Surface profiling of cellulose, hemicellulose, and lignin in softwood Kraft handsheets by reference-guided ToF-SIMS

Journal article, 2026

The surface composition of softwood Kraft fiber materials, particularly the relative contributions of cellulose, hemicelluloses, and lignin at fiber surfaces, strongly influences interfacial properties relevant to paper performance and surface modification. Because these properties are governed by the outermost fiber surface rather than by bulk composition alone, methods capable of resolving chemically heterogeneous lignocellulosic surfaces are needed. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is attractive for this purpose because it provides surface-sensitive and chemically resolved information, but its spectra are complicated by fragment overlap, adduct formation, matrix effects, and contamination. Here, a semi-quantitative ToF-SIMS workflow was developed using compacted reference samples, total-ion-count normalization, pairwise principal component analysis, and conservative marker-ion validation. Unbleached and bleached handsheets were used to assess whether the workflow could detect bleaching-induced chemical differences at softwood Kraft fiber surfaces. The analysis reproducibly differentiated lignin- and polysaccharide-associated ion patterns. Unbleached handsheets showed higher relative contributions from guaiacyl lignin-associated fragments, whereas bleached handsheets showed enhanced polysaccharide-associated signals. Two-dimensional chemical imaging supported these trends by visualizing the spatial distribution of assigned marker ions across the handsheet surfaces. The workflow provides a practical, semi-quantitative surface-characterization method for pulp fibers surfaces, fiber modification, adhesive and coating interfaces, and related bio-based material surfaces.