We have demonstrated the construction and use of a low-cost optical microscope capable of single-molecule detection. The instrument operates in confocal, total internal reflection, epifluorescence, and brightfield transmitted light modes. The microscope is capable of detecting the blinking of individual CdSe/ZnS core/shell quantum dots as well as the fluorescence of single solution-synthesized CdSe nanowires. Furthermore, the Brownian motion of 40-nm and 500-nm diameter dye-doped polystyrene beads suspended in water can be observed. This demonstrates a wide range of applications for the microscope within the context of an undergraduate laboratory. Modifications to the system include the addition of a fiber-based spectrometer allowing the acquisition of fluorescence spectra from selected areas of samples. The assembly and alignment of such a microscope not only shows different forms of modern single-molecule microscopy to both undergraduates and high school students alike but also provides a useful platform for studying microscopic processes at the single-fluorophore limit.
“Demonstration of a low-cost, single molecule capable, multimode optical microscope” V. Protasenko, K. L. Hull, M. Kuno, Chem. Ed. 2005, 10, 269-282.