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This study aims to study the possibility of distinguishing the UV–Vis–NIR spectra of filamentous fungi on a paper substrate from the background. Model samples of five filamentous fungi were used: Alternaria alternata, Aspergillus niger, Cladosporium herbarum, Penicillium chrysogenum, and Trichoderma atroviride. The model samples were cultivated on paper substrates, and two methods, cross-validation (CV) and principal component analysis (PCA), were utilised to compare their spectra with the reference background spectra. The results of the CV analysis indicated that certain combined spectra sets of Cladosporium herbarum, Penicillium chrysogenum, Trichoderma atroviride, Aspergillus niger, and Alternaria alternata, at specific surface concentrations, exhibited two active components, signifying distinguishable differences from the background spectra. Additionally, the score scatter diagrams derived from PCA revealed clusters of samples, further confirming the distinguishability of the filamentous fungi spectra from the background. However, for Trichoderma atroviride, the scatter diagram demonstrated a relatively large scattering of points, impeding the resolution of spectra with a surface concentration of 2 105cm−2due to measurement inaccuracies. Based on the combined results of CV and PCA, the study concluded that the lower threshold of measurability for UV–Vis–NIR spectra varied among the different filamentous fungi. For example, Cladosporium herbarum, Penicillium chrysogenum, and Trichoderma atrovirideexhibited a threshold around a surface concentration of 2 106cm−2, while Aspergillus nigerhad a threshold around 2 105cm−2, and Alternaria alternatahad a threshold around 2 103cm−2. In summary, this research provides insights into the distinguishability of filamentous fungi spectra on the paper substrate from background spectra using spectral analysis techniques, offering potential applications in fungal identification and characterisation.

Microorganisms, especially microscopic filamentous fungi, represent one of the most significant factors influencing the degradation of cultural heritage cellulosic objects. Early detection, identification and characterisation of microbial communities can help select a suitable conservation intervention and, in addition, allow possible control of its effectiveness. A combination of spectral methods and statistical data processing appears to be a suitable alternative to conventional methods for monitoring microbial contamination. The main goal of the presented research was the investigation of the spectral properties of vital and devitalised filamentous fungi Alternaria alternata, Aspergillus niger, Cladosporium herbarum, Penicillium chrysogenum, and Trichoderma atroviride, inoculated on a paper substrate Whatman in two phases—dormant (conidia) and active (mycelium). The combination of the UV-Vis-NIR and NIR Fibre Optics Reflection Spectroscopy (FORS) with the Principal Component Analysis (PCA) was set to determine whether the spectra of vital and devitalised forms of studied samples differ. The obtained results prove differences between the spectra of vital and devitalised forms of filamentous fungi, at least in one studied spectral region. Therefore, UV-Vis-NIR and NIR FORS combined with PCA seems to be a promising tool for monitoring paper-based objects' microbial contamination.

Research into paper artworks and the identification of drawing techniques dating from the 15th to the 19th century from the collection of Slovak National Gallery revealed that the most frequently used means of writing was a set of brown-gray inks. This set includes bistre, sepia, and iron-gall inks (IGI). The light fastness of these organic compounds is not considered very high. Moreover, iron gall inks attack paper support by the processes commonly known as iron gall ink corrosion. In the experimental part of the research, the stability of three different brown-gray inks was studied. Model inks, i.e. bistre, sepia and IGI with two molar ratios Fe : gallic acid were prepared according to historical recipes. Whatman paper was used as a support material. Samples were submitted to accelerated aging in closed vessels at 100°C with and without the presence of NO2in concentration of 100 ppm as well as to the light aging in a light chamber. Changes of mechanical, optical and chemical properties of the samples as well as spectra in the IR region were studied. The observed changes allowed an evaluation of the effect of particular inks on paper support and effect of various external factors of aging (temperature, light, pollutants) on the model systems. Simultaneous thermal analysis (DTA/TG) was carried out in order to study the thermo-oxidative stability of the materials. Sepia and bistre inks have been assessed as generally more stable than iron-gall inks.

This paper presents a novel approach in non-destructive analysis of inkjet-printed documents. Our method is based on the combination of molecular spectroscopy in the Near Infrared Region (NIR) and a chemometric method - principal component analysis (PCA). The aim of this work was to prepare spectral data for the analysis of the interrelationships between 19 samples consisting of the same type of office paper on which black squares were full printed in black ink only. The spectra were obtained separately using the Ocean Optics System in two spectral regions, i.e., overtones: 1000-1600 nm and combination bands: 1600-2300 nm, with the paper base. Experimental results confirmed the high reliability of the proposed approach despite the sparse dataset.

Raman spectroscopy and surface enhanced Raman spectroscopy were used to examine 14 blue inks obtained from commercially available stationery. Standard colouring agents in the inks: β-phase of phtalocyanine blue PB15 and some homologues of the methyl violet class, were identified. Surface enhanced Raman spectra were recorded on a firm heterostructure of silver/nanocrystalline diamond/silicon constituting an active substrate providing the possibility to write directly on the surface. Based on the differences in traditional and surface enhanced Raman spectra, two inks were identified unambiguously, the remaining inks were categorised into three groups exhibiting common spectral features. Despite their similarity, surface enhanced Raman spectra exhibited soft variations enabling discrimination of the inks, thus proving the usefulness of the method.

Photoactive TiO2 layers were formed by anodic oxidation of Ti in O2 RF plasma under various conditions and Ti surface pretreatment. The photocurrent spectrum in 1M NaOH was used to calculate the quantum efficiency of the photocurrent production and the band-gap energy for indirect transitions. Photoelectrochemical properties of TiO2 layers were studied on the decomposition of p-cresol water solution. The method of Ti surface pretreatment (mechanical polishing or chemical etching) has a decisive influence on the photoelectrochemical properties and the structure of the polycrystalline oxide, rutile, anatase or amorphous phase content.