Inorganic–organic hybrid materials represent a large share of newly reported structures, owing to their simple synthetic routes and customizable properties1. This proliferation has led to a characterization bottleneck: many hybrid materials are obligate microcrystals with low symmetry and severe radiation sensitivity, interfering with the standard techniques of single-crystal X-ray diffraction2,3 and electron microdiffraction4–11. Here we demonstrate small-molecule serial femtosecond X-ray crystallography (smSFX) for the determination of material crystal structures from microcrystals. We subjected microcrystalline suspensions to X-ray free-electron laser radiation12,13 and obtained thousands of randomly oriented diffraction patterns. We determined unit cells by aggregating spot-finding results into high-resolution powder diffractograms. After indexing the sparse serial patterns by a graph theory approach14, the resulting datasets can be solved and refined using standard tools for single-crystal diffraction data15–17. We describe the ab initio structure solutions of mithrene (AgSePh)18–20, thiorene (AgSPh) and tethrene (AgTePh), of which the latter two were previously unknown structures. In thiorene, we identify a geometric change in the silver–silver bonding network that is linked to its divergent optoelectronic properties20. We demonstrate that smSFX can be applied as a general technique for structure determination of beam-sensitive microcrystalline materials at near-ambient temperature and pressure.

In this contribution we use nonconventional methods that help to increase the success rate of a protein crystal growth, and consequently of structural projects using Xray diffraction techniques. In order to achieve this purpose, this contribution presents new approaches involving more sophisticated techniques of protein crystallization, not just for growing protein crystals of different sizes by using electric fields, but also for controlling crystal size and orientation. This latter was possible through the use of magnetic fields that allow to obtain protein crystals suitable for both high-resolution X-ray and neutron diffraction crystallography where big crystals are required. This contribution discusses some pros, cons and realities of the role of electromagnetic fields in protein crystallization research, and their effect on protein crystal contacts. Additionally, we discuss the importance of room and low temperatures during data collection. Finally, we also discuss the effect of applying a rather strong magnetic field of 16.5 T, for shorts and long periods of time, on protein crystal growth, and on the 3D structure of two model proteins.

Copper‐based layered perovskites have shown abundant phase transitions and thermochromic behaviors. However, there are very few cases of perovskites with irreversible transitions. Here, the thermochromic behavior of two perovskites (CEA)2CuCl4 and (BEA)2CuCl4 is discussed, where CEA = 2‐chloroethylammonium and BEA = 2‐bromoethylammonium, the latter of which is reported for the first time. These materials exhibit a reversible and irreversible thermochromic behavior determined by the nature of the organic cation. Using nuclear magnetic resonance, X‐ray diffraction, and optical absorption, it was possible to investigate the mechanism for this transition: a topochemical exchange reaction between the organic and inorganic halides in (BEA)2CuCl4 to yield the mixed‐halide perovskite (BEA)1.1(CEA)0.9CuCl3.1Br0.9. These materials and the fundamental principles shown herein have potential use as low‐cost irreversible thermochromic sensors and their design.

Herein we show that mixed-cation perovskite films made by spin-coating do not necessarily have the same stoichiometry as the precursor solution from which they are made and propose a simple method to quantify the true composition of such films.

Broadband and white-light emitting materials are sought after for applications such as phosphors and LEDs. Some twodimensional (2D) halide perovskites are promising candidates in this realm. Nevertheless, optimizing their photoluminescence quantum efficiency (PLQY) is highly challenging. Herein, we show a new strategy for optimizing the efficiency of the broadband emission of 2D halide perovskites. Specifically, we show that by a combination of halide bonds and halide mixing, the PLQYs of a novel family of materials with the formula (Br-PEA) 2 PbBr x Cl 4−x (Br-PEA = 4-bromo phenethylammonium) can be improved by one order of magnitude, from 3 to 25%; this approach could be useful to many other 2D perovskites.