Characterising synthetic dyes on heritage textiles represents a relatively recent research frontier, which aims to obtain new information about the evolution of textile manufacturing and industrial chemistry. Whilst spectral enhancement or amplification methods are often considered a requirement for the Raman analysis of textile dyes, this work highlights the potential of standard Raman spectroscopy for the non-invasive analysis of synthetically dyed fibres. In this research, Raman spectroscopy was used for the chemical characterisation of early 20th century synthetic dyes, in both powder form and on dyed fibres. The dyes were produced by the Italian company Azienda Coloranti Nazionali e Affini (ACNA) and housed in the Sapienza University Museum of Chemistry. The investigation first employed literature research into the ACNA's commercial nomenclature. This information was used to hypothesise likely molecular structures of the dyes, pointing towards the azo dye class. The application of Raman spectroscopy confirmed these hypotheses and the high-quality spectra collected provided structural information about the dye molecules. Spectral features of azo-groups, aromatic moieties, and substituents were observable in spectra. Comparison with a Raman spectrum of wool allowed confident dye signal attribution, and some spectra displayed features linked to changes in the fibre during the dyeing process. Combining literature research and Raman vibrational information proved a powerful non-invasive approach for the characterisation of synthetic dyes, allowing molecular identification of some colorants and structural information for most. Standard Raman spectroscopy may provide a widely applicable, non-invasive method for acquiring information about synthetically dyed historical and artistic textiles in future research.

中文翻译：

---

20 世纪及其新色彩：利用拉曼光谱研究历史合成染料的分子结构

表征传统纺织品上的合成染料是一个相对较新的研究前沿，旨在获取有关纺织品制造和工业化学演变的新信息。虽然光谱增强或放大方法通常被认为是纺织染料拉曼分析的必要条件，但这项工作凸显了标准拉曼光谱在合成染色纤维非侵入性分析中的潜力。在这项研究中，拉曼光谱用于对 20 世纪早期合成染料（粉末形式和染色纤维上的）进行化学表征。这些染料由意大利公司 Azienda Coloranti Nazionali e Affini (ACNA) 生产，现藏于萨皮恩扎大学化学博物馆。该调查首先对 ACNA 的商业术语进行了文献研究。该信息用于假设染料的可能分子结构，指向偶氮染料类别。拉曼光谱的应用证实了这些假设，收集的高质量光谱提供了有关染料分子的结构信息。在光谱中可以观察到偶氮基团、芳香族部分和取代基的光谱特征。与羊毛拉曼光谱的比较可以确定染料信号的归属，并且一些光谱显示了与染色过程中纤维变化相关的特征。结合文献研究和拉曼振动信息，证明了一种强大的非侵入性合成染料表征方法，可以对某些着色剂进行分子鉴定，并获得大多数着色剂的结构信息。标准拉曼光谱可以提供一种广泛适用的、非侵入性的方法，用于在未来的研究中获取有关合成染色的历史和艺术纺织品的信息。