Pure component Raman spectral reconstruction from glazed and unglazed Yuan, Ming, and Qing shards: a combined Raman microscopy and BTEM study

Abstract

Raman mapping measurements were performed on the glazed and unglazed surfaces of shards excavated from Yuan, Ming, and Qing dynasty strata. A number of areas on each surface were chosen. Circa 21 × 21 pixels were measured for each area using both 514 and 785-nm laser as the Raman excitation. Data were collected from 100-3600 cm −1 . Many sets of spectra exhibited very intense fluorescence. In spite of the intense fluorescence, the resulting sets of spectra were collated and analyzed together using the band-target entropy minimization (BTEM) algorithm. Pure component spectral estimates of many of the major components were achieved, without the use of any a priori information such as spectral libraries. These include α-silica quartz, carbon, anatase, cobalt oxides, hematite, glassy silicate, and lanthanide complexes. In addition, two further unidentified pure component spectra A and B were recovered as well as an interference pattern due to the microscopic texture of the shards (associated with small particle/thin layer domains). The carbon was primarily present in elemental form, i.e. mixture of amorphous and graphitic (unordered and ordered domains); however there is an evidence of some partial oxidation, i.e. formation of carboxylates. The interference patterns and the lanthanide complexes were only observed when using the longer wavelength red laser. The cobalt oxides and the anatase were only observed when using the green laser. In summary, the combination of Raman microscopy and BTEM has allowed the enumeration of many of the underlying spectral patterns present and hence unambiguous identification of the major individual components present in the archaeological samples. This approach would appear applicable to other classes of archaeological materials as well. Limitations and extensions of the present approach are discussed.

Porcelain shards from Portuguese wrecks: Raman spectroscopic analysis of marine archaeological ceramics

“…However, the spectra shown in Figs. 2, 3 and 5 have significantly more structure and bare a great similarity to recent data published by Widjaja et al [17] who investigated a range of glazed and unglazed Yuan, Ming and Qing shards using a combination of Raman microspectroscopy and band-target entropy minimization (BTEM) which is a self-modeling curve resolution technique. The analysis of over 3700 spectra collected using an excitation wavelength of 785 nm resulted in the reconstruction of six pure component spectra.…”

“…No evidence of rutile with the characteristic strong doublet at ~610 and 445 cm −1 were observed in these spectra. Although amorphous carbon has been observed in the spectra collect from other Ming porcelain samples [10,14,17] it was not observed in the data collected from these samples.…”

Amino‐methyl coumarin as a potential SERS@Ag probe for the evaluation of protease activity and inhibition

“…Let k represent the number of spectra measured and let ν represent the number of spectroscopic channels, then the intensity matrix M k×ν can be transformed to obtain each pure component spectral estimate. The procedure has been described in Widjaja & Garland . The set of data used corresponds to the nine spectra obtained as a function of time (Fig.…”

Raman spectroscopy of minerals and mineral pigments in archaeometry

“…Rarely, multivariate analysis can be used to distinguish minerals in ceramics or to group and classify ceramics from the identified mineral phases . In particular, to discriminate Raman signals of the different ceramic components in case of high fluorescence background, band‐target entropy minimization, a self‐modelling curve resolution technique, was proposed . The resulting pure component spectra show an excellent signal‐to‐noise ratio.…”