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We have obtained visible range polarization spectra of template-synthesized gold nanoparticles oriented in polyethylene (PE). The plasmon resonance extinction bands observed with the incident electric field polarized parallel, perpendicular, and at intermediate angles to the direction of friction orientation are consistent with the long axis of the particles being aligned with the gross orientation axis. For all particle sizes considered (radii 16, 38, and 60 nm) the degree of linear dichroism increases with the amount of gold deposited in the template synthesis step prior to extraction and orientation. The experimental spectra agree with the predictions of the Rayleigh, Maxwell−Garnett, and dynamical Maxwell−Garnett theories only qualitatively. All of these treatments fail to predict the dependence of the spectral extinction intensities on the polarization angle θ. T-matrix scattering calculations suggest that the contribution from electric quadrupole modes cannot be ignored in the 38 and 60 nm radius particles. The calculated θ-dependence of the extinction intensity does not resemble experiment for 16 nm radius particles, but the theory−experiment comparison is more favorable for the larger radius systems. Some possible models for these observations are discussed.

Despite the high π-acidity of thioether donors, ruthenium(II) complexes with a bidentate 1,2-bis(phenylthio)ethane (dpte) ligand and two chelating diimine ligands (i.e., Ru(diimine) 2 (dpte) 2+ ) exhibit room-temperature fluid solution emission originating from a lowest MLCT excited state (diimine = 2,2′-bipyridine, 5,5′-dimethyl-2,2′-bipyridine 4,4′-di-tert-butyl-2,2′-bipyridine, 1,10-phenanthroline, 5-methyl-1,10-phenanthroline, 5-chloro-1,10-phenanthroline, 5-bromo-1,10-phenanthroline, 5-nitro-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, and 3,4,7,8-tetramethyl-1,10-phenanthroline). Crystal structures show that the complexes form 2 of the 12 possible conformational/configurational isomers, as well as nonstatistical distributions of geometric isomers; there also are short intramolecular π−π interactions between the diimine ligands and dpte phenyl groups. The photoinduced solvolysis product, [Ru(diimine) 2 (CH 3 CN) 2 ](PF 6 ) 2 , for one complex in acetonitrile also was characterized by single-crystal X-ray diffraction. Variations in the MLCT energies and Ru(III/II) redox couple, E°′(Ru 3+/2+ ), can be understood in terms of the influence of the donor properties of the ligands on the mainly metal-based HOMO and mainly diimine ligand-based LUMO. E°′(Ru 3+/2+ ) also is quantitatively described using a summative Hammett parameter (σ T ), as well as using Lever's electrochemical parameters (E L ). Recommended parametrizations for substituted 2,2′-bipyridyl and 1,10-phenanthrolinyl ligands were derived from analysis of correlations of E°′(Ru 3+/2+ ) for 99 homo-and heteroleptic ruthenium(II) tris-diimine complexes. This analysis reveals that variations in E°′(Ru 3+/2+ ) due to substituents at the 4-and 4′-positions of bipyridyl ligands and 4-and 7-positions of phenanthrolinyl ligands are significantly more strongly correlated with σ p + than either σ m or σ p . Substituents at the 5-and 6positions of phenanthrolinyl ligands are best described by σ m and have effects comparable to those of substituents at the 3-and 8positions. Correlations of E L with σ T for 1,10-phenanthrolinyl and 2,2′-bipyridyl ligands show similar results, except that σ p and σ p + are almost equally effective in describing the influence of substituents at the 4-and 4′-positions of bipyridyl ligands. MLCT energies and d 5 /d 6 -electron redox couples of the complexes with 5-substituted 1,10-phenanthroline exhibit correlations with values for other d 6 -electron metal complexes that can be rationalized in terms of the relative number of diimine ligands and substituents.

Nanocomposite materials based on metal nanoparticles and graphene oxide (GO) have gained increasing attention for their wide range of potential applications in various materials science fields. In this study, an efficient photocatalyst based on GO/ ZnO nanocomposites with embedded metal nanoparticles was successfully synthesized via a simple one-pot method. The synthesized nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. The photocatalytic activity of the synthesized nanocomposites was tested in the degradation of methylene blue (MB) dyes, as a model of water pollutants. A catalytic activity of 84% was achieved using a nanocomposite with a percentage of 3.125% GO, after 90 min sunlight irradiation. Furthermore, embedded copper and silver nanoparticles were used as dopants to study their effects on the activity of the photocatalyst. The GO−ZnO−Cu nanocomposite showed that the activity toward MB degradation was decreased by 50%, while a significant increase in the activity of MB degradation was achieved by the GO−ZnO−Ag nanocomposite. The removal efficiency of MB by the GO−ZnO−Ag nanocomposite reached 100% after 40 min of sunlight irradiation. Thus, the GO−ZnO−Ag nanocomposite has the potential to be an efficient adaptable photocatalyst for the photodegradation of organic dyes in industrial wastewater.

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