Periodic table screening for enhanced positive contrast in MRI and in vivo uptake in glioblastoma

The quest for nanomaterial-based imaging probes that can provide positive contrast in MRI is fueled by the necessity of developing novel diagnostic applications with potential for clinical translation that current gold standard probes cannot provide. Although interest in nanomaterials for positive contrast has increased in recent years, their study is less developed than that of traditional negative contrast probes in MRI. In our search for new magnetic materials with enhanced features as positive contrast probes for MRI, we decided to explore the chemical space to comprehensively analyze the effects of different metals on the performance of iron oxide nanomaterials already able to provide positive contrast in MRI. To this end, we synthesized 30 different iron oxide-based nanomaterials. Thorough characterization was performed, including multivariate analysis, to study the effect of different variables on their relaxometric properties. Based on these results, we identified the best combination of metals for in vivo imaging and tested them in different experiments. First, we tested its performance on magnetic resonance angiography using a concentration ten times lower than that clinically approved for Gd. Finally, we studied the capability of these nanomaterials to cross the affected blood-brain barrier in a glioblastoma model. The results showed that the selected nanomaterials provided excellent positive contrast at large magnetic field and were able to accumulate at the tumor site, highlighting the affected tissue.

New 3D Vortex Microfluidic System Tested for Magnetic Core-Shell Fe3O4-SA Nanoparticle Synthesis

This study's main objective was to fabricate an innovative three-dimensional microfluidic platform suitable for well-controlled chemical syntheses required for producing fine-tuned nanostructured materials. This work proposes using vortex mixing principles confined within a 3D multilayered microreactor to synthesize magnetic core-shell nanoparticles with tailored dimensions and polydispersity. The newly designed microfluidic platform allowed the simultaneous obtainment of Fe3O4 cores and their functionalization with a salicylic acid shell in a short reaction time and under a high flow rate. Synthesis optimization was also performed, employing the variation in the reagents ratio to highlight the concentration domains in which magnetite is mainly produced, the formation of nanoparticles with different diameters and low polydispersity, and the stability of colloidal dispersions in water. The obtained materials were further characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM), with the experimental results confirming the production of salicylic acid-functionalized iron oxide (Fe3O4-SA) nanoparticles adapted for different further applications.

Magnetic induction heating and drug release properties of magnetic carbon nanotubes

AIM

The use of magnetic carbon nanotubes for multi-modal cancer treatment, incorporating both hyperthermia and drug delivery functions, has drawn substantial interest. Yet, the present method of regulating hyperthermia temperature involves manually adjusting the magnetic field intensity, adding to the complexity and difficulty of clinical applications. This study seeks to design novel magnetic carbon nanotubes capable of self-temperature regulation, and investigate their drug loading and release characteristics.

METHODS

Using the co-precipitation method, we synthesized magnetic carbon nanotubes with a Curie temperature of 43 °C. A comprehensive investigation was conducted to analyze their morphology, crystal structure, and magnetic characteristics. To enhance their functionality, chitosan and sodium alginate modifications were introduced, enabling the loading of the antitumor drug doxorubicin hydrochloride (DOX) into these magnetic carbon nanotubes. Subsequently, the loading and release properties of DOX were investigated within the modified magnetic nanotubes.

RESULTS

Under alternating magnetic field, magnetic carbon nanotubes exhibit self-regulating properties by undergoing a magnetic phase transition, maintaining temperatures around 43 °C as required for hyperthermia. On the other hand, during magnetic induction heating, the release percentage of DOX reached 23.5% within 2 h and 71.7% within 70 h at tumor pH conditions, indicating their potential for sustained drug release.

CONCLUSIONS

The prepared magnetic carbon nanotubes can effectively regulate the temperature during hyperthermia treatment while ensuring controlled drug release, which presents a promising method for preparing nanomaterials that synergistically enhance magnetic hyperthermia and chemotherapy drugs.

Labile Fe(III) phase mediates the electron transfer from Fe(II,III) (oxyhydr)oxides to carbon tetrachloride

Labile Fe(III) phase (includes Fe(III)aq, Fe(III)ads, or Fe(III)s species) is an important intermediate during the interaction between Fe(II) and Fe(III) (oxyhydr)oxides, but how does labile Fe(III) influence the electron transfer from Fe(II) to oxidant environmental pollutant during this Fe(II)-Fe(III) interaction is unclear. In this work, the dynamic change of Fe(II,III) (oxyhydr)oxides at the same time scale is simulated by synthesizing Fe(III)-Fe(II)-I (Fe(III)+NaOH+Fe(II)+NaOH) with different Fe(II)/Fe(III) ratios. CCl4 is used as a convenient probe to test the reduction kinetics of mixed valence Fe(II,III)(oxyhydr)oxides with different Fe(II):Fe(III) ratios. The Mössbauer spectra results reveal the Fe(III)labile in the solid phase is in octahedral coordination. The electron-donating capability of Fe(II) was improved with increasing Fe(III) content, but suppressed when [Fe(III)] ≥ 30 mM. The reductive dechlorination of CT by Fe(III)-Fe(II)-I decreased gradually with the increase of Fe(III) content, because more amount Fe(III)labile in solid phase is accumulated. This shows that the electron transfer from Fe(II) to Fe(III)labile rather than to CT is enhanced with increasing Fe(III) content. FTIR data shows that the hydroxylation of Fe(II) with Fe(OH)3 occurs preferentially in the non-hydrogen bonded hydroxyl group, causing the decrease of its reductive reactivity. The presence of [Fe(III)-O-Fe(II)]+ in Fe(III)-Fe(II)-I can stabilize the dichlorocarbene anion (:CCl2-), favouring the conversion of CT to CH4 (13.1%). The aging experiment shows that Fe(III)labile surface may maintain the reductive reactivity of Fe(II) during aging when [Fe(III)] = 5-20 mM. This study deepens our understanding of the mass transfer pathway of iron oxyhydroxides induced by Fe(II) and its impact on the reductive dechlorination of CT.

Magnetic layered double hydroxides with carbamazepine for breast cancer treatment

Current cancer chemotherapy is associated with many side effects and, in some cases, drug resistance, which makes the search for new active molecules and drug delivery strategies imperative. Carbamazepine is an antiepileptic compound that has shown efficacy against breast cancer cell lines. In this study, it was incorporated into layered double hydroxide nanoclays, the percentage of drug loading was increased compared to previous research, and the clays were impregnated with magnetic Fe3O4 nanoparticles. The goal of the magnetic Fe3O4-impregnation was to direct the nanocomposites to the therapeutic target with an external magnetic field. The nanoclay-carbamazepine composites had a carbamazepine loading of 51 %, and the nanoclay-carbamazepine-nanoparticles had a drug loading of 13 % due to the addition of more ingredients. The structure of the composites was analyzed by X-ray diffraction and Scherrer equation, showing a layered double hydroxide organization with crystal sizes of 9-15 nm; from transmission electron microscopy, the final compounds showed a particle size of 97-158 nm, small enough for systemic circulation. In vibrating sample magnetization studies, the composites showed a superparamagnetic behavior with high magnetic saturation (9-17 emu/gr), which should allow a good material attraction by an external magnetic field located near the tumor. In vitro drug release studies were done in Franz cells and measured by UV/Vis spectrophotometry; they showed that carbamazepine release from the nanocomposites responds to the media pH: a good drug release at the lysosome pH and slow release at the blood pH. Finally, the efficacy was tested in vitro in MDA-MB-231 breast cancer cells, and the composites showed an enhanced efficacy in comparison with that produced by the free drug (96 % and 62 % of cell inhibition respectively). Carbamazepine administered with magnetic clays as a carrier is a promising treatment for breast cancer, and further studies should be done to measure the arrival time and the efficacy in vivo.

E. coli Cell Lysis Induced by Lys394 Enzyme Assisted by Magnetic Nanoparticles Exposed to Non-Heating Low-Frequency Magnetic Field

The spreading of microbial pathogens with more and more resistance to traditional low-molecular antibiotic agents demands new approaches to antibacterial therapy. The employment of bacteriophage enzymes capable of breaking bacterial cell walls has attracted much interest within this context. The specific features of the morphology of Gram-negative bacteria prevent the effective direct usage of lytic enzymes and require assistance from additional helpers to facilitate cell lysis. The current work is devoted to the study of boosting the lysis of Escherichia coli (E. coli) JM 109 and MH 1 strains induced by Lys394 bacteriophage endolysin by means of rod-like (56 × 13 nm) magnetic nanoparticles (MNPs) activated by a non-heating low-frequency magnetic field (LF MF) with a frequency of 50 Hz and a flux density of 68.5 mT in a pulse-pause mode (1 s on and 0.3 s off). According to theoretical assumptions, the mechanism of MNP assistance is presumably based upon the disordering of the outer membrane that facilitates enzyme permeation into peptidoglycans to its substrate. It is found that the effect of the LF MF reaches an almost a twofold acceleration of the enzyme reaction, resulting in almost 80 and 70%, respectively, of lysed E. coli JM 109 and MH 1 cells in 21 min. An increase in the membrane permeability was proven by two independent experiments employing β-lactamase periplasmic enzyme leakage and Nile Red (NR) hydrophobic dye fluorescence. It is shown that the outer membrane disordering of E. coli caused by exposure to LF MF nanoparticle movement leads to almost complete (more than 80%) β-lactamase release out of the cells' periplasm to the buffer suspension. Experiments with NR (displaying fluorescence in a non-polar medium only) reveal a drastic reduction in NR fluorescence intensity, reaching a change of an order of magnitude when exposed to LF MF. The data obtained provide evidence of changes in the bacterial cell wall structure. The result shown open up the prospects of non-heating LF MF application in enhancing enzyme activity against Gram-negative pathogens.

Microwave-Assisted Solvothermal Synthesis of Nanocrystallite-Derived Magnetite Spheres

The synthesis of magnetic particles triggers the interest of many scientists due to their relevant properties and wide range of applications in the catalysis, nanomedicine, biosensing and magnetic separation fields. A fast synthesis of iron oxide magnetic particles using an eco-friendly and facile microwave-assisted solvothermal method is presented in this study. Submicron Fe₃O₄ spheres were prepared using FeCl₃ as an iron source, ethylene glycol as a solvent and reductor and sodium acetate as a precipitating and nucleating agent. The influence of the presence of polyethylene glycol as an additional reductor and heat absorbent was also evaluated. We reduce the synthesis time to 1 min by increasing the reaction temperature using the microwave-assisted solvothermal synthesis method under pressure or by adding PEG at lower temperatures. The obtained magnetite spheres are 200–300 nm in size and are composed of 10–30 nm sized crystallites. The synthesized particles were investigated using the XRD, TGA, pulsed-field magnetometry, Raman and FTIR methods. It was determined that adding PEG results in spheres with mixed magnetite and maghemite compositions, and the synthesis time increases the size of the crystallites. The presented results provide insights into the microwave-assisted solvothermal synthesis method and ensure a fast route to obtaining spherical magnetic particles composed of different sized nanocrystallites.

Facile synthesis of superparamagnetic thiamine/Fe3O4 with enhanced adsorptivity toward divalent copper ions

The development of environmentally friendly adsorbents has been extensively carried out to overcome the detrimental effects of heavy metal accumulation, which has persistently become a global ecological problem. In pursuit of generating eco-friendly adsorbents, a green method for synthesizing thiamine functionalized-Fe₃O₄ (FT) was developed in this study. A one-step chemical oxidation and functionalization technique was used to prepare FT using the ammonia-containing solvent. A molar ratio of ammonia:Fe:thiamine of 15:1:1 was shown to produce FT15 with high yield, adsorptivity, and purity. XRD, XPS, FTIR, SEM, and SQUID characterization of FT15 revealed the formation of superparamagnetic thiamine functionalized Fe₃O₄ in their particles. This superparamagneticity facilitates the easy recovery of FT15 particles from the waste-containing solution by using an external magnetic force. The batch adsorption of Cu(II) onto FT15 showed the best fit with the Sips adsorption isotherm model with a maximum adsorption capacity of 426.076 mg g^-1, which is 5.69-fold higher capacity than the control unmodified Fe₃O₄ (F15). After five adsorption-desorption cycles, the FT15 can maintain up to 1.95-fold higher capacity than the freshly synthesized F15. Observation on the physicochemical properties of the post-adsorption materials showed the contribution of an amine group, pyrimidine ring, and the thiazolium group of thiamine in boosting its adsorption capacity. This study provides important findings to advance the adsorptivity of magnetic adsorbents with promising recoverability from aqueous solution by employing naturally available and environmentally friendly compounds such as thiamine.

Structural elucidation of hexavalent Cr adsorbed on surfaces and bulks of Fe3O4 and α-FeOOH

Magnetite (Fe3O4) and goethite (α-FeOOH) were synthesized via a hydrothermal approach and utilized as adsorbents for Cr6+ removal in an aqueous medium. Cr3+ could migrate into bulk Fe3O4 and stabilize in form of a solid solution.

Formulation of Iron Oxide and Oxy-hydroxide Nanoparticles from Ilmenite Sand through a Low-Temperature Process

In our previous publication, we published a simple, low-cost, and environmentally friendly process for the breaking down of the ilmenite lattice using rotary autoclaving, separation of titanium and iron components, and the conversion of the titanium component to amorphous TiO₂ and phase-specific titanium dioxide nanorods. Here, the separated iron component was converted into iron oxide (magnetite and hematite) and iron oxy-hydroxide (akaganeite, β-FeOOH) nanoparticles. The process flow diagram is presented to explain the steps involved. The materials synthesized are fully characterized by X-ray diffractogram (XRD), scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDAX), and Fourier transform infrared (FT-IR), and it is shown that they contain 100% pure iron oxide and iron oxy-hydroxide nanoparticles without any detectable impurities. All of the chemical reactions involved in this process, which contribute to the mechanism of the process, are given. So far, such a low-cost, environmentally friendly, and low-temperature process has not been documented, and the process can be scaled-up for mass production of these nanomaterials used in various technological applications.

Fabrication of monodisperse magnetic nanorods for improving hyperthermia efficacy

Background

Hyperthermia is one of the promising cancer treatment strategies enabled by local heating with the use of tumor-targeting magnetic nanoparticles (MNP) under a non-invasive magnetic field. However, one of the remaining challenges is how to achieve therapeutic levels of heat (without causing damages to regular tissues) in tumors that cannot be effectively treated with anti-tumor drug delivery.

Results

In this work, we report a facile method to fabricate magnetic nanorods for hyperthermia by one-step wet chemistry synthesis using 3-Aminopropyltrimethoxysilane (APTMS) as the shape-controlling agent and ferric and ferrous ions as precursors. By adjusting the concentration of APTMS, hydrothermal reaction time, ratios of ferric to ferrous ions, magnetic nanorods with aspect ratios ranging from 4.4 to 7.6 have been produced. At the clinically recommended field strength of 300 Oe (or less) and the frequency of 184 kHz, the specific absorption rate (SAR) of these nanorods is approximately 50 % higher than that of commercial Bionized NanoFerrite particles.

Conclusions

This increase in SAR, especially at low field strengths, is crucial for treating deep tumors, such as pancreatic and rectal cancers, by avoiding the generation of harmful eddy current heating in normal tissues.

Fe2+: Fe3+ Molar Ratio Influences the Immunomodulatory Properties of Maghemite (γ-Fe2O3) Nanoparticles in an Atopic Dermatitis Model

Here, we report the different antioxidant and physiological effects of maghemite nanoparticles (γ-Fe2O3 NPs) obtained using various Fe2+: Fe3+ molar ratios (FM1 = 1: 1, FM2 = 1: 2, and FM3 = 2: 3) via coprecipitation from ferrous/ferric salts. We investigated the physical, optical, and antioxidant properties of FM1, FM2, and FM3 nanoparticles by conducting UV, Raman, FTIR, and EDX spectroscopic analyses along with DPPH radical scavenging activity. Results showed the highest DPPH scavenging activity in the FM2 group (50.76%), while the activity in the FM1 and FM3 groups was 23.60% and 34.63%, respectively. In addition, topical application of nanoparticles induced significant but different anti-inflammatory and immunomodulatory effects in Dermatophagoides farinae extract/2,4-dinitrochlorobenzene (DFE/DNCB)-sensitized BALB/c mice. The FM2 treatment alleviates more effectively the DFE/DNCB-induced atopic dermatitis-like (AD-like) symptoms in mouse ears (edema, excoriation, scaling, and hemorrhage). In comparison with the DFE/DNCB-sensitized mice, FM2 treatment greatly reduced the size and weight of the spleen and the lymph nodes. It also suppressed mast cell infiltration (2-fold) and reduced dermal and epidermal thickness in mice. In addition, FM2 treatment exhibited better inhibition of the mRNA levels of Th1 (IFN-γ and TNF-α) and Th2 cytokines (IL-4, IL-5, IL-6, IL-10, IL-13, and IL-31), as well as the levels of various inflammation-related proteins (COX-2, iNOS, and TNF-α). Moreover, we demonstrated that an increasing proportion of Fe3+ in Fe2+: Fe3+ enhances the antioxidant activity and increases the anti-inflammatory and immunomodulatory effects of γ-Fe2O3 NPs in an AD mouse model. Thus, γ-Fe2O3 NPs could be used in the formulation of nonsteroidal drugs for AD treatment.

Self-standing magnetic composite nanosheets prepared in the presence of an external magnetic field: Characterization and potential for medical applications

The aim of this study is to develop self-standing, ultrathin film, nanosheets with high magnetic response for use in a medical device that can be migrated to a target location in the body by using an external magnetic field. First, iron oxide nanoparticles are synthesized by either the sol-gel method or thermal decomposition. The resulting magnetic properties of the nanoparticles show that the thermal decomposition method provides a greater saturation magnetization value than the sol-gel method. Next, the nanoparticles obtained by the thermal decomposition method are embedded into nanosheets of poly(L-lactide) at varying concentrations. Embedding of the nanoparticles in the composite nanosheets is achieved by the application of an external magnetic field. The composite nanosheets are then characterized. The thickness of the nanosheet increases, and the nanoparticles are well dispersed, with an increase in poly (L-lactide) concentration. The NP-embedded nanosheets are imaged by transmission electron microscopy, which reveals thin, long aggregates aligned in collinear line features. X-ray diffraction results indicate that the magnetic hard axis of the nanoparticles in the nanosheets is aligned in parallel to the plane of the nanosheet by magnetic field application during nanosheet preparation. In addition, the nanosheets at high poly (L-lactide) concentrations that had been subjected to a magnetic field during preparation show a slightly greater magnetic response compared with both nanosheets without magnetic field exposure and nanosheets prepared at low poly (L-lactide) concentrations.

High Yield Synthesis and Application of Magnetite Nanoparticles (Fe3O4)

Magnetite nanoparticles (Fe3O4), average particle size of 12.9 nm, were synthesized de novo from ferrous and ferric iron salt solutions (total iron salt concentration of 3.8 mM) using steady-state headspace NH3(g), 3.3% v/v, at room temperature and pressure, without mechanical agitation, resulting in >99.9% yield. Nanoparticles size distributions were based on enumeration of TEM images and chemical compositions analyzed by: XRD, EDXRF, and FT-IR; super-paramagnetic properties were analyzed by magnetization saturation (74 emu/g). Studies included varying headspace [NH3(g)] (1.6, 3.3, 8.4% v/v), and total iron concentrations (1.0 mM, 3.8 mM, 10.0 mM, and >>10 mM). An application of the unmodified synthesized magnetite nanoparticles included analyses of tetracycline’s (50, 100, 200, 300, and 400 ppb) in aqueous, which was compared to the same tetracycline concentrations prepared in aqueous synthesis suspension with >97% extraction, analyzed with LC-MS/MS.

Hydrothermal synthesizing sludge-based magnetite catalyst from ferric sludge and biosolids: Formation mechanism and catalytic performance

Sludge-based magnetite catalyst (SBMC) containing Fe₃O₄ was synthesized by hydrothermal (HT) of biosolids and ferric sludge, which is a promising wasted sludge recycling way. The protein and carbohydrate, main representative compounds in biosolids, were used to explore the SBMC formation mechanism. A part of carbohydrate and the produced Maillard reaction products (MRPs) derived from two substrates via Maillard reaction (MR) were confirmed to participate in Fe³⁺ reduction. The MR accompanied by substrates humification, making MRPs own strong chelation activity. The MRPs (50-100 kDa) reflected the strongest relative reducing and chelation activity, mainly involving in Fe₃O₄ synthesis. Furthermore, the SBMC was verified as an efficient Fenton-like catalyst for aniline with 77.9% removal efficiency. The OH and O₂^- both contributed to the degradation, differing from only OH playing function in traditional Fenton-like system, implying biochar in SBMC could mediate the reactive oxygen species generating by Fe₃O₄, and benefit its catalytic performance.

Green synthesis and optimization of nano-magnetite using Persicaria bistorta root extract and its application for rosewater distillation wastewater treatment

The aim of this research is to synthesize magnetite nanoparticles, using Persicaria bistorta root extract as the reducing agent, and to test its adsorption properties in the treatment of rosewater distillation wastewater. Taking advantage of Taguchi method, effect of synthesis parameters, including molar concentration of FeCl₂, concentration of plant extract, temperature, and pH on crystallite size and magnetization strength is studied. Based on the successful synthesis of magnetite nanoparticles and characterization experiments, Persicaria bistorta root extract can be considered as a proper alternative as the reducing agent. Data analysis shows that crystallite size and magnetization are positively correlated with concentration of FeCl₂ and pH, while inversely related to temperature and independent of plant extract concentration. The optimum values achieved for concentration of FeCl₂, temperature, and pH are 0.15 M, 70 °C, and 11, respectively, with the production of nanoparticles with magnetite size of 45.5 nm and magnetization value of 62.5 emu/g. In addition, the application of as-synthesized magnetite nanoparticles as an adsorbent for treatment of rosewater distillation wastewater proved its high adsorption capacity for chemical oxygen demand (COD) up to 149 mg/g. Adsorption data also shows a good fitness with Langmuir and Freundlich isotherm models.

A Hybrid System for Magnetic Hyperthermia and Drug Delivery: SPION Functionalized by Curcumin Conjugate

Cancer is among the leading causes of death worldwide, thus there is a constant demand for new solutions, which may increase the effectiveness of anti-cancer therapies. We have designed and successfully obtained a novel, bifunctional, hybrid system composed of colloidally stabilized superparamagnetic iron oxide nanoparticles (SPION) and curcumin containing water-soluble conjugate with potential application in anticancer hyperthermia and as nanocarriers of curcumin. The obtained nanoparticulate system was thoroughly studied in respect to the size, morphology, surface charge, magnetic properties as well as some biological functions. The results revealed that the obtained nanoparticles, ca. 50 nm in diameter, were the agglomerates of primary particles with the magnetic, iron oxide cores of ca. 13 nm, separated by a thin layer of the applied cationic derivative of chitosan. These agglomerates were further coated with a thin layer of the sodium alginate conjugate of curcumin and the presence of both polymers was confirmed using thermogravimetry. The system was also proven to be applicable in magnetic hyperthermia induced by the oscillating magnetic field. A high specific absorption rate (SAR) of 280 [W/g] was registered. The nanoparticles were shown to be effectively uptaken by model cells. They were found also to be nontoxic in the therapeutically relevant concentration in in vitro studies. The obtained results indicate the high application potential of the new hybrid system in combination of magnetic hyperthermia with delivery of curcumin active agent.

Synthesis and characterization of a magnetic adsorbent from negatively-valued iron mud for methylene blue adsorption

With increasing awareness of reduction of energy and CO₂ footprint, more waste is considered recyclable for generating value-added products. Here we reported the negatively-valued iron mud, a waste from groundwater treatment plant, was successfully converted into magnetic adsorbent. Comparing with the conventional calcination method under the high temperature and pressure, the synthesis of the magnetic particles (MPs) by Fe²⁺/Fe³⁺ coprecipitation was conducted at environment-friendly condition using ascorbic acid (H₂A) as reduction reagent and nitric acid (or acid wastewater) as leaching solution. The MPs with major component of Fe₃O₄ were synthesized at the molar ratio (called ratio subsequently) of H₂A to Fe³⁺ of iron mud ≥ 0.1; while amorphous ferrihydrite phase was formed at the ratio ≤ 0.05, which were confirmed by vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). With the ratio increased, the crystalline size and the crystallization degree of MPs increased, and thus the Brunauer-Emmett-Teller (BET) surface and the cation-exchange capacity (CEC) decreased. MPs-3 prepared with H₂A to Fe³⁺ ratio of 0.1 demonstrated the highest methylene blue (MB) adsorption of 87.3 mg/g and good magnetic response. The adsorption of MB onto MPs agreed well with the non-linear Langmuir isotherm model and the pseudo-second-order model. Pilot-scale experiment showed that 99% of MB was removed by adding 10 g/L of MPs-3. After five adsorption-desorption cycles, MPs-3 still showed 62% removal efficiency for MB adsorption. When nitric acid was replaced by acid wastewater from a propylene plant, the synthesized MPs-3w showed 3.7 emu/g of saturation magnetization (Ms) and 56.7 mg/g of MB adsorption capacity, 2.8 times of the widely used commercial adsorbent of granular active carbon (GAC). The major mechanism of MPs adsorption for MB was electrostatic attraction and cation exchange. This study synthesized a magnetic adsorbent from the negatively-valued iron mud waste by using an environment-friendly coprecipitation method, which had a potential for treatment of dye wastewater.

Soybean peroxidase immobilized onto silica-coated superparamagnetic iron oxide nanoparticles: Effect of silica layer on the enzymatic activity

Peroxidase immobilization onto magnetic supports is considered an innovative strategy for the development of technologies that involves enzymes in wastewater treatment. In this work, magnetic biocatalysts were prepared by immobilization of soybean peroxidase (SBP) onto different silica-coated superparamagnetic iron oxide nanoparticles. The obtained magnetic biocatalysts were tested for the degradation of malachite green (MG), a pollutant often found in industrial wastewaters and with significant drawbacks for the human and environmental health. A deep physicochemical characterization of the materials was performed by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), High Resolution-Transmission Electron Microscope (HR-TEM) and magnetization measurements among others techniques. Results showed high immobilization yield of SBP onto nanomaterials with excellent properties for magnetic recoverability. A partial loss of activity with respect to free SBP was observed, compatible with the modification of the conformational structure of the enzyme after immobilization. The structural modification depended on the amount (and thickness) of silica present in the hybrid materials and the activity yield of 43% was obtained for the best biocatalyst. Thermal stability and reusability capacity were also evaluated.

Ultrafine ferroferric oxide nanoparticles embedded into mesoporous carbon nanotubes for lithium ion batteries

An effective one-pot hydrothermal method for in situ filling of multi-wall carbon nanotubes (CNT, diameter of 20–40 nm, length of 30–100 μm) with ultrafine ferroferric oxide (Fe₃O₄) nanoparticles (8–10 nm) has been demonstrated. The synthesized Fe₃O₄@CNT exhibited a mesoporous texture with a specific surface area of 109.4 m² g⁻¹. The loading of CNT, in terms of the weight ratio of Fe₃O₄ nanoparticles, can reach as high as 66.5 wt%. Compared to the conventional method of using a Al₂O₃ membrane as template to fill CNT with iron oxides nanoparticles, our strategy is facile, effective, low cost and easy to scale up to large scale production (~1.42 g per one-pot). When evaluated for lithium storage at 1.0 C (1 C = 928 mA g⁻¹), the mesoporous Fe₃O₄@CNT can retain at 358.9 mAh g⁻¹ after 60 cycles. Even when cycled at high rate of 20 C, high capacity of 275.2 mAh g⁻¹ could still be achieved. At high rate (10 C) and long life cycling (500 cycles), the cells still exhibit a good capacity of 137.5 mAhg⁻¹.

Ternary Spinel MCo2O4 (M = Mn, Fe, Ni, and Zn) Porous Nanorods as Bifunctional Cathode Materials for Lithium-O2 Batteries

The development of Li-O2 battery electrocatalysts has been extensively explored recently. The Co3O4 oxide has attracted much attention because of its bifunctional activity and high abundance. In the present study, toxic Co(2+) has been replaced through the substitution on the tetrahedral spinel A site ions with environmental friendly metals (Mn(2+), Fe(2+), Ni(2+), and Zn(2+)), and porous nanorod structure are formed. Among these spinel MCo2O4 cathodes, the FeCo2O4 surface has the highest Co(3+) ratio. Thus, oxygen can be easily adsorbed onto the active sites. In addition, Fe(2+) in the tetrahedral site can easily release electrons to reduce oxygen and oxidize to half electron filled Fe(3+). The FeCo2O4 cathode exhibits the highest discharging plateau and lowest charging plateau as shown by the charge-discharge profile. Moreover, the porous FeCo2O4 nanorods can also facilitate achieving high capacity and good cycling performance, which are beneficial for O2 diffusion channels and Li2O2 formation/decomposition pathways.

Sonochemical synthesis of iron oxide nanoparticles loaded with folate and cisplatin: effect of ultrasonic frequency

Simple preparative methods were used to sonosynthesize different magnetic iron oxide nanoparticles (FeNPs) via co-precipitation of aqueous solutions of ferrous salts in a basic aqueous solution of ethylene glycol (EG). Sonosynthesis was achieved using different frequencies of ultrasound: 581, 861, and 1141 kHz under the same acoustic power. The hydroxyl radicals generated by cavitational collapse, induced by the ultrasonic field, led to the oxidation of Fe(2+) to Fe(3+). The rate of sonochemical Fe(3+) production decreased linearly with the frequency. Three different systems of FeNPs were synthesized, all with the same core but a different shell: FeNPs capped with EG (EG/FeNPs), FeNPs capped with EG and folate (Fol/EG/FeNPs), and FeNPs capped with EG, folate and cisplatin (Pt/EG/FeNPs). The nanoparticles were characterized by transmission electron microscopy, fluorescence and Raman microspectroscopy, total-reflection X-ray fluorescence, and elemental analysis (C, N, and H). The magnetization hysteresis loops of these samples were also measured. The obtained values of saturation magnetization were within the interval between 60 and 93 Am(2)kg(-1). From the analysis of these results, it was found that the ultrasonic frequency did not affect the nanoparticle size (diameter of 21-31 nm). In contrast, the frequency affected the amount of drug loaded, as cisplatin loading increased proportionately with ultrasound frequency.

CNTs in situ attached to α-Fe2O3 submicron spheres for enhancing lithium storage capacity

In this work, we developed a facile hydrothermal method for synthesis of hybrid α-Fe2O3-carbon nanotubes (CNTs) architectures (α-Fe2O3-CNTs-1 and α-Fe2O3-CNTs-2). The CNTs are in situ attached to the α-Fe2O3 submicron spheres and form three-dimensional network robust architectures. The increase in the amount of CNTs in the network α-Fe2O3-CNTs architectures will significantly enhance the cycling and rate performance, as the flexible and robust CNTs could ensure the fast electron transport pathways, enhance the electronic conductivity, and improve the structural stability of the electrode. As for pure α-Fe2O3 submicron spheres, the capacity decreased significantly and retained at 377.4 mAh g(-1) after 11 cycles, and the capacity has a slightly increasing trend at the following cycling. In contrast, the network α-Fe2O3-CNTs-2 electrode shows the most remarkable performance. At the 60th cycle, the capacity of network α-Fe2O3-CNTs-2 (764.5 mAh g(-1)) is 1.78 times than that of α-Fe2O3 submicron spheres (428.3 mAh g(-1)). The long-term cycling performance (1000 cycles) of samples at a high current density of 5 C showed that the capacity of α-Fe2O3 submicron spheres fade to ∼37.3 mAh g(-1) at the 400th cycle and gradually increased to ∼116.7 mAh g(-1) at the 1000th cycle. The capacity of network α-Fe2O3-CNTs-2 maintained at ∼220.2 mAh g(-1) before the 400th cycle, arrived at ∼326.5 mAh g(-1) in the 615th, cycle and retained this value until 1000th cycle. The network α-Fe2O3-CNTs-2 composite could significantly enhance the cycling and rate performance than pure α-Fe2O3 submicron spheres composite.

Arsenite removal from aqueous solution by a microbial fuel cell-zerovalent iron hybrid process

Conventional zerovalent iron (ZVI) technology has low arsenic removal efficiency because of the slow ZVI corrosion rate. In this study, microbial fuel cell (MFC)-zerovalent iron (MFC-ZVI) hybrid process has been constructed and used to remove arsenite (As(III)) from aqueous solutions. Our results indicate that the ZVI corrosion directly utilizes the low-voltage electricity generated by MFC in the hybrid process and both the ZVI corrosion rate and arsenic removal efficiency are therefore substantially increased. The resultant water qualities are compliant with the recommended standards of EPA and WHO. Compared to the ZVI process alone, the H2O2 generation rate and output are dramatically improved in MFC-ZVI hybrid process. Strong oxidants derived from H2O2 can rapidly oxidize As(III) into arsenate (As(V)), which helps to improve the As(III) removal efficiency. The distribution analysis of As and Fe indicates that the As/Fe molar ratio of the flocs in solution is much higher in the MFC-ZVI hybrid process. This phenomenon results from the different arsenic species and hydrous ferric oxides species in these two processes. In addition, the electrosorption effect in the MFC-ZVI hybrid process also contributed to the arsenic removal by concentrating As(V) in the vicinity of the iron electrode.

Removal of arsenic(V) from spent ion exchange brine using a new class of starch-bridged magnetite nanoparticles

Ion exchange (IX) is considered by US EPA as one of the best available technologies for removing arsenic from drinking water. However, typical IX processes will generate large volumes of arsenic-laden regenerant brine that requires costly further handling and disposal. This study aimed to develop an engineered strategy to minimize the production and arsenic leachability of the process waste residual. We prepared and tested a new class of starch-bridged magnetite nanoparticles for removal of arsenate from spent IX brine. A low-cost, "green" starch at 0.049% (w/w) was used as a stabilizer to prevent the nanoparticles from agglomerating and as a bridging agent allowing the nanoparticles to flocculate and precipitate while maintaining their high arsenic sorption capacity. When applied to a simulated spent IX brine containing 300 mg/L As and 6% (w/w) NaCl, nearly 100% removal of arsenic was achieved within 1 h using the starch-bridged nanoparticles at an Fe-to-As molar ratio of 7.6, compared to only 20% removal when bare magnetite particles were used. Increasing NaCl in the brine from 0 to 10% (w/w) had little effect on the arsenic sorption capacity. Maximum uptake was observed within a pH range of 4-6. The Langmuir capacity coefficient was determined to be 248 mg/g at pH 5.0. The final treatment sludge was able to pass the TCLP (Toxicity Characteristic Leaching Procedure) based leachability of 5 mg/L as As.