Organic–inorganic hybrid perovskites are promising candidates for the next-generation solar cells. Many efforts have been made to study their structures in the search for a better mechanistic understanding to guide the materials optimization. Here, we investigate the structure instability of the single-crystalline CH3NH3PbI3 (MAPbI3) film by using transmission electron microscopy. We find that MAPbI3 is very sensitive to the electron beam illumination and rapidly decomposes into the hexagonal PbI2. We propose a decomposition pathway, initiated with the loss of iodine ions, resulting in eventual collapse of perovskite structure and its decomposition into PbI2. These findings impose important question on the interpretation of experimental data based on electron diffraction and highlight the need to circumvent material decomposition in future electron microscopy studies. The structural evolution during decomposition process also sheds light on the structure instability of organic–inorganic hybrid perovskites in solar cell applications.

Ion hydration and transport at interfaces are relevant to a wide range of applied fields and natural processes. Interfacial effects are particularly profound in confined geometries such as nanometre-sized channels, where the mechanisms of ion transport in bulk solutions may not apply. To correlate atomic structure with the transport properties of hydrated ions, both the interfacial inhomogeneity and the complex competing interactions among ions, water and surfaces require detailed molecular-level characterization. Here we constructed individual sodium ion (Na) hydrates on a NaCl(001) surface by progressively attaching single water molecules (one to five) to the Na ion using a combined scanning tunnelling microscopy and noncontact atomic force microscopy system. We found that the Na ion hydrated with three water molecules diffuses orders of magnitude more quickly than other ion hydrates. Ab initio calculations revealed that such high ion mobility arises from the existence of a metastable state, in which the three water molecules around the Na ion can rotate collectively with a rather small energy barrier. This scenario would apply even at room temperature according to our classical molecular dynamics simulations. Our work suggests that anomalously high diffusion rates for specific hydration numbers of ions are generally determined by the degree of symmetry match between the hydrates and the surface lattice.

Water/solid interfaces are vital to our daily lives and are also a central theme across an incredibly wide range of scientific disciplines. Resolving the internal structure, that is, the O-H directionality, of water molecules adsorbed on solid surfaces has been one of the key issues of water science yet it remains challenging. Using a low-temperature scanning tunnelling microscope, we report submolecular-resolution imaging of individual water monomers and tetramers on NaCl(001) films supported by a Au(111) substrate at 5 K. The frontier molecular orbitals of adsorbed water were directly visualized, which allowed discrimination of the orientation of the monomers and the hydrogen-bond directionality of the tetramers in real space. Comparison with ab initio density functional theory calculations reveals that the ability to access the orbital structures of water stems from the electronic decoupling effect provided by the NaCl films and the precisely tunable tip-water coupling.

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A cDNA clone encoding a 64-amino acid type 3 metallothionein protein, designated GhMT3a, was isolated from cotton (Gossypium hirsutum) by cDNA library screening. Northern blot analysis indicated that mRNA accumulation of GhMT3a was up-regulated not only by high salinity, drought, and low temperature stresses, but also by heavy metal ions, abscisic acid (ABA), ethylene, and reactive oxygen species (ROS) in cotton seedlings. Transgenic tobacco (Nicotiana tabacum) plants overexpressing GhMT3a showed increased tolerance against abiotic stresses compared with wild-type plants. Interestingly, the induced expression of GhMT3a by salt, drought, and low-temperature stresses could be inhibited in the presence of antioxidants. H2O2 levels in transgenic tobacco plants were only half of that in wild-type (WT) plants under such stress conditions. According to in vitro assay, recombinant GhMT3a protein showed an ability to bind metal ions and scavenge ROS. Transgenic yeast overexpressing GhMT3a also showed higher tolerance against ROS stresses. Taken together, these results indicated that GhMT3a could function as an effective ROS scavenger and its expression could be regulated by abiotic stresses through ROS signalling.