Poslet Shumbula

Analysis of the Interaction of Surfactants Oleic Acid and Oleylamine with Iron Oxide Nanoparticles through Molecular Mechanics Modeling

The interface interactions between surfactants oleic acid and oleylamine and magnetic nanoparticles are studied via molecular mechanics and dynamics. Mixtures of these two surfactants are widely advocated in the chemical synthesis of nanoparticles. However, the exact dynamic mechanism remains unclear. Here we report, for the first time, a comprehensive qualitative model showing the importance of acid-base complex formation between oleic acid and oleylamine as well as the presence of free protons in the engineering of nanoparticles of specific shapes and sizes. We show why critical parameters such as surfactant concentration may modify iron oxide nanoparticle shape and size and how this can be understood in the light of acid-base complex pair formation. We report on the influence these parameters have on both the in situ nanoparticle surface charge and zeta potential. Transmission electron microscopy (TEM), FTIR, and pH studies are used to confirm the validity of the calculated binding energies and number of acid-base pairs.

Synthesis and characterization of Cu3N nanoparticles using pyrrole-2-carbaldpropyliminato Cu(II) complex and Cu(NO3)2 as single-source precursors: the search for an ideal precursor

Herein, we report the synthesis and characterization of Cu3N nanocrystals using two single-source precursors, bis(pyrrole-2-carbalpropyliminato) Cu(II) (PPC) and Cu(NO3)2·3H2O. The optical and structural properties were investigated and the suitability of the two precursors was studied in terms of producing good quality Cu3N nanocrystals without the detection of Cu or oxidation to CuO. Both precursors resulted in crystalline Cu3N with an anti-ReO3 cubic structure with no presence of copper impurities, however, peaks due to excess capping agent were detected by XRD and confirmed with XPS. The PPC complex resulted in spherical nanocrystals whilst the copper nitrate resulted in nanocubes. The band gaps were in the visible region with the copper nitrate nanocrystals slightly red shifted from the PPC derived particles due to larger crystal sizes. The emission spectra were blue-shifted from the absorption band edges hence indicating an up-conversion process.

Antimicrobial Activity of Amino Acid-Capped Zinc and Copper Sulphide Nanoparticles

The synthesis of polydispersed zinc sulphide and copper sulphide nanocrystals capped with polar L-alanine (Aln) and l-aspartic acid (Asp) molecules is reported. The resulting nanocrystals were characterized by UV-visible spectroscopy (UV-Vis), photoluminescence (PL), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). UV-Vis absorption spectra of all samples were blue-shifted from the bulk band edges due to quantum confinement effects. PL emission spectrum of the nanoparticles showed peaks at 453 and 433 nm for Aln-capped ZnS and CuS nanoparticles, respectively, while peaks for Asp-capped ZnS and CuS nanoparticles were observed at 455 and 367 nm, respectively. The average particle sizes for Aln-capped ZnS and Asp-capped ZnS nanoparticles synthesized at 35°C were measured to be 2.88 nm and 1.23 nm, respectively. The antibacterial properties were tested using different strains of both positive and negative bacteria and fungi. It was found that capped-copper sulphide nanoparticles were more effective against the bacteria than capped-zinc sulphide nanoparticles. Staphylococcus aureus (ATCC 25923) was the most susceptible one with an MIC of 0.05 mg/mL for uncapped-CuS nanoparticles while Pseudomonas aeruginosa (ATCC 15442) and Cryptococcus neoformans (ATCC 14116) were the least ones with the MIC of 3.125 mg/mL for both uncapped-CuS and Aln-capped CuS.