This "close companion" of our SO3- product has been used for oriented growth of calcite, vaterite and aragonite crystals on SAMs (J. Am. Chem. Soc.121, 4500-4509, 1999; J. Mat. Chem.8, 641-650, 1998), for functionalization of nanoparticles for heavy-metal removal (Mat. Res. Soc. Symp. Proc.847, 305-310, 2005), and for self-assembly of multilayer structures through zirconium bridging (Langmuir6, 1567-71, 1990). In addition, since the phosphonic group has two pKa's (pKa1=0.9 and pKa2=5.6) this thiol is an interesting candidate for making pH-sensitive SAMs.