Secondary Functionalization of Allyl-Terminated GaP(111)A Surfaces via Heck Cross-Coupling Metathesis, Hydrosilylation, and Electrophilic Addition of Bromine

The functionalization of single crystalline gallium phosphide (GaP) (111)A surfaces with allyl groups has been performed using a sequential chlorine-activation/Grignard reaction process. Increased hydrophobicity following reaction of a GaP(111)A surface with C3H5MgCl was observed through water contact angle measurements. Infrared spectra of GaP(111)A samples after reaction with C3H5MgCl showed the asymmetric C═C and C═C–H modes diagnostic of surface-attached allyl groups. The stability of allyl-terminated GaP(111)A surfaces under ambient and aqueous conditions was investigated. XP spectra of allyl-terminated GaP(111)A highlighted a significant resistance against interfacial oxidation both in air and in water relative to the native interface. Electrochemical impedance spectroscopy indicated a change in the flat-band potential of allyl-terminated GaP(111)A electrodes immersed in water relative to native GaP(111)A surfaces. Further, the flat-band potentials for allyl-terminated electrodes were insensitive to...