Thermally Conductive and Electrically Insulated Silicone Rubber Composites Incorporated with Boron Nitride-Multilayer Graphene Hybrid Nanofiller.

Thermally conductive and electrically insulating composites are important for the thermal management of new generation integrated and miniaturized electronic devices. A practical and eco-friendly electrostatic self-assembly method was developed to prepare boron nitride-multilayer graphene (BN-MG) hybrid nanosheets. Then, BN-MG was filled into silicone rubber (SR) to fabricate BN-MG/SR composites. Compared with MG/SR composites with the same filler loadings, BN-MG/SR composites exhibit dramatically enhanced electrical insulation properties while still maintaining excellent thermal conductivity. The BN-MG/SR with 10 wt.% filler loading shows a thermal conductivity of 0.69 W·m-1·K-1, which is 475% higher than that of SR (0.12 W·m-1·K-1) and only 9.2% lower than that of MG/SR (0.76 W·m-1·K-1). More importantly, owing to the electron blocking effect of BN, the electron transport among MG sheets is greatly decreased, thus contributing to the high-volume resistivity of 4 × 1011 Ω cm for BN-MG/SR (10 wt.%), which is fourorders higher than that of MG/SR (2 × 107 Ω·cm). The development of BN-MG/SR composites with synergetic properties of high thermal conductivity and satisfactory electrical insulation is supposed to be a promising candidate for practical application in the electronic packaging field.

Synergetic integration of thermal conductivity and flame resistance in nacre-like nanocellulose composites.

Highly thermally conductive and flame resistant nanocellulose-based composites can synchronously achieve efficient thermal dissipation and low fire hazards of electronic devices, which shows great promise in next-generation green and flexible electronics. However, it has long been intractable to optimize the high thermal conductivity (TC) and flame resistance simultaneously. Herein, synergetic integration of high TC and flame resistance in nacre-like nanocellulose composites has been successfully achieved by the vacuum-assisted filtration of cellulose nanofibers (CNFs) and functionalized boron nitride nanosheets (BNNS-p-APP). Benefiting from the highly oriented hierarchical microstructure, strong hydrogen-bonding interaction, and successful immobilization of ammonium polyphosphate (APP), the as-obtained CNFs/BNNS-p-APP composite film achieves a high in-plane TC of 9.1 W m-1 K-1 and outstanding flame resistance. Meantime, this eco-friendly nanocellulose-based composite also exhibits remarkable flexibility, folding endurance, and mechanical robustness, robustness, which may open up a new opportunity for the thermal management of flexible electronics.

Room temperature phosphorescence from Si-doped-CD-based composite materials with long lifetimes and high stability.

C-dot-based composites with phosphorescence have been widely reported due to their attractive potential in various applications. But easy quenching of phosphorescence induced by oxygen or instability of matrices remained a tricky problem. Herein, we reported a Si-doped-CD (Si-CD)-based RTP materials with long lifetime by embedding Si-CDs in sulfate crystalline matrices. The resultant Si-CD@sulfate composites exhibited a long lifetime up to 1.07 s, and outstanding stability under various ambient conditions. The intriguing RTP phenomenon was attributed to the C = O bond and the doping of Si element due to the fact that sulfates could effectively stabilize the triplet states of Si-CDs, thus enabling the intersystem crossing (ISC). Meanwhile, we confirmed that the ISC process and phosphorescence emission could be effectively regulated based on the heavy atom effect. This research introduced a new perspective to develop materials with regulated RTP performance and high stability.

A green approach for tunable fluorescent and superhydrophobic monodisperse polysilsesquioxane spheres.

HYPOTHESIS: Typically, calcination at high temperature could bring fluorescence to hybrid silica spheres prepared with 3-aminopropyltriethoxysilane and tetraethylorthosilicate, but they tended to be hydrophilic. Further extra modification is required to gain superhydrophobicity, which might probably block the fluorescence. Short side organic chains are very thermostable at high temperature. Therefore, it might be possible to produce superhydrophobic and fluorescent hybrid silica spheres through the co-condensation of organosilanes with short side organic chains and calcination at high temperature. EXPERIMENTS: Methyltrimethoxysilane (MTMS) and vinyltrimethoxysilane (VTMS) were co-condensed to prepare polysilsesquioxane (PSQ) spheres, which were subsequently calcinated at high temperature. The impact of MTMS/VTMS ratio on the chemical structures, fluorescence and wettability was investigated, and the applications of PSQ spheres were expanded. FINDINGS: The PSQ spheres with the ratio of MTMS/VTMS as 3/1 and 2/2 exhibited strong fluorescence, and the calcination did not destroy the superhydrophobicity for the remaining of abundant methyl, vinyl, or ethyl groups. Our study provides an extremely green, simple and effective approach to prepare thermostable, fluorescent and superhydrophobic monodisperse silica spheres without using rare earth element, gold, conjugated polymer, phorsphore, fluoride chemical or organic solvent.

Dual Bio-Inspired Design of Highly Thermally Conductive and Superhydrophobic Nanocellulose Composite Films.

Highly thermally conductive, electrically insulating, and flexible nanocellulose composite films are crucially significant for the thermal management of next-generation green electronics. However, the intrinsic hygroscopicity of nanocellulose poses a daunting challenge to the reliability and structural stability of electronic products. To address these issues, herein, a dual bio-inspired design was innovatively introduced to fabricate highly thermally conductive and superhydrophobic nanocellulose-based composite films via vacuum-assisted self-assembly of cellulose nanofibers (CNFs) and hydroxylated boron nitride nanosheets (OH-BNNS) and subsequent hydrophobic modification. Driven by the highly orderly hierarchical architecture and a strong hydrogen bonding interaction, the laminated CNF-based composite films with 50 wt % OH-BNNS show a high in-plane thermal conductivity (15.13 W/mK), which results in a 505% enhancement compared with the pure CNF films. On the other hand, the rough surface combined with a low surface energy modifier endows CNF/OH-BNNS composite films with unique superhydrophobicity (contact angle over 155°) and a simultaneous self-cleaning function. Furthermore, the as-fabricated multifunctional CNF/OH-BNNS composite films were designed as a flexible printed circuit board to simulate the potential applications in the field of cooling electronic devices. The development of CNF/OH-BNNS composite films with synergetic properties of high thermal conductivity and superhydrophobicity may shed light on the functional thermal management materials and offer an innovative insight toward fabricating multifunctional nanocomposites via a dual bio-inspired design.

Highly monodisperse polysilsesquioxane spheres: synthesis and application in cotton fabrics.

Highly monodisperse methyl-functionalized, vinyl-functionalized, and thiol-functionalized polysilsesquioxane spheres (MPSQ, VPSQ, and MPPSQ spheres) have been successfully prepared through a one-pot emulsion approach with one organosilane as sole precursor in aqueous medium. The morphology, size distribution, and chemical structure were characterized by SEM, DLS, FT-IR, solid NMR, XRD, etc. The thermodecomposition and hydrophobicity of these spheres were investigated with TGA and water contact angle measurement. Our research turns out that the organofunctional groups play a key role in thermostability and hydrophobicity of polysilsesquioxane spheres, MPSQ, and VPSQ spheres possess better thermostability than MPPSQ spheres, the order of hydrophobicity is as follows: MPSQ>VPSQ>MPPSQ. Cotton fabrics can become superhydrophobic when treated with methyl- or vinyl-functional silica spheres.

Surfactant-free ionic liquid-based nanofluids with remarkable thermal conductivity enhancement at very low loading of graphene.

We report for the first time the preparation of highly stable graphene (GE)-based nanofluids with ionic liquid as base fluids (ionic liquid-based nanofluids (Ionanofluids)) without any surfactant and the subsequent investigations on their thermal conductivity, specific heat, and viscosity. The microstructure of the GE and MWCNTs are observed by transmission electron microscope. Thermal conductivity (TC), specific heat, and viscosity of these Ionanofluids were measured for different weight fractions and at varying temperatures, demonstrating that the Ionanofluids exhibit considerably higher TC and lower viscosity than that of their base fluids without significant specific heat decrease. An enhancement in TC by about 15.5% and 18.6% has been achieved at 25 °C and 65 °C respectively for the GE-based nanofluid at mass fraction of as low as 0.06%, which is larger than that of the MWCNT-dispersed nanofluid at the same loading. When the temperature rises, the TC and specific heat of the Ionanofluid increase clearly, while the viscosity decreases sharply. Moreover, the viscosity of the prepared Ionanofluids is lower than that of the base fluid. All these advantages of this new kind of Ionanofluid make it an ideal fluid for heat transfer and thermal storage.

[Isolation and characterization of SIR73 gene fragment in salt resistant mutant of wheat involved in salt stress].

cDNA-AFLP (amplified fragment length polymorphism) is used to isolate genes differentially expressed in two wheat lines with the different resistance to NaCl derived from a single seed. A lot of cDNA fragments related to salt tolerance are obtained. Of with the number 73 cDNA fragment encodes for a transcription factors with an 32% similarity to human transcription factors in the relative amino acid which is named SIR73. Northern analysis confirms that SIR73 is strongly induced by NaCl stress and the expression in SR is more strongly induced than in SS.SIR73 may be involved in the regulation of gene expression in salt stress in wheat.

AhSL28, a senescence- and phosphate starvation-induced S-like RNase gene in Antirrhinum.

Several species of higher plants have been found to contain S-like ribonucleases (RNases), which are homologous to S-RNases controlling self-incompatibility. No S-like RNase genes have been isolated from self-incompatible Antirrhinum. To investigate the relationship between S- and S-like RNases, we cloned a gene named AhSL28 encoding an S-like RNase in Antirrhinum. Amino acid sequence, genomic structure and phylogenetic analyses indicated that AhSL28 is most similar to RNS2, an S-like RNase from Arabidopsis thaliana and formed a distinct subclass together with several other S-like RNases within the S-RNase superfamily. Unlike S-RNase genes in Antirrhinum, AhSL28 is not only expressed in pistils but also in leaves, petals, sepals and anthers, in particular, showing a strong expression in vascular tissues and transmitting track. Moreover, its RNA transcripts were induced during leaf senescence and phosphate (Pi) starvation but not by wounding, indicating that AhSL28 plays a role in remobilizing Pi and other nutrients, particularly when cells senesce and are under limited Pi conditions in Antirrhinum. Possible evolutionary relations of S- and S-like RNases as well as signal transduction pathways related to S-like RNase action are discussed.

An F-box gene linked to the self-incompatibility (S) locus of Antirrhinum is expressed specifically in pollen and tapetum.

In many flowering plants, self-fertilization is prevented by an intraspecific reproductive barrier known as self-incompatibility (SI), that, in most cases, is controlled by a single multiallelic S locus. So far, the only known S locus product in self-incompatible species from the Solanaceae, Scrophulariaceae and Rosaceae is a class of ribonucleases called S RNases. Molecular and transgenic analyses have shown that S RNases are responsible for pollen rejection by the pistil but have no role in pollen expression of SI, which appears to be mediated by a gene called the pollen self-incompatibility or Sp gene. To identify possible candidates for this gene, we investigated the genomic structure of the S locus in Antirrhinum, a member of the Scrophulariaceae. A novel F-box gene, AhSLF-S2, encoded by the S2 allele, with the expected features of the Sp gene was identified. AhSLF-S2 is located 9 kb downstream of S2 RNase gene and encodes a polypeptide of 376 amino acids with a conserved F-box domain in its amino-terminal part. Hypothetical genes homologous to AhSLF-S2 are apparent in the sequenced genomic DNA of Arabidopsis and rice. Together, they define a large gene family, named SLF (S locus F-box) family. AhSLF-S2 is highly polymorphic and is specifically expressed in tapetum, microspores and pollen grains in an allele-specific manner. The possibility that Sp encodes an F-box protein and the implications of this for the operation of self-incompatibility are discussed.