Ommer Bashir

Effects of ionic surfactants on the morphology of silver nanoparticles using Paan (Piper betel) leaf petiole extract

Stable silver nanoparticles were synthesized by the reduction of silver ions with a Paan (Piper betel) leaf petiole extract in absence and presence of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS). The reaction process was simple and convenient to handle, and was monitored using ultraviolet-visible spectroscopy. Absorbance of Ag-nanoparticles increases with the concentrations of Paan leaf extract, acts as reducing, stabilizing and capping agents. The polyphenolic groups of petiole extract are responsible to the rapid reduction of Ag(+) ions into metallic Ag(0). The results indicated that the shape of the spectra, number of peaks and its position strongly depend on the concentration of CTAB, which played a shape-controlling role during the formation of silver nanoparticles in the solutions, whereas SDS has no significant effect. The morphology (spherical, truncated triangular polyhedral plate and some irregular nanoparticles) and crystalline phase of the particles were determined from transmission electron microscopy (TEM) and selected area electron diffraction (SAED).

Encapsulation of silver nanocomposites and effects of stabilizers

Silver nanocomposites (AgCPs) have been synthesized by chemical reduction from silver nitrate and sodium borohydride in presence of two stabilizers. Starch and poly (vinyl) alcohol, PVA with its rich source of polyhydroxy groups has been exploited for the capping of AgCPs. The ageing of NaBH4 aqueous solution, molar ratios of the reactants, nature of the stabilizers, mixing order of NaBH4 as well as capping agents have great influence on the morphology of AgCPs. We used the iodometric titration to conform the encapsulation of AgCPs inside the helical structure of starch. The reversible nature of encapsulation has been studied by UV-vis spectroscopic technique. Well-dispersed with an approximate size of 10nm and aggregated with an approximate size of 24-52 nm AgCPs were observed in the absence and presence of stabilizers (starch and PVA), respectively. TEM images indicates that the reaction mixture containing different order of reactants and stabilizers (PVA+NaBH4+Ag(+), PVA+Ag(+)+NaBH4, starch+NaBH4+Ag(+) and starch+Ag(+)+NaBH4) have different morphology. Added electrolytes (NaCl, NaBr and NaI) do not detached the Ag(+) ions from the surface of AgNCs.

Aggregation of Congo red with surfactants and Ag-nanoparticles in an aqueous solution.

Self aggregation, sorption, and interaction of Congo red, with cetyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS), Ag(+) ions and silver nanoparticles have been determined spectrophotometrically. Congo red self-aggregation was identified from UV-visible spectra due to the shrinkage in an absorption band at 495 nm. The shape of the absorbance spectrum changed entirely with increasing [Congo red] but wavelength maxima remain unchanged. The molar absorptivity was found to be 9804 mol(-1) dm(3) cm(-1) at 495 nm. Absorption spectra of Congo red with Ag(+) ions show an isosbestic point. The complex formation constant and difference in absorption coefficients were found to be 8.5 × 10(4) mol(-1) dm(3) and 11,764 mol(-1) dm(3) cm(-1), respectively. Silver nano-particles could not be used for the catalytic degradation of Congo red because it results in the formation of a strong complex with them. Sodium dodecylsulfate did not show any significant interaction with this dye. Congo red was also used as a probe to determine the critical micellar concentration of CTAB.

Synthesis, optical properties, stability, and encapsulation of Cu-nanoparticles.

Starch-capped copper nanoparticles (CuNPs) were prepared by a chemical reduction method using hydrazine, copper sulfate and starch as reducing, oxidizing and stabilizing agents, respectively, for the first time at room temperature. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction patterns (EDX), X-ray photoelectron spectroscopy (XPS), fourier transform infrared (FT-IR) spectroscopy, thermo-gravimetric analysis (TGA), and ultraviolet-visible spectroscopy. The effect of [starch], [hydrazine] and [copper sulfate] on the optical properties of CuNPs were studied by UV-visible spectrophotometrically. The hydrazine concentrations have large impact on the surface Plasmon resonance absorbance, nature of the reaction time curves and reaction rates decreases with [hydrazine]. Starch concentrations have no effect on the path of the CuNPs formation. The hexahedral with some irregular shaped CuNPs were formed in presence of starch with diameter 900 nm. Starch acted as a stabilizing, shape-directing and capping agent during the growth processes. The KI-I2 reagent could not replace CuNps from the inner helical structure of starch.

Cu nanoparticles: synthesis, crystallographic characterization, and stability

Synthesis, crystallographic characterization, and time evaluation morphology of stable copper nanoparticles (CuNPs) have been reported for the first time at room temperature without the protection of any inert gas in presence of cetyltrimethylammonium bromide (CTABr). The morphology and structure determination were determined by using the conventional techniques such as UV–vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), electron diffraction (EDX) patterns, thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Reaction time has marked influence on the size, shape, and the size distribution of CuNPs. From the TEM analysis, it was found that the initially, quantum dots, nanorods and some irregular particles were formed. As the reaction time increases, triangular nanoplates along with nanorods were formed. The optical band gap and width of the band tail of the Cu nanostructural were estimated by using the absorption spectrum fitting method. The work reported in this paper would be helpful for the large-scale production of CuNPs at room temperature.