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. 相似文献
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 SHgS chains in z = 0 planes connected together with CuS2X2 (X = Cl, Br) tetrahedrons. S and X atoms build up a distorted cubic centered lattice. 相似文献
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 CuClmBr4−m or CuClnBr4−n tetrahedra (m=0, 1, 2, and 4; n=0, 1, and 4). 相似文献
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. 相似文献
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, Cl0.166Br0.834) 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. 相似文献
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. 相似文献
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. 相似文献
Composite solid electrolytes PbX2-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. 相似文献
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.
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. 相似文献
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. 相似文献