Kaszowska Zofia, Malek Kamilla, Staniszewska-Slezak Emilia, Niedzielska Karina
Faculty of Conservation and Restoration of Works of Art, Jan Matejko Academy of Fine Arts in Krakow, 27-29 Lea Street, 30-052 Krakow, Poland.
Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland.
Spectrochim Acta A Mol Biomol Spectrosc. 2016 Dec 5;169:7-15. doi: 10.1016/j.saa.2016.06.012. Epub 2016 Jun 7.
This work presents an in-depth study on Raman spectra excited with 1064 and 532nm lasers of lime binders employed in the past as building materials and revealed today as valuable conservation materials. We focus our interest on the bands of strong intensity, which are present in the spectra of all binders acquired with laser excitation at 1064nm, but absent in the corresponding spectra acquired with laser excitation at 532nm. We suggest, that the first group of spectra represents fluorescence phenomena of unknown origin and the second true Raman scattering. In our studies, we also include two other phases of lime cycle, i.e. calcium carbonate (a few samples of calcite of various origins) and calcium oxide (quicklime) to assess how structural and chemical transformations of lime phases affect the NIR-Raman spectral profile. Furthermore, we analyse a set of carbonated limewashes and lime binders derived from old plasters to give an insight into their spectral characteristics after excitation with the 1064nm laser line. NIR-Raman micro-mapping results are also presented to reveal the spatial distribution of building materials and fluorescent species in the cross-section of plaster samples taken from a 15th century chapel. Our study shows that the Raman analysis can help identify lime-based building and conservation materials, however, a caution is advised in the interpretation of the spectra acquired using 1064nm excitation.
这项工作对过去用作建筑材料、如今被视为珍贵保护材料的石灰粘结剂在1064纳米和532纳米激光激发下的拉曼光谱进行了深入研究。我们关注的是高强度谱带，这些谱带出现在用1064纳米激光激发采集的所有粘结剂光谱中，但在用532纳米激光激发采集的相应光谱中却不存在。我们认为，第一组光谱代表来源不明的荧光现象，第二组代表真正的拉曼散射。在我们的研究中，我们还纳入了石灰循环的另外两个阶段，即碳酸钙（各种来源的方解石的几个样品）和氧化钙（生石灰），以评估石灰相的结构和化学转变如何影响近红外拉曼光谱轮廓。此外，我们分析了一组来自旧灰泥的碳酸化石灰乳和石灰粘结剂，以深入了解它们在1064纳米激光线激发后的光谱特征。还展示了近红外拉曼微观映射结果，以揭示从一座15世纪教堂采集的灰泥样品横截面中建筑材料和荧光物质的空间分布。我们的研究表明，拉曼分析有助于识别基于石灰的建筑和保护材料，然而，在用1064纳米激发采集的光谱解释中建议谨慎。
