TEMPLATED CRYSTALLIZATION OF CALCIUM AND STRONTIUM CARBONATES ON CENTERED RECTANGULAR SELF-ASSEMBLED MONOLAYER SUBSTRATES

The calcite and vaterite modifications of CaCO3 possess threefold symm etry axes in their crystal structures, while the aragonite modificatio n does not. Since many self-assembled monolayers (SAMs) of simple thio ls on gold organise in a hexagonal close-packed manner, patterns for t he templated crystallisation of the first two polymorphs on SAMs are s imple to achieve. This is not true in the case of aragonite. A substit uted disulphide derived from anthracene-2-carboxylic acid, which has b een previously established as forming centred rectangular lattices whe n assembled on a gold (111) surface, has therefore been employed to fo rm substrates for the crystallisation of CaCO3 with the specific inten tion of preferentially inducing the growth of aragonite. For compariso n, we have also performed such crystallisations on a SAM substrate der ived from hexadecane thiol, While the crystallisation of the CaCO3 pol ymorphs is invariably accompanied bg the problem of competing phases, SrCO3 crystallises from solution uniquely in the strontianite modifica tion, which is isostructural with aragonite. We have thus performed th e crystallisation of SrCO3 as well and present the results.