James H. Johnston

Colored and Functional Silver Nanoparticle−Wool Fiber Composites

Silver nanoparticles utilizing the surface plasmon resonance effect of silver have been used to color merino wool fibers as well as imparting antimicrobial and antistatic properties to them to produce a novel silver nanoparticle-wool composite material. This is accomplished by the reduction of silver ions in solution by trisodium citrate (TSC) in the presence of merino wool fibers or fabrics. The silver metal nanoparticles simultaneously bind to the amino acids of the keratin protein in the wool fibers using TSC as the linker. The colors of the resulting merino wool-silver nanoparticle composites range from yellow/brown to red/brown and then to brown/black, because of the surface plasmon resonance effect of silver, and are tuned by controlling the reduction of silver ions to silver nanoparticles to give the required particle size on the fiber surface. In addition to the surface plasmon resonance optical effects, the silver nanoparticle-wool composites exhibit effective antimicrobial activity, thus inhibiting the growth of microbes and also an increase in the electrical conductivity, imparting antistatic properties to the fibers. Therefore, silver nanoparticles function as a simultaneous colorant and antimicrobial and antistatic agent for wool. Chemical and physical characterizations of the silver nanoparticle-merino wool composite materials have been carried out using scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, synchrotron radiation X-ray diffraction, atomic absorption spectroscopy, X-ray photoelectron spectroscopy, direct-current electrical conductivity measurements, wash-fast and rub-fast tests, and antimicrobial tests.

Carbothermal synthesis of titanium nitride

Studies of the reactivity of six TiO2 samples (two rutiles and four anatases) and nine carbon samples towards the formation of TiN by reduction of TiO2 with carbon in a nitrogen atmosphere at 1150°C show that the reaction is influenced by the chemical and physical properties of both the TiO2 and the carbon. Although anatases and rutiles behave similarly, their reactivities are adversely affected by the presence of impurities such as those deliberately added as surface coatings in pigment-grade TiO2. There is some evidence that the reactivity of the TiO2 increases with increasing surface area. Carbons with higher ash contents appear to be more reactive. The reactivity of the carbons generally increases with increasing surface area, as measured by gas penetration methods (BET nitrogen adsorption and Blaine gas permeation).

Novel hybrid materials of magnetic nanoparticles and cellulose fibers.

In this study, magnetic cellulose fibers have been prepared by coating bleached Kraft fibers (Pinus radiata) with magnetite nanoparticles. In doing so, the inherent properties of the fiber (such as tensile strength and flexibility) have been preserved, but imparted to it are the magnetic properties of the coating. The surface coating approach used differs from other methods in the literature in which the lumen loading or in situ approach is taken. After successive washings and sonication, the particles remained bonded to the surface of the fiber, and the fibers could be formed into a paper sheet. The chemical and physical characterization of these materials were carried out using scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and SQUID magnetometry. SEM shows the surface of the fibers to be completely encapsulated by the ferrite nanoparticles. This is also confirmed by EDS. XRD line broadening analysis shows the average particle sizes of the nanoparticles range from 12-26 nm. Magnetically responsive cellulose fibers such as those synthesized in this study, will allow the investigation of new concepts in papermaking and packaging, security paper, and information storage. Potential applications are in electromagnetic shielding, magnetographic printing and magnetic filtering.

Silver nanoparticle–clay composites

Composite materials of the alumino silicate minerals, kaolinite and halloysite, with silver nanoparticles have been successfully synthesised. This was achieved by a layer-by-layer deposition process in which kaolinite or halloysite was dispersed in successive solutions of the cationic polymeric linker polydiallyldimethylammonium chloride and anionic polymethacrylic acid capped silver nanoparticles. The optical properties of the metallic nanoparticles were retained in the composites and attractively coloured powders were produced. Electron microscopy revealed the silver to be nanospheres, ranging in diameter from 5–40 nm depending on the method of preparation. The chemical and physical characterisation of the resultant composites, particularly the mode of bonding between the nanoparticles and clays, was undertaken through X-ray diffraction, X-ray photoelectron spectroscopy and solid state NMR. The composites showed effective anti-microbial activity against Staphylococcus aureus bacteria.

A geochemical appraisal of oil seeps from the East Coast Basin, New Zealand

Abstract Oil seeps and stains from the East Coast Basin, New Zealand have been investigated using biomarker and stable carbon isotope analyses to determine oil-oil correlations. Oils sampled from the Raukumara Peninsula (northern East Coast Basin, North Island) and Marlborough (southern East Coast Basin, South Island) are derived from Late Cretaceous-Paleocene marine source rocks with a minor terrestrial content and are isotopically light. In contrast, oils sampled from Hawke’s Bay and Wairarapa (central and southern East Coast Basin, North Island) are derived from Paleocene marine source rocks, which contain high abundances of C30 regular steranes and 28,30-bisnorhopane, and are isotopically heavier than the other group. Biomarkers and bulk carbon isotopes show that there are at least two distinct sources of hydrocarbons in the basin.

Weathered spheroids in a Cretaceous/Tertiary boundary shale at Woodside Creek, New Zealand

Three types of spheroids are found in the iridium-rich shale layer at the Cretaceous/Tertiary boundary at Woodside Creek, South Island, New Zealand. Two of the types (A and B) consist mainly of microcrystalline goethite, whereas the third type (F) contains an appreciable quantity of hematite. There is a strong correlation between the iridium content of the spheroids and their matrices and the concentrations of other siderophiles such as chromium, cobalt, iron, and nickel. A similar pattern was observed for the chalcophiles arsenic, copper, and zinc. It is suggested that spheroids of types A and B are weathering products derived from diagenetic pyrite clumps and that type F, which contains hematite, represents a further stage in the weathering process and was derived from goethite. The original pyritic material could have readily scavenged arsenic and other siderophiles from the sea-water column under organic-rich reducing conditions at the end of the Cretaceous, and the siderophiles including iridium could have been incorporated into the original meteoritic material. It was concluded, therefore, that types A, B, and F spheroids are weathering products and do not represent original meteoritic material.

Nanogold and nanosilver composites with lignin-containing cellulose fibres

The formation of nanogold and nanosilver composites with cellulose paper fibres and the associated lignin component together with their antimicrobial properties are presented. This follows on from the proprietary technology of Johnston et al. [1] wherein they used nanogold and nanosilver entities in wool fibres to provide novel colourfast colourants in textiles with additional effective antimicrobial and catalytic properties. The nanogold and nanosilver are formed and bound directly onto the unbleached lignin-containing paper fibres without the use of an external linker molecule. For this, the lignin was found to play an essential role and hence the methodology presented is applicable only to cellulose in the form of unbleached kraft fibres and mechanical pulp. The phenol and possibly the aromatic methoxy groups of the lignin are considered to reduce Au3+ to Au0 and Ag+ to Ag0, respectively, and bind the nanogold and nanosilver to the fibre surface. SEM images and UV–Visible spectra confirm the formation of nanogold and nanosilver on the fibre surface. Changes in the IR spectra are consistent with the above role of the phenol and methoxy groups. The resulting nanogold—unbleached kraft fibres are purple and the nanosilver—unbleached kraft fibres are yellow due to the surface plasmon resonance effects of nanogold and nanosilver respectively. The nanogold—unbleached kraft fibres and particularly the nanosilver—unbleached kraft fibres exhibit very effective antimicrobial properties at low levels of gold and at very low levels of silver. In this way we have been able to produce novel nanogold paper and nanosilver paper fibres and products which collectively exhibit the properties of the nanomaterials and the fibre substrates in a synergistic way. This provides the opportunity for developing new functional paper products for antimicrobial packaging, medical dressings, and clothing.

Comparison of aromaticity and phenolic content as parameters for characterization of coal by 13C n.m.r. spectroscopy

Cross-polarization and magic-angle spinning techniques were used to obtain 13C n.m.r. spectra of 27 New Zealand coals sampled from drill cuttings at depths between 1.4 and 4.0 km in the Tara-1 oil exploration well, offshore south of New Zealand. Aromaticity and phenolic content were estimated from each spectrum. Of these two parameters, the phenolic content showed a stronger correlation with depth. The correlation was improved further by expressing the phenolic content as a fraction of the aromatic content. It was concluded that a combination of these parameters provides a new method for obtaining information about differences both in depositional environments and in the extent of subsequent coalification for suites of coal samples.

Calcium-phosphorus interactions at a nano-structured silicate surface.

Nano-structured calcium silicate (NCS), a highly porous material synthesized by controlled precipitation from geothermal fluids or sodium silicate solution, was developed as filler for use in paper manufacture. NCS has been shown to chemisorb orthophosphate from an aqueous solution probably obeying a Freundlich isotherm with high selectivity compared to other common environmental anions. Microanalysis of the products of chemisorption indicated there was significant change from the porous and nano-structured morphology of pristine NCS to fibrous and crystalline morphologies and non-porous detritus. X-ray diffraction analysis of the crystalline products showed it to be brushite, CaHPO42H2O, while the largely X-ray amorphous component was a mixture of calcium phosphates. A two-step mechanism was proposed for the chemisorption of phosphate from an aqueous solution by NCS. The first step, which was highly dependent on pH, was thought to be desorption of hydroxide ions from the NCS surface. This was kinetically favoured at lower initial pH, where the predominant form of phosphate present was H2PO(-)4, and led to decreased phosphorus uptake with increasing pH. The second step was thought to be a continuing chemisorption process after stabilization of the pH-value. The formation of brushite as the primary chemisorption product was found to be consistent with the proposed mechanism.

Towards the efficient utilization of geothermal resources

Abstract Separated geothermal water from production wells at Wairakei, Ohaaki, Kawerau, Ngawha and other less developed fields in New Zealand, contains potentially valuable chemical constituents. In particular, the extraction of precipitated amorphous silica is discussed in terms of its strategic and beneficial value to expanded energy generation in geothermal development, removal of environmentally sensitive constituents and as a marketable commodity in its own right. The prospect of recovering other minerals thereby realising the full potential of geothermal resources is considered. Expectations regarding high temperature reinjection could be reviewed in consideration of alternative opportunities which have been advanced in recent years.