Electromagnetic Shielding Enhancement of Butyl Rubber/Single-Walled Carbon Nanotube Composites via Water-Induced Modification.

Electromagnetic properties of polymer composites strongly depend on the loading amount and the completeness of the filler's dispersive structure. Improving the compatibility of single-walled carbon nanotubes (SWCNTs) with isobutylene butyl rubber (IIR) is a good solution to mitigate aggregation. The change in configuration of poly-oxyethylene octyl phenol ether (OP-10) was induced using water as the exposed hydrophilic groups linking with water molecules. The SWCNT and IIR/SWCNT composites were then prepared via wetly-melt mixing at a relatively high temperature to remove water, and they were then mixed with other agents after vacuum drying and cured. The SWCNTs were dispersed uniformly to form a good network for a lower percolation threshold of the wave-absorbing property to 2 phr from 8 phr. With 8 phr SWCNTs, the tensile strength of the material improved significantly from 7.1 MPa to 15.1 MPa, and the total electromagnetic shielding effectiveness of the material was enhanced to 23.8 dB, a 3-fold increase compared to the melt-mixed material. It was demonstrated that water-induced modification achieved good dispersion of SWCNTs for electromagnetic shielding enhancement while maintaining a wide damping temperature range from -55 °C to 40 °C with a damping factor over 0.2.

Transformation from Electromagnetic Inflection to Absorption of Silicone Rubber and Accordion-Shaped Ti3C2MXene Composites by Highly Electric Conductive Multi-Walled Carbon Nanotubes.

Electromagnetic (EM) pollution becomes more penetrating in daily life and work due to more convenience provided by multi-electrical devices, as does secondary pollution caused by electromagnetic reflection. EM wave absorption material with less reflection is a good solution to absorb unavoidable EM radiation or reduce it from the source. Filled with two-dimensional Ti3SiC2MXenes, silicone rubber (SR)composite demonstrated a good electromagnetic shielding effectiveness of 20 dB in the X band by melt-mixing processes for good conductivity of more than 10-3 S/cm and displayed dielectric properties and a low magnetic permeability; however, the reflection loss was only -4 dB. By the combination of one-dimensional highly electric conductive multi-walled carbon nanotubes (HEMWCNTs) and MXenes, the composites achieved the transformation from electromagnetic inflection to an excellent absorbing performance to reach a minimum reflection loss of -30.19 dB due to electric conductivity of above 10-4 S/cm, a higher dielectric constant, and more loss in both dielectric and magnetic properties. Ni-added multi-walled carbon nanotubes were not able to achieve the transformation. The as-prepared SR/HEMWCNT/MXene composites have potential application prospects in protective layers, which can be used for electromagnetic wave absorption, electromagnetic interference suppression of devices, and stealth of the equipment.

Oxygen-selective adsorption on high-silica LTA zeolite.

The adsorption capacity of O2 and N2 on a LTA-type zeolite can be significantly affected by the change of its Si/Al ratio. With the increase in Si/Al ratio and the decrease in the amount of Na+, the protonated high-silica LTA zeolite changes from being a N2-selective sorbent to an O2-selective sorbent to reverse the O2 and N2 selectivity.

Chaetoindicins A-C, three isoquinoline alkaloids from the fungus Chaetomium indicum.

[structure: see text] Chaetoindicins A-C (1-3), three isoquinolines with novel skeletons, were isolated from the solid-state fermented culture of Chaetomiumindicum. Their structures were elucidated on the basis of spectral data. X-ray crystallographic analysis confirmed the structure of 2.

Directed calcium chloride coalescence method for preparation of silver nanocubes.

Controlling the size, shape, and structure of metal nanoparticles is very important because of the strong correlation between these parameters and their resulting optical, electrical, and catalytic properties. This paper describes a directed calcium chloride coalescence method, based upon incubating a silver colloid with an aqueous solution of CaCl(2), for preparation of silver nanocubes with a particle size of 270 to 950 nm. The method avoids the use of nonvolatile surfactants and polymers, which may be adsorbed onto the silver nanocubes and interfere with their possible applications in catalysis and analytical devices based on surface-enhanced Raman scattering (SERS) spectroscopy. The nanocubes show good SERS activity in the presence of adsorbed 4-mercaptobenzoic acid (4-MBA) with excitation at 632.8 nm, and the enhancement factor reaches approximately 7 x 10(5). The nanocubes are produced in a simple and cost-effective way, and they are expected to play an important role in the development of SERS-based analytical devices. The method may represent a novel route for preparation of metal nanocubes, which is a subject of intense interest.

Chaetocochins A-C, epipolythiodioxopiperazines from Chaetomium cochliodes.

Three new epipolythiodioxopiperazines, chaetocochins A (1), B (2), and C (3), along with dethio-tetra (methylthio) chetomin (4) and chetomin (5), were isolated from the ethyl acetate extract of the solid-state fermented rice culture of the fungus Chaetomium cochliodes. Their structures were elucidated on the basis of spectroscopic analysis. Compounds 1, 3, and 4 exhibited significant cytotoxicity in vitro against cancer cell lines Bre-04, Lu-04, and N-04.

Sesterterpenoids, terretonins A-D, and an alkaloid, asterrelenin, from Aspergillus terreus.

Four new sesterterpenoids, terretonins A-D (1-4), and a new alkaloid, asterrelenin (5), together with five known compounds, were isolated from the ethyl acetate extract of a solid-state fermented culture of Aspergillus terreus. Their structures were elucidated on the basis of spectroscopic analysis. The structures of 1, 2, and 5 were confirmed by X-ray crystallographic analysis.