Abstract:

The T-BAG method was used to deposit hydroxyl-terminated organic layers on silicon substrates. These treated silicon substrates were utilized as platforms for the development of chemical and biological sensors. Detailed characterization of the modified surface was conducted to understand the nature of bonding, which is important for their use as sensors. A new method, based on X-ray Photoelectron Spectroscopy (XPS), was developed to distinguish a multilayer from a monolayer film. The hydroxyl-terminated surfaces were further modified to attach single stranded DNA molecules via standard coupling chemistry. This method was then adapted for use on silicon-on-insulator (SOI) substrates. A SOI-FET, shown to be highly surface sensitive, was used to demonstrate label-free detection of DNA. A new platform, based on phosphonate terminated SAMs, for the detection of gaseous nitric oxide, was developed. Hematin, which bonds NO, was attached via hydroxyl termination of the phosphonate films; high resolution XPS was used to demonstrate the detection of NO. Based on measurements of surface loading of hematin species using quartz crystal microgravimmetry and XPS, detection of ? 40 picomoles of NO in the sampled region was accomplished.