When small is better

Makiura and coresearchers have shown how a canonical high-temperature Ag+-ion conductor can be manipulated to produce functional conduction under ambient conditions. This is achieved by forming small nanoparticles of AgI coated in a particular polymer that is also known for its ability to conduct Ag+ ions. The authors have synthesized nanoparticles of AgI coated with the polymer poly(N-vinyl-2-pyrrolidone). On being heated, these particles transform to the ion-conducting α-phase at the expected temperature of more than 140°C. The authors report that the high-temperature to low-temperature transition is suppressed over only a small range of particle sizes. Nanoparticles larger than this have properties much more similar to the bulk, suggesting that a very specific state is present at about 10 nm.