White Light-emitting Materials Research Articles

Additive Mixing of Emissive Ligands in Covalent Organic Frameworks for White Light Emission.

Emissive covalent organic frameworks (COFs) are a promising class of crystalline materials that have demonstrated applications for sensing and light-emitting diodes. However, white light emission from a single COF has not been achieved yet as it requires multicomponent organic chromophores that simultaneously emit blue, green, and red light. In this work, we report the successful synthesis of a single COF with efficient white light emission by utilizing tunable emission properties of 2,1,3-benzothiadazole after incorporating different functional groups on its core structure, which results in the formation of three ligands, i.e., 4',4-(benzothiadiazole-4,7-diyl)-dibenzaldehyde (BTD), 4,4'-(benzoselenadiazole-4,7-diyl)-dibenzaldehyde (BSD), and 4,4'-(naphtho[2,3-c][1,2,3] selenadiazole-4,9-diyl)-dibenzaldehyde (NSD), that emit in the blue, green, and red regions of the visible light spectrum. We show that white light emission can only occur when BTD, BSD, and NSD are assembled in a single COF structure due to the facilitated energy transfer process from BTD to BSD/NSD. This work demonstrates a unique approach to developing new white light-emitting materials based on the COF structure.

Heavy-Atom Effect Regulating Room-Temperature Phosphorescence of Organic-Inorganic Zn-Based Halides for White-Light Emission.

Organic-inorganic metal halides (OIMHs) with room-temperature phosphorescence (RTP) properties have aroused great research enthusiasm as outstanding broadband white-light emitters. Current studies on OIMHs with white-light emission were achieved via self-trapped excitons (STEs), but the unclear mechanism of STE formation is not favorable for the design of materials. In this work, zero-dimensional OIMHs composed of organic 3,4,5-trimethoxybenzylamine (TBA) and zine halide were synthesized, which enhanced the ratio of the RTP emission to the fluorescence emission from the TBA ligand. The experimental and mechanistic analyses demonstrate that the manageable RTP is mainly caused by the heavy-atom effect. In particular, by adjusting the incorporation ratio of halogen, an obvious white-light emission with a chromaticity coordinate value of (0.31, 0.33) can be achieved. This work developed a method for regulating the RTP of OIMHs with the heavy-atom effect to realize white-light emission, providing a new idea for the design of white-light emission materials.

Synthesis and properties of fluorine-containing polyhedral oligomeric silsesquioxanes (POSSs) modified hyperbranched white light-emitting materials for OLEDs

Synthesis and properties of fluorine-containing polyhedral oligomeric silsesquioxanes (POSSs) modified hyperbranched white light-emitting materials for OLEDs

A novel styrylpyridine derivatives: Supramolecular assembly with cucurbit[8]uril for detection of difenzoquat, white light material and beyond

In this work, we developed a novel fluorescent molecule (SPy) that can form a supramolecular fluorescence probe with cucurbit[8]uril (Q[8]) (Q[8]@SPy) and exhibit a unique response to the herbicide difenzoquat in aqueous solution. Moreover, excellent optical properties in different solvents were shown by the fluorescence spectra of SPy. It was further shown that SPy could not only detect the water content in organic solvents, but also exhibit potential applications in the field of white-light emission materials and anti-counterfeiting.

Electrospun green-emitting La2O2CO3:Tb3+ nanofibers and La2O2CO3:Tb3+/Eu3+ nanofibers with white-light emission and color-tuned photoluminescence

Color-tuned luminescence and white-light emission materials have attracted much attention owing to their broad application prospects. Generally, Tb3+ and Eu3+ co-doped phosphors have color-tuned luminescence, but white-light emission is rarely achieved. In this work, color-tunable photoluminescence and white light emission are achieved in Tb3+ and Tb3+/Eu3+ doped monoclinic-phase La2O2CO3 one-dimensional (1D) nanofibers synthesized by electrospinning united with succedent strictly controlling calcination procedure. The prepared samples own excellent fibrous morphology. La2O2CO3:Tb3+ nanofibers are the superior green-emitting phosphors. To obtain 1D nanomaterials with color-tunable fluorescence, particularly those with white-light emission, Eu3+ ions are further selected and doped into La2O2CO3:Tb3+ nanofibers to obtain La2O2CO3:Tb3+/Eu3+ 1D nanofibers. The major emission peaks of La2O2CO3:Tb3+/Eu3+ nanofibers at 487, 543, 596 and 616 nm are attributed to 5D4→7F6 (Tb3+), 5D4→7F5 (Tb3+), 5D0→7F1 (Eu3+) and 5D0→7F2 (Eu3+) energy levels transitions under 250-nm (for Tb3+ doping) and 274-nm (for Eu3+ doping) UV light excitation, respectively. At different wavelengths excitation, La2O2CO3:Tb3+/Eu3+ nanofibers with excellent stability achieve color-tuned fluorescence and white-light emission with the help of energy transfer from Tb3+ to Eu3+ and tuning the doping concentration of Eu3+ ions. Formative mechanism and fabrication technique of La2O2CO3:Tb3+/Eu3+ nanofibers are advanced. The design concept and manufacturing technique developed in this work may offer fresh insights for synthesizing other 1D nanofibers doped with rare earth ions to tune emitting fluorescent colors.

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.

Efficient manipulation of Förster resonance energy transfer through host-guest interaction enables tunable white-light emission and devices in heterotopic bisnanohoops.

In this study, we synthesized and reported the heterotopic bisnanohoops P5-[8,10]CPPs containing cycloparaphenylenes (CPPs) and a pillar[5]arene unit, which act not only as energy donors but also as a host for binding energy acceptors. We demonstrated that a series of elegant FRET systems could be constructed successfully through self-assembly between donors P5-[8,10]CPPs and acceptors with different emissions via host-guest interaction. These FRET systems further allow us to finely adjust the donors P5-[8,10]CPPs and acceptors (BODIPY-Br and Rh-Br) for achieving multiple color-tunable emissions, particularly white-light emission. More importantly, these host-guest complexes were successfully utilized in the fabrication of white-light fluorescent films and further integrated with a 365 nm LED lamp to create white LED devices. The findings highlight a new application of carbon nanorings in white-light emission materials, beyond the common recognition of π-conjugated molecules.

Dual-emissive solid-state histidine-stabilized gold nanoclusters for applications in white-light generation.

The majority of present-day white-light emitting devices (WLEDs) are built upon the use of rare-earth elements, which have a short supply, are expensive and can become extremely toxic. Thus, in this work, we synthesized an eco-friendly, efficient and cheap white-light emitting material (WLEM) based on solid-state histidine-stabilized gold nanoclusters (His-AuNCs), obtained through the lyophilization of microwave-synthesized photoluminescent His-AuNCs. Their morphological and structural characterization was followed by thorough evaluation of their intrinsic solid-state photoluminescence properties via steady-state and time-resolved fluorescence spectroscopy and microscopy, at multiple excitation wavelengths. A white-light emission was observed under UV light excitation due to the two-band broad emission, with maxima at 475 and 520 nm, covering a large area of the visible spectrum. In order to evaluate the purity of the white-light emission we calculated the chromaticity coordinates, at different wavelengths, and displayed them on a CIE (Commision Internationale d'Eclairage) diagram. An excellent value of (0.36, 0.33) was found at 420 nm excitation, which falls within the range of pure white-light emission. Moreover, the His-AuNCs show great photo- and thermo-stability, thus proving their ability to perform as a reliable WLEM with potential use in the development of eco-friendly WLEDs.

Triple luminescent center energy transfer enables color tuning in Na3Y(PO4)2:RE3+ (RE = Tb/Eu/Tm) for w-LEDs

Single-phase host white light-emitting materials have been widely favored by researchers recently because of their advantages, such as no color reabsorption, better CRI, coordinated CCT, and pure CIE chromaticity coordinates. In this paper, a single matrix phosphor of Na3Y(PO4)2: xTb3+, yEu3+, zTm3+ was prepared by the high-temperature solid-state method, and white light emission was obtained by color regulation. The synthesized phosphor crystallizes in the Pca21 orthorhombic system, and the doping of rare-earth ions will not affect the phase composition. Firstly, the fluorescence properties of Na3Y(PO4)2: Tb3+ are studied. Tb3+ has high doping quenching concentration and shows a typical narrow-band green emission peak caused by the f-f transition. The color can be adjusted from green (0.308, 0.587) to red (0.578, 0.378) by co-doping Tb3+-Eu3+, which has the potential for application in color display LED. The mechanism of energy transfer is characterized as electric dipole-electric dipole interaction. After the blue emission of Tm3+ is introduced, light waves of different colors are emitted at different excitation wavelengths. The color coordinates of (0.338, 0.342) can be achieved in the triple luminescence center by adjusting the concentration of Tm3+, which is very close to the standard white light emission. The single-phase white-light-emitting phosphor has specific application potential in the field of w-LEDs.

Encapsulation of AIEgens within Metal–Organic Framework toward High‐Performance White Light‐Emitting Diodes

AbstractWhite light‐emitting diodes (WLEDs) have a wide range of applications in display and illumination, however, it is still challenging to achieve efficient solid‐state white light‐emitting (WLE) materials due to the conventional quenching effect. Herein, a strategy of encapsulating aggregation‐induced emission luminogens (AIEgens) into the pores of metal–organic framework (MOF) to achieve high‐performance WLED is proposed. Two cationic dyes, 2,3,4,5‐tetrakis(4‐methoxyphenyl)oxazol‐3‐ium (MOTPO) and 1‐methyl‐4‐(4‐(1,2,2‐triphenylvinyl)phenyl)pyridin‐1‐ium (TPEPy) with bright blue and yellowish green emissions, respectively, are synthesized and successfully incorporated into the pore of anionic MOF ZJU‐28. The synergy of AIE characteristics and confinement effect within hybrid material result in an enhanced emission signal in comparison to each of the individual components. The single‐phase WLE material with Commission International de L'Eclairage coordinates of (0.35, 0.34) and the quantum efficiency of 64.9% is realized by optimizing the ratio between the two guests, which is almost the best among the reported WLE MOF composites to date. The resulting WLED demonstrates the maximum external quantum efficiency of 12.67% accompanied by the excellent color‐rendering index and correlated color temperature of 86 and 4076 K, respectively. Moreover, the WLE flexible film is also achieved. This work will provide new insights and strategies for the design of efficient WLEDs in the future.

Two-step, sequential, efficient, artificial light-harvesting systems based on twisted cucurbit[14]uril for manufacturing white light emission materials

White-light-emitting (WLE) materials have promising and valuable applications in controllable lighting, screen displays and sensing. In this study, a two-step sequence of highly efficient artificial light-harvesting systems (ALHSs) with white light emission is successfully constructed in the aqueous phase through a non-covalent bond among imidazole derivatives (DIm), twisted cucurbit[14]uril (tQ[14]), eosin Y (ESY), and Nile red (NiR). The prepared linear supramolecular polymer (DIm@tQ[14]) constructed by DIm and tQ[14] through host–guest interaction is an ideal energy donor due to its superior aggregation-induced emission effect, which enables one-step energy transfer by loading ESY and two-step energy transfer by further loading NiR with a high efficiency of 91.47%. The emission color of the two-step sequential ALHSs changes from cyan to chartreuse then to orange-red, and bright white light emission can be achieved by controlling the donor/acceptor molar ratio. Moreover, the assemblies of the two-step sequential ALHSs can be applied to white LED materials. This research not only simulates the multi-step energy transfer process in nature but also has an attractive commercial value in the manufacturing of WLE materials.

Pillararene-Induced Intramolecular Through-Space Charge Transfer and Single-Molecule White-Light Emission.

The fabrication of single-molecule white-light emission (SMWLE) materials has become a highly studied topic in recent years and through-space charge transfer (TSCT) is emerging as an important concept in this field. However, the preparation of ideal TSCT-based SMWLE materials is still a big challenge. Herein, we report a bifunctional pillar[5]arene (TPCN-P5-TPA) with a linear donor-spacer-acceptor structure and aggregation-induced emission (AIE) property. The bulky pillar[5]arene between the donor and acceptor induces a twisted conformation and a non-conjugated structure, resulting in intramolecular TSCT. In addition, the AIE feature and pillar[5]arene cavity endow TPCN-P5-TPA with responsiveness to viscosity and polar guests, by which the TSCT emission is triggered. The combination of blue locally-excited state emission and yellow TSCT emission of TPCN-P5-TPA generates SMWLE. Therefore, we provide a new and versatile strategy for the construction of TSCT-based SMWLE materials.

Synthesis and Properties of Fluorine-Containing Polyhedral Oligomeric Silsesquioxanes (Posss) Modified Hyperbranched White Light-Emitting Materials for Oleds

Synthesis and Properties of Fluorine-Containing Polyhedral Oligomeric Silsesquioxanes (Posss) Modified Hyperbranched White Light-Emitting Materials for Oleds

Lanthanide-based, water-soluble, white light-emitting coordination complexes for multitarget luminescence detection

Water-based multitarget response materials have received considerable research attention. Here, by reasonably tuning the ratio of Eu, Tb, 4,4′-biphenyldicarboxylic acid (H2BPDC) and polyethyleneimine (PEI), we synthesized a water-soluble, single-wavelength-excitation, white light-emitting material and realized multitarget detection by using the change in luminescence color as a signal. The composite luminescence materials showed different luminescence colors after interacting with five different targets. In contrast to other multitarget sensing materials, this material has the advantages of simple synthesis, high integration and convenient detection procedures.

Tunable White-Light Emissions of Azapyrene Derivatives with Cucurbit[n]uril Hosts in Aqueous Solution.

Cucurbit[n]uril (CB[n])-mediated assembly of π-conjugated azapyrene derivatives with rigid aromatic rings as bridging units into optically tunable complexes is reported. Due to the hindrance of rotation of diazapyrene moieties and the enhancement of intramolecular charge transfer of chromophore guests within the cavity of the CB[8] host, color tuning including white-light emission was easily achieved by introducing CB[8] into the guest aqueous solution, therefore suggesting a feasible strategy for the creation of tunable white-light emission materials through CB[n]-based host-guest interactions.

Orange-emitting bimetallic nanoclusters combined with cyan-emitting Fe@TAOH as white light-emitting materials

White-light-emitting diodes (WLEDs) possess many merits, such as high efficiency and stability. Developing cost-effective, environmentally friendly, high-performance luminophores to achieve high-quality, full-spectrum, white lighting is of great importance to the construction and progress of WLEDs. In this work, solid-state, highly luminescent orange-emitting nanoclusters (MgCl2-Lys-Ag/Au NCs) were prepared via the salt-induced precipitation of Lys-Ag/Au NCs from solution, which showed a high absolute quantum yield of 44.5%. A cyan-emitting metal-organic framework (MOF)-like nanomaterial (named Fe@TAOH) was also prepared by the self-assembly of the coordination compound of Fe3+ and TAOH acted upon by H3PO4via H-bonding and π-π stacking interactions, which showed an emission peak at 485 nm and an absolute quantum yield of 21.7%. The potential application of the two facile-synthesis, low toxicity, and highly luminescent materials in WLEDs was investigated. The WLEDs was constructed by coating powdered Fe@TAOH and MgCl2-Lys-Ag/Au NCs samples on commercial GaN LED chip with 365 nm emissions, and it exhibited acceptable white light characteristics with a CIE color coordinates and a color rendering index (CRI) of (0.28, 0.34) and 79.6, respectively, implying good prospects in the field of WLEDs.

Facile passivation of yellow light-emitting CdSe QDs by polyethyleneimine in water to achieve bright white light emission

A bright white light-emitting material based on CdSe QDs was prepared by a facile post-synthetic treatment of passivating the QDs by hyperbranched polyethyleneimine (PEI) in water.

Supramolecular Engineering Strategy to Construct BODIPY-Based White Light Emission Materials.

Two kinds of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyads BDP-OH containing 4-hydroxystyrene groups and BDP-PY bearing pyridinyl units were prepared. In addition, a naphthalene derivative NAP-PY modified by pyridinyl moieties substituent was made. The above three dyads could be used to construct white-light emission (WLE) material by a supramolecular engineering strategy due to their three primary colors of blue, green and red. The supramolecular correlations between the hydroxyl group of BDP-OH and the pyridinyl groups of NAP-PY and BDP-PY were confirmed by 1 H NMR titration, 2D NOESY and FTIR. A fluorescence monitor application was carried out based on the realization of WLE. This work might be useful for designing other WLE supramolecular systems and image display.

Supramolecular self-assembly of an alkynylpyrene derivative and dye for modulation of white light

White light-emitting materials arouse widespread interest in optical research in recent years because of their broad application prospects in the fields of display and lighting. However, limited success on white light emission has been achieved in solution which induce it a worthy subject to study. In this article, we regulated the fluorescence color of the solution and achieved the white light emission by adjusting the concentration of the alkynylpyrene derivative 1 and the dye rhodamine-B (RhB), as well as the ratio of the mixed solvents. The results of fluorescence spectrum showed that when the concentrations of 1 and RhB are 40 μM and 50 μM, respectively, white light was achieved in 25 % water and 75 % DMSO, and the CIE coordinates were (0.33, 0.32). TEM, SEM, fluorescence spectrum, time-resolved fluorescence and other methods were used to observe the morphologies and fluorescence properties of white-light solution, exploring the self-assembly process and mechanism. We also studied the polymerization of white-light solution under 420 nm light irradiation, observed the changes of self-assembly behavior and fluorescence properties. Such white-light solution is expected to be applied to new luminescent materials.

Metal-Free White Light-Emitting Fluorescent Material Based on Simple Pillar[5]arene-tripodal Amide System and Theoretical Insights on Its Assembly and Fluorescent Properties.

The booming of host-guest assembly-based supramolecular chemistry provides abundant ways to construct functional systems and materials. Attracted by the important application prospect of white light emission and aggregation-induced emission (AIE) materials, herein, we report an efficient way for fabricating metal-free white light-emitting AIE materials through the supramolecular assembly of simple organic compounds: methoxyl pillar[5]arene (MP5) and tri-(pyridine-4-ylamido)benzene (TAP). By host-guest assembly, MP5 and TAP formed a supramolecular polymer (MP5-T); meanwhile, the MP5-T xerogel powder emitted white light at CIE coordinates (0.29 and 0.29). The supramolecular assembly and white light-emitting mechanisms were carefully investigated by experiments as well as quantum chemical calculations including density functional theory (DFT), reduced density gradient, electrostatic surface potential, independent gradient model, and frontier molecular orbital (highest-occupied molecular orbital-lowest-unoccupied molecular orbital) analyses. Interestingly, according to the experiments and calculations, the supramolecular assembly is critical in the white light-emitting phenomenon. Moreover, in this work, the quantum chemical calculations could not only support experimental phenomena but also provide deep understanding and visualized presentation of the assembly and emission mechanism. In addition, the obtained MP5-T solid powder could serve as a novel and easy means to make material for white light-emitting devices.