Giant Optical Activity and Second Harmonic Generation in 2D Hybrid Copper Halides.

Hybrid organic-inorganic metal halides have emerged as highly promising materials for a wide range of applications in optoelectronics. Incorporating chiral organic molecules into metal halides enables the extension of their unique optical and electronic properties to chiral optics. By using chiral (R)- or (S)-methylbenzylamine (R-/S-MBA) as the organic component, we synthesized chiral hybrid copper halides, (R-/S-MBA)2 CuCl4 , and investigated their optical activity. Thin films of this material showed a record anisotropic g-factor as high as approximately 0.06. We discuss the origin of the giant optical activity observed in (R-/S-MBA)2 CuCl4 by theoretical modeling based on density functional theory (DFT) and demonstrate highly efficient second harmonic generation (SHG) in these samples. Our study provides insight into the design of chiral materials by structural engineering, creating a new platform for chiral and nonlinear photonic device applications of the chiral hybrid copper halides.

Silica encapsulation of metal perovskite nanocrystals in a photoluminescence type display application.

Perovskite nanocrystals (PeNCs) are attractive in high-color gamut display technology as light converters which can achieve saturated green and red lights, respectively. However, PeNCs are intrinsically fragile against ambient conditions, such as moisture and oxygen and it is hard to maintain their performance in long-term operation. In this work, a new hierarchical encapsulation method is proposed, integrated with surface modification by halide ions protection, nano-scaled encapsulation by in situ capping SiO2 and embedding into poly (methyl methacrylate) (PMMA) matrix composites, to achieve a stable perovskite light converting composite sheet for LED remote-type encapsulation. The storage stability, as well as the operational stability of perovskite composites, were confirmed by the spectra evolution from encapsulated LEDs with normalized blue emission intensity. The 2D maps of spectra and aging measurement indicate that the silica encapsulation can well protect the PeNCs in the PMMA matrix from the ambient circumstance during a long-term storage process. Additionally, the hierarchical encapsulation for PeNCs/silica/PMMA showed better operational stability than the direct encapsulation of PeNCs/PMMA, and the correspondent Commission Internationale de L'Eclairage color coordinates tracking also indicated more stable color properties, which demonstrates the great potential in photoluminescent display applications.

[Spectroscopic properties of Er3+ : Ba0.65Sr0.35TiO nanopowders].

Ba0.65Sr0.35TiO2 (BST) nanopowders doped with Er3+ were prepared by sol-gel method. The absorption spectrum and photoluminescence (PL) spectrum of Er3+ : BST nanopowders was measured at room temperature. Based on the Judd-Ofelt theory, the intensity parameters of Er3+ in BST nanopowders were determined, omega2 = 0.993 x 10(-20) cm2, omega4 = 1.665 x 10(-20) cm2 and omega = 0.540 x 10(-20) cm2, and then the values of the line strengths, radiative transition probabilities and branching ratios of Er3+ were calculated. According to the PL spectrum, the emission bands centered at about 522, 545, 654 and 851 nm corresponding to 2H(11/2)-->4S(3/2-->4I(15/2), 4F(9/2)-->4I(15/2), and 4S(3/2-->4I(13/2) transition were observed, and the emission properties were also discussed. The results show that the Er3+ : BST nanomaterials are prospective candidates for applications in new photoelectric devices.

All-inorganic copper(i)-based ternary metal halides: promising materials toward optoelectronics.

All-inorganic lead halides, including CsPbX3 (X = Cl, Br, I), have become important candidate materials in the field of optoelectronics. However, the inherent toxicity of metal lead and poor material stability have hindered further applications of traditional metal halides, CsPbX3. Therefore, copper(i)-based ternary metal halides are expected to become promising substitutes for traditional metal halides because of their nontoxicity, excellent optical properties and good stability under ambient conditions. This article reviews the recent development of all-inorganic low-dimensional copper(i)-based ternary metal halides by introducing their various synthesis methods, crystal structures, properties and their optoelectronic applications. In addition, the prospects for future challenges and the potential significance of copper(i)-based ternary metal halides in optoelectronic fields are presented.

Chiral Transition Metal Oxides: Synthesis, Chiral Origins, and Perspectives.

Transition metal oxides (TMOs) consist of a series of solid materials, exhibiting a wide variety of structures with tunability and versatile physicochemical properties. Such a statement is undeniably true for chiral TMOs since the introduction of chirality brings in not only active optical activities but also geometrical anisotropy due to the symmetry-breaking effect. Although progressive investigations have been made for accurately controlled synthesis and relevant explanations on the chirality origin of such materials, the overall field of chiral TMOs is still in its infancy with adequate space for interdisciplinary communications and development. Herein, therefore, recent advances in both experimental phenomena and theoretical calculations in this area are reviewed, to elucidate the underlying chiral origin with respect to their fabrications process, triggering new insights for further evolution of this field.

From Molten Calcium Aluminates through Phase Transitions to Cement Phases.

Crystalline calcium aluminates are a critical setting agent in cement. To date, few have explored the microscopic and dynamic mechanism of the transitions from molten aluminate liquids, through the supercooled state to glassy and crystalline phases, during cement clinker production. Herein, the first in situ measurements of viscosity and density are reported across all the principal molten phases, relevant to their eventual crystalline structures. Bulk atomistic computer simulations confirm that thermophysical properties scale with the evolution of network substructures interpenetrating melts on the nanoscale. It is demonstrated that the glass transition temperature (T g) follows the eutectic profile of the liquidus temperature (T m), coinciding with the melting zone in cement production. The viscosity has been uniquely charted over 14 decades for each calcium-aluminate phase, projecting and justifying the different temperature zones used in cement manufacture. The fragile-strong phase transitions are revealed across all supercooled phases coinciding with heterogeneous nucleation close to 1.2T g, where sintering and quenching occur in industrial-scale cement processing.

Second-harmonic generation in IR-transparent beta-GeS2 crystallized glasses.

IR-transparent beta-GeS(2) crystallized glasses were fabricated by crystallization of the glass with a stoichiometric composition corresponding to target crystal and only beta-GeS(2) crystallites were precipitated. A clear second-harmonic generation was observed in the crystallized glasses by the Maker fringe technique. The optical nonlinear susceptibility, chi((2)), of beta-GeS(2) crystallized glasses was found to be ~7.3 pm/V, being comparable to that created by thermal/electric or other poling methods, which opens a new way to an optical converter operating in the mid-IR spectral region.