Musings: Creative Solutions
Diane Ackerman writes in her Natural History of the Senses: "I once stood in front of a huge piece of sulfur so yellow I began to cry."
The color purple is what caught my attention.
During my first day in a chemistry research laboratory, I poured some foul-smelling colorless liquids into a round glass flask while my research mentor adjusted the focus of an intense light bulb illuminating the mixture. Returning from lunch, I was surprised to see that the solution had become an audacious purple.
What had happened? How could light cause a chemical reaction? Could we synthesize compounds having other colors? Although I struggle to remember exactly what substance we produced that summer afternoon, the alluring beauty of that solution invited me to explore the molecular nature of color and initiated my career as a photochemist.
Many students find a chemistry laboratory to be an intimidating environment, with bench tops covered by fragile glassware, grotesque instruments, tangled electrical cables, mephitic residues, and unidentifiable stains. But sensual surprises can be discovered: slippery surfactant molecules, sweetly fragrant ethers, fluffy polycrystalline precipitates, and, of course, the vibrant hues of dyes.
Last semester, while watching a research student prepare a solution having unexpectedly bright red luminescence, I reflected on the spectrum of brilliant colors that have imbued our laboratory at Kenyon: the buttery yellow of a light-activated platinum anticancer drug, the luminescent green aluminum dye used in flat panel display screens, the orange glow of a ruthenium catalyst that can capture sunlight and convert its energy into electricity.
You see, purple can also have a purpose. Experimenting with solutions that harness the power of light, photochemists seek to treat disease, find replacements for dirty fossil fuels, and design more energy-efficient devices. We may initially be drawn to research by our ability to make colorful chemicals blossom in reaction flasks. But this ability pollinates ideas of how to employ these beautiful dyes in service to society.
In recent years, research efforts in our scientific community have been coalescing around one central challenge: developing clean and sustainable energy to replace fossil fuels. Throngs of students are joining our quest to devise efficient methods to harvest sunlight and convert the energy into useful forms, such as electricity or chemical fuels, to power the planet.
The holy grail we hunt is an "artificial leaf" that will use sunlight to split water and release clean hydrogen fuel. Inspiration comes from the beautiful pigments, such as green chlorophyll, employed in nature's molecular machines that produce carbohydrate fuels. Photochemists dream of leaves constructed from our own yellow, blue, orange, and purple molecules.
But it is foolish to think that these colorful dyes will cooperate in the effort. Constructing molecules to capture light is easy; even students in our first-semester chemistry lab course learn how to manipulate chemical structures to absorb either yellow or purple light. Convincing these excited molecules to do something useful with the absorbed energy is much trickier. Have you ever tried to catch a sunbeam in your hand?
Photochemistry research is a frustrating race against time. After absorbing light, most excited molecules last for only a few billionths of a second before releasing their energy as useless heat. I once worked with a student in my lab for a full year just to create a new light-absorbing platinum dye that could hang on for a bit longer than other members of its molecular family. The lifetime of our product, record-breaking at the time, was two millionths of a second. Progress in this field often comes in little millisecond steps.
Hundreds of scientists around the world cooperate and compete in the quest to design molecules that might harvest sunlight and produce solar fuels. We race to be the first to construct target molecules but also brace ourselves for the disappointment of discovering that a great idea has already been built in someone else's lab. The chemistry community recognizes each unique creation, such as our orange platinum dye, with something like a social security number that documents its admission into a global inventory of molecules. This is one of the special delights of chemistry: creating a form of matter that has never before existed in the world.
If participation in research requires speed, it also requires patience. Photochemists began the quest to crack water with sunlight during the energy crisis of the 1970s. After decades of research, some of the ersatz leaves constructed in laboratories operate with efficiencies besting their more beautiful natural models, but practical methods of making solar fuels may still be decades away. If our holy grail is ever found, the hunt will have involved generations of scientists.
Associate Professor of Chemistry Scott Cummings has taught courses on solar energy, hydrogen energy, and nanoscience and materials chemistry. Cummings, who joined the Kenyon faculty in 1995, received the Trustee Teaching Excellence Award in 1999 and the Robert J. Tomsich Science Award in 2003.