Aquatic Fate and Ecotoxicology Effect of ZnS:Mn Quantum Dots on Chlorella vulgaris in Fresh Water.

With the increasing integration of nanomaterials into daily life, the potential ecotoxicological impacts of nanoparticles (NPs) have attracted increased attention from the scientific community. This study assessed the ecotoxicity of ZnS quantum dots (QDs) doped with varying molar concentrations of Mn2+ on Chlorella vulgaris. The ZnS:Mn QDs were synthesized using the polyol method. The size of the ZnS:Mn QDs ranged from approximately 1.1 nm to 2 nm, while the aggregation size in Seine River water was 341 nm at pH 6 and 8. The presence of ZnS:Mn (10%) NPs exhibited profound toxicity to Chlorella vulgaris, with immediate reductions in viability (survival cells) from 71%, 60% to 51%, 52% in BG11 and Seine River water, respectively, at a concentration of 100 mg L-1 of ZnS:Mn (10%) NPs. Additionally, the ATP content in Chlorella vulgaris significantly decreased in Seine River water (by 20%) after 3 h of exposure to ZnS:Mn (10%) NPs. Concurrently, SOD activity significantly increased in Seine River water, indicating that the ZnS:Mn (10%) NPs induced ROS production and triggered an oxidative stress response in microalgae cells.

Gold and Iron Oxide Nanoparticle Assemblies on Turnip Yellow Mosaic Virus for In-Solution Photothermal Experiments.

The ability to construct three-dimensional architectures via nanoscale engineering is important for emerging applications in sensors, catalysis, controlled drug delivery, microelectronics, and medical diagnostics nanotechnologies. Because of their well-defined and highly organized symmetric structures, viral plant capsids provide a 3D scaffold for the precise placement of functional inorganic particles yielding advanced hierarchical hybrid nanomaterials. In this study, we used turnip yellow mosaic virus (TYMV), grafting gold nanoparticles (AuNP) or iron oxide nanoparticles (IONP) onto its outer surface. It is the first time that such an assembly was obtained with IONP. After purification, the resulting nano-biohybrids were characterized by different technics (dynamic light scattering, transmission electron microcopy, X-ray photoelectron spectroscopy…), showing the robustness of the architectures and their colloidal stability in water. In-solution photothermal experiments were then successfully conducted on TYMV-AuNP and TYMV-IONP, the related nano-biohybrids, evidencing a net enhancement of the heating capability of these systems compared to their free NP counterparts. These results suggest that these virus-based materials could be used as photothermal therapeutic agents.

Unusual, hierarchically structured composite of sugarcane pulp bagasse biochar loaded with Cu/Ni bimetallic nanoparticles for dye removal.

Biochar-supported nanocatalysts emerged as unique materials for environmental remediation. Herein, sugarcane pulp bagasse (SCPB) was wet-impregnated with Cu(NO3)23H2O and Ni(NO3)26H2O, then pyrolyzed at 500 °C, under N2, for 1 h. We specifically focused on sugarcane pulp instead of SCB and biochar materials. The metal nitrate to biomass ratio was set at 0.5, 1, and 2 mmol/g, with Cu/Ni initial ratio = 1. The process provided hierarchically structured porous biochar, topped with evenly dispersed 40 nm-sized CuNi alloy nanoparticles (SCPBB@CuNi). The biochar exhibited an unusual fishing net-like structure induced by nickel, with slits having a length in the 3-12 µm range. Such a fishing net-like porous structure was obtained without any harsh acidic or basic treatment of the biomass. It was induced, during pyrolysis, by the nanocatalysts or their precursors. The CuNi nanoparticles form true alloy as proved by XRD, and are prone to agglomeration at high initial metal nitrate concentration (2 mmol/g). Stepwise metal loading was probed by XPS versus the initial metal nitrate concentration. This is also reflected in the thermal gravimetric analyses. The SCPBB@CuNi/H2O2 (catalyst dose: 0.25 g/L) system served for the catalyzed removal of Malachite Green (MG), Methylene Blue (MB), and Methyl Orange (MO) dyes (concentration = 0.01 mmol/L). Both single and mixed dye solutions were treated in this advanced oxidation process (AOP). The dyes were removed in less than 30 min for MG and 3 h for MB, respectively, but 8 h for MO, therefore showing selectivity for the degradation of MG, under optimized degradation conditions. The catalysts could be collected with a magnet and reused three times, without any significant loss of activity (∼85%). AOP conditions did not induce any nanocatalyst leaching. To sum up, we provide a simple wet impregnation route that permitted to design highly active Fenton-like biochar@CuNi composite catalyst for the degradation of organic pollutants, under daylight conditions.

Interaction between carbon dots from folic acid and their cellular receptor: a qualitative physicochemical approach.

According to the World Health Organization, the number of cancers (all cancers, both sexes, all ages and worldwide) in 2020 reached a total of 19 292 789 new cases leading to 9 958 133 deaths during the same period. Many cancers could be cured if detected early. Preventing cancer and detecting it early are two essential strategies for controlling this pathology. For this purpose, several strategies have been described for imaging cancer cells. One of them is based on the use of carbon nanoparticles called carbon dots, tools of physical chemistry. The literature describes that cancer cells can be imaged using carbon dots obtained from folic acid and that the in cellulo observed photoluminescence probably results from the interaction of these nanoparticles with the folic acid-receptor, a cell surface protein overexpressed in many malignant cells. However, this interaction has never been directly demonstrated yet. We investigated it, for the first time, using (i) freshly synthesized and fully characterized carbon dots, (ii) folate binding protein, a folic acid-receptor model protein and (iii) fluorescence spectroscopy and isothermal titration calorimetry, two powerful methods for detecting molecular interactions. Our results even highlight a selective interaction between these carbon made nano-objects and their biological target.

Functionalized maghemite nanoparticles for enhanced adsorption of uranium from simulated wastewater and magnetic harvesting.

Maghemite (γ-Fe2O3) nanoparticles (MNPs) were functionalized with 3-aminopropyltriethoxysilane (APTES) to give APTES@Fe2O3 (AMNP) which was then reacted with diethylenetriamine-pentaacetic acid (DTPA) to give a nanohybrid DTPA-APTES@Fe2O3 (DAMNP). Nano-isothermal titration calorimetry shows that DTPA complexation with uranyl ions in water is exothermic and has a stoichiometry of two DTPA to three uranyl ions. Density functional theory calculations indicate the possibility of several complexes between DTPA and UO22+ with different stoichiometries. Interactions between uranyl ions and DAMNP functional groups are revealed by X-photoelectron and Fourier transform infrared spectroscopies. Spherical aberration-corrected Scanning Transmission Electron Microscopy visualizes uranium on the particle surface. Adsorbent performance metrics were evaluated by batch adsorption studies under different conditions of pH, initial uranium concentration and contact time, and the results expressed in terms of equilibrium adsorption capacities (qe) and partition coefficients (PC). By either criterion, performance increases from MNP to AMNP to DAMNP, with the maximum uptake at pH 5.5 in all cases: MNP, qe = 63 mg g-1, PC = 127 mg g-1 mM-1; AMNP, qe = 165 mg g-1, PC = 584 mg g-1 mM-1; DAMNP, qe = 249 mg g-1, PC = 2318 mg g-1 mM-1 (at 25 °C; initial U concentration 0.63 mM; 5 mg adsorbent in 10 mL of solution; contact time, 3 h). The pH maximum is related to the predominance of mono- and di-cationic uranium species. Uptake by DAMNPs follows a pseudo-first-order or pseudo-second-order kinetic model and fits a variety of adsorption models. The maximum adsorption capacity for DAMNPs is higher than for other functionalized magnetic nanohybrids. This adsorbent can be regenerated and recycled for at least 10 cycles with less than 10% loss in activity, and shows high selectivity. These findings suggest that DAMNP could be a promising adsorbent for the recovery of uranium from nuclear wastewaters.

Green, zero-waste pathway to fabricate supported nanocatalysts and anti-kinetoplastid agents from sugarcane bagasse.

The conversion processes of sugarcane into direct-consumption sugar and juice are generating a tremendous amount of waste, the so-called sugarcane bagasse (SCB). Biochar preparation is among the practical solutions aiming to manage and valorize SCB into high added-value functional material (FM). Herein, we propose a novel zero-waste pathway to fabricate two FMs from one biomass. The SCB was first macerated and ultrasonicated to obtain the natural extract that served as bio-reducing medium. Then, the H2O/EtOH-extracted SCB was in-situ impregnated with a bimetallic solution of copper and silver nitrates. The process produced an intermediate composite (FM0), Ag/Cu-Ag+/Cu2+-loaded SCB which was carbonized to elaborate Ag/Cu-Biochar (FM1), free Ag/Cu nanoparticles (FM2) were obtained by microwaving the residual liquid waste. FM1 exhibited high catalytic activity for the total Fenton-like degradation of methylene blue. The experimental data followed the pseudo-first and the pseudo-second order rate laws with apparent degradation rate constants K1 45 10-3 min-1 and K2 0.115 g.mg-1.min-1, respectively. FM0, FM1 and FM2 were tested as new anti-kinetoplastid materials against two flagellated protozoans namely the Leishmania spp and the Trypanosoma cruzi. Notably, Ag/Cu (FM2) showed exceptional leishmanicidal and trypanocidal effects with IC50 values of 2.909 ± 0.051, 3.580 ± 0.016 and 3.020 ± 0.372 ppm for L.donovani, L. amazonensis and Trypanosoma cruzi, respectively. In this way, we combine green chemistry and agrowaste valorization in a full zero-waste process, to address the 3rd (indicator 3.3.5) and 6th (indicator 6.3.1) United Nations sustainable development goals, ″Good Health and Well-Being″ and ″Clean Water and Sanitation″.

Electron transfer between carbon dots and tetranuclear Dawson-derived sandwich polyanions.

Among the photocatalysts which could be used for converting solar energy, polyoxometalates are often regarded as ideal candidates because of their remarkable performances in photocatalytic water splitting and photodegradation of pollutants. Nonetheless, these polyanions are only capable of absorbing UV light, unless coupled to a visible-light photosensitizer. Carbon nanodots are especially promising for this purpose because of their strong visible-light absorption, photostability, non-toxicity, and very low production costs. In this work we demonstrate the possibility of coupling carbon dots to polyoxometalates with different structures, by a simple self-assembly approach based on electrostatic interactions in solution phase. Our studies highlight an extremely efficient interaction between the two compounds, resulting in ultrafast photoinduced electron or energy transfer from carbon dots to the coupled polyoxometalates, depending on the structure of the latter, as revealed by a detailed study based on ultrafast transient absorption spectroscopy. The evidence herein provided shows how nanohybrids based on polyoxometalates photosensitized by carbon dots could find their place in photocatalytic applications, thanks to their remarkable efficiency and huge versatility.

Water Vapor Photoelectrolysis in a Solid-State Photoelectrochemical Cell with TiO2 Nanotubes Loaded with CdS and CdSe Nanoparticles.

In this study, polyol-made CdS and CdSe crystalline nanoparticles (NPs) are loaded by impregnation on TiO2 nanotube arrays (TNTAs) for solar-simulated light-driven photoelectrochemical (PEC) water vapor splitting. For the first time, we introduce a safe way to utilize toxic, yet efficient photocatalysts by integration in solid-state PEC (SSPEC) cells. The enabling features of SSPEC cells are the surface protonic conduction mechanism on TiO2 and the use of polymeric electrolytes, such as Nafion instead of liquid ones, for operation with gaseous reactants, like water vapor from ambient humidity. Herein, we studied the effects of both the operating conditions in gaseous ambient atmospheres and the surface modifications of TNTAs-based photoanodes with well-crystallized CdS and CdSe NPs. We showed 3.6 and 2.5 times increase in the photocurrent density of defective TNTAs modified with CdS and CdSe, respectively, compared to the pristine TNTAs. Electrochemical impedance spectroscopy and structural characterizations attributed the improved performance to the higher conductivity induced by intrinsic defects as well as to the enhanced electron/hole separation at the TiO2/CdS heterojunction under gaseous operating conditions. The SSPEC cells were evaluated by cycling between high relative humidity (RH) (80%) and low RH levels (40%), providing direct evidence of the effect of RH and, in turn, adsorbed water, on the cell performance. Online mass spectrometry indicated the corresponding difference in the H2 production rate. In addition, a complete restoration of the SSPEC cell performance from low to high RH levels was also achieved. The presented system can be employed in off-grid, water depleted, and air-polluted areas for the production of hydrogen from renewable energy and provides a solution for the safe use of toxic, yet efficient photocatalysts.

Preparation of Fe3O4-Ag Nanocomposites with Silver Petals for SERS Application.

The formation of silver nanopetal-Fe3O4 poly-nanocrystals assemblies and the use of the resulting hetero-nanostructures as active substrates for Surface Enhanced Raman Spectroscopy (SERS) application are here reported. In practice, about 180 nm sized polyol-made Fe3O4 spheres, constituted by 10 nm sized crystals, were functionalized by (3-aminopropyl)triethoxysilane (APTES) to become positively charged, which can then electrostatically interact with negatively charged silver seeds. Silver petals were formed by seed-mediated growth in presence of Ag+ cations and self-assembly, using L-ascorbic acid (L-AA) and polyvinyl pyrrolidone (PVP) as mid-reducing and stabilizing agents, respectively. The resulting plasmonic structure provides a rough surface with plenty of hot spots able to locally enhance significantly any applied electrical field. Additionally, they exhibited a high enough saturation magnetization with Ms = 9.7 emu g-1 to be reversibly collected by an external magnetic field, which shortened the detection time. The plasmonic property makes the engineered Fe3O4-Ag architectures particularly valuable for magnetically assisted ultra-sensitive SERS sensing. This was unambiguously established through the successful detection, in water, of traces, (down to 10-10 M) of Rhodamine 6G (R6G), at room temperature.

Grafting TRAIL through Either Amino or Carboxylic Groups onto Maghemite Nanoparticles: Influence on Pro-Apoptotic Efficiency.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF cytokine superfamily. TRAIL is able to induce apoptosis through engagement of its death receptors DR4 and DR5 in a wide variety of tumor cells while sparing vital normal cells. This makes it a promising agent for cancer therapy. Here, we present two different ways of covalently grafting TRAIL onto maghemite nanoparticles (NPs): (a) by using carboxylic acid groups of the protein to graft it onto maghemite NPs previously functionalized with amino groups, and (b) by using the amino functions of the protein to graft it onto NPs functionalized with carboxylic acid groups. The two resulting nanovectors, NH-TRAIL@NPs-CO and CO-TRAIL@NPs-NH, were thoroughly characterized. Biological studies performed on human breast and lung carcinoma cells (MDA-MB-231 and H1703 cell lines) established these nanovectors are potential agents for cancer therapy. The pro-apoptotic effect is somewhat greater for CO-TRAIL@NPs-NH than NH-TRAIL@NPs-CO, as evidenced by viability studies and apoptosis analysis. A computational study indicated that regardless of whether TRAIL is attached to NPs through an acid or an amino group, DR4 recognition is not affected in either case.

Polyol Synthesis: A Versatile Wet-Chemistry Route for the Design and Production of Functional Inorganic Nanoparticles.

The term "polyol process" was first used in the late eighties by Fiévet, Lagier, and Figlarz [...].

Highly Efficient Electron Transfer in a Carbon Dot-Polyoxometalate Nanohybrid.

Using solar radiation to fuel catalytic processes is often regarded as the solution to our energy needs. However, developing effective photocatalysts that are active under visible light has proven to be difficult, often due to the toxicity, instability, and high cost of suitable catalysts. We engineered a novel photoactive nanomaterial obtained by the spontaneous electrostatic coupling of carbon nanodots with [P2W18O62]6-, a molecular catalyst belonging to the class of polyoxometalates. While the former are used as photosensitizers, the latter was chosen for its ability to catalyze reductive reactions such as dye decomposition and water splitting. We find the electron transfer within the nanohybrid to be so efficient that a charge-separated state is formed within 120 fs from photon absorption. These results are a cornerstone in the engineering of a new class of nanodevices, which are nontoxic, are inexpensive, and can carry out solar-driven catalytic processes.

Synthesis of Magnetic Wires from Polyol-Derived Fe-Glycolate Wires.

Fe-glycolate wires with micrometer-scale lengths can be synthesized by the polyol process. Although the as-produced wires are in the paramagnetic state at room temperature, they are transformed into ferrimagnetic iron oxides and ferromagnetic metallic iron wires by reductive annealing. The shape of the wires is unchanged by reductive annealing, and it is possible to control the magnetic properties of the resulting wire-shaped ferri/ferromagnets by adjusting the annealing conditions. Consequently, the reductive annealing of polyol-derived Fe-glycolate wires is an effective material-processing route for the production of magnetic wires.

Polyol-Made Luminescent and Superparamagnetic ß-NaY0.8Eu0.2F4@γ-Fe2O3 Core-Satellites Nanoparticles for Dual Magnetic Resonance and Optical Imaging.

Red luminescent and superparamagnetic ß-NaY0.8Eu0.2F4@γ-Fe2O3 nanoparticles, made of a 70 nm-sized ß-NaY0.8Eu0.2F4 single crystal core decorated by a 10 nm-thick polycrystalline and discontinuous γ-Fe2O3 shell, have been synthesized by the polyol process. Functionalized with citrate ligands they show a good colloidal stability in water making them valuable for dual magnetic resonance and optical imaging or image-guided therapy. They exhibit a relatively high transverse relaxivity r2 = 42.3 mM-1·s-1 in water at 37 °C, for an applied static magnetic field of 1.41 T, close to the field of 1.5 T applied in clinics, as they exhibit a red emission by two-photon excited fluorescence microscopy. Finally, when brought into contact with healthy human foreskin fibroblast cells (BJH), for doses as high as 50 µg·mL-1 and incubation time as long as 72 h, they do not show evidence of any accurate cytotoxicity, highlighting their biomedical applicative potential.

Star-Shaped Fe3-xO4-Au Core-Shell Nanoparticles: From Synthesis to SERS Application.

In this work, the preparation of magneto-plasmonic granular nanostructures and their evaluation as efficient substrates for magnetically assisted surface enhanced Raman spectroscopy (SERS) sensing are discussed. These nanostructures consist of star-shaped gold Au shell grown on iron oxide Fe3-xO4 multicores. They were prepared by seed-mediated growth of anisotropic, in shape gold nanosatellites attached to the surface of polyol-made iron oxide polycrystals. In practice, the 180 nm-sized spherical iron oxide particles were functionalized by (3-aminopropyl) triethoxysilane (APTES) to become positively charged and to interact, in solution, with negatively charged 2 nm-sized Au single crystals, leading to nanohybrids. These hybrids acted subsequently as nucleation platforms for the growth of a branched gold shell, when they were contacted to a fresh HAuCl4 gold salt aqueous solution, in the presence of hydroquinone, a reducing agent, for an optimized nominal weight ratio between both the starting hybrids and the gold salt. As expected, the resulting nanocomposites exhibit a high saturation magnetization at room temperature and a rough enough plasmonic surface, making them easily attracted by a lab. magnet, while exhibiting a great number of SERS hot spots. Preliminary SERS detection assays were successfully performed on diluted aqueous thiram solution (10-8 M), using these engineered substrates, highlighting their capability to be used as chemical trace sensors.

On the first evidence of exchange-bias feature in magnetically contrasted consolidates made from CoFe2O4-CoO core-shell nanoparticles.

Hetero-nanostructures based on magnetic contrast oxides have been prepared as highly dense nanoconsolidates. Cobalt ferrite-cobalt oxide core-shell type nanoparticles (NPs) were synthesized by seed mediated growth in polyol and subsequently consolidated by Spark Plasma Sintering (SPS) at 500 °C for a few minutes while applying a uniaxial pressure of 100 MPa. It is interesting to note that the exchange bias feature observed in the core-shell NPs is reproduced in their ceramic counterparts, or even attenuated. A systematic structural characterization was then carried out to elucidate the decrease in the exchange magnetic field, involving mainly advanced X-ray diffraction, zero-field and in-field 57Fe Mössbauer spectrometry, magnetic measurements and electron microscopy.

On the limits of Reactive-Spark-Plasma Sintering to prepare magnetically enhanced nanostructured ceramics: the case of the CoFe2O4-NiO system.

Magnetic materials are crucial for the efficiency of the conversion-storage-transport-reconversion energy chain, and the enhancement of their performance has an important impact on technological development. The present work explores the possibility of preparing hetero-nano-structured ceramics based on magnetic oxides, by coupling a ferrimagnetic phase (F) with an antiferromagnetic one (AF) on the nanometric scale. The field-assisted sintering technique or SPS (Spark-Plasma Sintering), adopted at this purpose, ensures the preservation of nano-sized crystals within the final solid structure. The aim is to establish how exchange bias may affect the resulting nano-consolidates and to investigate the potential of this process to increase the total magnetic anisotropy of the CoFe2O4 grains, and thus their coercive field, while keeping the saturation magnetization the same. The structure, microstructure and magnetic properties of the ceramics obtained were studied by several techniques. The results show that the sintering process, along with its typical reductive atmosphere, modifies the composition of the constituents. A new metallic phase appears as a consequence of the reciprocal diffusion of Co and Ni cations, leading to a change in the amount and structure of the AF phase. We propose a schematic representation of the atomic movements that hinder an exchange bias effect between the F and AF phases.

TRAIL acts synergistically with iron oxide nanocluster-mediated magneto- and photothermia.

Targeting TRAIL (Tumor necrosis factor (TNF)-Related Apoptosis-Inducing Ligand) receptors for cancer therapy remains challenging due to tumor cell resistance and poor preparations of TRAIL or its derivatives. Herein, to optimize its therapeutic use, TRAIL was grafted onto iron oxide nanoclusters (NCs) with the aim of increasing its pro-apoptotic potential through nanoparticle-mediated magnetic hyperthermia (MHT) or photothermia (PT). Methods: The nanovector, NC@TRAIL, was characterized in terms of size, grafting efficiency, and potential for MHT and PT. The therapeutic function was assessed on a TRAIL-resistant breast cancer cell line, MDA-MB-231, wild type (WT) or TRAIL-receptor-deficient (DKO), by combining complementary methylene blue assay and flow cytometry detection of apoptosis and necrosis. Results: Combined with MHT or PT under conditions of "moderate hyperthermia" at low concentrations, NC@TRAIL acts synergistically with the TRAIL receptor to increase the cell death rate beyond what can be explained by the mere global elevation of temperature. In contrast, all results are consistent with the idea that there are hotspots, close to the nanovector and, therefore, to the membrane receptor, which cause disruption of the cell membrane. Furthermore, nanovectors targeting other membrane receptors, unrelated to the TNF superfamily, were also found to cause tumor cell damage upon PT. Indeed, functionalization of NCs by transferrin (NC@Tf) or human serum albumin (NC@HSA) induces tumor cell killing when combined with PT, albeit less efficiently than NC@TRAIL. Conclusions: Given that magnetic nanoparticles can easily be functionalized with molecules or proteins recognizing membrane receptors, these results should pave the way to original remote-controlled antitumoral targeted thermal therapies.

Tailoring the magnetic properties of cobalt ferrite nanoparticles using the polyol process.

Background: In extrinsically magnetoelectric materials made of two components, the direct magnetoelectric coupling arises from a mechanical strain transmission at the interface due to the shape change of the magnetostrictive component under an external magnetic field. Here, the size of the interface between the two components plays a crucial role. Therefore, the development of nanomaterials exhibiting large surface-to-volume ratios can help to respond to such a requirement. However, the magnetic nanoparticles (NPs) must be highly magnetostrictive and magnetically blocked at room temperature despite their nanometer-size. We describe here the use of the polyol process to synthesize cobalt ferrite (Co x Fe3- x O4) nanoparticles with controlled size and composition and the study of the relationship between size and composition and the magnetic behavior. Methods: We used an improved synthesis of magnetostrictive Co x Fe3- x O4 NPs based on the forced hydrolysis of metallic salts in a polyol solvent, varying the fraction x. Stoichiometric NPs (x = 1) are expected to be highly magnetostrictive while the sub-stoichiometric NPs (particularly for x ≈ 0.7) are expected to be less magnetostrictive but to present a higher magnetocrystalline anisotropy constant, as previously observed in bulk cobalt ferrites. To control the size of the NPs, in order to overcome the superparamagnetic limit, as well as their chemical composition, in order to get the desired magnetomechanic properties, we carried out the reactions for two nominal precursor contents (x = 1 and 0.67), using two different solvents, i.e., triethylene glycol (TriEG) and tetraethylene glycol (TetEG), and three different durations of refluxing (3, 6 and 15 h). The structure, microstructure and composition of the resulting NPs were then investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray fluorescence spectroscopy (XRF), respectively. The magnetic properties were also evaluated using standard magnetometry. To measure the magnetostrictive response of the particles, the particles were sintered to dense pellets on which strain gauges were bonded, measuring the size variation radially, as a function of a dc magnetic field. Findings: We found two samples, the first one being stoichiometric and magnetostrictive, and the second one being sub-stoichiometric and presenting a higher magnetization, that are appropriate to be used as ferromagnetic building blocks in nanostructured magnetoelectric materials, particularly materials based on polymers. We show that the polyol solvent and the reaction time are two key parameters to control the size and the magnetic properties of the resulting nanoparticles. We believe that these results provide relevant insights to the design of efficient magnetic and magnetostrictive nanoparticles that can be further functionalized by coupling agents, to be contacted with piezoelectric polymers.

New Iron Oxide Nanoparticles Catechol-Grafted with Bis(amidoxime)s for Uranium(VI) Depletion of Aqueous Solution.

Environmental pollution caused by heavy metals constitutes a serious public health problem. In the case of uranium depletion, amidoxime groups are important because of their high affinity for uranium(VI). New series of bis(amidoxime)s with catechol-derived anchor groups were tested (b-AMD-1 and b-AMD-2). The catechol groups were designed to bind to the surface of maghemite nanoparticles (MNPs), and two nanohybrid devices MNP-b-AMD-1 and MNP-b-AMD-2 were obtained. This strategy makes for efficient removal of U(VI) via its complexation with the bis(amidoxime)s (b-AMD) and also its extraction from aqueous solution by magnetic harvesting of the MNPs. The assynthesized and b-AMD-grafted MNPs were characterized by several techniques: X-ray diffraction (XRD), high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), X-ray photoelectron spectrophotometry (XPS), thermal analysis (TG/DTA) and Fourier transform infrared spectroscopy (FTIR). Sorption tests were run at pH 6.5, which corresponds to the highest affinity and selectivity of b-AMD for U(VI). After magnetic separation, the chelation ability and the selectivity of MNP-b-AMD-1 and MNP-b-AMD-2 towards U(VI) were evaluated by measuring the residual U(VI) concentration in the supernatant by inductively coupled plasma-mass spectrometry (ICP-MS). The data were plotted according to the Langmuir and Freundlich isotherms; the maximal sorption capacity (qmax) was 29 and 60 mg U g-1 for MNP-b-AMD-1 and MNP-b-AMD-2, respectively. This confirms that bis(amidoxime) groups are good candidates for uranium depletion of aqueous solution.