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The results of the experimental and theoretical studies of the optical absorption properties of the composite metal/organic nanoparticles in colloidal solutions are reported. The nanoparticles consist of Ag-core coated with the J-aggregate of 3,3′-disulfopropyl-5,5′-dichlorothiacyanine sodium salt (TC). The absorption spectrum of the composite Ag/TC nanoparticles exhibits two peaks at λ = 395 and 480 nm, which originally come from the localized surface plasmon resonance of Ag nanoparticles and the electronic excitation of TC-dye, respectively. To explain the results obtained we calculate the extinction cross-section of such composite material on the basis of a model for the polarizability of two concentric spheres by taking into account complex frequency-dependent dielectric functions of Ag and the TC-dye and size-dependent effects. The model provides a good description of the main features in the measured absorbance. It is shown that for the core–shell nanoparticles under investigation the peak positions and their intensities are strongly dependent on their geometrical size and the thickness of the J-aggregate coating. This opens a possibility to controllable driving of the absorption properties of such composite materials.

The annual production of solid domestic wastes by population of big cities of the USSR is about 37.5 million tons. The main method of disposal is burial in designated landfills. In the USSR large landfills occupy an area of more than 140,000 hectares. It has been calculated that the mass of the landfill deposits generating methane is today about 600 million tons. The studies carried out using geophysical, isotopic, and microbiological methods at different landfills of the Moscow region have shown that the emission of methane and other gases from the surface of landfills into the atmosphere is extremely irregular and considerably less than their generation in the anaerobic zone. The most important factors determining methane emission are the thickness of the layer of buried refuse, the heterogeneity of the deposit body, and the microbiological oxidation of gases in the upper aerated ground layer. It has been shown that the temperature in the anaerobic zone of big landfills is relatively constant and in most cases is 25–35°C. Methanogenesis often is most intensive in the upper part of anaerobic zone where the content of organic matter is rather high. The stable carbon isotope composition of the biogas generated from landfills is characteristic of the methanogenesis from organic wastes and depends on the concentration of organic matter and the age of the landfill. At first a lighter gas is generated and then a heavier one as the substrate is depleted. In the upper aerated ground layer of the landfill, about 1 meter in depth, methane, hydrogen, and carbon monoxide (CH4, H2, CO) are oxidized intensively. The number of bacteria oxidizing these gases reaches 1011 cells per gram of wet refuse. In this case the stable isotope composition of methane becomes heavier and, of carbon dioxide, lighter. It has been shown that at small landfills methane can be oxidized completely in aerobic zones. The gas-oxidizing ability of the microflora of the aerated ground layer of a landfill decrease considerably in the cold season of the year. The methane emission from landfills located in the USSR is estimated at 1.2 – 2.4 billion cubic meters per year. About two-thirds comes from the European part of the country. Effective methods of decreasing methane emission into the atmosphere are the extraction of biogas from big landfills and the maintenance of good aeration of the upper ground layer at the small ones.