Guerra I, Cardell C
Scientific Instrumentation Centre, Avda. Campus Fuentenueva, University of Granada, 18071, Granada, Spain.
Department of Mineralogy and Petrology, Faculty of Science, University of Granada, Campus Fuentenueva s/n, 18071, Granada, Spain.
J Microsc. 2015 Oct;260(1):47-61. doi: 10.1111/jmi.12265. Epub 2015 May 13.
The novel Structural Chemical Analyser (hyphenated Raman spectroscopy and scanning electron microscopy equipped with an X-ray detector) is gaining popularity since it allows 3-D morphological studies and elemental, molecular, structural and electronic analyses of a single complex micro-sized sample without transfer between instruments. However, its full potential remains unexploited in painting heritage where simultaneous identification of inorganic and organic materials in paintings is critically yet unresolved. Despite benefits and drawbacks shown in literature, new challenges have to be faced analysing multifaceted paint specimens. SEM-Structural Chemical Analyser systems differ since they are fabricated ad hoc by request. As configuration influences the procedure to optimize analyses, likewise analytical protocols have to be designed ad hoc. This paper deals with the optimization of the analytical procedure of a Variable Pressure Field Emission scanning electron microscopy equipped with an X-ray detector Raman spectroscopy system to analyse historical paint samples. We address essential parameters, technical challenges and limitations raised from analysing paint stratigraphies, archaeological samples and loose pigments. We show that accurate data interpretation requires comprehensive knowledge of factors affecting Raman spectra. We tackled: (i) the in-FESEM-Raman spectroscopy analytical sequence, (ii) correlations between FESEM and Structural Chemical Analyser/laser analytical position, (iii) Raman signal intensity under different VP-FESEM vacuum modes, (iv) carbon deposition on samples under FESEM low-vacuum mode, (v) crystal nature and morphology, (vi) depth of focus and (vii) surface-enhanced Raman scattering effect. We recommend careful planning of analysis strategies prior to research which, although time consuming, guarantees reliable results. The ultimate goal of this paper is to help to guide future users of a FESEM-Structural Chemical Analyser system in order to increase applications.
新型结构化学分析仪（配备X射线探测器的联用拉曼光谱和扫描电子显微镜）越来越受欢迎，因为它可以对单个复杂的微小样本进行三维形态学研究以及元素、分子、结构和电子分析，而无需在仪器之间转移样本。然而，在绘画遗产领域，它的全部潜力仍未得到充分发挥，因为在绘画中同时识别无机和有机材料这一关键问题尚未得到解决。尽管文献中显示了其优缺点，但在分析多面的油漆样本时仍需面对新的挑战。扫描电子显微镜 - 结构化学分析仪系统各不相同，因为它们是根据要求专门制造的。由于配置会影响优化分析的程序，同样地，分析协议也必须专门设计。本文探讨了配备X射线探测器拉曼光谱系统的可变压力场发射扫描电子显微镜分析历史油漆样本的分析程序优化。我们讨论了分析油漆地层、考古样本和松散颜料时出现的基本参数、技术挑战和局限性。我们表明，准确的数据解释需要全面了解影响拉曼光谱的因素。我们解决了以下问题：（i）场发射扫描电子显微镜 - 拉曼光谱分析顺序，（ii）场发射扫描电子显微镜与结构化学分析仪/激光分析位置之间的相关性，（iii）不同可变压力场发射扫描电子显微镜真空模式下的拉曼信号强度，（iv）场发射扫描电子显微镜低真空模式下样本上的碳沉积，（v）晶体性质和形态，（vi）焦深，以及（vii）表面增强拉曼散射效应。我们建议在研究之前仔细规划分析策略，虽然这很耗时，但能保证结果可靠。本文的最终目标是帮助指导场发射扫描电子显微镜 - 结构化学分析仪系统的未来用户，以增加其应用。
