Reorganization of Au nanoparticle Langmuir-Blodgett films on wet chemically passivated Si(001) surfaces

Abstract

Surface correlation behaviors of metal-organic Langmuir-Blodgett films on differently passivated Si(001) surfacesGrowth of dodecanethiol-encapsulated Au nanoparticles on differently terminated (OH-, H-, or Br-terminated) Si(001) substrates by Langmuir-Blodgett method at a constant monolayer surface pressure and their out-of-plane structural modification with time have been investigated. As the substrates have different gradations in the hydrophilic/hydrophobic nature, three different out-of-plane structures have been formed. On H-terminated Si (hydrophobic surface), a fluctuating monolayer of Au nanoparticles has been formed, whereas on Br-(coexistence of hydrophilic and hydrophobic surfaces) and OH-terminated Si (hydrophilic surfaces), trilayer of Au nanoparicles have been formed, but the top layer coverage is more for the OH-terminated Si. The growth of Au nanoparticles on H-terminated Si is similar to the Frank-van der Marwe mode, whereas on Br-and OH-terminated Si, the growth is similar to the Stranski-Krastanov mode. These three different structures modify with time and finally become a thicker monolayer of high density, and positions of naoparticles within the monolayer become random. AFM images of the films also show that positions of the Au nanoparticles are random. Density of the final layer becomes maximum on OH-terminated Si and minimum on H-terminated Si, whereas it becomes intermediate on Br-terminated Si. Reorganization thus helps to obtain nanostructures of tunable nanoparticle density.

QDs Supported on Langmuir‐Blodgett Films of Polymers and Gemini Surfactant

“…In an attempt to interpret this behavior, we analyzed the ability of QDs to wet the different molecules employed as substrate coating by means of the spreading parameter. The spreading parameter has been used previously in LB Journal of Nanomaterials films to evaluate their stability [58] and to interpret the nanostructures formed by nanoparticles deposited onto different substrates [59]. Therefore, we analyzed the spreading parameter indicative of the balance between QDs and the coating layer (adhesive forces) and QD-QD (cohesive forces) intermolecular forces.…”

Langmuir and Langmuir–Blodgett Films of Gold and Silver Nanoparticles

“…However, Si surfaces terminated with hydrophilic groups (Br and OH) reduced the E s–n interaction, meaning that the E n–n interactions dominated, thus leading to the formation of trilayers of Au NPs upon dewetting. The coverage of each successive layer increased with the hydrophilicity of the substrate …”

Prolonged reorganization of thiol-capped Au nanoparticles layered structures

“…[24][25][26][27] For the organic capped nanoparticles, which are effectively hydrophobic in nature the growth, structure and stability on differently passivated Si surfaces have been studied. 28 Differently passivated Si surfaces have different hydrophilic/hydrophobic nature, which effectively controls the growth and stability of the nanoparticle films. Due to the reorganization for nearly two months, close packed layered structure has been observed.…”

“…26,28 Immediately after the chemical treatment, all the substrates were kept inside the Milli-Q water until LB deposition.…”