High Enantioselectivity in Adsorption of Chiral Molecules on the Surface of Chiral Terbium Phosphate Nanocrystals

The enantioselective adsorption (and catalysis) of molecules on chiral surfaces has been a topic of interest, in particular with respect to models describing homochirality in the evolution of life. While such adsorption on single crystal surfaces has been studied using various traditional surface science techniques, similar studies on powders have been less successful. Here we show that studying enantioselective adsorption on the particular system of intrinsically chiral TbPO₄·H₂O nanocrystals (chiral space group) is highly useful and obeys some simple rules. The advantages of this system are the ability to produce such nanocrystals with 100% enantiomeric purity with virtually no ligands, due to strong autocatalytic effects in their enantioselective nucleation, and the prevalence of one type of surface type (100) in the formed nanocrystals. We show that particular chiral molecules such as tartaric and aspartic acids exhibit significant enantioselectivity in adsorption, while similar ones, like glutamic acid, show none. We demonstrate that at least three functional groups are required to define enantioselective adsorption, and in addition, there should be matching of distances between these groups and the corresponding surface adsorption sites (Tb³⁺ sites in our case).