Search

We demonstrate a polymer brush assisted approach for the fabrication of continuous zirconium oxide (ZrO2) films over large areas with high uniformity (pin-hole free) on copper (Cu) substrates. This approach involves the use of a thiol-terminated polymethyl methacrylate brush (PMMA-SH) as the template layer for the selective infiltration of zirconium oxynitrate (ZrN2O7). The preparation of a highly uniform covalently grafted polymer monolayer on the Cu substrate is the critical factor in fabricating a metal oxide film of uniform thickness across the surface. Infiltration is reliant on the chemical interactions between the polymer functional group and the metal precursor. A following reductive H2 plasma treatment process results in ZrO2 film formation whilst the surface Cu2O passive oxide layer was reduced to a Cu/Cu2O interface. Fundamental analysis of the infiltration process and the resulting ZrO2 film was determined by XPS, and GA-FTIR. Results derived from these techniques confirm the inclusion of the ZrN2O7 into the polymer films. Cross-sectional transmission electron microscopy and energy dispersive X-ray mapping analysis corroborate the formation of ZrO2 layer at Cu substrate. We believe that this quick and facile methodology to prepare ZrO2 films is potentially scalable to other high-κ dielectric materials of high interest in microelectronic applications.

Fabrication of ultrathin films of dielectric (with particular reference to materials with high dielectric constants) materials has significance in many advanced technological applications including hard protective coatings, sensors, and next-generation logic devices. Current state-of-the-art in microelectronics for fabricating these thin films is a combination of atomic layer deposition and photolithography. As feature size decreases and aspect ratios increase, conformality of the films becomes paramount. Here, we show a polymer brush template-assisted deposition of highly conformal, ultrathin (sub 5 nm) high-κ dielectric metal oxide films (hafnium oxide and zirconium oxide) on topographically patterned silicon nitride substrates. This technique, using hydroxyl terminated poly-4-vinyl pyridine (P4VP-OH) as the polymer brush, allows for conformal deposition with uniform thickness along the trenches and sidewalls of the substrate. Metal salts are infiltrated into the grafted monolayer polymer brush films via solution deposition. Tailoring specific polymer interfacial chemistries for ion infiltration combined with subsequent oxygen plasma treatment enabled the fabrication of high-quality sub 5 nm metal oxide films.

Atomic and molecular level interactions in solutions dictate the structural and functional attributes of crystals. These features clearly dictate the properties of materials and their applicability in technologies. However, the microscopic phenomena of particle formation—nucleation and growth—in real systems are still not fully understood. Specifically, crystallisation occurring in closed systems are largely unproven. Combining coherent experimental data, we here demonstrate a fundamental nucleation-growth mechanism that occurs in a model zinc oxide system when particles are formed under continuous, rapid heating under closed reaction conditions. Defying all previous reports, we show that the nucleation commences only when the heating is terminated. A prenucleation clusters pathway is observed for nucleation, followed by crystallite assembly-growth. We show that the nucleation-growth processes result from temporal and dynamic activity of constituent ions and gaseous molecules in solution and by the irreversible expulsion of the dissolved gaseous molecules. We suggest that this nucleation process is generic to most closed systems that go through precipitation, and, therefore, important for the crystallisation of a variety of metal oxides, composites and minerals. We anticipate that the work may be a platform for future experimental and theoretical investigation promoting deeper understanding of the nucleation-growth phenomena of a variety of practical systems.

The bottom-up colloidal synthesis of photonic band gap (PBG) materials or photonic crystals (PCs) has attracted considerable interest in comparison to top-down approaches due to the relatively simple processing steps involved, the potential for large area sample production and the relatively low-costs associated with this approach for the fabrication of complex 3-dimensional (3D) structures. This research focuses on the colloidal synthesis of poly(methyl methacrylate) (PMMA)@Au core–shell (CS) structures, their bottom-up assembly into 3D metallodielectric PCs (MDPCs) and the demonstration of their potential to be used as surface enhanced Raman substrates (SERS) using the commonly deployed SERS reporter molecule, 4- aminothiolphenol. Here, monodispersed spherical PMMA particles were used both as a host material for Au nanoparticles (NPs) and as a crystal template to produce the MDPC structures. The materials engineering employed which involved combining the synthesis of monodispersed CS particles and the fabrication of their corresponding MDPCs enabled us to control the distribution of Au NPs in the PC structure and thereby investigate their light scattering, reflection and transmission properties including Raman scattering.

Fresh and processed muscle-based foods are highly perishable food products and packaging plays a crucial role in providing containment so that the full effect of preservation can be achieved through the provision of shelf-life extension. Conventional packaging materials and systems have served the industry well, however, greater demands are being placed upon industrial packaging formats owing to the movement of muscle-based products to increasingly distant markets, as well as increased customer demands for longer product shelf-life and storage capability. Consequently, conventional packaging materials and systems will have to evolve to meet these challenges. This review presents some of the new strategies that have been developed by employing novel nanotechnological concepts which have demonstrated some promise in significantly extending the shelf-life of muscle-based foods by providing commercially-applicable, antimicrobially-active, smart packaging solutions. The primary focus of this paper is applied to subject aspects, such as; material chemistries employed, forming methods utilised, interactions of the packaging functionalities including nanomaterials employed with polymer substrates and how such materials ultimately affect microbes. In order that such materials become industrially feasible, it is important that safe, stable and commercially-viable packaging materials are shown to be producible and effective in order to gain public acceptance, legislative approval and industrial adoption.

TiSiC-Cr coatings, with Cr and Si as additional elements, were deposited on Si, C 45 and 316 L steel substrates via cathodic arc evaporation. Two series of coatings with thicknesses in the range of 3.6–3.9 μm were produced, using either CH 4 or C 2 H 2 as carbon containing gas. For each series, different coatings were prepared by varying the carbon rich gas flow rate between 90 and 130 sccm, while maintaining constant cathode currents (110 and 100 A at TiSi and Cr cathodes, respectively), substrate bias (–200 V) and substrate temperature (∼320 °C). The coatings were analyzed for their mechanical characteristics (hardness, adhesion) and tribological performance (friction, wear), along with their elemental and phase composition, chemical bonds, crystalline structure and cross-sectional morphology. The coatings were found to be formed with nano-scale composite structures consisting of carbide crystallites (grain size of 3.1–8.2 nm) and amorphous hydrogenated carbon. The experimental results showed significant differences between the two coating series, where the films formed from C 2 H 2 exhibited markedly superior characteristics in terms of microstructure, morphology, hardness, friction behaviour and wear resistance. For the coatings prepared using CH 4 , the measured values of crystallite size, hardness, friction coefficient and wear rate were in the ranges of 7.2–8.2 nm, 26–30 GPa, 0.3–0.4 and 2.1–4.8 × 10 −6 mm 3 N −1 m −1 , respectively, while for the coatings grown in C 2 H 2 , the values of these characteristics were found to be in the ranges of 3.1–3.7 nm, 41–45 GPa, 0.1–0.2 and 1.4–3.0 × 10 −6 mm 3 N −1 m −1 , respectively. Among the investigated coatings, the one produced using C 2 H 2 at the highest flow rate (130 sccm) exhibited the highest hardness (45.1 GPa), the lowest friction coefficient (0.10) and the best wear resistance (wear rate of 1.4 × 10 −6 mm 3 N −1 m −1 ).

Niobium oxide coatings deposited on Ti

Silver (Ag) nanoparticles (NPs) were synthesised and characterised, and their antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus cereus, Pseudomonas fluorescens and microflora derived from raw chicken, beef or cooked ham was determined. Polyvinyl chloride (PVC) films or antimicrobial Ag/PVC nanocomposite films were manufactured via a solvent casting method and the mechanical and thermal properties of these materials determined. Manufactured antimicrobial Ag/PVC nanocomposite films were used to wrap chicken breast fillets, followed by modified atmosphere packaging (using conventional laminates and employing a gas mix of 60 % N2/40 % CO2), and compared against PVC control films. In general, Gram-negative bacteria were more sensitive to Ag NPs than Gram-positive bacteria and microflora isolated from meat products were more resistant than pure culture bacteria. However, the most sensitive bacteria to Ag NPs were Pseudomonas fluorescens. No significant differences (p > 0.05) in tensile strength and elongation at break were observed, but glass transition temperatures (T g) of Ag/PVC nanocomposite films were lower (p

Recent developments in nanomaterials science and nanotechnology are advancing progress in every sphere of science, including medicine. In fact, nanotechnology is a promising field for new applications in medicine. New developments of technologies based on the manipulation of matter at the nanoscale have been applied to explain some of the physiological and pathological mechanisms of biological processes due to their improved features in the field of biodetection of pathogens and proteins, tissue engineering, separation of cells and molecules, studies of various DNA structures, fluorescent detection, implantable biosensors, medical implants, and drug delivery. In order to achieve these goals, multidisciplinary studies have been done by different research teams working on laboratory techniques, biochemistry, microbiology, pathology, electronics, and informatics for direct treatment or for (tele)monitoring of different therapies. The biocompatibility of new materials is an important aim for the researchers, as well as the potential antimicrobial action of the sample, in order to be used for medical applications.

Effective antimicrobial (AM) packaging strategies can significantly extend the shelf life of food allowing efficiency in the food supply chain and enhancing the sustainability of food production. Shelf life extending technologies have the greatest impact for high-value, high-end foods such as meat products since their production is resource intensive. AM food packaging, enabled by recent developments in nanotechnology, is a promising concept for addressing some of the key issues of sustainable food packaging. This chapter will describe recent developments in commercialized or commercialization-oriented research on AM active packaging concepts; in particular, we will focus on AM solutions centered on the surface engineering of packaging materials. In particular, we will discuss the pros and cons of surface engineering technology in food packaging based on our experience with a block copolymer-based surface modification strategy of polymer substrates and will further discuss about the costs, practicalities, risks, benefits, and safety challenges that may arise on the route to their commercialization process.

Niobium oxide coatings deposited on Ti6Al4V substrates by electron beam deposition and annealed in air at 600 °C and 800 °C were evaluated for their suitability towards dental, maxillofacial or orthopaedic implant applications. A detailed physico-chemical properties investigation was carried out in order to determine their elemental and phase composition, surface morphology and roughness, mechanical properties, wettability, and corrosion resistance in simulated body fluid solution (pH = 7.4) at room temperature. The biocompatibility of the bare Ti6Al4V substrate and coated surfaces was evaluated by testing the cellular adhesion and viability/proliferation of human osteosarcoma cells (MG-63) after 72 h of incubation. The coatings annealed at 800 °C exhibit more phase pure nanocrystalline Nb2O5 surfaces with enhanced wettability, reduced porosity and enhanced corrosion resistance properties making them good candidate for dental, maxillofacial or orthopaedic implant applications.

The hydroxyapatite enriched with Ti were prepared as possible candidates for biomedical applications especially for implantable devices that are in direct contact to the bone. The hydroxyapatites with different Ti content were prepared by RF magnetron sputtering on Ti-6Al-4V alloy using pure hydroxyapatite and TiO2 targets. The content of Ti was modified by changing the RF power fed on TiO2 target. The XPS and FTIR analyses revealed the presence of hydroxyapatite structure. The hardness and elastic modulus of the hydroxyapatite were increased by Ti addition. After 5 days of culture, the cell viability of the Ti-6Al-4V was enhanced by depositing with undoped or doped hydroxyapatite. The Ti additions led to an increase in cell viability of hydroxyapatite, after 5 days of culture. The electron microscopy showed the presence of more cells on the surface of Ti-enriched hydroxyapatite than those observed on the surface of the uncoated alloys or undoped hydroxyapatite. (C) 2016 Elsevier Ltd. All rights reserved.