Mid-infrared luminescence of Dy^(3+)-doped Ga_2S_3–Sb_2S_3–CsI chalcohalide glasses

The mid-infrared （MIR） luminescent properties of Dy3＋ ions in a new chalcohalide glass host, Ga2S3-Sb2S3-CsI, are investigated; and the suitability of the doped glass for MIR fiber lasers is evaluated. The Dy3＋-doped chalcohalide glasses exhibit good thermal stability and intense MIR emissions around 2.96 μm and 4.41 μm. These emissions show quantum efficiencies （η） as high as ～ 60%, and have relatively large stimulated emission cross sections （σem）. The low phonon energy （～ 307 cm-1） of the host glass accounts for the intense MIR emissions, as well as the high η. These favorable thermal and emission properties make the Dy3＋-doped Ga2S3-Sb2S3-CsI glasses promising materials for MIR fiber amplifiers or lasers.

3.1 μm mid-infrared luminescence in Er^(3+) doped ZnF_(2) modified aluminum fluoride glass

Herein,melt-quenching and Er^(3+) doping were used to synthesize fluoride glass specimens with low phonon energies(582 cm^(-1)).These glass specimens exhibit intense 3.1 μm mid-infrared band emission when they are excited by a 980 nm laser diode,achieving a full width at half maximum(FWHM) of about166 nm.This 3.1 μm emission intensity is enhanced by the introduction of ZnF_(2) to the AlF_(3)-based fluoride glass.Up-conversion emission,strong near-infrared emission,and fluorescence lifetime are enhanced to different degrees by increasing the ZnF_(2) content.Moreover,the spectroscopic characteristics of the glass specimens and the highly efficient Er^(3+):~4S_(3/2)→~4F_(9/2) transition's energy transfer mechanism were investigated.The absorption spectra and emission spectra of these aluminum fluoride glass specimens were used to calculate their gain coefficients and maximum cross sections at 1.5 and 3.1 μm.Overall,the spectral properties of these prepared aluminum fluoride glass specimens demonstrate their high potential for use as infrared laser host materials.

Tm^(3+) and Nd^(3+) singly doped LiYF_4 single crystals with 3-5 μm mid-infrared luminescence

Mid-infrared（MIR） emissions of 2.4 and 3.5 μm from Tm3＋：LiYF4 single crystals attributed to3H4 →3H5 and3H5 →3F4 transitions as well as MIR emissions of 4.2,4.3,and 4.5 μm from Nd3＋：LiYF4 lasers attributed to4I15/2 →4I13/2,4I13/2 →4I11/2,and4I11/2 →4I9/2 transitions,respectively,are observed.LiYF4 single crystals possess high transmittance of over 85% in the 2.5-6 μm range.The large emission crosssections of Tm-doped crystals at 2.4 μm（1.9×10-20cm2） and Nd-doped crystals at 4.2 μm（0.84×10-20 cm2） as well as the high rare-earth doping concentrations,excellent optical transmission,and chemicalphysical properties of the resultant samples indicate that Nd3＋and Tm3＋singly doped crystals may be promising materials for application in MIR lasers.

Nd^(3+)/Yb^(3+) co-doped mid-infrared luminescence fluorobromide glass with energy transfer and zero-thermal-quenching IR emission

Nd^(3+)/Yb^(3+)co-doped fluorobromide glass samples were prepared by melt quenching.The mid-infrared(MIR)luminescence of the Nd^(3+)/Yb^(3+)co-doped fluorobromide glass was investigated by Br-doping reduces the phonon state density of the matrix.The 3.9μm MIR luminescence of the samples excited at 793 and 980 nm pump excitation was investigated in detail.There is an effective mutual energy transfer process between Nd^(3+)and Yb^(3+).It is proved under 793 nm excitation that the luminescence of Nd^(3+)at 3.9μm is reduced by effective energy transfer from,Nd^(3+):2 H11/2→Yb^(3+):2 F5/2,At the same time,it is proved that the effective energy transfer from Yb^(3+):2 F5/2→Nd^(3+):2 H11/2 under the excitation of 980 nm enhances the luminescence of Nd^(3+)at 3.9μm.In addition,it is found that the samples still have good infrared(IR)luminescent properties when the temperature changes.The emission cross-sectional area and the absorption cross-sectional area areσem(3.87×10^(-20)cm^(2))andσabs(4.25×10^(-20)cm^(2)).The fluorescence decay characteristics of the sample at 3.9μm at the 2 H11/2 level were investigated and the fluorescence lifetime was calculated.The gain performance of the sample was calculated and analyzed,which can reach 4.25×10^(-20)cm^(2).Those results prove that Nd^(3+)/Yb^(3+)co-doped fluorobromide glass is the potential mid-infrared laser gain material.

Atomic layer deposition in advanced display technologies:from photoluminescence to encapsulation

Driven by the growing demand for next-generation displays,the development of advanced luminescent materials with exceptional photoelectric properties is rapidly accelerating,with such materials including quantum dots and phosphors,etc.Nevertheless,the primary challenge preventing the practical application of these luminescent materials lies in meeting the required durability standards.Atomic layer deposition(ALD)has,therefore,been employed to stabilize luminescent materials,and as a result,flexible display devices have been fabricated through material modification,surface and interface engineering,encapsulation,cross-scale manufacturing,and simulations.In addition,the appropriate equipment has been developed for both spatial ALD and fluidized ALD to satisfy the low-cost,high-efficiency,and high-reliability manufacturing requirements.This strategic approach establishes the groundwork for the development of ultra-stable luminescent materials,highly efficient light-emitting diodes(LEDs),and thin-film packaging.Ultimately,this significantly enhances their potential applicability in LED illumination and backlighted displays,marking a notable advancement in the display industry.

In situ luminescence measurements of GaN/Al_(2)O_(3) film under different energy proton irradiations

Ion beam-induced luminescence(IBIL) experiments were performed to investigate the in situ luminescence of GaN/Al_(2)O_(3) at varying ion energies,which allowed for the measurement of defects at different depths within the material.The energies of H^(+)were set to 500 keV,640 keV and 2 MeV,the Bragg peaks of which correspond to the GaN film,GaN/Al_(2)O_(3) heterojunction and Al_(2)O_(3) substrate,respectively.A photoluminescence measurement at 250 K was also performed for comparison,during which only near band edge(NBE) and yellow band luminescence in the GaN film were observed.The evolution of the luminescence of the NBE and yellow band in the GaN film was discussed,and both exhibited a decrease with the fluence of H^(+).Additionally,the luminescence of F centers,induced by oxygen vacancies,and Cr^(3+),resulting from the ^(2)E →^(4)A_(2) radiative transition in Al_(2)O_(3),were measured using 2 MeV H^(+).The luminescence intensity of F centers increases gradually with the fluence of H^(+).The luminescence evolution of Cr^(3+)is consistent with a yellow band center,attributed to its weak intensity,and it is situated within the emission band of the yellow band in the GaN film.Our results show that IBIL measurement can effectively detect the luminescence behavior of multilayer films by adjusting the ion energy.Luminescence measurement can be excited by various techniques,but IBIL can satisfy in situ luminescence measurement,and multilayer structural materials of tens of micrometers can be measured through IBIL by adjusting the energy of the inducing ions.The evolution of defects at different layers with ion fluence can be obtained.

Energy transfer process of Nd^(3+)/Ho3+co-doped fluoride halide glasses with anion substituted multi-wavelength tunable mid-infrared luminescence

Ho^(3+)doped ZBLAN glass with 2.0 and 2.9μm emission was prepared.In order to further improve the luminescence of Ho^(3+),halogen ions(Cl,Br,1)were introduced to reduce the maximum phonon energy and phonon state density of the sample.At the same time,Nd^(3+)was introduced to transfer the energy to Ho^(3+)pumped with a 793 nm laser(Nd^(3+):4 F5/2,4 F3/2→Ho^(3+):5 I6).The effect of different halogen ion on the luminescent properties of the fluoride halide glass was compared.The results show that the luminescent intensity of infrared increases with the introduction of different halogen ions.By comparison,it is found that the sample with I-has the strongest luminescence of 1064 nm,2.0μm and 2.9μm.This is consistent with the calculated J-O intensity parameters.In addition,the 2.0 and 2.9μm emission of Ho^(3+)pumped with a 450 nm laser will not disappear.A mid-infrared sample with multi-wavelength excitation and multi-wavelength emission can be obtained.Nd^(3+)/Ho^(3+)co-doped fluoride halide glasses with 1064 nm,2.0μm and 2.9μm luminescence were prepared by melt quenching method.The luminescent mechanism and the energy transfer process between the two ions of Nd^(3+)/Ho^(3+)co-doped fluoride halide glass were studied.The J-O parameters,luminescence lifetime and absorption emission cross-sectional area of Ho^(3+)and Nd^(3+)were calculated,respectively.It is found that the value ofΩ2 in the glass matrix increases with the introduction of different halogen ions,whileΩ4 andΩ6 do not change obviously in different glass compositions.This is because the environment of the crystal field around the rare earth ions changes.The crystal phase and phonon energy of the sample were analyzed by X-ray diffraction pattern and a Fourier transform infrared spectrometer,respectively.Based on the above spectra and data(phonon energy is 634.71 cm-1),it can be predicted that Nd^(3+)/Ho^(3+)co-doped fluoride halide glass is a potential mid-infrared luminescent material.

Mid-infrared lightly Er^(3+)-doped CaF_(2)laser under acousto–optical modulation

A 1.7-at.%Er:CaF_(2)crystal was synthesized by temperature gradient method.The Er:CaF_(2)crystal was applied in acousto-optically Q-switched laser at mid-infrared region for the first time.Using a Te O_(2)-based crystal as Q-switcher,we obtained a laser diode(LD)end-pumped Er:CaF_(2)laser with the highest single pulse energy up to 0.49 mJ and maximum peak power of 0.56 kW under 6.34-W absorbed pump power.The implication of these results is that the low-doped Er:CaF_(2)crystal exhibits promising optical properties in solid-state lasers.

GCR-Net:3D Graph convolution-based residual network for robust reconstruction in cerenkov luminescence tomography

Cerenkov Luminescence Tomography(CLT)is a novel and potential imaging modality which can display the three-dimensional distribution of radioactive probes.However,due to severe ill-posed inverse problem,obtaining accurate reconstruction results is still a challenge for traditional model-based methods.The recently emerged deep learning-based methods can directly learn the mapping relation between the surface photon intensity and the distribution of the radioactive source,which effectively improves the performance of CLT reconstruction.However,the previously proposed deep learning-based methods cannot work well when the order of input is disarranged.In this paper,a novel 3D graph convolution-based residual network,GCR-Net,is proposed,which can obtain a robust and accurate reconstruction result from the photon intensity of the surface.Additionally,it is proved that the network is insensitive to the order of input.The performance of this method was evaluated with numerical simulations and in vivo experiments.The results demonstrated that compared with the existing methods,the proposed method can achieve efficient and accurate reconstruction in localization and shape recovery by utilizing threedimensional information.

Simultaneous Morphologies and Luminescence Control of NaYF_(4)∶Yb/Er Nanophosphors by Surfactants for Cancer Cell Imaging

Hydrophilic rare-earth up-conversion nanophosphors(UCNPs)with small sizes and a strong up-conversion luminescence have attracted much interest.Herein the simultaneous control of morphologies and the up-conversion luminescence intensities was reported for NaYF_(4)∶Yb/Er nanophosphors by a facile hydrothermal procedure with different surfactants.With the change of the surfactants from polyvinylpyrrolidone(PVP)to sodium citrate(CIT),edetate disodium(EDTA)or sodium dodecyl benzenesulfonate(SDBS),the morphology of NaYF_(4)∶Yb/Er nanophosphors transformed from nanoparticles with a diameter of about 70.0 nm to hexagonal nanoblocks with a thickness of about 125.0 nm and a length of about 240.0 nm,nanorods with a diameter of about 700.0 nm and a length of about 2.6μm,or nanowires with a diameter of 250.0 nm and a length of about 3.2μm.Simultaneously,their up-conversion luminescence intensity went down gradually under laser irradiation at a wavelength of 980 nm due to the increase of photobleaching.PVP-capped NaYF_(4)∶Yb/Er nanoparticles exhibited the smallest size and the strongest up-conversion luminescence intensity.Biological experiment results revealed that NaYF_(4)∶Yb/Er nanophosphors exhibited a high biocompatibility and could be used as biological labels with a perfect signal-to-noise ratio for cancer cell imaging.

A Comparison of CNN and PLSR for Glucose Monitoring Using Mid-Infrared Absorption Spectroscopy

With the development of mid-infrared (MIR) photoelectric devices, mid-infrared spectroscopy has become one of the important methods for non-invasive detection of blood glucose. The mid-infrared region (4000 - 400 cm-1) has the well-known fingerprint region (1200 - 800 cm-1) of glucose, which has clearer characteristic absorption peaks and better specificity. There is a lot of molecular information about glucose in the MIR. The non-invasive detection of blood glucose by mid-infrared spectroscopy needs to achieve certain accuracy, and the quantitative model is an important factor affecting the accuracy of glucose detection. In this paper, the samples of imitation solution containing only glucose and the samples of imitation mixed solution are taken as the research objects, and the mid-infrared spectral data of the samples are collected. The full spectrum partial least squares Regression (PLSR) model, SNV + Ctr-PLSR model, MSC + Ctr-PLSR model, and convolutional neural networks (CNN) model of 3000 - 900 cm-1 band were constructed. Full spectrum PLS model and CNN model of 1200 - 900 cm-1 band were constructed. The experimental results show that the optimal model of the two bands is CNN, then the correlation coefficient of prediction set (Rp) of 3000 - 900 cm-1 band is 0.95, and the root mean square error of pre-diction set (RMSEP) value is 22.10. The Rp of 1200 - 900 cm-1 band is 0.95, and the RMSEP value is 22.54. The research results show that CNN is a promising method, which has higher accuracy than PLSR, and is especially suitable for modeling human complex environment. In addition, the study provides a theoretical and practical basis for CNN in feature selection and model interpretation.

Rapid Detection of Accelerants in Fire Debris Using a Field Portable Mid-Infrared Quantum Cascade Laser Based Analyzer

Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.

Thermally enhanced photoluminescence and temperature sensing properties of Sc2W3O12:Eu3+ phosphors

Recently, lanthanide-ion-doped luminescent materials have been extensively used as optical thermometry probes due to their fast responses, non-contact, and high sensitivity properties. Based on different responses of two emissions to temperature, the fluorescence intensity ratio(FIR) technique can be used to estimate the sensitivities for assessing the optical thermometry performances. In this study, we introduce different doping concentrations of Eu^(3+) ions into negative thermal expansion material Sc2W3O12to increase the thermal-enhanced luminescence from 373 K to 548 K, and investigate the temperature sensing properties in detail. All samples can exhibit their good luminescence behaviors thermally enhanced.The emission intensity of Sc2W3O12:6-mol% Eu3+phosphor reaches 147.8% of initial intensity at 473 K. As the Eu3+doping concentration increases, the resistance of the sample to thermal quenching decreases. The FIR technique based on each of the transitions 5D→7F_(1)(592 nm) and 5D→7F_(2)(613 nm) of Eu3+ions demonstrates a maximum relative temperature sensitivity of 3.063% K-1at 298 K for Sc_(2)W_(3)O_(12):6-mol% Eu3+phosphor. The sensitivity of sample decreases with the increase of Eu3+concentration. Benefiting from the thermal-enhanced luminescence performance and good temperature sensing properties, the Sc_(2)W_(3)O_(12):Eu^(3+)phosphors can be used as optical thermometers.

New Opportunities for Lanthanide Luminescence

Trivalent lanthanide ions display fascinating optical properties. The discovery of the corresponding elements and their first industrial uses were intimately linked to their optical properties. This relationship has been kept alive until today when many high-technology applications of lanthanide-containing materials such as energy-saving lighting devices, displays, optical fibers and amplifiers, lasers, responsive luminescent stains for biomedical analyses and in cellulo sensing and imaging, heavily rely on the brilliant and pure-color emission of lanthanide ions. In this review we first outlined the basics of lanthanide luminescence with emphasis on f-f transitions, the sensitization mechanisms, and the assessment of the luminescence efficiency of lanthanide-containing emissive molecular edifices. Emphasis was then put on two fast developing aspects of lanthanide luminescence： materials for telecommunications and light emitting diodes, and biomedical imaging and sensing. Recent advances in NIR-emitting materials for plastic amplifiers and waveguides were described, together with the main solutions brought by researchers to minimize non-radiative deactivation of excited states. The demonstration in 1999 that erbium tris（8-hydroxyquinolinate） displayed a bright green emission suitable for organic light emitting diodes （OLEDs） was followed by realizing that in OLEDs, 25% of the excitation energy leads to singlet states and 75% to triplet states. Since lanthanide ions are good triplet quenchers, they now also play a key role in the development of these lighting devices. Luminescence analyses of biological molecules are among the most sensitive analytical techniques known. The long lifetime of the lanthanide excited states allows time-resolved spectroscopy to be used, suppressing the sample autofluorescence and reaching very low detection limits. Not only visible lanthanide sensors are now ubiquitously provided in medical diagnosis and in cell imaging, but the feasibility of using NIR emission of ions such as YbⅢ is now being tested because of deeper penetration in biological tissues.

Luminescence Properties of Green-Emitting Phosphor (Ba_(1-x),Sr_x_2SiO_4∶Eu^(2+) for White LEDS

The （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ green-emitting phosphors were synthesized by conventional solid-state reaction in a CO-reductive atmosphere, and their luminescent properties were investigated. The XRD data show that the Ba/Sr ratio not only affects the lattice parameters, but also influences the emission peak. The excitation spectra indicate that this phosphor can be effectively excited by UV light from 370 to 470 nm. The emission band is due to the 4f^65d^1→4f^7 transition of the Eu^2＋ ion. With an increase in x, the emission band shifts to longer wavelength and the reason was discussed. The emission spectra exhibit a satisfactory green performance under different excitation wavelength（380,398,412,420,460 nm）. （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ is a promising phosphor for green white-lighting-emission diode by ultraviolet chip.

Relationship between Crystal Structure and Luminescence Properties of (Y_(0.96-x)Ln_xCe_(0.04))_3Al_5O_(12) (Ln=Gd, La, Lu) Phosphors

The doping effects of La^3＋, Gd^3＋ and Lu^3＋ on the crystal structure and luminescence properties of （Yo96-x LnxCe0.04）3Al5O12（Ln = Gd, La, Lu） phosphors were studied. The X-ray diffraction patterns presented that with the inerease of the doping concentrations of La^3＋ and Gd^3＋ ions, the d-value of （Y0.96-xLnxCe0.04）3Al5O12 （Ln = Gd, La） inereased and the larger the doping ion, the stronger the effect would be. The doping amount causing phase transition in （Y0.96-xLnxCe0.04）3Al5O12 decreased with the inerease of the ionic radii of the doping lanthanide ions （La^3＋： 0.106 nm, Gd^3＋： 0. 094 nm, Lu^3＋ ： 0.083 nm）. The bigger doping ion of Gd^3＋ made the emission of （Y0.96-xGdxCe0.04）3Al5O12 move to red spectral region, but the smaller one of Lu^3＋ made it blue.

Preparation and luminescence properties of the red-emitting phosphor(Sr_(1-x)Ca_x)_2Si_5N_8:Eu^(2+) with different Sr/Ca ratios

A series of Eu2＋-doped ternary nitride phosphors, with a formula of（Sr1-xCax）2Si5N8：Eu2＋, were synthesized by high-temperature solid-state method.The structure and luminescence properties were characterized, indicating the potential application as a red phosphor in the phosphor-converted white light-emitting diodes.The X-ray diffraction patterns showed that the Sr2Si5N8 and Ca2Si5N8 phases were generated at each end of（Sr1-xCax）2Si5N8：Eu2＋ and coexisted in the range of 0.5≤x≤0.75.The emission spectra showed broad emission bands originating from the 4f65d1→4f7 transition of Eu2＋ ions.The emission peak changed with the variations in Ca2＋ concentration.

Study on Luminescence Properties and Crystal-Lattice Environment of Eu^(2+) in Sr_(4-x)Mg_x Si_3O_8Cl_4∶Eu^(2+) Phosphor

According to the Van Uitert experimental equation, crystal-lattice environment of Eu^(2+) in the Sr_4Si_3O_8Cl_4 crystal was discussed. By adding Mg^(2+) to the host lattice, Sr_(4- x )Mg_ x Si_3O_8Cl_4∶Eu^(2+) was synthesized and the emission peak shifted from blue-green (488 nm) to blue-violet (411 nm) with the increase of amount of the magnesium which replaced the strontium. By analyzing the spectra of Sr_(4- x )Mg_ x Si_3O_8Cl_4∶Eu^(2+) the two Eu^(2+) emission centers were found because of the change of crystal-lattice environment in the host and the crystal structure was obtained by X-ray diffraction data.

Electronic structure of the SrAl_2O_4:Eu^(2+) persistent luminescence material

The electronic structure of the strontium aluminate （SrAl2O4：Eu^2＋） materials was studied with a combined experimental and theo- retical approach. The UV-VUV synchrotron radiation was applied in the experimental study while the electronic structure of the non-optimized and optimized crystal structure were investigated theoretically by using the density functional theory. The structure of the valence and conduction bands as well as the band gap energy of the material together with the position of the Eu2＋ 4f7 85712 ground state were calculated. The calculated band gap energy （6.4 eV） agreed well with the experimental value of 6.6 eV. The valence band consisted mainly of oxygen states whereas the bottom of the conduction band of strontium states. In agreement with the experimental results, the calculated 4f7 8S7r2 ground state of Eu2＋ lies in the energy gap of the host. The position of the 4f7 ground state depended on the Coulomb repulsion strength. The position of the 4f7 ground state with respect to the valence and conduction bands was discussed using theoretical and experimental evidence available.

Synthesis and luminescence properties of rare earth ternary complexes consisting of Tb(Ⅲ), β-diketones and 1,10-phenanthroline (phen)

In order to study the luminescent properties of ternary rare earth complexes with fl-diketone ligand, three new β-diketone ligands, 1-phenyl-3-（p-phenylethynylphenyl）-1,3-propanedione（HPPP）, 1-（2-thienyl）-3-（p-phenylethynylphenyl）-1,3-propanedione （HTPP） and 1-（2-furyl）-3-（p-phenylethynylphenyl）-1,3-propanedione （HFPP）, were synthesized by Sonogashira coupling reaction and Claisen condensation. Three new ternary rare earth complexes, TbL3phen （L = PPP, TPP, or FPP）, were synthesized by the reaction of rare earth chloride TbCl3,1,10-phenanthroline （phen） with HPPP, HTPP, or HFPP respectively, in alcohol solution. The compositions were characterized by means of elemental analysis, chemical analysis, and IR spectra. Luminescent properties of the three new complexes have been studied. The results show that the ternary Yb（Ⅲ） complexes only emit the weak fluorescence of the Tb（Ⅲ） ion, which reveals the triplet state energy of the ligands does not match well with the excited state vibrating energy of Tb^3＋ ion.