No abstract

Citrate-stabilized gold nanoparticles 15 nm and 33 nm in diameter were transferred concomitantly with a monolayer of positively charged polyaniline by Langmuir-Blodgett transfer at pH 5 onto a conducting indium-doped tin oxide (ITO) support. Films consisting of one to three layers of polyaniline with thicknesses of 1-3 nm were prepared and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy. After electro-oxidation of the Au nanoparticles in 0.1 M KCl, cavities were left behind in the film that could be analyzed by SEM. These cavities were able to recapture analyte nanoparticles from a solution of pH 10 and showed size-exclusion properties. The amount of nanoparticles taken up by the cavities was conveniently analyzed by measuring the charge associated with the electro-oxidation of these particles in 0.1 M KCl after the film had been rinsed with water. The size-exclusion properties improved with the number of Langmuir-Blodgett layers transferred.

The Langmuir-Blodgett (LB) method was used for depositing cubic polyhedral oligomeric silsesquioxanes (T 8 POSS) onto Au, indium tin oxide (ITO) and mica supports. Three different T 8 POSS were examined; two were amphiphilic and aggregated upon transfer to a solid support, while the highly symmetric POSS (termed MP 8 ) gave stable and reproducible Langmuir films as studied by surface pressure and transfer ratio measurements. This was attributed to the eight identical alkanethiol groups located on each of the eight corners of the cubic like skeleton. The LB films were studied by RA-FTIR, XPS, contact angle and cyclic voltammetry. These techniques revealed the formation of a permeable, yet, stable layer. The symmetric MP 8 was utilized as a bridging building block between the support and Au nanoparticles (Au-NPs). This assembly was examined by means of AFM, SEM and anodic oxidation of the nanoparticles. An average density of 1.45 Â 10 9 nanoparticles cm À2 was obtained for the deposited Au-NPs on the MP 8 layer. Furthermore, anodic stripping voltammetry was used for studying the extraction of Hg 2+ by the MP 8 LB film.

Anisotropic CdS nanorods tipped by Au nanoparticles on one edge (Au-CdS-NRs) are perpendicularly oriented at the air/water interface, whereby all the Au tips are located in the subphase, using the Langmuir-Blodgett technique. Since these nano-objects reveal light-induced charge separation at the semiconductor/metal interface, it is of high interest to control their organization. The orientation of these assemblies is studied in situ while compressing the Langmuir-Blodgett trough using the π -A isotherm, Brewster angle microscopy, and horizontal touch voltammetry. All these analyses clearly confi rm the induced organization of the amphiphilic Au-CdS-NRs by compression of the Langmuir layer. The compressed layers are successfully transferred by the Langmuir-Schaefer method onto transmission electron microscopy grids while maintaining the preferential orientation as analyzed by transmission, scanning and scanning trasmission electron microscopy, and X-ray photoelectron spectroscopy. As far as can be determined, the Langmuir-Blodgett technique has not been used so far for perpendicularly orienting anisotropic nano-objects. Moreover, these fi ndings clearly demonstrate that anisotropic amphiphilic nano-objects can be treated with some similarity to the traditional amphiphilic molecular building blocks.

Capping CdS nanorods on one side with Au nanoparticles makes these asymmetric nano‐objects amphiphilic. As D. Mandler and co‐workers report in article 1300030, this enables the formation of 2D nanometric monolayers at the liquid/air interface using the LB technique. This interesting system is studied in situ by various methods, such as horizontal touch voltammetry as well as by ex situ approaches upon transferring the films onto solid supports