Design of a multi-well plate for high-throughput characterization of heterogeneous catalysts by XRD, FT-IR, Raman and XRF spectroscopies

For powder catalyst characterization, Fourier Transform Infrared (FTIR), Raman, and X-Ray Fluorescence (XRF) spectrometers and X-Ray Diffraction (XRD) are available in high-throughput (HT) configurations, for example at the REALCAT platform to sequentially analyse multiple sets of samples. To remove the bottleneck resulting from the use of different sample holders for each equipment, a unique multi-well plate was developed. This paper details the design of such a plate including the selection of the fabrication material and the plate dimensioning based on the study of the 4 different physical interactions between matter and electromagnetic radiations for the aforementioned techniques. This new plate consists of a holder for removable wells enabling the avoidance of cross-contamination between samples. Raman, a focusing technique, has no strict constraint on the plate design. The number of wells, their geometry, spacing and dimensions were adjusted to deal with the constraints of IR optics. The well depth was set according to the XRF maximum penetration depth in the sample. The well diameter was optimized in order to obtain from the X-ray spot size the maximum achievable intensity. Poly-methyl-methacrylate (PMMA) was chosen as the material for the new plate due to its amorphous structure (no peak in XRD analysis) and ease with which it can be cut by a laser. Finally, the flatness of the multi-well plate was validated on the most challenging instrument: XRD. This new plate allows fast sample filling/preparation, requires small quantities of catalyst (50 to 80 mg) in each well and is compatible and convenient for HT experimentation.