Fabrication of the magnetic mesoporous silica Fe-MCM-41-A as efficient adsorbent: performance, kinetics and mechanism

Antibiotics are emerging pollutants and increasingly present in aquaculture and industrial wastewater. Due to their impact on the environment and health, their removal has recently become a significant concern. In this investigation, we synthesized nano zero-valent iron-loaded magnetic mesoporous silica (Fe-MCM-41-A) via precipitation and applied the adsorption of oxytetracycline (OTC) from an aqueous solution. The effects of competing ions such as Na⁺, Ca²⁺ and Cu²⁺ on the adsorption process under different pH conditions were studied in depth to providing a theoretical basis for the application of nanomaterials. The characterization of the obtained material through transmission electron microscopy demonstrates that the adsorbent possesses hexagonal channels, which facilitate mass transfer during adsorption. The loaded zero-valent iron made the magnetic, and was thus separated under an applied magnetic field. The adsorption of OTC onto Fe-MCM-41-A is rapid and obeys the pseudo-second-order kinetic model, and the maximum adsorption capacity of OTC is 625.90 mg g^-1. The reaction between OTC and Fe-MCM-41-A was inner complexation and was less affected by the Na⁺. The effect of Ca²⁺ on the adsorption was small under acidic and neutral conditions. However, the promotion effect of Ca²⁺ increased by the increase of pH. Cu²⁺ decreased the removal efficiencies continuously and the inhibitory effects decrease varied with the increase of pH. We propose that surface complexing, ion-exchange, cationic π-bonding, hydrogen bonding, and hydrophobicity are responsible for the adsorption of OTC onto Fe-MCM-41-A.

Fluorescent and Magnetic Mesoporous Hybrid Material: A Chemical and Biological Nanosensor for Hg(2+) Ions

We introduce “sense, track and separate” approach for the removal of Hg²⁺ ion from aqueous media using highly ordered and magnetic mesoporous ferrosilicate nanocages functionalised with rhodamine fluorophore derivative. These functionalised materials offer both fluorescent and magnetic properties in a single system which help not only to selectively sense the Hg²⁺ ions with a high precision but also adsorb and separate a significant amount of Hg²⁺ ion in aqueous media. We demonstrate that the magnetic affinity of these materials, generated from the ultrafine γ-Fe₂O₃ nanoparticles present inside the nanochannels of the support, can efficiently be used as a fluorescent tag to sense the Hg²⁺ ions present in NIH3T3 fibroblasts live cells and to track the movement of the cells by external magnetic field monitored using confocal fluorescence microscopy. This simple approach of introducing multiple functions in the magnetic mesoporous materials raise the prospect of creating new advanced functional materials by fusing organic, inorganic and biomolecules to create advanced hybrid nanoporous materials which have a potential use not only for sensing and the separation of toxic metal ions but also for cell tracking in bio-separation and the drug delivery.

Synthesis of small-sized, porous, and low-toxic magnetite nanoparticles by thin POSS silica coating

In this communication, we report the synthesis of small-sized (<10 nm), water-soluble, magnetic nanoparticles (MNPs) coated with polyhedral oligomeric silsesquioxanes (POSS), which contain either polyethylene glycol (PEG) or octa(tetramethylammonium) (OctaTMA) as functional groups. The POSS-coated MNPs exhibit superparamagnetic behavior with saturation magnetic moments (51-53 emu g(-1)) comparable to silica-coated MNPs. They also provide good colloidal stability at different pH and salt concentrations, and low cytotoxicity to MCF-7 human breast epithelial cells. The relaxivity data and magnetic resonance (MR) phantom images demonstrate the potential application of these MNPs in bioimaging.

Synthesis, characterization and biocompatibility evaluation of iron oxide incorporated magnetic mesoporous silica

On the basis of a thermal process, a facile, low cost, one-step approach for preparing iron oxide (Fe(2)O(3)) incorporated ordered magnetic mesoporous silica nanocomposites by a co-operative self-assembly approach is presented. Various mesostructured silica materials incorporated with different amounts of iron oxide (nSi/nFe = 1/1, 1/0.5, 1/0.25 and 1/0.123) at various pH (<1, 3, 5 and 7) were synthesized and characterized by electron microscopy and X-ray diffractometry. Further, the surface area and magnetic properties were evaluated using N(2)-sorption analyses, and a superconducting quantum interference device interfaced with a vibrating sample magnetometer (SQUID-VSM) respectively. The transmission electron micrographs and nitrogen sorption analysis indicated that most of the Fe(2)O(3) domains of several nanometers were embedded in the silica walls, rather than dispersed in the mesopores. The incorporation of iron oxide into the mesopores without compromising the structural and textural properties was achieved at pH < 1. These structures have great potential in diagnostics and therapeutics. However, the acceptance of this material by the biological host is a critical issue for such biomedical applications. In this study, we have also evaluated the in vivo biocompatibility of these magnetic mesoporous materials in a rat model. The histopathological results show that this magnetic material can be classified as a level 2 biomaterial that can be safely used for short term applications such as MRI imaging, hyperthermia, targeted drug delivery, etc.