Pure Silver Nanoparticles Research Articles

Low-Temperature Metallic Alloying of Copper and Silver Nanoparticles with Gold Nanoparticles through Digestive Ripening

We describe a remarkable and simple alloying procedure in which noble metal intermetallic nanoparticles are produced in gram quantities via digestive ripening. This process involves mixing of separately prepared colloids of pure Au and pure Ag or Cu particles and then heating in the presence of an alkanethiol under reflux. The result after 1 h is alloy nanoparticles. Particles synthesized according to this procedure were characterized by UV-vis spectroscopy, EDX analysis, and high-resolution electron microscopy, the results of which confirm the formation of alloy particles. The particles of 5.6+/-0.5 nm diameter for Au/Ag and 4.8+/-1.0 nm diameter for Cu/Au undergo facile self-assembly to form 3-D superlattice ordering. It appears that during this digestive ripening process, the organic ligands display an extraordinary chemistry in which atom transfer between atomically pure copper, silver, and gold metal nanoparticles yields monodisperse alloy nanoparticles.

Rapid synthesis of Au, Ag, and bimetallic Au core–Ag shell nanoparticles using Neem ( Azadirachta indica) leaf broth

We report on the use of Neem ( Azadirachta indica) leaf broth in the extracellular synthesis of pure metallic silver and gold nanoparticles and bimetallic Au/Ag nanoparticles. On treatment of aqueous solutions of silver nitrate and chloroauric acid with Neem leaf extract, the rapid formation of stable silver and gold nanoparticles at high concentrations is observed to occur. The silver and gold nanoparticles are polydisperse, with a large percentage of gold particles exhibiting an interesting flat, platelike morphology. Competitive reduction of Au 3+ and Ag + ions present simultaneously in solution during exposure to Neem leaf extract leads to the synthesis of bimetallic Au core–Ag shell nanoparticles in solution. Transmission electron microscopy revealed that the silver nanoparticles are adsorbed onto the gold nanoparticles, forming a core–shell structure. The rates of reduction of the metal ions by Neem leaf extract are much faster than those observed by us in our earlier studies using microorganisms such as fungi, highlighting the possibility that nanoparticle biological synthesis methodologies will achieve rates of synthesis comparable to those of chemical methods.

石英ガラスヘの金属負イオン多重注入による表面プラズモン共鳴吸収帯域の制御

Optical absorption properties of Cu and Ag double metal negative-ion-implanted silica glasses have been investigated from a standpoint of controlling absorption band due to surface plasmon resonance of nanoparticles. Three silica glasses were implanted with Cu negative ions at 30, 60 and 90 keV, respectively, with dose of 1 × 1017 ions/cm2. Then, Ag negative ions were implanted into each sample at a constant condition of 40 keV and 5 × 1016 ions/cm2.Optical absorption spectra were measured after annealing at various temperatures for 1 hour in Ar gas flow. In all samples annealed at 500 °C and below, intense and wide absorption with a peak of 2.6-2.8 eV was observed, and the peak position was moved to higher energy with increase in annealing temperature. These absorption peaks were considered to be due to Cu-Ag alloy nanoparticles. After annealing at 600-800°C, a sharp and intense absorption peak was observed for all the samples at photon energy of 3.1 eV, of which the absorption corresponded to that due to surface plasmon resonance of pure silver nanoparticles.