Colloids scanning electron microscopy

Perhaps the most significant complication in the interpretation of nanoscale adhesion and mechanical properties measurements is the fact that the contact sizes are below the optical limit ( 1 t,im). Macroscopic adhesion studies and mechanical property measurements often rely on optical observations of the contact, and many of the contact mechanics models are formulated around direct measurement of the contact area or radius as a function of experimentally controlled parameters, such as load or displacement. In studies of colloids, scanning electron microscopy (SEM) has been used to view particle/surface contact sizes from the side to measure contact radius [3]. However, such a configuration is not easily employed in AFM and nanoindentation studies, and undesirable surface interactions from charging or contamination may arise. For adhesion studies (e.g. Johnson-Kendall-Roberts (JKR) [4] and probe-tack tests [5,6]), the probe/sample contact area is monitored as a function of load or displacement. This allows evaluation of load/area or even stress/strain response [7] as well as comparison to and development of contact mechanics theories. Area measurements are also important in traditional indentation experiments, where hardness is determined by measuring the residual contact area of the deformation optically [8J. For micro- and nanoscale studies, the dimensions of both the contact and residual deformation (if any) are below the optical limit. 

Honisbenger, M., and Rosset, J. (1977) Colloidal gold, a useful marker for transmission and scanning electron microscopy./. Histochem. Cytochem. 25, 295. 

Core-shell colloidal crystal films were prepared in three steps as outlined in Table 4.2. First, spherical submicron polystyrene particles were prepared by known methods38 39. The size of isolated polystyrene beads was 326 5 nm as determined by analysis of scanning electron microscopy (SEM) images using standard techniques. 

Tanaka K, Mitsushima A, Yamagata N, Kashima Y, Takayama H. Direct visualization of colloidal gold-bound molecules and a cell surface receptor by ultrahigh resolution scanning electron microscopy. J Microsc 1990 161 455—461. 

Horisberger, M. (1981) Colloidal gold a cytochemical marker for hght and fluorescent microscopy and for transmission and scanning electron microscopy, in Scanning Electron Microscopy II (Johari, O., ed.), SEM, Inc., AMF O Hare, Chicago, pp. 9-31. 

Hodges, G M., Southgate, J, and Toulson, E. C (1987) Colloidal gold-a powerful tool in S E. M. immunocytochemistry an overview of bioapplications. Scanning Electron Microscopy 1, 301—318. 

Leaching studies indicate that these radionuclides associated with sediment are not in the form of adsorbed ions, but in the form of discrete minerals, or are partly trapped inside the colloidal hydroxides of Fe and Mn coated on the sediment. Further studies by other leaching agents, such as hydroxylamine hydrochloride, and ammonium oxalate, and by X-ray diffraction and scanning-electron microscopy on sediment minerals will reveal the geochemical status of these radionuclides in the sediment. 

Douglas and Douglas (2000) Environmental scanning electron microscopy studies of colloidal sulfur deposition in a natural microbial community from a cold sulfide spring near Ancaster, Ontario, Canada. Geomicrobiol. J. 17, 275-289. 

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