Manufacture of semiconductor-thiol-biomolecular systems and investigation of their optical properties

In this study, methods which enhance the protein immobilization on surface were investigated for semiconductor biosensor applications. Some biological molecules (DNA, RNA, proteins, etc) do not establish a bond easily with semiconductors. Nonetheless, various methods were developed for creating a bond between biomolecules and semiconductors. One of these methods is the interaction with thiols (-SH group) which ensures the bonding between a biomolecule and semiconductor. It was found that n-GaAs (001) surface is not convenient for direct protein bonding as a result of having a contact angle value (66,5°) which is close to the hydrophobic surface. The value of contact angle was decreased to 36,5° after passivation of GaAs surface with KOH for 30 min and 3° after passivation of another GaAs surface with NaOH for 30 min for catalyzing the bonding of thiol, and thereby protein, to the surface. If the photoluminescence (PL) data are investigated, it can easily be deduced from increments of the PL peaks that the number of thiol molecules bonded with surface is increased as the contact angle decreases on the surfaces completed passivation. After, 11-Mercaptoundecanoic acid (thiol), which increases the interaction between the surface and protein, was applied for 24 hours for protein bonding. In addition to these studies, 22 Å of Au layer was deposited on the n-GaAs (001) surface by magnetron sputtering system. Thiol-protein bonding with the Au deposited surface was ensured through Surface Plasmon Resonance (SPR) supported ellipsometer. Surface and optical analyses were conducted through Atomic Force Microscope (AFM) and PL.Key Words : GaAs, Biosensor, Thiol