Optimizing plasmonic nanopipettes to enhance spectroscopic sensitivity

The addition of plasmonic nanostructures, such as gold, to nanopipettes concentrates light to enhance signal strength in near-field spectroscopy. This allows plasmonic nanopipettes to obtain detailed chemical information at the single-cell, molecule, or atom level in various applications, including electrochemistry, cell biology, and biomedicine.

Tareq et al. optimized plasmonic nanopipettes through a simple fabrication and evaluation method. They tested the performance of the nanopipettes, which were coated in varying thicknesses of gold, with surface-enhanced Raman spectroscopy (SERS) to determine the optimal gold-sputtering conditions. The tip coated with 10-nanometers of gold showed the maximum plasmonic enhancement.

The authors implemented the optimized probe in scanning ion-conductance microscopy with tip-enhanced Raman spectroscopy (TERS), a technique used to measure samples in electrolytic environments, such as biological interfaces or electrocatalytic systems.

“We documented how we evaluated the performance of the nanopipette probes so that if other groups are interested, they can also use the same approach to optimize their probes,” said author Naihao Chiang. “The goal is to help others to improve their designs for different applications.”

This work utilized a 785-nanometer laser, but the reported evaluation method could be extended to optimize plasmonic nanopipettes for other excitation wavelengths. The authors also employed sophisticated simulations to aid in their interpretation of the spectra from the SERS and TERS experiments.

“We’re very interested in combining angstrom-scale resolution with chemical information. The theory-experiment collaboration is allowing us to bridge those two pieces of information,” said author Lindsey Madison.

Next, the authors will apply this probe to study surface chemistry in interfacial systems, including mapping proteins on cell membranes and identifying active sites for hydrogen generation in heterogeneous electrocatalysis.

Source: “Fabrication and evaluation of plasmonic nanopipettes for near-field enhanced raman spectroscopy,” by Abu Montakim Tareq, Olivia E. Dalman, Munachimso Onuoha, Xing He, Ylli Conti, Richard Ifeanyichukwu Ikwugbado, Lindsey R. Madison, and Naihao Chiang, JVST: A (2025). The article can be accessed at https://doi.org/10.1116/6.0004821 .

This paper is part of the Papers from the AVS 71st International Symposium Collection, learn more here .