White-light Materials Research Articles

Highly efficient white emission from UV-driven hybrid LEDs through down-conversion of arylmaleimide-based branched polymers

Single-component white light materials excited by UV have great potential in the field of white LED (WLED) for avoiding the harm of the blue chip and the self-absorption between multi-components. However, the luminous efficiency (LE) of UV-driven WLED based on single-component material is always lower than 15 lm/W. Herein, branched polymers (HPF-PMs and SPF-PMs) with different topology structures (hyperbranched and star-shaped ones) have been synthesized by employing phenylmaleimide (PM) as core unit, and oligomer of fluorene (OF) as arm unit. Both of them exhibit strong yellow emission of PM in neat films with quantum yield up to 92%, due to complete energy transfer (ET) from OF to PM. Interestingly, HPF-PMs and SPF-PMs show dual-emissive white light in silica gel films for incomplete ET. White emission of the composite films can be adjusted by changing loading amount of copolymer, and introducing a green-emissive arylmaleimide core. When the blend films applied in LEDs based on UV chip, highly efficient white electroluminescence with the LE of 16–48 lm/W, and CIE close to (0.33, 0.33) can be realized through down-conversion.

Lead Borate Glasses and Glass-Ceramics Singly Doped with Dy3+ for White LEDs.

In this paper, some series of lead borate glasses and glass ceramics singly doped with Dy3+ ions were prepared and then studied using spectroscopic techniques. Our research includes mainly studies of the luminescence properties of received materials for white light. The luminescence bands associated with the characteristic 4F9/2→6H15/2 (blue), 4F9/2→6H13/2 (yellow) and 4F9/2→6H11/2 (red) transitions of trivalent dysprosium in lead borate systems are well observed. In particular, the Commission Internationale de I’Eclairage (CIE) chromaticity coordinates (x, y) were calculated in relation to potential applications for white light-emitting diodes (W-LEDs). Their values depend on the relative B2O3/PbO ratios and PbX2 contents (where X = Cl, F, Br) in glass composition. For glass-ceramics, the chromaticity coordinates are changed significantly under different excitation wavelengths.

Atomistic Perspective on the Intrinsic White-Light Photoluminescence of Rare-Earth Free MgMoO4 Nanoparticles

Intrinsic white-light photoluminescent rare-earth free materials are promising candidates in the field of environment-friendly optical devices. They are important because white-light materials such...

Crystal structure and luminescence properties of thermally stable Sm3+-doped Sr9In(PO4)7 orange-red phosphor

A series of novel phosphate orange-red phosphor, Sr9In(PO4)7:xSm3+ (0.01 < x < 0.30), were successfully synthesized from high-temperature solid-state synthesis in this work. Their crystal structure has been analyzed by the Rietveld refinement, which shows Sr9In(PO4)7 consists of a monoclinic cell (C2/c), which also confirms the successful doping, preferential site occupancy and local ligand environment of Sm3+. Luminescence properties of the samples have been systematically investigated including excitation and emission spectra, quantum efficiency, concentration quenching, fluorescence decay and temperature-dependent luminescence properties. Photoluminescence spectra exhibited typical peaks, corresponding to 4G5/2 → 6HJ transitions of Sm3+ ions, where J = 5/2, 7/2, 9/2, and 11/2, respectively. Moreover, the concentration quenching result revealed that the optimal doping content of Sm3+ was 0.15 mol, and based on the Dexter theory, the energy transfer between Sm3+ ions was found in dipole-dipole interactions. The quantum yield of Sr9In(PO4)7:0.15Sm3+ phosphor was acceptable (58.5%). Most importantly, the emission intensity of Sr9In(PO4)7:0.15Sm3+ remains constant (>97%) below 150 °C and the configurational coordinate diagram analysis demonstrated excellent thermal stability of the Sr9In(PO4)7:Sm3+ phosphor, which is superior to that of the previously reported and commercially available phosphors. These results suggest that the Sr9In(PO4)7:Sm3+ phosphor is a promising orange-red phosphor materials for white light emitting diodes.

Effects of post-annealing on photoluminescence of Eu-doped ZnO microsphere for single-component white-light materials

The influence of post-annealing on optical properties of Eu-doped ZnO (ZnO:Eu3+) microsphere synthesized by hydrothermal method has been studied. The intrinsic deep defect emission of ZnO and the transition emission of both 5D0→7F1 and 5D0→7F2 related to Eu3+ have been observed under excitation at 325 nm. The photoluminescence (PL) spectra reveal that ZnO annealed in N2 is more favorable for Eu3+ being doped into ZnO, which is helpful to greatly enhance the red light emission of ZnO:Eu3+. Alkaline conditions are more conducive to the formation of intrinsic deep defects in ZnO lattice, but they are not so conducive to the doping of Eu3+ ions into ZnO lattice. From Gaussian deconvolution analysis of PL spectrum for ZnO:Eu3+, it can be seen that intrinsic defects of ZnO in N2 atmosphere may efficiently assist energy transfer from ZnO host to Eu3+ ions to enhance Eu3+ intrinsic red light emission. There are blue light (446 nm), green light (525 nm) and stronger red light (618 nm) which are simultaneously obtained. This work could pave a way for high performance of white light emission application.

(N-AEPz)ZnCl4]Cl: A “Green” Metal Halide Showing Highly Efficient Bluish-White-Light Emission

Benefiting from their structural flexibility and solution processability, organic-inorganic metal halide hybrids with efficient white-light emission present a great promise for solid-state lighting and display applications. However, most of these reported high-performance single-component white-light materials contain lead. Herein, we report a "green" organic zinc halide, [(N-AEPz)ZnCl4]Cl (1; N-AEPz = N-aminoethylpiperazine), exhibiting prominent bluish-white-light emission with a photoluminescence quantum efficiency as high as 11.52%. Such a value is among the highest in the reported metal halide white-light emitters. Mechanism studies disclose that the broad-band emission is ascribed to the synergistic work of organic salts and inorganic clusters. This work would incent research on single-component white-light materials for next-generation display and lighting technologies.

Ln-CPs constructed from unsymmetrical tetracarboxylic acid ligand: Tunable white-light emission and highly sensitive detection of CrO42-, Cr2O72-, MnO4- in water.

A series of isostructural lanthanide coordination polymers (Ln-CPs), [Ln(Hbptc)(H2O)4]·H2O [Ln=Er (1), Pr (2), Dy (3), Sm (4), Gd (5), Nd (6) and Tb(7); H4bptc=2,3,3',4'-biphenyl tetracarboxylic acid] have been isolated based on an unsymmetrical tetracarboxylic acid. Single-crystal X-ray diffraction analysis reveals that all CPs featured a two dimensional (2D) layer with (6, 6, 6)-connected 63 topology. Luminescent spectra demonstrate that CPs 1-7 exhibit impressive UV-visible luminescence in the solid state at room temperature. More significantly, a single-component white-light material with International Commission on Illumination (CIE) coordinates of (0.335, 0.334) for 4 (Sm-CP), very closing to the pure white-light of (0.333, 0.333) was obtained by finely tuning of the excitation wavelength. In addition, the luminescent detection for anions of 7 is investigated. Fluorescence measurements show that 7 can detect oxoanion pollutants Cr2O72-, CrO42-, and MnO4- anions in aqueous solutions with high selectivity and sensitivity, which suggests that the Tb-CP is a promising functional luminescence probe for toxic oxoanions. The possible mechanisms of the quenching effect were also discussed in detail.

Tetraphenylethylene-Decorated Metal-Organic Frameworks as Energy-Transfer Platform for the Detection of Nitro-Antibiotics and White-Light Emission.

The highly porous luminescent metal-organic frameworks (MOFs) can act as fluorescent probes for the detection of nitro compounds and can also serve as containers and energy transfer platforms to construct the host-guest systems. Herein, two new three-dimensional MOFs with high porosity were prepared successfully by the electron-rich tetrakis(4-pyridylphenyl)ethylene (tppe) as ligands. Compound 1 shows the high sensitivity and selectivity toward nitro-antibiotics in an aqueous media, particularly showing the best detection efficiency for furazolidone (FZD) among the reported luminescent sensors. The highly efficient fluorescence quenching toward FZD may be attributed to the electron and energy transfer. Compound 2 has naphthalene-2,7-dicarboxylic acid (2,7-npd) and tppe as dual linkers, and the energy transfer between 2,7-npd and tppe leads to the emission band in a large scale. It is worth noting that the single-phased white-light materials can be obtained by the in situ encapsulation of different concentration of sulforhodamine 101 (SR101) into compound 2 matrix.

Single-component warm-white-light materials with high color-rendering index based on Eu3+, Tb3+-complexes co-doped Laponite® under mild reaction conditions

Single-component white-light phosphors for UV-LED chip excitation have attracted increasing interests due to its good color stability and high color rendering index (CRI) values in solid-state lighting and display applications. However, most of such materials are prepared in harsh conditions, such as requiring extremely high temperature calcination (>1000 °C) and reductive atmosphere generally. To deal with this problem, we herein put forward a novel way to prepare the single-component white-light materials using Eu3+, Tb3+, and DPA (DPA = 2,6-Pyridinedicarboxylic acid) co-doped Laponite® through environmentally friendly preparation method (in aqueous solution) under mild reaction conditions (low calcination temperature 550 °C and air atmosphere), which exhibits a highly pure white light with good color quality (0.33, 0.34), moderate correlated color temperature value (CCT, 5544 K) and high color-rendering index value (CRI, 93).

Ln3+-Induced Diblock Copolymeric Aggregates for Fully Flexible Tunable White-Light Materials.

In this research contribution, nano-aggregates have been fabricated by introducing lanthanide (Ln3+) ions into solutions of amphiphilic diblock copolymers of polystyrene-b-poly (acrylic acid) (PS-b-PAA). The coordination of acrylic acid segments to lanthanide cations induces diblock copolymer (BCPs) self-assembly in order to design stable white luminescent hybrid nanoparticles with fine uniform particle size. The introduction of Ln3+ ions (Eu3+ and Tb3+) bestows the micelles, precisely white light, upon excitation of 342 nm. Lanthanide coordination cross-linking of poly (acrylic acid) segments, or blocks, endows the micelles higher thermal stability than that of BCPs micelles without cross-linking. As the most important key point of this work, the regular and stable nano-particles with high emission quality can make fully flexible electroluminescent devices with self-formation or uncoordinated into polymer hosts. Instead of inorganic luminescent nanoparticles with hard cores, this method can potentially apply for fully flexible white-light emitting diodes (FFWLEDs).

Novel donut-like carbon composites for the selective detection of Fe3+

The faint fluorescence of hydrothermal carbon microsphere (HTC) restricts its application in the field of luminescent materials. In this paper, novel HTC/zinc borate (4ZnO·B2O3·H2O, ZBH) (ZBH/HTCs) composites were fabricated by hydrothermal method. The as-prepared ZBH/HTCs composites have a donut-liked morphology. A large amount of oxygen-containing functional groups exist on the surface of the ZBH/HTCs composites which have been proved by Fourier Translation infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Interestingly, the ZBH/HTCs samples exhibit strong fluorescence emission. In addition, the tunable emission color provides the possibility for the preparation of white light materials. Moreover, the effects of various metal ions on the fluorescence of the ZBH/HTCs composites were investigated. The fluorescence of carbon composites shows a sensitive and selective quenching effect to Fe3+ ions, allowing it to be used as a fluorescent probe to detect Fe3+ ions with a detection limit of 49.20 nM. These results demonstrate that the ZBH/HTCs composites have great potential applications in the area of the white light-emitting diodes lighting and Fe3+ ions sensor.

Photoluminescence and semiconductor properties of two novel lanthanide-mercury compounds with one-dimensional chain-like structures

Two novel lanthanide-mercury compounds [Ln(IA)3(H2O)2]n(Hg3Cl9)n·4nH2O (Ln = Eu (1) and Tb (2); IA = isonicotinic acid) have been synthesized under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction. Both complexes exhibit one-dimensional (1D) chain-like structure with a novel isolated (Hg3Cl9)3– anion. Solid-state diffuse reflectance spectroscopy reveals the presence of wide optical band gaps of 2.81 eV and 3.47 eV, suggesting that they are potentially wide band gap organic semiconductor materials. Solid-state photoluminescence measurements uncover that they show red or green light emission bands, respectively. The emission bands can be assigned to the characteristic emission of the 4f electrons intrashell transitions of 5D0 → 7FJ (Eu3+, J = 2 and 4) and 5D4 → 7FJ (Tb3+, J = 6, 5, 4 and 3), respectively. Energy transfer mechanism is explained by the energy level diagram of Eu3+ ion, Tb3+ ion and isonicotinic acid ligand. The title compounds have remarkable CIE chromaticity coordinates of (0.6438, 0.3559) and (0.3172, 0.4773). This suggests that they may be potential candidates with red or green light emitting materials for white light emitting diodes (LEDs).

Exploring excited state hydrogen bonding interactions and proton transfer mechanism for 2,2′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(4-tert-butylphenol)

In this present work, combing density functional theory (DFT) and time-dependent DFT (TDDFT) methods, we investigate a novel white light material 2,2′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(4-tert-butylphenol) (t-HTTH) about its dual intramolecular hydrogen bonding behaviors and relative excited state intramolecular proton transfer (ESIPT) process in detail. Via testing functional and basis set, the DFT//TDDFT/MPW1PW91/6–311+G(d,p) theoretical level has been decided in three kinds of solvents (cyclohexane (CYH), dichloromethane (DCM) and toluene (Tol)), which can well reappear experimental phenomenon. Exploring molecular electrostatic potential (MEP), primary bond lengths, bond angles and infrared (IR) vibrational spectra for t-HTTH system in both S0 and S1 states, we find the double hydrogen bonds O1-H2···N3 as well as O4-H5···N6 should be strengthened in the S1 state. Investigating the photo-excitation process, we find that the S0 → S1 transition corresponds to charge transfer, which provides the driving force for ESIPT. And analyses about frontier molecular orbitals (MOs) and relative energy gaps between HOMO and LUMO orbitals, we deduced the ESIPT process may occur more likely in nonpolar solvents. Constructing potential energy curves, we reveal that the ESIPT reaction results in the dynamic equilibrium in S1 state between forward and backward processes, which facilitates white light. We not only clarify the excited state hydrogen bond dynamical behavior of t-HTTH material, but also elaborate the ESIPT mechanism and explain previous experimental phenomenon reasonably.

Preparation of Mg1+yAl2-xO4:xMn4+, yMg2+ deep red phosphor and their optical properties

Exploration of efficient deep red phosphor based on non-rare-earth ion activated oxide is of great practical value in the field of phosphors converted white light-emitting diode lighting. A spinel Mg1+yAl2-xO4:xMn4+, yMg2+ phosphor with deep red emission is synthesized by a solid-state reaction route. The crystal structure and morphology are characterized by powder X-ray diffraction and scanning electron microscopy. The luminescent performance is characterized by fluorescence spectrophotometer and fluorescence decay curves. The results demonstrate that the synthesized phosphor shows that two excited spectrum bands centered at 290 nm and 438 nm cover a broad spectral region from 220 nm to 500 nm due to the Mn4+-O2- charge transfer band and the 4A2-4T1 and 4T2 transitions of Mn4+ ions. Upon excitation at 300 nm, a strong, narrow red emission band is observed between 600 and 700 nm peaked at 652 nm as a result of the spin-forbidden 2Eg-4A2g electron transition of Mn4+. The corresponding chromaticity coordinate is (0.7256, 0.2854). Additionally, the concentration quenching of Mn4+ in the MgAl2O4 host is evaluated in detail, which indicates that the optimum doping concentration of Mn4+ is experimentally determined to be 0.14 mol%. The critical distance is calculated to be 52.15 according to the Blasse equation, which elucidates that the concentration quenching mechanism is consequently very likely to be induced by the multipole-multipole interaction. The crystal field strength (Dq) and the Racah parameters (B and C) are estimated to evaluate the nephelauxetic effect of Mn4+ suffered in MgAl2O4:Mn4+ host lattice. Luminous mechanism is explained by Tanabe-Sugano energy level diagram of Mn4+ ion. The ratio of Dq/B equals 1.74, indicating that Mn4+ ions experience a weak crystal field in the MgAl2O4 host and emission peak energy of 2Eg-4A2g transition is dependent on the nephelauxetic effect. The red emission intensity of Mg1+yAl2-xO4:xMn4+, yMg2+ increases on account of excess Mg2+ which would compensate for the local charge balance surrounding Mn4+ ions, furthermore, lead the Mn4+-Mn4+ pairs connected with interstitial O2- to transform into isolated Mn4+ ions, and thus eliminating energy transfer and enhancing the luminescence efficiency effectively. The decay times of two time-dependent curves of Mg1+yAl2-xO4:xMn4+,yMg2+ are 0.672 ms and 0.604 ms, and each entire decay curve could be well-fitted to single-exponential, confirming that there is only a single Mn4+ ion luminescence center. The decay time of Mn4+ luminescence is prolonged with the increase of Mg2+ content, indicating that excitation energy transfer and non-radiative relaxation between Mn4+-Mn4+ pairs decrease, the reason is that photoexcitation energy can be temporarily stored in the trapping centers induced by excess positive charges. These results imply that Mn4+ doped Mg1+yAl2 -xO4:xMn4+, yMg2+ is a promising candidate of deep-red phosphors for near-UV and blue light emitting diodes. These findings in the paper would be beneficial not only to developing a low-cost and safe strategy to produce high-efficient Mn4+ activated luminescent materials for white light emitting diodes, but also to providing a new insight into improving the photoluminescence properties of Mn4+.

Emission enhancement of LiLaMo2O8:Eu3+ phosphor by co-doping with Bi3+ and Sm3+ ions

A series of LiLaMo2O8:Eu3+, R (R = Bi3+ and Sm3+) phosphors are synthesized by a high temperature solid-state reaction method in air. The crystal structures, fluorescence lifetimes, and luminescence properties are investigated in detail. LiLaMo2O8:Eu3+ phosphor with excitation 395 nm shows red light in the range of 525–725 nm and it photoluminescence intensity may be enhanced ∼2.35 times due to energy transfer (ET) from a sensitizing species (Bi3+ or Sm3+) to Eu3+ ion after Bi3+ or Sm3+ ion is co-doped. The optimal Eu3+, Bi3+, and Sm3+ ion concentrations are 4%. Luminous mechanism of LiLaMo2O8:Eu3+, R (R = Bi3+ and Sm3+) phosphors and ET processes between Eu3+ and Bi3+/Sm3+ ions are analyzed and explained by their excitation and emission spectra and energy level diagrams of Eu3+, Bi3+, and Sm3+ ions. The experimental results indicate that LiLaMo2O8:Eu3+, R (R = Bi3+ and Sm3+) phosphors may be used as potenial red emitting materials for white light emitting diodes (LEDs) based on either a near ultraviolet (∼395 nm) or blue (∼465 nm) chip.

Saturated and Stable White Electroluminescence from Linear Single Polymer Systems Based on Polyfluorene and Mono-Substituted Dibenzofulvene Derivatives

The development of new electroluminescent copolymer based materials for white polymer light emitting diodes (WPLED) with special emphasis on the conceptual novelty of utilizing aggregation-induced emission enhancement (AIEE) active or dual state emitting, monosubstituted dibenzofulvene (M-DBF) derivatives 4-(5-fluoren-9-ylidenemethyl-thiophen-2-yl)-7-(4-methoxy-phenyl)-benzo[1,2,5]thiadiazole (DT) or 4-[5-(4-fluoren-9-ylidenemethyl-phenyl)-thiophen-2-yl]-7-(4-methoxy-phenyl)-benzo[1,2,5]thiadiazole (DP) as orange/red fluorophores into polyfluorene (PF) main chain is demonstrated. The mol % of these M-DBF monomer based special small π-system has been optimized as low as 0.0003, 0.0006, and 0.001% in the poly[2,7-(9,9′-dioctylfluorene)-co-4-(5-fluoren-9-ylidenemethyl-thiophen-2-yl)-7-(4-methoxy-phenyl)-benzo[1,2,5]thiadiazole (WDT) and poly[2,7-(9,9′-dioctylfluorene)-co-4-[5-(4-fluoren-9-ylidenemethyl-phenyl)-thiophen-2-yl]-7-(4-methoxy-phenyl)-benzo[1,2,5] thiadiazole (WDP) copolymers, respectively. We report the utilization of “dual emission” peaks from PFO and M-DBFs in the blue and orange region that enabled the fabrication of bias-independent WPLEDs which is fundamentally very important and highly challenging in the case of linear polymers. These copolymers showed excellent solubility in organic solvents viz. CHCl3, THF, toluene, p-xylene, etc. The synthesized copolymers were characterized by UV–vis and photoluminescence (PL) spectroscopy, and WPLEDs with ITO/PEDOT:PSS/WDP or WDT/TPBi/LiF/Al configurations were fabricated to study their electroluminescence (EL) properties. Partial energy transfer has been achieved by adjusting the PFO and DT or DP concentrations in the single polymer main chain leading to the white emission in a facile manner. The copolymers WDP-1 and WDT-1 gave saturated white emission with CIE coordinates of (0.31, 0.33) and (0.35, 0.34) at 8–14 voltages and exhibiting excellent voltage independent emission. The highest luminous efficiencies of 7.82 and 4.57 cd A–1 were achieved for WDP and WDT polymers with the highest brightness values of 9753 and 7436 cd m–2, respectively.

Introduction of Red-Green-Blue Fluorescent Dyes into a Metal-Organic Framework for Tunable White Light Emission.

The unique features of the metal-organic frameworks (MOFs), including ultrahigh porosities and surface areas, tunable pores, endow the MOFs with special utilizations as host matrices. In this work, various neutral and ionic guest dye molecules, such as fluorescent brighteners, coumarin derivatives, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM), and 4-(p-dimethylaminostyryl)-1-methylpyridinium (DSM), are encapsulated in a neutral MOF, yielding novel blue-, green-, and red-phosphors, respectively. Furthermore, this study introduces the red-, green-, and blue-emitting dyes into a MOF together for the first time, producing white-light materials with nearly ideal Commission International ed'Eclairage (CIE) coordinates, high color-rendering index values (up to 92%) and quantum yields (up to 26%), and moderate correlated color temperature values. The white light is tunable by changing the content or type of the three dye guests, or the excitation wavelength. Significantly, the introduction of blue-emitting guests in the methodology makes the available MOF host more extensive, and the final white-light output more tunable and high-quality. Such strategy can be widely adopted to design and prepare white-light-emitting materials.

Bipolar highly solid-state luminescent phenanthroimidazole derivatives as materials for blue and white organic light emitting diodes exploiting either monomer, exciplex or electroplex emission

Four phenanthroimidazole-based bipolar compounds having electron-donating carbazole or diphenylamino moieties were synthesized and characterized. All compounds form glasses and exhibit high glass transition temperatures ranging from 183 to 239 °C. Solid state blue emission was detected for all synthesized compounds and quantum yields in solid state reached 0.55. Room temperature hole and electron mobilities in the layers of phenanthroimidazole derivatives reached 3.14 × 10−4 and 5.69 × 10−4 cm2/V·s, respectively, at an electric field of 3.6 × 105 V/cm. Quantum chemical calculations on the molecular level were employed to interpret optical, photophysical and photoelectrical properties of the compounds. Due to the efficient blue solid-state emission and ambipolar charge transport the phenanthroimidazole-based derivatives were used for the preparation of non-doped emitting layers of blue OLEDs. The electroplex forming properties of the compounds were observed in a host:guest emitting layer with a commercial hole-transporting material 4,4′-cyclohexylidenebis [N,N-bis(4-methylphenyl)benzenamine]. Two most promising phenanthroimidazole-based compounds were used for the fabrication of white OLEDs which were based on both fluorescence and either electroplex or exciplex emissions. The best almost blue and white OLEDs were characterized by maximal current efficiency of 1.3 and 5.3 cd/A, power efficiency of 0.8 and 1.7 lm/W, and external quantum efficiency of 0.95 and 2.9 %.

White-light manipulation in Ho3+/Yb3+/Tm3+-doped LiNbO3 single crystals through transition metal Mn2+ ion doping

A strategy for ideal upconversion white-light emission in LiNbO3:Ho3+/Yb3+/Tm3+ single crystals is demonstrated simply through transition metal Mn2+ doping. The addition of different Mn2+ concentrations favors the probability of upconversion red emission transition, and the ratio of red-to-green is enhanced resulting in a purer upconversion white-light emission. It is observed the cross-relaxation of energy between Ho3+, Tm3+ and Mn2+ ions plays an important role in improving the red emission. The obtained results greatly benefit in the further discovery to design upconversion process and fabricate other ideal upconversion white-light materials.

Enhanced visible photoluminescent and structural properties of ZnO/KIT-6 nanoporous materials for white light emitting diode (w-LED) application

Mesoporous metal oxides ZnO are prepared by wet impregnation via hard templating synthesis method using KIT-6 mesoporous silica. The pore size of mesoporous silica with the symmetry of bicontinuous cubic Ia3d have been controlled in the range of 3.4–4.9 nm, indicating the existence of ordered within the silica walls respectively, by choosing surfactants and adjusting the temperature. The pore size of the silica template has been considered to be an important factor that determines the mesostructure of the resulting metal oxides. The prepared ZnO/KIT-6 samples have been studied by XRD, transmission electron microscope (TEM), BET surface area, and photoluminescence (PL) spectroscopy. The ZnO/KIT-6 nanocomposite has the ordered mesostructure of KIT-6 can be used as a white light emitting diode (w-LED) and ultraviolet nanolasers.