Owing to quantum confinement, low-dimensional hybrid perovskite materials have recently shown a great potential for applications in optoelectronics. Such compounds can exhibit broad-or narrow-band light emission, lowtemperature solution processability, high thermal stability, and relatively high photoluminescence quantum yields (PLQY). However, the search for efficient phosphors with a specific set of characteristics remains difficult because the family of hybrid perovskites consists in an extremely large chemical system (i.e., different halides, metals, and organic molecules), and optical properties are not predictable prior to material synthesis and characterization. Here, is proposed a simple approach to screen a significant amount of new hybrid lead halide perovskites. The synthetic method by fast crystallization at low temperature enables the rapid identification of the materials exhibiting the targeted photoluminescence properties. This approach is tested for the discovery of hybrid lead halide perovskites with efficient white-light emission. Among 100 newly synthesized compounds, 5 exhibit intense white emission, and the in-depth characterization of a selected candidate shows high color rendering index (CRI) = 78 and a PLQY of 9%, which is equivalent to the record reported for hybrid perovskites. This compound exhibits a new structure type for warm white-light emitting hybrid perovskites with chains of corner-sharing PbX 6 .
New assemblies based on the archetypal [IrIII(ppy)2(bpy)]+ complex and a series of polyoxometalates exhibit highly tunable phosphorescence and vapoluminescence properties for detection of volatile organic compounds.
A color-tunable phosphor Li 2 SrSiO 4 :Eu 2+ ,Eu 3+ ,Ce 3+ was synthesized by solid state reaction in reducing atmosphere followed by a controlled heating treatment of the compound in air at different temperatures. Due to the different temperatures of oxidation of Eu 2+ into Eu 3+ and Ce 3+ into Ce 4+ , Eu 2+ / Eu 3+ / Ce 3+ / Ce 4+ ions can coexist in the Li 2 SrSiO 4 host and enable a tunable coloration of the "blue-yellow-red" photoemission to obtain white luminescence.
Rare earth-based inorganic phosphors are of great interest for solid-state lighting because some of them present very efficient luminescence properties. However, their performances strongly depend on several parameters. For multivalent dopants such as cerium, a widely used activator in the lighting industry, a synthesis in reducing atmosphere is often required to stabilize the dopant in its lower oxidation state. Surprisingly, this crucial step is not much considered, and the presence of the reduced state only is often assumed. However, the presence of the dopants oxidized form has been previously evidenced after such reductions. In this case, a question remains open about the impact of the Ce 3+ /Ce 4+ ratio on the materials optical properties. As an example, different CaSc 2 O 4 :Ce samples were prepared and their Ce 3+ /Ce 4+ ratios were probed by diffuse reflection and XANES. The evolution of their photoluminescence properties was investigated to rationalize the progressive reduction of dopants.
The physical properties of doped multifunctional compounds are commonly tuned by controlling the amount of dopants, but this control is limited because all the properties are influenced simultaneously by this single parameter. Here, we present a strategy that enables the fine-tuning of a specific combination of properties by controlling the reduction of dopants. The feasibility of this approach was demonstrated by optimizing the near-IR photoluminescence of strontium titanate SrTiO :Ni for potential applications in biomedicine for a range of absorbance in the visible/near-IR region. We discussed how material properties, such as luminescence, conductivity, or photocatalytic properties can be designed by carefully controlling the ratio of dopants in different oxidation states.
Herein we report a joint experimental and theoretical investigation on two tetranuclear Cu(I) clusters stabilized by halide ligands. These clusters are of high interest due to their spectroscopic and optical properties, more precisely both clusters exhibit thermochromism. The compounds synthesized by the hydrothermal method have been characterized by single-crystal X-ray diffraction, UV-visible spectroscopy and quantum calculations. Modeled structures have been investigated by means of DFT and TD-DFT methods. Anharmonic computations have been performed to better achieve the vibrational investigation. Computations of the triplet excited states permit us to get more insights into the structure and electronic structure of the excited states responsible for the luminescence properties. Calculations are in agreement with the observed phosphorescence wavelengths.
Chiral building units must pack into chiral crystal structures. However, chiral structures can also be induced from achiral building units. In this letter, the later well-known phenomenon is illustrated with the simple synthesis of a new chiral compound from commonly used achiral organic molecules. Thus, the new compound cyclohexylammonium sulfanilate was synthesized at room temperature and characterized by single crystal X-ray diffraction, spectroscopy (UV/Visible and FT-IR), and thermal analysis. The compound is chiral and crystallizes in orthorhombic system with space group P2 1 2 1 2 1. Noncentrosymmetry was confirmed by Second Harmonic Generation (SHG) measurements using solid potassium dihydrogenphosphate (KDP) as reference. The organic ions which form this chiral compound namely cyclohexylammonium (CyNH 3) and sulfanilate (NH 2 PhSO 3 À) are both low-cost achiral building units. A statistical investigation of previously reported structures shows that NH 2 PhSO 3 À stabilized by noncentrosymmetric cations more likely lead to noncentrosymmetric materials.
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