1. A method for preparing a patterned surface, comprising: (i) irradiating in a patternwise fashion with ultraviolet light a surface having thiol groups to obtain a treated surface having (a) an area which has been irradiated and exhibits a resistance to biomolecule adsorption and (b) an area which has not been irradiated; and (ii) contacting said treated surface with a heterobifunctional crosslinking reagent, which binds to the area of said surface which has not been irradiated, to convert the area of said surface which has not been irradiated to an area which exhibits biomolecule adsorption, wherein said surface having thiol groups is prepared by reacting a substrate with a compound of formula (I) ##STR3## wherein X, Y, and Z are each independently C.sub.1-4 -alkyl or C.sub.1-4 -alkoxy, provided that at least one of X, Y, and Z is C.sub.1-4 -alkoxy, Ar is aryl, n is 1 to 20,n' is 1 to 20, l is 0 or 1, with the proviso that when l is 0, n' is 0.