Fascinating control of crystalline microstructures

Crystalline tubes can be produced by immersing certain hydrate crystals in an antisolvent and thereby inducing a phase transformation. The tube diameter as well as the growth rate of the example sodium-2-keto-l-gulonate anhydrate (skga), which occurs during the dehydration of sodium-2-keto-l-gulonate monohydrate (skgm) in an antisolvent (methanol), was controlled by changing the initial antisolvent composition. The outer diameter of skga anhydrate needles can be decreased from about 7 μm to 300 nm by increasing the water content in the antisolvent. Furthermore, it was observed that the temperature at which the transformation is carried out does not have a significant influence upon the diameter of the skga tubes. The dehydration of skgm in other antisolvents (e.g. ethylene glycol) also results in the growth of needles (transformation skgm to skga).Moreover, first results for closed tubes (containers) generated from the needles are presented in this work.