Here, monolayer‐protected gold and silver nanoparticles with extremely high solvent dispersibility (over 200 mg mL−1 in water and glycols) and low coalescence temperature (approximately 150 °C, measured by the percolation transition temperature Tp) are developed, to reach conductivities better than 1 × 105 S cm−1. These materials are suitable for inkjet and other forms of printing on substrates that may be solvent‐ and/or temperature‐sensitive, such as for plastic electronics, and as bus lines for solar and lighting panels. This is achieved using a new concept of the sparse ionic protection monolayer. The metal nanoparticles are initially protected by a two‐component mixed ligand shell comprising an ω‐functionalized ionic ligand and a labile ligand. These are selectively desorbed to give a sparse shell of the ω‐ionic ligands of ca. 25% coverage. Through a systematic study of different monolayer‐protected Au nanoparticles using FTIR spectroscopy, supported by XPS and DSC, it is shown that Tp is not determined by thermodynamic size melting or by surface area effects, as previously thought, but by the temperature when ca. 80% of the dense monolayer is eliminated. Therefore, Tp depends on the thermal stability and packing density of the shell, rather than the size of the metal core, while the solubility characteristics depend strongly on the exposed terminal group.
Single wall carbon nanotubes (SWNTs) are considered to be one of the potential candidates for the production of transparent conducting films (TCFs), which can be used in many applications, e.g., touch panels, displays, and polymer solar cells. However, for making optimum usage of the superior properties of SWNTs, a better understanding on the processing and fabrication of thin films is essential. In this work, the effects of the purification conditions of SWNTs, the stability of their dispersions as a function of pH, and the performance of TCFs fabricated from dispersions of different pH are studied. The figure of merit s dc /s oc for such films can be increased by factor of 2 when the pH of the SWNT dispersion is increased, i.e., the optical and electrical performance is improved significantly. We also report the surface charge-manipulated transformations in transparent conducting films fabricated from SWNT dispersions of different pH values.
A layered composite coating material with favorable properties for application as a transparent conductor is presented. It is composed of layers of three nanoscopic materials, namely zinc oxide nanoparticles, single wall nanotubes, and graphene oxide nanosheets. The electrically conducting layer consists of single wall nanotubes (SWNTs). The layer of zinc oxide nanoparticles acts as a primer. It increases the adhesion and the stability of the films against mechanical stresses. The top layer of graphene oxide enhances the conductivity of such coatings. Such three-layer composite coatings show better conductivity (without compromising transparency) and improved mechanical stability compared to pure SWNT films. The processes used in the preparation of such coatings are easily scalable.
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