1. Moisture-dependent transition from strong to weak hydrogen bonding in wood polysaccharidesFilip Majstorović, Jakub Michal Sandak, 2026, original scientific article Abstract: Near-infrared (NIR) spectroscopy combined with multivariate analysis was employed to investigate moisture- dependent hydrogen bonding of water in softwood cell walls. Spectral variations at equilibrium moisture con- tents were analyzed using principal component analysis and perturbation-correlation moving-window two- dimensional correlation spectroscopy to distinguish water populations with varying hydrogen-bond strengths. A distinct transition in hydrogen-bonding behavior was identified at approximately 10% wood moisture content. Below this threshold, water was found to predominantly engage in strong hydrogen bonds within wood cell walls. Above 10% moisture content, the relative contribution of strong hydrogen bonds to the overall wood- water hydrogen bond network decreased, whereas weakly hydrogen-bonded population became increasingly dominant. Experiments on modified wood and isolated polymers indicated that this transition originates mainly from wood polysaccharides, while lignin plays a minor role. These findings provide strong evidence for distinct water populations in wood cell walls, distinguished by their intermolecular hydrogen-bonding energies and predominant at specific wood moisture contents
Keywords: infrared spectroscopy, wood-water interactions, hydrogen bonding, wood cell wall, cellulose
Published in RUP: 05.06.2026; Views: 275; Downloads: 10
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2. Photochemical behavior of colloidal lignin particles under controlled UV exposure : balancing self-stabilization and degradationJulia Tomasich, Rene Alexander Herrera Diaz, Anna Malgorzata Sandak, Michael Harasek, Stefan Beisl, Oihana Gordobil, 2025, original scientific article Abstract: Colloidal Lignin Particles (CLPs), with their polyphenolic structure, are promising sustainable alternatives to chemical UV filters. This study investigates the photochemical behavior of CLPs under ultraviolet irradiation synthetized from five different technical raw lignins (Alkali, Organosolv, two Enzymatic Hydrolyzed and Softwood Kraft Lignin) via solvent-shift procedure. The suspensions were irradiated using a self-developed UV-pen set-up and a commercially available UV chamber, enabling controlled UV exposure over time. Variations in the physicochemical properties of irradiated colloidal lignin particles were characterized by Multi-Angle Dynamic Light Scattering (MADLS), Fourier Transform Infrared Spectroscopy (FTIR) coupled with chemometrics, UV–Vis spectroscopy, and High-Performance Size Exclusion Chromatography (HP-SEC). CLPs exhibited comparable responses after 14 days of UV exposure, with alterations in particle chemistry, particularly in the formation of new functional groups and molecular rearrangement. Moreover, the photochemical stability of CLPs was found to be highly dependent on both their concentration and the nature of the dispersion medium (aqueous, hexane-based, and solid-state). At higher concentrations (1.8 mg/mL), CLPs demonstrated effective self-stabilization, while lower concentrations led to rapid degradation, resulting in the disappearance of particles and the formation of low-molecular-weight fragments. Additionally, Minimal photochemical changes were observed in non-aqueous or solid-state environments due to restricted molecular mobility. These findings provide valuable insights into the degradation pathways and stability across different environmental contexts, which can contribute to understanding the potential environmental impact of CLPs in aquatic ecosystems.
Keywords: biobased materials, lignin colloidal particles, photodegradation, UV-irradiation, spectroscopy
Published in RUP: 09.09.2025; Views: 955; Downloads: 8
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3. Feasibility of portable NIR spectrometer for quality assurance in glue-laminated timber productionJakub Michal Sandak, Peter Niemz, Andreas Hänsel, Juana Mai, Anna Malgorzata Sandak, 2021, original scientific article Keywords: near infrared spectroscopy, glue-laminated timber, glulam, delamination, quality assurance
Published in RUP: 18.10.2021; Views: 5178; Downloads: 27
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4. Oriented investigations on the application of NIR spectroscopy for the evaluation of the bonding quality of glued laminated timber from hardwoodPeter Niemz, Jakub Michal Sandak, Juana Mai, Andreas Hänsel, 2021, published scientific conference contribution abstract Keywords: wood gluing, ash wood, delamination, NIR spectroscopy, Micro-NIR, hyperspectral imaging, quality control
Published in RUP: 16.07.2021; Views: 3835; Downloads: 83
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5. Brain imaging with functional near-infrared spectroscopy in educational researchNežka Sajinčič, Anna Malgorzata Sandak, Jakub Michal Sandak, Andreja Istenič, 2021, published scientific conference contribution abstract Keywords: functional near-infrared spectroscopy (fNIRS), functional neuroimaging, educational research, ecological validity, electro-encephalography (EEG), functional magnetic resonance imaging (fMRI)
Published in RUP: 06.05.2021; Views: 3528; Downloads: 17
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7. Impact of drying process on kraft lignin : ligninwater interaction mechanism study by 2D NIR correlation spectroscopyOihana Gordobil, Rene Alexander Herrera Diaz, Faksawat Poohphajai, Jakub Michal Sandak, Anna Malgorzata Sandak, 2021, original scientific article Keywords: hardwood kraft lignin, drying temperature, DVS, NIR spectroscopy, 2D-COS
Published in RUP: 06.05.2021; Views: 4259; Downloads: 12
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8. A method for accelerated natural weathering of wood subsurface and its multilevel characterizationAnna Malgorzata Sandak, Jakub Michal Sandak, Marion Noël, Athanasios Dimitriou, 2021, original scientific article Keywords: photodegradation, wood weathering, SEM imaging, FT-IR spectroscopy, thin samples, accelerated natural weathering
Published in RUP: 04.02.2021; Views: 3122; Downloads: 41
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