Nanoscale Characterisation and Imaging of Partially Amorphous Materials using Local Thermomechanical Analysis and Heated Tip AFM

Abstract

The study has demonstrated that thermal nanoprobes represent a novel method of characterising and imaging partially amorphous materials.

Mapping amorphous material on a partially crystalline surface: Nanothermal analysis for simultaneous characterisation and imaging of lactose compacts

“…Wollaston wire probes are the traditional probe type used for microthermal studies and have a tip diameter of circa 5 mm, while the nanoprobes have dimensions akin to those of conventional AFM probes and hence may allow considerably greater spatial resolution. 19 The scan area for all AFM images was 50 mm  50 mm with a resolution of 200 lines; the spatial resolution was 200 data points per line.…”

“…Such site-specific thermal techniques have been referred to microthermal (and more recently nanothermal) analysis and include localised thermometric, thermomechanical, and calorimetric measurements, 17,19 all of which are point measurements and allow identification of the nature of the material under study via properties such as the softening temperature or differential heat flow. The same probes may be used in scanning mode to obtain images based on thermal properties such as thermal conductivity.…”

“…21 We also demonstrated proof of concept of using nanoprobes to discriminate between amorphous and crystalline indometacin in both L-TMA and variable temperature pulsed force modes. 19 Here we take these studies further by examining mixed amorphous and crystalline materials so as to mimic materials whereby both components may be present and compare the use of Wollaston and thermal nanoprobes for their characterisation. We examine the effects of using variable tip temperature on the ability of the approach to discriminate between these materials and the combined use of single point and mapping studies.…”

Structural Characterization of Amorphous Solid Dispersions

“…1-14.9 at the end of the chapter. (Amigo 2010;Breitkreitz and Poppi 2012;Chen et al 2011;Gendrin et al 2008;Jørgensen et al 2009;Kazarian and Ewing 2013;McIntosh et al 2012;Pavia et al 2001;PratsMontalbán et al 2012;Reich 2005;Van Eerdenbrugh and Taylor 2011;Zeitler et al 2007) Change in frequency of incident electromagnetic radiation due to the absorption or inelastic scattering of a portion resonant to the frequency of molecular, lattice or phonon vibration (stretching, bending, bending, rocking, wagging, scissoring, etc (Carlton 2011;Dieing et al 2011;Eddleston et al 2010;Vitez et al 1998) Interaction of molecular solids with optical/electronic source resulting information on morphology, solid state Polarized light microscopy Identification of solid form based on birefringence and morphology Scanning electron microscopy (SEM) Focused electron beam scanned over the specimen surface under a high vacuum Penetrate the sample interior and the emitted electrons produces the specimen topography Transmission electron microscopy (TEM) Spatial variation of the inelastic interaction of electron beam while transmitting through a sample produces highly resolved image Thermo-gravimetry (TGA; Giron et al 2004) Weight change of the sample as a function of temperature and/or time measured using a sensitive microbalance (Barnes et al 2011;Brown and Vickerman 1984;Chehimi et al 2011;Clark 1977;Harding et al 2007;Ho and Heng 2013;Pollock and Hammiche 2001;Sitterberg et al 2010;Thielmann and Levoguer 2002;Voelkel et al 2009) Atomic force microscopy (AFM) A sharp probe on a flexible cantilever tip (10-20 nm) scanned...…”

The Development of Heated Tip Force–Distance Measurements as a Novel Approach to Site-Specific Characterization of Pharmaceutical Materials

“…This is particularly pertinent to multicomponent systems whereby the melting or softening of one component can influence the subsequent thermal behavior of a second. We have utilized a related heated tip approach to perform variable temperature pulsed force mode (PFM) imaging 16 and we see both techniques as being facets of a new field of using heated tips for simultaneous imaging and mechanical assessment.…”