The use of self-assembled monolayers (SAM) on semiconductors creates a basis for the design and creation of bioelectronics, such as biosensors. The interface between the surface and an organic monolayer can change significant electrical and physiochemical properties of a biological device. Therefore, this research examined the orientation and packing of peptide and alkylthiol monolayers on the bulk III-V semiconductor, Gallium Arsenide (GaAs). The surface of GaAs was chemically modified with 1-octadecanethiol (ODT), 6-mercapto-1-hexanol (MHL), and two different sequences of the human immunodeficiency virus (HIV-1) derived TAT peptide. By the use of Fourier transform - infrared reflection absorption spectroscopy (FT-IRRAS) and contact angle measurements, the monolayers were analyzed for crystallization and hydrophobicity, respectively. It was found that ODT and MHL alone showed fairly ordered packing, however, ODT created a more hydrophobic surface than MHL. When mixed together at different concentrations, the monolayers were disordered on the surface. Also, monolayers exhibited disorder when TAT peptides were mixed with both ODT and MHL alone. All in all, the understanding of the semiconductor-organic monolayer interface is advancing quickly and providing a foundation for the design and creation of biosensors.
Advisor: Albena Ivanisevic, Biomedical Engineering, Purdue University, West Lafayette, IN
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