Nanoscale Studies of Proteins and Thin Films Using Scanning Probe Microscopy

Nanostructures of organosilanes, thin metal films, and protein nanopatterns were prepared and analyzed with atomic force microscopy (AFM). Organosilanes with designed functional groups were used to selectively pattern green fluorescent protein at the nanoscale using protocols developed with particle lithography. Mesospheres are deposited onto a substrate to produce a surface mask. Organosilanes are deposited to form a matrix film surrounding nanopores for depositing proteins. The nanopatterns were characterized using AFM, after steps of particle lithography for directly visualizing surface changes. Studies with AFM also provide a compelling tool for teaching undergraduates to introduce concepts of nanoscience. An undergraduate laboratory was developed with particle lithography to introduce the concepts of nanoscience and surface chemistry. Nanopatterns of organosilane films are prepared using protocols of particle lithography. An organic thin film is applied to the substrate using steps of either heated vapor deposition or immersion in solution. At the molecular level, two types of sample morphology can be made depending on the step for depositing organosilanes. Experience with advanced AFM instrumentation is obtained for data acquisition, digital image processing and analysis. Skills with chemical analysis are gained with bench methods of sample preparation. Concepts such as the organization of molecules on surfaces and molecular self-assembly are demonstrated with the visualization of nanopatterns prepared by students. Experiments with particle lithography can be used as a laboratory module or for undergraduate research projects, and are suitable for students with a multidisciplinary science background. The kinetics and properties of thin gold films during dewetting were studied using AFM. Thin films of gold with varying initial thickness were first deposited onto fire polished glass slides and imaged with AFM. Next, the films were annealed for two hours, and then imaged after annealing. Gold islands with varying degrees of separation were formed. Surface plasmon spectroscopy was also used to analyze the gold films. To further this study, a kinetic study was done. Two gold thin films of 10 nm each were imaged after being annealed for 15, 30, 45, 60 and 120 minutes. It was found that after the first 15 minutes of annealing, gold islands were observed