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.     

Ionic hydrogenation in the presence of surface-active substances

Conclusions Surface-active substances can be efficient catalysts of the ionic hydrogenation reaction.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimichekaya, No. 4, pp. 941–942, April, 1984.     

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.     

Quasi-one-dimensional arrangement of silver nanoparticles templated by cellulose microfibrils

We demonstrate a simple, facile approach to the deposition of silver nanoparticles on the surface of cellulose microfibrils with a quasi-one-dimensional arrangement. The process involves the generation of aldehyde groups by oxidizing the surface of cellulose microfibrils and then the assembly of silver nanoparticles on the surface by means of the silver mirror reaction. The linear nature of the microfibrils and the relatively uniform surface chemical modification result in a uniform linear distribution of silver particles along the microfibrils. The effects of various reaction parameters, such as the reaction time for the reduction process and employed starting materials, have been investigated by transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy. Additionally, the products were examined for their electric current-voltage characteristics, the results showing that these materials had an electric conductivity of approximately 5 S/cm, being different from either the oxidated cellulose or bulk silver materials by many orders of magnitude.     

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.     

A silica-silver nanocomposite obtained by sol-gel method in the presence of silver nanoparticles

Silver nanoparticles (AgNPs) were obtained by a redox reaction, using a glucose-containing cyclosiloxane as a reduction agent and stabilizer. Then the AgNPs aqueous solution was used as the reaction medium for the sol-gel process, starting from tetraethylorthosilicate (TEOS) as silica precursor. The nanocomposite material resulted (SilAg) after solvent removal, aging and calcination and was investigated by infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy coupled with energy dispersive X-ray system (SEM/EDX), transmission electron microscopy (TEM), energy-dispersive X-ray fluorescence spectroscopy (EDXRF), X-ray diffraction (XRD) and dynamic vapor sorption (DVS). The results were compared to model silicas obtained without silver. A higher condensation degree in SilAg was obtained due to the basic medium used in the first step and was confirmed by a sorption capacity lower than for the model silicas. The solid surface area calculated with GAB analysis using DVS data for the water vapors is 210 m² g^?1. The nanocomposite showed good catalytic activity for hydrogen peroxide decomposition.      

Highly-loaded silver nanoparticles in ultrafine cellulose acetate nanofibrillar aerogel

A facile method was developed to load a large amount of silver nanoparticles into a biodegradable and biocompatible cellulose acetate (CA) nanofibrillar aerogel in a controlled manner. The micro-sized CA fibrils were separated into nano-sized fibrils by salt-assisted chemical treatment in a water-acetone co-solvent to give a nanofibrillar structure with a diameter of 20-50 nm, BET surface area of 110 m²/g, and porosity of 96%. Using the high electron-rich oxygen density in the CA macromolecules and the large surface area of the CA nanoporous structure as an effective nanoreactor, the in-situ direct metallization technique was successfully used to synthesize Ag nanoparticles with an average diameter of 2.8 nm and a loading content of up to 6.98 wt%, which can hardly be achieved by previous methods. This novel procedure provides a facile and economic way to manufacture Ag nanoparticles supported on a porous membrane for various biomedical applications.     

Biodegradation of flax fibers in the presence of silver nanoparticles

Biodegradation of flax fibers differing in the chemical composition, structure of cellulose, and content of concomitant natural impurities (pectin compounds, lignin, hemicellulose) was studied. The effect exerted on the biodegradation by silver nanoparticles immobilized in the fiber was evaluated.     

Gas chromatographic properties of methacrylate polymers modified by silver nanoparticles

Russian Chemical Bulletin - The gas chromatographic properties of the porous methacrylate polymers, copolymers of 2,3-epoxypropyl methacrylate (2,3-EPMA) and ethylenedimethacrylate (EDMA), modified...     

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.     

Antimicrobial activity of silver nanoparticles in situ growth on TEMPO-mediated oxidized bacterial cellulose

In order to improve the antimicrobial activity of bacterial cellulose (BC), the silver nanoparticles (Ag NPs) were in situ fabricated on the BC membranes, affording BC and Ag hybrid antimicrobial materials, BC + Ag, which possesses excellent antimicrobial performance. Typically, carboxyl groups were firstly introduced into BC by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation. Then, the carboxyl-functionalized BC was performed with ion-exchange reaction to change the sodium ions into Ag⁺ by immersing in AgNO₃ aqueous solution, generating Ag⁺ anchored BC. Finally, two types of distinct reductive reagents including NaBH₄ and sodium citrate were employed to transform Ag⁺ into Ag NPs to fabricate BC + Ag. The diameters of Ag NPs were determined to be 3.8 nm for NaBH₄-reduced BC + Ag, and 22.0 nm for sodium citrate-reduced one, respectively. The silver content of BC + Ag were determined to be 1.944 and 2.895 wt% for NaBH₄-reduced sample and sodium citrate-reduced one, respectively. Two types of BC + Ag both showed a slow and persistent Ag⁺ release profile, but the NaBH₄-reduced one released much more Ag⁺ than that of sodium citrate under the same measurement condition. In-depth antibacterial analysis via the disc diffusion and colony forming count method disclosed that BC + Ag exhibited strong bactericidal effects against both Escherichia coli and Staphylococcus aureus. And the antibacterial activity of NaBH₄-reduced BC + Ag was higher than the sodium citrate-reduced one. Overall, this study would further improve the antibacterial efficiency of BC + Ag.     

Rapid determination of surface-active substances by fast-scan differential-pulse voltammetry

Fast-scan differential-pulse voltammograms of air-saturated acetate buffer and mercury nitrate solutions are presented. The current-voltage curves obtained are markedly influenced by surface-active substances (SAS). The peak potential of the voltammogram shifts to more positive potentials with increasing concentration of the SAS. This effect can be utilized for analytical purposes.     

Electrocatalytic dechlorination of chloroacetic acids by silver nanoparticles modified glassy carbon electrode

A simple potentiostatic method was employed to prepare silver nanoparticles deposited on glassy carbon electrode. The silver nanoparticles exhibit extraordinary electrocatalytic activities toward the reduction process of chloroacetic acids. The electrochemical behavior of trichloroacetic acid, dichloroacetic acid, and monochloroacetic acid has been investigated by cyclic voltammetry at the silver nanoparticles-modified glassy carbon electrode in 0.1 M LiClO₄ solution; each compound exhibits a series of reduction peaks which represent sequential dechlorination steps up to acetic acid. The electrocatalytic dechlorination mechanism for chloroacetic acids was also discussed in this work.     

Preparation of silver nanoparticles on cellulose nanocrystals and the application in electrochemical detection of DNA hybridization

Synthesis of Ag nanopaticles was carried out with carboxylated cellulose nanocrystals as the scaffolds by reducing metallic cations using NaBH₄. Ag particles with a size less than 10 nm were readily prepared and dispersed well. The carboxyl and hydroxyl groups of carboxylated cellulose nanocrystals supplied a coordination effect to adsorb metallic cations and Ag nanoparticles, which prevent the aggregation of nanoparticles. The carboxylated cellulose nanocrystals carrying Ag nanoparticles were used as labels for electrical detection of DNA hybridization.     

Facile size-regulated synthesis of silver nanoparticles by controlled thermolysis of silver alkylcarboxylates in the presence of alkylamines with different chain lengths

Controlled thermolysis of silver alkylcarboxylates with primary alkylamines was investigated as a facile synthetic method of silver nanoparticles. A series of silver alkylcarboxylates, C(7)H(15)COOAg, C(13)H(27)COOAg, and C(17)H(35)COOAg, have been prepared and the thermolysis of those silver alkylcarboxylates in the presence of various alkylamines, C(8)H(17)NH(2), C(12)H(25)NH(2), and C(18)H(37)NH(2), with no use of solvent was conducted at 120 or 180 degrees C for 5 h, providing spherical silver nanoparticles stabilized by alkylcarboxylates and alkylamines. The size and dispersibility of nanoparticles depend on the alkyl chain length of the precursors, alkylcarboxylates and alkylamines.     

In situ synthesis of silver nanoparticles on dialdehyde cellulose as reliable SERS substrate

Cellulose - Dialdehyde cellulose (DAC) has considerable potential as an effective metal nanoparticle support material for the preparation of highly sensitive SERS substrates. In this study, a SERS...