Langmuir−Blodgett Films of Carboxylic Acid Derivatized Silver Colloidal Particles:  Role of Subphase pH on Degree of Cluster Incorporation

Abstract

In this paper, we demonstrate that reasonably ordered multilayer films of silver clusters can be deposited by the Langmuir−Blodgett (LB) technique. The approach consists of electrostatically immobilizing negatively charged carboxylic acid derivatized silver colloidal particles at the air−water interface using positively charged fatty amine Langmuir monolayers. The degree of cluster incorporation into the Langmuir monolayer has been controlled by varying the charge on the amine molecules through the colloidal subphase pH. Pressure−area isotherms were used to follow adsorption of the silver colloidal particles at the amine surface, while quartz crystal microgravimetry (QCM), optical absorption spectroscopy, infrared spectroscopy, contact angle measurements, and optical interferometry were used to characterize the multilayer LB films. The films were found to grow in the classical Y-type mode. Optical interferometry indicated a bilayer thickness of 106 Å, which yields a cluster size of ∼55 Å, in reasonable agreement with a mean cluster size of 73 Å determined from transmission electron microscopy. Incorporation of clusters into inorganic matrices as outlined in the paper shows promise for the growth of superlattice structures, mixed cluster systems, etc., which are not realizable by currently used experimental methods.

Nanoparticle Organization at the Air‐Water Interface and in Langmuir‐Blodgett Films

“…At this pH, the ODA monolayer is uncharged and consequently the driving force for surface assembly is absent [85]. Similar variation in the pH-dependent complexation of silver [76,78], gold [84] and small SiO 2 and TiO 2 nanoparticles with ODA monolayers [87] have been made, thereby strengthening the electrostatic interaction model proposed.…”

“…12.10). The kinetics of complexation of the nanoparticles is slow, often requiring 15 h for nanoparticle equilibration at the air-water interface as observed in the case of 4-CTP-capped silver particles [76]. The fact that the interaction between the CdS nanoparticles and the ODA monolayer is electrostatic in nature was established by the fact that no nanoparticle complexation was observed when the CdS subphase was maintained at pH 12.…”

Monolayer/bilayer transition in Langmuir films of derivatized gold nanoparticles at the gas/water interface: An x-ray scattering study

“…One of the more complex methods that have been used is based on attractive interactions between colloidal nanoparticles in an aqueous solution and a charged surfactant monolayer at the solution/air interface. 20,[43][44][45][46][47][48] In this approach, nanoparticles form a monolayer of their own just below the surfactant monolayer, and the composite film thus formed is transferred onto a solid support by the LB method. Finally, more recent studies have explored the formation of nanoparticle monolayers at liquid/liquid interfaces, [49][50][51] and some of these films have also been transferred onto solid substrates.…”

Thin Films of Ag Nanoparticles Prepared from the Reduction of AgI Nanoparticles in Self-Assembled Films

“…A variety of methods have been proposed for the preparation of uniform films of Ag nanoparticles, such as physical deposition (14), electrochemical deposition (15,16), the LangmirBlodgett technique (17), and the layer-by-layer self-assembly method (18)(19)(20)(21)(22)(23). In addition, in applications of microelectronics or microsensors, patterned assembly of nanoparticles is of paramount importance (4).…”