Nanoscale chemical imaging by photo-induced force microscopy: technical aspects and application to the geosciences

Photo-induced force microscopy (PiFM) is a new-frontier technique that combines the advantages of atomic force microscopy with infrared spectroscopy and allows for the simultaneous acquisition of 3D topographic data with molecular chemical information at high spatial (~ 5 nm) and spectral (~ 1 cm⁻¹) resolution at the nanoscale. This non-destructive technique is time efficient as it requires only conventional mirror-polishing and has fast mapping rates on the order of a few minutes that allow the study of dynamic processes via time series. Here, we review the method’s historical development, working principle, data acquisition, and evaluation, and provide a comparison with traditional geochemical methods. We review PiFM studies in the areas of materials science, chemistry and biology. In addition, we provide the first applications for geochemical samples including the visualization of faint growth zonation in zircons, the identification of fluid speciation in high-pressure experimental samples, and of nanoscale organic phases in biominerals. We demonstrate that PiFM analysis is a time- and cost-efficient technique combining high-resolution surface imaging with molecular chemical information at the nanoscale and, thus, complements and expands traditional geochemical methods.