Automated Time-Delay Characterization and Data Synchronization for Operando Gas and Heating Systems

Time-resolved correlations between the sample environment, reaction products, energy transfer and material structures during reaction processes have made operando gas and heating TEM increasingly attractive in recent years. Due to the physical layout of any gas and heating system: gas flowing from a gas supply system, to a sample holder and then to a gas analyzer; time delays between measurements are unavoidable. Gas composition changes are measured in the gas supply system before they actually reach the sample, reactions products are measured inside the gas analyzer after they have travelled from the sample holder to the analyzer. These time delays can be optimized, by means of shortening the distance between the three parts of the system, but they cannot be avoided.<br/>These intrinsic time delays complicate the analysis of these gas and heating experiments where potentially erroneous conclusions can be drawn, such as overestimating the critical temperatures, or mismatching the structure and composition relationships to activities. Therefore, these time delays need to be calibrated for valid correlations and an unambiguous analysis of the experiment.<br/><br/>During this talk, I will present a method to measure and calibrate the time delays involved in operando TEM.[1] We have developed two open-source scripts to make the complete removal of time delays possible. Firstly, the time delay characterization script automatically fits a functional relationship for the two time delays (Pre-TEM to In-TEM and In-TEM to Post-TEM) and the pressure and flow in the system. It does so by automatically controlling the Gas and Heating system through the Impulse API and monitoring the measurements in real-time to determine the time delays. A characterization of the system can be performed once, after which the same calibration file is used to calibrate any data recorded at any time from the same system. Secondly, the data calibration script uses the functional relationships in the calibration file to remove the time delays from any dataset and synchronize the Pre-TEM and Post-TEM measurements with the In-TEM measurements. I will explain the full process during this presentation and showcase its use on application data.<br/><br/>[1] Zhang, F., Pen, M., Spruit, R. G., Perez Garza, H., Liu, W. & Zhou, D. (2021). Data Synchronization in Operando Gas and Heating TEM. ChemRxiv. Pre-print.