Preparation of Magnetic Iron Oxide Nanoparticles (MIONs) with Improved Saturation Magnetization Using Multifunctional Polymer Ligand

Facile Synthesis of Magnetic Iron-Based Nanoparticles from the Leach Solution of Hyperaccumulator Plant Pinus brutia for the Antibacterial Activity and Colorimetric Detection of Ascorbic Acid

It has been well known that metallic nanoparticles with striking properties possess wide application prospects in the processes of colorimetric detection, catalysis, disease diagnosis and treatment, energy, wastewater treatment, remediation, and antibacterial activity in recent years. Herein, iron-based nanoparticles (FeNPs), metallic nanoparticles, were synthesized via a facile chemical reduction method using a hyperaccumulator plant. Also, their use in antibacterial activity applications and colorimetric ascorbic acid (AA) detection was investigated. It was observed that FeNPs presented high antibacterial potency against Gram-positive bacteria of Listeria monocytogenes and Staphylococcus aureus and also Gram-negative bacteria of Escherichia coli(O157: H7), E. coli(ATCC 25922), Salmonella enteritidis, and Salmonella typhimurium. Moreover, it was found that FeNPs exhibited superior peroxidase-like activity to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue color product, oxidized TMB (oxTMB), in the presence of H₂O₂. The colorimetric AA detection could be carried out by making the solution color lighter owing to the antioxidant property of AA. The quantitative detection of AA could be performed simply, selectively, and sensitively with FeNPs with a detection limit (LOD) of 0.5462 μM in a linear range of 30-200 μM.

Performance of CO2 and Fe-modified lignin char on arsenic (V) removal from water

Biochar was produced by the pyrolysis of Kraft lignin at 600 °C followed by modification with CO₂ at 700 and 800 °C and impregnation with FeOx. The physicochemical properties and arsenic (V) adsorption performance of biochar were evaluated. The characteristics of the lignin biochar before and after CO₂ modification and FeOx impregnation were analyzed using the following methods: proximate and ultimate analysis, specific surface area (Brunauer-Emmett-Teller (BET) surface area), porosity, scanning electron microscopy and energy dispersive spectroscopy mapping, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The specific surface area and porosity of biochar were improved significantly after CO₂ modification. However, impregnation of FeOx in CO₂-modified biochar showed a 50%-60% decrease of BET surface area and porosity due to pore blocking of FeOx. The batch adsorption of arsenic (V) showed that FeOx-LC-800 (FeOx impregnation lignin char modified with CO₂ at 800 °C) had the highest adsorption efficiency among the biochars tested because of its highest Fe-O intensity and large surface area. The Langmuir adsorption model was suitable for the curve fitting arsenic (V) adsorption. The theoretical equilibrium adsorption amount (q_e) was calculated to be 6.8 mg/g using a pseudo-second-order kinetic model.

Nanoengineering with RAFT polymers: from nanocomposite design to applications

Reversible addition–fragmentation chain-transfer (RAFT) polymerization is a powerful tool for the precise formation of macromolecular building blocks that can be used for the construction of well-defined nanocomposites.

Promoting CO2 methanation via ligand-stabilized metal oxide clusters as hydrogen-donating motifs

Electroreduction uses renewable energy to upgrade carbon dioxide to value-added chemicals and fuels. Renewable methane synthesized using such a route stands to be readily deployed using existing infrastructure for the distribution and utilization of natural gas. Here we design a suite of ligand-stabilized metal oxide clusters and find that these modulate carbon dioxide reduction pathways on a copper catalyst, enabling thereby a record activity for methane electroproduction. Density functional theory calculations show adsorbed hydrogen donation from clusters to copper active sites for the *CO hydrogenation pathway towards *CHO. We promote this effect via control over cluster size and composition and demonstrate the effect on metal oxides including cobalt(II), molybdenum(VI), tungsten(VI), nickel(II) and palladium(II) oxides. We report a carbon dioxide-to-methane faradaic efficiency of 60% at a partial current density to methane of 135 milliampere per square centimetre. We showcase operation over 18 h that retains a faradaic efficiency exceeding 55%.

Enhanced Arsenic (III and V) Removal in Anoxic Environments by Hierarchically Structured Citrate/FeCO3 Nanocomposites

Novel citrate/FeCO₃ nanocomposites (CF-NCs) were synthesized for effective arsenic (III and V) sorption with constant addition of Fe²⁺ into HCO₃⁻ solution in the presence of citrate. This paper is the first report on the formation of CF-NCs, and in this study we investigate the mechanisms of arsenic uptake by the sorbent under anoxic conditions through various solid- and liquid-phase spectroscopic methods, including X-ray absorption spectroscopy. In CF-NCs, citrate was found to be incorporated into the structure of siderite (up to 17.94%) through (Fe²⁺citrate)⁻ complexes. The crystal morphology of rhombohedral siderite was changed into hierarchically nanostructured spherical aggregates composed of several sheet-like crystals, which improved the surface reactivity in the presence of sufficient citrate. Compared to pure siderite (15.2%), enhanced removal of As(III) in the range of 19.3% to 88.2% was observed, depending on the amount of incorporated citrate. The maximum sorption capacities of CF-NCs for As(III) and As(V) were 188.97 and 290.22 mg/g, respectively, which are much higher than those of previously reported siderite-based adsorbents. It was found that arsenic (III and V) sorption on CF-NCs occurred via bidentate corner-sharing surface complexation, predominantly without changes in the arsenic oxidation states. These results suggest that arsenic (III and V) can be attenuated by siderite in anoxic environments, and this attenuation can be even more effective when siderite is modified by incorporation of organic compounds such as citrate.

Highly Luminescent Copper Nanoclusters Stabilized by Ascorbic Acid for the Quantitative Detection of 4-Aminoazobenzene

As one of the widely studied metal nanoclusters, the preparation of copper nanoclusters (Cu NCs) by a facile method with high fluorescence performance has been the interest of researchers. In this paper, a simple, green, clean, and time-saving chemical etching method was used to synthesize water-soluble Cu NCs using ascorbic acid (AA) as the reducing agent. The as-prepared Cu NCs showed strong green fluorescence (with a quantum yield as high as 33.6%) and high ion stability, and good antioxidant activity as well. The resultant Cu NCs were used for the detection of 4-aminoazobenzene (one of 24 kinds of prohibited textile compounds) in water with a minimum detection limit of 1.44 μM, which has good potential for fabric safety monitoring.

Defect modified zinc oxide with augmenting sonodynamic reactive oxygen species generation

Poor chemical stability, low tumor enrichment, and weak therapeutic effects of commonly used organic sonosensitizers significantly hinder further clinical applications of sonodynamic therapy (SDT). Encouraged by the principles of semiconductor catalysis and defect chemistry, we obtained a defect-rich gadolinium (Gd) doped zinc oxide (D-ZnOx:Gd) semiconductor sonosensitizer by defect engineering for efficient deep tumor sonodynamic eradication. The abundant oxygen defect can promote the separation of the electron (e-) and hole (h+) of D-ZnOx:Gd, which significantly enhances the sonodynamic effect. In addition, D-ZnOx:Gd is more easier to adsorb water and oxygen molecules due to its rich oxygen-deficient, greatly enhancing the capacities of ROS production. A significantly higher sonodynamic ROS generation abilities and anti-deep tumor efficiency against breast cancer are obtained in such defect-rich ZnO nanobullets. This work not only broadens the applications of ZnO semiconductor nanoagent in the field of nanomedicine, but also reveals the mechanism of how the oxygen deficiency enhanced the sonodynamic efficacy of zinc oxide, providing a new application of defect engineering in the field of cancer therapy.

Targeted removal of leukemia cells from the circulating system by whole-body magnetic hyperthermia in mice

Until now, magnetic hyperthermia was used to remove solid tumors by targeting magnetic nanoparticles (MNPs) to tumor sites. In this study, leukemia cells in the bloodstream were directly removed by whole-body hyperthermia, using leukemia cell-specific MNPs. An epithelial cellular adhesion molecule (EpCAM) antibody was immobilized on the surface of MNPs (EpCAM-MNPs) to introduce the specificity of MNPs to leukemia cells. The viability of THP1 cells (human monocytic leukemia cells) was decreased to 40.8% of that in control samples by hyperthermia using EpCAM-MNPs. In AKR mice, an animal model of lymphoblastic leukemia, the number of leukemia cells was measured following the intravenous injection of EpCAM-MNPs and subsequent whole-body hyperthermia treatment. The result showed that the leukemia cell number was also decreased to 43.8% of that without the treatment of hyperthermia, determined by Leishman staining of leukemia cells. To support the results, simulation analysis of heat transfer from MNPs to leukemia cells was performed using COMSOL Multiphysics simulation software. The surface temperature of leukemia cells adhered to EpCAM-MNPs was predicted to be increased to 82 °C, whereas the temperature of free cells without adhered MNPs was predicted to be 38 °C. Taken together, leukemia cells were selectively removed by magnetic hyperthermia from the bloodstream, because EpCAM-modified magnetic particles were specifically attached to leukemia cell surfaces. This approach has the potential to remove metastatic cancer cells, and pathogenic bacteria and viruses floating in the bloodstream.

Fe3O4 Nanoparticles Functionalized with Polymer Ligand for T1-Weighted MRI In Vitro and In Vivo

Magnetic resonance imaging (MRI) has gained wide interest in early accurate diagnoses due to the high resolution and low toxicity of magnetic nanoparticles. In order to develop potential alternatives of toxic Gd- or Mn-based chelating agents, we report the synthesis of water soluble ultra-small Fe3O4 nanoparticles by a modified co-precipitation method as T1-weighted positive contrast agents. The magnetic iron oxide nanoparticles (MIONs) were functionalized by polymer ligand dodecanthiol-polymethacrylic acid (DDT-PMAA) to enhance their colloidal stability. These MIONs have high longitudinal relaxivity (r1 = 8.18 mM-1·S-1) and exhibited good results in the in vitro and in vivo MR imaging. No toxicity was observed in cytotoxicity assay and histology toxicity analysis. The MIONs@DDT-PMAA(magnetic iron oxide nanoparticles @ dodecanthiol-polymethacrylic acid) present great potential as positive contrast agents for tumor diagnosis.

Tungsten disulfide-based nanocomposites for photothermal therapy

Nanostructures of transition-metal dichalcogenides (TMDC) have raised scientific interest in the last few decades. Tungsten disulfide (WS2) nanotubes and nanoparticles are among the most extensively studied members in this group, and are used for, e.g., polymer reinforcement, lubrication and electronic devices. Their biocompatibility and low toxicity make them suitable for medical and biological applications. One potential application is photothermal therapy (PTT), a method for the targeted treatment of cancer, in which a light-responsive material is irradiated with a laser in the near-infrared range. In the current article we present WS2 nanotubes functionalized with previously reported ceric ammonium nitrate-maghemite (CAN-mag) nanoparticles, used for PTT. Functionalization of the nanotubes with CAN-mag nanoparticles resulted in a magnetic nanocomposite. When tested in vitro with two types of cancer cells, the functionalized nanotubes showed a better PTT activity compared to non-functionalized nanotubes, as well as reduced aggregation and the ability to add a second-step functionality. This ability is demonstrated here with two polymers grafted onto the nanocomposite surface, and other functionalities could be additional cancer therapy agents for achieving increased therapeutic activity.

Synthesis and Characterization of Wooden Magnetic Activated Carbon Fibers with Hierarchical Pore Structures

Wooden magnetic activated carbon fibers (WMACFs) with hierarchical pore structures were obtained by adding magnetic iron oxide (Fe₃O₄) nanoparticles into the liquefied wood. The structures and properties of WMACFs were analyzed by scanning electronmicroscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N₂ adsorption, and vibrating sample magnetometer (VSM). The results showed that WMACFs had high Brunauer-Emmett-Teller (BET) surface area (1578 m²/g) and total pore volume (0.929 cm³/g), of which 45% was the contribution of small mesopores of 2⁻3 nm. It is believed that Fe₃O₄ nanoparticles play an important role in the formation of hierarchical pores. With the Fe₃O₄ content increasing, the yield rate of WMACFs decreased, and the Fe₃O₄ crystal plane diffraction peaks and characteristic adsorption peaks were obviously observed. At the same time, it was also found that WMACFs had favorable magnetic properties when the Fe₃O₄ content was above 1.5%. As a result, WMACFs could be a promising candidate for high efficiency, low cost, and convenient separation for the magnetic field.

Biocompatible zwitterionic copolymer-stabilized magnetite nanoparticles: a simple one-pot synthesis, antifouling properties and biomagnetic separation

A simple one-pot synthesis of biocompatible and antifouling magnetite nanoparticles (Fe₃O₄NPs) was developed. The process involves co-precipitation and in situ coating of zwitterionic copolymer poly[(methacrylic acid)-co-(2-methacryloyloxyethyl phosphorylcholine)] (PMAMPC). The influence of one-step and two-step coating methods on the performance of modified Fe₃O₄NP was investigated. The PMAMPC-Fe₃O₄NP with a narrow particle size distribution obtained from the two-step approach were highly stable in aqueous media within a wide range of pH. The particles exhibited superparamagnetic behavior with high saturation magnetization values so that they could be easily separated from solution by a magnet. Their antifouling characteristics against 2 selected proteins, lysozyme (LYZ) and bovine serum albumin (BSA), as a function of copolymer molecular weight and composition were also evaluated. Moreover, taking advantage of having carboxyl groups in the coated copolymer, the PMAMPC-Fe₃O₄NP were conjugated with a model biomolecular probe, biotin. The biotin-immobilized PMAMPC-Fe₃O₄NP were then tested for their specific capturing of a target molecule, streptavidin. The results have demonstrated the potential of PMAMPC-Fe₃O₄NP prepared by the two-step in situ coating method for probe immobilization and subsequent biomagnetic separation of target molecules. The fact that the developed functionalizable magnetite nanoparticles are biocompatible and antifouling also opens up the possibility of their use in other biomedical-relevant applications.

A simple one-pot synthesis of biocompatible and antifouling magnetite nanoparticles (Fe₃O₄NPs) was developed.