Novel Hybrid Materials And Their Applications

<p>The development of novel hybrid materials of cellulose fibres and substrates with nanoparticles, conducting polymers and quantum dots, opens up novel application for new packaging materials and paper based products for the ‘smart packaging’ and ‘functional products’ areas that are emerging in the paper and packaging industries. Examples of these materials which have been developed here include cellulose fibres and substrates functionalised with magnetic nanoparticles, electrically conducting polypyrrole, and photoluminescent zinc sulfide quantum dots. Such materials were synthesised and then characterised using Alternating Gradient Magnetometry (AGM), Atomic Absorption Spectroscopy (AA), Cotec Profilometer Measurements, DC Conductivity Measurements, Photoluminescence Spectroscopy (PL), Scanning Electron Microscopy (SEM), SQUID Magnetometry, Transmission Electron Microscopy (TEM), Vibrational Sample Magnetometry (VSM), X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and X-ray Photoelectron Spectroscopy (XPS). Ferrimagnetic magnetite nanoparticles (particle size 12-26 nm) were synthesised by a simple aqueous precipitation method and had a magnetic saturation of approximately 60 emu g⁻¹, a coercive field of approximately 12-120 Oe, and a remnant magnetisation of approximately 11 emu g⁻¹. Magnetite coated Kraft fibres (1.2 – 3.15 wt. % Fe) were synthesised by adding a colloidal suspension of magnetite nanoparticles to a suspension of Kraft fibres. The fibres retained their inherent properties, such as tensile strength and flexibility, but inherited the magnetic properties of the magnetic nanoparticles. The nanoparticles remained unchanged on bonding - presumably through hydrogen bonding between the surface hydroxyl groups of the cellulose and the oxygen present in the magnetite. Newsprint, Kraft Board and Cotton fabric were coated with polypyrrole using a chemical polymerisation method. SEM shows a complete coating, whereby the fibres are completely encapsulated by the polymer, including individual fibrils. Again, bonding is facilitated through hydrogen bonding between the surface hydroxyl groups of the cellulose and the lone pairs of the nitrogen in the polypyrrole backbone. Samples were doped with p-toluenesulfonic acid to increase conductivity, of which up to 4 S cm⁻¹ was achieved. The samples were coated with magnetite nanoparticles using a starch binder, and tested for their application in EMI shielding. A maximum shielding effectiveness of 43 % in the 1-18 GHz range and 47 % in the 16-40 GHz range was obtained using cotton fabrics coated with both polypyrrole and magnetite. A synergistic effect is observed on using a polypyrrole and magnetite coating. Photoluminescent ZnS quantum dots, synthesised using an aqueous precipitation method, were doped with Mn²⁺ and Cu²⁺ to achieve emissions at approximately 600 nm (Mn²⁺) and 530 nm (Cu²⁺) on irradiation with UV light. The quantum dots had a particle size of approximately 2 nm, and were present in the zinc blende phase. Doped ZnS-coated Kraft fibres (5 – 30 wt. % Zn) were synthesised by a number of methods, the most successful being the ‘in-situ’ method, in which a uniform and complete coating was afforded. The fibres retained their inherent properties, such as tensile strength and flexibility, but inherited the photoluminescent properties of the ZnS quantum dots. The quantum dots remained unchanged on bonding - presumably through hydrogen bonding between the surface hydroxyl groups of the cellulose and the sulfur present in the ZnS quantum dots. ZnS quantum dots doped with Mn² and Cu²⁺ were successfully formulated for inkjet printing by capping with mercaptosuccinic acid. Upon irradiation with UV light, emissions at approximately 600 nm (Mn²⁺-doped) and 530 nm (Cu²⁺-doped) were observed. These were successfully inkjet printed in intricate patterns onto a number of substrates, including photographic quality inkjet paper, cotton, and wool.</p>

Novel Hybrid Materials And Their Applications

<p>The development of novel hybrid materials of cellulose fibres and substrates with nanoparticles, conducting polymers and quantum dots, opens up novel application for new packaging materials and paper based products for the ‘smart packaging’ and ‘functional products’ areas that are emerging in the paper and packaging industries. Examples of these materials which have been developed here include cellulose fibres and substrates functionalised with magnetic nanoparticles, electrically conducting polypyrrole, and photoluminescent zinc sulfide quantum dots. Such materials were synthesised and then characterised using Alternating Gradient Magnetometry (AGM), Atomic Absorption Spectroscopy (AA), Cotec Profilometer Measurements, DC Conductivity Measurements, Photoluminescence Spectroscopy (PL), Scanning Electron Microscopy (SEM), SQUID Magnetometry, Transmission Electron Microscopy (TEM), Vibrational Sample Magnetometry (VSM), X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and X-ray Photoelectron Spectroscopy (XPS). Ferrimagnetic magnetite nanoparticles (particle size 12-26 nm) were synthesised by a simple aqueous precipitation method and had a magnetic saturation of approximately 60 emu g⁻¹, a coercive field of approximately 12-120 Oe, and a remnant magnetisation of approximately 11 emu g⁻¹. Magnetite coated Kraft fibres (1.2 – 3.15 wt. % Fe) were synthesised by adding a colloidal suspension of magnetite nanoparticles to a suspension of Kraft fibres. The fibres retained their inherent properties, such as tensile strength and flexibility, but inherited the magnetic properties of the magnetic nanoparticles. The nanoparticles remained unchanged on bonding - presumably through hydrogen bonding between the surface hydroxyl groups of the cellulose and the oxygen present in the magnetite. Newsprint, Kraft Board and Cotton fabric were coated with polypyrrole using a chemical polymerisation method. SEM shows a complete coating, whereby the fibres are completely encapsulated by the polymer, including individual fibrils. Again, bonding is facilitated through hydrogen bonding between the surface hydroxyl groups of the cellulose and the lone pairs of the nitrogen in the polypyrrole backbone. Samples were doped with p-toluenesulfonic acid to increase conductivity, of which up to 4 S cm⁻¹ was achieved. The samples were coated with magnetite nanoparticles using a starch binder, and tested for their application in EMI shielding. A maximum shielding effectiveness of 43 % in the 1-18 GHz range and 47 % in the 16-40 GHz range was obtained using cotton fabrics coated with both polypyrrole and magnetite. A synergistic effect is observed on using a polypyrrole and magnetite coating. Photoluminescent ZnS quantum dots, synthesised using an aqueous precipitation method, were doped with Mn²⁺ and Cu²⁺ to achieve emissions at approximately 600 nm (Mn²⁺) and 530 nm (Cu²⁺) on irradiation with UV light. The quantum dots had a particle size of approximately 2 nm, and were present in the zinc blende phase. Doped ZnS-coated Kraft fibres (5 – 30 wt. % Zn) were synthesised by a number of methods, the most successful being the ‘in-situ’ method, in which a uniform and complete coating was afforded. The fibres retained their inherent properties, such as tensile strength and flexibility, but inherited the photoluminescent properties of the ZnS quantum dots. The quantum dots remained unchanged on bonding - presumably through hydrogen bonding between the surface hydroxyl groups of the cellulose and the sulfur present in the ZnS quantum dots. ZnS quantum dots doped with Mn² and Cu²⁺ were successfully formulated for inkjet printing by capping with mercaptosuccinic acid. Upon irradiation with UV light, emissions at approximately 600 nm (Mn²⁺-doped) and 530 nm (Cu²⁺-doped) were observed. These were successfully inkjet printed in intricate patterns onto a number of substrates, including photographic quality inkjet paper, cotton, and wool.</p>

Hydrophobicity and Charge Distribution Effects in the Formation of Bioorganoclays

Interactions of bioorganic moieties with clay minerals have attracted attention not only from the perspective of novel bioclay materials but also because they play a crucial role in our understanding of physical and chemical processes in soils. The aim of the present article is to explore the interactions responsible for the formation of a phosphatidylcholine-kaolinite bioclay by employing a series of classical molecular dynamic simulations. Detailed analysis of the structure and energies of the resulting bioclays reveals that the phosphatidylcholine molecules bind to the kaolinite surface either via their zwitterionic heads or hydrophobic aliphatic tails, depending on the kaolinite surface characteristics and the density of organic coating. The phosphatidylcholine molecules have a tendency to form irregular layers with a preferred parallel orientation of molecules with respect to the kaolinite surface. The tails exhibit varying degrees of flexibility and disorder depending on their distance from the surface and the density of surface coating. Significant differences in the binding can be spotted with respect to the two types of kaolinite basal surfaces, i.e., the hydrophobic siloxane surface, which possesses a considerable dispersion character, and the hydrophilic alumina surface, polarized by the surface hydroxyl groups.

A review of current knowledge and future trends in polymer/boehmite nanocomposites

Boehmite [bey-mahyt] is a unique aluminum oxide hydroxide nanostructure. It consists of nanosheets of octahedral aluminum ions with surface hydroxyl groups. Owing to exceptional reinforcing behavior, boehmite nanoparticles have gained immense attention as polymeric nanofillers. Essential matrices used with the boehmite based nanocomposites include poly(methyl methacrylate), polyethylene, polypropylene, polyamide, epoxy, and other polymers. In this review, all-inclusive considerations on the design, morphology, mechanical, thermal, electrical, ion conducting, flame retardancy, electrochemical, and other physical properties, and advances related to the polymer/boehmite nanocomposites are presented. The polymer/boehmite nanocomposites have been employed for the membranes (water filtration/dye removal), coatings (anti-corrosion/self-healing), Li-ion batteries, and non-flammability purposes.

Soft Tissue Interface with Various Kinds of Implant Abutment Materials

Various materials, such as titanium, zirconia and platinum-gold (Pt-Au) alloy, have been utilized for dental implant trans-mucosal parts. However, biological understanding of soft tissue reaction toward these materials is limited. The aim of this study was to compare the response of cell lines and soft tissue to titanium, zirconia and Pt-Au substrata. The surface hydroxyl groups and protein adsorption capacities of the substrata were measured. Next, gingival epithelial-like cells (Sa3) and fibroblastic cells (NIH3T3) were cultured on the materials, and initial cell attachment was measured. Immuno-fluorescent staining of cell adhesion molecules and cytoskeletal proteins was also performed. In the rat model, experimental implants constructed from various materials were inserted into the maxillary tooth extraction socket and the soft tissue was examined histologically and immunohistochemically. No significant differences among the materials were observed regarding the amount of surface hydroxyl groups and protein adsorption capacity. Significantly fewer cells of Sa3 and NIH3T3 adhered to the Pt-Au alloy compared to the other materials. The expression of cell adhesion molecules and a well-developed cytoskeleton was observed, both Sa3 and NIH3T3 on each material. In an animal model, soft tissue with supracrestal tissue attachment was observed around each material. Laminin-5 immuno-reactivity was seen in epithelia on both titanium and zirconia, but only in the bottom of epithelia on Pt-Au alloy. In conclusion, both titanium and zirconia, but not Pt-Au alloy, displayed excellent cell adhesion properties.