Anna Luisa Costa

Pyrochlore phase and microstructure development in lead magnesium niobate materials

Abstract Microstructure characteristics of powder and sintered samples of lead magnesium niobate (PMN) have been compared and related to the presence or not of pyrochlore phase. Two kinds of samples obtained from two different batches of powders, batch A and B, containing 1 and 0 vol.% of pyrochlore phase respectively, were analysed. The two powders show the same morphology. The sintered samples, with pyrochlore content around 13 vol.% for samples from batch A and 0 vol.% for samples from batch B, exhibit totally different microstructures The grain size increases drastically from about 1 μm for samples with pyrochlore to 4–5 μm for pyrochlore free samples although starting from powders with same granulometry. The maximum dielectric constant of samples as fired, ground and annealed were measured and related to microstructures and amount of pyrochlore. On the basis of these results and data reported in literature, mostly relating dielectric properties to stoichiometry of the starting powder, it has been hypothesised that different sintering mechanisms come into play and govern the microstructure. Consequently the dielectric properties obtained were correlated to the sintering mechanism occurred rather than to the absolute value of pyrochlore phase present, as its commonly accepted.

Green and easily scalable microwave synthesis of noble metal nanosols (Au, Ag, Cu, Pd) usable as catalysts

A green synthesis process was developed for the production of PVP-coated noble metal nanoparticles in the form of stable nanosols. Water is the environmentally benign solvent; glucose serves as a mild, renewable and non-toxic reducing agent and microwave irradiation is an effective and fast heating technique. The same green process has been optimized to obtain several metal nanoparticles (Au, Ag, Cu, Pd), and therefore encourages the easy preparation of bimetallic nanostructures. Nanosols were characterized by dynamic light scattering DLS, HR-TEM, UV-Vis spectroscopy, XRD and ICP-AES. The total reaction yield for all the samples was assessed, the prepared nanoparticles were spherical shaped with an average diameter ranging from 3 to 20 nm. Nanosols with excellent stability over several months, achieved even for high solid contents, were prepared. Additionally, it is shown that all of the synthesized nanoparticles can act as effective catalysts for the reduction of 4-nitrophenol (4-NP) in the presence of NaBH4 (which is otherwise unfeasible without a metal catalyst). This reduction was spectrophotocally followed and the rate constants were determined by measuring the change in absorbance at 400 nm (the wavelength typical of 4-NP) as a function of time. The following ranking of decreasing efficiency of the catalyst was found: Pd > Au > Ag > Cu.

Organ burden and pulmonary toxicity of nano-sized copper (II) oxide particles after short-term inhalation exposure

Abstract Introduction: Increased use of nanomaterials has raised concerns about the potential for undesirable human health and environmental effects. Releases into the air may occur and, therefore, the inhalation route is of specific interest. Here we tested copper oxide nanoparticles (CuO NPs) after repeated inhalation as hazard data for this material and exposure route is currently lacking for risk assessment. Methods: Rats were exposed nose-only to a single exposure concentration and by varying the exposure time, different dose levels were obtained (C × T protocol). The dose is expressed as 6 h-concentration equivalents of 0, 0.6, 2.4, 3.3, 6.3, and 13.2 mg/m3 CuO NPs, with a primary particle size of 10 9.2–14 nm and an MMAD of 1.5 μm. Results: Twenty-four hours after a 5-d exposure, dose-dependent lung inflammation and cytotoxicity were observed. Histopathological examinations indicated alveolitis, bronchiolitis, vacuolation of the respiratory epithelium, and emphysema in the lung starting at 2.4 mg/m3. After a recovery period of 22 d, limited inflammation was still observed, but only at the highest dose of 13.2 mg/m3. The olfactory epithelium in the nose degenerated 24 h after exposure to 6.3 and 13.2 mg/m3, but this was restored after 22 d. No histopathological changes were detected in the brain, olfactory bulb, spleen, kidney and liver. Conclusion: A 5-d, 6-h/day exposure equivalent to an aerosol of agglomerated CuO NPs resulted in a dose-dependent toxicity in rats, which almost completely resolved during a 3-week post-exposure period.

Synthesis of nanostructured magnetic photocatalyst by colloidal approach and spray-drying technique.

Nanostructured particles with a magnetic core and a photocatalytic shell are very interesting systems for their properties to be magnetically separable (and so reusable) in photocatalytic water depuration implant. Here, a robust, low time-consuming, easily scale up method to produce Fe(3)O(4)/SiO(2)/TiO(2) hierarchical nanostructures starting from commercial precursors (i.e. Fe(3)O(4), SiO(2)) by employing a colloidal approach (i.e. heterocoagulation) coupled with the spray-drying technique is presented. In particular, a self-assembled layer-by-layer methodology based on the coagulation of dissimilar colloidal particles was applied. First, a passive layer of silica (SiO(2), amorphous) was created on magnetite in order to avoid detrimental phenomena arising from the direct contact between magnetite and titania, then the deposition of titania onto silica-coated-magnetite was promoted. TiO(2), SiO(2) and Fe(3)O(4) nanosols were characterized in terms of zeta potential, optimized and a self-assembled layer-by-layer approach was followed in order to promote the heterocoagulation of silica onto magnetite surface and of titania onto silica coated magnetite. Once optimized the colloidal route, the mixture was then spray-dried to obtain a granulated powder with nano-scale reactivity, easier to handle and re-disperse in comparison to starting nanopowders with the same surface properties. The nanostructured particles have been characterized by different techniques such as SEM, TEM, XDR and their magnetic properties have been investigated. Moreover, preliminary photocatalytic texts have been performed.

Impact and effectiveness of risk mitigation strategies on the insurability of nanomaterial production: evidences from industrial case studies

Workers involved in producing nanomaterials or using nanomaterials in manufacturing plants are likely to have earlier and higher exposure to manufactured/engineered nanomaterials (ENM) than the general population. This is because both the volume handled and the probability of the effluence of ‘free’ nanoparticles from the handled volume are much higher during a production process than at any other stage in the lifecycle of nanomaterials and nanotechnology‐enabled products. Risk assessment (RA) techniques using control banding (CB) as a framework for risk transfer represents a robust theory but further progress on implementing the model is required so that risk can be transferred to insurance companies. Following a review of RA in general and hazard measurement in particular, we subject a Structural Alert Scheme methodology to three industrial case studies using ZrO2, TiO2, and multi‐walled carbon nanotubes (MWCNT). The materials are tested in a pristine state and in a remediated (coated) state, and the respective emission and hazard rates are tested alongside the material performance as originally designed. To our knowledge, this is the first such implementation of a CB RA in conjunction with an ENM performance test and offers both manufacturers and underwriters an insight into future applications. WIREs Nanomed Nanobiotechnol 2015, 7:839–855. doi: 10.1002/wnan.1340 This article is categorized under: 1 Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine

Hollow-fiber flow field-flow fractionation and multi-angle light scattering investigation of the size, shape and metal-release of silver nanoparticles in aqueous medium for nano-risk assessment.

Due to the increased use of silver nanoparticles in industrial scale manufacturing, consumer products and nanomedicine reliable measurements of properties such as the size, shape and distribution of these nano particles in aqueous medium is critical. These properties indeed affect both functional properties and biological impacts especially in quantifying associated risks and identifying suitable risk-mediation strategies. The feasibility of on-line coupling of a fractionation technique such as hollow-fiber flow field flow fractionation (HF5) with a light scattering technique such as MALS (multi-angle light scattering) is investigated here for this purpose. Data obtained from such a fractionation technique and its combination thereof with MALS have been compared with those from more conventional but often complementary techniques e.g. transmission electron microscopy, dynamic light scattering, atomic absorption spectroscopy, and X-ray fluorescence. The combination of fractionation and multi angle light scattering techniques have been found to offer an ideal, hyphenated methodology for a simultaneous size-separation and characterization of silver nanoparticles. The hydrodynamic radii determined by fractionation techniques can be conveniently correlated to the mean average diameters determined by multi angle light scattering and reliable information on particle morphology in aqueous dispersion has been obtained. The ability to separate silver (Ag(+)) ions from silver nanoparticles (AgNPs) via membrane filtration during size analysis is an added advantage in obtaining quantitative insights to its risk potential. Most importantly, the methodology developed in this article can potentially be extended to similar characterization of metal-based nanoparticles when studying their functional effectiveness and hazard potential.

Shape-Related Toxicity of Titanium Dioxide Nanofibres

Titanium dioxide (TiO2) nanofibres are a novel fibrous nanomaterial with increasing applications in a variety of fields. While the biological effects of TiO2 nanoparticles have been extensively studied, the toxicological characterization of TiO2 nanofibres is far from being complete. In this study, we evaluated the toxicity of commercially available anatase TiO2 nanofibres using TiO2 nanoparticles (NP) and crocidolite asbestos as non-fibrous or fibrous benchmark materials. The evaluated endpoints were cell viability, haemolysis, macrophage activation, trans-epithelial electrical resistance (an indicator of the epithelial barrier competence), ROS production and oxidative stress as well as the morphology of exposed cells. The results showed that TiO2 nanofibres caused a cell-specific, dose-dependent decrease of cell viability, with larger effects on alveolar epithelial cells than on macrophages. The observed effects were comparable to those of crocidolite, while TiO2 NP did not decrease cell viability. TiO2 nanofibres were also found endowed with a marked haemolytic activity, at levels significantly higher than those observed with TiO2 nanoparticles or crocidolite. Moreover, TiO2 nanofibres and crocidolite, but not TiO2 nanoparticles, caused a significant decrease of the trans-epithelial electrical resistance of airway cell monolayers. SEM images demonstrated that the interaction with nanofibres and crocidolite caused cell shape perturbation with the longest fibres incompletely or not phagocytosed. The expression of several pro-inflammatory markers, such as NO production and the induction of Nos2 and Ptgs2, was significantly increased by TiO2 nanofibres, as well as by TiO2 nanoparticles and crocidolite. This study indicates that TiO2 nanofibres had significant toxic effects and, for most endpoints with the exception of pro-inflammatory changes, are more bio-active than TiO2 nanoparticles, showing the relevance of shape in determining the toxicity of nanomaterials. Given that several toxic effects of TiO2 nanofibres appear comparable to those observed with crocidolite, the possibility that they exert length dependent toxicity in vivo seems worthy of further investigation.

A Tractable Method for Measuring Nanomaterial Risk Using Bayesian Networks

While control banding has been identified as a suitable framework for the evaluation and the determination of potential human health risks associated with exposure to nanomaterials (NMs), the approach currently lacks any implementation that enjoys widespread support. Large inconsistencies in characterisation data, toxicological measurements and exposure scenarios make it difficult to map and compare the risk associated with NMs based on physicochemical data, concentration and exposure route. Here we demonstrate the use of Bayesian networks as a reliable tool for NM risk estimation. This tool is tractable, accessible and scalable. Most importantly, it captures a broad span of data types, from complete, high quality data sets through to data sets with missing data and/or values with a relatively high spread of probability distribution. The tool is able to learn iteratively in order to further refine forecasts as the quality of data available improves. We demonstrate how this risk measurement approach works on NMs with varying degrees of risk potential, namely, carbon nanotubes, silver and titanium dioxide. The results afford even non-experts an accurate picture of the occupational risk probabilities associated with these NMs and, in doing so, demonstrated how NM risk can be evaluated into a tractable, quantitative risk comparator.

TiO2 Nanosols Applied Directly on Textiles Using Different Purification Treatments

Self-cleaning applications using TiO2 coatings on various supporting media have been attracting increasing interest in recent years. This work discusses the issue of self-cleaning textile production on an industrial scale. A method for producing self-cleaning textiles starting from a commercial colloidal nanosuspension (nanosol) of TiO2 is described. Three different treatments were developed for purifying and neutralizing the commercial TiO2 nanosol: washing by ultrafiltration; purifying with an anion exchange resin; and neutralizing in an aqueous solution of ammonium bicarbonate. The different purified TiO2 nanosols were characterized in terms of particle size distribution (using dynamic light scattering), electrical conductivity, and ζ potential (using electrophoretic light scattering). The TiO2-coated textiles’ functional properties were judged on their photodegradation of rhodamine B (RhB), used as a stain model. The photocatalytic performance of the differently treated TiO2-coated textiles was compared, revealing the advantages of purification with an anion exchange resin. The study demonstrated the feasibility of applying commercial TiO2 nanosol directly on textile surfaces, overcoming problems of existing methods that limit the industrial scalability of the process.

Processing of a multilayer bender type actuator

Abstract A PZT material with high d 31 was developed and the processing of a bending type multilayer actuator by stacking and co-firing platinum electroded tape cast layers was investigated. The thermocompression step, as well as the binder burnout heating profile, proved to be critical and a tempering process was introduced that prevents the microcracks formation during densification. All the processing steps were optimized and prototype actuators made of 11 layers, each layer being 50 μm thick, were fabricated. The final microstructure was studied as well as the no-load deflection at increasing driving voltage.