فهرست مطالب maryam zirak

Cellulose nanofibers/SiO2 nanocomposite was prepared by extraction of cellulose nanofibers (CNFs) from Yucca leaves, followed by immobilization of SiO2 nanoparticles on the surface of cellulose nanofibers denoted as SiO2@CNFs. Prepared SiO2@CNFs nanocomposite was characterized using various techniques, including Fourier Transform Infra-Red (FT-IR), X-Ray Diffraction (XRD), Thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy Dispersive Spectroscopy (EDS) analysis, and used as controlled drug delivery system for the release of doxorubicin, an anticancer drug. CNFs exhibited higher loading level of doxorubicin (79.82%) than SiO2@CNFs (72.67%), while CNFs exhibited rapid drug release, but SiO2@CNFs showed controlled drug release properties. Doxorubicin release from CNFs is not pH sensitive, as CNFs released high content of doxorubicin, 94.0% and 88.0% within 5-7 h, at both pH values of 4.5 and 7.4, respectively. However, the release of doxorubicin from SiO2@CNFs occurred slowly, and could be controlled by pH, as cumulative release percentage of doxorubicin from SiO2@CNFs were measured to be 73.5% at pH = 4.5, while 17.07% at pH = 7.4 after 48 h. Doxorubicin release kinetic was studied by fitting the experimental data with well-known kinetic models, including zero order, first order, Higuchi, Korsmeyer-Peppas, Hixson-Corwell, Weibull and Gompertz models. Results revealed that the doxorubicin release from SiO2@CNFs is well fitted with Higuchi and Hixson–Crowell models at pH = 4.5 and Hixson–Crowell model at pH = 7.4. Fitting the date using Korsmeyer-Peppas indicated the nonFickian diffusion of doxorubicin from SiO2@CNFs at pH = 4.5 by n values of 0.4755, and Fickian type diffusion at pH = 7.4 by n values of 0.3359.

A novel nanosensor based on CdSe quantum dots was developed for the detection of lead ions in aqueous solution. Synthesized nanosensor exhibited high selectivity and sensitivity for the detection of lead ions at very low concentration. Fluorescence emission of nanosensor was increased linearly within 0-500 μM concentration of Pb2+ ions. In order to synthesize nanosensor, the thioglycolic acid capped CdSe quantum dots were synthesized using Cd2+ and freshly prepared Se2- ions in the presence of thioglycolic acid, which then functionalized with ethylene diamine using EDC/NHS coupling reagent, and then reacting with fluorescein methyl ester. The structure of prepared nanosensor was characterized and confirmed using UV-Vis, Ft-IR, SEM, TEM and EDX analysis.

N-(2-Pyridylmethyl)-L-histidine functionalized Fe3O4 magnetic nanoparticles (PMHis@Fe3O4 MNPs) efficiently catalyzed three-component Mannich-type reaction of ketones, aromatic aldehydes and anilines, to synthesize β-amino ketones in good to high yields. Mannich adducts were obtained in moderate to high diastereoselectivity, favoring anti isomer. The imidazole moiety of PMHis residue on catalyst plays an important role in the diastereoselectivity. PMHis@Fe3O4 MNPs were prepared via simple coprecipitation from an aqueous solution of Fe2+ and Fe3+ ions using NH4OH in the presence of L-histidine, followed by reductive amination with 2-pyridine carbaldehyde in the presence of NaBH4. Obtained PMHis@Fe3O4 MNPs were characterized by FT-IR, XRD, VSM, BET, TGA, SEM, EDX and TEM analysis.

3,6-Diphenylpyrazin-2,5-dione was prepared in two steps from reaction of phenylglyoxal monohydrate with ammonium acetate in water at room temperature, followed by subjecting with hydroxyl amine hydrochloride in the presence of NaOH in a mixture of EtOH/water under reflux conditions, and used as an efficient ligand in palladium catalyzed Heck reaction between aryl halides and various alkenes. The products were obtained in good to high yields.In addition to FT-IR and NMR, the structure of the ligand was also confirmed by single crystal X-ray crystallography. Easy preparation, inexpensiveness, and stability in air and moisture are the main advantageous of this ligand.