The spontaneous α-to-δ phase transition of the formamidinium-based (FA) lead halide perovskite hinders its large scale application in solar cells. Though this phase transition can be inhibited by alloying with methylammonium-based (MA) perovskite, the underlying mechanism is largely unexplored. In this Communication, we grow high-quality mixed cations and halides perovskite single crystals (FAPbI)(MAPbBr) to understand the principles for maintaining pure perovskite phase, which is essential to device optimization. We demonstrate that the best composition for a perfect α-phase perovskite without segregation is x = 0.1-0.15, and such a mixed perovskite exhibits carrier lifetime as long as 11.0 μs, which is over 20 times of that of FAPbI single crystal. Powder XRD, single crystal XRD and FT-IR results reveal that the incorporation of MA is critical for tuning the effective Goldschmidt tolerance factor toward the ideal value of 1 and lowering the Gibbs free energy via unit cell contraction and cation disorder. Moreover, we find that Br incorporation can effectively control the perovskite crystallization kinetics and reduce defect density to acquire high-quality single crystals with significant inhibition of δ-phase. These findings benefit the understanding of α-phase stabilization behavior, and have led to fabrication of perovskite solar cells with highest efficiency of 19.9% via solvent management.

1603568(1 of 8) photoluminescence (PL) yield for potential optoelectronic application such as in LED and laser devices. [10][11][12][13][14][15][16][17][18] Luminescent MAPbBr 3 films have been deposited onto mesoporous Al 2 O 3 substrate. [19,20] Beside regular bulk lead halide perovskite, 2D or nanostructured lead halide perovskites had been previously synthesized for use as LEDs or other optoelectronic materials. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] These progresses have demonstrated the great success of classic solution chemistry method in the preparation of high quality lead halide nanocrystals with excellent photoluminescent properties for optoelectronic applications.It should be pointed out that although high quality nanocrystals can be successfully fabricated into devices via follow-up processes, a high quality film is more easy-to-process than nanocrystals suspensions for optoelectronic applications. For example, smooth lead halide perovskite films have been directly fabricated via simple one-step or two-step method in solar cell applications. [37] However, we found the high quality smooth planar MAPbBr 3 films for solar cells usually do not exhibit high photoluminescent properties as the nanocrystals suspension or the film deposited in the mesoporous Al 2 O 3 matrix. This is because the MAPbBr 3 films usually consist of large perovskite nanocrystals with size up to hundreds nanometers to micrometers, while the mesoporous support can be used to prevent crystal growth and control the particle size. As recently reported, lead halide perovskite nanoplate with quantum confine without the mesoporous support could grow in large crystals and thus lose the quantum confine effect. [38] It would be urgent to develop a facile method to fabricate highly luminescent perovskite-based film with good controllability and high stability.Metal-organic frameworks (MOFs) are periodic networks formed by coordination of metal ions with organic molecules. This configuration bears the similar structure as the organicinorganic perovskite from the viewpoints that both consist of the metal ions and organic molecules in the framework or lattice. Inspired by the ease preparation and various advantages of the MOFs configuration, [39][40][41] here, we report a strategy for fabricating highly luminescent and stable lead bromide The perovskite quantum dots are usually synthesized by solution chemistry and then fabricated into film for device application with some extra process. Here it is reported for the first time to in situ formation of a crosslinked 2D/3D NH 3 C 4 H 9 COO(CH 3 NH 3 ) n Pb n Br 3n perovskite planar films with controllable quantum confine via bifunctional amino acid crosslinkage, which is comparable to the solution chemistry synthesized CH 3 NH 3 PbBr 3 quantum dots. These atomic layer controllable perovskite films are facilely fabricated and tuned by addition of bi-functional 5-aminovaleric acid (Ava) of NH 2 C 4 H 9 COOH into regular (CH 3 NH 3 )PbBr 3 (MAPbBr 3 ) perovskite precursor solu...

No abstract

No abstract

BackgroundLong non-coding RNAs (lncRNAs) have been found to play a vital role in several gene regulatory networks involved in the various biological processes in plants related to stress response. However, systematic analyses of lncRNAs expressed in rice Cadmium (Cd) stress are seldom studied. Thus, we presented the characterization and expression of lncRNAs in rice root development at an early stage in response to Cd stress.ResultsThe lncRNA deep sequencing revealed differentially expressed lncRNAs among Cd stress and normal condition. In the Cd stress group, 69 lncRNAs were up-regulated and 75 lncRNAs were down-regulated. Furthermore, 386 matched lncRNA-mRNA pairs were detected for 120 differentially expressed lncRNAs and 362 differentially expressed genes in cis, and target gene-related pathway analyses exhibited significant variations in cysteine and methionine metabolism pathway-related genes. For the genes in trans, overall, 28,276 interaction relationships for 144 lncRNAs and differentially expressed protein-coding genes were detected. The pathway analyses found that secondary metabolites, such as phenylpropanoids and phenylalanine, and photosynthesis pathway-related genes were significantly altered by Cd stress. All of these results indicate that lncRNAs may regulate genes of cysteine-rich peptide metabolism in cis, as well as secondary metabolites and photosynthesis in trans, to activate various physiological and biochemical reactions to respond to excessive Cd.ConclusionThe present study could provide a valuable resource for lncRNA studies in response to Cd treatment in rice. It also expands our knowledge about lncRNA biological function and contributes to the annotation of the rice genome.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4807-6) contains supplementary material, which is available to authorized users.

Optimizing product selectivity and conversion efficiency are primary goals in catalysis. However, efficiency and selectivity are often mutually antagonistic, so that high selectivity is accompanied by low efficiency and vice versa. Also, just increasing the temperature is very unlikely to change the reaction pathway. Here, by constructing hierarchical plasmonic nanoreactors, we show that nanoconfined thermal fields and energetic electrons, a combination of attributes that coexist almost uniquely in plasmonic nanostructures, can overcome the antagonism by regulating selectivity and promoting conversion rate concurrently. For propylene partial oxidation, they drive chemical reactions by not only regulating parallel reaction pathways to selectively produce acrolein but also reducing consecutive process to inhibit the overoxidation to CO2, resulting in valuable products different from thermal catalysis. This suggests a strategy to rationally use plasmonic nanostructures to optimize chemical processes, thereby achieving high yield with high selectivity at lower temperature under visible light illumination.

Summary Red rice contains high levels of proanthocyanidins and anthocyanins, which have been recognized as health‐promoting nutrients. The red coloration of rice grains is controlled by two complementary genes, Rc and Rd. The RcRd genotype produces red pericarp in wild species Oryza rufipogon, whereas most cultivated rice varieties produce white grains resulted from a 14‐bp frame‐shift deletion in the seventh exon of the Rc gene. In the present study, we developed a CRISPR/Cas9‐mediated method to functionally restore the recessive rc allele through reverting the 14‐bp frame‐shift deletion to in‐frame mutations in which the deletions were in multiples of three bases, and successfully converted three elite white pericarp rice varieties into red ones. Rice seeds from T1 in‐frame Rc lines were measured for proanthocyanidins and anthocyanidins, and high accumulation levels of proanthocyanidins and anthocyanidins were observed in red grains from the mutants. Moreover, there was no significant difference between wild‐type and in‐frame Rc mutants in major agronomic traits, indicating that restoration of Rc function had no negative effect on important agronomic traits in rice. Given that most white pericarp rice varieties are resulted from the 14‐bp deletion in Rc, it is conceivable that our method could be applied to most white pericarp rice varieties and would greatly accelerate the breeding of new red rice varieties with elite agronomic traits. In addition, our study demonstrates an effective approach to restore recessive frame‐shift alleles for crop improvement.

Witnessed by the rapid increase of power conversion efficiency to 25.5%, organic–inorganic hybrid perovskite solar cells (PSCs) are becoming promising candidates of next‐generation photovoltaics. However, PSCs can be unstable under the influence of light and bias. Especially, grain boundaries (GBs) are vulnerable to attack by light and bias in perovskite films, leading to degradation of photovoltaic properties of PSCs. Herein, photocurrent atomic force microscopy and Kelvin probe force microscopy are employed to systematically investigate the bias‐dependent charge transport behaviors and stability of (FAPbI3)0.85(MAPbBr3)0.15 perovskite under working condition. Bias‐dependent morphology and photocurrent images show irreversible decomposition of the perovskite at a bias of 0.1 V or below, which is accelerated by light illumination, leading to formation of an interfacial layer that restricts carrier transport. Meanwhile, GBs appear to enhance carrier transport at larger bias, but serve as breakthrough sites for perovskite decomposition at smaller bias. Introducing excess methylammonium iodide promotes decomposition, while potassium iodide passivation greatly relieves the decomposition. These results support the ion migration mechanism of decomposition through interfaces and GBs. This work provides a deeper understanding of bias‐induced degradation of PSCs as well as bias‐dependent double‐edged roles of GBs, and forms valuable guidance for appropriate operation of PSCs.