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Magnetic nanoclusters have novel applications as magnetic sensors, spintronic and biomedical devices, as well as applications in more traditional materials such as high-density magnetic storage media and high performance permanent magnets. We describe a new synthesis protocol which combines the advantages of ion implantation and electron beam annealing (EBA) to produce surface iron nanoclusters. We compare the structure, composition and magnetic properties of iron nanoclusters fabricated by low dose 15 keV Fe implantation into SiO(2) followed by 1000 °C EBA or furnace annealing. Atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM) images together with superconducting quantum interference device (SQUID) magnetometry measurements show that only EBA leads to the rapid formation of surface crystalline Fe spherical nanoclusters, showing magnetic moments per Fe atom comparable to that of bulk bcc Fe and superparamagnetic properties. We propose a fabrication mechanism which includes e-beam enhanced desorption of SiO(2). This method has potential for fabricating nanoscale magnetic sensors integrated in microelectronic devices.

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The effect of sodium silicates on collagen structure during leather processing was investigated. Small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) reveal that the molecular structure and thermal stabilities of the sodium silicate treated leathers (So-Si and So-Si + BCS) were different to the conventionally processed chromium treated leathers (BCS). The collagen fibrils were observed to be coated by aggregates of silica, which did not affect the axial periodicity (D-period) of the collagen molecules. However, an increase in collagen fibril diameter was observed during the main tanning step when sodium silicates were used. This could be due to the swelling of collagen fibers from the high alkaline conditions of sodium silicates. From DSC studies, it was also found that sodium silicate treated samples impart no effect on collagen stabilization in the absence of chromium(III). However, a pseudostabilization effect is observed in the So-Si + BCS samples, possibly due to the inability of the collagen molecules to undergo conformational changes due to the silica coating on the collagen fibrils.The tanning of leather involves chemically intense processes leading to environmental pollution, resulting in a demand for cleaner but effective collagen stabilization mechanisms for the leather industry.1,2 Basic chromium(III) sulphate is the most common mineral tanning agent and, is preferred industrially because of the high hydrothermal stability. It has excellent properties in addition to relative short times required to produce nished leathers.3 However, poor uptake of chromium salts leads to high chemical and biological oxygen demand, and toxicity concerns relating to hexavalent chromium(VI) exposure, have led researchers to seek more environmentally friendly alternatives. 4-6Mineral tanning agents such as chromium, zirconium, aluminium, titanium and iron can all stabilize collagen and impart varying degrees of hydrothermal stability.3,7 Synthetic tanning agents (syntans) and vegetable tanning agents from plant polyphenols along with aldehydic cross-linkers are also commonly used, but typically in conjunction with mineral tannages.8 Combination tannages however, with or without mineral tanning agents, can overcome the issues that single tanning systems have with hydrothermal stability.9,10 For example, Vitolo and co-workers observed an increase in chromium uptake when sodium silicate was used in combination with basic chromium sulphate.11 Whilst pre-tans can improve the penetration and even distribution of the main tanning agents in the collagen matrix, a co-stabilizing agent can increase the efficiency of chrome uptake by reducing the amount of chrome required.8 With this idea of combining a weak and strong tanning agent, further studies have been carried out by investigating combinations of a number of tanning options and their effect on collagen stabilization. 4,6,9,12 Soluble silicates such as sodium silicate belong to a group of compounds that contain varying compositions of an alkali met...

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A large room temperature magnetoresistance ratio of up ∼40% at 8 T is observed in ion beam synthesized surface Fe nanoclusters on SiO2 where there is negligible hysteresis, and quasilinear behavior occurs for fields above 2 T. The negligible hysteresis can be attributed to the small dimensions of the Fe nanoparticles that are superparamagnetic with blocking temperatures ranging from 170 to 250 K. The large magnetoresistance is likely to be due to a combination of geometric and extraordinary magnetoresistances as well as spin-dependent scattering. The observed properties have great potential for magnetic sensing in the high field regime.

Low-energy platinum ions were implanted with 15 keV under normal incidence into synthesized conducting polymer films with the aim to improve film conductivity and to demonstrate the use of implanted platinum in a simple sensing design. Conductivity measurements, cyclic voltammetry, and Raman spectroscopy were performed on samples both before and following ion implantation. Results display an optimum fluence of ion implantation for which polypyrrole films implanted with 2 × 1016 at. cm–2 display and retain enhanced conductivity compared with nonimplanted samples. X-ray photoelectron spectroscopy (XPS) and scanning electron microscope–energy-dispersive X-ray spectroscopy (SEM-EDS) confirmed that implanted platinum is present mainly as Pt0 and indicated that the depth and amount of ion implantation are in agreement with a simulated implantation profile. Raman spectroscopy showed a surface-enhanced Raman spectroscopy (SERS) effect with platinum’s presence. The advantageous increase in conductivity can be rationalized by two chemical modifications to the polymer upon high-fluence implantation: (1) an increase in the number of charge carriers (dications) within the polymer and (2) the presence of elemental platinum metal and its synergistic effect on conductivity. A simple DNA sensor was constructed on the basis of polypyrrole/Pt0 films where Pt0 was able to serve as anchoring points for DNA attachment as well as an enhancer of the film’s conductivity. This enabled a DNA sensor capable of successful detection of cDNA, and a good discrimination of noncDNA, thus opening a way to direct electrochemical biosensing on the basis of ion implanted highly conducting polymer films.

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