Integrative Analysis of Transcriptomic and Proteomic Changes Related to Cytoplasmic Male Sterility in Spring Stem Mustard (Brassica juncea var. tumida Tsen et Lee).

The development of flower and pollen is a complex biological process that involves multiple metabolic pathways in plants. In revealing novel insights into flower and pollen development underlying male sterility (MS), we conducted an integrated profiling of gene and protein activities in developing buds in cytoplasmic male sterile (CMS) mutants of mustard (Brassica juncea). Using RNA-Seq and label-free quantitative proteomics, 11,832 transcripts and 1780 protein species were identified with significant differential abundance between the male sterile line 09-05A and its maintainer line 09-05B at the tetrad stage and bi-nucleate stage of B. juncea. A large number of differentially expressed genes (DEGs) and differentially abundant proteins (DAPs) involved in carbohydrate and energy metabolism, including starch and sucrose metabolism, tricarboxylic acid (TCA) cycle, glycolysis, and oxidoreductase activity pathways, were significantly downregulated in 09-05A buds. The low expression of these DEGs or functional loss of DAPs, which can lead to an insufficient supply of critical substrates and ATP, could be associated with flower development, pollen development, and changes in fertility in B. juncea. Therefore, this study provided transcriptomic and proteomic information of pollen abortion for B. juncea and a basis for further research on the molecular regulatory mechanism of MS in plants.

2D Self-Assembly of Large-Sized Inorganic Nanosheets Leading to Enhanced Power Factors in Earth-Abundant Cu3SbSe4-Based Flexible Hybrid Films.

Fabrication of large-sized inorganic nanosheets is an efficient strategy to promote carrier transportation in flexible thermoelectric (TE) films. Herein, we report the self-assembly of large-sized Cu3SbSe4 nanosheets by using a Se nanowire template via wet chemical synthesis and then vacuum-assisted filter these plate-like microcrystals on nylon to prepare Cu3SbSe4 flexible thermoelectric (TE) hybrid films. SEM reveals that the as-synthesized Cu3SbSe4 powders by using Se nanowires as selenium sources presented 2D plate-like micron structures uniformly and tightly self-assembled by acute triangle-like nanoparticles. Furthermore, XPS evidences that extra Sb vacancies are generated in the unit cell of Cu3SbSe4 crystals synthesized by using the Se NW template, resulting in the shrinkage of the unit cell and the narrowing interplanar spacing, which are characterized by XRD and TEM. As a result, both carrier concentration and carrier mobility have been significantly improved. The high carrier concentration is proved to originate from the extra carriers induced by Sb vacancies, and the high carrier mobility of the film is mainly ascribed to its continuous grain boundaries in the plate-like microcrystal morphology. The large-sized nanosheet Cu3SbSe4/nylon hybrid film (CSS MPs) exhibits a high power factor (PF) of 235.45 µW m-1 K-2 at 400 K, which is 4.23 times higher than that of the Cu3SbSe4/nylon hybrid film (CSS NPs) where Cu3SbSe4 crystals are synthesized by using raw Se particles. This work reveals a novel approach to prepare plate-like Se-based semiconductors, which requires both high carrier concentration and high carrier mobility.

Thermoelectric Characteristics of Self-Supporting WSe2-Nanosheet/PEDOT-Nanowire Composite Films.

Conducting polymer poly(3,4-ethylenedioxythiophene) nanowires (PEDOT NWs) were synthesized by a modified self-assembled micellar soft-template method, followed by fabrication by vacuum filtration of self-supporting exfoliated WSe2-nanosheet (NS)/PEDOT-NW composite films. The results showed that as the mass fractions of WSe2 NSs increased from 0 to 20 wt % in the composite films, the electrical conductivity of the samples decreased from ∼1700 to ∼400 S cm-1, and the Seebeck coefficient increased from 12.3 to 23.1 µV K-1 at 300 K. A room-temperature power factor of 44.5 µW m-1 K-2 was achieved at 300 K for the sample containing 5 wt % WSe2 NSs, and a power factor of 67.3 µW m-1 K-2 was obtained at 380 K. The composite film containing 5 wt % WSe2 NSs was mechanically flexible, as shown by its resistance change ratio of 7.1% after bending for 500 cycles at a bending radius of 4 mm. A flexible thermoelectric (TE) power generator containing four TE legs could generate an output power of 52.1 nW at a temperature difference of 28.5 K, corresponding to a power density of ∼0.33 W/m2. This work demonstrates that the fabrication of inorganic nanosheet/organic nanowire TE composites is an approach to improve the TE properties of conducting polymers.

Flexible Thermoelectric Reduced Graphene Oxide/Ag2S/Methyl Cellulose Composite Film Prepared by Screen Printing Process.

As an organic-inorganic thermoelectric composite material, a flexible, reduced graphene oxide (rGO)/silver sulfide (Ag2S)/methyl cellulose (MC) film was fabricated by a two-step method. Firstly, a rGO/Ag2S composite powder was prepared by a chemical synthesis method, and then, the rGO/Ag2S/MC composite film was prepared by a combined screen printing and annealing treatment process. The rGO and rGO/Ag2S composite powders were evenly dispersed in the rGO/Ag2S/MC composite films. A power factor of 115 µW m-1 K-2 at 520 K was acquired for the rGO/Ag2S/MC composite film, which is ~958 times higher than the power factor at 360 K (0.12 µW m-1 K-2), mainly due to the significant increase in the electrical conductivity of the composite film from 0.006 S/cm to 210.18 S/cm as the test temperature raised from 360 K to 520 K. The as-prepared rGO/Ag2S/MC composite film has a good flexibility, which shows a huge potential for the application of flexible, wearable electronics.

Effects of Preparation Methods on the Thermoelectric Performance of SWCNT/Bi2Te3 Bulk Composites.

Single-walled carbon nanotube (SWCNT)/Bi2Te3 composite powders were fabricated via a one-step in situ reductive method, and their corresponding bulk composites were prepared by a cold-pressing combing pressureless sintering process or a hot-pressing process. The influences of the preparation methods on the thermoelectric properties of the SWCNT/Bi2Te3 bulk composites were investigated. All the bulk composites showed negative Seebeck coefficients, indicating n-type conduction. A maximum power factor of 891.6 µWm-1K-2 at 340 K was achieved for the SWCNT/Bi2Te3 bulk composites with 0.5 wt % SWCNTs prepared by a hot-pressing process, which was ~5 times higher than that of the bulk composites (167.7 µWm-1K-2 at 300 K) prepared by a cold-pressing combing pressureless sintering process, and ~23 times higher than that of the bulk composites (38.6 µWm-1K-2 at 300 K) prepared by a cold-pressing process, mainly due to the enhanced density of the hot-pressed bulk composites.

High Performance and Flexible Polyvinylpyrrolidone/Ag/Ag2Te Ternary Composite Film for Thermoelectric Power Generator.

In this work, polyvinylpyrrolidone (PVP) coated Ag-rich Ag2Te nanowires (NWs) were synthesized by a wet chemical method using PVP coated Te NWs as templates, and a flexible PVP/Ag/Ag2Te ternary composite film on a nylon membrane was prepared by vacuum assisted filtration, followed by heat treatment. TEM and STEM observations of the focused ion beam prepared sample reveal that the composite film shows a porous network-like structure and that the Ag and Ag2Te exist as nanoparticles and NWs, respectively, both bonded with PVP. The Ag nanoparticles are formed by separation of the Ag-rich Ag2Te NWs during the heat treatment. For the composite film starting from a Ag/Te initial molar ratio of 6:1, a high power factor of 216.5 µW/mK2 is achieved at 300 K, and it increases to 370.1 µW/mK2 at 393 K. Bending tests demonstrate excellent flexibility of the hybrid film. A thermoelectric (TE) prototype composed of five legs of the hybrid film is assembled, and a maximum output power of 469 nW is obtained at a temperature gradient of 39.6 K, corresponding to a maximum power density of 341 µW/cm2. This work provides an effective route to a composite film with high TE performance and excellent flexibility for wearable TE generators.