A Combined SAXS/WAXS/XAFS Setup Capable of Observing Concurrent Changes Across the Nano-to-Micrometer Size Range in Inorganic Solid Crystallization Processes

Abstract

Crystalline inorganic solids show intriguing properties of importance in many technological applications, such as ferromagnetism, semiconductivity, gas sensing, and catalysis. A great deal of attention has been and continues to be focused on understanding why these materials possess these properties. When such phenomena are fundamentally understood, it becomes possible to improve their performance, and this can potentially lead to the development of new "designer" materials to meet the challenges of the future. However, the concept of a designer solid is still some way from being realized since the critical stages of inorganic solid crystallization are still not sufficiently understood.Time-resolved in situ experimentation represents the most likely means by which the key stages of inorganic solid crystallization can be unraveled. Many studies using a variety of analytical techniques on a range of samples have been reported in the literature with the area of microporous material crystallization receiving a lot of attention. 1-3 However, such studies often focus on data acquired using a single technique, which rarely provides all of the necessary information from which new insight can be obtained. This is because changes occur over the molecular (local coordination state), nano (primary units), and microscale (crystallite formation) dimension during crystallization, whereas the techniques are often only able to probe limited size regimes. In other words, with separate in situ studies, it is sometimes difficult to obtain consistent and corroborative information. One way to overcome these limitations is to intelligently combine complementary techniques into one experimental setup, and this approach often yields new insight. Some examples include the observation of primary units in zeolite MFI formation and the importance of a coordination state change of Co 2+ before the formation of CoAlPO-5 molecular sieves. 2,4 In addition, a combination of techniques has several advantages. 5 One being the possibility to evaluate if the probing technique may influence the state of a sample. Furthermore, you circumvent the need to repeat identical experimental conditions for recording separate measurements; although seemingly a trivial point, it is far from easy to achieve experimentally.In this communication, we present a novel setup, which combines SAXS, WAXS, and XAFS to study the crystallization processes of inorganic solids in depth. This study aims to follow the changes that occur with time at the molecular, nanoscopic, and crystalline level, with a time resolution in the order of a few minutes. The setup enables us to observe the various stages of zinc-substituted microporous aluminophosphate formation in one experiment and represents, to the best of our knowledge, the first data of its kind acquired in such a manner. A scheme of the setup is given in Figure 1. In Figure 2, we show the raw data collected during the heating of the zinc-doped aluminophosphate gel. Data analysis suggested that the initial † Utrecht Univers...

The role of synchrotron radiation in examining the self-assembly of crystalline nanoporous framework materials: from zeolites and aluminophosphates to metal organic hybrids

“…These results are interesting as the authors propose experimental evidence that the formation of chain-like species (e.g. Loiseau et al 49 WAX study) are indeed directly involved in a chain formation mechanism of AlPOs as proposed by Oliver et al 50 Similar measurements were performed by Beale et al 67 on ZnAPO-34, with an even closer match between the SAXS and Scherrer particle size determinations (B12 nm), indicating size retention during crystallization and a similar (but this time two stage) crystallization mechanism was proposed. Most importantly, however, this work discussed the role of the Zn 2+ ions which appear to act as both nucleating and structure directing agents-an observation latterly confirmed by the in situ Raman measurements of the organic template conformation performed by O'Brien et al 70 Most recently Simmance et al 71 again utilized combined XAS/WAXS to examine CoAPO-5 formation.…”

“…The basic experimental setup is demonstrated in Fig. 9 (with examples of the data recorded separately by Grandjean) and, as demonstrated by Beale et al, 67 the cell and setup is flexible enough to allow these measurements to be performed in a single combined experiment. Here the XANES underwent similar changes to Sankar et al, 66 however a detailed analysis of the high quality XAS data revealed more complex variations in the Fourier transform of the EXAFS.…”

A Combined Multi-Technique In Situ Approach Used to Probe the Stability of Iron Molybdate Catalysts During Redox Cycling

“…The use of synchrotron light sources has, for a number of decades now, provided a way to examine catalysts under increasingly more realistic conditions [1][2][3][4][5][6]. The continued development of more brilliant and powerful light sources along with improved detectors has more recently allowed for the combination of two and three X-ray based in situ techniques [1,[7][8][9][10][11][12]. Information can now be collected on various parts of the catalyst congruently revealing additional insight into their operation under various conditions.…”

Nucleation, Growth, and Aggregation of Mineral Phases: Mechanisms and Kinetic Controls

“…However, the PDF was not fully Gaussian in shape and this may indicate that asymmetry in the bond length distribution could also have contributed to the observed increase in radius. When they compared the WAXS analyses with the XAS data however, the agreement was not so good although the WAXS and molecular dynamic modeling fitted better (see also examples below in the XAS section and Beale et al, 2006).…”