The preprint is available here.
What we have found is that ascorbic acid, widely used as a mild reducing agent, also plays a shape-directing role. These two actions are difficult to decouple, since a reductant is always needed to perform reduction reactions. The workaround we found was employing the reactive species generated by the electron beam in the observation cell.
The result is well captured by the following movies, recorded with and without ascorbic acid (all other things being equal.)
