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Fourier transform Raman spectroscopy and (dispersive) confocal Raman microscopy have been applied to quantitatively and qualitatively describe the local distribution of chemical moieties of poly(styrene- co -maleimide) coatings on paper substrates containing different amount of imide. In parallel, local coating defects have been imaged for a better understanding of the influence of the coating composition on homogeneity at macro- to microscale levels. From FT-Raman spectroscopy, the imide content was calculated in quantitative agreement with previous thermoanalytical data. From dispersive spectroscopy, the measuring parameters were optimized for single-point measurements including signals of the coating and macropoint measurements including more intense signals of the paper. The large surface maps (5 × 5 mm 2 ) provided good quantification for the lateral distribution of imide moieties and coverage for coatings with different thickness and imide content, based on relative intensities of imide/styrene and imide/cellulose bands. The inhomogeneities were related to the formation of surface patterns for coatings with high viscosity and presence of non-imidized residues. From detailed surface maps (1 × 1 mm 2 ), sensitive Raman bands were selected to describe variations in imide and styrene concentrations, conformations and interactions with fillers and cellulose. Based on data from Raman analysis, interactions between nanoparticles and cellulose possibly happened through hydrogen bonding. [ABSTRACT FROM AUTHOR]

To advance our understanding of the molecular biochemistry of fungi which impact cultural heritage in libraries, museums and archives we investigated the diagnostic capacity of Raman spectroscopy to identify the composition of colored chromophores of fungi on paper. In this study we explored the diagnostic capacity of resonant Raman to distinguish chromophores in fungal filaments stimulated to grow on paper under high humidity with a focus on characterizing chromophores of Alternaria group species. To facilitate molecular analysis, we conducted quantum chemistry calculations of representative metabolites having optical absorption in the ultraviolet–visible spectral range. Comparing theory and experiment we show that fonsecin, erythroglaucin and aurasperone type chromophores occur in mature hyphal filaments with β-carotene dominant in yeast depositions on paper surfaces. Resonant Raman of mature filaments suggests a further contribution of carotenes longer than β-carotene to the spectral signature. Using microscopic resolution, we distinguish rich sets of Raman signatures that we assign to lignin, flavoglaucin, riboflavin, cycloleucomelon(e) and asperyellone molecular components in the spatial regions where filaments initiate from yeast depositions. In such regions, where filament microstructures stimulate development of a mature three-dimensional scaffold, the diversity of Raman resonances confirms a rich biochemistry of the developing structures. The library of computed optical and spectroscopic responses of characteristic fungal chromophores and metabolites presented here is essential for understanding the effect of fungi on a wide range of objects made from paper including books, prints, drawings, watercolors, engravings and even sculptures as well as designing next generation materials based on fungal hyphal mats. • Non-invasive Raman spectroscopy can be used to identify pigments in fungi. • Quantum chemistry (DFT) combined with Raman for quantitative measure of chromophores. • Computed optical responses of fungal chromophores and metabolites. • Raman spectroscopy combined with Quantum chemistry as tools for cultural heritage. • Alternaria sp. generates specific pigments when grown on paper. [ABSTRACT FROM AUTHOR]

The creation of functional papers requires a specific deposition of chemical moieties at the surface. In particular, water-repellent barrier coatings can be formed by the deposition of (poly(styrene-co-maleimide) nanoparticles filled with different vegetable oils. The analysis of coated paper surfaces by dispersive Raman spectroscopy allows for statistical classification of different coating types and chemical mapping of the lateral surface distribution of the coating components. The Raman spectra were used to quantify the amount of free oil and imide content. The partial least squares model with three principal components (PC) could differentiate between the type of oil (degree of saturation in PC-1), coating thickness (cellulose bands of paper substrate in PC-2), and organic coating phase (styrene, imide in PC-3). The chemical surface maps with average intensities indicate coating inhomogeneities for thin coatings located near the organic coating components, while the presence of free oil acts as a natural binder in between the organic phase and provides a more homogeneous coating. Depending on the type of oil, a higher amount of free oil coincides with lower imide content at the surface. The surface coverage of polyunsaturated oils overlaps relatively well with the areas of organic coating components, as the oil is largely encapsulated. The surface coverage for mono- and unsaturated oils is rather complementary to the organic phase as there are larger amounts of free oil. The latter is confirmed by single wavenumber maps and image processing constructing composite chemical surface maps. [ABSTRACT FROM AUTHOR]