Peak force visible microscopy

Abstract

Optical responses of molecules and materials provide a basis for chemical measurement and imaging. The optical diffraction limit in conventional light microscopy is exceeded by mechanically probing optical absorption through...

Dual-Frequency Peak Force Photothermal Microscopy for Simultaneously Spatial Mapping Chemical Distributions and Energy Dissipation

“…The method that we developed for this research is through integrating the PFIR microscopy and the PF-visible microscopy. Both PFIR and PF-visible microscopies were developed in our group earlier and described in the literature. , The essence of these two methods is the mechanical detection of the photothermal responses of the sample with an AFM, operated in the peak force tapping mode or pulsed force mode. , The sample absorbs the infrared or visible radiations according to its vibrational and electronic resonances. The infrared absorption from vibrational resonances is characteristic of functional groups and chemical composition; the electronic resonances are typically within the visible frequency range for photovoltaics.…”

“…AFM-based photothermal microscopy has been increasingly popular . The AFM photothermal microscopy with visible excitation has also been implemented to probe the electronic absorption of the sample. − However, there is not yet a platform of AFM-based photothermal microscopy with simultaneous measurement with IR and visible excitations, which would be instrumental for studying novel photovoltaic materials.…”

Photo-induced force microscopy (PiFM) – principles and implementations

“…[3][4][5] In addition, PiFM has also been used to probe nonlinear polarizations in the sample, resulting in images based on stimulated Raman transitions 6 and pump-probe transitions. 7,8 Along with the development of improved detection strategies, [9][10][11] a great deal of progress has been made on the theoretical description of the PiFM signal, [12][13][14][15] putting the PiFM technique on a more solid footing. Whereas the first applications of PiFM involved inorganic materials 1,16 and metals, 17 the technique has since been used to study organic compounds (polymers 18 and organic semiconductors 19 ), biological samples (collagen fibres 20 and protein structures 21 ), as well as samples of geological significance (biominerals).…”

“…5,[24][25][26] This technique is referred to as peak force (PF)-PiFM, where the laser pulse is typically illuminating the sample moments before tip-sample contact. 3,11 Upon light illumination, material properties like the polarizability (a) at the microscopic scale, or the permittivity (e) and refractive index (n) at the macroscopic scale, dictate the sample's response. There are several mechanisms that can contribute to the force felt by the tip as a consequence of the presence of light.…”

“…5,24–26 This technique is referred to as peak force (PF)–PiFM, where the laser pulse is typically illuminating the sample moments before tip–sample contact. 3,11…”