MnFe2O4 Magnetic Nanoparticles Research Articles

Synthesis and characterization of monophasic MnFe2O4 nanoparticles for potential application in magnetic hyperthermia

Nanostructured materials are being used in a wide range of technological applications. In biomedical applications, magnetic hyperthermia (MH) is a therapeutic modality for the treatment of solid tumors. The materials needed for MH face challenges such as size homogeneity, reasonable temperature increase and biocompatibility. In this work, MnFe2O4 magnetic nanoparticles (Nps) were synthesized by a simple method using the bio-polymer chitosan. Samples with several particles sizes were obtained by treatments at the temperatures of 300, 400, 500 and 600 °C. The particle sizes ranged from 7.8 to 13.3 nm. At 300 K, the saturation magnetization of the Nps varied from 16.2 to 35.8 emu/g. The Mössbauer spectra at low temperatures showed the presence of monophasic MnFe2O4. For all samples, the Mössbauer results at 300 K suggest that the samples are in the superparamagnetic regime. The measurements to obtain the Specific Loss Power (SLP) were conducted at a frequency of 74 kHz and AC field amplitude of 247 Oe. The sample thermally treated at 600 °C and the dispersion prepared with a concentration of 1.0 mg/mL showed the highest SLP of 129.1 W/g.

Field-induced magnetorheological study towards the active magneto-viscoelastic behavior of stable MnFe2O4 magnetic nanofluid

This work presents the fine-tuned synthesis of MnFe2O4 oleic acid-coated magnetic nanoparticles (MNPs) by the chemical co-precipitation method. The X-ray photoelectron spectroscopy (XPS) was utilized to investigate the elemental composition and oxidation state of oleic acid-coated MnFe2O4 MNPs. The Fourier transform infrared spectroscopy (FTIR) spectra were used to confirm the functional groups in the oleic acid-coated MnFe2O4 magnetic nanoparticles. The spherical shape of MnFe2O4 MNPs is confirmed by Field emission scanning electron microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM) techniques. Zeta potential (ζ) measurements were performed to confirm the stability of MnFe2O4 magnetic nanofluid (MNF). Magnetic measurements (M−vs−H) reveal the saturation magnetization, Ms = 20.3 emu/g and coercivity, HC = 30 Oe, confirming the single domain superparamagnetic nature at 300 K. Field-induced shear thinning behavior of the MnFe2O4 magnetic fluid is confirmed by a power law, η = c γn + n∞ and steady-state behavior measurements. Magneto viscous effect initially increased at a low shear rate of 20 s−1 and then decreased at a higher shear rate of 100 s−1, which confirms the stability of the MnFe2O4 magnetic fluid. Also, the highest deflection angle, θ = 243 m.rad of MnFe2O4 magnetic fluid was observed at a moderate shear rate 100 s−1 and a high magnetic field of 1.2 T, while the lowest value of deflection angle, θ = 65 m.rad was observed in the absence of magnetic field. In contrast, the storage modulus (G') is greater than the loss modulus (G''), in corroboration with the viscoelastic-to-viscous behavior of MnFe2O4 magnetic fluid.

Magnetization and ZIF-67 modification of Aspergillus flavus biomass for tetracycline removal from aqueous solutions: A stable and efficient composite

In the present work, the biomass of Aspergillus flavus (AF) was modified using magnetic nanoparticles MnFe2O4 and metal-organic framework of ZIF-67, and its ability to remove tetracycline antibiotic (TCH) was investigated. With the help of physicochemical tests, AF biomass modification with ZIF-67 and MnFe2O4 magnetic nanoparticles was confirmed. Based on the BET value, AF-MnFe2O4-ZIF-67 (139.83 m2/g) has a higher surface value than AF (0.786 m2/g) and AF/MnFe2O4 (17.504 m2/g). Also, the magnetic saturation value revealed that the modified biomass can be isolated from the treated solution using a simple magnetic field. Maximum TCH elimination (99.04%) using AF-MnFe2O4-ZIF-67 was obtained at pH 7, adsorber mass of 1 g/L, adsorption time of 40 min, and TCH content of 10 mg/L. The thermodynamic study indicated that the TCH abatement using the desired composite is spontaneous and exothermic. The experimental results showed that the adsorption process is compatible with the pseudo-second-order kinetic and Freundlich model. The maximum adsorption capacity for AF, AF-MnFe2O4, and AF-MnFe2O4-ZIF-67 was quantified to be 9.75 mg/g, 25.59 mg/g, and 43.87 mg/g, respectively. The reusability of the desired adsorbers was examined in up to 8 steps. The outcomes showed that the adsorbers can be used several times in TCH elimination. The provided composite can remove TCH from hospital wastewater, so it can be suggested for use in water and wastewater treatment works.

Remotely triggered curcumin release from stimuli‐responsive magneto‐polymericlayer‐by‐layerengineered nanoplatforms

AbstractCurcumin is a promising natural drug in cancer therapy. However, its therapeutic applicability is limited by its low solubility, short half‐life, and low bioavailability. In this work curcumin is encapsulated in stimuli‐responsive magneto‐polymeric nanoplatforms aiming at improving its bioavailability and efficiency for delivery in biological media. MnFe2O4magnetic nanoparticles (MNPs) were synthesized via thermal decomposition, coated with sodium citrate and then functionalized with multilayers of chitosan and sodium alginate, by means of the layer‐by‐layer deposition technique. A mesoporous polymeric‐magnetic nanoplatform was produced capable of a controlled and sustained release of curcumin under temperature, pH and alternating magnetic field (magnetic hyperthermia) stimuli. As the temperature and pH of the medium increased, an increase in the rate of curcumin release was observed in a two‐stage process, following the Gallagher‐Corrigan mathematical model. The use of magnetic hyperthermia resulted in a faster diffusion‐based release of curcumin. Increasing the number of polymer layers assembled on top of MNPs hinders the release of the curcumin molecules from innermost regions of the multilayers. These results show that magnetic hyperthermia provides a means for the controlled heat‐induced release of curcumin, which can lead to an enhanced therapeutic action for curcumin.

Preparation and Characterization of Chitosan-Coated Manganese-Ferrite Nanoparticles Conjugated with Laccase for Environmental Bioremediation.

Bioremediation with immobilized enzymes has several advantages, such as the enhancement of selectivity, activity, and stability of biocatalysts, as well as enzyme reusability. Laccase has proven to be a good candidate for the removal of a wide range of contaminants. In this study, naked or modified MnFe2O4 magnetic nanoparticles (MNPs) were used as supports for the immobilization of laccase from Trametes versicolor. To increase enzyme loading and stability, MNPs were coated with chitosan both after the MNP synthesis (MNPs-CS) and during their formation (MNPs-CSin situ). SEM analysis showed different sizes for the two coated systems, 20 nm and 10 nm for MNPs-CS and MNPs-CSin situ, respectively. After covalent immobilization of laccase by glutaraldehyde, the MNPs-CSin situ-lac and MNPs-CS-lac systems showed a good resistance to temperature denaturation and storage stability. The most promising system for use in repeated batches was MNPs-CSin situ-lac, which degraded about 80% of diclofenac compared to 70% of the free enzyme. The obtained results demonstrated that the MnFe2O4-CSin situ system could be an excellent candidate for the removal of contaminants.

Fabrication of recoverable magnetic composite material based on graphene oxide for fast removal of lead and cadmium ions from aqueous solution

AbstractBACKGROUNDIn this study, a novel magnetic material was applied as an adsorbent for simultaneous removal of Pb(II) and Cd(II) ions from aqueous solutions. The adsorbent was synthesized using functionalized MnFe2O4 magnetic nanoparticles grafted to lamellar graphene oxide surface (MnFe2O4@SiO2‐NH2@GO) and characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and magnetic measurements.RESULTSThe adsorbent exhibited superior adsorption properties for Pb(II) and Cd(II). The maximum uptake capacity of Pb(II) and Cd(II) reached 42.48 and 18.28 mg g−1 within 30 min at 25 °C, respectively. The data for adsorption fitted well with the Langmuir isotherm and pseudo‐second‐order kinetic models, which indicated that the adsorption was via monolayer chemisorption on homogeneous sites. The calculation of thermodynamic parameters revealed spontaneous and endothermic adsorption processes accompanied by randomness increase. X‐ray photoelectron spectroscopy analysis indicated that the coordination between nitrogen atoms of amino groups and the two types of heavy metal ions was a possible adsorption mechanism.CONCLUSIONSMnFe2O4@SiO2‐NH2@GO possesses the properties of high adsorption efficiency, fast separation, high stability and easy regeneration for adsorption of Pb(II) and Cd(II) ions. Thus, the as‐prepared adsorbent is considered as a promising material for the removal of heavy metal ions and this research could offer a new means for water cleanup. © 2020 Society of Chemical Industry

Ozone catalytic oxidation of biologically pretreated semi-coking wastewater (BPSCW) by spinel-type MnFe2O4 magnetic nanoparticles

• MnFe 2 O 4 magnetic catalysts had excellent ozone catalytic oxidation performance on the real BPSCW. • The effect of operational parameters in practical applications on catalytic ozonation is investigated. • The removal efficiencies of COD and volatile phenol could reach 85.2% and 94.1%, respectively. • MnFe 2 O 4 magnetic catalysts catalyzed O 3 /H 2 O 2 to produce hydroxyl radicals (∙OH). • MnFe 2 O 4 magnetic catalysts were superparamagnetic (67.8 emu∙g −1 ) and reused without high loss of activity. In this study, spinel-type MnFe 2 O 4 magnetic nanoparticles were successfully synthesized employing the purified sol–gel method and used for the advanced treatment of biologically pretreated semi-coking wastewater (BPSCW) by the O 3 /H 2 O 2 catalytic system. Results showed that the MnFe 2 O 4 magnetic catalysts did not have a regular surface morphology, and their surface contained numerous fine particles that showed a particle accumulation state and formed a good nano-spinel structure. Their surface morphology, ratio, size, and X-ray photoelectron spectroscopy revealed two active metal elements in the catalyst, namely, Fe 3+ and Mn 2+ , which were consistent with the elemental composition and valence of MnFe 2 O 4 . Under optimal reaction conditions, the removal efficiency of O 3 /H 2 O 2 /MnFe 2 O 4 catalytic system for chemical oxygen demand (COD) and volatile phenol (VP) can reach 85.2% and 94.1%, respectively (catalyst dosage = 2.0 g∙L −1 , O 3 dosage = 1.2 mg∙min −1 , H 2 O 2 concentration = 0.15 mol∙L −1 , pH = 7.0, and treatment time = 70 min). The free radical quenching experiment and electron paramagnetic resonance (EPR) experiment verified that hydroxyl radicals (∙OH) played a role in the deep treatment of BPSCW in the O 3 /H 2 O 2 /MnFe 2 O 4 catalytic system. Phosphate experiments proved that lewis acid sites on the surface of the MnFe 2 O 4 magnetic catalysts were the catalytically active sites. The superparamagnetic properties of the MnFe 2 O 4 magnetic catalysts (67.8 emu∙g −1 ) facilitated magnetic separation from the treated wastewater. After 10 cycles, the activity of the MnFe 2 O 4 magnetic catalysts remained high, and the removal efficiencies of COD and VP only decreased by 13.6% and 11.9%, respectively. Considering excellent degradation performance, easy magnetic separation and high stability, this study provided important insights into the practical application of the O 3 /H 2 O 2 catalytic system for the advanced treatment of BPSCW.

Effective removal of cationic dyes from aqueous solutions using reduced graphene oxide functionalized with manganese ferrite nanoparticles

In this research, we synthesized GO by a Hummer's method and decorated with it MnFe2O4 magnetic nanoparticles that is synthesized by the sol-gel method to remove methylene blue dye as a primary cationic organic dye pollutant model, from wastewaters. Successful removal of MB has been achieved on MnFe2O4/rGO magnetic nanoparticles (MRGO) having a surface area of 95 m2/g at different pH with maximum adsorption capacity 105 mg/g at pH 7.50. The effects of contact time, adsorbent dose, and change in pH were also studied. The kinetics of adsorption model follows the pseudo-second order mechanism.This magnetic facilely separable adsorbent retains 85% of its reactivity on dye removal after the reuse it for four-times.

Size dependent magnetic and capacitive performance of MnFe2O4 magnetic nanoparticles

MnFe2O4 magnetic nanoparticles (MNPs) are prepared by simple chemical oxidation method with optimized experimental conditions. The particle size is reduced by introducing the ferric ions as a size reducing agent during the chemical reaction. The saturation magnetization of the MnFe2O4 MNPs are tuned between 45 and 67 emu/g. The shift in the particle size distribution is confirmed from the transmission electron microscope (TEM) micrograph. The highest specific capacitance of 415 F/g is achieved for the smaller sized MnFe2O4 MNPs prepared with higher concentration of ferric ions. The results suggest that the ferric ions could be used for the size control of ferrites through chemical oxidation method and the sized reduced MnFe2O4 MNPs could be a suitable choice for the electrochemical supercapacitor applications.

Effect of molybdenum doping on the structural and magnetic properties of MnFe2O4 magnetic nanoparticles

Magnetic nanoparticles MnFe2-xMoxO4 (x = 0.00, 0.04, 0.08 and 0.10) have been prepared by wet coprecipitation method at calcination temperature 673 K. X-ray powder diffraction (XRD) was used to study the structural properties of the prepared samples, whereas the vibrating sample magnetometer (VSM) and Mossbauer spectrometry measurements (at T = 300 K and T = 77 K) were used to investigate the magnetic properties. The single-phase cubic spinel structure of the ferrites samples was confirmed by the XRD patterns, and a nonlinear variation in the crystalline size was revealed. VSM hysteresis loops confirmed the ferromagnetic behavior in all the samples with an increase in saturation magnetization with the molybdenum doping. Mossbauer spectra at 300 K showed a mixture of the magnetic sextet and central quadrupole doublet with enhancement in the magnetic sextet in the Mo-doped samples. Moreover, Mossbauer spectra at 77 K revealed the disappearance of the quadrupole doublet in all samples, indicating the enhancement of magnetic properties of manganese ferrites nanoparticles due to Mo-doping.

Facile synthesis, antibacterial mechanisms and cytocompatibility of Ag–MnFe2O4 magnetic nanoparticles

Magnetic MnFe2O4 nanoparticles containing 0, 1 and 3 at.% silver, respectively were synthesized by one-pot sol-gel method for antibacterial applications in biomedical fields. Material characterizations indicate that MnFe2O4 begins crystallization at 134 °C and oxidation at 450 °C, the grain size and agglomeration degree increase with the silver content and silver exists as metallic state for the particles. The saturation magnetization decreases with the sintering temperature and slightly increases with the silver content, with the maximum of 50.0 emu/g obtained. Antibacterial tests by plate counting and PI-Hoechst 33342 staining suggest that the antibacterial activity of Ag–MnFe2O4 nanoparticles is silver content-dependent. Silver ions concentration measurement, β-galactosidase activity assay and transmission electron microscopic observation show that the antibacterial activity is dominated by the actions of the released silver ions, rather than the membrane cell impairment or reactive oxygen species-induced oxidative stress mechanism. MC3T3-E1 cell test demonstrates the best cytocompatibility of the nanoparticles with 3 at.% silver, which is likely related to the reduced cell endocytosis of the aggregated particles. The combination of magnetism, antibacterial activity and biocompatibility would make Ag–MnFe2O4 nanoparticles a potential multi-functional material in various biomedical applications.

MnFe2O4 nanoparticles/cellulose acetate composite nanofiber for controllable release of naproxen

Nanofibers have been demonstrated to be highly effective for drug delivery applications. Although magnetic nanoparticles (MNPs) have been potentially added to nanofibers for improved drug release stimulation, the effect has been limited. In this study, a magnetic nanofiber membrane composed of cellulose acetate (CA), collagen (COL), and MnFe2O4 MNPs was prepared by electrospinning. Naproxen (NAP) drug was deposited on the nanofibers, and the drug release mechanism and effect of the MNPs on the stimulated NAP release were investigated. The electrical conductivity of the dope solution strongly affected the nanofiber characteristics. Moreover, the MTT cytotoxicity assay proved that CA-COL, CA-COL-NAP, and CA-COL-NAP-MNP nanofibers had low toxicity, as the cell viability was >80%. The NAP release mechanism was determined using zero-order, first-order, Higuchi, and Korsmeyer-Peppas kinetics models. According to the dissolution results, for all nanofibers, the NAP release followed the Korsmeyer-Peppas kinetics model, and the transport mechanism was Fickian diffusion. A high MNP concentration and neutral pH condition were conducive to NAP release.

Studies on catalytic activity of MnFe2O4 and CoFe2O4MNPsas mediators in hemoglobin based biosensor

Abstract MnFe2O4 and CoFe2O4 magnetic nanoparticles (MNPs) were synthesized using simple polyol method by refluxing in diethylene glycol. The size of obtained CoFe2O4 MNPs was found to be 4.0 nm and MnFe2O4 MNPs was found to be 7.0 nm with surface area 291.04 M2/g and 165.39 M2/g respectively. These MNPs due to its high surface area and nanosize were used in the hemoglobin based biosensor for the detection of H2O2 as a mediator. The EIS measurements show that the CoFe2O4 MNPs are more conducting than the MnFe2O4 MNPs. The surface area of CoFe2O4 MNPs was found to be higher than the MnFe2O4 MNPs. The GCE/CS/CoFe2O4/Hb modified biosensor shows wider linearity range (1×10-7 to 8×10-4 M) than the GCE/CS/MnFe2O4/Hb modified biosensor (1×10-6 to 4×10-4 M) because of higher conductivity and greater surface area of CoFe2O4 which increases the catalytic activity

MnFe2O4 magnetic nanoparticles modified with chitosan polymeric and phosphotungstic acid as a novel and highly effective green nanocatalyst for regio- and stereoselective synthesis of functionalized oxazolidin-2-ones.

A novel magnetically recoverable acid nanocatalyst, MnFe2O4/chitosan/phosphotungstic acid (MnFe2O4@CS@PTA), was successfully synthesized. The synthesized nanoparticle was studied as the heterogenous nanocatalyst to prepare the functionalized oxazolidin-2-ones as versatile chiral synthons in asymmetrically synthesizing the compounds with biological activity through the reaction of α-epoxyketones with urea and thiourea. This new procedure has notable advantages such as excellent yields, green reaction conditions, and short reaction time. In addition, the excellent catalytic performance in protic solvent and the easy preparation, thermal stability and separation of the catalyst make it a good heterogeneous system and a useful alternative to other heterogeneous catalysts. Perhaps, the synthesized MnFe2O4@CS@PTA is a hopeful catalytic substance for mass fine chemicals production. The structure and composition of the nanocomposite was performed by different methods and analyzed by Infrared Spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FE-SEM), Thermo-Gravimetric Analysis (TGA), X-ray Diffraction (XRD) Transmission Electron Microscopy (TEM), Vibrating Sample Magnetometer (VSM) and Brunauere Emmette Teller (BET).

Impact of manganese ferrite (MnFe2O4) nanoparticles on growth and magnetic character of barley (Hordeum vulgare L.)

The main objective of this study was to assess the uptake and translocation of MnFe2O4 magnetic nanoparticles (MNPs) in hydroponically grown barley (Hordeum vulgare L.). Hydrothermally synthesized and well characterized MNPs (average crystallite size of 14.5 ± 0.5 nm) with varied doses (62.5, 125, 250, 500, and 1000 mg L−1) were subjected to the plants at germination and early growing stages (three weeks). The tissues analyzed by vibrating-sample magnetometer (VSM) and transmission electron microscopy (TEM) revealed the uptake and translocation of MNPs, as well as their internalization in the leaf cells. Also, elemental analysis proved that manganese (Mn) and iron (Fe) contents were ∼7–9 times and ∼4–7 times higher in the leaves of MNPs-treated plants than the ones for non-treated control, respectively. 250 mg L−1 of MNPs significantly (at least p < 0.05) promoted the fresh weight (FW, %10.25). However, higher concentrations (500 and 1000 mg L−1) remarkably reduced the increase to %8 and %5, respectively, possibly due to the restricted water uptake. Also, catalase activity was increased from 91 (μM H2O2 min−1 mg−1) to 138 in leaves, and decreased to 66 in roots upon 1000 mg L−1 of MNPs application. Chlorophyll and carotenoid contents were not significantly changed, except chlorophyll a (%6 increase at 1000 mg L−1, p < 0.05). Overall, MnFe2O4 NPs were up-taken from the roots and migrated to the leaves which promoted the growth parameters of barley. Hence, MNPs can be suggested for barley breeding programs and can be proposed as effective delivery system for agrochemicals. However, the possible negative effect of MNPs due to its potential horizontal transfer from plants to animals via the food chain must be also considered.

Novel ternary nanohybrids of tetraethylenepentamine and graphene oxide decorated with MnFe2O4 magnetic nanoparticles for the adsorption of Pb(II)

Novel ternary nanohybrids, consisting of tetraethylenepentamine (TEPA), graphene oxide (GO) and manganese ferrite magnetic nanoparticles (TEPA-GO/MnFe2O4), were prepared by a facile hydrothermal method and utilized to remove Pb(II) from aqueous solution effectively. The adsorbents were characterized by SEM, TEM, XRD, FTIR, zeta potential analysis, magnetization hysteresis loop, BET and XPS. These nanoparticles exhibited superparamagnetic behavior as well as high removal efficiency for Pb(II). Moreover, numerous amino groups of the functionalized pendant TEPA on GO coupled with the porous structure of TEPA-GO/MnFe2O4 contribute to high Pb(II) adsorption capacity. The maximum Pb(II) adsorption capacity of TEPA-GO/MnFe2O4 was determined to be 263.2 mg/g at the optimized solution pH of 5.5, much higher than that of GO/MnFe2O4 (133.3 mg/g) and GO (196.1 mg/g). The kinetics and isotherm data fitted well with the pseudo-second-order kinetics and the Langmuir isotherm model, respectively. Thermodynamic studies revealed that the Pb(II) adsorption of TEPA-GO/MnFe2O4 was a endothermic and spontaneous process. The experimental results corroborated that TEPA-GO/MnFe2O4 can be efficaciously reused after washed with HCl, indicative of its potential applications in environmental cleanup.

Novel magneto-responsive nanoplatforms based on MnFe2O4 nanoparticles layer-by-layer functionalized with chitosan and sodium alginate for magnetic controlled release of curcumin

Remotely assisted drug delivery by means of magnetic biopolymeric nanoplatforms has been utilized as an important tool to improve the delivery/release of hydrophobic drugs and to address their low cargo capacity. In this work, MnFe2O4 magnetic nanoparticles (MNPs) were synthesized by thermal decomposition, coated with citrate and then functionalized with the layer-by-layer (LbL) assembly of polyelectrolyte multilayers, with chitosan as polycation and sodium alginate as polyanion. Simultaneous conductimetric and potentiometric titrations were employed to optimize the LbL deposition and to enhance the loading capacity of nanoplatforms for curcumin, a hydrophobic drug used in cancer treatment. ~200 nm sized biopolymer platforms with ~12 nm homogeneously embedded MNPs were obtained and characterized by means of XRD, HRTEM, DLS, TGA, FTIR, XPS and fluorescence spectroscopy techniques to access structural, morphological and surface properties, to probe biopolymer functionalization and to quantify drug-loading. Charge reversals (±30 mV) after each deposition confirmed polyelectrolyte adsorption and a stable LbL assembly. Magnetic interparticle interaction was reduced in the biopolymeric structure, hinting at an optimized performance in magnetic hyperthermia for magneto-assisted drug release applications. Curcumin was encapsulated, resulting in an enhanced payload (~100 μg/mg). Nanocytotoxicity assays showed that the biopolymer capping enhanced the biocompatibility of nanoplatforms, maintaining entrapped curcumin. Our results indicate the potential of synthesized nanoplatforms as an alternative way of remotely delivering/releasing curcumin for medical purposes, upon application of an alternating magnetic field, demonstrating improved efficiency and reduced toxicity.

Adsorption behavior and mechanism of different arsenic species on mesoporous MnFe2O4 magnetic nanoparticles

Arsenic pollution poses severe threat to human health, therefore dealing with the problem of arsenic contamination in water bodies is extremely important. The adsorption behaviors of different arsenic species, such as arsenate (As(V)), p-arsanilic acid (p-ASA), roxarsone (ROX), dimethylarsenate (DMA) from water using mesoporous bimetal oxide magnetic manganese ferrite nanoparticles (MnFe2O4) have been detailedly investigated. The adsorbent was synthesized via a facile co-precipitation approach and recovered conveniently owing to its strong magnetic properties. The obtained MnFe2O4 with large surface area and abundant hydroxyly functional groups exhibited excellent adsorption performance for As(V) and p-ASA, in contrast to ROX and DMA with the maximum adsorption capacities of As(V), p-ASA, ROX and DMA of 68.25 mg g−1, 59.45 mg g−1, 51.49 mg g−1, and 35.77 mg g−1, respectively. The Langmuir model and the pseudo-second-order kinetic model correlated satisfactorily with the adsorption thermodynamics and kinetics, and thermodynamic parameters depicted the spontaneous endothermic nature for the adsorption of different arsenic species. The adsorption mechanism of different arsenic species onto MnFe2O4 nanoparticles at various pH values could be explained by surface complexation and molecular structural variations. Attenuated Total internal Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) further proved that arsenic species were bonded to the surface of MnFe2O4 through the formation of an inner-sphere complex between the arsenic acid moiety and surface metal centers. The results would help to know the interaction of arsenic species with iron-manganese minerals and the mobility of arsenic species in natural environments.

Photothermal-modulated drug delivery and magnetic relaxation based on collagen/poly(γ-glutamic acid) hydrogel.

Injectable and stimuli-responsive hydrogels have attracted attention in molecular imaging and drug delivery because encapsulated diagnostic or therapeutic components in the hydrogel can be used to image or change the microenvironment of the injection site by controlling various stimuli such as enzymes, temperature, pH, and photonic energy. In this study, we developed a novel injectable and photoresponsive composite hydrogel composed of anticancer drugs, imaging contrast agents, bio-derived collagen, and multifaceted anionic polypeptide, poly (γ-glutamic acid) (γ-PGA). By the introduction of γ-PGA, the intrinsic temperature-dependent phase transition behavior of collagen was modified to a low viscous sol state at room temperature and nonflowing gel state around body temperature. The modified temperature-dependent phase transition behavior of collagen/γ-PGA hydrogels was also evaluated after loading of near-infrared (NIR) fluorophore, indocyanine green (ICG), which could transform absorbed NIR photonic energy into thermal energy. By taking advantage of the abundant carboxylate groups in γ-PGA, cationic-charged doxorubicin (Dox) and hydrophobic MnFe2O4 magnetic nanoparticles were also incorporated successfully into the collagen/γ-PGA hydrogels. By illumination of NIR light on the collagen/γ-PGA/Dox/ICG/MnFe2O4 hydrogels, the release kinetics of Dox and magnetic relaxation of MnFe2O4 nanoparticles could be modulated. The experimental results suggest that the novel injectable and NIR-responsive collagen/γ-PGA hydrogels developed in this study can be used as a theranostic platform after loading of various molecular imaging probes and therapeutic components.

Synthesis, characterization and application of a MnFe2O4@poly(o-toluidine) nanocomposite for magnetic solid-phase extraction of polycyclic aromatic hydrocarbons

A nanocomposite of poly(o-toluidine)-coated MnFe2O4 magnetic nanoparticles with a core–shell structure was synthesized by the chemical co-precipitation method and employed as a magnetic adsorbent for solid-phase extraction of ten polycyclic aromatic hydrocarbons (PAHs).