Abstract:In situ investigations on the nucleation and crystallization processes are essential for understanding of the formation of solids. Hence, the results of such experiments are prerequisites for the rational synthesis of solid materials. The in situ approach allows the detection of precursors, intermediates, and/or polymorphs, which are mainly missed in applying ex situ experiments. With a newly developed crystallization cell, simultaneous in situ experiments with X-ray diffraction (XRD) and luminescence analysis are possible, also monitoring several other reaction parameters. Here, the crystallization of the model system tris(acetylacetonato)-aluminum(III) Al(acac) 3 was investigated.In the time-resolved in situ XRD patterns, two polymorphs of Al(acac) 3 , the α-and the γ-phase, were detected at room temperature and the influence of the pH value onto the product formation was studied. Moreover, changes in the emission of Al(acac) 3 and the light transmission of the solution facilitated monitoring the reaction by in situ luminescence. The first results demonstrate the potential of the cell to be advantageous for controlling and monitoring several reaction parameters during the crystallization process.

Here, we introduce the principle of the novel in situ luminescence analysis of coordination sensor (ILACS) approach for monitoring the formation of solid materials, recording information from the formed solid compounds as well as from the surrounding solutions. This technique utilizes as a main tool the sensitivity of luminescence properties of lanthanide (Ln) ions on the coordination environment, being incorporated as local sensors by the investigated material during synthesis. The luminescence spectra and their environment-dependent developments are monitored in situ from the early stages of the reaction until the final product formation under real conditions with a high time resolution. The ILACS principle is demonstrated here for monitoring the formation of [Eu(phen)2(NO3)3] (phen = 1,10-phenanthroline) and further metal-ligand exchange processes during its conversion to [Sn(phen)Cl4]. These reactions were followed, for instance, analyzing the antenna effect, shift of the (5)D0→(7)F4 Eu(3+) transition and quenching effects. In addition, these results have been validated by comparison with other in situ techniques. The results demonstrate that ILACS is a new powerful, fast, broadly available in situ characterization method, which is applicable for liquids, amorphous samples, and very small crystallites besides for large crystals.

In this work, in situ luminescence analysis was applied for the first time for monitoring the phase transitions of calcium phosphate (CaP) and confirmed by synchrotron in situ X-ray diffraction in addition to in situ infrared spectroscopy, with simultaneous measurements of pH and ion conductivity. Applying doped Ce 3+ and Eu 3+ as local coordination sensors, the high sensitivity of their emission spectra upon the changes in the coordination sphere of the doped cation sites enabled to detect the formation of amorphous calcium phosphate (ACP) and Ca 5 (PO 4 ) 3 OH, besides their subsequent transitions to CaHPO 4 ·2H 2 O and Ca 8 H 2 (PO 4 ) 6 ·5H 2 O under real reaction conditions. Calcium phosphates are widely present in mammals and understanding their phase transitions is important to comprehend the conversion between healthy and diseased tissues. In situ luminescence measurements are advantageous for allowing monitoring these phase transitions in a fast and sensitive fashion also in conventional laboratories, independent of synchrotron radiation.