Self-assembled molecular pattern by chemical lithography and interfacial chemical reactions

The fabrication of lipid-modified molecular patterns by Chemical Lithography combined with interfacial chemical reactions is reported. In this method, self-assembled monolayers (SAMs) of 4'-nitro-1,1'-biphenyl-4-thiol (NBT) were structured by Chemical Lithography which produced cross-linked 4'-amino-1,1'-biphenyl-4-thiol (cABT) monolayers within a nitro-terminated (NBT) matrix. The terminal amino groups in the cABT monolayer were diazotized to create diazo cations, and the lipid monolayer with negative charge was assembled on the diazo regions by electrostatic attraction. Under the exposure of UV light, the photoreaction occurs. The diazonium groups interacting with the lipid headgroups via electrostatic attraction decompose and release N2 which leads to the lipid monolayer covalently attaching to the cABT region. The presence of phosphorus in X-ray photoelectron spectra (XPS) reveals the binding of the phospholipid layer to the cABT surface. Atomic force microscopy (AFM) images display that lipid-modified molecular patterns with different sizes and shapes and with a thickness of ca. 2.5 nm have been formed. The resulting lipid-modified molecular patterns are considered to be a first step towards obtaining stable biointerfacing patterns and studying biomolecular recognition.