Cross-links in Carbon Nanotube Assembly Introduced by Using Polyacrylonitrile as Precursor

Individual carbon nanotube (CNT) exhibits extraordinary mechanics. However, the properties of the macroscopic CNT-based structure, such as CNT fibers and films, are far lower than that of individual CNT. One of the main reasons is the weak interaction between tubes and bundles in the CNT assemblies. It is understood that the cross-links in CNT assembly play a key role to improve the performance of CNT-based structure. Different approaches have been taken to create CNT joints. Most of these approaches focus on connecting CNTs by generating new covalent bonding between tubes. In this work, we intend to reinforce the CNT network by locking the contacted CNTs. Polyacrylonitrile (PAN) was used as precursor because PAN can form graphitic structures after carbonization. The freestanding superthin CNT sheet and CNT yarn were used to evaluate the effects of the PAN precursor to form cross-links between CNTs. The tensile strength of CNT yarn is improved when the yarn is partially infiltrated with PAN and consequently carbonated. High-resolution transmission electron microscopy observation of the sheets shows that graphite structures are formed and cross-link CNTs in CNT assembly

Copper/Parylene Core/Shell Nanowire Surface Fastener Used for Room-Temperature Electrical Bonding

The traditional bonding technology in electronic assembly relies on high-temperature processes, such as reflow soldering or curing of adhesives, which result in undesired thermal excursions and residual stress at the bonding interface. Therefore, there is an urgent need to attach electronic components on the circuit board with good mechanical and electrical properties at room temperature. In this paper, a room-temperature electrical surface fastener consisting of copper/parylene core/shell nanowire (NW) arrays were prepared, and van der Waals (VDW) forces were utilized to interconnect the core/shell NWs. Interestingly, the Parylene C film becomes conductive due to dielectric breakdown when the thickness of it is miniaturized to nanoscale. Our electrical surface fastener exhibits high macroscopic adhesion strength (∼25 N/cm²) and low electrical resistance (∼4.22 × 10^–2 Ω·cm²). Meanwhile, a new theoretical model based on VDW forces between the NWs is proposed to explain the adhesion mechanism of the core/shell structure

Toluene catalytic oxidation over gold catalysts supported on cerium-based high-entropy oxides

A series of cerium-based high-entropy oxide catalysts (the ratio of CeO2 and HEO is 1:1) was prepared by a solid-state reaction method, which exploit their unique structural and performance advantages. The Ce-HEO-T samples can achieve 100% toluene conversion rate above 328 oC when they were used as catalysts directly. Subsequently, the Ce-HEO-500 exhibited the lowest temperature for toluene oxidation was used as a support to deposit different amounts of Au for a further performance improvement. Among all of prepared samples, Au/Ce-HEO-500 with a moderate content of Au (0.5 wt%) exhibited the lowest temperature for complete combustion of toluene (260 oC)，which decreased nearly 70 oC compared with Ce-HEO-500 support. Moreover, it also showed excellent stability for 60 h with 98% toluene conversion rate. Most importantly, under the condition of 5 vol.% H2O vapor, the toluene conversion rate remained unchanged and even increased slightly compared with that in dry air, exhibiting excellent water resistance. Combined with the characterizations of XRD, SEM, TEM, BET, Raman, H2-TPR and XPS, it was found that the high dispersion of active Au NPs, the special high-entropy structure and the synergistic effect between Au and Ce, Co, Cu are the key factors when improving the catalytic performance in the Au/Ce-HEO-500 catalyst.</p

Suppression Subtractive Hybridization Reveals Transcript Profiling of Chlorella under Heterotrophy to Photoautotrophy Transition

<div><h3>Background</h3><p>Microalgae have been extensively investigated and exploited because of their competitive nutritive bioproducts and biofuel production ability. <em>Chlorella</em> are green algae that can grow well heterotrophically and photoautotrophically. Previous studies proved that shifting from heterotrophy to photoautotrophy in light-induced environments causes photooxidative damage as well as distinct physiologic features that lead to dynamic changes in <em>Chlorella</em> intracellular components, which have great potential in algal health food and biofuel production. However, the molecular mechanisms underlying the trophic transition remain unclear.</p> <h3>Methodology/Principal Findings</h3><p>In this study, suppression subtractive hybridization strategy was employed to screen and characterize genes that are differentially expressed in response to the light-induced shift from heterotrophy to photoautotrophy. Expressed sequence tags (ESTs) were obtained from 770 and 803 randomly selected clones among the forward and reverse libraries, respectively. Sequence analysis identified 544 unique genes in the two libraries. The functional annotation of the assembled unigenes demonstrated that 164 (63.1%) from the forward library and 62 (21.8%) from the reverse showed significant similarities with the sequences in the NCBI non-redundant database. The time-course expression patterns of 38 selected differentially expressed genes further confirmed their responsiveness to a diverse trophic status. The majority of the genes enriched in the subtracted libraries were associated with energy metabolism, amino acid metabolism, protein synthesis, carbohydrate metabolism, and stress defense.</p> <h3>Conclusions/Significance</h3><p>The data presented here offer the first insights into the molecular foundation underlying the diverse microalgal trophic niche. In addition, the results can be used as a reference for unraveling candidate genes associated with the transition of <em>Chlorella</em> from heterotrophy to photoautotrophy, which holds great potential for further improving its lipid and nutrient production.</p> </div

<i>Chlorella</i> growth and the cellular component temporal pattern characteristics under diverse nutrition transition.

<p>A: Biomass concentration; B: Protein content; C: Chlorophyll content. Error bars represent the mean ± standard deviation of three independent biological replicates.</p

Gene Ontology (GO) annotation of genes obtained from the SSH libraries.

<p>GO predictions identified several categories based on the three terms cellular component, molecular function, and biological process, and were plotted by WEGO. LI represents forward library under the light-induced treatment; HC represents the reverse library under the heterotrophic culture process.</p

Functional classification of the differentially expressed genes in reverse library.

<p>Numbers in parentheses represent the number of ESTs categorized into each group.</p

Functional classification of the differentially expressed genes in forward library.

<p>Numbers in parentheses represent the number of ESTs categorized into each group.</p

Assembly and annotation statistics of the two SSH libraries.

<p>Assembly and annotation statistics of the two SSH libraries.</p

Time course changes on <i>Chlorella</i> physiological features under heterotrophy to photoautotrophy transition.

<p>A: Changes of photosynthesis fluorescence parameters on different light intensity; B: Production of ROS and lipid peroxidation; C: Activities of ROS scavenging enzymes. H: heterotrophy; P: photoautotrophy. Error bars represent the mean ± standard deviation of three independent biological replicates.</p