The crystals that I am synthesizing use two different stabilizers CTAB and SDS, but they say one is used as a surfactant and since they are both stabilizers what is the need for both?
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CTAB is a cationic surfactant, SDS is an anion surfactant.
These surfactants act to selectively stabilize ionic faces on the crystal as it grows, causing those faces to grow more rapidly. This leads to a change in geometry or crystal shape. CTAB causes one morphology being cationic, while SDS will cause another, its head ion having the opposite charge. Further, a mixture of the two will cause an intermediary morphology.
For instance, CTAB will cause an aqueous solution of thioacetamide and Lead(II) acetate to form PbS nanocrystals in a octahedron shape, while SDS will cause them to form a dendritic fern like shape, while a CTAB/SDS mixture (5:1) will cause a stellated octahedron or star shape to form.
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$\begingroup$ Thank you for the help. I am actually fabricating PbS NC's for my senior project. Maybe you can explain to me or send my in the right direction how EDTA, SDS, CTAB, lead acetate and thiorea solution facilitate the formation of these NCs when only heated to 70 degrees C. Any information helps $\endgroup$– user4505Feb 24, 2014 at 20:48
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$\begingroup$ Low-Temperature Synthesis of Star-Shaped PbS Nanocrystals in Aqueous Solutions of Mixed Cationic/Anionic Surfactants $\endgroup$ Feb 25, 2014 at 15:04