Hybrid Mechanism of Nucleation and Cooperative Propagation in a Single-Crystal-to-Single-Crystal Transition of a Molecular Crystal

Martensitic transition is a type of solid-phase transition that involves a collective, rapid propagation of crystal structure change. In molecular crystals, such a transition is rarely observed, as most systems exhibit a nucleation and growth mechanism. Thus, the process and mechanism of martensitic transition are underexplored. Here we use in situ microscopy of organic single crystals complemented with interaction energy calculations to provide new insights on martensitic transition. We separate the transition process into three distinct steps where each step corresponds to propagation of structural change in a specific direction. We analyze an initiation stage and two propagation stages from hysteresis and propagation speed during cyclic transitions. We discover the dichotomous role of defects in facilitating the initiation step and hindering the propagation steps of transition. We conclude that the organic martensitic transition shows mixed mechanisms of nucleation and cooperativity. This study presents new experimental evidence of a rare phenomenon that will contribute to expanding the understanding of martensitic transition in molecular crystals

Hybrid Mechanism of Nucleation and Cooperative Propagation in a Single-Crystal-to-Single-Crystal Transition of a Molecular Crystal

Martensitic transition is a type of solid-phase transition that involves a collective, rapid propagation of crystal structure change. In molecular crystals, such a transition is rarely observed, as most systems exhibit a nucleation and growth mechanism. Thus, the process and mechanism of martensitic transition are underexplored. Here we use in situ microscopy of organic single crystals complemented with interaction energy calculations to provide new insights on martensitic transition. We separate the transition process into three distinct steps where each step corresponds to propagation of structural change in a specific direction. We analyze an initiation stage and two propagation stages from hysteresis and propagation speed during cyclic transitions. We discover the dichotomous role of defects in facilitating the initiation step and hindering the propagation steps of transition. We conclude that the organic martensitic transition shows mixed mechanisms of nucleation and cooperativity. This study presents new experimental evidence of a rare phenomenon that will contribute to expanding the understanding of martensitic transition in molecular crystals

Hybrid Mechanism of Nucleation and Cooperative Propagation in a Single-Crystal-to-Single-Crystal Transition of a Molecular Crystal

Martensitic transition is a type of solid-phase transition that involves a collective, rapid propagation of crystal structure change. In molecular crystals, such a transition is rarely observed, as most systems exhibit a nucleation and growth mechanism. Thus, the process and mechanism of martensitic transition are underexplored. Here we use in situ microscopy of organic single crystals complemented with interaction energy calculations to provide new insights on martensitic transition. We separate the transition process into three distinct steps where each step corresponds to propagation of structural change in a specific direction. We analyze an initiation stage and two propagation stages from hysteresis and propagation speed during cyclic transitions. We discover the dichotomous role of defects in facilitating the initiation step and hindering the propagation steps of transition. We conclude that the organic martensitic transition shows mixed mechanisms of nucleation and cooperativity. This study presents new experimental evidence of a rare phenomenon that will contribute to expanding the understanding of martensitic transition in molecular crystals

Hybrid Mechanism of Nucleation and Cooperative Propagation in a Single-Crystal-to-Single-Crystal Transition of a Molecular Crystal

Martensitic transition is a type of solid-phase transition that involves a collective, rapid propagation of crystal structure change. In molecular crystals, such a transition is rarely observed, as most systems exhibit a nucleation and growth mechanism. Thus, the process and mechanism of martensitic transition are underexplored. Here we use in situ microscopy of organic single crystals complemented with interaction energy calculations to provide new insights on martensitic transition. We separate the transition process into three distinct steps where each step corresponds to propagation of structural change in a specific direction. We analyze an initiation stage and two propagation stages from hysteresis and propagation speed during cyclic transitions. We discover the dichotomous role of defects in facilitating the initiation step and hindering the propagation steps of transition. We conclude that the organic martensitic transition shows mixed mechanisms of nucleation and cooperativity. This study presents new experimental evidence of a rare phenomenon that will contribute to expanding the understanding of martensitic transition in molecular crystals

Chromium(III) Terephthalate Metal Organic Framework (MIL-101): HF-Free Synthesis, Structure, Polyoxometalate Composites, and Catalytic Properties

Hybrid materials of the metal–organic framework (MOF), chromium­(III) terephthalate (MIL-101), and phosphotungstic acid (PTA) were synthesized in aqueous media in the absence of hydrofluoric acid. XRD analysis of the MIL101/PTA composites indicates the presence of ordered PTA assemblies residing in both the large cages and small pores of MIL-101, which suggests the formation of previously undocumented structures. The MIL101/PTA structure enables a PTA payload 1.5–2 times higher than previously achieved. The catalytic performance of the MIL101/PTA composites was assessed in the Baeyer condensation of benzaldehyde and 2-naphthol, in the three-component condensation of benzaldehyde, 2-naphthol, and acetamide, and in the epoxidation of caryophyllene by hydrogen peroxide. The catalytic efficiency was demonstrated by the high (over 80–90%) conversion of the reactants under microwave-assisted heating. In four consecutive reaction cycles, the catalyst recovery was in excess of 75%, whereas the product yields were maintained above 92%. The simplicity of preparation, exceptional stability, and reactivity of the novel composites indicate potential in utilization of these catalytic matrices in a multitude of catalytic reactions and engineering processes

Conjugation-Break Spacers in Semiconducting Polymers: Impact on Polymer Processability and Charge Transport Properties

Conjugation-break spacers (CBSs) are intentionally introduced into the diketopyrrolopyrrole (DPP)-based polymer backbones. We reveal that the solution processability progressively increases with the percentage of CBSs, while charge mobility inversely varies to the CBS ratio. For instance, the polymer DPP-30 with solubility of ∼10 mg/mL in dichlorobenzene provides an average mobility over 1.4 cm² V^–1 s^–1, while DPP-0 exhibits an average mobility of 4.3 cm² V^–1 s^–1 with solubility of ∼3 mg/mL. This correlation provides a general guidance to design polymers with desired electronic performance and solution processability for large-scale roll-to-roll processing. Most encouraging, DPP-70 can be melt processed in air and provide hole mobilities up to 0.30 cm² V^–1s^–1, substantially higher value than their solution-processed counterparts about 0.1 cm² V^–1 s^–1. The mobility boost in melt-processed devices, together with completely eliminating the need to use toxic solvent in the processing, encourages to design melt-processable polymers for electronic devices

<i>De Novo</i> Transcriptome and Small RNA Analyses of Two Amorphophallus Species

<div><p>Konjac is one of the most important glucomannan crops worldwide. The breeding and genomic researches are largely limited by the genetic basis of <i>Amorphophallus</i>. In this study, the transcriptomes of <i>A. konjac</i> and <i>A. bulbifer</i> were constructed using a high-throughput Illumina sequencing platform. All 108,651 unigenes with average lengths of 430 nt in A. konjac and 119,678 unigenes with average lengths of 439 nt were generated from 54,986,020 reads and 52,334,098 reads after filtering and assembly, respectively. A total of 54,453 transcripts in <i>A. konjac</i> and 55,525 in <i>A. bulbifier</i> were annotated by comparison with Nr, Swiss-Prot, KEGG, and COG databases after removing exogenous contaminated sequences. A total of 80,332 transcripts differentially expressed between <i>A. konjac</i> and <i>A. bulbifer.</i> The majority of the genes that are associated with konjac glucomannan biosynthetic pathway were identified. Besides, the small RNAs in <i>A. konjac</i> leaves were also obtained by deep sequencing technology. All of 5,499,903 sequences of small RNAs were obtained with the length range between 18 and 30 nt. The potential targets for the miRNAs were also predicted according to the konjac transcripts. Our study provides a systematic overview of the konjac glucomannan biosynthesis genes that are involved in konjac leaves and should facilitate further understanding of the crucial roles of carbohydrate synthesis and other important metabolism pathways in <i>Amorphophallus</i>.</p></div

COG function classification of Unigenes.

<p>COG function classification of Unigenes.</p

Statistics of Glucomannan and starch biosynthesis related genes in Amorphophallus.

<p>Statistics of Glucomannan and starch biosynthesis related genes in Amorphophallus.</p

Statistics of unigene assembly qualities.

<p>All sizes of the Unigenes were calculated.</p