Reviewed by Lexie CornerMar 28 2025
A research team from the Nano Optics Group at the UNIST Department of Physics has developed a plasmonic structure capable of precisely adjusting nanometer-sized gaps in response to temperature changes. This technology enables real-time modification of nanogaps to match molecular sizes, enhancing detection capabilities beyond those of traditional sensors.
a) Schematic representation of the SERS sensing mechanism, showing molecules trapped in the nanogap. b) Schematic diagram of the transfer process of nanogaps with micrometer periodicity onto a flexible substrate. FE-SEM images of the top view of the nanogap c) before and d) after strain (scale bars: 10 µm). (The inset shows a close-up of a single gap from the top, (scale: 1 µm). Image Credit: UNIST.
The flexible nanogap structures developed in this study are essential for Surface-Enhanced Raman Spectroscopy (SERS). This technique utilizes the strong near-field generated by localized surface plasmon resonance when light interacts with metallic nanostructures on gold thin films, significantly amplifying Raman signals. By incorporating flexible substrates, the researchers enabled dynamic modulation of nanogaps, allowing for the analysis of a broader range of molecular sizes that were previously challenging to assess.
The study achieved a SERS signal amplification factor of about 107 and a detection limit of as low as 10-12 M, making it suitable for single-molecule detection. This was accomplished by effectively modulating the nanogaps through temperature control.
The ability to precisely control nanogaps using temperature changes allows us to achieve much higher sensitivity than conventional SERS sensors. This technology has significant potential, particularly for accurate analyses at the single-molecule level and in various environmental and medical diagnostic applications.
Dr. Mahsa Haddadi Moghaddam, UNIST
The National Research Foundation of Korea (NRF) supported the study.
Journal Reference:
Moghaddam, H, M., et al. (2025) Tuning 1D Plasmonic Gap at Nanometer Scale for Advanced SERS Detection. Advanced Optical Materials. doi.org/10.1002/adom.202403021