Effective Organochlorine Pesticides Removal from Aqueous Systems by Magnetic Nanospheres Coated with Polystyrene

In this paper, magnetic nanospheres coated with polystyrene （Fe3O4@PS） were prepared for the removal of organochlorine pesticides from aqueous solutions. The obtained Fe3O4@PS was round shape with diameter of 55±11 nm. The VSM results illustrated that its higher saturated magnetization was 36.76 emu g^-1 and it could be easily separated from aqueous solutions with a permanent magnet. The adsorption results showed that pesticides could be effectively adsorbed and the adsorption equilibrium time was less than 20 mins. The pseudo-second-order model was suitable to describe the adsorption kinetics. Compared with the Freundlich adsorption model, the adsorption data fitted well with Langmuir model. The effect of salinity and humic acid was also studied and the results illustrated that they could be neglected under optimized conditions. The asobtained sorbent showed a good performance with more than 93.3% pesticides removal in treating actual water samples.

Selective oxidation of benzyl alcohols to benzoic acid catalyzed by eco-friendly cobalt thioporphyrazine catalyst supported on silica-coated magnetic nanospheres

A novel magnetically recoverable thioporphyrazine catalyst（CoPz（S-Bu）8/SiO2@Fe3O4） was prepared by immobilization of the cobalt octkis（butylthio） porphyrazine complex（CoPz（S-Bu）8） on silica-coated magnetic nanospheres（SiO2@Fe3O4）. The composite CoPz（S-Bu）8/SiO2@Fe3O4appeared to be an active catalyst in the oxidation of benzyl alcohol in aqueous solution using hydrogen peroxide（H2O2） as oxidant under Xe-lamp irradiation,with 36.4% conversion of benzyl alcohol, about 99% selectivity for benzoic acid and turnover number（TON） of 61.7 at ambient temperature. The biomimetic catalyst CoPz（S-Bu）8was supported on the magnetic carrier SiO2@Fe3O4 so as to suspend it in aqueous solution to react with substrates, utilizing its lipophilicity. Meanwhile the CoPz（S-Bu）8can use its unique advantages to control the selectivity of photocatalytic oxidation without the substrate being subjected to deep oxidation. The influence of various reaction parameters on the conversion rate of benzyl alcohol and selectivity of benzoic acid was investigated in detail. Moreover, photocatalytic oxidation of substituted benzyl alcohols was obtained with high conversion and excellent selectivity, specifically conversion close to 70%, selectivity close to 100% and TON of 113.6 for para-position electron-donating groups. The selectivity and eco-friendliness of the biomimetic photocatalyst give it great potential for practical applications.

Magnetic covalent organic framework nanospheres-based miRNA biosensor for sensitive glioma detection

Sensitive detection and accurate diagnosis/prognosis of glioma remain urgent challenges.Herein,dispersed magnetic covalent organic framework nanospheres(MCOF)with uniformed Fe3O4 nano-assembly as cores and high-crystalline COF as shells were prepared by monomer-mediated in-situ interface growth strategy.Based on the unique interaction between MCOF and hairpin DNA,a fluorescent signal amplified miRNA biosensor was constructed.It could realize the sensitive detection of miRNA-182 in different matrixes,where the detection limit,linearity range and determination coefficient(R^(2))in real blood samples reached 20 fM,0.1 pM-10 pM and 0.991,respectively.Also,it possessed good stability and precision as observed from the low intra-day/inter-day RSD and high extraction recovery.As a result,it could quantify miRNA-182 in serum of glioma patients,the concentration of which was significantly higher than that of healthy people and obviously decreased after surgery.Finally,a proof-of-concept capillary chip system using this biosensor was proposed to realize the visualized detection of miRNA-182 in microsample.These findings suggest a robust way for sensitive detection and accurate diagnosis/prognosis of glioma.

Controlled synthesis of hollow magnetic Fe3O4 nanospheres： Effect of the cooling rate

The controlled synthesis of hollow magnetite （Fe3O4） nanospheres of varying sizes and structures was successfully obtained via a facile solvothermal process and varying cooling processes. The Fe3O4 nanospheres were characterized by X-ray diffraction, transmission electron microscopy, scanning elec- tron microscopy, and superconducting quantum interference device magnetometry. The diameters of the as-synthesized nanospheres were controlled at around 500-700 nm by simply changing the cool- ing rate, which had an obvious influence on the morphology and magnetic properties of these Fe3O4 nanospheres. While a low cooling rate triggered the formation and extension of the cracks present in the Fe3O4 nanospheres, a sudden drop of temperature tended to favor multi-site nucleation of the crystals as well as the formation of compact and smooth hollow nanospheres with superior crystallinity and high saturation magnetization. The growth mechanism of hollow magnetite oxide nanospheres was proposed and the correlation between the structure and the magnetic properties of the hollow nanospheres was discussed, which promises the potential of the hollow nanospheres in various applications such as drug delivery and cell separation.

Analysis of the formation process and performance of magnetic Fe_3O_4@Poly(4-vinylpyridine) absorbent prepared by in-situ synthesis

The morphology evolution of the mesoporous magnetic composite nanospheres Fe3O4@Poly（4- vinylpyridine） during the formation process and its absorption property of Congo red were studied in this study. A simple solvothermal method was applied for the fabrication of Fe3O4@Poly（4-vinylpyridine） composites with regular structure and uniform size distribution in the presence of 4-vinylpyridine as the structure inducer. The morphology, structure and magnetism performance were characterized and the adsorption model and mechanism were discussed. The results showed that the Fe3O4@Poly（4- vinylpyridine） composites were efficient adsorbent for the removal of Congo red from water and it could be reused by a magnetic separation. The adsorption isotherm of Congo red on Fe3O4@Poly（4- vinylpyridine） composites was fitted well with the Langmuir adsorption model.