Metal Coordination Sphere Deformation Induced Highly Stokes‐Shifted,Ultra Broadband Emission in 2D Hybrid Lead‐Bromide Perovskites and Investigation of Its Origin

Published studies of layered (2D) (100)‐oriented hybrid lead‐bromide perovskites evidence a correlation between increased inter‐octahedral (Pb‐Br‐Pb) distortions and the appearance of broadband white light emission. However, the impact of distortions within their constituent [PbBr₆]^4? octahedra has yet to be assessed. Herein, we report two new (100)‐oriented 2D Pb‐Br perovskites, whose structures display unusually high intra‐octahedral distortions, whilst retaining minimal inter‐octahedral distortions. Using a combination of temperature‐dependent, power‐dependent and time‐resolved photoluminescence spectroscopic measurements, we show that increased intra‐octahedral distortion induces exciton localization processes and leads to formation of multiple photoinduced emissive colour centres. Ultimately, this leads to highly Stokes‐shifted, ultrabroad white light emission at room temperature.     

Local properties of geodesics onp-convex sets

Summary We prove some local properties of geodesics on p-convex sets. First of all, we give an intrinsic characterization of geodesic in terms of local minimality for the energy functional. Then, we prove local uniqueness and continuous dependence from extrema for geodesics with assigned endpoints. Further, we show a consequence of these results.     

Palladium-catalysed Heck reaction on 1,2-dien-1-ols: a stereoselective synthesis of α-arylated α,β-unsaturated aldehydes

A new methodology for preparing α-arylated α,β-unsaturated aldehydes is reported. The starting materials are all commercially available alkyn-1-ols (1a-c) that have been easily isomerised to the corresponding allenes (2a-c). The key step is the Heck coupling of the 1,2-dien-1-ols with a series of iodo- and bromoarene. The products have been synthesised in good yields, and the reactions were carried out under very mild conditions.     

Effect of biotic and abiotic stresses on volatile emission of Achillea collina Becker ex Rchb

This study describes the application of headspace solid-phase microextraction (HS-SPME)–gas chromatography/mass spectrometry (GC/MS) to characterise the volatile fingerprint changes of Achillea collina, induced by aphids' infestation, mechanical damage and jasmonic acid (JA) treatment. The volatile organic compound profiles of A. collina, Prunus persica and Pisum sativum infested by Myzus persicae were also compared. Several changes were observed between control, infested, mechanically damaged and JA-treated plants, and new inducible volatile organic compounds (IVOCs) were emitted in response to biotic or abiotic stresses. Some of these were in common for all stresses and other compounds were in common only for two types of stress. Conversely some IVOCs were emitted only in response to the specific stimuli. The results suggested that there were species-specific and common IVOCs emitted by A. collina, P. persica and P. sativum in response to M. persicae infestation. In conclusion, HS-SPME–GC/MS seems to be a reliable analytical approach to study in vivo plant reaction to external stimuli.     

Metal Coordination Sphere Deformation Induced Highly Stokes-Shifted,Ultra Broadband Emission in 2D Hybrid Lead-Bromide Perovskites and Investigation of Its Origin

Published studies of layered (2D) (100)-oriented hybrid lead-bromide perovskites evidence a correlation between increased inter-octahedral (Pb-Br-Pb) distortions and the appearance of broadband white light emission. However, the impact of distortions within their constituent [PbBr₆]⁴⁻ octahedra has yet to be assessed. Herein, we report two new (100)-oriented 2D Pb-Br perovskites, whose structures display unusually high intra-octahedral distortions, whilst retaining minimal inter-octahedral distortions. Using a combination of temperature-dependent, power-dependent and time-resolved photoluminescence spectroscopic measurements, we show that increased intra-octahedral distortion induces exciton localization processes and leads to formation of multiple photoinduced emissive colour centres. Ultimately, this leads to highly Stokes-shifted, ultrabroad white light emission at room temperature.     

Diffusion of iron in lithium niobate: a secondary ion mass spectrometry study

Iron-doped X-cut lithium niobate crystals were prepared by means of thermal diffusion from thin film varying in a systematic way the process parameters such as temperature and diffusion duration. Secondary Ion Mass Spectrometry was exploited to characterize the iron in-depth profiles. The evolution of the composition of the Fe thin film in the range between 600°C and 800°C was studied, and the diffusion coefficient at different temperatures in the range between 900°C and 1050°C and the activation energy of the diffusion process were estimated.     

Almost Exponential Maps and Integrability Results for a Class of Horizontally Regular Vector Fields

We consider a family ${\mathcal{H}}:= \{X_1, \dots, X_m\}$ of C ¹ vector fields in ? ⁿ and we discuss the associated ${\mathcal{H}}$ -orbits. Namely, we assume that our vector fields belong to a horizontal regularity class and we require that a suitable s-involutivity assumption holds. Then we show that any ${\mathcal{H}}$ -orbit ${\mathcal{O}}$ is a C ¹ immersed submanifold and it is an integral submanifold of the distribution generated by the family of all commutators up to length s. Our main tool is a class of almost exponential maps of which we discuss carefully some precise first order expansions.     

Local {W^{2,m(\cdot)}_{loc}}regularity for p(.)-Laplace equations

We study ${W^{2,m(\cdot)}_{loc}}$ regularity for local weak solutions of p(·)-Laplace equations where ${p\in C^1(\Omega) \cap C(\overline{\Omega})}$ and ${\min_{x\in \overline{\Omega}} p(x) > 1}$ .     

Synthesis of tetrasubstituted 4,4'-biimidazoles

Highly substituted 4,4'-biimidazoles were synthesized, in good to excellent yields, through a multicomponent imidazole ring synthesis by using imidazol-4-yl-ethane-1,2-diones as starting materials. The obtained compounds were preliminarily tested as chromogenic and fluorescent sensors for heavy metals.