Organic-inorganic perovskite materials are revolutionizing photovoltaics with high power conversion efficiencies, but experience significant environmental degradation and instability. In this work, the phase stability and decomposition mechanisms of lead-free all inorganic Cs2SnI6 perovskite upon water and moisture exposure were systematically investigated via in situ synchrotron X-ray diffraction, environmental SEM, and micro-Raman spectroscopy. A critical relative humidity (80%) is identified below which Cs2SnI6 perovskite is stable without decomposition. Under higher humidity or aqueous environment, Cs2SnI6 perovskite decomposes into SnI4 and CsI through etch pits formation and stepwave propagation, leading to rapid crystal dissolution. A partial reversibility of the Cs2SnI6 perovskite upon dissolution and re-precipitation with subsequent dehydration was identified, suggesting a self-healing capability of Cs2SnI6 and thus enhanced air stability. Mechanistic understanding of the Cs2SnI6 degradation behavior can be a vital step towards developing new perovskites with enhanced environmental stability and materials performance.
A metal‐ and reagent‐free, electrochemical cross‐dehydrogenative coupling reaction of N‐aryl‐tetrahydroisoquinolines with phosphites and indole is developed. This method provides an environmentally benign and simple approach for the construction of C–P and C–C bonds in moderate to high yields with wide tolerance of functional groups.
Guanine-rich sequences in the genomes of herpesviruses can fold into G-quadruplexes. Compared with the widely-studied G3-quadruplexes, the dynamic G2-quadruplexes are more sensitive to the cell microenvironment, but they attract less attention. Pseudorabies virus (PRV) is the model species for the study of the latency and reactivation of herpesvirus in the nervous system. A total of 1722 G2-PQSs and 205 G3-PQSs without overlap were identified in the PRV genome. Twelve G2-PQSs from the CDS region exhibited high conservation in the genomes of the Varicellovirus genus. Eleven G2-PQSs were 100% conserved in the repeated region of the annotated PRV genomes. There were 212 non-redundant G2-PQSs in the 3′ UTR and 19 non-redundant G2-PQSs in the 5′ UTR, which would mediate gene expression in the post-transcription and translation processes. The majority of examined G2-PQSs formed parallel structures and exhibited different sensitivities to cations and small molecules in vitro. Two G2-PQSs, respectively, from 3′ UTR of UL5 (encoding helicase motif) and UL9 (encoding sequence-specific ori-binding protein) exhibited diverse regulatory activities with/without specific ligands in vivo. The G-quadruplex ligand, NMM, exhibited a potential for reducing the virulence of the PRV Ea strain. The systematic analysis of the distribution of G2-PQSs in the PRV genomes could guide further studies of the G-quadruplexes’ functions in the life cycle of herpesviruses.
Hybrid halide perovskites
display a great tunability of optoelectronic properties and environmental
stability by controlling the halogen anions (e.g., I, Cl,
and Br). However, their water interaction and degradation mechanisms
are not fully elucidated. In this work, the interaction of Cs2SnCl6 and Cl-enriched solid solution Cs2SnI0.9Cl5.1 with water was systematically studied
by in situ synchrotron X-ray diffraction and micro-Raman spectra and
compared with the isostructural Cs2SnI6. Unlike Cs2SnI6, which experiences a direct
dissolution in water, Cs2SnCl6 displays an enhanced
stability and the dissolution of the Cs2SnCl6 accompanies with the formation of an amorphous alteration phase. Under
controlled dehydration conditions, two-dimensional Cs2SnCl6 flakes can be precipitated out from water solution. Furthermore,
the mixed halide perovskite (Cs2SnI0.9Cl5.1) experiences fast iodide dissolution in water solution
and transforms to a more chloride-enriched perovskite which shows
a behavior similar to Cs2SnCl6. The mechanistic
understanding of the dissolution–precipitation process of Cs2SnI
x
Cl6–x
perovskites is useful for developing new perovskites with
varied halogen and controlled environmental stability.
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