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, PiFM）是一种纳米分析技术，可同步采集原子力显微镜（Atomic Force Microscopy, AFM）形貌数据与红外（infrared, IR）物相识别信息。该技术利用样品表面与安装在原子力显微镜上的尖锐金属涂层悬臂尖之间的吸引力，在可调谐红外激光照射下可实现约5 nm的空间分辨率（Nowak等人，2016；Otter等人，2021）。 由于其高灵敏度可实现分子单层的检测，光诱导力显微镜尤其适用于纳米尺度物相的识别与可视化，可作为扫描/透射电子显微镜（Scanning/Transmission Electron Microscopy, S/TEM）、原子探针断层扫描（Atom Probe Tomography）等其他纳米成像与元素分析技术的优秀补充（例如Otter等人，2023）。 光诱导力显微镜的样品制备面临诸多挑战，需克服这些挑战才能实现无伪影成像与准确的结果解读。这一点至关重要，因为用于固定、抛光与存储样品的材料可能会在样品表面留下分子痕迹，从而使数据解读变得复杂。因此，本光谱库收录了传统样品制备与存储材料的光诱导力显微镜光谱，可助力分析过程中潜在污染源的识别与规避。 光谱库工作表（补充表1）收录了所有测量值的平均值与一阶标准差（±1σ，原文标注为±1s），并针对三种激光波数范围（755~1875 cm⁻¹，对应Block Engineering量子级联激光器（quantum cascade laser）；2000~2400 cm⁻¹，对应DRS Daylight Solutions MIRcat量子级联激光器；2400~4400 cm⁻¹，对应EKSPLA PT200光学参量振荡器（optical parametric oscillator））下所有被测样品制备与存储材料的光谱进行了归一化处理（归一化至最高强度）。 光谱库之后的工作表收录了经分析的样品（补充表2）。 参考文献： 1. Förster, M. W., Chen, C., Foley, S. F., Alard, O., Yaxley, G. M. (2024). 弧前流体流失调控俯冲带氮循环效率. *Chemical Geology*, 121985. 2. 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. & Park, S. (2016). 光诱导力显微镜实现纳米尺度化学成像. *Science Advances*, 2, e1501571. 3. 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前沿综述：光诱导力显微镜的纳米化学成像：技术要点及其在地球科学中的应用. *Geostandards and Geoanalytical Research*, 45(1), 5-27. 4. Otter, L.M., Eder, K., Kilburn, M.R., Yang, L., O’Reilly, P., Nowak, D.B., Cairney, J.M., Jacob, D.E. (2023). 天然珍珠母的生长动力学及非晶态-晶态相变过程. *Nature Communications*, 14(1), 2254.