Dechlorination of Environmental Contaminants Using a Hybrid Nanocatalyst: Palladium Nanoparticles Supported on Hierarchical Carbon Nanostructures

This paper demonstrates the effectiveness of a new type of hybrid nanocatalyst material that combines the high surface area of nanoparticles and nanotubes with the structural robustness and ease of handling larger supports. The hybrid material is made by fabricating palladium nanoparticles on two types of carbon supports: as-received microcellular foam (Foam) and foam with carbon nanotubes anchored on the pore walls (CNT/Foam). Catalytic reductive dechlorination of carbon tetrachloride with these materials has been investigated using gas chromatography. It is seen that while both palladium-functionalized carbon supports are highly effective in the degradation of carbon tetrachloride, the rate of degradation is significantly increased with palladium on CNT/Foam. However, there is scope to increase this rate further if the wettability of these structures can be enhanced in the future. Microstructural and spectroscopic analyses of the fresh and used catalysts have been compared which indicates that there is no change in density or surface chemical states of the catalyst after prolonged use in dechlorination test. This implies that these materials can be used repeatedly and hence provide a simple, powerful, and cost-effective approach for dechlorination of water

Silver Nanoparticles Supported on Carbon Nanotube Carpets: Influence of Surface Functionalization

The effectiveness of nanoparticle-based functional devices depends strongly on the surface morphology and area of the support. An emerging powerful approach of increasing the available surface area without decreasing strength or increasing bulk is to attach arrays of suitable nanotubes on the surface, and to attach the necessary nanoparticles to them. Earlier publications by this team have shown that carpet-like arrays of carbon nanotubes (CNTs) can be successfully grown on a variety of larger carbon substrates such as graphite, foams and fabric, which offer hierarchical multiscale supporting architecture suitable for the attachment of silver nanoparticles (AgNPs). A limiting factor of pure CNT arrays in fluid-based applications is their hydrophobicity, which can reduce the percolation of an aqueous medium through individual nanotubes. Previous studies have demonstrated that the treatment of CNT carpets with dry (oxygen) plasma can induce reversible wettability, and treatment with wet (sol–gel) coating can impart permanent wettability. In this paper, we report the influence of such treatments on the attachment of AgNPs, and their effectiveness in water disinfection treatments. Both types of hydrophilic surface treatment show an increase in silver loading on the CNT carpets. Oxygen-plasma treated surfaces (O-CNT) show fine and densely packed AgNPs, whereas silica-coated nanotubes (silica-CNT) show uneven clusters of AgNPs. However, O-CNT surfaces lose their hydrophilicity during AgNP deposition, whereas silica-CNT surfaces remain hydrophilic. This difference significantly impacts the antibacterial effectiveness of these materials, as tested in simulated water containing Gram negative Escherichia coli (E. coli, JM109). AgNPs on silica-coated CNT substrates showed significantly higher reduction rates of E. coli compared to AgNPs on plasma-treated CNT substrates, despite the finer and better dispersed AgNP distribution in the latter. These results provide important insights into different aspects of surface modification approaches that can control the wettability of CNT carpets, and their applicability in water treatment applications

Evaluating Superconducting Ybco Film Properties Using Xray Photoelectron Spectroscopy

Initial results have been recently reported that suggest a potential correlation exists between the full-width-halfmaximum (FWHM) of the Y(3d) peak obtained by x-ray photoelectron spectroscopy (XPS) and the critical current density a YBa2Cu3O7-x film can carry. In particular, the Y(3d5/2) demonstrated a stronger correlation. Transport currents were determined by the 4-point contact method using the 1μV/cm criterion. An apparent correlation was also suggested between the Y(3d) FWHM and ac loss data points were acquired to further test the usefulness of the correlations. Samples were created by pulsed laser deposition of YBa2Cu3O7-x on LaAlO3 substrates

A Comparative Study of Three Different Chemical Vapor Deposition Techniques of Carbon Nanotube Growth on Diamond Films

This paper compares between the methods of growing carbon nanotubes (CNTs) on diamond substrates and evaluates the quality of the CNTs and the interfacial strength. One potential application for these materials is a heat sink/spreader for high-power electronic devices. The CNTs and diamond substrates have a significantly higher specific thermal conductivity than traditional heat sink/spreader materials making them good replacement candidates. Only limited research has been performed on these CNT/diamond structures and their suitability of different growth methods. This study investigates three potential chemical vapor deposition (CVD) techniques for growing CNTs on diamond: thermal CVD (T-CVD), microwave plasma-enhanced CVD (MPE-CVD), and floating catalyst thermal CVD (FCT-CVD). Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (TEM) were used to analyze the morphology and topology of the CNTs. Raman spectroscopy was used to assess the quality of the CNTs by determining the ID/IG peak intensity ratios. Additionally, the CNT/diamond samples were sonicated for qualitative comparisons of the durability of the CNT forests. T-CVD provided the largest diameter tubes, with catalysts residing mainly at the CNT/diamond interface. The MPE-CVD process yielded non uniform defective CNTs, and FCT-CVD resulted in the smallest diameter CNTs with catalyst particles imbedded throughout the length of the nanotubes

Key Attributes of Nanoscale Materials and Special Functionalities Emerging from Them

This chapter is from the book Nanoscale Multifunctional Materials: Science and Applications. This book consolidates various aspects of nanomaterials, highlighting their versatility as well as how the same materials can be used in seemingly diverse applications spanning across disciplines. It captures the multi-disciplinary and multi-functional aspects of nanomaterials in a holistic way. Chapters address the key attributes of nanoscale materials that make them special and desirable as novel materials; functionality that emerges based on these unique attributes; multiple uses of nanomaterials including combining properties and materials selection, and then separate chapters devoted to energy, biomedical materials, environmental applications, and chemical engineering applications

Nanoscale Multifunctional Materials: Science and Applications

This book consolidates various aspects of nanomaterials, highlighting their versatility as well as how the same materials can be used in seemingly diverse applications spanning across disciplines. It captures the multi-disciplinary and multi-functional aspects of nanomaterials in a holistic way. Chapters address the key attributes of nanoscale materials that make them special and desirable as novel materials; functionality that emerges based on these unique attributes; multiple uses of nanomaterials including combining properties and materials selection, and then separate chapters devoted to energy, biomedical materials, environmental applications, and chemical engineering applications.https://corescholar.libraries.wright.edu/books/1017/thumbnail.jp

Sample Preparation for Microscope and Spectroscopic Characterization of Solid Surfaces and Films

This chapter is from the book Sample Preparation Techniques in Analytical Chemistry. The synopsis of the book states the importance of accurate sample preparation techniques cannot be overstated--meticulous sample preparation is essential. Often overlooked, it is the midway point where the analytes from the sample matrix are transformed so they are suitable for analysis. Even the best analytical techniques cannot rectify problems generated by sloppy sample pretreatment. Devoted entirely to teaching and reinforcing these necessary pretreatment steps, Sample Preparation Techniques in Analytical Chemistry addresses diverse aspects of this important measurement step. These include: State-of-the-art extraction techniques for organic and inorganic analytes Sample preparation in biological measurements Sample pretreatment in microscopy Surface enhancement as a sample preparation tool in Raman and IR spectroscopy Sample concentration and clean-up methods Quality control steps Designed to serve as a text in an undergraduate or graduate level curriculum, Sample Preparation Techniques in Analytical Chemistry also provides an invaluable reference tool for analytical chemists in the chemical, biological, pharmaceutical, environmental, and materials sciences