  Fabrication of silver nanowires (AgNWs) with fine and independent control of
both the diameter (from 30 to 120 nm) and length (from 5 to 120 $\mu$m) by
concomitant addition of co-nucleants and temperature control is demonstrated,
and used for the preparation of size standards. Percolating random networks
were fabricated using these standards and their optoelectronic properties were
measured and compared with regard to the nanowire dimensions. The transparent
electrodes appear suitable for various applications and exhibit excellent
performances (e.g. 16 ohm sq --1 at 93% transparency), with haze values varying
from 1.6 to 26.2%. Besides, in vitro toxicological studies carried out on
murine macrophages with the same size standards revealed that AgNWs are weakly
toxic (no toxicity observed below 50 $\mu$g mL --1 Ag), in particular compared
to other silver nanoparticles. Short AgNWs (4 $\mu$m) appeared to be slightly
more toxic than longer AgNWs (10 and 20 $\mu$m). Conversely, long AgNWs (20
$\mu$m) induced a more prolonged pro-inflammatory response in murine
macrophages. These results contribute, in a safer by design approach, to
promoting the use of short AgNWs. The global knowledge dealing with the
combination of nanowire dimensions associated with optoelectronic performances
and related toxicity should encourage the rational use of AgNWs, and guide the
choice of the most adequate AgNW dimensions in an integrated approach.
