Applications of AFM-based nanoscale infrared spectroscopy: A conducting polymer and an amyloid-like protein

摘要

Infrared (IR) spectroscopy is a powerful tool for obtaining chemical information related to a material. Unfortunately, the wavelength of light used to make the measurement limits the size of structures that can be reliably identified by IR spectroscopy. Diffraction typically limits the spatial resolution of IR spectroscopy to 3-10 μm. Atomic force microscopy (AFM), on the other hand, provides exquisite spatial resolution (as small as a few nanometers), but the AFM technique has lacked broadly applicable chemical analysis capabilities. Recently, AFM and IR spectroscopy have been combined in a single instrument enabling the chemical identification of structures less than 100 nm in size [1-2]. In this paper, we describe the AFM-IR technique and illustrate its application using two specific examples: a conducting polymer and an amyloid-like protein. In the first example, the molecular structure of the γ-radiolytically synthesized conducting polymer polypyrrole (γ-PPy) is examined by AFM-IR spectroscopy and IR absorbance mapping [3]. The structures of the pyrrole monomer (Py) and polypyrrole (PPy) are given below.