Atomic Force Microscopy and Magnetic Force Microscopy Study of Model Colloids

Abstract

Atomic force microscopy (AFM) is used to study the size, shape, and polydispersity of a variety of magnetic and nonmagnetic model colloids, previously imaged by transmission electron microscopy (TEM) only. Both height and phase images are analyzed and special attention is given to 3D morphology and softness of particles, as well as structures and presence of secondary components in the colloid, difficult to investigate with TEM. Several methods of tip characterization followed by deconvolution were applied in order to improve the accuracy of lateral diameter determination. In the case of magnetite particles dispersed in conventional ferrofluids, we explore both experimentally and theoretically the possibility of using magnetic force microscopy (MFM). We propose and discuss several models which allow to estimate the magnetic moment of a single domain superparamagnetic sphere using MFM, which cannot be done with other techniques; alternatively the tip magnetization can be determined. C 2002 Elsevier Science (USA)

Heteroaggregation, repeptization and stability in mixtures of oppositely charged colloids

“…1). Since the lateral diameter is strongly affected by tip convolution, height information was used to determine the particle size [12]. The average diameter of particles was 12.1 nm for negative particles (which confirms the nominal diameter re- ported by DuPont) and 15.2 nm for positive particles.…”

“…Particle sizes were determined using an atomic force microscope (AFM) (Nanoscope IIIa, Digital Instruments), in tapping mode, according to [12]. In order to image the cluster formation as well as single particles in the ethanol based samples, we used the cryogenic transmission electron microscopy (cryo-TEM).…”

Cantilever-based optical interfacial force microscope in liquid using an optical-fiber tip

“…In previous studies, 16,17 the radius of the tip was critical in determining the particle size when the curvature of the tip was larger than the particle. The tip-radius of the optical-fiber tip was determined by analyzing Figure 2(d), with the equation R = (x 2 +y 2 )/(2y), where R is the tip radius, y is the y-axis distance between the maximum height and the minimum height of the tip, and x is the x-axis distance between the same points.…”

Magnetic Force Microscopy: Basic Principles and Applications

“…This pseudodomain model allows interpretation of most results obtained by MFM on the basis of bulk probes. For probes with a different geometry, for example those where the magnetic region is confined to a thin layer, other appropriate models have been developed (Rasa et al, 2002). Fig.…”