr2 and (TPA)2Cu4Br6, accompanied by a back-and-forth emission color change between cyan and orange under its respective excitation. The emission mechanism of above two compounds was investigated, and the results show that they stem from self-trapped excitons emission. Such PL color switching under the external stimuli of water, heat and different excitation wavelengths enables us to construct a series of anti-counterfeiting and information encryption scenarios. In addition, the rewritable PL paper based on (TPA)CuBr2 with water as ink is realized. These two compounds not only provide a good way to modulate zero-dimensional Cu(I)-based metal halide with highly efficient emission, but also a new example to develop multifunctional applications by organic–inorganic hybrid metal halides.

Highly-efficient cyan-emitting phosphor enabling high-color-quality lighting and transparent anticounterfeiting

Constructing the broad-band emitting luminescent materials with high quantum yield is of great significance towards their widespread applications. Herein, series of Eu2+ activated, whitlockite-type Ca8ZnY(PO4)7 phosphors are developed towards bifunctional platform involving the white LED and anti-counterfeiting field. Benefiting from the typical 5d-4f transitions among Eu2+ ions, the broad asymmetric cyan-emission spectra (FWHM = 78 nm) is generated under 365 nm excitation with a highest quantum yield of ∼72.11 %. The optimal doping concentration of Eu2+ ions in the Ca8ZnY(PO4)7 host is determined as 4 % and the concentration quenching mechanism is mainly attributed to a dipole–dipole interaction. Impressively, after exploiting the newly discovered cyan-emitting phosphors Ca8ZnY(PO4)7:Eu2+, the CRI value of as-prepared warm w-LED devices is remarkably enhanced from 83.9 to 90.5. Moreover, the w-LED exhibits an applicable correlated color temperature (CCT = 4176 K) and good color stability. Additionally, the transparent anticounterfeiting film is fabricated based on the highly efficient phosphors and soluble PVA, which presents anticounterfeiting performances due to their bright cyan emission upon UV light. Notably, their sustainability, excellent flexibility and foldability provide more possibilities applied for anticounterfeiting field. These results suggest the highly efficient phosphors Ca8ZnY(PO4)7:Eu2+ are promising bifunctional luminescent platforms, for both high-color-quality lighting and anticounterfeiting applications.

Augmenting cyan emission in vanadate garnets via Dy3+activation for light emitting devices and multi-mode optical thermometry.

Developing cyan-based phosphors is inevitable to bridge the cyan gap to generate white light with a high color rendering index. Herein, the blue-green emission from the VO43- center in the Sr2NaMg2V3O12 host is augmented via activating with Dy3+ ions. Dual emission from the Sr2NaMg2V3O12:Dy3+ system under 335 nm excitation is due to the energy transfer from VO43- to the Dy3+ center. An increase in the ratio of yellow to blue bands (Y/B) is noted with the increase in the concentration of Dy3+. Apart from the higher activation energy of 0.41 eV, excellent color stability with a small thermochromic shift is noted at elevated temperatures. The light emitting device fabricated based on the Sr2NaMg2V3O12:Dy3+ phosphor presents bright cyan emission with CIE coordinates of (0.250, 0.352), a CCT of 9826 K, and a CRI of 53 with stable emission even at higher input currents. The application of Sr2NaMg2V3O12:Dy3+ in multi-mode temperature sensing is also discussed. The maximum relative temperature sensitivity of 1.32, 0.41, and 1.9% K-1 at 380, 300, and 460 K is obtained for the fluorescence, fluorescence intensity ratio and excitation intensity ratio methods. Thus, the present work details the capability of Dy3+-based vanadate garnet phosphors for solid-state lighting and temperature sensing.

One-pot reaction derived multicolor nitrogen-doped graphene quantum dots for LED applications

Multicolor nitrogen-doped graphene quantum dots (NGQDs) were prepared via one-pot method and purified by column chromatography to obtain three NGQDs with different emission colors, i.e. blue emission (B-NGQDs), cyan emission (C-NGQDs), and yellow emission (Y-NGQDs). The multicolor NGQDs were combined with InGaN chip to fabricate light-emitting diode (LED) that emitted blue, cyan, and yellow light, respectively. Moreover, reducing the amount of Y-NGQDs used could construct a white LED (WLED) with color coordinate of (0.324, 0.334).

Nitrogen-doped graphene quantum dot-based portable fluorescent sensors for the sensitive detection of Fe3+ and ATP with logic gate operation.

Adenosine triphosphate (ATP) and Fe3+ are important "signaling molecules" in living organisms, and their abnormal concentrations can be used for the early diagnosis of degenerative diseases. Therefore, the development of a sensitive and accurate fluorescent sensor is essential for detecting these signaling molecules in biological matrices. Herein, nitrogen-doped graphene quantum dots (N-GQDs) with cyan fluorescence emission were prepared by thermal cleavage of graphene oxide (GO) with N,N-dimethylformamide (DMF) as a solvent. The synergistic effect of static quenching and internal filtration enabled the selective quenching of N-GQD fluorescence by Fe3+. With the introduction of ATP, Fe3+ in the N-GQDs-Fe3+ system formed a more stable complex with ATP via the Fe-O-P bond, thus restoring the fluorescence of the N-GQDs. Fe3+ and ATP were detected in the linear ranges of 0-34 μM and 0-10 μM with the limits of detection (LOD) of 2.38 nM and 1.16 nM, respectively. In addition to monitoring Fe3+ and ATP in mouse serum and urine, the proposed method was also successfully applied for cytoplasmic imaging of 4T1 cells and in vivo imaging of freshwater shrimps. Moreover, the fluorescence and solution color change-based "AND" logic gate was successfully demonstrated in the biological matrix. Importantly, a complete sensing system was constructed by combining the N-GQDs with hydrogel kits and fluorescent flexible films. Thus, the prepared N-GQDs can be expected to serve as a valuable analytical tool for monitoring Fe3+ and ATP concentrations in biological matrices.

Metal halides RbCdCl3:Sb3+ and Rb4CdCl6:Sb3+ with yellow and cyan emissions obtained via a facile hydrothermal process

Fabrication of white LEDs using both synthesized RbCdCl3:Sb3+ and Rb4CdCl6:Sb3+ crystals.

A novel bright cyan emitting phosphor of Eu2+activated Ba6BO3Cl9with robust thermal stability for full-spectrum WLED applications

A novel bright cyan-emitting phosphor of Eu2+-activated Ba6BO3Cl9with robust thermal stability has been reported. It can efficiently compensate for the lack of cyan emission and also contribute to the improvement inRaof white LED devices.

Ba3LuGa2O7.5:Bi3+ phosphors with potential application in full-spectrum WLEDs and temperature sensing

A novel n-UV activated phosphor Ba3LuGa2O7.5:Bi3+ with strong cyan emissions has been synthesized and systematically investigated.

Synergistic Effects of Surface Ligand Engineering and Double Matrices Protecting Enable Ultrastable and Highly Emissive Blue/Cyan Perovskite Nanocrystal Films for Multifunctional Applications

AbstractPerovskite nanocrystals (NCs) have attracted considerable attention because of the extraordinary optoelectronic properties, making them promising candidates for lighting and display applications. However, the emissive efficiency and stability of blue/cyan‐emitting NCs lag far behind other color emissive perovskites, which greatly restrict their practical application. Herein, a feasible strategy is proposed for synthesizing highly luminescent and stable CsPbClxBr3−x NCs by the didodecyldimethylammonium bromide (DDAB) ligand‐assisted post‐treatment. The prepared DDAB‐CsPbCl0.8Br2.2 and DDAB‐CsPbCl2.0Br1.0 NCs exhibit bright cyan and blue emission, respectively, and their quantum yields are significantly enhanced from 12.2% and 7.5% to 83.1% and 75.3% owing to the obvious decrease of surface defects by the ligand‐exchange and halogen‐compensation mechanisms. The outstanding fluorescence properties are almost remained by grafting perovskite NCs onto the surface of SiO2 nanospheres. Notably, the ultrahigh water‐stability is realized after encapsulating the composite nanospheres into polystyrene‐polyisoprene‐polystyrene (SIS) film, which is benefit from the triple protection of DDA+ cations, SiO2 nanospheres and SIS copolymers. The fabricated SiO2@DDAB‐CsPbCl2.0Br1.0/SIS film is assembled into an white light emitting diode with high color rendering index of 83.4. Importantly, the blue/cyan‐emitting films display superb temperature‐sensitivity (30–160 °C) and favorable elasticity (1200% stretch rate), indicating their promising application prospect in flexible multifunctional photoelectric devices.

Ba5GeO4Br6:Bi3+, a promising cyan phosphor for high-quality full-spectrum white light illumination

Using efficient cyan phosphors to reduce the cyan gap in the white light-emitting diode spectrum plays an important role in realizing full-spectrum white light illumination. In this work, herein, we successfully prepared a cyan phosphor Ba5GeO4Br6:Bi3+ by high-temperature solid-state method to compensate for the cyan gap in the spectrum and studied its crystal structure, luminescent properties, and thermal quenching behavior. Meanwhile, the valence state of Bi ions in the phosphor was determined by XPS spectroscopy. The Ba5GeO4Br6:Bi3+ phosphor shows strong absorption in the range of 250–400 nm, which can be attributed to the 1S0→3P1 transition of Bi3+. When excited at UV light, Ba5GeO4Br6:Bi3+ gives a bright and broad cyan emission with a half width at half maximum (FWHM) of 138 nm, and the emission peak at 491 nm. In addition, as the temperature increases, the blue shift and broadening of the spectrum can be elucidated by the nonradiative transfer and the increase of the thermally active phonon density. Finally, a full-spectrum WLED lamp with a color rendering index of 93.4 was prepared by coating Ba5GeO4Br6:Bi3+ phosphor, commercial BaMgAl10O17:Eu2+ and (Ca,Sr)AlSiN3:Eu2+ phosphors on a 310 nm UV LED chip.

Highly stable Ga-doped ZnO/polystyrene nanocomposite film with narrow-band cyan emission

In the present study, a simple method for the preparation of a luminescent flexible gallium doped zinc oxide (GZO)/polystyrene nanocomposite film was developed. The prepared GZO powder was characterized through different optical and structural techniques. The XRD study revealed the existence of a wurtzite structure with no extra oxide peaks. Elemental-mapping, EDX, FTIR and XPS analyses were used to confirm the presence of elements and the several groups present in the structure. Under excitations of UV, the prepared hybrid nanocomposite showed a strong cyan emission with narrow full width at half the maximum value (20 nm) that has not been reported before. X-ray and laser-induced luminescence results of the hybrid film revealed novel blue-green emission at room temperature. The prepared composite film showed a strong scintillation response to ionizing radiation. The strong emissions, very weak deep-level emissions, and low FWHM of composite indicate the desirable optical properties with low-density structural defects in the GZO composite structure. Therefore, the prepared hybrid film can be considered to be a suitable candidate for the fabrication of optoelectronic devices.

Enhanced cyan emission via competitive site occupancy engineering in Sr2SiO4:Eu2+ phosphor for achieving full-spectrum LED lighting

Highly efficient containing cyan-emitting phosphors are used to bridge the cyan cavity for near ultraviolet (NUV) light-emitting diodes (LEDs) to obtain high-quality full-spectrum white lighting. In this work, a series of Sr2-xNaxSi1-xNbxO4:Eu2+ (x = 0–0.25) (SNSNO:Eu2+) solid solution phosphors were prepared by a solid-state reaction method. The bright SNSNO:Eu2+ phosphors were proceeded to fill the cyan gap. Such a cosubstitution of Na + -Nb5+ ion pair improves the cyan sub-band emission peaking at around 500 nm owing to the competitive site occupancy of Eu2+ on the Sr2+ site. Notably, codoping Na+-Nb5+ ion pairs into the host can realize a tuning of spectrum of SNSNO:Eu2+ from yellow-green to cyan-green region by crystallographic site engineering. Finally, employing mixture of SNSNO:Eu2+ and commercial BAM:Eu2+ and CaAlSiN3:Eu2+ coated on a 365 nm NUV chip, a full spectrum wLED package with remarkable color rendering index (Ra = 95.1) and low CCT = 3167 K was generated. The results indicate that the SNSNO:Eu2+ phosphor is very significative on closing the cyan gap for full-spectrum white lighting.

Base‐Catalyzed Sequential 5‐exo‐dig/7‐endo‐dig Cyclization of (2‐Alkynylphenyl) Benzyl Ethers: Scope, Mechanism Studies, and Photophysical Properties

AbstractHeterocycles fused to seven‐membered rings are synthesized in a highly selective fashion from (2‐alkynylphenyl) benzyl ethers by a consecutive potassium tert‐butoxide‐catalyzed one‐pot cyclization. Systematic study to determine the ideal conditions revealed that a catalytic amount of potassium tert‐butoxide, dimethyl sulfoxide, and the tert‐BuOK/tert‐BuOH equilibrium can play a crucial role in the formation of products. The optimized reaction conditions were applied to 2‐alkynylphenyl benzyl ethers containing substituted aromatic systems directly bonded to the triple bond; however, they were ineffective for alkynes having alkyl groups. The protocol afforded the heterocycles fused to seven‐membered rings in good yields by an exclusive 5‐exo‐dig/7‐endo‐dig one‐pot sequence. The photophysical properties of compounds were investigated using absorption and emission fluorescence analyses. The emission analysis showed a blue to cyan emission. Large Stokes shift values were found for all compounds, which were attributed to the ICT state and the electronic properties of the substituents.

A zinc(II) complex based on 5-(ethylamino)isophthalic acid and trans-1,2-di(4-pyridyl)ethene with a threefold interpenetrated crystal structure: synthesis, crystal structure and room temperature phosphorescence

Abstract A coordination complex {[Zn(EtAIPA)(dpe)]·H2O} n (1), has been synthesized under hydrothermal conditions based on 5-(ethylamino)isophthalic acid (H2EtAIPA) and trans-1,2-di(4-pyridyl)ethene (dpe). The title complex was characterized by elemental analysis, UV/Vis absorption, single-crystal X-ray diffraction and emission properties. The as-prepared complex appears as a puckered 2D (4,4) network, The individual 2D nets are interlocked with each other to form a 3-fold parallel interpenetrated 2D architecture. Time-resolved measurements reveal cyan phosphorescence emission at room temperature.