Self-Assembly of Uniform Monolayer Arrays of Nanoparticles

Abstract

Five nanometer diameter gold particles encapsulated by alkanethiol molecules have been self-assembled into well-ordered monolayers on a water surface, and these nanoparticle films have been transferred intact onto various solid substrates. The method involves spreading a thin layer of an organic solvent containing the gold nanoparticles on a water subphase that has a controlled surface curvature. As the solvent evaporates, a nanoparticle monolayer free of microscopic cracks and voids nucleates at the center of the apparatus and grows radially outward until it covers practically the entire water surface. This monolayer is transferred from the water surface to a polydimethylsiloxane (PDMS) stamp pad by the Langmuir-Schaefer (LS) technique and is applied to the solid substrate by microcontact printing (µCP). Uniform centimeter-scale films have been produced with this method. The quality of the transferred films has been verified by transmission electron microscopy (TEM). The nanoparticle monolayer is a hexagonal close-packed array with a center-to-center spacing that is approximately equal to the sum of the diameter of the gold particles and twice the height of a self-assembled monolayer (SAM) of the alkanethiol molecules on Au(111). The transferred films are free of multilayer regions and of microscopic voids and grain boundaries over their entire area and exhibit crystalline order across the openings in the TEM grid (∼4000 µm 2 ).

Surface-Enhanced Raman Scattering from Oleate-Stabilized Silver Colloids at a Liquid/Liquid Interface

“…In recent years, this kind of interfacial aggregation was applied to prepare nanoselfassemblies in nanotechnology, where hexagonal closepacked arrays were prepared at solid/liquid and liquid/liquid interfaces. 13,14 The silver colloid surfaces in the present study were covered with oleate anions, which made the surface negatively charged and prevented coagulation of the colloids. The oleate ions worked not only as a stabilizer of silver colloids, but also as an extractant of colloids from the aqueous phase to the organic phase.…”

Challenges and breakthroughs in recent research on self-assembly

“…The nanowires retain the width of the initial PbS nanowires after alignment with an average diameterý of 1.8 ± 0.08 nm and pitch of 2.7 ± 0.08 nm. Similarly LB methods were used for assembly of nanoparticles [984][985][986][987][988][989][990][991][992], nanowires and nanorods [993][994][995][996][997][998][999], and quantum dots [1000].…”

From supramolecular chemistry to nanotechnology: Assembly of 3D nanostructures

“…In their earlier work, micropatterns of palladium nanoparticles were prepared by μCP, which served as a catalyst for electroless deposition of copper (Scheme 2.11). 73 74,75 Dense and hexagonally packed monolayers of nanoparticles were first assembled on a water surface. By using the Langmuir-Schäfer technique, the Au nanoparticle monolayer was transferred to a PDMS stamp, and printed onto a substrate.…”