/pdf/self-assembled-monolayers-of-thiolates-on-metals-as-a-form-1neb0hj3k4.pdf

Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

Images and force measurements taken by an atomic‐force microscope (AFM) depend greatly on the properties of the spring and tip used to probe the sample’s surface. In this article, we describe a simple, nondestructive procedure for measuring the force constant, resonant frequency, and quality factor of an AFM cantilever spring and the effective radius of curvature of an AFM tip. Our procedure uses the AFM itself and does not require additional equipment.

Calibration of atomic‐force microscope tips

http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) precludes their widespread application in electronics, optics and sensing. We report on the sorting of carbon nanotubes by diameter, bandgap and electronic type using structure-discriminating surfactants to engineer subtle differences in their buoyant densities. Using the scalable technique of density-gradient ultracentrifugation, we have isolated narrow distributions of SWNTs in which >97% are within a 0.02-nm-diameter range. Furthermore, using competing mixtures of surfactants, we have produced bulk quantities of SWNTs of predominantly a single electronic type. These materials were used to fabricate thin-film electrical devices of networked SWNTs characterized by either metallic or semiconducting behaviour.

Sorting carbon nanotubes by electronic structure using density differentiation

A method to determine the spring constant of a rectangular atomic force microscope cantilever is proposed that relies solely on the measurement of the resonant frequency and quality factor of the cantilever in fluid (typically air), and knowledge of its plan view dimensions. This method gives very good accuracy and improves upon the previous formulation by Sader et al. [Rev. Sci. Instrum. 66, 3789 (1995)] which, unlike the present method, requires knowledge of both the cantilever density and thickness.

/pdf/calibration-of-rectangular-atomic-force-microscope-290lry8thn.pdf

Calibration of rectangular atomic force microscope cantilevers

THE forces between colloidal particles dominate the behaviour of a great variety of materials, including paints, paper, soil, clays and (in some circumstances) cells. Here we describe the use of the atomic force microscope to measure directly the force between a planar surface and an individual colloid particle. The particle, a silica sphere of radius 3.5 µm, was attached to the force sensor in the microscope and the force between the particle and the surface was measured in solutions of sodium chloride. The measurements are consistent with the double-layer theory1,2 of colloidal forces, although at very short distances there are deviations that may be attributed to hydration forces3–6 or surface roughness, and with previous studies on macroscopic systems4–6. Similar measurements should be possible for a wide range of the particulate and fibrous materials that are often encountered in industrial contexts, provided that they can be attached to the microscope probe.

Direct measurement of colloidal forces using an atomic force microscope

Measurement of forces in liquids using a force microscope

Measurements of Hydrophobic and DLVO Forces in Bubble-Surface Interactions in Aqueous Solutions

The aggregated structure of sodium dodecyl sulfate (SDS) adsorbed to the graphite−solution interface has been determined. Atomic force microscopy reveals that SDS adsorbs in periodic structures when the solution concentration is in the range 2.8−81 mM. Using previously obtained adsorption isotherms, we deduce that these structures are hemicylindrical, but we are not able to determine their length. The long axes of the hemicylinders lie parallel in grains which typically extend over (500 nm)2 to (1000 nm)2, but the grain size can be reduced by adsorption of other species from solution. Two basic types of grain boundaries have been identified:  broad boundaries, where the periodicity of both grains continue into the boundary for several periods, and narrow boundaries, where one or both of the hemicylindrical arrays terminate within a short distance. The period within each grain decreases when the concentration of SDS or the concentration of added NaCl is increased and approaches the diameter of bulk micelle...

Organization of Sodium Dodecyl Sulfate at the Graphite−Solution Interface

For a V‐shaped atomic force microscopy cantilever beam, the spring constants in the three principal directions are given in terms of the beam geometry and material properties. For the lateral stiffness, a closed‐formed expression is presented. Also, the normal and the longitudinal stiffness are obtained from a few simple equations. The results are compared with a finite element study and found to be very accurate. All spring constants depend strongly on the cantilever thickness, which is difficult to measure. In addition, the lateral and longitudinal stiffness are sensitive to the location and the height of the attached pyramid.

William A. Ducker

Papers

Direct measurement of colloidal forces using an atomic force microscope

Measurement of forces in liquids using a force microscope

Measurements of Hydrophobic and DLVO Forces in Bubble-Surface Interactions in Aqueous Solutions

Organization of Sodium Dodecyl Sulfate at the Graphite−Solution Interface

Lateral, normal, and longitudinal spring constants of atomic force microscopy cantilevers