Incorporation of surface-derivatized gold nanoparticles into electrochemically generated polymer films

Polymethylolacrylamide/AuNPs Nanocomposites: Electrochemical Synthesis and Functional Characteristics

In this study the advantages of the electrochemical approach to the formation of polymer/metal nanoparticle composites are demonstrated. The method enables one to simplify the multistage processes of traditional technologies for the production of such materials through combining all intermediate processes in one stage and reducing the total formation time to 3–10 min. The possibility of a single-stage formation of a polymethylolacrylamide/AuNPs composite through including AuNPs into an electrically non-conducting polymethylolacrylamide film (carrier) formed by electropolymerization through potentiostatic electrolysis is also demonstrated for the first time. It is established that the addition of tetrachloroauric acid (HAuCl₄·4H₂O) into a monomeric composition containing acrylamide, formaldehyde, N,N′-methylene-bis-acrylamide, zinc chloride, and H₂O results in simultaneous electrochemical initiation of polymerization with the formation of a polymer film on the cathode, electrolytic reduction of gold ions to Au⁰, and immobilization of AuNPs particles into the growing polymer matrix. It was found that the formation of the PMAA / AuNPs composite is energetically more favorable than the synthesis of the main PMAA film, since it proceeds at a lower cathodic potential. The inclusion of AuNPs into the polymethylolacrylamide film was confirmed visually, as well as by X-ray phase analysis, small-angle X-ray scattering, microscopy, and element analysis. The gold content in the composite increases along with the increase of the concentration of HAuCl₄ in the electrolyte. The radius of the AuNPs particles was found to range between 3 and 7 nm. The AuNPs particles are spherical in shape and can combine into larger clusters containing up to 10 or more particles. The dynamics of formation, structure, and morphology of the polymethylolacrylamide/AuNPs composite were investigated. It was revealed that gold nanoparticles are mainly concentrated in the near-electrode and near-solution layers of the composite. We found that the composite has electrocatalytic activity. The possibility of its use as a sensor for hydrogen peroxide is demonstrated.

Light-induced modification of silver nanoparticles with functional polymers

Light coating: Ag–polymer core–shell nanoparticles were prepared using photoenol-based light-induced ligation.

Effect of composition on the conductivity and morphology of poly(3-hexylthiophene)/gold nanoparticle composite Langmuir–Schaeffer films

Ultrathin Langmuir-Schaeffer (LS) films were fabricated from blends of regioregular poly(3-hexylthiophene) (P3HT) and highly monodispersed dodecanethiolate-capped gold nanoparticles (Au NPs) mixed in varying weight ratios. The morphology of the ultrathin films was investigated by UV-visible absorption spectroscopy, atomic force microscopy (AFM) and field-emission scanning electron microscopy (FE-SEM). The results of the structural investigations were correlated with the lateral conductivity of the films, with P3HT in its unintentionally doped state, probed by scanning electrochemical microscopy (SECM), which proved to be a very sensitive technique. Control over the P3HT/Au NP ratio led to remarkable changes in the morphology and lateral conductivity of the films. Inclusion of Au NPs into P3HT was found to influence the ordering of P3HT, which ultimately determined the macroscopic charge transport characteristics of the films. Composite films with ca. 33% by weight of Au NPs were found to be the most ordered and exhibited the highest conductivity, substantially higher than P3HT alone. To provide insight into the film formation process, LS composite films comprising equal quantities of P3HT and Au NPs (by weight) were transferred at several surface pressures and investigated by SECM, AFM and FE-SEM.

Molecular Ordering and 2D Conductivity in Ultrathin Poly(3-hexylthiophene)/Gold Nanoparticle Composite Films

This paper reports the first comparison of the structure and electrical conductivity properties of spin cast (SC) and Langmuir-Schaeffer (LS) films of regioregular poly(3-hexylthiophene) (P3HT). In addition, the effect of incorporating highly monodisperse Au nanoparticles (NPs), with a core diameter of approximately 5 nm, into SC and LS P3HT films is described. A detailed picture of molecular organization in the films has been obtained using ultraviolet-visible absorption spectroscopy, atomic force microscopy, field-emission scanning electron microscopy, X-ray diffraction, and X-ray reflectivity. Film morphology was correlated with pseudo-two-dimensional conductivity measured using scanning electrochemical microscopy, with P3HT in the semiconducting regime. It was found that SC films, which were slightly thicker than those formed with the LS technique, exhibited greater organization. This resulted in an order of magnitude higher lateral conductivity for the SC films. Inclusion of Au NPs (50 wt %) into both SC and LS films resulted in the formation of uniform and relatively flat (rms roughness approximately 1 nm) composite films. Surprisingly, the addition of NPs did not disrupt the characteristic crystal structure found for the native P3HT films. The effect of Au NPs on film lateral conductivity was found to be determined by the distribution of Au NPs within the polymer, which varied significantly between SC and LS films. Whereas Au NPs aggregated into hexagonally packed clusters in SC films, NPs in LS films were predominantly uniformly distributed between the lamella bilayer. It was found that, while the inclusion of Au NPs caused the lateral conductivity to decrease in SC films, in LS films, the lateral conductivity increased by a factor of 2.

Photofragmentation of Phase-Transferred Gold Nanoparticles by Intense Pulsed Laser Light

Gold nanoparticles with an average diameter of approximately 20 nm were prepared in an aqueous solution by a wet chemistry method. The parent gold nanoparticles were then capped with a 4-aminothiophenol protecting layer and transferred into toluene by tuning the surface charge of the modified nanoparticles. Gold nanoparticles before and after phase transfer were subjected to photofragmentation by a pulsed 532 nm laser. The effects of solvent properties and surface chemistry on the photofragmentation of the gold nanoparticles have been investigated. Fast photofragmentation has been observed in the organic solvent in which the dielectric constant, heat capacity, and thermal conductivity are lower. The results suggest new approaches for the preparation of very small gold clusters from gold nanoparticles.

Electrochemical nucleation of gold nanoparticles in a polymer film at a liquid-liquid interface

Simultaneous nucleation of gold nanoparticles and polymerization of tyramine has been carried out at an immiscible electrolyte interface. By transferring the gold ion of tetraoctylammoniumtetracloroaurate (TOAAuCl(4)) from the organic to the aqueous phase, a fast homogeneous electron transfer from the tyramine monomer reduces the gold ion. Electropolymerization then proceeds, and gold nanoparticles form. The newly formed nanoparticles act as nucleation sites for the deposition of the oligomers/polymer (and possibly vice versa). This results in gold nanoparticles stabilized in a polytyramine matrix. The size of the nanoparticles is controlled by the concentration of oligomers/polymer in solution. The polymer nanoparticle composite film was analyzed with TEM, XPS, and AFM.

Metal nanoparticle—conjugated polymer nanocomposites

Recent literature describing nanocomposites of metal nanoparticles and conjugated polymers and oligomers are reviewed. Preparation of these nanocomposites by chemical and electrochemical methods are described, and the electronic and optical properties of these materials are discussed. Some initial applications that have been investigated for such nanocomposites are covered.

Monolayer-Protected Au Cluster (MPC)-Supported Ti−BINOLate Complex

[reaction: see text] Disulfides bearing (R)-1,1'-bi-2-naphthol ((R)-BINOL) moieties at each terminal position have been successfully introduced on the surface of Au cluster. Ti-BINOLate complex generated from the obtained monolayer-protected Au cluster (MPC) promoted catalytic asymmetric alkylation of benzaldehyde with Et(2)Zn to afford the adduct in up to 98% yield with 86% ee. After completion of the reaction, the BINOL-functionalized MPC was easily recovered.