Wheaton College Norton, Massachusetts

National Science Foundation grant supports physics and chemistry research

Wheaton has won a National Science Foundation grant to acquire a cutting-edge laser system that will advance the research of three Wheaton scientists and their students.

The $255,865 grant from NSF’s Major Research Instrumentation Program will finance the purchase of a tunable laser and auxiliary equipment to support the work of chemistry professor Thandi Buthelezi and physics professors John Collins and Xuesheng Chen. The instrumentation will foster Wheaton’s interdisciplinary curriculum and promote interactions among science departments.

A tunable laser can emit at a wide variety of colors, or wavelengths, and the ability to control and vary the wavelength makes this instrument a powerful research tool.

For instance, Collins will use the laser system to investigate new phosphor materials that could improve the efficiency and environmental friendliness of lighting. (A phosphor is a substance that exhibits luminescence when hit with certain light wavelengths.) Standard incandescent lamps are only 10 percent efficient, and fluorescent lights, only about 30 percent efficient. Fluorescent bulbs use ultraviolet light that shoots through a mercury gas and hits the phosphor, which re-emits white light. Now that new lighting technologies avoid the use of toxic mercury, there is a need for alternative light sources and phosphors. The challenge is to develop phosphors that can, for example, absorb a blue laser beam and emit a warm, white light at high efficiency.

“When I’m studying a new material, we don’t know exactly where [on the spectrum] it’s going to absorb and where it’s not,” Collins explains, “so it’s necessary to have a tunable light source. Also, this is a so-called pulsed laser, so it gives off light in a very short time, and I can study not only what comes out of the laser, but also how long it takes to come out. That gives information on the processes that are going on inside the material, so I can understand the physics.”

Buthelezi will use the new instrument in her investigations of host/guest interactions of photochromic molecules, which change color reversibly when exposed to light or heat. These molecules will include spiropyrans that could potentially be used for the development of molecular-based nanothermometers, which can measure temperatures in materials as small as a single living cell or a dewdrop. Her work also has potential applications to technologies such as photo-imaging, noninvasive drug delivery and optical switching.

Chen conducts optical studies on transparent ceramic materials, which are used in laser technology in place of more expensive crystals. For several years, Chen has collaborated with industry leader Boston Applied Technologies on the research and development of these materials. With the new laser system, she will further this research, focusing on infrared-to-visible upconversion light emission, on finding effective excitation wavelengths to produce efficient light output, and on studying the physical mechanisms that are involved.

Wheaton students are engaged in every step of these research projects. Students will learn how to use this sophisticated laser instrument, acquiring skills that will give them an advantage in graduate school and in the workplace.

The laser instrument will be central to three existing lab courses—“Quantum Chemistry,” “Modern Physics II” and “Experimental Physics.” Collins and Buthelezi will also develop and co-teach a new course that crosses disciplines.

“We’re getting together to offer a course about the workings of biological materials from a physicist’s and a chemist’s point of view,” says Collins. “There are new tools coming out to study nanoparticles, they’re using lasers to figure out protein folding, and they’re developing subcellular surgery” that’s performed with a laser microbeam or “optical scissors.”

The walls between scientific disciplines are breaking down, he says, and tomorrow’s scientists will need expertise in many overlapping fields to effectively investigate new scientific questions.