Low-temperature preparation of highly conductive thin films from acrylic acid-stabilized silver nanoparticles prepared through ligand exchange.

The preparation of AcA-stabilized Ag nanoparticles and its application to make highly conductive thin films are reported. The AcA-stabilized Ag nanoparticles were prepared through a ligand exchange of original oleylamine (OLA)-coated Ag nanoparticles with acrylic acid (AcA), which acted as both an antisolvent and a modifying ligand during the ligand exchange process. Efficiencies of the ligand exchange as well as the properties of Ag nanoparticles were analyzed using various techniques including TEM, FT-IR, XPS, TGA, and UV-vis methods. The thin films were fabricated by annealing spin-coated AcA-stabilized Ag nanoparticles. Further, the effects of annealing temperature, time, and film thickness on both the film morphology and electrical conductivity have been investigated. In this work, due to the low boiling temperature of stabilizer (AcA) and adjustment of annealing conditions, high electrical conductivity was obtained for the Ag thin films. For example, when annealing at 175 °C for 30 min, a 70 nm thick film showed a maximum electrical conductivity of 1.12 × 10(5) S cm(-1). A conductive layer on a flexible polymer substrate (e.g., PET) sheet has been successfully prepared by annealing a spin-coated film at 140 °C for 30 min. The combined advantages of long-term stability of the AcA-stabilized Ag nanoparticles, low annealing temperature, and high conductivity of the prepared thin films make this relatively simple method attractive for applications in flexible electronics.

Surface modification of hydrophobic nanocrystals using short-chain carboxylic acids.

Acrylic, acetic and methacrylic acids which are short-chain carboxylic acids have been applied to modify the surface of oleic acid-coated TiO(2) nanorods (NRs) and oleic acid/oleylamine-coated Fe(3)O(4) nanoparticles (NPs). The short-chain carboxylic acids not only acted as modifying ligands but also as anti-solvents during the ligand exchange processes. The prepared products have been characterized using TEM, HRTEM and FTIR spectroscopy. The results show that the acrylic acid-exchanged TiO(2) and Fe(3)O(4) solution remain stable even after six months, showing no agglomeration. Such acrylic acid-exchanged nanocrystals (NCs) prepared in this work could also be well-dispersed in other polar solvents such as ethanol and ethanol/water mixtures. On the contrary acetic acid and methacrylic acid-exchanged TiO(2) solutions were not stable due to the presence of remaining oleic acid on the TiO(2) surface. This approach has been shown to be effective in making hydrophilic TiO(2) NRs and Fe(3)O(4) NPs and can also be applied to other NCs covered by different hydrophobic ligands.