Chemical force microscopy CFM

Chemical force microscopy (CFM) [26] is a progression from the physicochemical based detection of LFM to specific chemical detection. CFM performs the nanoscale chemical analysis of the sample, through the measurement of forces related to specific chemical interaction between a chemically functionalised tip (e.g., with carbon nanotubes or oligonucleotides) and a surface that is chemically functionalised with complementary (or non-complementary) chemical species, e.g., complementary oligonucleotides. 

Another AFM-based technique is chemical force microscopy (CFM) (Friedsam et al. 2004 Noy et al. 2003 Ortiz and Hadziioaimou 1999), where the AFM tip is functionalized with specific chemicals of interest, such as proteins or other food biopolymers, and can be used to probe the intermolecular interactions between food components. CFM combines chemical discrimination with the high spatial resolution of AFM by exploiting the forces between chemically derivatized AFM tips and the surface. The key interactions involved in food components include fundamental interactions such as van der Waals force, hydrogen bonding, electrostatic force, and elastic force arising from conformation entropy, and so on. (Dther interactions such as chemical bonding, depletion potential, capillary force, hydration force, hydrophobic/ hydrophobic force and osmotic pressure will also participate to affect the physical properties and phase behaviors of multicomponent food systems. Direct measurements of these inter- and intramolecular forces are of great interest because such forces dominate the behavior of different food systems. 

Thus, the different surface free energies ji can, in principle, be experimentally determined based on AFM pull-off force measurements if the surface free energy of the tip is varied in a controlled manner. These equations form the basis for the so-called chemical force microscopy (CFM) approach and allow one to discriminate between different materials [7]. 

A version of AFM is chemical force microscopy (CFM), where an AFM tip is coated with a thin chemical layer that interacts selectively with the different functional groups exposed on the sample surface. For example, gold-coated tips functionalised with a thiol... 

When the tip is functionalized with a chemical species, chemical discrimination can be achieved (chemical force microscopy, CFM) [236, 237]. Covalently functionalized nanotubes can be prepared, allowing chemical contrast between areas with different SAM layers [238]. For biomolecular applications tips can be chemically modified by a layer of molecules that bind especially strongly to complementary molecules. Insight into mechanical properties of biomolecules, such as binding/recognition interactions, unfolding, and elasticity of complex biomolecules has been gained on the basis of force-distance curves [239-243]. 

The chemical modification by silani2a-tion (or other chemical reactions) of carbon, oxide, or metal electrode surfaces [21, 22] or SAM formation on gold surfaces with thiol or disulfide compounds [23] has been utilized for the tip functionalization. The systematic chemical derivatization of the tips was carried out with silane [10, 24-27] or thiol [17, 18, 20, 28-37] derivatives. Today, chemical differentiation of the terminal groups by FFM [5-20,28, 36, 37] or adhesive force measurements [17, 18, 20, 24-28, 30-37] is called chemical force microscopy (CFM) [17]. Adhesive and frictional forces can be mapped in x-y planes as CFM images. The adhesive... 

Chemical force microscopy (CFM) will be used as a synonym for AFM using defined surface chemistry, for instance self-assembled monolayer functionalization, on AFM probe tips in order to measure differences in suriace chemical composition (using friction or adhesion differences related to interactions between functional groups or atoms exposed on both tip and sample surface as contrast) throughout this review article. 

As described here, these problems can be circumvented by "inverted" chemical force microscopy (CFM) [14], In inverted CFM, pull-off forces [15] between the tip coated with the reactant and an inert surface are monitored as a function of time (Figure 1). The contact area of the tip at pull-off in such experiments using non-reactive SAMs (as inert samples) deposited on Au(lll) varies between approximately 10-100 effectively interacting molecular pairs [16,17],... 

In probe microscopy, a trend called chemical force microscopy (CFM) has been formed. To enhance the chemical contrast in AFM images, the methods used in CFM for modifying probes increase their selectivity with respect to the adhesion force to areas of the studied surface with different chemical compositions [15]. 

Tapping Mode Atomic Force Microscopy (TM-AFM) Chemical Force Microscopy (CFM)... 

Chemical force microscopy (CFM) refers to the chemical modification of the AFM tip with specific functional groups to measure the forces involved in chemically specific interactions with a surface. It is implemented in lateral force microscopy, force spectroscopy (force curve), and force-... 

---