Surface plasmon resonance of Ag organosols: Experimental and theoretical investigations

The aim of this paper is to investigate and compare the changes in surface plasmon resonance (SPR) of silver (Ag) hydrosol and organosols obtained by experimental and theoretical approaches. Silver nanoparticles (Ag NPs) of 5 ± 1.5 nm in diameter were prepared in water by reduction of silver nitrate with sodium borohydride. Nanoparticles were subsequently transferred into different organic solvents (chloroform, hexane, toluene, 1,2-dichlorobenzene) using oleylamine as a transfer agent. These solvents were chosen because of the differences in their refractive indices. Using UV-Vis absorption spectrophotometry and transmission electron microscopy (TEM), we confirmed that there were no shape and size changes of the nanoparticles upon the transfer to the organic phase. The absorption spectra of the obtained Ag organosols showed only changes in the position of SPR band depending on dielectric property of the used solvent. To analyze these changes, absorption spectra were modelled using Mie theory for small spherical particles. The experimental and theoretical resonance values were compared with those predicted by Drude model and its limitations in the analysis of absorption behavior of Ag NPs in organic solvents were briefly discussed

Two-phase boundary synthesis and optical properties of silver/polyaniline nanocomposites

Nanocomposites containing metal nanoparticles, dispersed in electrically conducting polymers such as polyaniline, show enhanced sensing, electrical and catalytic properties as compared with those of neat polymer. These composites have generated increasing interest as advanced technological materials due to synergistic effects of both components. Here, we report silver/polyaniline (Ag/PANI) nanocomposites obtained through a two-phase water/toluene interfacial reaction. As prepared silver nanoparticles in toluene with oleylamine as a reducing and stabilizing agent, were used as nucleation centers for the polymerization of aniline. Once the polymerization occurs at the interface of the organic (containing the aniline and the silver nanoparticles) and aqueous (containing the oxidizing ammonium persulfate agent) phase, the polymer grows around the silver nanoparticles and forming the nanocomposite structure. The formation of Ag/PANI nanocomposite was characterized by UV–Vis and FTIR spectroscopy, and transmission electron microscopy. In contrast to pure PANI, the absorption spectrum of Ag/PANI nanocomposite showed additional strong band assigned to surface plasmon resonance absorption of the electrons in the conducting silver bands

Synthesis and optical behavior of copper nanoparticles in different media

In this report, we describe a simple and rapid chemical reduction method with inert gas protection, for preparing stable copper nanoparticle with average particle size of 9.4 nm. In our synthesis route, ascorbic acid is used as antioxidant to effectively prevent the general oxidation process during copper nuclei formation. As-prepared copper nanoparticles were transferred from water phase to different organic solvents (hexane, octane, cyclohexane, and toluene) using oleylamine as a phase transfer agent. This should allow dispersion of the particles in both polar and nonpolar solvents and avoid particle aggregation during the solvent exchange process. Transmission electron microscopy and UV–Vis spectroscopy contributed to the analysis of size and optical properties of the copper nanoparticles in different media, respectively. The advantages of such solvent exchange process can be found in the applications of metal particles as catalysts for organic reactions in nonpolar solvents and in the study of the changes in surface chemistry depending on the surrounding medium and on the adsorption of different moieties

Surface plasmon resonance of Ag organosols: Experimental and theoretical investigations

Silver nanoparticles (Ag NP), 5 ± 1.5 nm in diameter, were prepared in water by reduction of the silver nitrate with sodium borohydride and transferred into different organic solvents using oleylamine as a transfer agent. The UV-Vis absorption spectra of obtained Ag organosols showed changes in position of surface plasmon resonance band depending on used solvent. To analyze these changes, absorption spectra were modelled using Mie theory for small spherical particles. The experimental and theoretical resonance values were compared to those predicted by Drude model and its limitations in the analysis of absorption behaviour of Ag NP in organic solvents are briefly discussed

Optical and structural characterization of polyaniline-gold nanocomposite

Nanocomposites based on conducting polymer and metal nanoparticles are very advantageous nanostructures due to their unique optical and conductive properties, offering the opportunity for many nanotechnological applications. In the present work, we report polyaniline – gold nanocomposite (PANI/Au) obtained by “in situ” chemical synthesis route. The chloroaurate ions (AuCl4 -) are used as an oxidant for the oxidative polymerization of aniline leading to the formation of gold nanoparticles together with polyaniline. Furthermore, the gold nanoparticles act as nucleation sites for the oxidative formation of PANI, encapsulating the metal in the form of a polymer/metal composite. Characterization of the samples, performed with UV-Vis and FTIR spectroscopy and XRD technique are used for description of the optical and structural properties of PANI/Au nanocomposite. Results from the FTIR spectra of the composite material are consistent with PANI produced using only ammonium persulfate as the oxidant. On the other hand, UV-Vis results indicate that the optical properties can be tailored from PANI

A simple two-phase route to polyaniline/gold nanocomposites

Combining the electrical, optical, and magnetic properties of polyaniline (PANI) with excellent chemical and physical properties of gold nanoparticles (Au NPs) is an efficient way to create novel functional nanomaterials with potential applications in biosensing and therapy, energy conversion and storage. In the present work, we report polyaniline/gold nanocomposite (PANI/Au) obtained by two-phase, water/toluene, interfacial chemical reaction. The polymerization process occurs at the interface of the organic phase (with aniline) and acidic water solution (with oxidant and Au NPs). Using this strategy, secondary growth of PANI could be suppressed. Transmission and scanning electron microscopy measurements were confirmed that PANI was formed as nanofibers decorated with 17 nm Au NPs. Characterization of the samples performed with UV-Vis and FTIR spectroscopy and XRD technique are used for description of the optical properties, interaction between components and structure of PANI/Au system. The obtained results indicate that the present synthetic route produces the PANI in conductive form (doped emeraldine salt form) with specific electric behavior, which makes PANI/Au nanocomposite suitable material for a wide range of applications

Optical and structural characterization of silver/polystyrene nanocomposites by in-situ bulk radical polymerization

Nanocomposites (NCs) with different amount of silver nanoparticles (Ag NPs) embedded in polystyrene (PS) matrix were prepared by in situ radical polymerization. In order to achieve homogeneous distribution of Ag NPs in the PS matrix, the nearly monodisperse Ag NPs (7.0 ± 1.5 nm) protected with oleylamine were first synthesized via organic solvothermal method and further used as a filler. For this purpose, a simple colloidal method for preparation of Ag NPs in organic solvent was developed. PS was selected as the polymer matrix based on its optical transparency and high chemical resistance. The gel permeation chromatography (GPC) measurements showed that the presence of Ag NPs stabilized with oleylamine during the polymerization of styrene have no influence on the molecular weight and polydispersity of the PS matrix. The structural properties of the resulting Ag/PS NCs were characterized by transmission electron microscope and FTIR spectroscopy. The influence of the presence of Ag NPs and their concentration on the optical properties of PS matrix was investigated in details using UV-Vis spectroscopy. Since the PS represents a nonabsorbing medium throughout the visible spectrum, the improvement of the optical performances of polymer was achieved by incorporation of the appropriate size Ag NPs with strong plasma resonance absorption

Optical properties of nanocomposite films based on Ag/PMMA system

As continue of our previous studies, three silver organosols with different nanoparticles sizes were used to obtain nanocomposite films based on Ag/PMMA system. Among polymeric materials, PMMA is well known as a polymeric glass and engineering plastic with a wide range of applications. One of the objectives of this work is to gain better insight into the properties of this material upon incorporation of small amount of silver nanoparticles. Silver nanoparticles were synthesized in various organic solvents (toluene, 1.2- dichlorobenzene ) in order to obtain different sizes of nanoparticles: 7.2 ±2.8 nm, 13.7±2.7 nm and 22.7±3.5 nm. By varying the heating temperature, solvent and reaction time, we could control the size of nanoparticles. In the second step, nanocomposites Ag/PMMA were prepared by in-situ bulk polymerization of methyl methacrylate in the presence of appropriate amount of silver nanoparticles. The size distribution and morphology of the silver nanopaticles in the nanocomposite films were determined using TEM measurements. The influence of size and dielectric property of surrounding media on surface plasmon absorption band of silver nanoparticles are discussed. UV-vis and FTIR spectroscopy have been applied to support the change in the optical and chemical properties of the silver organosols, as well as transparent and coloured Ag/PMMA nanocomposite films

Electrocatalityc application of gold-polyaniline nanocomposite

Gold‒polyaniline (AuPANI) nanocomposite, with granular morphology of PANI and rod‒like Au nanoparticles (NPs) as dominate structure distributed in it, was prepared by interfacial polymerization method in an immiscible water/toluene biphasic system. Simultaneously with the aniline polymerization to polyaniline (PANI) by HAuCl4, as an oxidant, AuNPs are formed. AuPANI composite as green precipitate is collected from aqueous phase. Polyaniline in the composite is in the conductive emeraldine salt form (PANIES), with high amount of Au (28.85 wt %). Nanocomposite showed great electrocatalytic activity towards the electrochemical O2reduction reaction (ORR), with high ORR onset potential and high selectivity for O2reduction to water. This makes it a good candidate for a new class of Pt‒free ORR catalyst.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 2016

Antibacterial activity of copper nanoparticles

Copper nanoparticles (CuNPs), with an average particle size of about 5 nm, was prepared by the simple chemical reduction procedure. TEM and UV– Vis spectroscopy contributed to the analysis of size and optical properties of CuNPs, and their antibacterial activity was evaluated toward human pathogenic bacteria Escherichia coli and Staphylococcus aureus, in a concentration dependent manner. The changes in the cell membrane morphology of tested strains were investigated by atomic force microscope (AFM), after 2 h of their contact with CuNPs. It was found that CuNPs cause different types of cell membrane disruptions, as well as that S. aureus bacteria were slightly resistant to the cell membrane damage than E. coli