NIR Mechanoluminescence from Cr3+ Activated Y3Al5O12 with Intense Zero Phonon line

Mechanoluminescence (ML) materials with long-wavelength emission bands are essential for future in vivo bioimaging, non-destructive testing of solids, etc. The lack of a defined mechanism, however, prevents the application of near infrared ML materials above 650 nm in several new fields. Here, the addition of Ga³⁺ ions to Y₃Al₅O₁₂: Cr³⁺ manipulates matrix microstructure evolution, boosting near-infrared (NIR) zero-phonon line (ZPL) stress optical output of the Cr³⁺ ion at 688 nm. The key factor changing the crystal field intensity D_q/B due to the addition of Ga³⁺ ions is what causes the luminescence amplification of ZPL. The ML fabricated by composite polydimethylsiloxane and Y₃Al₄GaO₁₂: Cr³⁺ (YAGG: Cr³⁺) may penetrate chicken feet epidermal tissue and 4 mm pork tissue thanks to the strong NIR ZPL emission of YAGG: Cr³⁺ phosphor. This discovery of enhancing near-infrared ZPL intensity by solid solution provides us with a new technique for optimizing NIR ML materials, as well as a new prospect for NIR ML materials in biological applications.     

Near-Infrared Mechanoluminescence of Cr3+ Doped Gallate Spinel and Magnetoplumbite Smart Materials

Mechanoluminescence (ML), as an optical response to deformation stimuli, shows great potential in high-end stress sensing, ultrasonic field visualization, and multidimensional anti-counterfeiting. However, processive practical applications in bio-medicine are constrained by the discovery of near-infrared (NIR) ML materials. Unlike lanthanides (Ln³⁺) with sharp multiplets, two kinds of Cr³⁺-doped NIR ML materials, gallate spinel (ZnGa₂O₄:Cr³⁺, Zn₃Ga₂GeO₈:Cr³⁺) and gallate magnetoplumbite (SrGa₁₂O₁₉:Cr³⁺) are here reported. Owing to the intrinsic cation antisite defects and cation vacancies in the matrix, these materials exhibit bright NIR ML under a relatively low load (20 N). In particular for SrGa₁₂O₁₉:Cr³⁺ (750 nm, peak; 100 nm, FWHM) with low persistent luminescence (PersL) interference, the ML behavior can be further rejuvenated under UV and sunlight irradiation. SrGa₁₂O₁₉:Cr³⁺ also shows bright NIR emission under photo- and thermo-stimulation. Owing to their excellent tissue penetration and concealment capability, NIR ML materials show great potential in the fields of bio-medicine and anti-counterfeiting.     

用闪光灯泵浦Cr3+:GSAG和Cr3+:GSGG的斜率效率、腔结构、色心及其可调谐性

Cr3+:Gd3Sc2Al3O12(GSAG)和Cr3+:Gd3Sc2Ga3O12(GSGG)属弱场石榴石晶体,室温下,能输出脉冲可调谐激光。我们用2英寸长的Cr3+:GSAG 激光棒得到了200mJ的多模输出,其可调谐范围为700～800nm。     

Photoluminescence and excitation features of Nd<Superscript>3+</Superscript> ions in (La<Subscript>0.97</Subscript>Nd<Subscript>0.03</Subscript>)<Subscript>2</Subscript>S<Subscript>3</Subscript> · 2Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

A combined study of the spectral photoluminescence distribution and excitation spectra of photoluminescence in La₂S₃ · 2Ga₂O₃ and (La_0.97Nd_0.03)₂S₃ · 2Ga₂O₃ glasses, along with the study of the transmission spectra of these glasses, was carried out. The radiative channel was ascertained to be the main channel for the energy transfer from the host matrix to the Nd³⁺ ions upon excitation of the glasses with light at a wavelength of the fundamental absorption band. Oxygen centers with the level E _c -2.0 eV act as sensitizing agents. The structural disordering of the glass host increases the variance in the magnitude of splitting of the multiplet levels from the 4f electronic states of the Nd³⁺ ion. This promotes nonradiative relaxation of the electrons from excited states to the laser ⁴F_3/2 level. The (La_0.97Nd_0.03)₂S₃ · 2Ga₂O₃ glasses can be considered as promising laser materials for obtaining the stimulated emission of radiation of Nd³⁺ ions under an optical pump in the range of the fundamental absorption band of the glass.     

Antimicrobial Gallium‐Doped Phosphate‐Based Glasses

Novel quaternary gallium‐doped phosphate‐based glasses (1, 3, and 5 mol % Ga₂O₃) were synthesized using a conventional melt quenching technique. The bactericidal activities of the glasses were tested against both Gram‐negative (Escherichia coli and Pseudomonas aeruginosa) and Gram‐positive (Staphylococcus aureus, methicillin‐resistant Staphylococcus aureus, and Clostridium difficile) bacteria. Results of the solubility and ion release studies showed that these glass systems are unique for controlled delivery of Ga³⁺. ⁷¹Ga NMR measurements showed that the gallium is mostly octahedrally coordinated by oxygen atoms, whilst FTIR spectroscopy provided evidence for the presence of a small proportion of tetrahedral gallium in the samples with the highest gallium content. FTIR and Raman spectra also afford an insight into the correlation between the structure and the observed dissolution behavior via an understanding of the atomic‐scale network bonding characteristics. The results confirmed that the net bactericidal effect was due to Ga³⁺, and a concentration as low as 1 mol % Ga₂O₃ was sufficient to mount a potent antibacterial effect. The dearth of new antibiotics in development makes Ga³⁺ a potentially promising new therapeutic agent for pathogenic bacteria including MRSA and C. difficile.     

<Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> photoreflectance spectra of semiconductor structures with a high density of interface states

The results of a photoreflectance spectroscopy study of Ga₂Se₃/n-GaAs samples prepared by long-term annealing of GaAs wafers (n≈10¹⁷ cm⁻³) in a Se-vapor atmosphere are presented. It was established that no photovoltage appears in the interface region of these structures under illumination. Photogeneration of the charge carriers in the substrate does not lead to a change in the Fermi level position at the interface, with only the depth of the space-charge region being modulated. The quantitative analysis of the spectra also indicates that the growth of a thick (∼ 1 μm) Ga₂Se₃ layer does not result in the expected shift of the Fermi level position in comparison to the natural oxide-covered surface. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 36, No. 7, 2002, pp. 838–842. Original Russian Text Copyright ? 2002 by Kuz’menko, Domashevskaya.     

Excitation mechanisms of multiple Er3+ sites in Er-implanted GaN

Site-selective photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies carried out at 6K on the ∼1540 nm ⁴I_13/2→⁴I_15/2 emissions of Er³⁺ in Er-implanted GaN have revealed the existence of four different Er³⁺ sites and associated PL spectra in this semiconductor. Three of these four sites are excited by below-gap, impurity- or defect-related absorption bands, with subsequent nonradiative energy transfer to the Er³⁺ 4f electrons; a fourth site is excited by direct Er³⁺ 4f shell absorption. PLE spectra obtained by selectively detecting Er³⁺ PL from each of the three sites pumped by broad below-gap absorption bands are compared with the PLE spectra of broad PL bands attributed to implantation damage-induced defects in the Er-implanted GaN. This comparison enables us to distinguish broad-band, below-gap optical excitation processes for Er³⁺ emission that are attributable to (1) absorption due to implantation damage-induced defects; (2) absorption due to defects or impurities characteristic of the as-grown GaN film; and (3) an Er-specific absorption band just below the band gap which may involve the formation of an Er-related isoelectronic trap. The two sites excited by impurity-or defect-related absorption bands are also strongly pumped by above-gap excitation, while the sites pumped by the Er-related trap and direct 4f shell absorption are not. This observation indicates that excitation of Er³⁺ luminescence in crystalline semiconductor hosts by either optical or electrical injection of electron-hole pairs is dominated by trap-mediated carrier capture and energy transfer processes. These trap-mediated processes may also control the thermal quenching of Er³⁺ emission in semiconductors.     

Photocatalyst Cr-doped titanium oxide nanoparticles: Fabrication,characterization, and investigation of the effect of doping on methyl orange dye degradation

The Cr/TiO₂ nanoparticles were synthesized via sol–gel technique by using tetraisopropylorthotitanate (TIPOT) and chromium nitrate (Cr(NO₃)₃·9H₂O) as precursors. The framework substitution of Cr into TiO₂ nanoparticles was evaluated by X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) techniques. XRD results showed that pure TiO₂ and Cr/TiO₂ nanoparticles own anatase phase with some rutile phase. SEM and TEM images confirmed the successful doping of Cr³⁺ ions into TiO₂ structure. The result of photocatalytic degradation of methyl orange (MO) demonstrated that appropriate Cr³⁺ doping can greatly enhance photocatalytic activity of TiO₂, which was attributed to the "red-shift" in ultraviolet–visible light (UV–vis) absorption spectra of TiO₂ nanoparticles while doped with Cr³⁺ ions and also to the improved transfer efficiency of photogenerated electrons and holes caused by incorporation of Cr³⁺ ions. The optimal Cr³⁺ concentration to obtain the highest photocatalytic activity was 5% mol. The relatively high photocatalytic activity of Cr/TiO₂ nanoparticles, suggests that it may have a promising future for water and wastewater purifications.     

Interrelation of vibrational spectra of Ag3Ga5Se9, Ag3Ga5Te9 and Ag3In5Te9 single crystals: A consequence of trivalent cation and anion substitutions

Silver gallium (indium) ternary selenides (tellurides) single crystals were studied through infrared reflection in the frequency range of 80–500 cm⁻¹. These spectra presented four infrared-active modes for studied crystals. Spectral dependencies of optical constants were computed from reflectivity spectra. The frequencies of transverse and longitudinal optical modes, damping constants and oscillator strengths were also evaluated. By replacing light selenium anions by heavier tellurium ones in Ag₃Ga₅Se₉ crystal and by substitution of light gallium cations by heavier indium ones in Ag₃Ga₅Te₉ crystal all the bands shift towards low frequencies. The bands observed in IR spectra of studied crystals were assigned to various vibration types (valence and valence-deformation). Crystal structure and atomic composition ratio of the constituent elements in Ag₃Ga₅Se₉, Ag₃Ga₅Te₉ and Ag₃In₅Te₉ crystals were revealed by structural characterization techniques of X-ray diffraction and energy dispersive spectroscopy.     

Three Electron Reversible Redox Reaction in Sodium Vanadium Chromium Phosphate as a High‐Energy‐Density Cathode for Sodium‐Ion Batteries

A sodium‐ion battery operating at room temperature is of great interest for large‐scale stationary energy storage because of its intrinsic cost advantage. However, the development of a high capacity cathode with high energy density remains a great challenge. In this work, sodium super ionic conductor‐structured Na₃V_2?xCr_x(PO₄)₃ is achieved through the sol–gel method; Na₃V_1.5Cr_0.5(PO₄)₃ is demonstrated to have a capacity of 150 mAh g^?1 with reversible three‐electron redox reactions after insertion of a Na⁺, consistent with the redox couples of V²⁺/³⁺, V³⁺/⁴⁺, and V⁴⁺/⁵⁺. Moreover, a symmetric sodium‐ion full cell utilizing Na₃V_1.5Cr_0.5(PO₄)₃ as both the cathode and anode exhibits an excellent rate capability and cyclability with a capacity of 70 mAh g^?1 at 1 A g^?1. Ex situ X‐ray diffraction analysis and in situ impedance measurements are performed to reveal the sodium storage mechanism and the structural evolution during cycling.     

Mechanisms of doping and the intensity of emission from intracenter f-f transitions in the doping Eu impurity in structures with InxGa1 ? x N/GaN quantum wells

Effect of doping with europium on the shape of the spectra of emission from structures with quantum wells based on In _x Ga_1−x N/GaN, on the mechanism of doping, and the intensity of emission caused by intracenter f-f transitions in Eu is studied. According to the data of M?ssbauer spectroscopy, the doping Eu impurity can have the charge state of the impurity ion of Eu²⁺ and Eu³⁺ or Eu³⁺ only. In the case where the charge state of the impurity ion is Eu³⁺, emission related to the intracenter transitions ⁵ D ₀−⁷ F ₂ (λ = 6220 ?) is observed. If the impurity ion can be found in the charge states Eu²⁺ and Eu³⁺, the emission related to the intracenter transitions characteristic of both Eu²⁺ and Eu³⁺ is not observed. Original Russian Text ? M.M. Mezdrogina, V.V. Krivolapchuk, V.N. Petrov, Yu.V. Kozhanova, E.Yu. Danilovski, R.V. Kuz’min, 2009, published in Fizika i Tekhnika Poluprovodnikov, 2009, Vol. 43, No. 4, pp. 467–477.     

Deep level spectra of MBE-grown ZnTe:Cr2+ layers

ZnTe:Cr²⁺ layers grown by molecular beam epitaxy on (001) GaAs substrates and doped with chromium from a metallic source or CrI₃ compound have been studied by current deep level transient spectroscopy (I-DLTS). The spectra of the layers show the presence of a deep level with an activation energy of (1.09±0.03) eV, related to a center originating from an electric-field-induced Cr²⁺-Cr⁺ transition. Doping with chromium from CrI₃ compound eliminates a number of point defects characteristic of ZnTe epitaxial layers, but leads to pronounced contamination of the grown films with iodine.     

A General Ammonium Salt Assisted Synthesis Strategy for Cr3+-Doped Hexafluorides with Highly Efficient Near Infrared Emissions

The discovery of highly efficient broadband near infrared (NIR) emission material is urgent and crucial for constructing NIR lighting sources and emerging applications. Herein, a series of NIR emission hexafluorides A₂BMF₆:Cr³⁺ (A = Na, K, Rb, Cs; B = Li, Na, K, Cs; M = Al, Ga, Sc, In) peaking at ≈733–801 nm with a full width at half maximum (FWHM) of ≈98–115 nm are synthesized by a general ammonium salt assisted synthesis strategy. Benefiting from the pre-ammoniation of the trivalent metal sources, the Cr³⁺ can be more efficiently doped into the A₂BMF₆ and simultaneously prevent the generation of the competitive phase. Particularly, Na₃ScF₆:Cr³⁺ (λ_em = 774 nm, FWHM ≈ 108 nm) with optimal Cr³⁺-doping concentration of 35.96% shows a high internal quantum efficiency of 91.5% and an external quantum efficiency of ≈40.82%. A lighting emitting diode (LED) device with a NIR output power of ≈291.05 mW at 100 mA driven current and high photoelectric conversion efficiency of 20.94% is fabricated. The general synthesis strategy opens up new avenues for the exploration of Cr³⁺-doped high efficiency phosphors, and the as-obtained record NIR output power demonstrates for NIR LED lighting sources applications.     

被动调Q腔内单共振光参变振荡器和Cr4+:YAG激光器

分析了以Cr4+:YAG作为饱和吸收体和激光增益介质的被动Q开关Cr4+:YAG激光器腔内抽运的Cr4+:YAG激光器和单共振光学参变振荡器(SRO)的特性.建立了描述这类激光器和单共振光学参变振荡器的动力学特性的速率方程.结果表明,适当条件下作为激光增益介质的Cr4+:YAG同时具有对二阶非线性作用过程产生的处于Cr4+:YAG激光增益谱范围内的SRO信号波的放大作用.分析中考虑了Cr4+:YAG较高激发态和激光上能级之间的弛豫时间约为100ns的中间能级对Cr4+:YAG饱和吸收体和激光器以及ICSRO的影响.     

Luminescence properties of Ca4GdO(BO3)3:Eu in ultraviolet and vacuum ultraviolet regions

The luminescent properties of Ca₄GdO(BO₃)₃:Eu³⁺ were investigated under excitation of UV and VUV light. Separate two broad bands at around 259 and 184 nm were observed in the excitation spectrum of Ca₄GdO(BO₃)₃:Eu³⁺. These peaks were assigned to the charge transfer transition of Eu³⁺-O²⁻ and Gd³⁺-O²⁻, respectively. Owing to the favorable spectral position in their broad intense excitation band, Eu³⁺ ions show a intense emission under 258 nm excitation in Ca₄GdO(BO₃)₃:Eu³⁺. This spectral position was determined by the free oxygen ions O (1). Ca₄GdO(BO₃)₃ doped with Eu³⁺ ion seems to be a preferable candidate as red lamp phosphor. On the other hand, a weak band with a maximum at about 184 nm was observed below 200 nm in the excitation spectrum of Ca₄GdO(BO₃)₃:Eu³⁺. This phosphor do not emit effectively under the 147 nm excitation. This unfavorable profile was also due to the O (1) ions, which played a role to the shifting towards the lower energy sides. The luminescence of Eu³⁺ ions in Ca₄GdO(BO₃)₃ was somewhat different from that observed in the other borates phosphors, but resembled to those observed in the oxide phosphors (e.g. Gd₂O₃, Y₂O₃ and Gd₂SiO₅). Such behavior was recognized by the detailed analysis of crystallographical surroundings around activator.     

ErIII‐Cored Complexes Based on Dendritic PtII–Porphyrin Ligands: Synthesis,Near‐IR Emission Enhancement,and Photophysical Studies

A series of stable and inert complexes with Er^III cores and dendritic Pt^II‐porphyrin ligands exhibit strong near‐IR (NIR) emission bands via highly efficient energy transfer from the excited triplet state of the Pt^II‐porphyrin ligand to Er³⁺ ions. The NIR emission intensity of thin films of Er^III complexes at 1530 nm, originating from 4f–4f electronic transitions from the first excited state (⁴I_13/2) to the ground state (⁴I_15/2) of the Er³⁺ ion, is dramatically enhanced upon increasing the generation number (n) of the aryl ether dendrons because of site‐isolation and light‐harvesting (LH) effects. Attempts are made to distinguish the site‐isolation effect from the LH effect in these complexes. Surprisingly, the site‐isolation effect is dominant over the LH effect in the Er³⁺‐[Gn‐PtP]₃(terpy) (terpy: 2,2′:6′,2″‐terpyridine) series of complexes, even though the present dendrimer systems with Er^III cores have a proper cascade‐type energy gradient. This might be due to the low quantum yield of the aryl ether dendrons. Thus, the NIR emission intensity of Er³⁺‐[G3‐PtP]₃(terpy) is 30 times stronger than that of Er³⁺‐[G1‐PtP]₃(terpy). The energy transfer efficiency between the Pt^II‐porphyrin moiety in the dendritic Pt^II‐porphyrin ligands and the Ln³⁺ ion increases with increasing generation number of the dendrons from 12–43 %. The time‐resolved luminescence spectra in the NIR region show monoexponential decays with a luminescence lifetime of 0.98 μs for Er³⁺‐[G1‐PtP]₃(terpy), 1.64 μs for Er³⁺‐[G2‐PtP]₃(terpy), and 6.85 μs for Er³⁺‐[G3‐PtP]₃(terpy) in thin films of these complexes. All the Er^III‐cored dendrimer complexes exhibit excellent thermal stability and photostability, and possess good solubility in common organic solvents.     

Synthesis and Luminescence of BaWO4:Ln3+ (Ln = Eu,Tb, and Dy) Powders

BaWO₄:Ln³⁺ powders were synthesized by a solid-state reaction method. The BaWO₄:Ln³⁺ samples were characterized by x-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), and luminescence spectroscopy. The XRD patterns reveal that the BaWO₄:Ln³⁺ samples present pure tetragonal scheelite structure. The SEM observations demonstrate that the BaWO₄:Ln³⁺ powders are irregular particles with size in the range of micrometers. The excitation spectra of the BaWO₄:Ln³⁺ samples show the broad absorption band originating from charge transfer between oxygen ligands and the central tungstate ions inside WO ₄ ^2? groups in the metal tungstate. The emission spectra of the BaWO₄:Ln³⁺ samples display the bands associated to the anion molecular complex (WO ₄ ^2? ) and the f–f transitions of Ln³⁺. According to the emission spectra and the chromaticity coordinates (Commission internationale de l'éclairage, CIE), one can see that the BaWO₄:Eu³⁺, BaWO₄:Tb³⁺, and BaWO₄:Dy³⁺ samples show emission in the red, green, and yellow region, respectively. The results show that the luminescence color can be altered by changing the Ln³⁺ doping in BaWO₄ material.     

A New Sol–Gel Material Doped with an Erbium Complex and Its Potential Optical‐Amplification Application

The crystal structure of a ternary Er(DBM)₃phen complex (DBM = dibenzoylmethane; phen = 1,10‐phenanthroline) and its in‐situ synthesis via a sol–gel process are reported. The infrared (IR), diffuse reflectance (DR), and fluorescence spectra of the pure complex and the Er³⁺/DBM/phen co‐doped luminescent hybrid gel, formed via an in‐situ method (ErDP gel), have been investigated. The results reveal that the erbium complex is successfully synthesized in situ in the ErDP gel. Excitation at the maximum absorption wavelength of the ligands resulted in the typical near‐IR luminescence (centered at around 1.54 μm) resulting from the ⁴I_13/2 → ⁴I_15/2 transition of the Er³⁺ ion, which contributes to the efficient energy transfer from the ligands to the Er³⁺ ion in both the Er(DBM)₃phen complex and the ErDP gel (an antenna effect). The full width at half maximum (FWHM) centered at 1541 nm in the emission spectrum of the ErDP gel is 72 nm, which has potential for optical‐amplification applications. Further theoretical analysis on the Er³⁺ ion in the ErDP gel shows that it appears to be a promising candidate for tunable lasers and planar optical amplifiers.     

Hydrothermal Synthesis and Luminescent Properties of BiPO4:Eu3+ Phosphors

In this study, BiPO₄:Eu³⁺ phosphors were synthesized by a facile hydrothermal route at different temperatures. The BiPO₄:Eu³⁺ particles were characterized by x-ray powder diffraction (XRD), infrared spectra, and luminescence spectroscopy. The XRD results reveal that the BiPO₄:Eu³⁺ particles present different phases for different hydrothermal temperatures. It is found that a hexagonal phase is formed at 100°C, which transforms to a low-temperature monoclinic phase (MP) when the hydrothermal temperature is increased to 150°C. This low-temperature MP transforms to high-temperature MP when the temperature is increased beyond 200°C. The luminescent properties of the BiPO₄:Eu³⁺ particles were studied using an excitation wavelength of 270 nm. The emission spectra display the bands associated with the ⁵D₀ → ⁷F _J (J = 1, 2, 3, and 4) electronic transitions of the Eu³⁺ cations. The intensity of the emission spectra increases with increasing hydrothermal temperature. These results demonstrate that BiPO₄:Eu³⁺ with different phases can be obtained through the hydrothermal method, which may enrich the solution chemistry for preparation of advanced materials with tailored functionality.     

Spin-orbit interaction of charge carriers with impurities in aligned Ge<Subscript>0.99</Subscript>Me<Subscript>0.01</Subscript> (Me = Mn,Cr, Co,Fe) nanowires

Aligned Ge_0.99Me_0.01 (Me = Mn, Cr, Co, Fe) nanowires have been investigated by electron spin resonance (ESR). Resonance lines corresponding to a magnetically ordered subsystem of localized spins (clusters of Ge alloys with transition metals) and an asymmetric Dysonian line, corresponding to the ESR of charge carriers in Ge, are identified in the ESR spectra. A systematic decrease in the effective g factor of the asymmetric Dysonian line with enhancement of spin-orbit interaction is found in the series of transition-metal ions Mn²⁺, Cr²⁺, Fe³⁺, and Co²⁺, which were used to dope Ge nanowires.