Conjugated polymers with high thermoelectric performance enable the fabrication of low-cost, large-area, low-toxicity, and highly flexible thermoelectric devices. However, compared to their p-type counterparts, n-type polymer thermoelectric materials show much lower performance, which is largely due to inefficient doping and a much lower conductivity. Herein, it is reported that the development of a donor-acceptor (D-A) polymer with enhanced n-doping efficiency through donor engineering of the polymer backbone. Both a high n-type electrical conductivity of 1.30 S cm and an excellent power factor (PF) of 4.65 µW mK are obtained, which are the highest reported values among D-A polymers. The results of multiple characterization techniques indicate that electron-withdrawing modification of the donor units enhances the electron affinity of the polymer and changes the polymer packing orientation, leading to substantially improved miscibility and n-doping efficiency. Unlike previous studies in which improving the polymer-dopant miscibility typically resulted in lower mobilities, the strategy maintains the mobility of the polymer. All these factors lead to prominent enhancement of three orders magnitude in both the electrical conductivity and the PF compared to those of the non-engineered polymer. The results demonstrate that proper donor engineering can enhance the n-doping efficiency, electrical conductivity, and thermoelectric performance of D-A copolymers.

Rice (Oryza sativa L.) is one of the world's most important staple crops and a powerful model system for studying monocot species because of its relatively small genome, rich genomic resources, and a highly efficient transformation system. With the completion of rice genome sequencing, the challenge of the post-genomic era is to systematically analyze the functions of all rice genes. Gene knockout is a frequently used and effective strategy for achieving this goal. Thus, generation of large-scale mutants at the whole-genome level is of great value for both functional genomics and genetic improvement of rice. Traditionally, large numbers of mutants are produced by physical, chemical, or biological mutagenesis. Mutants created by these methods have made enormous contributions to basic plant research and crop improvement. T-DNA insertion (Jeon et al., 2000), TILLING (targeting-induced local lesions in genomes) (Till et al., 2007) and RNAi (RNA interference) (Wang et al., 2013) are the three most common methods of performing genetic studies. T-DNA insertion and TILLING are time-consuming and labor-intensive in generating genome-wide mutant libraries, because large mutagenized populations must be generated to ensure sufficient genome-wide coverage. In addition, the T-DNA insertions occur randomly and often in intergenic and noncoding regions, for TILLING mutants it is difficult to identify the targeted mutations for the observed phenotypes, and the RNAi method only reduces the expression of targeted genes rather than generating the knockout mutants. Recently, a simple and highly efficient genomic engineering tool, the CRISPR (Clustered Regularly Interspaced Palindromic Repeats)/Cas9 system, has been developed; this technology can create small insertions and deletions (indels) in specific target genes and has been applied to many organisms. Because it is an easy and convenient technique, some CRISPR/Cas9 mutant libraries have been developed for genomewide mutation screens in cultured eukaryotic cells (Shalem et al., 2015). However, no large-scale CRISPR/Cas9 mutant libraries have yet been generated in higher plants. Here, we report the construction of a high-throughput CRISPR/Cas9 mutant library in rice and demonstrate its application for identifying gene functions and its potential use for genetic improvement.

A straightforward strategy has been used to construct large BN-embedded π-systems simply from azaacenes. BN heterosuperbenzene derivatives, the largest BN heteroaromatics to date, have been synthesized in three steps. The molecules exhibit curved π-surfaces, showing two different conformations which are self-organized into a sandwich structure and further packed into a π-stacking column. The assembled microribbons exhibit good charge transport properties and photoconductivity, representing an important step toward the optoelectronic applications of BN-embedded aromatics.

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