An electrochemical sensor developed at Oregon State University holds promise for making food quality testing faster, more accurate, more environmentally friendly and less expensive.
The novel sensor, which also has potential applications in health care and environmental monitoring, is based on the design principle of engineered interfacial chemistry.
The sensor requires tiny sample amounts, can be built into portable testing devices, and is fast and highly sensitive.
Funded by the National Science Foundation, the study by scientists at Oregon State and researchers in Taiwan was published in Applied Nano Materials, a journal of the American Chemical Society.
The collaboration led by Mas Subramanian and Gopika Meenakumari Gopakumar of the OSU College of Science engineered a nanocomposite sensing material consisting of strontium oxide, functionalized carbon black (tiny particles of almost pure carbon), and reduced graphene oxide.
Together, these components formed a highly conductive interface that enhanced adsorption, accelerated electron transfer and improved the electrochemical oxidation of theobromine, the compound the scientists sought to detect in barley tea, black tea, green tea, coffee and chocolate milk.
Chemically similar to caffeine and found in cocoa-derived products, theobromine is a mood elevator in humans, producing a sense of calm alertness, and is what makes chocolate toxic to dogs.
"Accurate measurement of theobromine is important for food quality control, labeling consistency and consumer safety," said Subramanian, university distinguished professor and Milton-Harris Professor of Materials Science in the Department of Chemistry. "The compound contributes to flavor and mild stimulant effects, and its reliable monitoring is especially valuable in formulations requiring precise composition. Theobromine detection may also have broader applications in toxicological and analytical studies."
The conventional technique for detecting theobromine involves expensive lab equipment, trained technicians, long processing times and harsh chemicals in the form of strong alkalis. The new nanoscale sensor, in contrast, works at neutral pH - making it safer and greener - because all it needs are the micro-alkaline zones it creates at the electrode surface, which do not alter the pH of the overall solution.
"This is the kind of innovation that moves industry toward greener, better chemistry," said Gopakumar, a postdoctoral researcher. "The results we got with theobromine were very promising, a successful test case that shows interfacial alkaline microdomain engineering is a new way to make weakly electroactive molecules detectable. That could mean better measuring of pharmaceuticals, contaminants in the environment, toxins in food, and biomarkers in medical diagnostics."
"This work demonstrates how controlling chemistry at the nanoscale interface can unlock sensing performance that conventional approaches often miss," Subramanian added. "It points to a broader pathway for developing economical and practical sensors for complex, real-world samples."
Oregon State graduate student Chung-Yi "Gary" Hsu also contributed to the research. Collaborators from Taiwan included Chih-Yu Kuo, associate professor in the Department of Chemical Engineering and Biotechnology at National Taipei University of Technology, and Mani Govindasamy, assistant professor and division director at the Research Center for Intelligent Medical Devices at Ming Chi University of Technology.
