AppNano – Applied NanoStructures

Abstract:
In this Letter, we investigate the nanomechanical properties of self-assembled 1,3,5-benzenetrisamide whiskers with atomic force microscopy (AFM) bending experiments. We use force mapping to acquire spatially resolved force measurements over the full length of a whisker segment spanning a channel of a structured glass substrate. This allows validation of the experimental boundary conditions directly from the AFM data and a reliable determination of Young’s modulus. The presented technique can be generalized for the mechanical characterization of other one-dimensional materials.

Abstract:
Electrochemically-assisted deposition of sol–gel materials can be locally confined at Pt nanoparticles. Pt nanoparticles have been locally deposited on glassy carbon surfaces by pulse electrodeposition using a droplet cell. Upon applying a potential for electrochemically-assisted deposition, the formed sol–gel film mirrors the region of the glassy carbon surface previously modified with Pt nanoparticles.
Research Highlights

• Controlled and local synthesis of composite materials by means of a sequential two-step process.
• Local deposition of sol–gel materials by means of electrocatalytic induction of pH modulation at Pt nanoparticles.
• Droplet cell for localized Pt nanoparticle deposition on glassy carbon.

Keywords: Electrocatalysis; Hydrogen evolution reaction; Pt nanoparticles; Sol–gel; Electrochemically-assisted deposition

Abstract:
Hollow polymeric capsules prepared from Layer-by-Layer coating of colloidal templates with polyelectrolyte multilayers are promising materials for drug delivery and release applications. Details of the wall structure arising from the core dissolution process are investigated by high resolution scanning electron microscopy (SEM), using both secondary (SE) and backscattered electron (BSE) imaging modes. Atomic force microscopy (AFM) of the capsules in liquid was used as an independent technique. BSE images of the coated templates may be used for a rough estimation of the wall thickness. A freeze-drying procedure allows for the first time the investigation of dried multilayer capsules with an intact shape by SEM. Details of the nanostructure of the capsule walls are obtained, the topography shows structures on the scale of several 10 nm, corresponding to single chains. These structures are confirmed by AFM in liquid. In addition, after core dissolution single holes with sizes above 10 nm can be identified in the capsule wall. These holes are the structural property controlling the permeation and release and are here visualized for the first time. The number of holes per capsule as well as their distribution and size are analysed and discussed in their relevance for release applications.

Abstract:
A new, extremely efficient method for the fabrication of films comprised of gold nanoparticles (GNPs) crosslinked by organic dithiols is presented in this paper. The method is based on layer-by-layer spin-coating of both components, GNPs and crosslinker, and enables the deposition of films several tens of nanometers in thickness within a few minutes. X-ray diffraction and conductance measurements reveal the proper adjustment concentration of the crosslinker solution of the critical is in order to prevent the destabilization and coalescence of particles. UV/vis spectroscopy, atomic force microscopy, and conductivity measurements indicate that films prepared via layer-by-layer spin-coating are of comparable quality to coatings prepared via laborious layer-by-layer self-assembly using immersion baths. Because spin-coated films are not bound chemically to the substrate, they can be lifted-off by alkaline underetching and transferred onto 3d-electrodes to produce electrically addressable, freely suspended films. Comparative measurements of the sheet resistances indicate that the transfer process does not compromise the film quality.