0D Cs3Cu2X5 (X = I,Br, and Cl) Nanocrystals: Colloidal Syntheses and Optical Properties

0D lead‐free metal halide nanocrystals (NCs) are an emerging class of materials with intriguing optical properties. Herein, colloidal synthetic routes are presented for the production of 0D Cs₃Cu₂X₅ (X = I, Br, and Cl) NCs with orthorhombic structure and well‐defined morphologies. All these Cs₃Cu₂X₅ NCs exhibit broadband blue‐green photoluminescence (PL) emissions in the range of 445–527 nm with large Stokes shifts, which are attributed to their intrinsic self‐trapped exciton (STE) emission characteristics. The high PL quantum yield of 48.7% is obtained from Cs₃Cu₂Cl₅ NCs, while Cs₃Cu₂I₅ NCs exhibit considerable air stability over 45 days. Intriguingly, as X is changed from I to Br and Cl, Cs₃Cu₂X₅ NCs exhibit a continuous redshift of emission peaks, which is contrary to the blueshift in CsPbX₃ perovskite NCs.     

Systemes CuX (X = Cl,Br)HgS. etude des composes CuHgSX (X = Cl,Br)

Powder samples of CuHgSCl and CuHgSBr have been synthesized, they crystallize in an orthorhombic structure, space group Pbam. The structure is built up of a three dimensional network of SHgS chains in z = 0 planes connected together with CuS₂X₂ (X = Cl, Br) tetrahedrons. S and X atoms build up a distorted cubic centered lattice.     

Cu magic angle spinning (MAS) nuclear magnetic resonance (NMR) study of CuX crystals (X=Cl, Br, and I) and CuX-based glasses (X=Cl, Br, and I)

⁶³Cu MAS NMR spectra of CuX crystals (X=Cl, Br, and I) and CuX-based glasses (X=Cl, Br, and I) have been measured. The CuCl and CuI crystals gave the isotropic chemical shift values around 0 ppm, and the CuBr crystal, around −55 ppm. The peak positions of the chlorocuprate(I), bromocuprate(I), and iodocuprate(I) glasses were very close to those of the CuX crystals, respectively. This result indicates that these glasses mainly consist of CuX₄ tetrahedra (X=Cl, Br, and I). The halogen coordination environments around Cu⁺ in bromochlorocuprate(I) glasses were dependent on the kind of modifying cation and the Br⁻/(Cl⁻+Br⁻) ratio. The bromochlorocuprate(I) glasses were mainly composed of CuCl_mBr_4−m or CuCl_nBr_4−n tetrahedra (m=0, 1, 2, and 4; n=0, 1, and 4).     

New halide glasses of the CdX2-PbX2-KI (X=Cl,Br) systems

The glass forming regions and some properties of the CdBr₂-PbBr₂-KI (10 to 50 mol % CdBr₂, 10 to 70 mol % PbBr₂, 20 to 40 mol % KI), CdCl₂-PbBr₂-KI (10 to 50 mol % CdCl₂, 10 to 80 mol % PbBr₂, 10 to 70 mol % KI) and CdCl₂-PbCl₂-KI (20 to 50 mol % CdCl₂, 10 to 70 mol % PbCl₂, 5 to 60 mol % KI) ternary systems were studied. Glasses exhibit remarkably high transmittance (up to 80%) in the visible and IR region (down to 250 cm^–1 for CdBr₂-PbBr₂-KI, 300 cm^–1 for CdCl₂-PbBr₂-KI and 400 cm^–1 for CdCl₂-PbCl₂-KI for 1 mm thick plates). The values of glass transition temperature lie between 343 to 353 K and crystallization temperature between 343 to 403 K.     

Remarkable Piezophoto Coupling Catalysis Behavior of BiOX/BaTiO3 (X = Cl,Br, Cl0.166Br0.834) Piezoelectric Composites

Polarization field engineering of piezoelectric materials is considered as an advisable strategy in fine‐tuning photocatalytic performance which has drawn much attention recently. However, the efficient charge separation that determines the photocatalytic reactivities of these materials is quite restricted. Herein, a judicious combination of piezoelectric and photocatalytic performances of BiOX/BaTiO₃ (X = Cl, Br, Cl_0.166Br_0.834) to enable a high piezophotocatalytic activity is demonstrated. Under the synergic advantages of chemical potential difference and piezoelectric potential difference in BiOX/BaTiO₃ composites, the photoinduced carriers recombination is largely halted, which directly contributes to the significantly promoted piezophotocatalytic activity of piezoelectric composites. Inspiringly, the BiOBr/BaTiO₃ composites under light irradiation with auxiliary ultrasonic activation result in an ultrahigh and stable photocatalytic performance, which is much higher than the total of those by isolated photocatalysis and piezocatalysis, and can rival current excellent photocatalytic system. In fact, the theoretical piezoelectric potential difference of BiOBr/BaTiO₃ composites reaches 100 mV, which far exceeds the pure BaTiO₃ of 31.21 mV and BiOBr of 30 mV, respectively. First, fabrication of BiOX/BaTiO₃ piezoelectric composites and its remarkable piezophoto coupling catalysis behavior lays new ground for developing high‐efficiency piezoelectric photocatalysts in purifying wastewater, killing bacteria, and other piezophototronic processes.     

PbX2（X：I,Br,Cl）基非氟卤化物玻璃的形成行为

为了获得具有实用意义的非氟卤化物玻璃，有必要探索新的玻璃形成系统，本文获得了 新的Ｃ ＰｂＸ２（Ｘ：Ｉ，Ｂｒ，Ｃｌ）为基质的三元非氟卤化物玻璃形成系统，并且首次发现ＰｂＩ２可以单独形成玻璃，所得的三元玻璃形成系统均表现出了良好的玻璃形成能力，此外，还从晶体结构，化学键的特怀，离了半径应电负性等角度探讨了各卤化物在玻璃形成过程中所坊的作用，结果表明，这些因素对玻璃形成均具有重要的作用。     

Structural, Spectroscopic Studies and Magnetic Properties of Doped Sillenites-Type Oxide Bi12[M]O20 M=Fe, Co

Layered structure of sillenites-type oxides Bi₁₂MO₂₀, the M position can be occupied by tetravalent or trivalent cations. This study focuses in Bi₁₂MO₂₀, M=Co, Fe, and Co/Fe, polycrystalline samples which are prepared by the solid-state reaction method. Infrared (IR) optical absorption, Raman scattering, and Foner magnetometer (BS2) techniques were used for systematic characterization of sillenite type oxide. IR and Raman scattering results showed the appearance of a band, at 850 cm^?1 and at 680 cm^?1, attributed to the (MO₄)^?3. Magnetic susceptibility measurements of all samples were done in a temperature range 2–300 K. The interaction of the M cations with each other through M–O–M linkages of approximately 180^° is expected to be dominant, and this would be paramagnetic in nature.     

Electrical relaxation of superionic conducting glasses AgX-AgPO3 (X=I,Br, Cl)

The complex impedance of superionic conducting glasses (AgX)_0.3-(AgPO₃)_0.7 (X = I, Br, Cl) was measured in the frequency range 5 Hz–500 kHz and temperatures between 299 K and 348 K. The frequency dependence of (the real part of complex conductivity) shows two regions: low and high frequencies. The first is attributed to the electrode-electrolyte polarization, while the second is attributed to the bulk conduction. The replacement of AgCl by AgBr or Agl at the same molar fraction is found to improve the bulk conductivity of the studied glasses. The electrical conductivity spectra exhibit one relaxation peak associated with dielectric loss which arises from the thermally activated jumps of Ag⁺ ions. The dependence of the relaxation time upon the halogen type is discussed in terms of the structural aspects, where the silver halides tend to form microdomains. The special characteristic of fast ionic conduction depending upon halide type is emphasized.     

Conduction mechanism in composite solid electrolytes,PbX 2-Al2O3 (X = Cl,Br, l) systems

Composite solid electrolytes PbX ₂-Al₂O₃ (X=Cl, Br, l) have been synthesized by the powder metallurgical process, and investigated by complex impedance analysis. X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscope (SEM) techniques. The phase analyses reveal that the composites are two-phase systems. No chemical reaction nor solid solution formation takes place between Al₂O₃ and the respective matrix phases. SEM photomicrographs show that Al₂O₃ particles are uniformly dispersed in the matrix phase for various systems. While PbCl₂-Al₂O₃ and PbBr₂-Al₂O₃ composites show a decrease in conductivity over their respective pure phases; Pbl₂-Al₂O₃ composites exhibit enhanced conductivity. By using the known diffusion and mobility data of the mobile species it has been shown that enhancement in conductivity is possible only in case of Pbl₂.     

基于BiOX(X=Cl、Br、I)新型高性能光催化材料的最新研究进展

铋系半导体BiOX(X=Cl、Br、I)因其独特的层状结构和合适的禁带宽度而表现出优异的光催化活性与稳定性, 已成为光催化材料领域极具应用前景的材料体系。本文首先针对BiOX(X=Cl、Br、I)光催化材料研究中的关键科学问题进行了深入分析, 进一步综述了国内外解决上述关键问题所采取的有效措施, 包括: 微结构调控、半导体复合、贵金属沉积、离子掺杂和表面敏化等, 并针对纳米结构BiOX(X=Cl、Br、I)负载于合适载体上实现固载的研究进展进行了概述, 从而对基于BiOX(X=Cl、Br、I)新型高性能光催化材料的最新研究进展进行了全面深入的综述, 最后展望了BiOX光催化材料的研究方向与趋势。     

Synthesis and transformation of zero-dimensional Cs3BiX6 (X = Cl,Br) perovskite-analogue nanocrystals

The unique structure of zero-dimensional (0D) perovskite-analogues has attracted a great amount of research interest in recent years. To date, the current compositional library of 0D perovskites is largely limited to the lead-based Cs₄PbX₆ (X = Cl, Br, and I) systems. In this work, we report a new synthesis of lead-free 0D Cs₃BiX₆ (X = Cl, Br) perovskite-analogue nanocrystals (NCs) with a uniform cubic shape. We observe a broad photoluminescence peak centered at 390 nm for the 0D Cs₃BiCl₆ NCs at low temperatures. This feature originates from a self-trapped exciton mechanism. In situ thermal stability studies show that Cs₃BiX₆ NCs remain stable upon heating up to 200 °C without crystal structural degradation. Moreover, we demonstrate that the Cs₃BiX₆ NCs can transform into other bismuth-based perovskite-analogues via facile anion exchange or metal ion insertion reactions. Our study presented here offers the opportunity for further understanding of the structure-property relationship of 0D perovskite-analogue materials, leading toward their future optoelectronic applications.

     

Resource‐Efficient Low‐Temperature Synthesis of Microcrystalline Pb2B5O9X (X = Cl,Br) for Surfaces Studies by Optical Second Harmonic Generation

Optically nonlinear Pb₂B₅O₉X (X = Cl, Br) borate halides are an important group of materials for second harmonic generation (SHG). Additionally, they also possess excellent photocatalytic activity and stability in the process of dechlorination of chlorophenols, which are typical persistent organic pollutants. It would be of great interest to conduct in situ (photo‐) catalysis investigations during the whole photocatalytic process by SHG when considering them as photocatalytic materials. In order to get superior photocatalytic efficiency and maximum surface information, small particles are highly desired. Here, a low‐cost and fast synthesis route that allows growing microcrystalline optically nonlinear Pb₂B₅O₉X borate halides at large quantities is introduced. When applying the ionothermal growth process at temperatures between 130 and 170 °C, microcrystallites with an average size of about 1 µm precipitate with an orthorhombic hilgardite‐like borate halide structure. Thorough examinations using powder X‐ray diffraction and scanning electron microscopy, the Pb₂B₅O₉X microcrystals are indicated to be chemically pure and single‐phased. Besides, the Pb₂B₅O₉X borate halides' SHG efficiencies are confirmed using confocal SHG microscopy. The low‐temperature synthesis route thus makes these borate halides a highly desirable material for surface studies such as monitoring chemical reactions with picosecond time resolution and in situ (photo‐) catalysis investigations.     

Preparation and luminescence of Pb2OFX; X=Cl,Br, I

The title compounds were prepared and crystallized with the ideal Perite structure. Low temperature luminescence spectra are presented.     

Conductivite ionique dans les verres LiPO3LiX (X = I,Br, Cl)

The glass-forming regions in the systems LiPO₃LiX with X = I, Br, Cl were determined and the study of the electrical conductivity of glasses belonging to these systems was carried out. The conductivity increases with increasing halogen ion size and reaches maxima values of the order of 10^?6, 3, 2 10^?7, 10^?7 (ohm cm)^?1 at 25° C with LiI, LiBr, LiCl respectively : they are obtained at the limit of glass forming region. The Raman spectra do not show any modifications. The study of the electrical conductivity shows that the conduction is essentially ionic in nature.     

{[Cd(Ⅱ)L(NCS)2](DMF)2}n(L=1,4-二[2-(2-吡啶基)苯并咪唑基]丁烷)的合成,晶体结构与荧光光谱研究

合成了一种新的包含咪唑基团的双端四齿鳌合配体1,4-二[2-(2-吡啶基)苯并咪唑基]丁烷,并用其作为桥联配体与金属离子共同构筑配位聚合物.用Cd2 金属离子和L在DMF/H2O混合溶液中,存在KSCN的条件下,合成一种新型的一维链状配位聚合物{[Cd(Ⅱ)L(NCS)2](DMF)2}n(L=1,4-二[2-(2-吡啶基)苯并咪唑基]丁烷).单晶X-射线分析仪分析表明,该晶体属三斜晶系,P-1空间群,晶胞参数为:a=8.869(1)A,b=11.278(2)A,c=19.328(4)A,α=89.83(3)°,β=89.52(3)°,γ=74.28(3)°,V=1860.9(7)(A)3,Z=2,7250个独立衍射点中,6039个可观测点满足F2≥2σ(F2o),R=0.0543,wR2=0.1442.它是由一维的锯齿形链[Cd(Ⅱ)L(NCS)2]n和游离的DMF分子组成.在链内金属原子与来自于2个具有不同结构的配体L中的4个N原子和2个SCN-阴离子中的2个N原子形成八面体配位.该固态配合物在室温下用389nm的紫外光激发时在453nm处发射出强的荧光.