Interactions and magnetization reversal of Ni nanowires arrays have been investigated by the first order reversal curve (FORC) method. Several series of samples with controlled spatial distribution were considered including simple wires of different lengths and diameters (70 nm and 110 nm) and complex wires with single modulated diameter along their length. Subtle features of magnetic interactions are revealed through a quantitative analysis of the local interaction field profile distributions obtained from FORC. In addition the FORC analysis indicates that the nanowire systems with a mean diameter of 70 nm appear to be organized in symmetric clusters indicative of a reversal-field memory effect.

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Nanomaterials are beginning to enter our daily lives through various consumer products as the result of technology commercialization. The development of methodologies to detect the presence of nanomaterials in consumer products is an essential element in understanding our exposure. In this study, we have developed methods for the separation and characterization of silicon dioxide (SiO2) and titanium dioxide (TiO2) nanostructures in dietary supplements marketed in products specifically targeted for women. A total of 12 commercial products claiming the inclusion of SiO2 and TiO2, but not making any claims regarding the particle size, were randomly selected for purchase through various retailers. To isolate nanostructures from these products, a simple methodology that combines acid digestion and centrifugation was utilized. Once isolated, the chemical composition, size, morphology, and crystal structure were characterized using mass spectroscopy, light scattering, electron microscopy, and X-ray diffraction techniques. SiO2 and TiO2 nanostructures were detected in 11 of 12 products using these methods. Many of the isolated nanoscale materials showed a high degree of aggregation; however, identified individual structures had at least one dimension below 100 nm. These robust methods can be used for routine monitoring of commercial products for nanoscale oxides of silica and titanium.

Titanium dioxide (TiO2) is commonly used as a color additive in food products. In this study, a total of 11 food products, such as a coffee cream, yogurt snack, hard candy, and chewy candy, that are widely consumed by adults or children were investigated. For characterization of particle size, size distribution, crystallinity, and concentration of TiO2, particles were first extracted using an acid digestion method from food, and various analytical techniques were applied. All products investigated in this study contained nanosized TiO2 particles (21.3–53.7%) in the anatase phase. The particle size of TiO2 was in the range of 26.9–463.2 nm. The concentration of TiO2 in the products ranged from 0.015% (150 ppm) to 0.462% (4620 ppm). These values obtained using inductively coupled plasma–mass spectrometry (ICP-MS) were considered as the reference and were compared with Raman results to evaluate the feasibility of using the Raman method to quantitate TiO2 in food products. The Raman method developed in this study proved to effectively analyze anatase TiO2 in food products at levels of several hundred parts per million or greater. Limitations of using the Raman method as a quick screening tool for determination of TiO2 are also discussed.

Coagulase-negative staphylococci (CoNS) are an important group of opportunistic pathogenic microorganisms that cause infections in hospital settings and are generally resistant to many antimicrobial agents. We report on phenotypic and genotypic virulence characteristics of a select group of clinical, mecA-positive (encoding penicillin-binding protein 2a) CoNS isolates. All CoNS were resistant to two or more antimicrobials with S. epidermidis strain 214EP, showing resistance to fifteen of the sixteen antimicrobial agents tested. Aminoglycoside-resistance genes were the ones most commonly detected. The presence of megaplasmids containing both horizontal gene transfer and antimicrobial resistance genetic determinants indicates that CoNS may disseminate antibiotic resistance to other bacteria. Staphylococcus sciuri species produced six virulence enzymes, including a DNase, gelatinase, lipase, phosphatase, and protease that are suspected to degrade tissues into nutrients for bacterial growth and contribute to the pathogenicity of CoNS. The PCR assay for the detection of biofilm-associated genes found the eno (encoding laminin-binding protein) gene in all isolates. Measurement of their biofilm-forming ability and Spearman’s rank correlation coefficient analyses revealed that the results of crystal violet (CV) and extracellular polymeric substances (EPS) assays were significantly correlated (ρ = 0.9153, P = 3.612e-12). The presence of virulence factors, biofilm-formation capability, extracellular enzymes, multidrug resistance, and gene transfer markers in mecA-positive CoNS clinical strains used in this study makes them powerful opportunistic pathogens. The study also warrants a careful evaluation of nosocomial infections caused by CoNS and may be useful in studying the mechanism of virulence and factors associated with their pathogenicity in vivo and developing effective strategies for mitigation.

A combination of mild and hard anodization processes have produced mild-hard AAO templates with selectively opened pores. Functional interpore distances were increased by as much as 3 times compared to conventional AAO templates. Magnetic nanowires with larger interpore distances show reduced wire-wire interactions in nanowire arrays.The sequential application of mild and hard anodization techniques in the fabrication of porous alumina membranes allows one to decrease the number of continuous pores in anodized aluminium oxide (AAO) templates. Initially, standard mild anodization techniques were used to create porous templates with 100 nm interpore distances and 70 nm pore diameters. Hard anodization treatment on the same membrane then produced interpore distances of about 265 nm with diameters of 110 nm. At the interface between the two anodization steps, many of the mild-side pores were terminated to create a mild-hard membrane (Mi-Ha AAO) where the functional interpore distances were 200-300 nm. Growth (electrodeposition) of nickel and cobalt nanowires in the various pore structures of the mild and hard sides of the Mi-Ha AAO templates allows one to probe magnetic interactions between nanowires and compares them to wires grown in standard mild templates (Mi-AAO). The magnetic properties of nanowires in Mi-Ha AAO and Mi-AAO showed distinct differences in the squareness of hysteresis loops and coercivity both as a function of pore structure and magnetic component. In general, the squareness of the hysteresis loops increased with aspect ratio and greater interpore distance. Coercivity also showed an increase with aspect ratio, but varied differently with interpore distance for Ni and Co. These various magnetic behaviors are discussed with respect to crystalline structure, morphology, and interactions of adjacent sets of nanowires.

This paper reports a rapid and straightforward method for the quantitation of total Ag content in nanobased commercially available liquid dietary supplements using a portable X-ray fluorescence (pXRF) analyzer. Figures of merits were evaluated by analyzing a series of AgNO3 standards. This method was shown to have a detection limit of 3 ppm, a quantitation limit of 10 ppm, and a broad linear range from the detection limit to 10000 ppm (1%). Accurate detection and quantitation of Ag content in well-characterized Ag nanoparticle samples and in nanobased liquid dietary supplements were achieved with good correlation (i.e., percentage difference average values under 15%) between the total Ag concentration obtained by the pXRF analyzer and by inductively coupled plasma mass spectrometry (ICP-MS). Furthermore, accurate quantitation of Ag in the presence of high concentrations of potential spectral interferences was also demonstrated.

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