Study of the Electronic Structure and Optical Properties of Rare Earth Luminescent Materials

Rare earth luminescent materials have attracted significant attention due to their wide-ranging applications in the field of optoelectronics. This study aims to delve into the electronic structure and optical properties of rare earth luminescent materials, with the goal of uncovering their importance in luminescence mechanisms and applications. Through theoretical calculations and experimental methods, we conducted in-depth analyses on materials composed of various rare earth elements. Regarding electronic structure, we utilized computational techniques such as density functional theory to investigate the band structure, valence state distribution, and electronic density of states of rare earth luminescent materials. The results indicate that the electronic structural differences among different rare earth elements notably influence their luminescence performance, providing crucial clues for explaining the luminescence mechanism. In terms of optical properties, we systematically examined the material’s optical behaviors through fluorescence spectroscopy, absorption spectroscopy, and other experimental approaches. We found that rare earth luminescent materials exhibit distinct absorption and emission characteristics at different wavelengths, closely related to the transition processes of their electronic energy levels. Furthermore, we studied the influence of varying doping concentrations and impurities on the material’s optical properties. Experimental outcomes reveal that appropriate doping can effectively regulate the emission intensity and wavelength, offering greater possibilities for material applications. In summary, this study comprehensively analyzed the electronic structure and optical properties of rare earth luminescent materials, providing deep insights into understanding their luminescence mechanisms and potential value in optoelectronic applications. In the future, these research findings will serve as crucial references for the technological advancement in fields such as LEDs, lasers, and bioimaging.

Modular Design Using Sustainable Luminescent Materials in Energy-Saving Reflective Cat’s Eyes for Public Road Safety Planning

Recently,there has been a global movement toward environmental protection and energy conservation through the design and development of new products in accordance with sustainable utilisation.In this study,rare earth luminescent materials were used owing to their active light emission and reusability.Additionally,solar lightemitting diode lights and car-light reflection were utilised to increase the recognition and reliability of reflective cat eyes.Along with carbon reduction,this can save energy and enhance road safety.This study considered the Theory of Inventive Problem Solving and a literature review to analyse the issues in existing products.Then,expert interviews were conducted to screen projects and develop product design policies.Finally,the ratio of light-storage materials was experimentally determined and the prototypes implemented.This cat’s eye addresses the shortcomings identified in previous analyses of existing products.We applied energy storage environmental protection materials,together with material proportioning(which balanced warning efficiency against cost-effectiveness)to develop diversified modular kits;these were flexible in terms of quantity and easily assembled.This study achieved four key objectives:(1)reducing the research and development costs of the manufacturer;(2)offering buyers a diverse suite of products;(3)responding to a need to improve diverse road user safety;and(4)reducing government procurement costs for safety warning products.The results provide a reference for the creative modular design of energy-saving products for public road safety planning in various industries.

Online and Offline Hybrid Teaching in the Luminescent Materials and Applications Course

Due to the outbreak of |x-19,colleges and universities have actively responded to the call of the state to carry out online teaching in completing their teaching tasks.After the epidemic,the online and offline hybrid teaching has become a novel mode of teaching which meets the requirements of teaching reform and the information society.This teaching method integrates both the online and offline teaching which plays an important role in enhancing teaching qualities and learning experiences.However,due to the lack of experience,there are some issues occurring in the teaching process of this method.The Luminescent Materials and Applications course is used as the subject in this article.The difficulties in traditional offline teaching as well as the advantages,detailed course construction process,and effectiveness evaluation of hybrid teaching are summarized and meticulously analyzed.In regard to that,the application of the online and offline hybrid teaching in the Luminescent Materials and Applications course is beneficial to the learning of professional knowledge and the cultivation of students'scientific literacy.Therefore,it is an effective way to improve and enrich this course by using the online and offline hybrid teaching method.

Recent Progress on Nanoscale Rare Earth Luminescent Materials

1 Results The size of nanoscale rare earth luminescent materials is often smaller than that of the excitement or emission wavelength,and it has amazing surface state density. Therefore,it shows a lot of new luminescent phenomena such as the shift of CTS,the broadening of emission peaks,the variation of fluorescent lifetimes and quantum efficiency,and the increase of quenching concentration.It is not only of academic interest but also of technological importance for advanced phosphor applications to rese...

Preparation, Characterization and Luminescent Properties of MCM-41 Type Materials Impregnated with Rare Earth Complex

Hybrid materials incorporating Eu-(TTA)3·2H20 (hereafter designated as Eu-TTA, with TTA: thenoyltrifluoroacetone) in unmodified or modified MCM-41 by 3-aminopropyl-triethoxysilane (APTES) were prepared by impregnation method. The obtained materials were characterized using X-ray diffraction (XRD), IR and diffuse reflectance spectroscopy and luminescence spectra. All the hybrid samples exhibited the characteristic emission bands of Eu3+ under UV light exci-tation at room temperature, and the excitation spectra showed significant blue-shifts compared to the pure rare-earth complex. Although the red emission intensity in the modified hybrid was almost the half of the red emission intensity in the pure Eu-TTA complex at room temperature, the hybrid showed a much higher thermal stability due to the shielding character of the MCM-41 host.

Research Advances in Helicene Structure-Based Chiral Luminescent Materials and Their Circularly Polarized Electroluminescence

Benefited from direct generation of circularly polarized(CP) emission with tunable colors, high efficiencies and facile device architectures, CP organic light-emitting diodes(CP-OLEDs) have attracted great attention and are expected to meet industrial applications. Particularly, CP electroluminescence(CPEL) originated from CP-OLEDs has wide potential applications in 3D displays, optical information storage, quantum communication, and biological sensors. The diverse design strategies of chiral luminescent materials for CP-OLEDs, including small organic emitters, lanthanide and transition-metal complexes and conjugated polymers, have been extensively explored. Helicene with twisted extended π-conjugated molecular structure could exhibit special helical chirality and excellent circularly polarized luminescence properties, which has been employed as the ingenious chirality core for constructing efficient chiral luminescent materials. In addition, significant improvements have been made in terms of CP photoluminescence research, however, the development of CPEL with more application prospects in optoelectronic technology still lags behind. In this review, we systematically summarize the recent advances in chiral luminescent materials based on helicene structure and their CPEL properties, including helicene-based chiral fluorescence molecules, transition metal complexes and thermally activated delayed fluorescence molecules, and discuss current challenges and future perspectives for this hot research field. We believe this progress report will provide a promising perspective of OLEDs based on helicene emitters with CPEL properties for extensive researchers, including chemical, physical and material scientists in different disciplinary fields and attract them to this rapidly developing field.

Rational Design of Star-shaped Molecules with Benzene Core and Naphthalimide Derivatives End Groups as Organic Light-emitting Materials

A series of star-shaped molecules with benzene core and naphthalimides derivatives end groups have been designed to explore their optical,electronic,and charge transport properties as charge transport and/or luminescent materials for organic light-emitting diodes（OLEDs）. The frontier molecular orbitals（FMOs） analysis has turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer（ICT）. The calculated results show that the optical and electronic properties of star-shaped molecules are affected by the substituent groups in N-position of 1,8-naphthalimide ring. Our results suggest that star-shaped molecules with n-butyl（1）,benzene（2）,thiophene（3）,thiophene S？,S？-dioxide（4）,benzo[c][1,2,5]thiadiazole（5）,and 2,7a-dihydrobenzo[d]thiazole（6） fragments are expected to be promising candidates for luminescent and electron transport materials for OLEDs. This study should be helpful in further theoretical investigations on such kind of systems and also to the experimental study for charge transport and/or luminescent materials for OLEDs.

Effects of SrO/Al_2O_3 Molar Ratio on the Luminescent Characteristics of Rare-Earth Strontium Aluminate Phosphors

The study on the effects of SrO/Al 2O 3 molar ratio on the crystalline phases and photoluminescence characteristics of strontium aluminate phosphors co-activated with Eu 2+ and Dy 3+ were conducted by X-ray powder diffractometry, fluorescence spectrometer and photometer. The strontium aluminate luminescent materials with different SrO/Al 2O 3 molar ratio emit the visible lights with different color tone after removal of excitation. The peak wavelengths of the emission spectra drift in the direction of short wave, the quantity of Sr 4Al 14O 25 crystalline phase increases and the afterglow time lengthens with the SrO/Al 2O 3 reduction. The results show that when the SrO/Al 2O 3 molar ratio is near 1, the photoluminescence materials have high luminescent intensity, and when it is near 0.75, they have long afterglow time. However, when SrO/Al 2O 3 molar ratio is more than 1, the luminescent materials appear strong alkaline in water solution; when SrO/Al 2O 3 molar ratio is much less than 0.75, the samples need a higher temperature to be sintered.

Synthesis of Ultra-Fine SrAl_2O_4∶Eu, Dy Phosphor and Its Luminescent Properties

Precursor of SrAl_2O_4∶Eu, Dy phosphor was prepared by co-precipitation method, in which dispersing agent was added to control particle size. Microwave radiation method was used to synthesize SrAl_2O_4∶Eu, Dy phosphors. Experimental results show that the precursor was composed of crystalline ammonium dawsonite hydrate and strontium carbonate, and the adding of dispersing agent can effectively diminish precursor size. The precursor can be transformed to pure SrAl_2O_4 phase after being calcined for 40 min in microwave chamber. The phosphors possess good persistent luminescent properties, finer grain size ranged from 0.2 μm to 5 μm and better size distribution than that of solid-state reaction. The doping of B^(3+) will result in the increasing of crystallite size, but can effectively improve phosphors′ persistent luminescent properties.

Comparison study of two aldehyde group finishing agents in surface modification of up-conversion luminescence materials

Surface modification of up-conversion luminescence materials （Na[Y0.57Yb0.39Er0.04]F4 modified by amino groups） by grafting and modifying with aldehyde groups was studied by means of Fourier transform infrared spectroscopy （FTIR）, scanning electron microscopy （SEM）, thermogravimetric analysis （TGA）, and emission spectrum （EM）. The surface modification effect was compared using two different finishhag agents, p-phthalaldehyde and glutaraldehyde. It was found that the surface of up-conversion luminescence materials could be modified by aldehyde groups of the two finishing agents, the systematic dispersibility and the thermostability of the up-conversion luminescence material modified by p-phthalaldehyde were better than those of the material modified by glutaraldehyde, and the luminous intensity of the material modified by p-phthalaldehyde was increased. The AI （the ratio of the suspended segmental quality in the specimen to the total mass of the specimen） of the material modified by p-phthalaldehyde was higher than that of the material modified by glutaraldehyde. It is obviously seen that the embellishment effect of p-phthalaldehyde as a finishing agent was better than that of glutaraldehyde. In addition, the reasons why p-phthalaldehyde is a good finishing agent are also explained.

Study of Photostimulable Luminescence Materials Sr_9Ca(PO_4)_6Cl_2:Eu

The polycrystalline Sr_9Ca(PO_4)_6Cl_2:Eu has been synthesized by solid state reaction.The reaction condition,the appropriate raw materials and their quantity used,which may affect the photostimulable luminescence (PSL),have been systematically inves- tigated.The properties of this PSL phosphor as a material for storing and reproducing the X-ray image in computer-aided radiography have been reported briefly.

Synthesis and Properties of Luminescent Material La_2O_2CO_3

A novel rare earth luminescent material La2O2CO3 was synthesized successfully by sintering the mixture of La2(CO3)3 and KCl powders. The XRD results revealed that the additive KCl not only affected the crystal form and crystallinity of the final product, but also greatly promoted its luminescence, compared with the products without adding KCl. The as-prepared material showed a strong green emission band centered at 470 nm under the excitation of 325 nm. Our experimental results indicated that the crystal form of La2O2CO3 affected its luminescent properties significantly. According to the primary analysis, the green emission might be related to the oxygen vacancies in La2O2CO3 lattice.

Luminescent metal-halide perovskites:fundamentals,synthesis,and light-emitting devices

Metal-halide perovskites have garnered considerable research attention as highly efficient light emitters in recent years due to their outstanding optoelectronic properties with remarkable tunability and excellent solution processabilities.Substantial advancements have been achieved in the development of novel halide perovskites,and the exploitations of these materials in lightemitting devices.This review comprehensively outlines recent breakthroughs in metal-halide perovskites,encompassing the rational design of perovskite materials with tunable light emission properties,the controllable growth of single crystal for a deeper understanding of their structure-property relationships,as well as the fundamental insights into the photophysics and carrier dynamics in perovskite systems.Additionally,it provides an overview of recent applications of perovskite materials in high-performance light-emitting diodes(LEDs)and lasers.

Improvement of water resistance of long afterglow SrAl_2O_4: Dy, Eu phosphor by coating with SiO_2 film

The long afterglow SrAl_2O_4: Dy, Eu phosphor is liable tohydrolyze in water with deterioration of the lumin- escent property.SrAl_2O_4: Dy, Eu phosphors were therefore heated at 60-90 deg. C inTEOS sol to form a surface gel and then heat-treated at 400 deg. C toobtain SiO_2 coated phosphors. Observation by ?Transmission ElectronMicroscope (TE) and X- ray photoelectron spectroscopy (XPS) showsthat a thin silica film forms on the surface of the phosphors. Thecoating procedure can be illustrated by a four-step process and thetransparent silica film can suppress the hydrolysis process, so thatthe luminescent properties of the phosphors are unimpaired or evenbetter.

VUV Spectroscopy of GdPO_4∶Eu^(3+) and GdBO_3∶Eu^(3+)

The emission and the excitation spectra of GdPO4 ： Eu^3＋ and GdBO3： Eu^3 ＋ prepared by solid state reaction method were investigated using the synchrotron radiation source of SUPERLUMI station of HASYLAB. The energy transfer between Gd^3＋ and Eu^3＋ was discussed with the probability of quantum cutting process. In the excitation spectra monitoring the red emission from Eu^3＋ , the distinct lines corresponding to the intraconfigurational 4f-4f transitions from Gd^3＋ were observed for both samples, indicating an efficient energy transfer from host Gd^3＋ ions to the doped Eu^3＋ ions. The efficient energy transfer is necessary for the quantum cutting process based on the two-step energy transfer from Gd^3＋ to Eu^3＋ . However, the overlapping of the lines corresponding to Gd^3＋ ：^8S7/2→^6GJ and the broad excitation band （180 - 270 nm） due to Eu^3＋- O^2- charge transfer states （CTS） around 200 nm cause excitation energy on ^6GJ levels to dissipate into CTS by direct energy transfer, unfavorable to the cross relaxation energy transfer between Gd^3＋ and Eu^3＋, thus unfavorable to the quantum cutting process. With the help of the general rules governing the energy positions of Eu^3＋-O^2- ：CTS, the suggestions concerning searching suitable oxide hosts for Gd^3＋-Eu^3＋ quantum cutting were made.

Synthesis and Photoluminescence of Three Europium (Ⅲ) Ternary Complexes with New Secondary Ligands of Different Structure

Three new 1,10-phenanthroline derivatives, dipyrido (3,2-f: 2,3-h) quinoxaline (DPQN), imidazo (5,6-f)-(1,10)-phenanthroline (IP) and 3-phenyl-imidazo (5,6-f)-(1,10)-phenanthroline (PIP) were designed and synthesized as a secondary ligand to coordinate with europium (Ⅲ) ion while dibenzoylmethane (DBM) was used as the first ligand. The compositions of the ligands and the europium (Ⅲ) ternary complexes were confirmed by elementary analysis, IR and (()~1H-NMR) spectroscopy. The UV-visible absorption spectra, thermal stability, photoluminescence spectra, quantum yield and fluorescence life time of the Eu(Ⅲ) complexes were investigated. The effect of the structure of the secondary ligand on the photoluminescence of the complexes was discussed. The results show that the synthesized Eu(Ⅲ) complexes are good red-emitiing materials for potential application in fabrication of organic electroluminescence devices.

Crystal Structure of Lithium Yttrium Borate LiY_6O_5(BO_3)_3

Single crystals of LiY6O5（BO3）3 were obtained by the flux method and its structure was determined by a four-circle automatic diffractometer with a MoKα radiation. It crystallizes in monoclinic, space group P21/n with a = 8.330（3）, b = 15.444（4）, c = 8.780（3）°A,β = 91.85（3）°, V = 1129.0（6）°A^3, Z = 4, Mr= 796.83, F（000） = 1456, μ = 30.567 mm^-1, Dc= 4.688 g/cm^3, the final R = 0.0722 and wR = 0.1304. It exhibits a three-dimensional fiamework of yttrium-oxygen polyhedra interconnected by common edges and corners. B and Li atoms are located in the planes and cavities formed by oxygen atoms, respectively.

Identification of surface oxygen vacancy-related phonon–plasmon coupling in TiO_2 single crystal

Oxygen vacancies （OVs） play a critical role in the physical properties and applications of titanium dioxide nanos- tructures, which are widely used in electrochemistry and photo catalysis nowadays. In this work, OVs were artificially introduced in the surface of a pure TiO2 single crystal by pulsed laser irradiation. Raman spectra showed that the intensity of Eg mode was enhanced. Theoretical calculations disclose that this was caused by the strong coupling effect between the phonon vibration and plasmon induced by the OVs-related surface deformation, and good agreement was achieved between the experiments and theory.

Synthesis of Y_2O_3:Eu^(3+) Hollow Spheres Using Silica as Templates

The Y2O3 ： EU^3 ＋ hollow spheres were synthesized using the template-mediated method. XRD patterns indicated that the broadened diffraction peaks resulted from nanocrystals in Y2O3 ： EU^3 ＋ shells of hollow spheres. XPS spectra showed that the Y2O3 ： EU^3 ＋ shells were linked with silica cores by a Si-O-Y chemical bond. SEM and TEM observations showed that the size of the SiO2/Y2O3 ： EU^3 ＋ core-shell particle was about 100 nm, and the thickness of the Y2O3 ： EU^3 ＋ hollow sphere was less than 5 nm. The photoluminescence spectra of the SIO2/Y2O3 ： EU^3 ＋ core-shell materials and Y2O3 ： EU^3 ＋ hollow spheres had red luminescent properties, and the broadened emission peaks came from nanocrystals composed of the Y2O3 ： EU^3 ＋ shell.