A new route to the formation of biomimetic phosphate assemblies on gold: synthesis and characterization

A biomimetic model system based on long-chain alkanethiols tailored with serine, threonine and tyrosine side-chain groups is created as a platform for the study of phosphorylated amino acids. The phosphorylated analogues are synthesized with protective tert-butyl groups that after assembly on thin polycrystalline gold films are removed in an acidic deprotection solution to form the corresponding phosphate self-assembled monolayers (SAMs). The SAMs are thoroughly characterized with null ellipsometry, contact angle goniometry, infrared reflection-absorption spectroscopy and X-ray photoelectron spectroscopy. The assembly and the subsequent deprotection process are optimized with respect to molecular orientation and chain conformation by varying the incubation time and the exposure time to the deprotection solution. The high quality of the generated SAMs suggests that the present assembly/deprotection approach is an attractive alternative when traditional synthetic routes become demanding because of solubility problems.