Silver nanoparticles have been prepared by photoreduction of silver nitrate with 254 nm UV light in the presence of poly(N-vinylpyrrolidone). The effects of PVP concentration on the particle size, the UV−vis absorption peak, and the rate of the photoreduction process were studied. The average particle size ranged from 15.2 to 22.4 nm, with the corresponding UV−vis absorption peak position at 404−418 nm in 1−0.25 wt % PVP. The rate of the photoreduction process was observed to increase with the PVP concentration. X-ray photoelectron spectroscopic studies further revealed that the polymer interacts with silver particles through the oxygen atom in the >CO group. A negative shift of binding energy in the Ag 3d5/2 for silver nanoparticles was observed.

In this paper, copper nanoparticles were prepared by the reduction of copper(II) acetate in water and 2-ethoxyethanol using hydrazine under reflux. The synthesized nanoparticles exhibit a distinct absorption peak in the region 572−582 nm. The average size variation from 6.6 to 22.7 nm in ethoxyethanol and from 15.5 to 30.2 nm in water was achieved by the addition of various amounts of a protective polymer (poly(N-vinylpyrrolidone)). The nonlinear optical properties of the copper colloids were first measured using the Z-scan technique. The χ(3)/α0 values obtained were found to be of the magnitude of 10-11−10-12 esu cm, which are in good agreement with the reported values obtained for copper nanoparticles embedded in glass.

Cu-, Eu-, or Mn-doped ZnS nanocrystalline phosphors were prepared at room temperature using a chemical synthesis method. Transmission electron microscopy observation shows that the size of the ZnS clusters is in the 3–18 nm range. New luminescence characteristics such as strong and stable visible-light emissions with different colors were observed from the doped ZnS nanocrystals at room temperature. These results strongly suggest that impurities, especially transition metals and rare-earth metals-activated ZnS nanoclusters form a new class of luminescent materials.

The interaction of ionic/nonionic surfactant micelles with strong polyelectrolytes has been studied by turbidimetric titrations. There exists a critical micellar fraction of ionic head groups, Yc, below which no interactions can be detected. At Y > Yc, the solute components form either soluble aggregates, complex coacervate, or amorphous precipitate, depending, in part, on the polymer:surfactant stoichiometry. The dependence of Yc on the square root of the ionic strength, P/2, appears as a linear phase boundary, which is rather insensitive to polymer concentration or total surfactant concentration. For several polyelectrolyte/mixed-micelle systems, we have measured the surface potential of the micelle ('F0) at values of Y and I corresponding to the polyion-micelle complex formation phase boundary. In the system poly-(dimethyldiallylammonium chloride)/sodium dodecyl sulfate, C12E06, the values of 'P0 measured from the pKt of the probe, dodecanoic acid, are constant (ca. -10.8 mV) along the phase boundary. For the same polymer-surfactant system, \P0 measured with the fluorescence probe hexadecylhydroxycoumarin increases with Yc from -18 to -24 mV along the phase boundary. For the system of reversed charge, sodium polystyrenesulfonate/dodecyldimethylamine oxide, in which the cationic surfactant head group itself acts as a potential probe, the surface potential varies from +12 to +43 mV along the phase boundary. The foregoing results, taken together with the absence of an effect of polymer chain length on Yc, suggest that critical conditions for complex formation are dictated by the cooperative adsorption of a relatively short sequence of polyion segments to the colloid surface. It appears likely that this process occurs when a critical potential is reached at the locus of the closest approach of the polymer chain to the micelle surface. The measured potential at critical conditions increases with the distance between this steric boundary and the mean position of the solubilized probe.

A modified inverse microemulsion technique was used to synthesize coated Ag2S/CdS nanocomposites of ∼10 nm in diameter. Their nonlinear absorption was observed with picosecond and nanosecond laser radiation of 532-nm wavelength. The nonlinear absorption in the Ag2S/CdS nanocomposites was enhanced, in comparison with the CdS nanoparticles, due to free-carrier absorption. In addition, the relaxation times of photoexcited free carriers in the Ag2S/CdS nanocomposites were also determined to be a few nanoseconds.