G. I. Romanovskaya

Concentration of polycyclic aromatic hydrocarbons by chemically modified silver nanoparticles

The ability of silver nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) to concentrate polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions was shown. It was found that fixed PAH molecules are capable of acting as electronic energy donors and of generating sensibilized fluorescence of silver nanoparticles. It was shown by spectral-luminescent investigations of dilute PAH solutions (5 × 10−10−1 × 10−6 g/ml) in the presence of silver nanoparticles (∼0.7 vol %) that the concentration of PAH molecules from solutions occurs due to its sorption on hydrocarbon CTAB radicals in close contact to the surface of metallic silver. On the basis of the spectral data, the sorption isotherms were obtained and the values of extraction degree and partition coefficients for naphthalene, phenanthrene, anthracene, chrysene, pyrene, and 3,4-benzopyrene were calculated. It was found that the degree of extraction values of the investigated PAHs fall within the range of 73–98%, the partition coefficients (logD) ∼ 6, and the concentration coefficients ∼105.

Sensitized Fluorescence of Silver Nanoparticles in the Presence of Pyrene

The fluorescence of pyrene adsorbed onto the surface of the cetyltrimethylammonium-coated silver nanoparticles was studied. Pyrene molecules adsorbed on freshly prepared silver particles were found to be in close proximity to silver surface thus providing the possibility of energy transfer from excited pyrene to silver cores of the particles. In that case along with the expected fluorescence of pyrene we observed the fluorescence of the silver nanoparticles induced by the excited pyrene molecules. In due course the restructuring of the cetyltrimethylammonium layer resulted in moving of pyrene molecules away from silver surface and simultaneous disappearance of the silver nanoparticles fluorescence band. These data strongly support the recent hypothesis of fluorophore-plasmon coupled emission.

Adsorption preconcentration of pyrene by silver nanoparticles and its determination in aqueous solutions

The reduction of silver nitrate with sodium borohydrate in an aqueous medium in the presence of cetyl trimethylammonium bromide gives a stable sol of silver, which can adsorb nonpolar organic compounds, e.g., polycyclic aromatic hydrocarbons, on the surface of metal nanoparticles. The subsequent luminescent determination demonstrated the effect of sensitized luminescence of silver nanoparticles, which could provide a basis for the determination of traces of polycyclic aromatic compounds in water.

Synthesis and adsorption and luminescence properties of hydrophobic silver nanoparticles in the presence of pyrene

A procedure was developed for the synthesis of hydrophobic silver nanoparticles with an average size of 4 nm in two-phase water-organic emulsions. The physical properties of the obtained silver organosol were studied by molecular spectroscopy and electron microscopy. It was found that the synthesized silver nanoparticles had a specific surface of 60–110 m2/g. It was shown that chemically modified silver nanoparticles can be used as an adsorbent for preconcentrating polycyclic aromatic hydrocarbons (using pyrene as an example) from dilute n-hexane solutions followed by luminescence determination at room temperature.

New nanomaterials for control of the luminescence of polycyclic aromatic hydrocarbons

New nanomaterials (ordered structures) have been proposed for control of the luminescence of polycyclic aromatic hydrocarbons by solubilization of the latter into ordered structures. These structures are formed by hydrophilic silver nanoparticles adsorbed on a cellulose matrix—filter paper—through their self organization and by molecules of a cationic surfactant—cetyltrimethylammonium bromide—in concentrations exceeding the critical micelle concentration. The observed enhancement of luminescence of solubilized pyrene molecules in the violet spectral range is due to the resonance of the electronic transitions of monomeric pyrene molecules in this range with a plasmon vibrations in silver nanoparticles.

Phosphorimetric Determination of Polycyclic Aromatic Hydrocarbons in Clinoptilolite-Filled Fibers at Room Temperature

The phosphorescence of polycyclic aromatic hydrocarbons (PAHs) adsorbed on natural zeolite (clinoptilolite) and clinoptilolite-filled acrylic fibers was studied at room temperature. The optimal conditions were selected for the phosphorescence of PAHs extracted from water and water–dioxane solutions at room temperature using clinoptilolite-filled fibers. The phosphorescence of PAHs in the clinoptilolite-filled fibers at room temperature is characterized by a high quantum yield and long lifetimes of PAH triplet states, as was the case at low temperatures (77 K). The results obtained indicate that the adsorbents used offer promise for the analytical chemistry of PAHs.

Spectral-kinetic relationships for the room-temperature phosphorescence of polycyclic aromatic hydrocarbons in micellar solutions

Lifetimes of triplet sates of molecules of different polycyclic aromatic hydrocarbons are measured in the system 0.1 M sodium dodecyl sulfate-0.025 M thallium nitrate-0.01 M sodium sulfite are measured, and the dependences of these quantities on the spectral luminescence characteristics are determined. Based on the obtained results, the application range of room-temperature phosphorimetry with time and spectral selection for the determination of individual polycyclic aromatic hydrocarbons in mixtures is determined.

Photochemical Synthesis of Anisotropic Silver Nanoparticles in Aqueous Solutions in the Presence of Sodium Citrate

The rapid one-step photochemical synthesis of anisotropic silver nanoparticles (ANPs) is reported. Silver ANPs were prepared from silver nitrate by a citrate route in aqueous solutions at room temperature under exposure to unfiltered light of a DRK 120 high-pressure mercury lamp. The silver ANPs form through one-electron reduction of the silver cation in its chelate complex with the production of sodium citrate photolysis. In the course of synthesis, small charged silver clusters and nanoparticles are formed first, which are then stabilized by citrate ions. Key factors that influence the synthesis of silver ANPs and their further transformation have been determined.

Fluorescence of pyrene in inhomogeneous media containing silver nanoparticles

Pyrene fluorescence in inhomogeneous media based on ionic detergents containing silver nanoparticles with different morphologies is investigated. An increase in pyrene monomer emissions in the spectral range of 400–500 nm is observed, due to the resonance between electronic transitions in pyrene molecules in that region and the plasmonic oscillations of silver nanoparticles.

Supramolecular structures of silver nanoparticles in solutions of surfactants

The ability of silver aquasols to form ordered nanostructured ensembles with linear dichroism in concentrated solutions of ionic surfactants is revealed.