Surface plasmon resonance effect in AFM–IR and its application in the drug/metal nanocarrier studies

by Natalia Piergies (Institute of Nuclear Physics Polish Academy of Sciences, PL-31342 Krakow, Poland)

Thursday 6 Jul 2023, 11:00 → 13:00 UTC

The discovery of the surface enhancement effect, used in Raman Spectroscopy (RS) and Infrared Absorption (IR) Spectroscopy, allowed for the development of surface–enhanced RS (SERS) and surface–enhanced IR (SEIRA) techniques. The obtained spectral signal reinforcement results from two mechanisms: chemical and electromagnetic. The first mechanism is associated with the charge transfer between the adsorbed molecule and metal, and the second one depends directly on the surface plasmon resonance effect which induces a strong electromagnetic field on the metal nanosurfaces. This additional field enhances the spectral signal and improves the detection limit of the SERS and SEIRA techniques. Moreover, based on the surface selection rules it is possible to characterize the adsorption process of the molecules on the metal surfaces. However, the spatial resolution offered by SERS (~500 nm) and SEIRA (~1um) is not satisfactory, since the size of the single metal nanoparticle reaches ~50 nm or less.

The new hybrid photothermal technique combining atomic force microscopy with the IR (AFM–IR), where the AFM tip is used as a spectral signal detector, opens new opportunities for molecule/metal interaction studies. Until now, no systematic investigations have shown that the AFM–IR technique is sensitive to the plasmon resonance effect and that it can be controlled for improved molecule adsorption characterization. During the seminar, I will discuss the experimental proofs of the presence of the surface plasmon resonance effect in the AFM–IR measurement for the drugs immobilized on the metal monolayers. Moreover, based on the obtained intensity maps I will indicate the possible plasmon effects resulting from the applied metal monolayers and the AFM tip coated by the gold.