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Green light is focused on the quantum dot solution. The green light excites the quantum dots and when the quantum dots return to their ground state, they emit red light as shown in the photograph.

Graduate students Tefera Tesema (r.) and Jenny Carolyn Sanchez (l.) prepare a quantum dot solution. 

The quantum dots emit light at 660 nm wavelength when excited. For the same material, the emission wavelength can be tuned broadly in the visible region simply by changing the size of the quantum dots. This tunability of wavelength is important for solar cell application as the wavelength of the sun light covers broad spectral region. 

As a chemist, Habteyes uses laser light in many of his experiments, requiring advanced optics setups like the one seen here. 

Assistant Professor Terefe Habteyes of UNM's Dept. of Chemistry and Chemical Biology. 

(l. to r.) Graduate students Hamed Kookhaee, Jenny Carolyn Sanchez, Bijesh Kafle, Tefera Tesema, Assistant Professor Terefe Habteyes, graduate student Sharmin Haq and undergraduate student Marisa Poveda.

(l.) The scanning electron micrscope image shows two gold nanobars with about a 10 nm gap between them. The near-field optical image (r.) shows the localization of the electric field between the two gold nanostructures when the nanostructures are excited with light. The intensity of the localized field can be 100 – 1,000 times higher than the intensity of the excitation light. As a result, when  molecules or other semiconductor materials are placed in the concentrated electric field, they experience much stronger interaction than they would in the absence of the plasmonic nanostructures.