Thermal lens spectrometry for the synthesis and study of nanocomposites on the basis of silver salts absorbed by a polyacrylate matrix

Thermal lens spectrometry is applied to determine the absorption of transparent nanocomposite materials, which are produced by the thermal decomposition of silver salts absorbed in the bulk of a polymethacrylate matrix. The high spatial resolution of determination, corresponding to the size of laser beams, makes it possible to evaluate the homogeneity for the distribution of coloration in the matrix. The advantages of thermal lens spectrometry over spectrophotometry include the weak effect of sample scattering on the results of its absorption determination and a higher sensitivity of determination, which may exceed that of spectrophotometry by one or two orders of magnitude. The possibility of achieving local syntheses of nanosized particles in the bulk of the matrix by virtue of the photoinduced decomposition of silver salts in initial polyacrylate materials is shown. Thermal lens experiments also allow the combination of the synthesis of silver nanoparticles and control of the absorbance for the prepared structural units.     

Reconstruction of the Q band spectrum of the 1285-cm−1 transition in the CO2 molecule from measurements of a pulsed response

By using the method of nonstationary spectroscopy of coherent anti-Stokes Raman scattering, pulsed responses of the Q band of the vibrational-rotational transition in the CO₂ molecule at a frequency of 1285 cm^?1 are measured under conditions of broadening close to the Doppler type. The ratios of the amplitudes of Q-band components at known frequencies are obtained by fitting to the measured pulsed responses.     

Surface-Modified Oxide Nanoparticles: Synthesis and Application

Russian Journal of General Chemistry - This review deals with one of the most important classes of nanomaterials — oxide nanoparticles. Preparative methods for the synthesis of nanooxides,...     

Spectral characteristics of subcritical carbon dioxide in nanopores

Coherent anti-Stokes Raman scattering spectra measured within the Q-branch of the vibrational transition ν₁ are used to gain insights into the state of carbon dioxide molecules in nanopores of Vycor™ glass at room temperature (20.5°C) and a subcritical temperature of 30.5°C and gas pressures up to the saturation point P _sat for each temperature. Along with the main spectral component, belonging to gaseous CO₂ molecules, the spectra recorded at pressures close to P _sat feature a second (low-frequency) component. The second component is associated with the contribution from the CO₂ molecules trapped inside pores. A spectral deconvolution with account for the interference of these two bands makes it possible to estimate the spectral characteristics of the second (low-frequency) component at each temperature. At 20.5°C, the bandwidth of the low-frequency component decreases with CO₂ pressure, a behavior that can be explained by the transition of CO₂ from the adsorbed to the condensed state in the pore. At the subcritical temperature of 30.5°C, the spectral width of the second component is pressure-independent and close to the value measured in the bulk of the supercritical fluid, a result likely associated with a low-temperature shift of the critical point of the substance trapped in nanopores.     

Preparation and Use of Chemically Modified Noble Metal Nanoparticles

Papers dealing with chemical modification of the surface of noble metal nanoparticles and their use in analytical and bioanalytical chemistry, pharmacology, etc., are analyzed. Grafting of a layer of preset chemical composition on the nanoparticle surface allows preparation of functional materials combining the properties of the metal core (surface plasmon resonance, enhancement of fluorescence and nonelastic scattering) and shell (selective interaction with components of the surrounding medium). Combination of these properties opens wide prospects for using the modified nanoparticles in various branches of science and engineering, primary in chemical and biochemical analysis, and also in pharmacology.     

Synthesis of highly stable silver colloids stabilized with water soluble sulfonated polyaniline

A simple technique was developed for the synthesis of silver nanoparticles (NPs) in an aqueous medium using water soluble sulfonated polyaniline as a new non-covalent effective stabilizer. The narrow size distribution of the NPs was achieved through the synthesis. In neutral and basic solutions the as-prepared silver NPs demonstrated resistance toward aggregation over several months and at least a few days at pH 1. The versatility of the procedure was demonstrated also for the preparation of gold nanoparticles. Transmission electron microscopy with electron microdiffraction, UV-vis spectroscopy, XRD, XPS and FTIR analyses were used to characterize the structure and chemical composition of as obtained silver NPs.     

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.     

Spectrophotometric nonenzymatic determination of hydrogen peroxide using silver nanoparticles

A nonenzymatic method was developed for the detection and quantification of hydrogen peroxide using metallic sols obtained by the reduction of silver compounds with sodium borohydride in the presence of a surface stabilizer. These sols changed color on exposure to aqueous solutions of hydrogen peroxide. The nature of the stabilizer used in sol preparation affects spectral characteristics of the final product formed in the reaction with hydrogen peroxide. In the case of polyvinyl pyrrolidone, the intensity of the surface plasmon resosnance absorption band at 405 nm decreased. In using cetyltrimethylammonium bromide, a signal at 519 nm appeared along with the similar decrease in the absorption band at 408 nm. The band intensity depends on the concentration of hydrogen peroxide. The described phenomena can form a basis for the development of procedures for the qualitative and quantitative determination of hydrogen peroxide in water bodies.     

Metal complexes in catalytic olefin transformations. 2. Structure of phosphine ligands attached to silica; Ni-catalysts for ethylene dimerization

-Bis(diphenylphosphine)aminopropyltriethoxysilane is synthesized and studied by IR and¹H,¹³C, and³¹P^1H NMR spectroscopies for the first time. Chemical modification of silica with (EtO)₃Si(CH₂)₃N(PPh₂)₂ gives the support (-DPAMPS) containing identical N(PPh₂)₂ ligands on its surface. Subsequent treatment of the support with (EtO)₃Si(CH₂)₃NH₂ and ClPPh₂ gives a silica surface containing two types of attached ligands, NH₂ and N(PPh₂)₂, in the ratio 11. The heterogenized complexes Ni-HMC, prepared by ligand exchange between Ni(PPh₃)_n (n=3, 4) and -DPAMPS, in combination with Et₂AlCl exhibit activity and selectivity for ethylene dimerization.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2674–2678, December, 1989.