Work

Molecular insights into diazonium salt binding and colour development in wood substrates

Year: 2025

Type: article

Abstract: Sustainable wood marking and tracking are essential for responsible forest management and the long-term conservation of natural resources. Functional modification of wood surfaces via azo coupling with diazonium salts offers a sustainable approach to coloration and marking. We investigate the substrate specificity and temporal dynamics of this reaction across softwood and hardwood species (oak, beech, and spruce), probing the roles of lignin, extractives, hemicellulose, and cellulose. Phenolic groups from lignin and extractives emerge as the primary reactive sites. While extractive content drives reaction kinetics in raw wood, overall coupling efficiency after their removal is strongly influenced by lignin composition—particularly the guaiacyl-to-syringyl ratio and degree of lignin condensation. Among the diazonium salts tested, Fast Black K (FB) exhibits superior performance, likely due to enhanced molecular planarity, stronger π-π stacking, and Zn²⁺ counterion effects that promote robust interactions with wood. Despite variations in salt and wood type, final coloration consistently converges towards reddish hues, as confirmed by CIELab measurements, reflecting lignin’s intrinsic chromophoric properties. This study highlights the interactions between wood components, their chemistry and diazonium salt design, that offers opportunities for controlled functionalization of wood surfaces.

Source: Dyes and Pigments

DOI: 10.1016/j.dyepig.2025.113202

Authors: Susanna Ortlieb, Avinash P. Manian, Thomas Bechtold, Tung Pham

Institution: Universität Innsbruck

Language: English

Topic: Lignin and Wood Chemistry

Subfield: Biomedical Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,590

Funders: Österreichische Forschungsförderungsgesellschaft, Universität Innsbruck