M_3(PO_4)_2(M=Sr,Ba)中 Ce~(3 )和 Tb~(3 )的发光

引言近来,我们报道了几种基质晶格中 Tb~(3 )的发光。特别强调了是什么因素决定 Tb~(3 )发光颜色的问题。通常,Tb~(3 )的发光是由于~5D_3和~5D_4能级的作用。~5D_3能级的发射是一般所说的蓝光发射,~5D_4能级的发射则是一般所说的绿光发射,因为事实上主发光线分别在蓝色和绿色光谱区。决定~5D_3和~5D_4发射强度比的主要因素是 Tb~(3 )的浓度。就大部分固态基质晶格而言,从~5D_3到~5D_4的无幅射多声子弛豫的可能性相当低。     

MnQ2 ( Q =S ,Se,Te)and [Mn(en) 3]Te4StructuresandTheir

The solvo-thermal technique is used for the synthesis of Te 4 (I).The crystal structure has been determined by single crystal X-ray diffraction techniques.The crystal belongs to the monoclinic, space group p 2 1/ c with unit cell: a =0.846 1(1), b =1.565 3(2), c =1.426 9(2) nm, α =90°, β =91.37(1) (3)°, γ =90°, V =1.889 3(4) nm 3,and Z =4.The results show that the structure contains a linear chain Zintl anion, 2- and a complex cation, 2+ . Optical studies have been performed on the powder sample of I, suggesting that the compound is a semiconductor with a band gap of 0.73 eV. The semiconductor properties for MnQ 2(Q=S,Se,Te) and Te 4 have been discussed by molecular orbital theory.     

AC conductivity of nanoparticles CoxFe(1−x)Fe2O4 (x=0, 0.25 and 1) ferrites

Nanoparticles of Co_xFe_(1−x)Fe₂O₄ (x=0, 0.25 and 1) were prepared by the chemical co-precipitation method. X-ray diffraction and scanning electron microscopy were used to determine the average particle size and morphology of the prepared samples. AC conductivity is found to vary as ω^s in the frequency range 42–5×10⁶ Hz. The impedance analysis reveals that low conductivity and high impedance values are observed at low temperatures. The Nyquist impedance plots of the present investigation clearly depict the inherent phenomenon involved in the conduction mechanism of Co doped Fe₃O₄ ferrites. Regarding frequency dependence of Co_xFe_(1−x)Fe₂O₄ AC conductivity the observed behavior clearly indicates that the present ferrites are semiconductor-like.     

Visible light assisted photocatalytic activity of TiO2–metal vanadate (M=Sr,Ag and Cd) nanocomposites

TiO₂–metal vanadate nanocomposites (TiO₂–MV) were synthesized by the precipitation method and successfully characterized using UV–visible diffuse reflectance spectroscopy (UV–vis-DRS), powder X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) techniques. The photocatalytic activity of TiO₂–MV was investigated for the degradation of fast green (FG) dye under visible light irradiation. The photocatalytic activity of TiO₂–silver vanadate [TiO₂–Ag₃VO₄] was found to be much higher than that of TiO₂–cadmium vanadate [TiO₂–CdV₂O₆], TiO₂–strontium vanadate [TiO₂–Sr₃(VO₄)₂] and TiO₂. The effect of operational parameters such as pH, photocatalyst concentration and initial dye concentration on the photodegradation of FG was examined in detail. The mineralization of FG was confirmed by chemical oxygen demand (COD) and total organic carbon (TOC) measurements. Moreover, TiO₂–Ag₃VO₄ was found to be a reusable photocatalyst.     

Uncovering Original Z Scheme Heterojunctions of COF/MOx (M = Ti,Zn, Zr,Sn, Ce,and Nb) with Ascendant Photocatalytic Selectivity for Virtually 99.9% NO-to-NO3− Oxidation

Novel Covalent organic skeleton/metal oxide (COF/MO_x; M = Ti, Zn, Zr, Sn, Ce, Nb) Z scheme heterojunction is constructed to achieve highly selective oxidation of nitric oxide (NO). Under visible-light irradiation, the optimized COF/TiO₂ (CF/TS0.05) catalyst showed an excellent NO removal rate (64.5%), resulting from the improvement of light absorption performance, the separation efficiency of photoexcited electron-hole pairs, and O₂ activation due to the uniform coating of COF. Meanwhile, the electrons are captured by the adsorbed oxygen to effectively render into superoxide radicals as the main active species, and the corresponding holes are retained at the complex interface due to the hydrophobic COF coating, which extremely reduced the ability of activated water to produce hydroxyl radicals and limited the production of intermediate nitrogen dioxide (NO₂), thereby improving the oxidation selectivity toward nitrate (NO₃⁻) at 99.9% in the Z scheme heterojunction. More importantly, other COF/MO_x catalysts also exhibited superior selectivity and activity, meaning that this scheme is credited with universality. In short, this study reveals that the generation of only one main reactive oxygen species is enhanced by reasonable control of electron-hole pair in the new Z scheme heterojunction to significantly increase photocatalytic performance and selectivity.     

Copoly[6,6′-bis(9-(2-ethylhexyl)carbazole-3-yl)/thieno-(2,5-b)thiophenylidenevinylene]-based photorefractive composite: A comparative study on conjugated and non-conjugated polymer systems

Photoconductivity and birefringence are two important factors that affect performances of photorefractive devices. Here, the optical properties of this composite based on copoly[6,6′-bis(9-(2-ethylhexyl)carbazole-3-yl)/thieno-(2,5-b)thiophenylidenevinylene] as photoconducting material, 2-[3-[(E)-2(piperidine)-1-ethenyl]-5,5-dimethyl]-2-cyclohexenyliden]malononitrile as nonlinear optical chromophore, butyl benzyl phthalate as plasticizer and C₆₀ as photosensitizer, has been compared to those of the corresponding non-π-conjugated polymer composite. The 50-μm thick photorefractive composite showed a diffraction efficiency 37.2% at 50 V/μm, which corresponded to a Δn of 2.62 × 10^?3. When we compare the speeds of the current and the non-conjugated analogue composites, the current composite has about a factor of seven larger speeds due to the π-conjugated polymer backbone. We also discuss and present simple explanation of the observed effect.     

Arsenic vapor pressure dependence of surface morphology and silicon doping in molecular beam epitaxial grown GaAs (n11)A (n=1–4) substrates

Surface morphology of undoped AlGaAs/GaAs asymmetric double quantum wells (ADQWs) and Si-doped single epitaxial GaAs layers were studied by atomic force microscopy. Samples were prepared on GaAs(n11)A (n=1–4) substrates in molecular beam epitaxy at different As pressures and the same substrate temperature and Ga flux. The surfaces of (n11)A ADQWs change from rough to smooth and featureless with increasing As pressures, while that of (100) sample shows an inverse change according to the atomic force microscopy results. Triangular pyramidal facets were observed at lower As pressure for (111)A and (211)A orientations. The interface roughness of ADQWs was improved at higher As pressure showing by a transmission electron microscope observation. The conduction type of (n11)A (n<=4) was p-type for lower As pressure and n-type for higher As pressure.     

Semiconducting Transport in Pb10−XCux(PO4)6O Sintered from Pb2SO5 and Cu3P

The recent claim on the discovery of ambient-pressure room-temperature superconductivity in Cu-doped lead-apatite has attracted sensational attention. The intriguing compound has been fabricated by sintering lanarkite (Pb₂SO₅) and copper(І) phosphide (Cu₃P). To verify this exciting claim, Pb₂SO₅, Cu₃P, and finally the modified lead-apatite Pb_10−xCu_x(PO₄)₆O have been successfully synthesized. Detailed electrical transport and magnetic properties of these compounds are systematically analyzed. It turns out that Pb₂SO₅ is a highly insulating diamagnet and Cu₃P is a paramagnetic metal. The obtained nominal Pb_10−xCu_x(PO₄)₆O compound sintered from Pb₂SO₅ and Cu₃P exhibits semiconductor-like transport behavior with a large room-temperature resistivity of ≈1.94 × 10⁴ Ω·cm, although the major phase of the compound shows consistent X-ray diffraction spectrum with the previously reported structure data. In addition, when a Pb_10−xCu_x(PO₄)₆O pellet pressed from uniformly ground powder is located on top of a commercial Nd₂Fe₁₄B magnet at room temperature, no repulsion can be felt and no magnetic levitation is observed either. The large difference in electrical and magnetic properties between the compounds and the previously reported compounds might be induced by distinct fine crystallographic structures, diverse multi-phase distributions, and different concentrations of impurity phases such as Cu₂S, all of which deserve further study.     

铁电材料的新族:A_2BMO_3F_3■和M=Mo、W时,A、B=K、Rb、Cs)

实验证明分子式为K_3MO_3F_3、Rb_MO_3F_3、C_sMO_3F_3、Rb_2KMO_3F_3和Cs_2RbMO_3F_3(M=M_o、W)的材料的介电、热电、量热和结晶性质与铁电性一致。在78K以上,这些材料的前七种呈现两次相变,后三种为一次相变。介电常数最大值仅与高温相变T_2有关。在T_2以上,在点群m3m中是顺电结构;在T_2以下,在点群3中是铁电结构。在低相变温度以下,可能的点群是3或1。     

Ca3(PO4)2:RE3+ (RE=Eu,Dy,Ce,Tb) 荧光粉的制备及其发光特性

采用高温固相法合成了Ca3(PO4)2:RE3+(RE = Eu, Dy, Ce, Tb)系列发光材料,研究了其发光性质。研究表明Ca3(PO4)2: RE3+ 在紫外区域均能有效被激发,有很强的荧光发射,且发光范围覆盖蓝到红光波段,是一类可以紫外激发实现白光LED用的潜在荧光粉。在0.005到0.03 mol 浓度范围内,Eu,Dy和Ce掺杂的荧光粉的发光都发生了浓度淬灭,分别对应于0.025,0.025和0.02 mol,而Tb3+掺杂的样品的表现出高的发光淬灭浓度。     

A New Candidate in Polyanionic Compounds for Potassium Ion Battery Anode: MXene Derived Carbon Coated π-Ti2O(PO4)2

Intercalation-type reaction that occurs in polyanion materials is considered to be a facile way to counter the mismatched relationship between the large K⁺ and compact host structure for potassium ion batteries (PIBs). However, the large “dead” weight and poor conductivity introduced by the polyanion framework severely limit the electrochemical performance of polyanion anodes. Herein, a new rigid K⁺ host of 1D π-Ti₂O(PO₄)₂ with carbon-coated (TOP@C) is simply synthesized through a simple Ti₃C₂T_x-derived method. The density functional theory (DFT) calculations and experimental results show that the potassium storage properties are unquestionably improved by the small cell volume change during cycling, the intercalation pseudo-capacitance energy storage mechanism, and the large K-storage tunnels with lower migration energy (0.23 eV) of TOP@C anode (134.5 mAh g^-1 after 2000 cycles at 1.0 A g^-1). The TOP@C//PTCDA full batteries, which clearly illustrate their promising application in advanced PIBs, successfully achieved a high energy density of 119.4 Wh kg^-1 and a power density up to 632.8 W kg^-1 with regard to the total mass of TOP@C and PTCDA.     

Fe?N4O?C Nanoplates Covalently Bonding on Graphene for Efficient CO2 Electroreduction and Zn?CO2 Batteries (Adv. Funct. Mater. 27/2023)

Electrochemical carbon dioxide (CO₂) reduction into value-added products holds great promise in moving toward carbon neutrality but remains a grand challenge due to lack of efficient electrocatalysts. Herein, the nucleophilic substitution reaction is elaborately harnessed to synthesize carbon nanoplates with a Fe N₄O configuration anchored onto graphene substrate (Fe N₄O C/Gr) through covalent linkages. Density functional theory calculations demonstrate the unique configuration of Fe N₄O with one oxygen (O) atom in the axial direction not only suppresses the competing hydrogen evolution reaction, but also facilitates the desorption of *CO intermediate compared with the commonly planar single-atomic Fe sites. The Fe N₄O C/Gr shows excellent performance in the electroreduction of CO₂ into carbon monoxide (CO) with an impressive Faradaic efficiency of 98.3% at −0.7 V versus reversible hydrogen electrode (RHE) and a high turnover frequency of 3511 h⁻¹. Furthermore, as a cathode catalyst in an aqueous zinc (Zn)-CO₂ battery, the Fe N₄O C/Gr achieves a high CO Faradaic efficiency (≈91%) at a discharge current density of 3 mA cm⁻² and long-term stability over 74 h. This work opens up a new route to simultaneously modulate the geometric and electronic structure of single-atomic catalysts toward efficient CO₂ conversion.     

Two new D–A conjugated polymers P(PTQD-Th) and P(PTQD-2Th) with same 9-(2-octyldodecyl)-8H-pyrrolo[3,4-b]bisthieno[2,3-f:3′,2′-h]quinoxaline-8,10(9H)-dione acceptor and different donor units for BHJ polymer solar cells application

We report the synthesis, characterization and photovoltaic properties of bulk heterojunction polymer solar cells of new donor–acceptor conjugated copolymers P(PTQD-Th) and P(PTQD-2Th) that incorporate same strong 9-(2-octyldodecyl)-8H-pyrrolo[3,4-b]bisthieno[2,3-f:3′,2′-h]quinoxaline-8,10(9H)-dione as strong acceptor and different weak thiophene (Th) and bi-thiophene (2Th) as donors, respectively. Both the copolymers showed suitable unoccupied lowest molecular orbital (LUMO) energy levels, compatible with the LUMO of PC₇₁BM for efficient electron transfer from copolymer to PC₇₁BM in the blended copolymer: PC₇₁BM thin films. Moreover the deeper highest occupied molecular orbital (HOMO) energy levels of both copolymers ensures the high open circuit voltage (V_oc) of the BHJ polymer solar cells. The optimized P(PTQD-Th):PC₇₁BM and P(PTQD-2Th):PC₇₁BM with weight ratio of 1:2 processed with chloroform solvent showed PCE of 3.65% and 3.96%, respectively. The higher value of J_sc for the device processed with P(PTQD-2Th):PC₇₁BM as compared to that for P(PTQD-Th):PC₇₁BM, attributed to narrower optical bandgap and broader absorption profile for P(PTQD-2Th) as compared to P(PTQD-Th). The PCE values of polymer solar cells were further improved (5.54% and 5.67% for P(PTQD-Th):PC₇₁BM and P(PTQD-2Th):PC₇₁BM, respectively) when small amounts of solvent additive, i.e. 1,8-diiodoctane (DIO) were used for the processing of active layers. The improved PCE has been attributed to both the enhanced values of short circuit current (J_sc) and fill factor (FF) due to the better nanomorphology and charge transport, induced by the high boiling point of solvent additive.     

Light emitting diodes for the spectral range λ=3.3–4.3 µm fabricated from InGaAs and InAsSbP solid solutions: Electroluminescence in the temperature range of 20–180°C (Part 2)

Light-emitting diodes (LEDs) based on p-n homo-and heterostructures with InAsSb(P) and InGaAs active layers have been designed and studied. An emission power of 0.2 (λ=4.3 µm) to 1.33 mW (λ=3.3 µm) and a conversion efficiency of 30 (InAsSbP, λ=4.3 µm) to 340 mW/(A cm²) (InAsSb/InAsSbP double heterostructure (DH), λ=4.0 µm) have been achieved. The conversion efficiency decreases with increasing current, mainly owing to the Joule heating of the p-n homojunctions. In DH LEDs, the fact that the output power tends to a constant value with increasing current is not associated with active region heating. On raising the temperature from 20 to 180°C, the emission power of the (λ=3.3 and 4.3 µm) LEDs decreases, respectively, 7-and 14-fold, to become 50 (at 1.5 A) and 7 µW (at 3 A) at 180°C.     

The adsorption of basic dye (Alizarin red S) from aqueous solution onto activated carbon/γ-Fe2O3 nano-composite: Kinetic and equilibrium studies

The adsorption behavior of Alizarin red S (ARS) from aqueous solution onto magnetic activated carbon (MAC) nano-composite was investigated under various experimental conditions. Characterization of the obtained MAC nano-composite was achieved by FT-IR, BET, FE-SEM, EDX, XRD and VSM techniques. The influence of variables including pH, concentration of the dye, amount of adsorbents and contact time was investigated by the batch method. High maximum adsorption capacity was obtained at 108.69 mg g⁻¹ for ARS. The equilibrium data was evaluated using Langmuir and Freundlich isotherm. The Langmuir model best describes the uptake of ARS dye, which implies that the adsorption of ARS dye onto MAC nano-composite is homogeneous. The kinetic data were analyzed using Lagergren pseudo-first order and pseudo-second equation. The pseudo-second order exhibited the best fit for the kinetic studies (R²=0.9999), which indicates that adsorption of ARS is limited by chemisorption process. This study shows that the as-prepared MAC composite could be utilized as an efficient, magnetically separable adsorbent for the environmental cleanup.     

Grain Boundaries in Cu(In,Ga)Se2: A Review of Composition–Electronic Property Relationships by Atom Probe Tomography and Correlative Microscopy

Cu(In,Ga)Se₂ thin-film solar cells have attracted significant research interest in recent decades due to their high efficiency in converting solar energy into electricity for enabling a sustainable future. Although the Cu(In,Ga)Se₂ absorber can be grown as a single crystal, its polycrystalline form is dominating the market not only due to its lower costs, but also due to its unexpectedly higher cell efficiency. However, this absorber contains a high fraction of grain boundaries. These are structural defects where deep-trap states can be localized leading to an increase in recombination activity. This controversy is mirrored in the existing literature studies where two main contradictory believes exist: 1) to be crucial grain boundaries in Cu(In,Ga)Se₂ absorber are anomalous, being benign in terms of cell performance, and 2) grain boundaries are regions characterized by an increased recombination activity leading to deteriorated cell performance. Therefore, the present review tackles this issue from a novel perspective unraveling correlations between chemical composition of grain boundaries and their corresponding electronic properties. It is shown that features such as Cu depletion/In enrichment, segregation of 1-2at.% of alkali dopants, and passivation by a wide-bandgap or type inversion at grain boundaries are crucial ingredients for low open-circuit voltage loss and, hence, for superior cell performance.