X-Ray Scattering


Figure 1: Characterization using temperature-controlled X-ray diffraction is a useful analytical tool for solids, liquids, and powder samples across many research applications, including solar cell research, drug discovery, and life sciences. Stock images used with permission from Shutterstock, iStock, and Pixabay.


to study materials with different forms, including solids (for example, powders, pastes, or thin films), liquids, liquid-crystals, and gels (with ordered and disordered structures). When coupled with a moving detector and automated alignment/ calibration routine, phase identification is fast and accurate. Te Ganesha 300XL provides extensive automation, a large


sample chamber, and versatile sample area to provide a highly customized instrument for temperature-dependent analysis between -175°C and 350°C, including analysis of solutions in refillable capillaries from 4°C to 80°C, and time-resolved micro-fluidics monitoring in air. Additionally, the instrument can be used for grazing angle experiments (GISAXS/GIWAXS), which is useful for thin films such as photovoltaic devices. Key applications of the Ganesha 300XL include nano-particle size, shape, distribution, and polydispersity analyses; three- dimensional protein molecule structure analyses (folding and unfolding); identification of molecular assembly or disassembly;


and colloids, metals, cement, oil, polymers, plastics, foods, and pharmaceuticals. Te setup at CNIE (Figure 3) can be widely applied to detect new polymorphs and phase changes in both solid and liquid samples. In order to study the temperature- dependent properties of these materials, such as phase changes at high or cryo temperatures, the Ganesha can be equipped with Linkam capillary or GI stages to enable in situ crystallographic measurements as the sample conditions change.


Speed is of the Essence Using a Linkam HFSX350-CAP temperature-control


capillary stage, it is possible at the CNIE to conduct time- resolved SAXS/WAXS studies of the phase behavior of pharmaceutical compounds under controlled heating/cooling conditions (-195°C to 350°C) at a remarkable rate of 1 second per scan, while achieving distinct and clear scattering data, as shown in Figure 4. In traditional XRD, 30 minutes to an hour is required to collect a pattern. Using the Linkam stage it is possible to heat and cool a sample rapidly and collect the pattern in just 1 or 2 seconds. In prior research at the University of Sheffield in 2010 [4],


Han Wu, the current CNIE Research Facility Manager, studied pyroglutamic acid (P), which occurs naturally in fruits, some plant foods, dairy, and fermented products, such as soya sauce, and can be produced by thermal dehydration and cyclization of glutamic acid [5,6]. Te brain-boosting effects of P were discovered in 1984 [7], and it plays an important role in the preservation and activity of key neurotransmitters. P esters can be used as dermal penetration enhancers for therapeutic agents having poor skin permeation [8] or hair growth agents [9]. In chemical synthesis, it has been used as a versatile chiral building block in asymmetric synthesis of alkaloids [10], pharmaceuticals, and many other natural products. Han Wu and her colleagues discovered three polymorphs


Figure 2: CNIE researcher fitting the HFSX350-CAP inside Ganesha’s SAXS/ WAXS chamber.


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for P: α’ (low-temperature polymorph); α (ambient temperature polymorph); β (high-temperature polymorph), and two phase changes (α/β and α’/α). Te β and α’ forms had not been recognized prior to this work. Tey found that the change from α’/α happens slowly over a range of very low temperatures (starting at -140°C) and appeared to be Martensitic in character, in which strain at the α/α’ interface in partially transformed crystals caused the transformation to occur in bursts with increased undercooling.


www.microscopy-today.com • 2021 November


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