A transparent silica colloidal crystal/PDMS composite and its application for crack suppression of metallic coatings.

A silica colloidal crystal (SCC)-polydimethylsiloxane (PDMS) composite with a heterogeneous surface of silica and PDMS was prepared by spreading a premixed PDMS solution on the 3D structured SCCs and curing the solution in-situ. Although the SCCs had a light blue color, the obtained composite of SCC and PDMS, due to the close effective refractive indexes of the materials, was colorless and transparent; the UV-vis spectra indicated a negligible effect of the added SCC on the transmittance of the PDMS sheet (1% reduction). Interestingly, the transparent composite sheet became translucent under stress and became clear again when relaxed. It was found that the wrinkles formed on the surface under stress were responsible for the optical change; and, the formation of the wrinkles was ascribed to the rigid nature of the SCC layer embedded in PDMS. We had applied this SCC/PDMS composite as a substrate to support a thin gold film of nanoscale thickness and found that the embedded SCC layer worked well as a transitional interface for bonding materials of mismatched mechanical properties. The incorporation of SCC layer significantly suppressed the crack generation and propagation of the gold film. The results demonstrated a potential approach for fabricating compliant and crackfree metallic films on polymeric substrates.

Durable Microstructured Surfaces: Combining Electrical Conductivity with Superoleophobicity.

In this study, electrically conductive and superoleophobic polydimethylsiloxane (PDMS) has been fabricated through embedding Ag flakes (SFs) and Ag nanowires (SNWs) into microstructures of the trichloroperfluorooctylsilane (FDTS)-blended PDMS elastomer. Microstructured PDMS surfaces became conductive at the percolation surface coverage of 3.0 × 10(-2) mg/mm(2) for SFs; the highest conductivity was 1.12 × 10(5) S/m at the SFs surface coverage of 6.0 × 10(-2) mg/mm(2). A significant improvement of the conductivity (increased 3 times at the SNWs fraction of 11%) was achieved by using SNWs to replace some SFs because of the conductive pathways from the formed SNWs networks and its connections with SFs. These conductive fillers bonded strongly with microstructured FDTS-blended PDMS and retained surface properties under the sliding preload of 8.0 N. Stretching tests indicated that the resistance increased with the increasing strains and returned to its original state when the strain was released, showing highly stretchable and reversible electrical properties. Compared with SFs embedded surfaces, the resistances of SFs/SNWs embedded surfaces were less dependent on the strain because of bridging effect of SNWs. The superoleophobicity was achieved by the synergetic effect of surface modification through blending FDTS and the microstructures transferred from sand papers. The research findings demonstrate a simple approach to make the insulating elastomer to have the desired surface oleophobicity and electrical conductivity and help meet the needs for the development of conductive devices with microstructures and multifunctional properties.

Protection of cells from nitric oxide-mediated apoptotic death by glutathione C60 derivative.

The influence of the glutathione C60 derivative on the cytotoxicity of a highly reactive free radical NO (nitric oxide) has been investigated. Consistent with its cytoprotective abilities, the derivative scavenges ROS (reactive oxygen species) and RNS (reactive nitrogen species) both in vitro and under cell-free conditions. Moreover, the glutathione C60 derivative protected PC12 cells from the cytotoxic effect of the NO-releasing compound, SNP (sodium nitroprusside). Addition of glutathione C60 derivative alone did not induce apoptosis and necrosis. The results suggest that the glutathione C60 derivative has the potential to prevent NO-mediated cell death without evident toxicity.

Photodynamic anticancer activities of water-soluble C(60) derivatives and their biological consequences in a HeLa cell line.

Photodynamic therapy is an emerging, externally activatable, treatment modality for various diseases, especially for cancer therapy. The photodynamic activities of tumor targeting water-soluble C(60) derivatives (WSFD) were evaluated on HeLa cells. To overcome the poor solubility, biocompatibility and selectivity of C(60), we modified C(60) with l-phenylalanine, folic acid and l-arginine. Consistent with their photodynamic abilities, WSFD generated the reactive oxygen species after irradiation both in water and in vitro. No dark cytotoxicity was observed using 5µg/mL WSFD during long incubation time. Furthermore, the uptake of WSFD into HeLa cells was much more than normal cells, which indicated the WSFD had selectivity to tumor cells. Investigation of the possible photodynamic activities of WSFD demonstrated that they expressed photokilling activities by raising the level of (1)O(2)/O(2)(-) under visible light irradiation. In parallel, following exposure of cells to WSFD and irradiation, a marked decrease in mitochondrial membrane potential, cell viability, activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), as well as increased malondialdehyde (MDA) production were observed. Moreover, WSFD caused significant elevation in caspase-3 activity, and induced apoptotic death. Experiments demonstrated that both chemical properties, such as the chemical structure of adduct and addend numbers, and physical properties, such as degree of aggregation, influenced the ROS-generation abilities, cellular uptake and photodynamic activities of WSFD. The results suggest that WSFD have the potential application in cancer cell inactivation by photodynamic therapy.

A giant polyaluminum species S-Al32 and two aluminum polyoxocations involving coordination by sulfate ions S-Al32 and S-K-Al13.

The giant polyaluminum species [Al32O8(OH)60(H2O)28(SO4)2](16+) (S-Al32) and [Al13O4(OH)25(H2O)10(SO4)](4+) (S-K-Al13) [S means that sulfate ions take part in coordination of the aluminum polycation; K represents the Keggin structure] were obtained in the structures of [Al32O8(OH)60(H2O)28(SO4)2][SO4]7[Cl]2·30H2O and [Al13O4(OH)25(H2O)10(SO4)]4[SO4]8·20H2O, respectively. They are the first two aluminum polyoxocations coordinated by sulfate ions. The "core-shell" structure of S-Al32 is similar to that of Al30, but the units are linked by two [Al(OH)2(H2O)3(SO4)](-) groups with replacement of four η(1)-H2O molecules. The structure of S-K-Al13 is similar to the well-known structure of ε-K-Al13, but the units are linked by two (SO4(2-))0.5 with replacement of a H3O(+) ion. It was shown that strong interaction exists between the polyoxocations and counterions. On the basis of their structural features and preparation conditions, a formation and evolution mechanism (from ε-K-Al13 to S-K-Al13 and S-Al32) has been proposed. A local basification degree symmetrical equalization principle was extracted based on a comparison of the calculated results of the local basification degree for each central Al(3+) ion included in a polycation. They can be used to explain how the two aluminum species are formed and evolved and why the sulfate ions can coordinate to them and to predict where the OH-bridging positions will be upon further hydrolysis.