Imaging in liquid

The surface deformation could be reduced even further with intermittent contact SFM. Tapping mode imaging in liquids has been described by several groups [185-191]. The main focus has been put on biological systems such as DNA, cells, chromosomes and proteins. However, it turned out to be rather tricky to perform the measurements. The resonant frequencies were usually 2-5 times lower than in air and the resonant peak gets strongly dampened and broadened [ 192,193]. Because of acoustic excitation of the cantilever holder and the body of fluid, the spectrum can be superimposed by other resonance s which not sensitive to the surface approach and cannot be used for the feedback control [185]. 

Fig. 13 SPR and AFM analyses of controlled streptavidin recognition on mixed oligo(ethylene glycol) layers, (a) Chemical structure of the mixed layer components linear oligo(ethylene glycol) left) and biotinylated moiety (right), (b) Streptavidin binding at 23°C and (c) at 45°C. (d) SPR sensogram of streptavidin adsorption at 23 and 45°C. Arrows show injections of (a) water (b) streptavidin solution and (c) subsequent water rinse at 23°C and (d) streptavidin solution and subsequent water rinse at 45°C. (e) Tapping mode AFM images in liquid phase after injection of streptavidin solution at 23°C and (f) at 45°C. Reprinted, with permission, from [185]. Copyright (2008) American Chemical Society...

This book addresses the most recent developments in the investigation and manipulation of liquids at the nanometer scale. This new field has shown important breakthroughs in the basic understanding of physical mechanisms involving liquid interfaces, which led to applications in nanopatterning. It also has consequences in force microscopy imaging in liquid environment. Co-authored by more than 20 of the most prominent scientists in the field, the book proposes a timely review of various aspects pertaining to nanoscale liquid interfaces. 

R Brunner, A Bietsch, O Hollricher, O Marti. Distance control in near-field optical microscopy with piezoelectrical shear-force detection suitable for imaging in liquids. Rev Sci Instrum 68 1769-1772, 1997. 

Imaging in Liquid and the Determination of Surface Electrical Properties... 

Imaging in Liquid and the Detennination of Surface Electricai Properties 115... 

The resolution of contact mode AFM is, as is typical for AFM in general, limited by the tip size, tip shape, and deformation in the tip-sample contact area. The range and strength of the interatomic and intermolecular forces between tip and sample may become significant, if the imaging force is very small. For operation in air, however, capillary condensation may occur in the tip-sample contact [12], which results in significant attractive forces that cannot be counteracted in a stable manner. Imaging in liquid (e.g., water or ethanol) can... 

FIGURE 3.5 AFM images in liquid (tapping mode) of laccase on a screen-printed carbon electrode (a) height, (h) amphtude, and (c) expanded section showing enzyme molecules marked hy hlack dots. Scale har=50 nm. (Adapted with permission from Ref. [27]. Copyright 2010, Elsevier.)... 

First, STM images in liquids were obtained in electrically insulating fluids such as N2 or paraflin oil [67]. However, it was demonstrated in 1986 that STM measurements can also be operated in conducting hquids such as a saline solution [68]. Consequently, STM at solid/Hquid interfaces has become an important tool for studying electrochemical processes in situ [72-78], and it is also of help in fields such as catalysis, corrosion, lubrication, and biological research [79]. 

Droz, E., Taborelli, M., Descouts, P, Wells, T.N.C., and Werlen, R.C. (1996). Covalent immobilization of immunoglobulins G and Fab fragments on gold substrates for scanning force microscopy imaging in liquids. J. Vacuum Sci. Technol. B 14 (2), 1422-1426. 

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