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This study introduces a simple method for preparing a new generation of MnO2 nanomaterials (MNMs) using tannic acid as a template. Two shapes of MnO2 NMs, flower-like M1-MnO2 and near-spherical M2-MnO2, were prepared and compared as dual-active nanozymes and contrast agents in magnetic resonance imaging (MRI). Various parameters, including the crystallinity, morphology, magnetic saturation (Ms), surface functionality, surface area, and porosity of the MNMs were investigated. Flower-like M1-MnO2 NMs were biocompatible and exhibited pH-sensitive oxidase and peroxidase mimetic activity, more potent than near-spherical M2-MnO2. Furthermore, the signal intensity and r1 relaxivity strongly depended on the crystallinity, morphology, pore size, and specific surface area of the synthesized MNMs. Our findings suggest that flower-like M1-MnO2 NM with acceptable dual-enzyme mimetic (oxidase-like and peroxidase-like) and T1 MRI contrast activities could be employed as a promising theranostic system for future purposes. [ABSTRACT FROM AUTHOR]

β-Cyclodextrine-based polyester was coated on the surface of gadolinium oxide nanoparticles (NPs) and then functionalised with folic acid to produce an efficient pH-sensitive targeted theranostic system (Gd2O3@PCD-FA) for doxorubicin delivery and magnetic resonance imaging (MRI). Gd2O3@PCD-FA was fully characterised by FTIR, vibrating sample magnetometer, TGA, XRD, SEM and TEM analyses. The dissolution profile of DOX showed a pH sensitive release. No significant toxicity was observed for the targeted NPs (Gd2O3@PCD-FA) and DOX-loaded NPs inhibiting M109 cells viability more efficiently than free DOX. Moreover, the negligible hemolytic activity of the targeted NPs showed their appropriate hemocompatibility. The preferential uptake was observed for the developed Gd2O3@PCD-FA-DOX NPs in comparison with Dotarem using T1- and T2-weighted MRI in the presence of folate receptor-positive and folate receptor-negative cancer cells (M109 and 4T1, respectively). Furthermore, in vivo studies revealed that Gd2O3@PCD-FA-DOX not only exhibited considerably relaxivity performance as a contrast agent for MRI, but also improved in vivo anti-tumour efficacy of the system. The results suggest that Gd2O3@PCD-FA-DOX improves its therapeutic efficacy in the treatment of solid tumours and also reduces the adverse effects, so it could be proposed as a promising drug delivery system for chemotherapy and molecular imaging diagnosis in MRI. [ABSTRACT FROM AUTHOR]

The graphene-based additives containing polyethyleneimine (PEI) or hydroxyapatite (HAP) were synthesized and their effects on the flame retardancy, thermal, mechanical properties of polyvinyl alcohol (PVA) matrix were evaluated. Thermogravimetric analysis studies (TGA) and Scanning electron microscope (SEM) images were indicated that PEI and HAP have a strong influence on the fire behavior of the composites which might be explained by the forming of a uniform and compact char during combustion. The presence of nitrogen in PEI and phosphorus in HAP which are generated nonflammable gases and phosphoric radicals, respectively at combustion conditions could represent a significant role in the catalytic char residue formation, heat transfer limitation and then diminish or even stop the combustion reactions. The char yields of the 5 wt% PVA/GO-PEI nanocomposites were increased up to 22 folds without any significant change in mechanical properties; Moreover, the char yield of PVA/GO-HAP nanocomposites was more than pure PVA (24 folds) because of its thermal stability at high temperature. All these data demonstrated that not only did PVA/GO-PEI keep the mechanical properties nearly the same as in pure PVA but also improved flame retardancy. But, the PVA/GO-HAP has great potential as flame retardants between all obtained composites. [ABSTRACT FROM AUTHOR]

In this work, the optimum condition for the adsorption of Reactive Blue 19 dye onto Fe3O4 functionalized with hyperbranched polyethylenimine (Fe@HPEI) was determined using response surface methodology. The properties of synthesized magnetic Fe@HPEI nanoparticles were ascertained using FTIR, SEM, TEM, VSM and zeta potential measurement. The experimental adsorption data indicating the positive effect of adsorbent dose and contact time, and the negative effect of pH, initial dye concentration and ionic strength on dye adsorption. At optimal condition; pH 3.4, contact time 25 min, adsorbent dose 0.4 g/L and initial dye concentration 113 mg/L, Fe@HPEI nanoparticles removed dye up to 99.27%. The maximum experimental dye adsorption was near to the predicted value of 100%, which confirmed the reliability of the selected statistical model. The dye adsorption data were fitted well to Langmuir isotherm and pseudo-second-order kinetic, and the maximum adsorption capacity was 500 mg/g. Totally, Fe@HPEI as an effective superadsorbent can be repeatedly utilized for the adsorption of dye from the aqueous environment. [ABSTRACT FROM AUTHOR]

A novel nanocatalyst was developed based on covalent surface functionalization of MCM‐41 with polyethyleneimine (PEI) using [3‐(2,3‐Epoxypropoxy)propyl] trimethoxysilane (EPO) as a cross‐linker. Amine functional groups on the surface of MCM‐41 were then conjugated with iodododecane to render an amphiphilic property to the catalyst. Palladium (II) was finally immobilized onto the MCM‐41@PEI‐dodecane and the resulted MCM‐41@aPEI‐Pd nanocatalyst was characterized by FT‐IR, TEM, ICP‐AES and XPS. Our designed nanocatalyst with a distinguished core‐shell structure and Pd2+ ions as catalytic centers was explored as an efficient and recyclable catalyst for Heck and oxidative boron Heck coupling reactions. In Heck coupling reaction, the catalytic activity of MCM‐41@aPEI‐Pd in the presence of triethylamine as base led to very high yields and selectivity. Meanwhile, the MCM‐41@aPEI‐Pd as the first semi‐heterogeneous palladium catalyst was examined in the C‐4 regioselective arylation of coumarin via the direct C‐H activation and the moderate to excellent yields were obtained toward different functional groups. Leaching test indicated the high stability of palladium on the surface of MCM‐41@aPEI‐Pd as it could be recycled for several runs without significant loss of its catalytic activity. [ABSTRACT FROM AUTHOR]

Background: Magnetic graphene oxide (Fe3O4@SiO2-GO) nanocomposite was fabricated through a facile process and its application as an excellent adsorbent for lead (II) removal was also demonstrated by applying response surface methodology (RSM). Methods: Fe3O4@SiO2-GO nanocomposite was synthesized and characterized properly. The effects of four independent variables, initial pH of solution (3.5-8.5), nanocomposite dosage (1-60 mg L-1), contact time (2-30 min), and initial lead (II) ion concentration (0.5-5 mg L-1) on the lead (II) removal efficiency were investigated and the process was optimized using RSM. Using central composite design (CCD), 44 experiments were carried out and the process response was modeled using a quadratic equation as function of the variables. Results: The optimum values of the variables were found to be 6.9, 30.5 mg L-1, 16 min, and 2.49 mg L-1 for pH, adsorbent dosage, contact time, and lead (II) initial concentration, respectively. The amount of adsorbed lead (II) after 16 min was recorded as high as 505.81 mg g-1 for 90 mg L-1 initial lead (II) ion concentration. The Sips isotherm was found to provide a good fit with the adsorption data (KS = 256 L mg-1, nS = 0.57, qm = 598.4 mg g-1, and R2 = 0.984). The mean free energy Eads was 9.901 kJ/mol which confirmed the chemisorption mechanism. The kinetic study determined an appropriate compliance of experimental data with the double exponential kinetic model (R2 = 0.982). Conclusions: Quadratic and reduced models were examined to correlate the variables with the removal efficiency of Fe3O4@SiO2-GO. According to the analysis of variance, the most influential factors were identified as pH and contact time. At the optimum condition, the adsorption yield was achieved up to nearly 100 %. [ABSTRACT FROM AUTHOR]