Implementing magnetically-active Sn-based nanocomposites in hexavalent chromium removal from drinking water.

A novel nanocomposite consisting of Fe3O4-loaded tin oxyhydroxy-chloride is demonstrated as an efficient adsorbent for the removal of hexavalent chromium in compliance to the new drinking water regulation. This study introduces a continuous-flow production of the nanocomposite through the separate synthesis of (i) 40 nm Fe3O4 nanoparticles and (ii) multilayered spherical arrangements of a tin hydroxy-chloride identified as abhurite, before the application of a wet-blending process. The homogeneous distribution of Fe3O4 nanoparticles on the abhurite's morphology, features nanocomposite with magnetic response whereas the 10 % loaded nanocomposite preserves a Cr(VI) uptake capacity of 7.2 mg/g for residual concentrations below 25 µg/L. Kinetic and thermodynamic examination of the uptake evolution indicates a relative rapid Cr(VI) capture dominated by interparticle diffusion and a spontaneous endothermic process mediated by reduction to Cr(III). The efficiency of the optimized nanocomposite was validated in a pilot unit operating in a sequence of a stirring reactor and a rotary magnetic separator showing an alternative and competitive application path than typical fixed-bed filtration, which is supported by the absence of any acute cellular toxicity according to human kidney cell viability tests.

Toward the Separation of Different Heating Mechanisms in Magnetic Particle Hyperthermia.

Magnetic particle hyperthermia (MPH) is a promising method for cancer treatment using magnetic nanoparticles (MNPs), which are subjected to an alternating magnetic field for local heating to the therapeutic range of 41-45 °C. In this window, the malignant regions (i.e., cancer cells) undergo a severe thermal shock while healthy tissues sustain this thermal regime with significantly milder side effects. Since the heating efficiency is directly associated with nanoparticle size, MNPs should acquire the appropriate size to maximize heating together with minimum toxicity. Herein, we report on facile synthetic controls to synthesize MNPs by an aqueous precipitation method, whereby tuning the pH values of the solution (9.0-13.5) results in a wide range of average MNP diameters from 16 to 76 nm. With respect to their size, the structural and magnetic properties of the MNPs are evaluated by adjusting the most important parameters, i.e. the MNP surrounding medium (water/agarose), the MNP concentration (1-4 mg mL-1), and the field amplitude (20-50 mT) and frequency (103, 375, 765 kHz). Consequently, the maximum heating efficiency is determined for each MNP size and set of parameters, outlining the optimum MNPs for MPH treatment. In this way, we can address the different heat generation mechanisms (Brownian, Néel, and hysteresis losses) to different sizes and separate Brownian and hysteresis losses for optimized sizes by studying the heat generation as a function of the medium viscosity. Finally, MNPs immobilized into agarose solution are studied under low-field MPH treatment to find the optimum conditions for clinical applications.

Composite PLGA-Nanobioceramic Coating on Moxifloxacin-Loaded Akermanite 3D Porous Scaffolds for Bone Tissue Regeneration.

Silica-based ceramics doped with calcium and magnesium have been proposed as suitable materials for scaffold fabrication. Akermanite (Ca2MgSi2O7) has attracted interest for bone regeneration due to its controllable biodegradation rate, improved mechanical properties, and high apatite-forming ability. Despite the profound advantages, ceramic scaffolds provide weak fracture resistance. The use of synthetic biopolymers such as poly(lactic-co-glycolic acid) (PLGA) as coating materials improves the mechanical performance of ceramic scaffolds and tailors their degradation rate. Moxifloxacin (MOX) is an antibiotic with antimicrobial activity against numerous aerobic and anaerobic bacteria. In this study, silica-based nanoparticles (NPs) enriched with calcium and magnesium, as well as copper and strontium ions that induce angiogenesis and osteogenesis, respectively, were incorporated into the PLGA coating. The aim was to produce composite akermanite/PLGA/NPs/MOX-loaded scaffolds through the foam replica technique combined with the sol-gel method to improve the overall effectiveness towards bone regeneration. The structural and physicochemical characterizations were evaluated. Their mechanical properties, apatite forming ability, degradation, pharmacokinetics, and hemocompatibility were also investigated. The addition of NPs improved the compressive strength, hemocompatibility, and in vitro degradation of the composite scaffolds, resulting in them keeping a 3D porous structure and a more prolonged release profile of MOX that makes them promising for bone regeneration applications.

Incorporating Graphene Nanoplatelets and Carbon Nanotubes in Biobased Poly(ethylene 2,5-furandicarboxylate): Fillers' Effect on the Matrix's Structure and Lifetime.

Poly(ethylene 2,5-furandicarboxylate) (PEF) nanocomposites reinforced with Graphene nanoplatelets (GNPs) and Carbon nanotubes (CNTs) were in situ synthesized in this work. PEF is a biobased polyester with physical properties and is the sustainable counterpart of Polyethylene Terephthalate (PET). Its low crystallizability affects the processing of the material, limiting its use to packaging, films, and textile applications. The crystallization promotion and the reinforcement of PEF can lead to broadening its potential applications. Therefore, PEF nanocomposites reinforced with various loadings of GNPs, CNTs, and hybrids containing both fillers were prepared, and the effect of each filler on their structural characteristics was investigated by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), and X-Ray Photoelectron Spectroscopy (XPS). The morphology and structural properties of a hybrid PEF nanocomposite were evaluated by Transmission Electron Microscopy (TEM). The thermo-oxidative degradation, as well as lifetime predictions of PEF nanocomposites, in an ambient atmosphere, were studied using Thermogravimetric Analysis (TGA). Results showed that the fillers' incorporation in the PEF matrix induced changes in the lamellar thickness and increased crystallinity up to 27%. TEM analysis indicated the formation of large CNTs aggregates in the case of the hybrid PEF nanocomposite as a result of the ultrasonication process. Finally, the presence of CNTs caused the retardation of PEF's carbonization process. This led to a slightly longer lifetime under isothermal conditions at higher temperatures, while at ambient temperature the PEF nanocomposites' lifetime is shorter, compared to neat PEF.

THz emission from Fe/Pt spintronic emitters with L10-FePt alloyed interface.

Recent developments in nanomagnetism and spintronics have enabled the use of ultrafast spin physics for terahertz (THz) emission. Spintronic THz emitters, consisting of ferromagnetic (FM)/non-magnetic (NM) thin film heterostructures, have demonstrated impressive properties for the use in THz spectroscopy and have great potential in scientific and industrial applications. In this work, we focus on the impact of the FM/NM interface on the THz emission by investigating Fe/Pt bilayers with engineered interfaces. In particular, we intentionally modify the Fe/Pt interface by inserting an ordered L10-FePt alloy interlayer. Subsequently, we establish that a Fe/L10-FePt (2 nm)/Pt configuration is significantly superior to a Fe/Pt bilayer structure, regarding THz emission amplitude. The latter depends on the extent of alloying on either side of the interface. The unique trilayer structure opens new perspectives in terms of material choices for the next generation of spintronic THz emitters.

Electrospun PLGA Membranes with Incorporated Moxifloxacin-Loaded Silica-Based Mesoporous Nanocarriers for Periodontal Regeneration.

Engineered electrospun membranes have emerged as promising materials in guided tissue regeneration, as they provide an appropriate framework for the formation of new functional periodontal tissues. The development of multifunctional local drug delivery systems with sustained release of drugs for prolonged infection control can be used in periodontal surgical interventions to simultaneously prohibit epithelium downgrowth and ensure proper healing and regeneration of damaged periodontal tissues. The aim of the present study was the fabrication of novel composite membranes from PLGA/moxifloxacin-loaded mesoporous nanocarriers through electrospinning and the evaluation of their drug release profiles. The addition of moxifloxacin-loaded mesoporous nanocarriers in PLGA yielded a sustained and prolonged drug release, while maintaining satisfactory mechanical strength. The freshly fabricated membranes were found to be biocompatible at masses less than 1 mg after exposure to healthy erythrocytes. Increase in the amount of polymer led to more uniform fibers with large diameters and pores. The study of the parameters of the electrospinning process indicated that increase in the applied voltage value and rotation speed of the collector led to more uniform fibers with higher diameter and larger pores, suitable for tissue regeneration applications, such as periodontal tissue regeneration.

Magnetization Reversal and Dynamics in Epitaxial Fe/Pt Spintronic Bilayers Stimulated by Interfacial Fe3O4 Nanoparticles.

We have explored the impact of elevated growth and annealing temperatures on the local interfacial structure of thin Fe(12 nm)/Pt(10 nm) spintronic bilayers, epitaxially grown on MgO (100), and their correlation to magnetization reversal and dynamics. Electron-beam evaporation growth and subsequent annealing at 450 °C causes significant roughening of the MgO/Fe interface with irregular steps and multilevel (100) MgO surface terraces. Consequently, threading dislocations emerging at the step edges propagated in the Fe layer and terminated at the Fe/Pt interface, which appears pitted with pits 1.5-3 nm deep on the Fe side. Most of the pits are filled with the overlying Pt, whereby others by ferrimagnetic Fe3O4, forming nanoparticles that occupy nearly 9% of the Fe/Pt interfacial area. Fe3O4 nanoparticles occur at the termination sites of threading dislocations at the Fe/Pt interface, and their population density is equivalent to the density of threading dislocations in the Fe layer. The morphology of the Fe/Fe3O4/Pt system has a strong impact on the magnetization reversal, enhancing the coercive field and inducing an exchange bias below 200 K. Furthermore, low-temperature spin pumping and inverse spin Hall effect voltage measurements reveal that below their blocking temperature the nanoparticles can influence the spin current transmission and the spin rectification effects.

The dome of Rotunda in Thessaloniki: Investigation of a multi-pictorial phase wall painting through analytical methods.

The present study focuses on the investigation of the successive pictorial phases of the wall painting which survives on the missing eastern part of the magnificent mosaic composition in the interior of Rotunda, Thessaloniki, Greece. Rotunda, a circular domed monumental building, was constructed in the early 4th century AD and it is included in the UNESCO World Heritage List. Characterization analysis was performed by means of microscopic, spectroscopic and crystallographic techniques, in order to identify the technological features of the wall painting and the materials used, to document the initial Byzantine pictorial phase -known from the archaeological research- along with the overpaintings attributed to the 19th and 20th centuries. In this framework, the collected samples were studied with optical microscopy, Fourier transform infrared micro-spectroscopy, scanning electron microscopy, X-ray diffractometry and X-ray photoelectron spectroscopy. Among the detected materials and pigments (including zinc oxide, barium sulfate, red lead, green earth, Prussian blue, emerald green, ultramarine and cuprite), the use of brass powder for false gilding purposes was detected, which is a material rarely used for mural applications.

Mechanical and thermal properties of PMMA resin composites for interim fixed prostheses reinforced with calcium ß-pyrophosphate.

Interim restorations are essential in fixed prosthodontics as they provide temporary protection of teeth before the insertion of the permanent restoration. Poly(methyl methacrylate) (PMMA) is widely used in the fabrication of interim-fixed restorations as it is a biocompatible material with a lot of convenient properties. However, it exhibits low impact and tensile strength and therefore it is necessary to be reinforced. Calcium ß-pyrophosphate (ß-CPP) is considered a promising reinforcing material for dental applications, especially for enamel regeneration due to its stability at low pH and its low wear rate. The aim of this study was to manufacture PMMA/ß-CPP composites suitable for fixed-interim restorations and to study their mechanical and thermal properties. In order to enhance ß-CPP dispersion into PMMA matrix, ball-milling was performed for 1 or 6 h. Three-point bending test was performed to study flexural strength, Dynamic Mechanical Analysis (DMA) to reveal the elastic and viscous moduli along with Tg, Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction Analysis (XRD) to investigate the structure of the materials and SEM for the morphological evaluation of both composite powders and polymerized specimens. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) experiments were performed to study their thermal properties. A statistically significant increase in flexural strength was found in the 0.5, 0.75 and 1% composite groups after 6 h ball-milling, relative to the control, with the 6 h ball milling mixed specimens, presenting the highest flexural strength values. The brittle fracture type was common to all groups. An obvious improvement of the mechanical properties and a slight improvement in the thermal stability of the composite materials values were also observed as ß-CPP content was increased, while Tg values were statistically not-affected.

Influence of Graphene Platelet Aspect Ratio on the Mechanical Properties of HDPE Nanocomposites: Microscopic Observation and Micromechanical Modeling.

A series of high-density polyethylene nanocomposites filled with different diameter sizes (5, 15, and 25 µm) of graphene nanoplatelets at various amounts (0.5-5 wt.%) are prepared by the melt-mixing method. The effect of diameter size and filler content on the mechanical properties is reported, and the results are discussed in terms of morphology and the state of dispersion within the polymer matrix. The measured stiffness and strength of the nanocomposites were found to be mainly influenced by the filler aspect ratio and the filler-matrix adhesion. Fractography was utilized to study the embrittleness of the nanocomposites, and the observations revealed that a ductile to brittle transition is caused by a micro-deformation mechanism change in the nanocomposites. Several micromechanical models for the prediction of mechanical properties of nanocomposites, taking into consideration filler aspect ratio, percolation effect, and interphase regions, are considered. The three-phase model proposed by Ji accurately predicts the stiffness of graphene nanoplatelets with a higher diameter size, while Takayanagi modified model II was found to show good agreement with the experimental results of smaller ones at low filler content. This study demonstrates that the diameter size of the filler plays a central role in determining the mechanical properties.

Stabilization of Cr-rich tannery waste in fly ash matrices.

In the present work, the stabilization/solidification of a Cr-rich ash obtained from the anoxic incineration of tannery hazardous wastes was studied. Chromium in the starting waste was exclusively in amorphous form and in trivalent state. The waste was embedded in fly ash-based cementitious material matrices. Calcium and sodium hydroxides, as well as sodium silicate, were used as activators. The proposed process combines mechanical activation with hydrothermal curing. Successful immobilization of chromium was achieved, as attested by standard leaching tests. Backscattered electron images revealed the existence of the C-S-H gel, and elemental mapping by energy dispersive X-ray spectroscopy showed a good interdispersion of chromate and aluminosilicate species, verifying that chromium was well distributed in the final amorphous cementitious matrix. X-ray diffraction confirmed the absence of Cr-rich crystalline phases of calcium aluminosilicates, where chromium can enter in hexavalent state. The stiffness of the stabilized samples was reduced with increasing the amount of added Cr-rich ash, as attested by measurements of the dynamic Young's modulus.

Remarkable Enhancement of the Hole Mobility in Several Organic Small-Molecules, Polymers, and Small-Molecule:Polymer Blend Transistors by Simple Admixing of the Lewis Acid p-Dopant B(C6F5)3.

Improving the charge carrier mobility of solution-processable organic semiconductors is critical for the development of advanced organic thin-film transistors and their application in the emerging sector of printed electronics. Here, a simple method is reported for enhancing the hole mobility in a wide range of organic semiconductors, including small-molecules, polymers, and small-molecule:polymer blends, with the latter systems exhibiting the highest mobility. The method is simple and relies on admixing of the molecular Lewis acid B(C6F5)3 in the semiconductor formulation prior to solution deposition. Two prototypical semiconductors where B(C6F5)3 is shown to have a remarkable impact are the blends of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene:poly(triarylamine) (diF-TESADT:PTAA) and 2,7-dioctyl[1]-benzothieno[3,2-b][1]benzothiophene:poly(indacenodithiophene-co-benzothiadiazole) (C8-BTBT:C16-IDTBT), for which hole mobilities of 8 and 11 cm2 V-1 s-1, respectively, are obtained. Doping of the 6,13-bis(triisopropylsilylethynyl)pentacene:PTAA blend with B(C6F5)3 is also shown to increase the maximum hole mobility to 3.7 cm2 V-1 s-1. Analysis of the single and multicomponent materials reveals that B(C6F5)3 plays a dual role, first acting as an efficient p-dopant, and secondly as a microstructure modifier. Semiconductors that undergo simultaneous p-doping and dopant-induced long-range crystallization are found to consistently outperform transistors based on the pristine materials. Our work underscores Lewis acid doping as a generic strategy towards high performance printed organic microelectronics.

Enrichment and oral bioaccessibility of selected trace elements in fly ash-derived magnetic components.

The mineralogy, morphology, and chemical composition of magnetic fractions separated from fly ashes (FAs) originating from Greek lignite-burning power plants was investigated. The oral bioaccessibility of potentially harmful elements (PHEs) from the fly ash magnetic fractions (FAMFs) was also assessed using in vitro gastrointestinal extraction (BARGE Unified Bioaccessibility Method, UBM). The FAMFs isolated were in the range 4.6-18.4%, and their mass specific magnetic susceptibility ranged from 1138 × 10-8 to 1682 × 10-8 m3/kg. XRD analysis and Mossbauer spectroscopy indicated that the dominant iron species were Fe-rich aluminosilicate glass along with magnetite, hematite, and maghemite (in decreasing order). The raw FAs exhibited differences in their chemical composition, indicating the particularity of every lignite basin. The elemental contents of FAMFs presented trends with fly ash type; thus, the FAMFs of high-Ca FAs were enriched in siderophile (Cr, Co, Ni) and lithophile (Cs, Li, Rb) elements and those separated from low-Ca FAs were presented depleted in chalcophile elements. Based on UBM extraction tests, the PHEs were more bioaccessible from the non-magnetic components of the FAs compared to the magnetic ones; however, the bioaccessible fractions estimated for the FAMFs were exceeding 40 % in many cases. Arsenic was found to be significantly bioaccessible (median ~ 80 %) from FAMFs despite the lower As contents in the magnetic fraction.

Small Molecule/Polymer Blend Organic Transistors with Hole Mobility Exceeding 13 cm(2) V(-1) s(-1).

A ternary organic semiconducting blend composed of a small-molecule, a conjugated polymer, and a molecular p-dopant is developed and used in solution-processed organic transistors with hole mobility exceeding 13 cm(2) V(-1) s(-1) (see the Figure). It is shown that key to this development is the incorporation of the p-dopant and the formation of a vertically phase-separated film microstructure.

Composition and hydrophilicity control of Mn-doped ferrite (MnxFe3-xO4) nanoparticles induced by polyol differentiation.

Manganese doped ferrite (MnxFe3-xO4) nanoparticles with x = 0.29-0.77 were prepared under solvothermal conditions in the presence solely of a polyol using the trivalent manganese and iron acetylacetonates as precursors. In this facile approach, a variety of polyols such as polyethylene glycol (PEG 8000), tetraethylene glycol (TEG), propylene glycol (PG) and a mixture of TEG and PG (1 : 1) were utilized in a triple role as a solvent, a reducing agent and a surface-functionalizing agent. The composition of the fine cubic-spinel structures was found to be related to the reductive ability of each polyol, while determination of structural characteristics plus the inversion parameter (i = 0.18-0.38) were provided by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy at both the Fe and Mn K-edges. The saturation magnetization increased up to 80 emu g(-1) when x = 0.35 and i = 0.22. In addition, the as-prepared nanocrystals coated with PEG, PG and PG&TEG showed excellent colloidal stability in water, while the TEG-coated particles were not water dispersible and converted to hydrophilic when were extra PEGylated. Measurements of the (1)H NMR relaxation in water were carried out and the nanoprobes were evaluated as potential contrast agents.

Tetravalent manganese feroxyhyte: a novel nanoadsorbent equally selective for As(III) and As(V) removal from drinking water.

The development of a single-phase Fe/Mn oxy-hydroxide (δ-Fe0.76Mn0.24OOH), highly efficient at adsorbing both As(III) and As(V), is reported. Its synthesis involves the coprecipitation of FeSO4 and KMnO4 in a kilogram-scale continuous process, in acidic and strongly oxidizing environments. The produced material was identified as a manganese feroxyhyte in which tetravalent manganese is homogeneously distributed into the crystal unit, whereas a second-order hollow spherical morphology is favored. According to this structuration, the oxy-hydroxide maintains the high adsorption capacity for As(V) of a single Fe oxy-hydroxide combined with enhanced As(III) removal based on the oxidizing mediation of Mn(IV). Ion-exchange between arsenic species and sulfates as well as the strongly positive surface charge further facilitate arsenic adsorption. Batch adsorption tests performed in natural-like water indicate that Mn(IV)-feroxyhyte can remove 11.7 µg As(V)/mg and 6.7 µg As(III)/mg at equilibrium pH 7, before residual concentration overcomes the regulation limit of 10 µg As/L for drinking water. The improved efficiency of this material, its low cost, and the possibility for scaling-up its production to industry indicate the high practical impact and environmental importance of this novel adsorbent.

Kilogram-scale synthesis of iron oxy-hydroxides with improved arsenic removal capacity: study of Fe(II) oxidation--precipitation parameters.

Various iron oxy-hydroxides were synthesized in a continuous flow kilogram-scale production reactor through the precipitation of FeSO(4) and FeCl(2) in the pH range 3-12 under intense oxidative conditions to serve as arsenic adsorbents. The selection of the optimum adsorbent and the corresponding conditions of the synthesis was based not only on its maximum As(III) and As(V) adsorption capacity but also on its potential efficiency to achieve the arsenic health regulation limit in NSF challenge water. As a result, the adsorbent prepared at pH 4, which consists of schwertmannite, was selected because it exhibited the highest adsorption capacity of 13 µg As(V)/mg, while maintaining a residual arsenic concentration of 10 µg/L at an equilibrium pH 7. The high surface charge and the activation of an ion-exchange mechanism between SO(4)(2-) adsorbed in the Stern layer and arsenate ions were found to significantly contribute to the increased adsorption capacity. Adsorption capacity values observed in rapid scale column experiments illustrate the improved efficiency of the qualified adsorbent compared to the common commercial arsenic adsorbents.