Catalytic Effect of Gold Nanoparticles Self-Assembled in Multilayered Polyelectrolyte Films

Abstract

Multilayer films composed of poly(l-arginine) (pArg) and mercaptoundecanoic acid (MUA) stabilized gold nanoparticles (Au−MUA NPs) have been fabricated based on the electrostatic layer-by-layer self-assembly technique upon a gold electrode modified with a first layer of mercaptosuccinic acid (MSA). The formation of the pArg/Au−MUA NP self-assemblies as alternative multilayers was confirmed by UV−vis absorption spectroscopy and atomic force microscopy while their electrochemical properties were studied using cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy. Charge transport through the multilayer was studied experimentally by using the redox pair [Fe(CN)6]3-/4-. It was found that these new assemblies have a high permeability to the probe ions. The presence of the Au−MUA NPs greatly improves the conductivity and the electron-transfer ability of the film which exhibited new electrical properties characterized by a low impedance response and enhanced electric current as more layers were added for both Au−MUA NP and pArg terminated multilayers. It is concluded that the behavior observed is based on two cumulative contributions: electron transfer mediated by the Au−MUA NPs layers and ionic diffusion favored by the poly(l-arginine) layers due to the Donnan inclusion. The films obtained showed high conductive properties which represent very promising features for the construction of electrochemical sensors or nanoelectronic devices.

Charge Transfer Within Multilayered Films of Gold Nanorods

“…The CdTe dots being very small (2.2nm, 2.5nm 2.9 nm) have slightly enhance mainly the reduction process. A size of 3nm or higher average diameters of the nanomaterials induces a higher enhancement of the electron transfer process as it was demonstrated in another report (Chirea et al, 2007). Table 3.…”

“…Various electrochemical techniques have been use for the investigation of the electron transfer processes taking place at hybrid nanostructured modified electrodes. Cyclic voltammetry, electrochemical impedance spectroscopy, square wave voltammetry, differential pulse voltammetry, potential step chronoamperometry and rotating disk electrodes are among the most used techniques for these electrochemical studies (Chen &Pei, 2001;Chirea et al, 2005Chirea et al, , 2007Hicks et al, 2002, Horswell et al,2003. Electrochemical impedance spectroscopy (EIS) has been proven as one of the most powerful tools for the investigation of interfacial electrode reaction mechanisms (Katz & Willner, 2003, Yan & Sadik, 2001, Lasia, A.…”

Hydrogen Bonding: A Bottom-Up Approach for the Synthesis of Films Composed of Gold Nanoparticles

“…For this reason, larger gold nanoparticles were synthesized by Turkevich method and successively functionalized with MUA, because the direct synthesis of gold clusters stabilized by MUA yields only clusters no larger than 4 nm. [3] Interestingly, after purification, filtration and drying, these large MUA functionalized gold clusters generated, spontaneously, soft solid films based on hydrogen bonding interaction as it will be proved further in this work. This behavior has not been observed previously for small gold nanoparticles (1-4 nm) stabilized by the same ligand.…”

Ion Transfer in Layer-by-Layer Films

“…When mercaptoundecanoic acid (MUA) stabilized gold nanoparticles are adsorbed layer-by-layer with poly(L-arginine), the films have shown a higher permeability for [Fe(CN) 6 ] 3-/4-couple at increasing layers. 51 The authors describe that the negative COOcharge becomes further away from nanoparticle surface which in turn helps reduce the www.intechopen.com repulsion between the redox species and negatively charged NPs. However, in (PMo 12 PDDA) 10 samples, the change in the microstructure of the films causes enhanced diffusion.…”

“…Silva et al have performed such EIS modeling in LbL films of polyelectrolytes 49,50 as well as gold nanoparticles. 38,51 Here, we first review the proposed models for gaining further insight in EIS modeling of LbL films. Followed, we will develop an EIS model to describe the mass transfer in functional LbL films.…”