A PiFM spectral library for the identification of molecular contaminants in geochemical laboratories

Photo-induced Force Microscopy (PiFM) is a nanoanalytical technique that merges the simultaneous acquisition of Atomic Force Microscopy (AFM) topographic data with infrared (IR) phase identification. By using the attractive forces between a sample surface and a sharp, metal-coated cantilever tip mounted on an AFM, PiFM achieves a spatial resolution of approximately 5 nm when illuminated with a tunable IR laser (Nowak et al., 2016; Otter et al., 2021). Due to its high sensitivity that allows for the detection of molecular monolayers, PiFM is particularly effective for identifying and visualizing phases on the nanoscale, making it an excellent complement to other nanoscale imaging and elemental analysis techniques such as Scanning/Transmission Electron Microscopy (S/TEM) and Atom Probe Tomography (e.g., Otter et al., 2023).
Sample preparation for PiFM poses significant challenges that must be overcome for artifact-free imaging andaccurate interpretation. This is critical as the materials used for mounting, polishing, and storing can leave molecular traces on the sample surfaces, which can complicate data interpretation. Hence, this spectral library presents PiFM spectra of traditional sample preparation and storage materials that will help identify and avoid potential contamination sources during analyses.
The spectral library tab (Sup Table 1) includes the averages and first standard deviations (± 1s) of all measurments, normalized to the highest intensity for all measured sample preparation and storage materials for the three laser wavenumber ranges 755-1875 cm-1 (Block Engineering quantum cascade laser), 2000-2400 cm-1 (DRS Daylight Solutions MIRcat quantum cascade laser), and 2400-4400 cm-1 (EKSPLA PT200 optical parametric oscillator). The tab following the spectral library lists the analysed products (Sup Table 2).

References:
Förster, M. W., Chen, C., Foley, S. F., Alard, O., Yaxley, G. M. (2024). Fluid loss to the fore-arc controls the recycling efficiency of nitrogen in subduction zones. Chemical Geology, 121985.
Nowak D., Morrison W., Wickramasinghe H.K., Jahng J., Potma E., Wan L., Ruiz R., Albrecht T.R., Schmidt K., Frommer J., Sanders D.P. and Park S. (2016) Nanoscale chemical imaging by photoinduced force microscopy. Science Advances, 2, e1501571.
Otter, L.M., Förster, M.W., Belousova, E., O’Reilly, P., Nowak, D., Park, S., Clark, S., Foley, S.F., Jacob, D.E. (2021) GGR Cutting-Edge Review: Nanoscale Chemical Imaging by Photo-Induced Force Microscopy: Technical Aspects and Application to the Geosciences. Geostandards and Geoanalytical Research, 45(1), 5-27.
Otter, L. M., Eder, K., Kilburn, M. R., Yang, L., O’Reilly, P., Nowak, D. B., Cairney, J. M., Jacob, D. E. (2023). Growth dynamics and amorphous-to-crystalline phase transformation in natural nacre. Nature Communications, 14(1), 2254.

光诱导力显微镜（Photo-induced Force Microscopy，简称 PiFM）是一种纳米级分析技术，它将原子力显微镜（Atomic Force Microscopy，简称 AFM）的拓扑数据采集与红外（Infrared，简称 IR）相位识别同步进行。通过利用样品表面与锐利的、金属涂覆的悬臂梁尖端（安装在 AFM 上）之间的吸引力，PiFM 在使用可调谐红外激光照射时，可以达到约 5 纳米的空间分辨率（Nowak 等人，2016；Otter 等人，2021）。由于其高灵敏度，能够检测分子单层，PiFM 特别适用于识别和可视化纳米尺度上的相，从而成为扫描/透射电子显微镜（Scanning/Transmission Electron Microscopy，简称 S/TEM）和原子探针层析术（Atom Probe Tomography）等纳米尺度成像和元素分析技术的绝佳补充（例如，Otter 等人，2023）。PiFM 的样品制备面临着巨大的挑战，这些挑战必须被克服，以实现无伪影的成像和准确的解释。这一点至关重要，因为用于安装、抛光和储存的材料可能会在样品表面上留下分子痕迹，从而复杂化数据解释。因此，本光谱库展示了传统样品制备和储存材料的光诱导力显微镜光谱，这将有助于在分析过程中识别和避免潜在的污染源。光谱库标签（附表 1）包括所有测量的平均值和第一次标准差（± 1s），并归一化到所有测量的样品制备和储存材料的最高强度，涵盖三个激光波数范围：755-1875 cm-1（Block Engineering 量子级联激光器）、2000-2400 cm-1（DRS Daylight Solutions MIRcat 量子级联激光器）和 2400-4400 cm-1（EKSPLA PT200 光参量振荡器）。光谱库标签之后列出的是分析产物（附表 2）。