Tunable Luminescence Properties Research Articles

Cocrystals of naphthalene diimide with naphthalene derivatives: A facile approach to tune the luminescent properties

Naphthalene diimides are attracting considerable interest because of their tunable luminescent properties, which are generally achieved by the incorporation of electron-donating moieties into naphthalene diimides core to form donor-acceptor compounds through covalent bond. However, this method is an elaborate strategy because the separation of byproduct is tedious. Here we report that the luminescent properties of naphthalene diimides can be finely modulated by supramolecular cocrystal formation. Through the donor-acceptor interactions between the electron-deficient N,N′-di-(4-pyridyl)-1,4,5,8-naphthalene diimide (DPNDI) molecules and electron-rich naphthalene derivatives (guest), a series of cocrystal complexes are successfully fabricated. These cocrystal complexes show guest-dependent color-tunable emissions, which originate from the excited state charge transfer interactions between the DPNDI and naphthalene derivatives in the solid state. The present study anticipates providing a new method for the design of various new types of organic luminescent materials.

Tunable luminescence and energy transfer properties of MgY4Si3O13: Ce3+, Tb3+, Eu3+ phosphors

The tricolor-emitting MgY4Si3O13: Ce3+, Tb3+, Eu3+ phosphors for ultraviolet-LED have been prepared via a high-temperature solid-state method. X-ray diffraction, photoluminescence emission, excitation spectra and fluorescence lifetime were utilized to characterize the structure and the properties of synthesized samples. Two different lattice sites for Ce3+ are occupied from the host structure and the normalized PL and PLE spectra. The emissions of single-doped Ce3+/Tb3+/Eu3+ are located in blue, green and red region, respectively. The energy transfer from Ce3+ to Tb3+ and from Tb3+ to Eu3+ has been validated by spectra and decay curves and the energy transfer mode from Tb3+ to Eu3+ was calculated to be electric dipole-dipole interactions. By adjusting the content of Tb3+ and Eu3+ in MgY4Si3O13: Ce3+, Tb3+, Eu3+, the CIE coordinates can be changed from blue to green and eventually generate white light under UV excitation. All the results indicate that the MgY4Si3O13: Ce3+, Tb3+, Eu3+ phosphors are potential candidates in the application of UV-WLEDs.

Simultaneous structure and luminescence property control of barium carbonate nanocrystals through small amount of lanthanide doping

Rare earth doping has been widely applied in many functional nanomaterials with desirable properties and functions, which would have a significant effect on the growth process of the materials. However, the controlling strategy is limited into high concentration of lanthanide doping, which produces concentration quenching of the lanthanide ion luminescence with an increase in the Ln3+ concentration, resulting in lowering the fluorescence quantum yield of lanthanide ion. Herein, for the first time, we demonstrate simultaneous control of the structures and luminescence properties of BaCO3 nanocrystals via a small amount of Tb3+ doping strategy. In fact, Tb3+ would partially occupy Ba2+ sites, resulting in the changes to the structures of the BaCO3 nanocrystals, which is primarily determined by charge modulation, including the contributions from the surfaces of crystal nuclei and building blocks. These structurally modified nanocrystals exhibit tunable luminescence properties, thus emerging as potential candidates for photonic devices such as light-emitting diodes and color displays.

Structural evolution induced by substitution of designated molybdate sites (MoO4−2) with different anionic groups (BO3−3, PO4−3 and SO4−2) in CaMoO4:Sm3+ phosphors-A study on color tunable luminescent properties

A series of novel red emitting CaMoO4:Sm3+ (1.0 mol %) phosphors substituted with different anionic groups (BO3−3, PO4−3 and SO4−2) were prepared using a high temperature solid state reaction method. The effects of anionic substitution on the crystalline structure and photoluminescence (PL) properties of the CaMoO4:Sm3+, CaMoO4-BO3:Sm3+, CaMoO4-PO4:Sm3+and CaMoO4-SO4:Sm3+ phosphors were investigated. The structure, particle morphology, chemical composition, vibration modes, and PL properties of the phosphors were investigated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectrometry (FT-IR) and PL spectroscopy, respectively. The XRD patterns indicated that the crystalline structures of all the samples were consistent with the standard scheelite structure of CaMoO4. The structural parameters of the pure phase of CaMoO4:Sm3+ phosphor were obtained from the Rietveld analysis. Red PL attributed to the 4G5/2 → 6H9/2 transition of Sm3+ was observed at 646 nm when the CaMoO4:Sm3+ samples were excited by 404 nm using a monochromatized Xenon lamp. Furthermore, orange-red color tunable emission has been achieved by substitution of different anionic groups (BO3−3, PO4−3 and SO4−2) into the CaMoO4:Sm3+ phosphors. Among all the studied phosphors, the CaMoO4-SO4:Sm3+ phosphor showed the strongest PL emission compared to all other phosphors suggesting that it is a promising potential candidate for red emission in the near UV excited white LED applications.

Green approach to photoluminescent carbon dots for imaging of gram-negative bacteria Escherichia coli

Fluorescent carbon dots, zero-dimensional nanomaterials with surface ligands, have been studied extensively over the past few years in biolabelling or fluorescence-based live cell assays. In the past, synthetic organic dyes have been used as cell tracking materials, but they have severe limitations; fluorescent carbon dots may pave the way to biolabelling and cell imaging. In this work, green fluorescent carbon dots have been synthesized from a green source, gram, without any sort of covalent or ionic modifications. These gram-derived carbon dots are unique with respect to synthetic commercial cell-tracking dyes as they are non-toxic, cell internalization occurs quickly, and they have excellent bioconjugation with bacterial cells. Our aim is to establish these carbon dots in a biolabelling assay with its other physicochemical features like the tunable luminescence property, high degree of water solubility and low toxicity, towards various environments (wide range of pH, high ionic strength). Our study introduces a new perspective on the commercialization of carbon dots as a potential alternative to synthetic organic dyes for fluorescence-based cell-labelling assays.

Switchable Nonlinear Optical and Tunable Luminescent Properties Triggered by Multiple Phase Transitions in a Perovskite-Like Compound.

A new perovskite-like inorganic-organic hybrid compound [Et3(n-Pr)P][Cd(dca)3] (1) (where [Et3(n-Pr)P]+ is the propyltriethylphosphonium cation and dca is a dicyanamide ligand) was discovered to undergo three reversible phase transitions at 270 K (T1), 386 K (T2), and 415 K (T3), respectively. The variable-temperature single-crystal X-ray structural analyses reveal that these sequential phase transitions originate from the deformations of the [Cd(dca)3]- frameworks and the concomitant reorientations of the [Et3(n-Pr)P]+ guest cations. It is found that 1 possesses a sensitive nonlinear optical (NLO) switching at T2 with a large contrast of ∼40 within a narrow temperature range of ∼7 K. Furthermore, 1 shows intriguing photoluminescence (PL) property, and the PL intensity suffers a plunge near T3. The multiple phase transitions, switchable NLO and tunable luminescent properties simultaneously exist in this inorganic-organic perovskite-like hybrid compound, suggesting its great potential application in molecular switches and photoelectric field.

Yellow White to Blue White Tunable Luminescent Properties of Dy3+, Tm3+ Doped Sr2LiSiO4F Phosphors for Near-UV Light-Emitting Diodes

Yellow White to Blue White Tunable Luminescent Properties of Dy³⁺, Tm³⁺ Doped Sr₂LiSiO₄F Phosphors for Near-UV Light-Emitting Diodes

Tunable and White Light Emission of a Single-Phased Ba2Y(BO3)2Cl:Bi3+,Eu3+ Phosphor by Energy Transfer for Ultraviolet Converted White LEDs

White or tunable photoluminescence of phosphors is of great significance for their practical applications in the light-emitting diodes. In this work, Ba2Y(BO3)2Cl:Bi3+,Eu3+ phosphors were fabricated, and their photoluminescence properties were investigated. Three difference luminescence peaks located at 366, 410, and 490 nm were observed in the single Bi3+-doped Ba2Y(BO3)2Cl phosphor under the excitation of ultraviolet light attributed to three various Bi3+ sites occupied in the Ba2Y(BO3)2Cl host. By tuning the excitation wavelength from three various Bi3+ sites, the tunable luminescence properties were obtained. The energy transfer from Bi3+ at various sites to Eu3+ were observed in the Ba2Y(BO3)2Cl:Bi3+,Eu3+ phosphors by an electric dipole–dipole interaction. The tunable and white luminescence was obtained by changing the Eu3+ concentration or excitation wavelength. The light-emitting diodes with the white light emission were constructed by coupling Bi3+ and Eu3+ codoped Ba2Y(BO3)2Cl phosphors with the ...

Quantum cutting and tunable luminescence properties in Pr3+/Sm3+, Yb3+ co-doped SrMoO4 powders

Pr3+, Yb3+ and Sm3+, Yb3+ co-doped SrMoO4 phosphors have been prepared via high temperature solid-state reaction method. The quantum cutting based on Sm3+,Yb3+ couple results in a new emission band at 1000nm and the quantum cutting based on Pr3+,Yb3+ couple realizes a broad near-infrared emission of about 76nm in full width at half maximum, centered at 1000nm. Meanwhile the near infrared emission intensity for Sm3+, Yb3+ and Pr3+, Yb3+ co-doped SrMoO4 phosphors have also been increased by 2.1 and 1.8 times, with 36.5% and 9.6% energy transfer efficiencies from Sm3+ to Yb3+ and Pr3+ to Yb3+, respectively. The result provides a meaningful reference for designing broad-band near infrared phosphors or tunable near infrared laser materials.

SmF3 doping and heat treatment manipulated Ag species evaluation and efficient energy transfer from Ag nanoclusters to Sm3 + ions in oxyfluoride glass

Oxyfluoride glasses containing Ag species (including Ag+ ions, Ag nanoclusters and Ag nanoparticles) and Sm3+ ions were prepared by melt-quenching method. The structure and luminescence properties were studied by absorption spectra, transmission electron microscopy, as well as steady and time-resolved photoluminescence spectra. The experimental results indicated that the doping of SmF3 can accelerate the formation and growth of Ag nanoclusters due to the introduction of valence-variable Sm2+/3+ ions and more F-center clusters in glass host. Besides, benefitting from the size-dependent tunable luminescence properties, the Ag nanoclusters were proved to be an efficient broadband sensitizer for Sm3+ ions. Heat treatment may but not necessarily improve the photoluminescence intensity of Ag nanoclusters and Sm3+ ions, depending on the amount of Ag nanoclusters and non-luminescent Ag nanoparticles formatted in the glass host.

Tunable luminescence and energy transfer properties in Na3Bi(PO4)2:Eu3+, Tb3+, Dy3+, Sm3+ phosphors with high thermal stability

Na3Bi(PO4)2:Eu3+/Tb3+/Dy3+/Sm3+ phosphors were synthesized via a high-temperature solid-state reaction method. The X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), diffuse reflection, photoluminescence (PL) and fluorescent decay curves were utilized to characterize the obtained phosphors. Under n-UV excitation, Na3Bi(PO4)2:Eu3+/Tb3+/Dy3+/Sm3+ samples show the characteristic f-f emissions and present red, green, yellow and orange emission, respectively. When Tb3+, Dy3+ and Sm3+ were co-doped into the Na3Bi(PO4)2:Eu3+ phosphors, tunable emission colors can be obtained and can be efficiently adjusted by varying the doping ions and the doping concentration. The energy transfer mechanisms were investigated in detail and demonstrated that there is an efficient energy transfer from Tb3+, Dy3+ and Sm3+ to Eu3+ via a dipole-dipole interaction mechanism. Additional, as the temperature increases from RT to 150°C, the PL intensity of Tb3+-Eu3+, Dy3+-Eu3+ and Sm3+-Eu3+ co-doped phosphors decreased to 86%, 85% and 88%, respectively, which prove good thermal stability. All the CIE coordinates of as-prepared phosphors are displayed and show abundant colors, making these materials have potential applications for n-UV-excited white-LEDs.

Dy3+ and Eu3+ Co-doped NaGdF4 nanofibers endowed with bifunctionality of tunable multicolor luminescence and paramagnetic properties

Luminescent-magnetic bifunctional NaGdF4:Dy3+,Eu3+ nanofibers have been successfully fabricated via the combination of electrospinning followed by calcination with fluorination technique for the first time. The structure, morphologies, luminescence, and magnetic properties of the synthesized nanofibers have been characterized by a variety of techniques. X-ray diffraction (XRD) analysis shows that as-prepared NaGdF4:Dy3+,Eu3+ nanofibers are pure hexagonal structure. Scanning electron microscope (SEM) observations indicate that directly electrospinning-made PVP/[NaNO3+Gd(NO3)3+Dy(NO3)3+Eu(NO3)3] composite nanofibers have smooth surfaces, good dispersion and uniform size, and the surfaces of NaGdF4:Dy3+,Eu3+ nanofibers become rough after calcination and fluorination process. The diameters of composite nanofibers and NaGdF4:Dy3+,Eu3+ nanofibers are respectively 400.19±48.06nm and 245.90±52.10nm. NaGdF4:Dy3+,Eu3+ nanofibers exhibit predominant visible emission under 274nm ultraviolet light excitation and the trend of their color tones changes from blue, cold white, warm white to red by adjusting the molar concentration of Eu3+. In addition, all of the samples exhibit paramagnetic features and the magnetic properties of NaGdF4:Dy3+,Eu3+ nanofibers are tunable by changing the species and doping concentration of RE3+ ions. More importantly, the tunable multicolor luminescence and paramagnetic properties are simultaneously realized in single-phase NaGdF4:Dy3+,Eu3+ nanofibers, which ideally suit to apply in many fields such as solid-state lasers, lighting and displays, magnetic resonance imaging. This design conception and construction strategy developed in this work may provide some new guidance for the synthesis of other rare earth fluorides nanostructures with various morphologies.

Ethylenediamine-Assisted Hydrothermal Synthesis of NaCaSiO3OH: Controlled Morphology, Mechanism, and Luminescence Properties by Doping Eu3+/Tb3.

This paper demonstrates a facile hydrothermal method using ethylenediamine (EDA) as a "shape modifier" for the controlled synthesis of rod bunch, decanedron, spindle, flakiness, and flowerlike NaCaSiO3OH microarchitectures. The set of experimental conditions is important to obtain adjustable shape and size of NaCaSiO3OH particles, as the change in either the amount of EDA/H2O or reaction time, or the amount of NaOH. Accordingly, the crystal growth mechanism during the synthesis process is proposed, and it is found that the EDA, acting as the chelating agent and shape modifier, plays a crucial role in fine-tuning the NaCaSiO3OH morphology. Morphology evolution process of flowerlike NaCaSiO3OH as a function of NaOH is also explained in detail. Eu3+/Tb3+ doped NaCaSiO3OH samples exhibit strong red and green emission under ultraviolet excitation, corresponding to the characteristic electronic transitions of Eu3+ and Tb3+. These results imply that the morphology-tunable NaCaSiO3OH:Eu3+/Tb3+ microarchitectures with tunable luminescence properties are expected to have promising applications for micro/nano optical functional devices.

A series of highly stable isoreticular lanthanide metal-organic frameworks with tunable luminescence properties solved by rotation electron diffraction and X-ray diffraction

A series of highly stable isoreticular lanthanide metal-organic frameworks with tunable luminescence properties solved by rotation electron diffraction and X-ray diffraction

Tunable luminescence properties and energy transfer of Tm3+, Dy3+, and Eu3+ co-activated InNbO4 phosphors for warm-white-lighting

A series of Dy3+/Tm3+ singly-doped, Dy3+/Tm3+ co-doped, and Dy3+/Tm3+/Eu3+ tri-doped InNbO4 phosphors have been synthesized by a high-temperature solid-state reaction method. Powder X-ray diffraction (XRD), structure refinement, UV–visible diffuse reflectance (UV-DR) spectrum, photoluminescence excitation (PLE) and emission (PL) spectrum, decay lifetimes and CIE chromaticity coordinate were employed to understand the origins of luminescence properties for synthesized phosphors. Rare-earth activators were determined to be completely dissolved into the host lattice and occupied the 2e sites deviated from an inversion center by virtue of XRD, structure refinement and photoluminescence features. The photoluminescence excitation spectra of phosphors exhibited a broad excitation band ascribed to charge-transfer of O2−-Nb5+, ranging from 200 to 300nm, and some characteristic excitation peaks associated with energy level transition of RE ions. Under the excitation of UV light, phosphors presented characteristic emission originating from f-f transition within the 4f configuration of RE ions. With increasing Dy3+ concentration, emission colors of InNbO4:Tm3+, Dy3+ phosphors can be appropriately tuned from blue to yellow, including almost all the white light region, by means of energy transfer from Tm3+ to Dy3+. Energy transfer rates and efficiencies were calculated according to decay lifetimes and energy transfer mechanism followed a resonant type dipole-dipole interaction with critical distance of 22.23Å between Tm3+ and Dy3+. By compensating a red component of Eu3+ ion, single-component warm-white-light emitting was realized in InNbO4:Tm3+,Dy3+,Eu3+ phosphors. They might be promising candidates for color-tunable light-conversion components in the fabrication of ultraviolet-pumped warm-white-light emitting diodes (WLEDs) for solid-state lighting. Relationship of crystal structures and luminescence properties for InNbO4 and YNbO4 phosphors is as well explicated based on structural analysis.

Facile and rapid preparation of Ln3+ (Ln = Eu, Tb) doped lanthanum pyrazine-2,3,5,6-tetracarboxylate submicroparticles and their tunable luminescence properties

Novel lanthanum pyrazine-2,3,5,6-tetracarboxylate (La-PZTC) submicroparticles have been synthesized through direct precipitation method without using any surfactant or template. The crystal structure of the La-PZTC can be speculated to monoclinic system, P2(1)/c space group based on Fourier transform infrared spectroscopy, X-ray powder diffraction, Thermogravimetric analysis and elemental analysis. Time-dependent experiment was performed to explore temporal morphological evolution, indicating the nucleation and growth of the products take place in a very short time. The luminescent properties of the as-obtained lanthanum pyrazine-2,3,5,6-tetracarboxylate samples have been discussed in detail. Under UV excitation, Eu3+ or Tb3+ doped La-PZTC samples exhibit strong red and green emission, corresponding to the characteristic lines of Eu3+ or Tb3+, respectively. Interestingly, the luminescence color of phosphors can be fine-tuned from green to green-yellow, yellow, and red-orange by simply adjusting the concentrations of Eu3+ and Tb3+ ions, making the material has potential applications in building mini-optoelectronic devices and color display fields.

Hydrothermal Synthesis of Europium Activated Terbium Tungstate Phosphors: Controllable Morphologies and the Tunable Luminescent Property

AbstractPhosphors of europium activated terbium tungstate (Tb2(WO4)3:Eu3+) were successfully prepared by hydrothermal method with the subsequent calcination treatment. The precursors presented flower‐like microstructures assembled from many nanoflakes, and various morphologies were obtained by controlling the reaction parameters. Tb2(WO4)3:Eu3+ phosphors show outstanding luminescent properties with tunable emission colors under ultraviolet (UV) excitation, owing to the efficient energy transfer from WO42− to Tb3+ to Eu3+. As the doped Eu3+ content increases, the emission colors of Tb2(WO4)3:Eu3+ phosphors can be altered from green,yellow to red. Particularly, the energy transfer mechanism (WO42−→Tb3+→Eu3+) has been investigated further based on a few theoretical simulations, finding that the process mainly takes place via the dipole‐dipole interaction. Due to the efficient energy transfer in Tb2(WO4)3:Eu3+ phosphors, multicolor emissions could be achieved in a single host material by adjusting the doped Eu3+ content. The facile preparation route and the outstanding tunable luminescent properties render the materials as promising candidate phosphors applied in future color displays and light‐emitting devices.

Tunable luminescence and energy transfer properties of LiSrPO4: Ce3+, Tb3+, Mn2+ phosphors

A series of single-composition phosphors LiSrPO4: Ce3+, Tb3+, Mn2+ have been prepared via a high-temperature solid-state reaction process. X-ray diffraction (XRD), scanning electric microscopy (SEM), photoluminescence (PL) spectra, and lifetimes were utilized to characterize the samples. The luminescence properties of Ce3+ in LiSrPO4 have been discussed. The energy transfer process from Ce3+ to Tb3+/Mn2+ has been demonstrated to be a resonant type via the dipole–dipole/quadrupole-quadrupole interaction mechanism, respectively. The emissive colors of LiSrPO4: Ce3+, Tb3+, Mn2+ samples can be adjusted from blue to green and from blue to red-orange by the energy transfer of Ce3+, Tb3+ and Ce3+, Mn2+, respectively. More importantly, white emission has been obtained through adjusting the relative concentrations of Ce3+, Tb3+ and Mn2+ ions in the LiSrPO4 host under UV. It is suggested the present phosphors can be potentially applied as a candidate of single-component white-light phosphor for UV-pumped w-LED.

Study of the Discrepancies between Crystallographic Porosity and Guest Access into Cadmium-Imidazolate Frameworks and Tunable Luminescence Properties by Incorporation of Lanthanides.

An extended member of the isoreticular family of metal-imidazolate framework structures, IFP-6 (IFP=imidazolate framework Potsdam), based on cadmium metal and an in situ functionalized 2-methylimidazolate-4-amide-5-imidate linker is reported. A porous 3D framework with 1D hexagonal channels with accessible pore windows of 0.52 nm has been synthesized by using an ionic liquid (IL) linker precursor. IFP-6 shows significant gas uptake capacity only for CO2 and CH4 at elevated pressure, whereas it does not adsorb N2 , H2 , and CH4 under atmospheric conditions. IFP-6 is assumed to deteriorate at the outside of the material during the activation process. This closing of the metal-organic framework (MOF) pores is proven by positron annihilation lifetime spectroscopy (PALS), which revealed inherent crystal defects. PALS results support the conservation of the inner pores of IFP-6. IFP-6 has also been successfully loaded with luminescent trivalent lanthanide ions (Ln(III) =Tb, Eu, and Sm) in a bottom-up one-pot reaction through the in situ generation of the linker ligand and in situ incorporation of photoluminescent Ln ions into the constituting network. The results of photoluminescence investigations and powder XRD provide evidence that the Ln ions are not doped as connectivity centers into the frameworks, but are instead located within the pores of the MOFs. Under UV light irradiation, Tb@IFP-6 and Eu@IFP-6 (λexc =365 nm) exhibit observable emission changes to a greenish and reddish color, respectively, as a result of strong Ln 4 f emissions.

ChemInform Abstract: A New Series of Borophosphate Phosphor Cd3BPO7:M (M: Ce3+, Tb3+, Mn2+) with Tunable Luminescence and Energy Transfer Properties.

AbstractCd3BPO7, Cd3BPO7:xCe3+ (x = 5, 7, 9, 11 mol%), Cd3BPO7:yTb3+ (y = 2, 3, 4, 6, 8, 12 mol%), Cd3BPO7.zMn2+ (z = 0.5, 0.7, 1.15, 2 mol%), Cd3BPO7:9 mol%Ce3+,yTb3+ (y = 3, 4, 6, 8 mol%), and Cd3BPO7:9 mol%Ce3+,zMn2+ (z = 0.5, 0.7, 1.15, 2 mol%) are prepared by solid state reactions of stoichiometric amounts of CdO, H3BO3, NH4H2PO4, Tb4O7, CeF3, and MnCO3 (alumina crucible, 573—1123 K, 4—12 h).