Nanoantennas for surface enhanced infrared spectroscopy

Abstract

Infrared spectroscopy is not only a powerful tool for the study of vibrational modes, it is also very effective for the investigation of metal nanoobjects such as films, wires, and dots. Metal films with thickness in the nm range can be studied with transmittance spectroscopy, which, via the development of the plasmon resonances, allows for the observation of their morphological development. Individual metal islands have their plasmon resonance in the visible range and only a weak tail of that resonance in the infrared. But nevertheless they can be detected with the help of adsorbate absorption lines. Their signals appear increased for molecules on metal islands. More signal enhancement is expected for metal particles at resonance, like metal nanorods with a length in range of infrared wavelengths that show a typical antenna resonance in the infrared related to considerable enhancement of the electromagnetic field.