2012 BFY Abstract Detail Page
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||W20 - Frontiers in Contemporary Physics Education: Gold Nanoparticle Photoabsorption & Quantization of Conductance Experiments
||This BFY workshop highlights the new pedagogical format of our sophomore Experimental Contemporary Physics course. We strive to provide a strong underlying core of experimental skills in modern topics and, at the same time, encourage students to join faculty research groups. We follow a physics research model using experiments that explore contemporary physical concepts from ongoing faculty research projects. The experimental format shows students "how physics research is actually conducted!" The two experiments we will highlight, 1) Optical characterization of Au nanoparticles, and 2) Quantization of Conductance, were developed as a direct result of the nanoscience and technology research the co-leaders conduct in their own laboratories. Using this basic curricular plan, the course maintains a truly contemporary nature, while providing an introduction to the concepts and instrumentation skills necessary for our students to begin physics research.
1) We explore how surface area, volume and shape change material behavior via optical spectroscopy of Au nanospheres and nanorods (NPs). White light induces a plasmon resonance in the metallic NPs which is measured spectrally. The transmission and scattering spectra of the Au NPs provide a measure how the spectral plasmon resonances reflect the particle morphology. The basic optical setup requires a fiberoptic light source and a reasonably inexpensive spectrometer, as plasmon resonances are quite broad. The excitation of charge carriers in a semiconducting nanowire is introduced next. Finally, both concepts are brought together by describing their application in a plasmon-enhanced nanowire-based biosensor. Students enjoy the visual nature of this experiment and the opportunity to align an optical system.
2) We demonstrate an extremely simple and inexpensive experiment to introduce atomic-scale confinement effects and particle-wave duality. A manual break junction in a gold wire is utilized to explore the quantization of the electrical conductance when the wire width is stretched to the atomic limit. A simple circuit reads the voltage across the break junction via LabView. Just before the wire breaks, the lateral confinement of the conduction electrons causes a step- wise increase in resistance with steps that depend on two fundamental constants of nature divided by an integer. This is due to the wave nature of the electrons that traverse the junction. This experiment is exciting for students because they can measure a complex idea like wave- particle duality with objects that they can "see."
In addition, we discuss how small adjustments make the experiments appropriate for more advanced students.
Dr. Jan Yarrison-Rice
Andrew Makepeace and Nick Geitne