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This study presents the adsorption capability of a filter composed of sand coated with cobalt nanomaterials (CoNM) for the extraction of manganese ions from aqueous media. The study was performed in both batch and dynamic modes in order to evaluate the adsorption capabilities of free-standing CoNM and CoNM-coated sand. The Langmuir and Freundlich isotherm models were applied to the adsorption of manganese ions in batch-mode. The Langmuir model estimated a maximum adsorption capacity of 17.86 mg/g corresponding to a single layer adsorption. Nevertheless, the Freundlich model also characterized the adsorption with a high coefficient of determination, suggesting a multilayered adsorption mechanism of Mn on CoNM. Dynamic mode studies were conducted with different influent Mn concentrations, pH and in the presence of foreign or competing ions (Fe3+, As3+, As5+ and Cu2+). The experimental data was fitted with linearized Thomas and Yoon-Nelson models in order to determine adsorption capacities. The multilayered adsorption mechanism was confirmed owing to a high adsorption capacity of 3360 mg/g of active nanomaterials at pH = 6.

International audience; Light-emitting diodes (LED) are widely employed in display applications and lighting systems. Further research on LED that incorporates carbon nanostructures and metal nanoparticles exhibiting surface plasmon resonance has demonstrated a significant improvement in device performance. These devices offer lower turn-on voltages, higher external quantum efficiencies, and luminance. De facto, plasmonic nanoparticles, such as Au and Ag have boosted the luminance of red, green, and blue emissions. When combined with carbon nanostructures they additionally offer new possibilities towards lightweight and flexible devices with better thermal management. This review surveys the diverse possibilities to combine various inorganic, organic, and carbon nanostructures along with plasmonic nanoparticles. Such combinations would allow an enhancement in the overall properties of LED.

Heavy metal pollution of aquatic media has grown significantly over the past few decades. Therefore, a number of physical, chemical, biological, and electrochemical technologies are being employed to tackle this problem. However, they possess various inescapable shortcomings curbing their utilization at a commercial scale. In this regard, nanotechnology has provided efficient and cost-effective solutions for the extraction of heavy metals from water. This review will provide a detailed overview on the efficiency and applicability of various adsorbents, i.e., carbon nanotubes, graphene, silica, zero-valent iron, and magnetic nanoparticles for scavenging metallic ions. These nanoparticles exhibit potential to be used in extracting a variety of toxic metals. Recently, nanomaterial-assisted bioelectrochemical removal of heavy metals has also emerged. To that end, various nanoparticle-based electrodes are being developed, offering more efficient, cost-effective, ecofriendly, and sustainable options. In addition, the promising perspectives of nanomaterials in environmental applications are also discussed in this paper and potential directions for future works are suggested.

The last two decades have witnessed the development of new technologies for thin-film deposition and coating [...]

The present study investigates the synthesis of silver nanoparticles (Ag NP) using Artemisia vulgaris tincture and their enhanced antimicrobial activity against different bacterial strains. The Ag NP were characterized using UV-Vis spectroscopy, FTIR, and XRD. Their antibacterial activity was also assessed against Escherichia coli, Staphylococcus aureus, Streptococcus uberis, Pseudomonas aeruginosa, Listeria monocytogenes and Corynebacterium spp. The results demonstrated that the size of the inhibition zone increased with increase in Ag NP concentration. Additionally, the type of bacterial strain also had an effect on the size of the inhibition zones.

Core-shell Co@Co(OH)2 nanoparticles are characterised electrochemically with particular focus on the thin shell of cobalt (II) hydroxide which stabilises the metallic cobalt core against further oxidation in the presence of air. Voltammetric characterisation allows insights into the nature of the shell so both complementing and providing information unavailable using electron microscopy and X-ray diffraction. Moreover, the electrode reactions, occurring at particle ensembles, of the further oxidation of surface Co(OH)2 to CoOOH under alkaline conditions are further evidenced at the single particle level using electrochemical particle-electrode impacts (or ‘nano-impacts’). On this basis, the large extent of particle agglomeration/aggregation of Co@Co(OH)2 nanoparticles while suspended in the solutions is inferred.

Purpose Nanotechnology applied to cancer treatment is a growing area of research in nanomedicine with magnetic nanoparticle-mediated anti-cancer drug delivery systems offering least possible side effects. To that end, both structural and chemical properties of commercial cobalt metal nanoparticles were studied using label-free confocal Raman spectroscopy. Materials and Methods Crystal structure and morphology of cobalt nanoparticles were studied by XRD and TEM. Magnetic properties were studied with SQUID and PPMS. Confocal Raman microscopy has high spatial resolution and compositional sensitivity. It, therefore, serves as a label-free tool to trace nanoparticles within cells and investigate the interaction between coating-free cobalt metal nanoparticles and cancer cells. The toxicity of cobalt nanoparticles against human cells was assessed by MTT assay. Results Superparamagnetic Co metal nanoparticle uptake by MCF7 and HCT116 cancer cells and DPSC mesenchymal stem cells was investigated by confocal Raman microscopy. The Raman nanoparticle signature also allowed accurate detection of the nanoparticle within the cell without labelling. A rapid uptake of the cobalt nanoparticles followed by rapid apoptosis was observed. Their low cytotoxicity, assessed by means of MTT assay against human embryonic kidney (HEK) cells, makes them promising candidates for the development of targeted therapies. Moreover, under a laser irradiation of 20mW with a wavelength of 532nm, it is possible to bring about local heating leading to combustion of the cobalt metal nanoparticles within cells, whereupon opening new routes for cancer phototherapy. Conclusion Label-free confocal Raman spectroscopy enables accurately localizing the Co metal nanoparticles in cellular environments. The interaction between the surfactant-free cobalt metal nanoparticles and cancer cells was investigated. The facile endocytosis in cancer cells shows that these nanoparticles have potential in engendering their apoptosis. This preliminary study demonstrates the feasibility and relevance of cobalt nanomaterials for applications in nanomedicine such as phototherapy, hyperthermia or stem cell delivery.

We report on the controlled enhancement of the UV emission from ZnO nanoparticles synthesized via hydrothermal sol-gel routes. Various characterization techniques were used in this study to determine the crystal structure, defect formation, morphology and size of the ZnO nanoparticles. Firstly, the crystallinity of the ZnO nanoparticles was assessed by X-ray diffraction. The role of the precursor quantities on their morphology and bandgap states was investigated via transmission electron microscopy and photoluminescence spectroscopy, respectively. Subsequently, the impurity content and related bonds were evaluated by Fourier-transform infrared spectroscopy. In this work, the ZnO nanoparticles manifest a sharp UV emission along with a subdued green emission in the visible region. Conjoining ZnO with carbon nanotubes (CNT) suppressed the visible emission, as well as blueshifted and intensified the UV emission by ∼5-fold. These results suggest that CNT are effective in passivating the surface states of ZnO nanoparticles.

We report on the synthesis of free-standing ZnO nanoparticles (NPs) and ZnO NPs-decorated multiwalled carbon nanotubes (MWCNTs) via nonhydrolytic sol–gel (NHSG) routes. The role of the hydrates in the zinc precursor on the structure and surface termination of ZnO NPs via NHSG routes has already been reported in our earlier study. In the present work, the synthesis has been carried out in ambient air without using a glovebox, whereupon the effects of the synthesis temperature have been studied systematically. The structure, morphology, and optical properties of the free-standing ZnO-NPs are compared with those of the carbon nanotube-based nanocomposites, ZnO:MWCNTs, synthesized under identical conditions. The observed efficient and broad luminescence covering the entire visible spectrum points toward the high potential of the hybrid nanocomposites in optoelectronic and photovoltaic applications.

The simultaneous population explosion and the growing lack of clean water today requires disruptively innovative solutions in water remediation [...]

Cesium is a radioactive fission product generated in nuclear power plants and is disposed of as liquid waste. The recent catastrophe at the Fukushima Daiichi nuclear plant in Japan has increased the 137Cs and 134Cs concentrations in air, soil and water to lethal levels. 137Cs has a half-life of 30.4 years, while the half-life of 134Cs is around two years, therefore the formers’ detrimental effects linger for a longer period. In addition, cesium is easily transported through water bodies making water contamination an urgent issue to address. Presently, efficient water remediation methods towards the extraction of 137Cs are being studied. Prussian blue (PB) and its analogs have shown very high efficiencies in the capture of 137Cs+ ions. In addition, combining them with magnetic nanoparticles such as Fe3O4 allows their recovery via magnetic extraction once exhausted. Graphene and carbon nanotubes (CNT) are the new generation carbon allotropes that possess high specific surface areas. Moreover, the possibility to functionalize them with organic or inorganic materials opens new avenues in water treatment. The combination of PB-CNT/Graphene has shown enhanced 137Cs+ extraction and their possible applications as membranes can be envisaged. This review will survey these nanocomposites, their efficiency in 137Cs+ extraction, their possible toxicity, and prospects in large-scale water remediation and succinctly survey other new developments in 137Cs+ extraction.

International audience; We report on the photocurrent generation in HfO2-carbon nanotube (CNT) nanocomposites under Ultra-Violet (UV) and visible excitations at zero bias. Cubic phase HfO2 nanoparticles have been combined with multi-walled carbon nanotubes in this work. The cubic phase of HfO2 has been stabilized by oxygen vacancies which act as luminescent band gap states. In a broad UV-visible range of below band gap photoexcitation, a photocurrent is generated which was found to be most efficient under UV illumination. We discuss the possible mechanism in terms of a CNT assisted charge transfer involving optically active surface states of the HfO2 nanoparticles. The abrupt generation and relaxation responses of the photocurrent on/off cycles along with a constant steady state current as high as 200nA for 1mg of the nanocomposite, has potential in energy harvesting and other applications requiring stable charge retention.

Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency.

A hybrid material consisting of nonfunctionalized multiwall carbon nanotubes (MWCNTs) and cubic-phase HfO2 nanoparticles (NPs) with an average diameter of 2.6 nm has been synthesized. Free standing HfO2 NPs present unusual optical properties and a strong photoluminescence emission in the visible region, originating from surface defects. Transmission electron microscopy studies show that these NPs decorate the MWCNTs on topological defect sites. The electronic structure of the C K-edge in the nanocomposites was probed by electron energy loss spectroscopy, highlighting the key role of the MWCNT growth defects in anchoring HfO2 NPs. A combined optical emission and absorption spectroscopy approach illustrated that, in contrast to HfO2 NPs, the metallic MWCNTs do not emit light but instead expose their discrete electronic structure in the absorption spectra. The hybrid material manifests characteristic absorption features with a gradual merger of the MWCNT π-plasmon resonance band with the intrinsic defect band and fundamental edge of HfO2. The photoluminescence of the nanocomposites indicates features attributed to combined effects of charge desaturation of HfO2 surface states and charge transfer to the MWCNTs with an overall reduction of radiative recombination. Finally, photocurrent generation under UV–vis illumination suggests that a HfO2 NP/MWCNT hybrid system can be used as a flexible nanodevice for light harvesting applications.

ZnO-CNT hybrid materials were prepared by non-aqueous sol-gel routes at 240ºC. The morphology and defects have been studied by transmission electron microscopy and photoluminescence spectroscopy. The hybrid nanostructures manifest a broad luminescence emission covering the visible spectrum. Variations in photoluminescence with time are observed for the ZnO-CNT hybrid structures exposed to different ambient and temperatures. The studies show that photoluminescence from adsorbed oxygen dominates the emission emanating from other intrinsic defects and also affects the stability of the latter over time.

Photoluminescent ZnO carbon nanomaterials are an emerging class of nanomaterials with unique optical properties. They each, ZnO and carbon nanomaterials, have an advantage of being nontoxic and environmentally friendly. Their cost-effective production methods along with simple synthesis routes are also of interest. Moreover, ZnO presents photoluminescence emission in the UV and visible region depending on the synthesis routes, shape, size, deep level, and surface defects. When combined with carbon nanomaterials, modification of surface defects in ZnO allows tuning of these photoluminescence properties to produce, for example, white light. Moreover, efficient energy transfer from the ZnO to carbon nanostructures makes them suitable candidates not only in energy harvesting applications but also in biosensors, photodetectors, and low temperature thermal imaging. This work reviews the synthesis and photoluminescence properties of 3 carbon allotropes: carbon quantum or nanodots, graphene, and carbon nanotubes when hybridized with ZnO nanostructures. Various synthesis routes for the hybrid materials with different morphologies of ZnO are presented. Moreover, differences in photoluminescence emission when combining ZnO with each of the three different allotropes are analysed.

This work presents a method that enables the cheap production of surfactant-free stable metal nanoparticles in air. The silver nanoparticles are good candidates for new applications in green housing. Recently, we demonstrated usage of air-stable silver MNPs as biocidal coatings instead of chemical agents for protection of straw bales used in a green housing construction. Application of the silver nanoparticles as antifungal agents needs a method that does not neutralize their biocidal properties as a result of the testing method. In this study, we discuss the usual methods that are used for the antibacterial property testing and the development of a method that allows demonstrating the antifungal properties of metal nanoparticles.

We report on the one-pot synthesis and characterization of pure cubic and monoclinic phase HfO2 nanoparticles. An average particles size of 2.6 nm was estimated from transmission electron microscopy studies. The equivalent synthesis conditions of the two polymorphs provided means for direct comparison of their optical absorption and emission properties, which are found to exhibit different behaviors as functions of temperature and ambient. The origin of the strong visible luminescence observed from both cubic and monoclinic HfO2 is discussed in terms of surface-defects and nanosize of the particles. The comparative analysis of the PL responses of the two polymorphs suggests that emission at 3.1eV originates from the oxygen vacancy related defects.

Nanoparticles are mainly synthesized by chemical methods that usually involve toxic reactants as reducing agents that further produce toxic by-products, which in turn are hazardous to the environment. During the last decade, the development of eco-friendly alternative chemical methods based on microorganisms like bacteria or fungi, or more recently biological molecules extracted from plants, have spurred a lot of interest as it brings forward a solution to curb the production of toxic by-products. The purpose of these investigations is to combine the natural biocidal properties of nanoparticles with specific properties derived from plant extracts, not limited to anti-inflammatory or anti-cancer properties. The development of antibacterial/antifungal coatings based on nanoparticles exhibiting biocidal properties offers a method to overpower multi-drug resistant bacteria. Metal oxide nanoparticles (TiO2, ZnO, and MgO) and noble metal nanoparticles like Ag, Au, and Pt have shown efficient biocidal properties against microorganisms. However, these mechanisms are still not fully understood and moreover, depend on the type of nanoparticles. Antibacterial activity of metal oxide nanoparticles is mainly attributed to the production of reactive oxygen species whereas metal nanoparticles interact with surface membranes and are capable of infiltrating into bacteria whereupon they induce apoptosis. Here, the mechanism of preventing bacterial growth is different from conventional antibiotics and offers a promising alternative.

We report on the antibacterial and antifungal properties of silver nanoparticles in applications related to straw bale construction. Humidity related growth of microorganisms in green constructions is of concern as it can cause health problems among the house residents and reduce the durability of ecologically friendly construction materials. We provide a comparative analysis of the effects of silver nanoparticles on some of the most common house-colonizing fungi and bacteria. Outdoor tests demonstrate the efficiency of the silver nanoparticles for fighting micro-organisms. Indoor tests in petri dishes are compared with the outdoor tests, and the possible nature of the biocidal properties of the silver nanoparticles is probed. In contrast to the commonly reported results, we observe that antifungal properties of silver nanoparticles against common fungi in outdoor conditions show great potential in related applications.

We report on properties of nanocomposites composed of oxide nanoparticles (ZnO, CaHfO3 and SrHfO3) embedded in oxide rare earth (Eu2O3, Nd2O3) matrices deposited using atomic layer deposition. The embedment of nanoparticles in different oxide matrices allowed us for highlighting the role of surface defects via monitoring of the luminescence properties. We provide a comparative analysis of the photoluminescence (PL) of the bulk material, thin films, oxide nanoparticles and nanocomposites, and discuss the possible nature of the luminescent sites on the surfaces of the nanoparticles. The ZnO nanocomposites show distinguishable PL properties from those of the free-standing nanoparticles in terms of overall quantum efficiency and referring to intensity ratios of characteristic blue and green emission bands associated with radiative transitions that involve excitons and intrinsic defects, respectively. In contrast to the observed PL enhancement in the case of ZnO nanocomposites, the embedment of hafnia perovskites into oxide matrix is found to suppress the luminescence efficiency

Silver nanoparticles synthesized through plant-mediated synthesis have recently gained recognition in the field of biocidal coatings. However, the accurate control of the synthesis using plant extract appears difficult and tends to produce a silver chloride secondary phase. In this study, 2 different methods of synthesis using the same plant extract of Plantago major have been investigated to evaluate their influence on the production of AgCl. In both cases the silver nanoparticles have demonstrated efficient biocidal properties against micro-organisms.

Curing processes enabling transformation of liquid threads into solid material have gained technological importance. Our study is focusing on the comparison of curing mechanisms for metal alkoxide-derived liquid threads. We studied the mechanisms of the formation of fine metal oxide fibers or hollow microtubes by comparing the solidification of propoxide and butoxide precursors.

International audience; In this work, we present two types of hybrid materials. The first hybrid material is a combination of carbon nanotubes (CNT) with HfO2 nanoparticles. The latter constituent on its own exhibits unusual visible photoluminescence, which is in stark contrast to non-luminescent HfO2 in the bulk form. The small size of HfO2 nanoparticles, 2.6 nm in average, suggests surface-defect related origin of the observed photoluminescence. The other hybrid material is CNT-ZnO with the embedded ZnO nanoparticles ranging from 50nm to 100nm in size. ZnO represents a direct bandgap semiconductor renowned as highly-luminescent in a broad spectral range. The visible region is attributed to luminescence involving deep-level defects, and hence depends on the synthesis conditions. In this study we compare the morphology of the two hybrid materials with transmission electron microscopy. We further compare the photoluminescence properties and the influence of the CNT coupling on enhancing or suppressing defect related emissions. Finally, we present a novel hybrid material CNT-HfO2 capable of producing a photocurrent under zero bias.

In this work we show that atomic layer deposition (ALD) stands out as a very promising method for coating nanomaterials and, more specifically, nanoporous materials of technological interest in heterogeneous catalysis. ALD is capable of coating extremely complex shapes with high conformality and high aspect ratios. The current work describes deposition of ZnO and CoO thin films on γ-alumina nanoporous particles with sizes ranging from 20 to 100 µm in diameter, as well on aluminum membrane discs (anodiscs), and converting the surfaces into nanoporous, mechanically more robust spinel phases. We maintain the porosity of the supporting γ-alumina particle, despite the addition of material to the 16 nm pores, by utilizing subsequent reactions between the coated layer and γ-alumina, following the Kirkendall mechanism. The oxide thin film coatings are deposited at 175 and 167°C for ZnO and cobalt oxide, respectively, and thereafter annealed at from 600 to 1000°C for 3 h. This represents a new way to produce highly porous spinel particles and spinel-coated membrane discs.

The deposition of a thin magnesium metallic interlayer on an Si substrate prior to the deposition of an oxide thin film using rf-sputtering was investigated. The deposition of high-κ HfO 2 thin film was more particularly studied and it was demonstrated that the metallic interlayer acts as an oxygen barrier, preventing the formation of a low-κ layer at the high-κ/Si interface during the deposition. A post-deposition annealing treatment performed on the films induced the diffusion of the metal barrier into the HfO 2 film and allowed obtaining a sharp interface. However, the degree of diffusion depends not only on the interlayer thickness, but also on the thickness of the high-κ film. X-ray photoelectron spectroscopy was used to study the degree of oxidation of the Mg interlayer. High resolution transmission electron microscopy and energy filtered transmission electron microscopy were used to characterize the films and the diffusion of the Mg interlayer into the high-κ film after annealing. In this work we will stress on the engineering of the interface via the diffusion of the Mg interlayer during the growth process and on annealing.

We report on properties of ZnO nanoparticles synthesized via non-aqueous sol–gel routes. The role of the hydrates in the zinc precursor (Zn(acac)2, xH2O) on the structure and surface termination during the synthesis is studied for the first time. The structural and chemical properties of the ZnO nanoparticles were studied by standard structural and optical characterization methods. A broad luminescence was observed from the nanoparticles stretching throughout the visible region of the spectrum and comprising characteristic blue and green emission bands commonly associated with intrinsic defects in ZnO. A tentative model is proposed to explain differences in the luminescence of nanoparticles synthesized using different routes by taking into account the role of oxygen vacancies and other native defects: most likely being zinc vacancies and interstitials, located near the surface of the nanoparticles.

This article reports on optical properties of SrHfO3 and CaHfO3 nanoparticles with sizes as small as 1.6 nm, synthesized via non aqueous sol–gel routs for the first time. An unexpectedly strong luminescence from the undoped nanoparticles was observed in the visible spectrum over a wide temperature range, also exhibiting sensitivity to temperature variation and surrounding ambient (vacuum/air) and exposure time to UV light. A tentative model is proposed to explain these phenomena in terms of luminescent centers located at the surface of the nanoparticles.

The binary Zn4Sb3 phase is a promising material for thermoelectric applications due to its extraordinarily low thermal conductivity. The present study attempts to rationalize this property by investigating its nanostructure. β-Zn4Sb3 samples with varying Zn content were thus synthesized, quenched from the melt and annealed at 350 °C. Their nanostructure was observed using transmission electron microscopy. The samples presented in this work have Zn:Sb atomic ratios of 1.30 and 1.33 and exhibit a single phase of β-Zn4Sb3 in X-ray diffraction studies. Transmission electron microscopy (TEM) observations revealed nanoporous morphologies for both compositions, with a random distribution of the voids. Both samples contain voids, while the sample with Zn:Sb = 1.33 also consists of Zn nanoinclusions. Density functional theory calculations were carried out to study the stability of atomistic β-Zn4Sb3 models with varying Zn content. This was used to suggest a mechanism for the formation of Zn nanoparticles and subsequently nanovoids. The calculations imply that the Zn solubility in the Zn4Sb3 matrix increases with decreasing temperature. Combined with a high Zn diffusivity, this work explains how Zn could leave the nanoprecipitates during annealing, resulting in the voids seen by TEM.

The effect of a thin metallic interlayer deposited on Si substrate prior the sputtering of HfO2 films was investigated. It was shown that the metallic interlayer acts as an oxygen barrier during the HfO2 deposition. After annealing, the metal diffuses in HfO2 films and prevents the formation of a low-k layer at the high-k/Si interface. However, in order to fully investigate the improvement in the interfacial and electrical properties, the thickness of the metallic interlayer needs to adapted to the thickness of the HfO2.

The control of high-symmetry phases of HfO2 can be achieved by cationic substitution for Hf. The electrical properties of the cubic HfO2 phase stabilized by addition of yttrium or magnesium were investigated. The introduction of moderate Y or Mg doping content (~10-15%) in HfO2 results in an enhancement of the dielectric constant. No degradation of the interface state density and of the leakage current was noticed. The flat-band voltage is shifted to positive voltages, similarly as it was observed for monoclinic and cubic pure HfO2 thin films. This result confirms that the contribution of the SiO2/high-k interface to the flat-band voltage depends on the structural interface properties.

The flat-band voltage shift of bilayer SiO2/HfO2 MOS structures is investigated as a function of the structural properties of the HfO2 films. It was demonstrated that for amorphous HfO2 films, the flat-band voltage vs HfO2 thickness relationship is well described by a second-order polynomial resulting from a bilayer model including two interfacial charge densities and bulk high-k charges. When the crystalline structure of HfO2 is stabilized in a monoclinic phase, the flat-band voltage is shifted to positive voltages and becomes nearly independent on the HfO2 thickness. These results confirm that the high-k/SiO2 interface can significantly contribute to the flat-band voltage shift. However, this contribution appears greatly dependent on the microstructural properties of HfO2.

Double perovskites provide a unique opportunity to induce and control multiferroic behaviors in oxide systems. The appealing possibility to design materials with a strong coupling between the magnetization and the polarization fields may be achieved in this family since these magnetic insulators can present structural self-ordering in the appropriate growth conditions. We have studied the functional properties of La2CoMnO6 and Bi2CoMnO6 epitaxial thin films grown by pulsed laser deposition. Cation-ordered La2CoMnO6 films display a magnetic Curie temperature of 250 K while cation-disordered Bi2CoMnO6 films present ferromagnetism up to ~ 800 K. Such high transition temperature for magnetic ordering can be further tuned by varying the strain in the films indicating an important contribution from the structural characteristics of the materials. Our approach might be generalized for other oxide systems. At this end, our results are compared with other multiferroic systems. The roles of various cations, their arrangements and structural effects are further discussed., 12 pages, 5 figs