Solvothermal synthesis of nanoparticles takes place under elevated temperatures and pressures, which entails a need for steel vessels to contain the reactions. Meanwhile, the progress of the reaction chemistry is of great interest: The transitions from raw, dissolved precursor to atomic clusters, seed crystals and subsequent growth into nanoparticles.
Much may happen along this pathway, strongly influenced by synthesis parameters such as temperature, residence time, precursor concentration, etc. Over the past decade, the Iversen group has used, developed and refined a method to watch nanoparticles form, using a miniaturized reaction vessel which can be penetrated by X-rays.
An elegant way to gain insight into the nanoparticle formation and growth is by in situ X-ray scattering. The reaction vessel developed in the Iversen group can be penetrated by X-rays, giving “snapshot" diffractograms of the nanostructures with a time resolution of (typically) 1-4 seconds. The data may subsequently be reconstructed via Rietveld and PDF refinement to show development of atomic structures, particle sizes, morphologies, etc. The special technique called total scattering (Pair Distribution Function analysis) even enables modeling of reactant species in the raw precursor solution, thus providing a window into the entire transition from reactant to product. Our group has established this particular approach as an in situ technique, and provided the first atomic scale insight into the chemistry of nucleation.
The common X-ray sources used for these experiments are international synchrotrons, e.g. PETRA-III (Hamburg, Germany) ESRF (Grenoble, France) or APS (Chicago, USA). They alone provide the intensity required to obtain a single-second time resolution. However, pre-studies within a more limited parameter space may be carried out in the home laboratory using in-house diffractometers.
We have been involved in developing in situ PDF studies of thin films to watch them grow. Together with PETRA III we have developed a magnetron sputtering facility on the beamline, which allows following growth of thin films at atomistic level.
Moreover, our group has been involved in the design and development of the new DanMAX beamline at MAX IV in Lund, Sweden, which received first light in early June 2020, where the aim will be to investigate real materials in real time in real operating conditions using high energy X-rays.
Click on the links below to discover a selection of our recent publications on In situ X-ray diffraction studies.