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Perovskite colloidal quantum dots (CQDs) enable a solution-processed approach toward lasers, simultaneously providing tunable wavelength, high quantum efficiency, large absorption cross-section, and long Auger lifetimes. However, broad-band single-mode lasers based on such CQDs have been proven to be challenging. Here we report broad-band single-mode lasers from solution-processed CsPbX3 (X = Cl, Br, I) CQDs based on a high-quality zinc oxide microrod hexagonal whispering-gallery microcavity. A typical single-mode laser with ultra-narrow linewidth (∼0.21 nm, quality factor ∼3000) at 11.7 μJ cm−2 was obtained at 636 nm based on the conformal deposition of CsPb(Br0.5I0.5)3 CQDs on an individual hexagonal zinc oxide microrod cavity with a radius of about ∼776 nm. Moreover, by tuning the halogen ratio, synthesis temperature and the size of the zinc oxide microrods, broad-band tunable single-mode lasers are obtained across the entire visible spectrum from 417 nm to 723 nm. These results represent a significant step towards easy solution-processed broad-band tunable single-mode lasers. [ABSTRACT FROM AUTHOR]

A series of novel phenylacetylene derivatives with two chiral centers, one of which was derived from l-phenylglycinol and the other from l- and d-alanine or l- and d-valine, were synthesized and polymerized in THF using Rh(nbd)BPh4 as a catalyst to obtain the corresponding stereoregular one-handed helical poly(phenylacetylene) derivatives (PPA-1a, PPA-1b, PPA-2a and PPA-2b). The polymers were used as chiral stationary phases (CSPs) in HPLC, and the effects of the coating solvents and configuration of the second amino acid groups on the helical conformation of the main chain and the enantioseparation were investigated. In DMF, CD intensities of PPA-1b and PPA-2b having R-configuration on the second chiral center were higher than those of PPA-1a and PPA-2a having S-configuration at the same position, indicating that PPA-1b and PPA-2b may possess more stereoregular helix senses. The chiral recognition abilities of these polymers obviously depended on the main chain helical conformation induced by different coating solvents and the chiral centers in the pendant. Some racemates were better resolved on PPA-1b and PPA-2b, especially the racemic 1-phenylprop-2-yn-1-ol (8) which could be better resolved on PPA-2b than on the well-known commercial chiral column AD-H. [ABSTRACT FROM AUTHOR]

Obtaining single-mode lasing with excellent stability and beam quality is highly desirable but still challenging. Although microplatelet optical cavities attract great attention because of their important lasing characteristics of directionality and high-power output light, they suffer from weak light confinement, which restricts applications of a single-mode laser. Herein, we increased the vertical thickness of the microplatelet cavity appropriately to achieve 3D light confinement in a CsPbBr3 micro-cubic cavity, from which single-mode lasing with an extreme narrow linewidth of 0.064 nm (Q∼ 8500) was successfully achieved at room temperature. Besides, the microcavity we prepared exhibits superb capability for the output of continuous stable single-mode lasing. Different growth stages of cavities were found and a related growth mechanism was analyzed, indicating that the micro-cubic cavities evolved from nanospheres. Moreover, interesting multi-mode lasing spectra with higher-order transvers modes were observed in larger micro-cubic cavities. All these results suggest that 3D CsPbBr3 micro-cubic cavities, which provide improved photo-physical properties, are important for fundamental studies and future applications in photonic devices. [ABSTRACT FROM AUTHOR]

We present the nonlinear optical properties of CsPb(Br/I)3 perovskite quantum dots (QDs) with high crystallinity. The perovskite QDs show better two-photon absorption response than the traditional metal chalcogenide QDs. And, the photoluminescence peak of the halogen vacancies in perovskite nanocrystals was experimentally observed for the first time. [ABSTRACT FROM AUTHOR]

Optical resonant modes in microwire cavities with irregular hexagonal cross-section have been observed in the visible spectral range. Single-crystalline In2O3 microwire functioning as a promising semiconductor microcavity, was fabricated by a simple sublimation–oxidation–deposition strategy. By using a spatially resolved spectroscopic technique, the effects of the cross sectional geometry on optical modulations was carefully investigated. The experimental results fitted well with the plane wave interference model and finite element method simulations. Our results demonstrate that the In2O3 microwire optical resonator offers another practical example for the study of fundamental physics in the field of cavity optics, and may be helpful for the development of miniature cavity-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

We demonstrate an easy, novel synthesis of nanosheet-based flower-like ZnO microspheres without any catalyst and template. The layered hydroxide zinc acetate Zn5(OH)8(CH3COO)2·2H2O (LHZA) nanostructures, one of important and efficient precursors to synthesize three dimensional (3D) ZnO hierarchical microstructures, are first fabricated in aqueous solution at room temperature. The detailed crystal structure and formation mechanism of the LHZA are also investigated. It is noteworthy that the initial ZnO seed layer is crucial to the growth of the final nano/microarchitectures. We found that the as-synthesized hierarchical ZnO microspheres obtained from the decomposition of LHZA showed excellent photocatalytic activity for the photodegradation of rhodamine 6G. This facile, efficient, and economical work provides a new route to simply and mildly synthesize ZnO 3D hierarchical microspheres, which may be adopted to prepare other metal oxide microstructures. [ABSTRACT FROM AUTHOR]

Hollow Gd2O3:Ln (Ln = Eu3, Sm3) microspheres were successfully fabricated by using carbon spheres as a template and urea as a precipitating agent, which involved the deposition of an inorganic coating on the surface of carbon spheres and subsequent calcination in the air. Various approaches including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence spectroscopy as well as kinetic decays were used to characterize the samples. The results indicate that the as-prepared products can be indexed to pure cubic Gd2O3phase. The samples are composed of uniform hollow Gd2O3:Ln spheres with a mean particle size of about 300 nm. The possible mechanism of evolution from glucose to carbon microspheres and the chemical reaction of each step to form the final hollow spheres are proposed. In particular, the urea-assisted precipitation process was carried out in aqueous solution without any organic solvent, and the hollow spheres formation process was achieved by simple calcination without using any etching agents. The hollow Gd2O3:Ln phosphors exhibit light emission under ultraviolet excitation, which may find promising applications in the fields of field emission displays (FED) and MRI contrast agents. [ABSTRACT FROM AUTHOR]

Hollow Gd2O3:Ln (Ln = Eu3+, Sm3+) microspheres were successfully fabricated by using carbon spheres as a template and urea as a precipitating agent, which involved the deposition of an inorganic coating on the surface of carbon spheres and subsequent calcination in the air. Various approaches including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence spectroscopy as well as kinetic decays were used to characterize the samples. The results indicate that the as-prepared products can be indexed to pure cubic Gd2O3phase. The samples are composed of uniform hollow Gd2O3:Ln spheres with a mean particle size of about 300 nm. The possible mechanism of evolution from glucose to carbon microspheres and the chemical reaction of each step to form the final hollow spheres are proposed. In particular, the urea-assisted precipitation process was carried out in aqueous solution without any organic solvent, and the hollow spheres formation process was achieved by simple calcination without using any etching agents. The hollow Gd2O3:Ln phosphors exhibit light emission under ultraviolet excitation, which may find promising applications in the fields of field emission displays (FED) and MRI contrast agents. [ABSTRACT FROM AUTHOR]

Due to the unique and excellent optical performance and promising prospect for various photonics applications, cavity-enhanced superfluorescence (CESF) in perovskite quantum dot assembled superstructures has garnered wide attention. However, the stringent requirements and high threshold for achieving CESF limit its further development and application. The high threshold of CESF in quantum dot superstructures is mainly attributed to the low radiation recombination rate of the quantum dot and the unsatisfactory light field limiting the ability of the assembled superstructures originating from low controllability of self-assembly. Herein, we propose a strategy to reduce the threshold of CESF in quantum dot superstructure microcavities from two aspects: facet engineering optimization of quantum dot blocks and controllability improvement of the assembly method. We introduce dodecahedral quantum dots with lower nonradiative recombination, substituting frequently used cubic quantum dots as assembly blocks. Besides, we adopt the micro-emulsion droplet assembly method to obtain spherical perovskite quantum dot superparticles with high packing factors and orderly internal arrangements, which are more controllable and efficient than the conventional solvent-drying methods. Based on the dodecahedral quantum dot superparticles, we realized low-threshold CESF (Pth = 15.6 μJ cm -2 ). Our work provides a practical and scalable avenue for realizing low threshold CESF in quantum dot assembled superstructure systems., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A novel family of heteronuclear Mn(IV)Ca-oxido complexes containing Mn(IV)Ca-oxido cuboidal moieties and reactive water molecules on Ca(2+) have been synthesized and characterized to mimic the oxygen-evolving complex (OEC) of photosystem II (PSII) in nature.

A novel heterometallic MnSr complex containing the Mn3SrO4 cuboidal moiety and all types of μ-O(2-) moieties observed in the oxygen-evolving complex (OEC) in Sr(2+)-containing photosystem II (PSII) has been synthesized and characterized, which provides a new synthetic model of the OEC.