Formation of Silver Nanoparticles and Self-Assembled Two-Dimensional Ordered Superlattice

Abstract

1-Nonanethiol-capped silver nanoparticles of about 4.18 nm in diameter were prepared using a liquid−liquid two-phase method. Two-dimensional ordered superlattices of the nanoparticles were formed on carbon films coated on transmission electron microscopy (TEM) copper grids by evaporating a drop of the dispersion in chloroform. The formation process of the silver nanoparticles was investigated by UV−visible absorption spectroscopy and TEM. A blue shift of the maximum absorption peak position of the UV−vis spectra occurred at the beginning of the reaction, followed by a red shift. This result indicated that large thiol-capped silver nanoparticles were formed at the beginning, then the large particles were decomposed into small particles, and in the final stage the small particles enlarged slightly again. The TEM images show directly the same process with the results from the UV−vis spectra. In addition, the UV−visible spectra of the silver nanoparticle colloidal phase obtained finally show that the system is monodisperse and can remain stable for several weeks.

Strain specificity in antimicrobial activity of silver and copper nanoparticles

“…For preparing solid media, the nutrient media was supplemented with 2% bacteriological agar (Himedia Laboratories Ltd., Mumbai) as solidifying agent. The silver and copper nanoparticles were prepared by wet chemical synthesis involving stoichiometric reaction between sodium borohydride and silver/copper ions [25]. The nitrate salts of silver and copper (S.D.…”

Biosynthesis of silver nanoparticles from the marine seaweed Sargassum wightii and their antibacterial activity against some human pathogens

“…The photoluminescence of silver metal and that of noble metal is generally attributed to electronic transition between the upper d band and conduction SP band (He et al 2001). Room temperature PL of Ag nanoparticles was recorded using an excitation wavelength of 325 nm.…”

Microwave-assisted synthesis of silver nanoparticles using benzo-18-crown-6 as reducing and stabilizing agent

“…The solution was observed to change from colourless to transparent yellow to dark yellow indicating the formation of larger number of NPs with increased heating time. There is only one symmetric absorption peak at 420 nm which is the characteristic surface plasmon resonance of spherical AgNPs (He et al 2001). According to Mie's theory, small spherical nanocrystals should exhibit a single surface plasmon band, whereas anisotropic particles should exhibit two or three bands, depending on their shape.…”

“…Metal NPs are usually prepared by reduction of metal ions in solution. Meanwhile, because of the trouble-some aggregation of NPs induced by their high surface energy, surface passivating reagent and capping reagent are usually involved in the reaction system (Manna et al 2001;He et al 2001). The choice of the capping agent is very critical because it determines the stability, solubility, reactivity and even the size and shape of the NPs during the synthesis.…”