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Graphical abstract Highlights • Flexible multifunctional nanoribbon arrays of palladium nanoparticles are prepared. • Sequential combination of laser nanostructuring and gas phase aggregation is used. • Interribon gap affects the optical transmittance and values above 80% can be reached. • The nanoribbon arrays are a system of anisotropic electrical resistance. • Reversible detection of hydrogen is observed down to a partial pressure of 60 ppm. Abstract A novel combination of nanostructuring techniques is undertaken to obtain a multifunctional material system consisting of planar arrays of nanoribbons of Pd nanoparticles (NPs) on polyethylene terephthalate (PET) substrates. The first stage was to prepare a laser-induced periodic surface structure (LIPSS) on the PET substrate, which electron microscopy revealed to be a large area, high coherence nanoripple pattern with spacing of (204 ± 1) nm and amplitude of (46 ± 9) nm. The second stage comprised NP (diameter 5 nm) deposition by orientating the nanostructured substrate to a Pd NP beam from a sputter gas phase aggregation source such that the substrate was partially shadowed by the ripple pattern (the incident angle with respect to the normal of the PET substrate was varied between 60 and 75°). This resulted in the formation of an array of NP ribbons (thickness ∼ 20 nm) on the ripple ridges, the mean ribbon width depending on the deposition incidence angle, thus confirming the shadowing effect. These planar arrays were studied as candidates for both flexible, transparent conductors and hydrogen sensors. Analysis of optical transmittance indicates that a mean inter-ribbon gap of above 100 nm is required in order to improve the average transmittance beyond 80%. Four-probe electrical resistance measurements show these nanoribbon arrays to be electrically anisotropic structures whose sheet resistance is understood to be governed by the contact resistance between NPs. An additional functionality is proven for the fabricated substrates: reversible detection of hydrogen at a partial pressure above ∼60 ppm, with good electrical sensitivity in the dilute (α-hydride) regime. [ABSTRACT FROM AUTHOR]

Purpose: To assess target coverage and dose homogeneity using conventional radiotherapy (RT) and intensity-modulated RT (IMRT) with anterior and posterior beams for elective irradiation of the cervical lymph nodes in patients with head and neck cancer.Materials and methods: A planning study was performed in six patients who had undergone radical RT for head and neck cancer. RT plans to irradiate the cervical lymph nodes using a single anterior field, or opposed anterior and posterior fields, with 6 or 10 MV photons were compared. Plans using IMRT for missing-tissue compensation were also studied. An algorithm was developed to guide clinicians to the most appropriate treatment technique depending on the nodal groups to be irradiated.Results: With 6 MV single field (SF) irradiation significant under-dose (minimum dose <70% of prescription dose) was seen in nodal groups II and V, due to their posterior position. With SF 10 MV the mean dose to level II was higher (p<0.001) and dose homogeneity to levels Ib and II was improved. Using opposed fields (OF), minimum doses to the nodes in levels II and V were improved. OF using 10 MV showed significant advantage over 6 MV with reduction of maximum doses to levels II, III and V. SF 10 MV IMRT improved maximum doses to levels Ib and II compared to SF 6 MV IMRT. OF IMRT gave the best dose distributions with optimal mean dose and dose homogeneity. Beam energy made no difference with OF IMRT.Conclusions: The optimal technique for elective cervical node irradiation depends on the lymph node levels within the PTV. If irradiation of the level II or V nodes is required, then the OF IMRT technique with either 6 or 10 MV gives the best dose distributions. In the absence of IMRT, then OF conventional techniques are best. If the aim is to irradiate levels III and IV or level IV only, then 6 MV SF non-IMRT is the simplest technique. [Copyright &y& Elsevier]

Nanostructured FeCo films comprising small (2.1 nm mean diameter) Co nanoparticles deposited into an Fe matrix are investigated by magnetometry, transmission electron microscopy and X-ray Magnetic Circular Dichroism (XMCD). Similar films were previously reported to possess a saturation magnetisation of up to 3 µ B /atom, thus exceeding the Slater-Pauling limit by a significant margin. The present work confirms the previous findings by magnetometry and demonstrates that the Co nanoparticles maintain their particulate identity within the film while adopting the crystallographic structure of the Fe matrix. The films show no evidence for voids or porosity (they exhibit the bulk density). An important factor in the high magnetisation in the films is an enhanced magnetic moment on the Co atoms, which XMCD indicates to be at least 2.21 µ B , i.e., 30 % larger than the bulk value for metallic cobalt. • Thin films of gas-phase Co clusters deposited into an Fe matrix were produced. • The magnetisation of the FeCo thin films is above the Slater-Pauling curve. • The bcc Co nanoparticles exhibit a magnetic moment 30 % higher than the bulk value. [ABSTRACT FROM AUTHOR]

Cloth used for facemask material has been coated with silver nanoparticles using an aerosol method that passes pure uncoated nanoparticles through the cloth and deposits them throughout the volume. The particles have been characterized by electron microscopy and have a typical diameter of 4 nm with the atomic structure of pure metallic silver presented as an assortment of single crystals and polycrystals. The particles adhere well to the cloth fibers, and the coating consists of individual nanoparticles at low deposition times, evolving to fully agglomerated assemblies in heavy coatings. The cloth was exposed to Usutu virus and murine norovirus particles in suspension and allowed to dry, following which, the infectious virus particles were rescued by soaking the cloth in culture media. It was found that up to 98% of the virus particles were neutralized by this contact with the silver nanoparticles for optimum deposition conditions. The best performance was obtained with agglomerated films and with polycrystalline nanoparticles. The work indicates that silver nanoparticles embedded in masks can neutralize the majority of virus particles that enter the mask and thus increase the opacity of masks to infectious viruses by up to a factor of 50. In addition, the majority of the virus particles released from the mask after use are non-infectious. [ABSTRACT FROM AUTHOR]

The advantages of gas-phase synthesis of nanoparticles in terms of size control and flexibility in choice of materials is well known. There is increasing interest in synthesizing multi-element nanoparticles in order to optimize their performance in specific applications, and here, the flexibility of material choice is a key advantage. Mixtures of almost any solid materials can be manufactured and in the case of core–shell particles, there is independent control over core size and shell thickness. This review presents different methods of producing multi-element nanoparticles, including the use of multiple targets, alloy targets and in-line deposition methods to coat pre-formed cores. It also discusses the factors that produce alloy, core–shell or Janus morphologies and what is possible or not to synthesize. Some applications of multi-element nanoparticles in medicine will be described. [ABSTRACT FROM AUTHOR]

Enhancement of mechanical properties in self‐assembled superstructures of magnetic nanoparticles is a new emerging aspect of their remarkable collective behavior. However, how magnetic interactions modulate mechanical properties is, to date, not fully understood. Through a comprehensive Monte Carlo investigation, this study demonstrates how the mechanical properties of self‐assembled magnetic nanocubes can be controlled intrinsically by the nanoparticle magnetocrystalline anisotropy (MA), as well as by the superstructure shape anisotropy, without any need for changes in structural design (i.e., nanoparticle size, shape, and packing arrangement). A low MA‐to‐dipolar energy ratio, as found in iron oxide and permalloy systems, favors isotropic mechanical superstructure stabilization, whereas a high ratio yields magnetically blocked nanoparticle macrospins which can give rise to metastable superferromagnetism, as expected in cobalt ferrite simple cubic supercrystals. Such full parallel alignment of the particle moments is shown to induce mechanical anisotropy, where the superior high‐strength axis can be remotely reconfigured by means of an applied magnetic field. The new concepts developed here pave the way for the experimental realization of smart magneto‐micromechanical systems (based, e.g., on the permanent super‐magnetostriction effect illustrated here) and inspire new design rules for applied functional materials. [ABSTRACT FROM AUTHOR]

Artificial materials from the self‐assembly of magnetic nanoparticles exhibit extraordinary collective properties; however, to date, the contribution of nanoscale magnetism to the mechanical properties of this class of materials is overlooked. Here, through a combination of Monte Carlo simulations and experimental magnetic measurements, this contribution is shown to be important in self‐assembled superstructures of magnetite nanocubes. By simulating the relaxation of interacting macrospins in the superstructure systems, the relationship between nanoscale magnetism, nanoparticle arrangement, superstructure size, and mechanical stability is established. For all considered systems, a significant enhancement in cohesive energy per nanocube (up to 45%), and thus in mechanical stability, is uncovered from the consideration of magnetism. Magnetic measurements fully support the simulations and confirm the strongly interacting character of the nanocube assembly. The studies also reveal a novel super‐size effect, whereby mechanically destabilization occurs through a decrease in cohesive energy per nanocube as the overall size (number of particles) of the system decreases. The discovery of this effect opens up new possibilities in size‐controlled tuning of superstructure properties, thus contributing to the design of next‐generation self‐assembled materials with simultaneous enhancement of magnetic and mechanical properties. [ABSTRACT FROM AUTHOR]

Electric, magnetic and resonance properties of La 0·7 Ba 0·3 MnO 3 /ZnO heterostructure fabricated on MgO (001) and LaAlO 3 (100) substrates by ion-beam sputtering have been studied in the work. Good crystallinity and phase purity of all heterostructure components have been confirmed using X-ray diffraction. Phase separated magnetic state of the manganite layer of heterostructure has been experimentally proved in the temperature region from 300 K down to 3 K. It has been shown that (La,Ba)MnO 3 /ZnO bilayer exhibits multi-step resistive switching as voltage exceeds a certain temperature-dependent threshold value. Detailed study of the resistive switching processes has been carried out at room temperature and in the low-temperature region. It is concluded that phase-separated state of manganites is responsible for strong temperature-induced transformation of the features of resistive switching phenomena. [ABSTRACT FROM AUTHOR]

Remanence magnetization plots (e.g., Henkel or δM plots) have been extensively used as a straightforward way to determine the presence and intensity of dipolar and exchange interactions in assemblies of magnetic nanoparticles or single domain grains. Their evaluation is particularly important in functional materials whose performance is strongly affected by the intensity of interparticle interactions, such as patterned recording media and nanostructured permanent magnets, as well as in applications such as hyperthermia and magnetic resonance imaging. Here, we demonstrate that δM plots may be misleading when the nanoparticles do not have a homogeneous internal magnetic configuration. Substantial dips in the δM plots of γ-Fe2O3 nanoparticles isolated by thick SiO2 shells indicate the presence of demagnetizing interactions, usually identified as dipolar interactions. Our results, however, demonstrate that it is the inhomogeneous spin structure of the nanoparticles, as most clearly evidenced by Mössbauer measurements, that has a pronounced effect on the δM plots, leading to features remarkably similar to those produced by dipolar interactions. X-ray diffraction results combined with magnetic characterization indicate that this inhomogeneity is due to the presence of surface structural (and spin) disorder. Monte Carlo simulations unambiguously corroborate the critical role of the internal magnetic structure in the δM plots. Our findings constitute a cautionary tale on the widespread use of remanence plots to assess interparticle interactions as well as offer new perspectives in the use of Henkel and δM plots to quantify the rather elusive inhomogeneous magnetization states in nanoparticles. [ABSTRACT FROM AUTHOR]

The exchange bias properties of 5 nm Co/CoO ferromagnetic/antiferromagnetic core/shell nanoparticles, highly dispersed in a CuxO matrix, have been optimized by matching the lattice parameter of the matrix with that of the CoO shell. Exchange bias and coercivity fields as large as HE = 7780 Oe and HC = 6950 Oe are linked to the presence of a Cu2O matrix (0.3% lattice mismatch with respect to the shells). The small mismatch between Cu2O and CoO plays a dual role: it (i) structurally stabilizes the CoO and (ii) favors the existence of a large amount of uncompensated moments in the shell that enhance the exchange bias effects. The results indicate that lattice matching may be a very efficient way to improve the exchange bias properties of core/shell nanoparticles, paving the way to novel approaches to tune their magnetic properties. [ABSTRACT FROM AUTHOR]

Porous films of cobalt nanoparticles have been obtained by sputter gas aggregation and controllably oxidized by air annealing at 100 °C for progressively longer times (up to more than 1400 h). The magnetic properties of the samples were monitored during the process, with a focus on the exchange bias field. Air annealing proves to be a convenient way to control the Co/CoO ratio in the samples, allowing the optimization of the exchange bias field to a value above 6 kOe at 5 K. The occurrence of the maximum in the exchange bias field is understood in terms of the density of CoO uncompensated spins and their degree of pinning, with the former reducing and the latter increasing upon the growth of a progressively thicker CoO shell. Vertical shifts exhibited in the magnetization loops are found to correlate qualitatively with the peak in the exchange bias field, while an increase in vertical shift observed for longer oxidation times may be explained by a growing fraction of almost completely oxidized particles. The presence of a hummingbird-like form in magnetization loops can be understood in terms of a combination of hard (biased) and soft (unbiased) components; however, the precise origin of the soft phase is as yet unresolved. [ABSTRACT FROM AUTHOR]

Microscopic structural instabilities of EuTiO3 single crystals were investigated by synchrotron x-ray diffraction. Antiferrodistortive (AFD) oxygen octahedron rotational order was observed alongside Ti derived antiferroelectric distortions. The competition between the two instabilities is reconciled through a cooperatively modulated structure allowing both to coexist. The combination of electric and magnetic fields increases the population of the modulated AFD order, illustrating how the origin of the large magnetoelectric coupling derives from the dynamic equilibrium between AFD and polar instabilities. [ABSTRACT FROM AUTHOR]

This work shows the possibility of tailoring the magnetic anisotropy direction in ferromagnetic LTP-MnBi thin films from out-of-plane to in-plane while also making possible for the first time the growth of quasi-hexagonal LTP-MnBi micro-islands. This has been managed with no need to apply any external magnetic field, but only by controlling the temperature growth. The rf sputtering of a Mn–Bi composite target produces highly crystalline <002> oriented micro-islands with a size distribution in the micrometer range (up to 80 μm) for samples grown at 300–425 K and <110> oriented elongated threads at 475 K. The <002> oriented films show perpendicular magnetic anisotropy while the <110> oriented ones show in-plane anisotropy. High values of coercivity have been obtained, reaching maximum values of 16.0 and 19.3 kOe at 300 and 400 K, respectively, for these LTP-MnBi thin films. Micromagnetic simulations have shown a clear correlation between the microstructure and the resulting magnetic properties. The route presented here represents a first step towards the possible fabrication of MnBi thin film micromagnets with customized magnetic anisotropy direction based on the deposition temperature. Image 1 • Magnetic anisotropy can be tuned in LTP-MnBi films from out-of-plane to in-plane. • No need to apply any external magnetic field to tune magnetic anisotropy. • Micromagnetic simulations correlate magnetic and morphological properties. • Quasi-hexagonal LTP-MnBi micro-islands are formed. • Coercivity increases from 16.0 to 19.3 kOe at 300 and 400 K, respectively. [ABSTRACT FROM AUTHOR]

The low temperature dynamic magnetic properties of two dense magnetic nanoparticle assemblies with similar superspin glass transition temperatures Tg~140 K are compared. The two samples are made from batches of 6 and 8 nm monodisperse γ-Fe2O3 nanoparticles, respectively. The properties of the individual particles are extracted from measurements on reference samples where the particles have been covered with a thick silica coating. The blocking temperatures of these dilute assemblies are found at 12.5 K for the 6 nm particles and at 35 K for the 8 nm particles, which implies different anisotropy energy barriers of the individual particles and vastly different temperature evolution of their relaxation times. The results of the measurements on the concentrated particle assemblies suggest a strong influence of the particle energy barrier on the details of the aging dynamics, memory behavior, and apparent superspin dimensionality of the particles. [ABSTRACT FROM AUTHOR]