Characteristic Emission Peaks Research Articles

A new organic-inorganic hybrid dimeric polyoxometalate assembled by monovacant Dawson [α2-P2W17O61]10− and Eu(III) cations

A novel organic-inorganic hybrid dimeric polyoxometalate was synthesized by the trivacancy precursor Na 12 [α-P 2 W 15 O 56 ]∙24H 2 O, which consists of dimer [{Eu(C 6 H 4 NO 2 )(H 2 O) 6 }{Eu(C 6 H 4 NO 2 ) 2 (H 2 O) 4 }{Eu(H 2 O) 3 } 2 (α 2 -P 2 W 17 O 61 ) 2 ] 11− ( 1a ), one Na + ion, eight protons and one [Eu(C 6 H 4 NO 2 )(H 2 O) 6 ] group for the charge balance, two C 6 H 5 NO 2 ligands. The decay time curve effectively demonstrates different potential energy transfer pathways triggered by different excitations, and also indicate POM components can sensitize the emission of Eu 3+ and lifetimes were prolonged. • A novel organic-inorganic hybrid dimeric POM NaH 8 [Eu(C 6 H 4 NO 2 )(H 2 O) 6 ][{Eu(C 6 H 4 NO 2 ) (H 2 O) 6 }{Eu(C 6 H 4 NO 2 ) 2 (H 2 O) 4 }{Eu(H 2 O) 3 } 2 (α 2 -P 2 W 17 O 61 ) 2 ]·(C 6 H 5 NO 2 ) 2 ·35H 2 O was prepared via the reaction of trivacancy Dawson Na 12 [α-P 2 W 15 O 56 ]∙24H 2 O and Eu 3+ cations in a acidic aqueous solution. • The UV/Vis spectrum of 1 shows four absorption band at 256, 340, 464 and 534 nm, which may originate from the pπ–dπ charge-transfer transitions of Dawson-type [α 2 -P 2 W 17 O 61 ] 10− polyoxoanions, the π−π* transition of C 6 H 5 NO 2 , and the 7F 0 –5D 2 and 7F 1 –5D 1 transitions of Eu 3+ cations, respectively. • The emission spectrum of the compound shows the characteristic emission peak of Eu 3+ at 580, 593, 614, 652, and 701 nm, which can be assigned to 5 D 0 → 7 F J (J = 0, 1, 2, 3, 4) transitions. • In addition, the decay time curve effectively demonstrates different potential energy transfer pathways triggered by different excitations, and also indicate POM components can sensitize the emission of Eu 3+ and lifetimes were prolonged. A new organic-inorganic hybrid dimeric polyoxometalate NaH 8 [Eu(C 6 H 4 NO 2 )(H 2 O) 6 ][Eu 4 (C 6 H 4 NO 2 ) 3 (H 2 O) 16 (α 2 -P 2 W 17 O 61 ) 2 ]·(C 6 H 5 NO 2 ) 2 ·35H 2 O ( 1 ) was prepared via the reaction of trivacant Dawson Na 12 [α-P 2 W 15 O 56 ]∙24H 2 O and Eu 3+ ion, which was further characterized by IR spectrum, thermogravimetric (TG) analysis, and X-ray single-crystal diffraction. Structural analysis revealed that 1 consists of an uncommon dimer [Eu 4 (C 6 H 4 NO 2 ) 3 (H 2 O) 16 (α 2 -P 2 W 17 O 61 ) 2 ] 11− ( 1a ), one [Eu(C 6 H 4 NO 2 )(H 2 O) 6 ] 2+ group, one Na + ion, eight protons for the charge balance, two C 6 H 5 NO 2 ligands and thirty-five lattice water molecules. The decay time curve effectively demonstrates different potential energy transfer pathways triggered by different excitations, and also indicate POM components can sensitize the emission of Eu 3+ and lifetimes were prolonged.

Synthesis and photoluminescence performance of single-component Ca3YAl3B4O15:Dy3+, Eu3+ white-emitting phosphor for white light-emitting diodes

A single-component Ca3YAl3B4O15 (CYAB):Dy3+, Eu3+ phosphor was synthesized by the traditional high temperature solid-phase method, Dy3+ and Eu3+ were codoped in the structure to obtain a warm white emission. The results of XRD and EDS revealed that all samples had the standard Ca3YAl3B4O15 structure, and no impurity phase appeared with codoping. The emission of Dy3+ in CYAB consisted of both main peaks at 476 nm and 570 nm, with which a white emission could be observed. Furthermore, a characteristic emission peak of Eu3+ appeared at 617 nm in Dy3+/Eu3+-codoped samples to supplement red component for the white emission of Dy3+, due to the energy transfer effect between Dy3+ and Eu3+. With the amount of Eu3+ raised, the correlated colour temperature of CYAB:Dy3+, Eu3+ phosphor obviously decreased, and a warm white light was successfully realized from the manufactured w-LEDs. Therefore, all results indicated that the single-component Dy3+/Eu3+ codoped CYAB white-emitting phosphor had a potential application in ultraviolet excited w-LEDs.

New dinuclear lanthanide complexes derived from Schiff base ligand and β-diketonate co-ligand: Synthesis, crystal structures, luminescent and magnetic properties

Six new rare earth metal complexes with the general formula [RE2(HL)2(dbm)2(CH3OH)2].2CH3OH (RE = Y (1), Tb (2), Dy (3), Ho (4), Er (5), Yb (6)) have been synthesized and constructed by Schiff base ligand and β-diketonate co-ligand. The single crystal X-ray structure study shows that 1–6 are phenoxo-O-bridged centrosymmetric dinuclear complexes and crystallize in the monoclinic P21/n space group. The near-infrared luminescent study indicates that complex 5 and 6 exhibit the characteristic emission peaks of the Er (III) and Yb (III) ions. Significantly, the emission peak of complex 5 at 1530 nm is located in the third telecommunication window of telecommunication, suggesting complex 5 has great potential application in modern telecommunication network. The alternating-current magnetic analysis reveals that the dysprosium complex exhibits single-molecule-magnet behavior under an applied dc field of 3000 Oe. In addition, the effective energy barrier of 3 is 12.45 K and pre-exponential factor is 1.08 × 10−6 s.

Preparation and Luminescence Properties of Green Li4−3xSmx(MoO4)2 Phosphors

A series of green Li4−3xSmx(MoO4)2 phosphors was prepared by a hydrothermal method. The morphology, structure and luminescence properties of the prepared powders were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and fluorescence (FL) spectroscopy. The effect of the Sm3+ content on the morphology and luminescence properties of the samples were analysed. All the microcrystalline samples were found to possess typical scheelite structures with tetragonal symmetry. This type of phosphor was effectively excited by blue light (450 nm) and emitted most strongly at 568 nm, i.e., green light with high brightness. With increasing x, the intensities of the two characteristic emission peaks of Sm3+ (at 568 nm and 664 nm) in the samples first increased, reaching a maximum at x = 0.6, and then decreased.

Wet chemical synthesis of BiPO4 :Eu3+ phosphor for w-LED application.

The synthesis of BiPO4 :Eu3+ phosphors has been achieved via a wet chemical process. X-ray diffraction patterns show that the phase of the as-prepared samples matches very well with the standard BiPO4 structure. At 395 nm, the highest excitation intensity was observed. Following 395 nm excitation, two characteristic emission peaks at 592 nm and 616 nm were shown. At 0.5mol% of Eu3+ ions, concentration quenching occurred. The particle size is within the micrometre range, according to the scanning electron microscope magnification. The chromaticity coordinates for wavelengths 592 nm and 616 nm are (x = 0.586, y = 0.412) and (x = 0.682, y = 0.317), respectively. The findings imply that the prepared phosphor may be used to create white light-emitting diodes.

Improvement of physical and electrochemical properties of Cu2O thin films with Fe ions doping towards optoelectronic applications

Pure and doped Cu2O thin films were deposited on FTO substrate with various Fe dopant concentrations employing low-cost electrodeposition technique. All thin films were successfully characterized employing XRD, SEM, PL spectroscopy, UV–vis spectrophotometer, and photocurrent measurement. XRD results indicate the formation of cubic structure of thin films where all grown grains were well oriented along (111) diffraction plane at different dopant concentrations. The crystal size of doped Cu2O thin films was calculated from the Scherrer equation were the values range from 24.95 to 31.75 nm. The creation of grains similar pyramid-shaped for grown thin films is proven by SEM results. PL results reveal the characteristic emission peaks of Cu2O thin films at 521 and 704 nm which are attributed to the inter-band transitions and Cu vacancies or O interstitial, respectively. Moreover, PL intensity changed with doping process due to the integration of Fe3+ ions in interstitial positions or/and Cu sites. The optical measurements indicate that thin films have optical absorption edge which located between 490 and 550 nm that attributed to Cu2O band gap. The estimated Eg for pure and doped Cu2O thin films was founded to be in the range from 2.1 to 2.59 eV. The photocurrent measurements signal that electrodeposited Cu2O films are p-type semiconductors. Furthermore, the doping process enhancement the photocurrent where more visible light could be more captured and therefore improvement of electron-hole production. The results show that Fe doped Cu2O thin films are talented candidate for the optoelectronic applications such as sensors and solar cells.

Observation of up conversion/ down conversion luminescence and structural analysis of La2Zr2O7: Pr3+ nano phosphors

Charge transfer band (CTB) transition significantly improves the photoluminescence properties of phosphor materials due to its higher absorption efficiency than the characteristic excitations of rare-earth ions. La2Zr2O7 (LZO): Pr3+ phosphors with varying doping concentrations of Pr3+ were synthesized through the hydrothermal method. The formation of the pure pyrochlore phase was confirmed from powder X-ray diffraction (XRD). The structural analysis was performed from Rietveld refinement of the XRD data. Field emission electron microscope (FESM) equipped with EDX spectroscopy was used to study the surface morphology and elemental compositions. X-ray photoelectron spectroscopy (XPS) analysis of the optimized sample provides the bonding state of the compositions. Under 257 nm CTB excitation, the photoluminescence emission spectra (PL) exhibit all the characteristic emission peaks of Pr3+ ion. The transitions involved in the excitation and emission process have been shown in the energy level diagram of Pr3+ ions. The Concentration quenching effect was explained from Bless relation and Dexter energy transfer theory between activator ions. Decay curves of the prepared phosphors show bi-exponential behavior. The up-conversion emission spectra were recorded under 980 nm laser excitation. The optical transition in the UV–Vis range was investigated based on the diffuse reflectance spectra, and the results match well with the excitation spectra. The photometric study informs the color and the quality of the emitted light. The outcomes produce a new synthesis method to prepare La2Zr2O7:Pr3+ nano phosphor that can be an excellent candidate for solid-state lighting and UV/NIR to the visible converter in solar cell applications.

Photoluminescence characteristics of Ln3+-doped phosphors derived from sustainable resources for solid state lightning applications

Di-calcium silicate (Ca2SiO4) phosphors doped with series of Ln3+ ions have been prepared by using high temperature solid-state reaction technique. The required raw chemicals of CaO from egg shell and SiO2 from rice husk powders have been used instead of chemicals which were derived from non-renewable minerals. The structural, morphological and photoluminescence characteristics were studied through XRD, SEM and FLS 980 spectrometer measurements, respectively. The XRD patterns of all the phosphors are fit well with the established ICDD card No.01–083–0464 with monoclinic crystal structure. Photoluminescence spectra of Ce3+, Pr3+, Sm3+, Eu3+, Tb3+, Dy3+ and Er3+-doped phosphors exhibit characteristic sharp intense emission peaks at 385 (d-f), 606 (1D2→3H4), 600 (4G5/2→6H7/2), 703 (5D0→7F4), 544 (5D4→7F5), 573 (4F9/2→6H13/2) and 545 nm (4S3/2→4I15/2), respectively. Emission characteristics of developed phosphors such as CIE co-ordinates, correlated colour temperature, colour purity, lifetimes of fluorescent level, etc., of Ln3+ have been quantified. The decay curves for lower concentrations of Ln3+ ion exhibit single exponential behaviour and turns into bi-exponential behaviour accompanied with shortening in lifetime for higher concentrations. These results have been discussed with reported values and found to be better than many of the reported phosphors derived from non-renewable minerals. Therefore, Ca2SiO4:Ln3+ phosphors could also be useful to design and develop low-cost solid state lightning devices besides effective utilization of renewable agricultural and food waste materials.

Photochromic tuning and scintillation properties of Tb3+/Eu3+ co-doped calcium gadolinium zinc borosilicate glass

Tb3+/Eu3+ co-doped Al2O3-B2O3-SiO2-CaO-Gd2O3-ZnO (ABS-CGZ) borosilicate glass with high transmittance (∼ 80%) and density (4.2∼4.3 g/cm3) were produced by melt-quenching method, and their luminescence and scintillation characteristics were investigated. X-ray diffraction (XRD) of prepared glass exhibited long-range disordered interior structures. As the concentration of Eu3+ ions increased, there were variations in the characteristic emission peak intensities and the decay times of Tb3+ and Eu3+ ions, suggesting energy transfer from Tb3+ to Eu3+ ions. Furthermore, the integrated scintillation efficiency of the glass (Eu3+, 0.8mol%) reached 40% of the commercial Bi4Ge3O12 (BGO) crystal, indicating that co-doped glass possessed excellent scintillation properties. Moreover, the glass exhibited typical green and red emissions at excitation wavelength of 378 and 395 nm, and the color tuning of green to red light emission was observed with variation in Eu3+ ions doping concentration. The application range of borosilicate glass is further expanded based on the findings of this study.

Low temperature-synthesized MgAl2 O4 :Eu3+ nanophosphors and their structural validations using density functional theory: photoluminescence, photocatalytic, and electrochemical properties for multifunctional applications.

A low temperature-assisted and oxalyl dihydrazide fuel-induced combustion synthesized series of uncalcined MgAl2 O4 :Eu3+ nanophosphors showed an average crystallite size of ~20 nm, and bandgap energy (Eg ) of 4.50-5.15 eV, and were validated using density functional theory and found to match closely with the experimental values. The photoluminescence characteristic emission peaks of Eu3+ ions were recorded between 480 and 680 nm. The nanophosphors excited at 392 nm showed f-f transitions assigned as 5 D0 →7 FJ (J = 0, 1, 2, and 3). The optimized MgAl2 O4 phosphors had Commission Internationale de l'Eclairage coordinates in the red region, a correlated colour temperature of 2060 K, and a colour purity of 98.83%. The estimated luminescence quantum efficiency ( ) was observed to be ~63% using Judd-Ofelt analysis. Electrochemical and photocatalytic performance were explored and indicated its multifunctional applications. Therefore, MgAl2 O4 :Eu3+ nanophosphors could be used for the fabrication of light-emitting diodes, industrial dye degradation, and as electrodes for supercapacitor applications.

Investigations into spectroscopic and optoelectronic behaviour of furoic acid-based Eu(III) complexes for advanced photonic applications.

To illuminate the zone of organic light-emitting diodes, a novel series of four red luminescent europium complexes, one binary (C1) and three ternary (C2-C4), of 5-phenyl 2-furoic acid was synthesized with 2,2'-bipyridyl (bipy), bathophenanthroline (batho) and 1,10-phenanthroline (phen) as ancillary ligands and characterized by adopting various analytical techniques. All the findings of energy-dispersive X-ray spectroscopy, elemental (CHN) analysis, Fourier transform infrared, nuclear magnetic resonance, and ultraviolet-visible spectroscopy confirmed the coordination of ligand binding sites with the europium ion. To evaluate the thermal stability, thermogravimetric/difference thermogravimetric measurements were taken that revealed that the synthesized complexes were stable up to 245°C. Diffused reflectance studies indicated that these complexes had potential for their use in wide band-gap semiconductors, as all the four complexes showed metal-centred luminescence as a characteristic red emission peak that was observed at 613 nm under the excitation wavelength of 330 nm. The internal quantum efficiencies and luminescence lifetime of complexes were predicted using Judd-Ofelt and photophysical data. The monoexponential luminescence decay and Judd-Ofelt analysis suggested the presence of a single and asymmetric chemical environment in the coordination sphere of the europium metal. Commission International de l'Eclairage colour coordinates, correlated colour temperature values, and colour purity of the complexes validated their red emission in the visible region.

Green emanating BiOCl:Tb3+ phosphors for strategic development of dermatoglyphics and anti-counterfeiting applications

• Green emitting BiOCl:xTb 3+ (x = 1–9 mol%) nanophosphors are prepared by propellant solution combustion route. • A new fluorescence based platform has been setup for in-situ visualization of latent fingerprints and lip prints by powder dusting method. • Well defined fluorescence fingerprint images on variety of surfaces by revealing type 1–3 ridge characteristics. • Developed latent fingerprints shows superior contrast, sensitivity, efficiency, selectivity and negligible background hindrance. • Fabricated unclonable invisible security ink and make it highly suitable for brush mode. In this work, we reported green emitting Tb 3+ ions (1–9 mol%) doped BiOCl nanophophors (NPs) synthesized by solution combustion route using Mimosa pudica ( M. p. ) plant extract as a bio-fuel. Powder X-ray diffraction (PXRD) patterns exhibit tetragonal structure of matlockite-type P4/nmm space group. Scanning electron microscopy (SEM) reveals that the prepared NPs were shown flake-like morphology. The energy bandgap of BiOCl:Tb 3+ (1–9 mol%) NPs were estimated and found to be in the range ∼3.50–3.53 eV. The photoluminescence (PL) spectra show characteristic emission peaks at ∼489, 545, 591 and 622 nm, which were corresponding to 5 D 4 → 7 F 6, 5 D 4 → 7 F 5 , 5 D 4 → 7 F 4 and 5 D 4 → 7 F 3 transitions of Tb 3+ ions, respectively. The maximum PL intensity was found to be for 5 mol% doped NPs and later diminishes. The diminished PL intensity was mainly ascribed to concentration quenching. The estimated CIE (Commission International de I’Eclairage) co-ordinates were close to the green emission standard values set by the National Television System Committee. The optimized NPs was used for development and visualization of latent fingerprints (LFPs) and lip prints. The developed fingerprints and lips prints revealed level I-III ridge details with high sensitivity, selectivity and without any background hindrance. The developed anti-counterfeiting labels were encrypted only under UV light illumination, but were completely invisible under normal light. These results clearly demonstrated that the optimized NPs can help to narrow the search gap in criminal investigations and forensic purposes.

Design of Dinuclear Lanthanide Complexes from N2O2 Donor Ligand for Single Molecule Magnets: Crystalline Architecture and Slow Magnetic Relaxation Studies

AbstractThree new dinuclear lanthanide complexes [Ln2L2(μ2‐benzoate)2(MeOH)2] ⋅ 4MeOH (H2L=2‐Bis(2‐hydroxybenzyl)aminomethyl]pyridine); Ln=Nd (1), Tb (2), Dy (3)) have been synthesized and structurally characterized by single‐crystal X‐ray diffraction analyses. Compounds 1, 2 and 3 are isomorphous and thus the framework connectivity features are the same for all the three compounds. In the dimeric form of the complexes, each metal centre is octacoordinated with square antiprism (D4d symmetry) geometry, which is completed by a coordinated methanol molecule. In addition, the methanol that present in the structural voids also acts as linkers of paddle‐wheel like complexes. Magnetic properties of the compounds have been investigated in detail using direct‐current and alternating‐current susceptibility measurements. From the analysis of all three complexes, the decrease of susceptibility value at low temperatures is due to the depopulation of Stark sublevels and the existence of intramolecular antiferromagnetic interactions. In addition, complex 3 shows slow relaxation of magnetization behavior, a characteristic feature of single molecule magnets (SMMs). An effective energy barrier value (Ueff) of 38.87 K and relaxation time (τ0) of 1.665×10−7 s for the magnetic relaxation process was obtained for 3. Solid state luminescence spectra for complex 2 show characteristic green emission peaks at 543 nm region having potential for applications in the solid state as light emitting diodes and photoluminescent materials.

Surface chemistry modification of core-shell structured SiO2@LaOF:Eu3+/Li+ nanophosphors for advanced forensic applications

The fabrication of core–shell structured SiO 2 @LaOF:Eu 3+ , Li + nanophosphors and its surface functionalization with oleic acid (OA) by an ultrasonication route are reported. The X-ray diffraction profiles were well indexed to the tetragonal phase of LaOF. The energy band gap of the prepared samples was found in the range ∼4.32–4.21 eV. The morphological studies evidenced the spherical core–shell structure of the prepared nanophosphors. The photoluminescence emission spectra were found to consist of characteristic emission peaks at ∼591 nm ( 5 D 0 → 7 F 1 ), 610 nm ( 5 D 0 → 7 F 2 ), 651 nm ( 5 D 0 → 7 F 3 ) and 707 nm ( 5 D 0 → 7 F 4 ). The enhancement of about 3 times (3-fold) of the photoluminescence emission in the surface functionalized samples is ascribed as due to the efficient ligand energy transfer. The powder dusting technique was adopted to visualize the latent fingerprints using nanophosphor on several porous and non-porous surfaces under sunlight and ultraviolet (254 nm) light excitation. The developed fingerprints display the high sensitivity, selectivity and contrast by enabling up to two levels of friction ridge details. The above-mentioned results revealed that the surface functionalized core–shell structured nanophosphor can be successfully engaged in the area of solid state display and forensic science applications. • Intense red emitting surface functionalized core–shell SiO 2 @LaOF:Eu 3+ ,Li + nanophosphors via grafting oleic acid. • The 3-fold enhancement in the PL emission upon surface functionalized samples due to efficient ligand energy transfer. • Well defined fluorescence fingerprint images on variety of surfaces by revealing type I-II ridge characteristics. • Developed latent fingerprints shows superior contrast, sensitivity, selectivity and negligible background hindrance. • Fabricated invisible security ink and make it highly suitable for dip-pen mode.

Dual Modification Engineering via Lanthanide‐Based Halide Quantum Dots and Black Phosphorus Enabled Efficient Perovskite Solar Cells with High Open‐Voltage of 1.235 V

AbstractInterfacial engineering is one of the most effective means to improve the photoelectric conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). In this work, Ln3+‐based halide Cs3TbCl6 quantum dots (QDs) are synthesized through a modified hot‐injection method, which displays an excitonic emission centered at 431 nm and the characteristic emission peaks of Tb3+ ions. Then, the Ln3+‐based halide Cs3TbCl6 QDs are introduced to the interface of Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 perovskite films in the PSCs, which can regulate the energy levels, fill the grain boundaries and remove the ionic defects. Surprisingly, the Cs3TbCl6 QDs modified devices achieve a champion PCE of 22.89% with a super high open‐voltage of 1.235 V. The high open‐voltage can be mainly attributed to the better bandgap alignment, enhanced interface, and reduced defects density. Afterward, the hole transport layer (HTL) is modified by the black phosphorus QDs (BPQDs), yielding a champion PCE of 23.49% and a filling factor of 80.32%. The Cs3TbCl6 QDs modified unencapsulated device possesses well environmental stability and humidity stability. This work demonstrates a new kind of Ln3+‐based metal QDs and explores a new approach to fabricate the PSCs with high open‐voltage, high efficiency, and good stability through the QD‐based passivation techniques.

Highly Sensitive Dual-Mode Optical Thermometry of Er3+/Yb3+ Codoped Lead-Free Double Perovskite Microcrystal.

In this Letter, erbium (Er3+) and ytterbium (Yb3+) codoped perovskite Cs2Ag0.6Na0.4In0.9Bi0.1Cl6 microcrystal (MC) is synthesized and demonstrated systematically to the most prospective optical temperature sensing materials. A dual-mode thermometry based on fluorescence intensity ratio and fluorescence lifetime provides a self-reference and highly sensitive temperature measurement under dual wavelength excitation at a temperature from 300 to 470 K. Combined with the white-light emission derived from self-trapped excitons (STEs), the characteristic emission peak of Er3+ ions can be observed under 405 nm laser excitation. The fluorescence intensity ratio (FIR) between perovskite and Er3+ is used as temperature-dependent probe signal, of which maximum value for relative and absolute sensitivities reaches to 1.40% K-1 and 8.20 × 10-2 K-1. Moreover, Er3+ luminescence becomes stronger with the feeding Yb3+ increasing under 980 nm laser excitation. The energy transfer of Er3+ and Yb3+ is revealed by power-dependent photoluminescence (PL) spectroscopy, and the involved upconversion mechanism pertains to the two-photon excitation process. The results reveal that the Er3+/Yb3+ codoped lead-free double perovskite MC is a good candidate for a thermometric material for the novel dual-mode design.

Synthesis, structure and characterization of Pr[B5O8(OH)]NO3·2H2O

A new rare earth metal borate crystalline compound Pr[B5O8(OH)]NO3·2H2O (1) containing nitrate anions was obtained using a hydrothermal method. The crystal structure was examined using single-crystal X-ray diffraction. The compound crystallises in the monoclinic system (space group P21/n) with a = 6.4619(5) Å, b = 15.4518(13) Å, c = 10.5754(8) Å, β = 90.357(2)° and V = 1055.91(14) Å3. The basic building block of the compound was a [B5O10(OH)]6− polyanion cluster, which forms a two-dimensional B–O layered structure; The Pr3+ ions fill the windows of the B–O layers, whereas the nitrates and water molecules occupy the gaps between the B–O layers. The crystal structure was further characterised using powder diffraction, infrared transmission spectroscopy and thermogravimetric analysis. In addition, the solid-state fluorescence emission spectra of the crystal were measured, showing the characteristic emission peaks of Pr3+.

Effect of partial substituting Y3+ with Ln3+ (Ln = La, Gd) on photoluminescence enhancement in high-performance Na5Y(MoO4)4:Dy3+ white-emitting phosphors

White-emitting Na5Y1-yLny(MoO4)4:Dy3+ (Ln = La, Gd) phosphors were synthesized by a sol-combustion method. The effects of Ln3+ partial introduction on the structure and photoluminescence of Na5Y1-yLny(MoO4)4:Dy3+ (Ln = La, Gd) phosphors were studied. The X-ray diffraction and chemical composition results verified the successful introduction of Dy3+, La3+ and Gd3+ into the Na5Y(MoO4)4 lattice. Under the excitation of ultraviolet at 352 nm, the as-prepared phosphors showed a white emission with characteristic emission peaks at 577 nm (yellow) and 485 nm (blue), corresponding to the 4F9/2→6H13/2 and 4F9/2→6H15/2 transitions of Dy3+ ions, respectively. By substituting Y3+ ion with La3+ and Gd3+, the photoluminescence intensity of Na5Y(MoO4)4:Dy3+ sample was obviously enhanced due to the crystal field effect surrounding the luminescence center Dy3+. The chromaticity coordinates of all phosphors were located at the white light region, and the substitution of La3+ or Gd3+ could realize a higher color rendering index of white emission. Therefore, the as-prepared white-emitting Na5Y0.90La0.06(MoO4)4:0.04Dy3+ and Na5Y0.88Gd0.08(MoO4)4:0.04Dy3+ phosphors could be used as single-component phosphor for w-LEDs application.

Synthesis and luminescence enhancement of red-emitting Sr9Y(PO4)7:Eu3+ phosphor through Gd3+ co-doping for white light-emitting diodes

A series of Sr9Y(PO4)7:Eu3+ and Sr9Y(PO4)7:Eu3+, Gd3+ red-emitting phosphors were prepared via a high-temperature solid-state method, Gd3+ ion was co-doped in Sr9Y(PO4)7:Eu3+ as sensitizer to enhance the luminescence property. The X-ray diffraction results verify that the structure of the as-prepared samples is consistent with the standard Sr9Y(PO4)7 phase. All the Sr9Y(PO4)7:Eu3+ samples show both characteristic emission peaks at 594 nm and 614 nm under near-ultraviolet excitation of 394 nm. The co-doping of Gd3+ significantly improves the luminescence intensity of the Sr9Y(PO4)7:Eu3+ phosphors due to the crystal field environment effect and energy transfer of Gd3+→Eu3+ caused by the introduction of Gd3+, especially Sr9Y(PO4)7:0.11Eu3+, 0.05Gd3+, which emission intensity is higher than that of Sr9Y(PO4)7:0.11Eu3+ by 1.21 times. The color purity and lifetime of Sr9Y(PO4)7:0.11Eu3+, 0.05Gd3+ phosphor are 88.26% and 3.7615 ms, respectively. A w-LED device was packaged via coating the as-prepared phosphor on n-UV chip of 395 nm with commercial phosphors. These results exhibit that the Sr9Y(PO4)7:Eu3+, Gd3+ red-emitting phosphor can be used as a red component in the w-LEDs application.

Near-IR Emission and upconversion luminescent properties of Tb3+/Yb3+ Co-doped HfO2/SiO2 nanoparticles

The luminescent characteristics of spherical hafnia/silica (HfO2/SiO2) nanoparticles (NPʼs) co-doped with Tb3+/Yb3+ were analysed. These NPʼs were synthesized using the spray pyrolysis technique. The addition of SiO2 and Tb3+/Yb3+ was found to induce a cubic phase in HfO2. The luminescent spectra presented the characteristic emission peaks for inter-electronic energy levels transitions of the Tb3+ and Yb3+ ions, with an excitation band centred at 270 nm. Under solid-state laser excitation at 980 nm an upconversion emission related to the Tb3+ ion was observed. The maximum emission peak in the visible region was at 543 nm, associated with 5D4 → 7F5 transitions of the Tb3+ ions and an IR emission peak at 970 nm (2F5/2 → 2F7/2) pertaining to Yb3+, with irradiation at 270 nm (UV). The energy transfer mechanism from Tb3+→Yb3+ (excitation at 270 nm), is discussed based on the time decay of the luminescence intensity analysis and the energy transfer efficiency (ηET) and was determined to be in the range of 29.2% to40.8%.