Quantum Dots

A 'Quantum' Leap to Italy

Cecilia Gentle, a senior chemistry major at the University of St. Thomas, almost didn't apply for a prestigious International Research Experience for Undergraduates scholarship she discovered last January a few days before the application deadline.

"I thought, 'I'm never going to get accepted, so why bother? I'm too busy right now, and there's no way I can get letters of recommendation, crank out an essay and get this application together in just three days,'" she said. The scholarship is offered annually to 17 undergraduates nationwide by the American Chemical Society. Selected students may choose to research in Germany, Singapore, the United Kingdom or Italy.

Cecilia Gentle

Cecilia Gentle

But the opportunity was too perfect – you could say down to the nanoscale – to pass up. "It was in the exact field of chemistry that I am interested in – inorganic materials chemistry with an emphasis on energy applications. So when I say 'exact,' I really mean 'exact,'" she said.

Gentle moved quickly – even tracking down a former professor on sabbatical from Anoka-Ramsey Community College where Gentle was a full-time PSEO student her last two years in high school – and was accepted. Six months later she boarded a plane destined for Italy to spend 10 weeks doing the research of her dreams: making quantum dots – tiny, man-made nanocrystals composed of semiconductors (such as silicon) and studying how to make them more efficient solar cells.

Gentle worked 40 hours per week under the direction of Dr. Loredana Latterini at the University of Perugia. Perugia is the capital city of Italy's Umbria region and located about 100 miles north of Rome. As part of the IREU program, she attended a weekendlong orientation in Washington, D.C., last April and will present a poster on her research in March at the national ACS conference in Denver.

Let there be light

Her day-to-day work entailed mixing and heating organometallic compounds, such as mixtures of cadmium (a heavy metal) and selenium (a mineral found in soil), in a solvent. When heated to 110 degrees Celsius (the boiling point of her solvent) on a hot plate, atoms from both elements bonded together to form quantum dots, crystals imperceptible to the naked eye.

One interesting thing about quantum dots is that they come to life, in (literally) glowing fashion, when exposed to UV light. Because quantum dots are so tiny, they interact with light in a unique way: They absorb different wavelengths of light based on their size.

"The only way I would know that I created something was by shining different wavelengths of light through the flask and watching how the material inside responded," Gentle said. "For example, if a quantum dot is two nanometers, it's blue, and if it's four nanometers, it's red. It's amazing. You have two things composed of the same elements, yet one is red and one is blue because they vary in size by two billionths of a meter."

However scientific and precision-based the process, the dramatic results made her giddy: "I have a technical fascination with chemistry and making sense of big ideas that initially mystify me, but there's also a childhood wonder aspect to this. In a lot of ways, I spent five days a week in a lab doing what the kid in me loves – making solutions of pretty colors in glass flasks. It was so cool!"

What's more, Gentle said, is that "if you can control the size of quantum dots, you can optimize the properties, and if you can optimize the properties, you can optimize the efficiency for whatever the electronic application is, like the solar cells you might be using them for."

Quantum dots glow under ultraviolet light.

Quantum dots glow under ultraviolet light.

Small dots, big contributions

Experiments like the one in which Gentle took part have the potential to make significant contributions to renewable energy, specifically in the efficiency and cost of solar cells, which convert the sun's energy into electricity.

"The most common solar cells you see on the market now are made using silicon. Even though silicon is an abundant element found naturally in the earth, it has to be made into perfect crystals to be used in solar cells, so it's incredibly expensive to produce, and it's also not very efficient," Gentle explained.

Every day the sun sends a gargantuan amount of energy to the earth that goes unharnessed. "That's why materials chemistry is a huge deal right now, especially with energy applications," Gentle said. "We're all working to make energy more efficient and renewable because our energy consumption is not slowing at all. It's growing. The outcomes of all this research could help by alleviating our dependence on fossil fuels."

She also noted that 3M has been using quantum dots in their optics division for use in televisions. Research also is underway for their role in biomedical imaging to aid in the detection of some cancers.

The Italian job

Gentle appreciated the opportunity to work in an international lab.

"I learned a lot about communication," she said. "It was sometimes frustrating, but I learned a lot from it and the language barrier made me appreciate my technical background. They didn't have to explain every single thing I'd be doing because I've done this kind of work already."

Cecilia Gentle at the University of Perugia, Italy.

Cecilia Gentle at the University of Perugia, Italy.

Since the summer after graduating from high school Gentle has worked for a lab in the Horticultural Science Department at the University of Minnesota, where her current project involves testing plants that have antimicrobial and antibiotic properties for Estee Lauder. Last summer she had an internship also synthesizing quantum dots at the University of Wisconsin-Madison.

Gentle also noted that the pace of Italian culture in the lab took some getting used to. "I got to the lab around 9 a.m. and left around 6 or 7 and took a lunch, which is pretty typical for any lab, but Italian culture is so different. Every few hours I'd hear, 'Coffee break?'" she said with a laugh. "The rigor in American labs sometimes feels more intense, but in my Italian lab we still got all the work done.  The short coffee breaks would help me give myself a break and be more efficient when I was working. It's just a difference in culture."

Over the course of her Italian job, an unexpected chemical change of sorts bloomed. "I developed a taste for espresso, and I can't drink American coffee now. It's so watery!" Gentle said. "I really miss Italian macchiatos and cappuccinos." When her 10 weeks came to a close, her Italian colleagues sent her home with a parting gift: an espresso machine.

 A reluctant chemist

As early as high school, Gentle tried very hard not to pursue chemistry. As her parents and older brother are chemists, Gentle was determined to veer from family tradition.

"Coming from a lineage of chemists, I had always approached problems in a systematic manner, but I was determined to do something different from the rest of my family. I remember during my first semester of college courses [as a PSEO student in high school], my general chemistry professor asked my major and I replied, 'anything but chemistry!'” she said.

But as the course progressed Gentle was enthralled by the "dynamic demos" in class. By the time she was a senior, her passion for science crossed a point of no return and she never looked back.

Gentle, who is 20, will graduate in May, after three years of undergraduate course work at St. Thomas, with a B.S. in chemistry and minors in mathematics and physics. During her time as a Tommie, she has pursued research opportunities every summer and has been awarded numerous accolades, including a 2014-15 Barry M. Goldwater Scholarship, one of the most competitive national honors granted to undergraduates pursuing post-graduate work in the STEM fields. This year, St. Thomas' Chemistry Department awarded her a William D. Larson Scholarship – the highest such honor bestowed by the department and given to students who show exceptional achievement in the field of chemistry and who intend to pursue careers in chemistry, related fields or medicine. She also has been named a Science, Mathematics and Engineering Scholar all three of her years at St. Thomas.

She plans to pursue a Ph.D. in materials chemistry. Though she added, with a little glee, that Italian culture's knack for good coffee got her thinking about a friend – a fellow chemist – who studied wine chemistry in France for three years. Gentle reminisced about her first project for the University of Minnesota lab  – studying the chemical composition of wine and figuring out how to detect flavonoids – a compound abundant in grapes.

"I wouldn't mind doing something like that in the future!" she said.