The manipulation of crystal orientation from the thermodynamic equilibrium states is desired in layered hybrid perovskite films to direct charge transport and enhance the perovskite devices performance. Here we report a templated growth mechanism of layered perovskites from 3D-like perovskites which can be a general design rule to align layered perovskites along the out-of-plane direction in films made by both spin-coating and scalable blading process. The method involves suppressing the nucleation of both layered and 3D perovskites inside the perovskite solution using additional ammonium halide salts, which forces the film formation starts from solution surface. The fast drying of solvent at liquid surface leaves 3D-like perovskites which surprisingly templates the growth of layered perovskites, enabled by the periodic corner-sharing octahedra networks on the surface of 3D-like perovskites. This discovery provides deep insights into the nucleation behavior of octahedra-array-based perovskite materials, representing a general strategy to manipulate the orientation of layered perovskites.
Graphene nanomaterials (GMs), such as graphene oxide (GO) and reduced graphene oxide (rGO), have been widely applied in various fields. Due to the rapid increase in production and application, the inevitable release of GMs into water and soil environments poses potential health and ecosystem risks. Upon exposure, the behavior, transport, and fate of GMs may be altered after interacting with the relevant environmental conditions. GMs can affect the microbial communities as well. Thus, it is imperative to understand the interaction between the GMs and the environmental systems for predicting their risks. For this purpose, this review highlights the influence of the most relevant environmental factors on the stability, aggregation, and transformation of GMs in aquatic environments. Moreover, the transport of GMs and microbial communities changes have also been presented based on the recent findings. To the best of our knowledge, this review covered most of the recent related studies and will allow for accurate predictions of the fate and risks associated with GMs. In consideration of the diversity of GMs and the complexity of environmental factors, further studies should be focused on their inherent properties and amicable development.
Silver nanomaterials with distinct fluorescent properties are synthesized with a series of G-rich/C-rich DNA templates, and the influence of DNA conformational structures on the size and the fluorescence of silver nanomaterials was investigated through varying the sequence composition and the ratio of complementary sequences, using CD, UV–vis, fluorescence spectroscopy, and TEM. It is intriguing to find out that G-rich templates at acidic conditions are capable of generating red emitters that are susceptible to the G-quadruplex structures associated with the number of 5′-terminal guanines. C-rich sequences can produce red silver clusters at either acidic or neutral conditions, and the emission is dramatically regulated by the number of 3′-end cytosines. It is the first time to report that double-stranded DNA templates can generate distinct fluorescent nanosilver modulated by the predominance among the structural competition of the Watson–Crick duplex, G-quadruplex, and i-motif. These results provide a promising pathway to prepare silver nanomaterials with desirable physicochemical properties through designing suitable DNA templates.
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