| Oct 03, 2025 |
New spectroscopy method reveals hidden molecular signals at material surfaces
A gap-controlled infrared technique makes it possible to study molecular interfaces with high sensitivity using affordable, widely available lab equipment.
(Nanowerk News) A new spectroscopy technique is making it easier and cheaper to study the invisible world where materials meet. Researchers have developed a method that reveals molecular interactions at surfaces and boundaries with a level of sensitivity that was previously hard to achieve without costly instruments (Analytical Chemistry, "Gap-Controlled Infrared Absorption Spectroscopy: A Unique Interface-Sensitive Spectroscopy Based on the Combination of Linear Spectroscopy and Multivariate Curve Resolution").
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These molecular interfaces are everywhere—on solid surfaces, thin films, and liquid boundaries. They shape processes in chemistry, biology, and materials science, from electrochemical reactions to protein behavior in cells. Yet for decades, they have been notoriously difficult to study. The problem lies in the methods: the faint signals from the interface are usually drowned out by stronger ones from the bulk material.
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The team behind the breakthrough turned to attenuated total reflection infrared (ATR-IR) spectroscopy, a common tool in labs. ATR-IR works by creating a weak electromagnetic field, called an evanescent wave, that probes molecules near a surface. On its own, though, ATR-IR struggles to separate the surface signals from background noise.
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The researchers solved this by adding precise distance control, creating a nanometre-scale gap between the crystal and the sample. “The nanometre-scale gap allows us to vary the contribution of interfacial molecules to the spectrum,” explains Associate Professor Tomohiro Hayashi.
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| Researchers have developed a low-cost method for the analysis of interfacial molecules by combining ATR-IR with precise gap-control and multi-variate data analysis. (Image: Institute of Science Tokyo) (click on image to enlarge)
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Once the data were collected, the team used a mathematical method known as multivariate curve resolution (MCR). This technique sorts overlapping signals, extracting the pure spectra of molecules at the interface while filtering out interference from the bulk material.
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“The strength of this approach lies in its simplicity,” says Hayashi. “By building on ATR-IR, which is already widely available, we eliminate the need for expensive instruments or specialized techniques to study interfacial molecules.”
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To test the method, the researchers applied it to several systems, including water molecules on self-assembled monolayers, quartz surfaces under different pH conditions, and polystyrene, a common material in lab culture dishes. The results matched those from advanced methods like sum frequency generation and surface-enhanced infrared absorption spectroscopy—both far more expensive and technically demanding.
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The new technique has broad potential. Because interfacial processes are central to technologies such as coatings, biomaterials, and nanodevices, this approach could accelerate progress across multiple fields. And because it uses widely available equipment, it opens the door for many labs that might otherwise be excluded by cost.
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“We believe that our technique will accelerate both fundamental research and industrial applications in surface science, nanotechnology, and materials engineering,” says Hayashi.
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The team is now working to adapt the method for real-time monitoring of dynamic processes at interfaces. With its mix of sensitivity, simplicity, and accessibility, the approach offers a new way to explore the subtle but crucial molecular interactions that shape our material world.
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