Additive Induced Formation of Ultrathin Sodium Chloride Needle Crystals

• Published in: Crystal growth & design Vol. 18; no. 2; pp. 755 - 762
• Main Authors: Townsend, Eleanor R, van Enckevort, Willem J. P, Tinnemans, Paul, Blijlevens, Melian A. R, Meijer, Jan A. M, Vlieg, Elias
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07.02.2018
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.7b01170

A multitude of ultrathin crystal needles are formed during the evaporation of saturated aqueous NaCl solution droplets in the presence of amide containing additives. The needles are as small as 300 nm wide and 100–1000 μm in length. Heating experiments, X-ray diffraction, and energy dispersive X-ray spectroscopy showed that the needles are cubic sodium chloride crystals with the needle length direction pointing toward [100]. This shape, not expected for the 43̅m point group symmetry of NaCl, has been explained using a model, based on tip formation by initial morphological instability followed by time dependent adsorption of additive molecules blocking the growth of the needle side faces. The latter also suppresses side branch formation, which normally occurs for dendrite growth.