Patterned growth of carbon nanotubes on Si substrates without predeposition of metal catalysts

Aligned carbon nanotubes (CNTs) can be readily synthesized on quartz or silicon-oxide-coated Si substrates using a chemical vapor deposition method, but it is difficult to grow them on pure Si substrates without predeposition of metal catalysts. We report that aligned CNTs were grown by pyrolysis of iron phthalocyanine at 1000 °C on the templates created on Si substrates with simple mechanical scratching. Scanning electron microscopy and x-ray energy spectroscopy analysis revealed that the trenches and patterns created on the surface of Si substrates were preferred nucleation sites for nanotube growth due to a high surface energy, metastable surface structure, and possible capillarity effect. A two-step pyrolysis process maintained Fe as an active catalyst.

An effective approach to grow boron nitride nanowires directly on stainless-steel substrates

When growing one-dimensional (1D) nanomaterials via the vapour–liquid–solid (VLS) model, the substrates usually need to be coated with a layer of catalyst film. In this study, however, an effective approach for the synthesis of boron nitride (BN) nanowires directly onto commercial stainless-steel foils has been demonstrated. Growth occurs by heating boron and zinc oxide (ZnO) powders at 1100 °C under a mixture of nitrogen and hydrogen gas flow (200 ml min−1). The stainless-steel foils played an additional role of catalyst besides substrate during the VLS growth of these BN nanowires. The as-synthesized nanowires emit strong photoluminescence (PL) bands at 515, 535 and 728 nm. In addition, we found that the gas flow rate and the hydrogen content in the gas mixture strongly affected the diameter and yield of the nanowires by changing the relative concentration of the nanowire growth species in the chamber.

Scratching carbon nanotubes onto Si substrates

Large-scale, high-density, and patterned carbon nanotubes (CNTs) on both pure Si and quartz (SiO2) substrates have been produced using different approaches. The CNTs were synthesized by pyrolysis of the ball-milled iron phthalocyanine (FePc) in a tube furnace under a Ar-5% H2 gas flow. Because patterned CNTs are difficult to grow directly on smooth and perfect single-crystalline Si wafer surface, mechanical scratches were created to help the selective deposition and growth of CNTs on the scratched areas. This simple process does not require pre-deposition of any metal catalysts. For SiO2 substrates, which can be readily covered by a CNT film, patterned CNTs are produced using a TEM grid as mask to cover the areas where CNTs are not needed. The growth temperature and vapor density have strong influence on the patterned CNT formation. The scratch areas with a special structure and a higher surface energy help the selective nucleation of CNTs.

Substrates and inhibitors of human multidrug resistance associated proteins and the implications in drug development

Human contains 49 ATP-binding cassette (ABC) transporter genes and the multidrug resistance associated proteins (MRP1/ABCC1, MRP2/ABCC2, MRP3/ABCC3, MRP4/ABCC4, MRP5/ABCC5, MRP6/ABCC6, MRP7/ABCC10, MRP8/ABCC11 and MRP9/ABCC12) belong to the ABCC family which contains 13 members. ABCC7 is cystic fibrosis transmembrane conductance regulator; ABCC8 and ABCC9 are the sulfonylurea receptors which constitute the ATP-sensing subunits of a complex potassium channel. MRP10/ABCC13 is clearly a pseudo-gene which encodes a truncated protein that is highly expressed in fetal human liver with the highest similarity to MRP2/ABCC2 but without transporting activity. These transporters are localized to the apical and/or basolateral membrane of the hepatocytes, enterocytes, renal proximal tubule cells and endothelial cells of the blood-brain barrier. MRP/ABCC members transport a structurally diverse array of important endogenous substances and xenobiotics and their metabolites (in particular conjugates) with different substrate specificity and transport kinetics. The human MRP/ABCC transporters except MRP9/ABCC12 are all able to transport organic anions, such as drugs conjugated to glutathione, sulphate or glucuronate. In addition, selected MRP/ABCC members may transport a variety of endogenous compounds, such as leukotriene C(4) (LTC(4) by MRP1/ABCC1), bilirubin glucuronides (MRP2/ABCC2, and MRP3/ABCC3), prostaglandins E1 and E2 (MRP4/ABCC4), cGMP (MRP4/ABCC4, MRP5/ABCC5, and MRP8/ABCC11), and several glucuronosyl-, or sulfatidyl steroids. In vitro, the MRP/ABCC transporters can collectively confer resistance to natural product anticancer drugs and their conjugated metabolites, platinum compounds, folate antimetabolites, nucleoside and nucleotide analogs, arsenical and antimonial oxyanions, peptide-based agents, and in concert with alterations in phase II conjugating or biosynthetic enzymes, classical alkylating agents, alkylating agents. Several MRP/ABCC members (MRPs 1-3) are associated with tumor resistance which is often caused by an increased efflux and decreased intracellular accumulation of natural product anticancer drugs and other anticancer agents. Drug targeting of these transporters to overcome MRP/ABCC-mediated multidrug resistance may play a role in cancer chemotherapy. Most MRP/ABCC transporters are subject to inhibition by a variety of compounds. Based on currently available preclinical and limited clinical data, it can be expected that modulation of MRP members may represent a useful approach in the management of anticancer and antimicrobial drug resistance and possibly of inflammatory diseases and other diseases. A better understanding of their substrates and inhibitors has important implications in development of drugs for treatment of cancer and inflammation.

Managing alternative stable states in constructed wetlands using artificial substrates

Algal blooms are a management concern in shallow water bodies. This project investigated the use of artificial substrates to enhance biofilm growth and shift primary production from the open water to artificial surfaces. This resulted in a shift from algal dominated wetland back to a clear water macrophyte dominated wetland.

Interfacial chemistry and adhesion between titanium dioxide nanotube layers and titanium substrates

Interfacial chemistry and adhesion between titanium dioxide (TiO₂) nanotube layers and titanium (Ti) substrates were studied in this Article. TiO₂ nanotube layers were produced on pure Ti by anodization and annealed in air for different time durations. The adhesion of the TiO₂ nanotube layers was then investigated by Rockwell C indentation test. Results show that adhesion of TiO₂ nanotube layers improved with the extension of annealing time. This improvement in adhesion of TiO₂ nanotube layers was analyzed from the viewpoint of interfacial chemistry using energy dispersive X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). It suggests that more Ti-O bonds formed in the interface after annealing, and this led to the improved adhesion of the TiO₂ nanoube layers.

Direct measurement of surface forces between sapphire crystals in aqueous solutions

Measurements are presented of the electrical double layer and van der Waals forces between the (0001) surfaces of two single-crystal sapphire platelets immersed in an aqueous solution of NaCl at pH values from 6.7 to 11. The results fit the standard Deryaguin-Landau-Verwey-Overbeek (DLVO) theory, with a Hamaker constant of 6.7 × 10−20 J. These are the first measurements made using the Israelachvili surface forces apparatus without mica as a substrate material, and they demonstrate the possibility of using this technique to explore the surface chemistry of a wider range of materials.

Measuring surface forces to explore surface chemistry : mica, sapphire and silica

In this paper measurements of the forces acting between two solid surfaces separated by a thin liquid film are discussed. By investigating these forces in a range of different liquids and solutions, it is possible to acquire an understanding of the surface properties of the solid material. The surface of mica has been studied extensively in this way, and the results obtained are reviewed to illustrate how the surface force measurements can give surface chemical information. Recent measurements on two other materials, sapphire and silica, which are of greater practical interest are also discussed.

Analytic solution for the three-layer multiple beam interferometer

We present a simple analytic solution for the condition of constructive interference for light transmitted through an interferometer incorporating three ideally transparent layers of arbitrary thickness and refractive index. We also consider the effect of adding two metallic coatings to the outer surfaces of the interferometer and give empirical expressions for the associated phase changes for silver coatings on silica, sapphire, and mica substrates. A particular application to fringes of equal chromatic order can be utilized to obtain precise measurements of the thickness of extremely thin films sandwiched between two substrates.

Wetting behavior and evolution of microstructure of Sn-3.5Ag solder alloy on electroplated 304 stainless steel substrates

In the present study, wetting characteristics and evolution of microstructure of Sn–3.5Ag solder on Ag/Ni and Ni electroplated 304 stainless steel (304SS) substrates have been investigated. Solder alloy spread on Ag/Ni plated 304SS substrates exhibited better wetting as compared to Ni/304SS substrate. The formations of irregular shaped and coarser IMCs were found at the interface of solder/Ni/304SS substrate region whereas, solder/Ag/Ni/substrate interface showed continuous scallop and needle shaped IMCs. The precipitation of Ag3Sn, Ni–Sn, FeSn2 and lesser percentage of Fe–Cr–Sn IMCs were found at the interface of solder/Ag/Ni/substrate region whereas, solder/Ni/304 SS substrate exhibited predominantly FeSn2 and Fe–Cr–Sn IMCs. Presence of higher amount of Fe–Cr–Sn IMCs at the solder/Ni/304SS substrate interface inhibited the further wetting of solder alloy.

Facile synthesis of NiCo2O4 nanorod arrays on Cu conductive substrates as superior anode materials for high-rate Li-ion batteries

In this work, we report a mild and cost-effective solution method to directly grow Ni-substituted Co3O4 (ternary NiCo2O4) nanorod arrays on Cu substrates. Electrochemical impedance spectroscopy (EIS) measurements show that the values of the electrolyte resistance Re and charge-transfer resistance Rct of NiCo2O4 are 6.8 and 63.5 Ω, respectively, which are significantly lower than those of binary Co3O4 (10.4 and 122.4 Ω). This EIS characterization strongly confirms that the ternary NiCo2O4 anode has much higher electrical conductivity than that of the binary Co3O4 electrode materials, which should greatly enhance the lithium storage performances. Due to the well-aligned 1D nanorod microstructure and a higher electrical conductivity, these ternary NiCo2O4 nanorod arrays manifest high specific capacity, excellent cycling stability (a high reversible capacity of about 830 mA h g−1 was achieved after 30 cycles at 0.5 C) and high rate capability (787, 695, 512, 254, 127 mA h g−1 at 1 C, 2 C, 6 C 50 C and 110 C, respectively).