Shokit Hussain

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.

Surfactant-assisted bio-conjugated synthesis of silver nanoparticles (AgNPs)

A simple one-spot synthetic route for the production of Ag-nanoparticles using aqueous extract of citrus lemon is being reported in presence of shape-directing cetyltrimethylammonium bromide (CTAB). To our knowledge, this is the first report where the biomolecules form a layer around a group of the Ag-nanoparticles in which the inner layer is bound to the AgNPs surface via the hydroxyl groups of citric acid. The appearance of a sharp surface plasmon resonance band in the UV–visible region might be due to the formation of spherical Ag-nanoparticles. Agglomeration number (NAg), the average number of silver atoms per nanoparticle (N), molar concentrations of nanoparticle (C) in solution, extinction coefficient (ε) and increase in the Fermi energy (ΔEF) were calculated using Mie theory and discussed. Interestingly, reaction mixture became turbid at higher [CTAB] due to the uncontrolled growth of Ag-nanoparticles. The transmission electron microscopic images of nanoparticles, recorded at different magnifications.

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.

Reversible encapsulation of silver nanoparticles into the helix of amylose (water soluble starch)

Natural biodegradable polymeric starch capped Ag-nanoparticles (AgNPs) were prepared by using extract of Dioscorea deltoidea in the presence of starch. UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, and digital images were used to determine the morphology and chemical composition of the as prepared AgNPs. The kinetics and morphology of the nano-materials (spherical, rod, triangular, irregular, truncated triangular, hexahedral, mono-dispersed, and aggregated) were discussed in terms of the [extract], [Ag+], and [starch]. Iodometric titration was used to confirm the reversible encapsulation of the AgNPs inside the helical structure of amylose. TEM images also suggest that the morphology of the encapsulated AgNPs entirely changes in comparison with the non encapsulated AgNPs. The starch functionalized AgNPs could be used for drug delivery, with the nucleation and aggregation controlled through fusogenic behaviour.

Nanoscale water soluble self-assembled zero-valent iron: role of stabilizers in their morphology

Self-assembled water soluble sheet-like zero-valent iron nano-composites have been prepared using a simple one-pot chemical reduction method using an aqueous solution of FeCl3 and NaBH4 both with and without cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS). It was demonstrated that dark brownish precipitates were formed immediately after the addition of NaBH4 into the ferric chloride solution. In the presence of CTAB and SDS, stable perfectly transparent brown colored iron sols were formed. UV-visible spectra show that both of the stabilizers (CTAB and SDS) formed a stable complex with Fe3+ ions. The synthesized Fe-nanoparticles were characterized using dynamic light scattering (DLS), energy dispersion X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible spectroscopy, and X-ray diffraction (XRD). The TEM results show that the average size of a zero-valent iron nano-sheet is about 144 to 625 nm in diameter. The mean particle size was estimated to be 203 nm with a standard deviation of 67 nm, which translated to a surface area of Fe-nanoparticles of ca. 2.0 m2 g−1. The role of surfactants and the mechanisms of nucleation and self-aggregation processes have been discussed for the first time.