Spectroscopic Characterization and Dye-Fibre Affinity of Plant-Based Textile Dyes on Natural Fibres

The increasing environmental and health hazards associated with synthetic textile dyes have necessitated intensive research into plant-based alternatives. This study presents a systematic spectroscopic characterization and dye-fibre affinity investigation of fifteen plant-derived textile dyes extracted from leaves, bark of trees, roots, fruit peels, and sheaths from plant materials sourced in Osun and Oyo States, Nigeria. Aqueous extraction was employed, and the extracted dyes were applied to cotton and silk fabrics using three mordants, alum, lemon juice, and cocoa pod ash, through pre-mordanting, simultaneous mordanting, and post-mordanting techniques. Characterization was conducted using Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet-Visible (UV-Vis) spectroscopy to identify functional groups and chromophoric systems. FTIR analysis revealed the presence of hydroxyl groups (O-H stretching, 3267–3337 cm⁻¹), C=C stretching (1620–1680 cm⁻¹), and C-O stretching (1000–1055 cm⁻¹) across all samples, consistent with phenolic compounds, tannins, and flavonoids. UV-Vis analysis identified strong absorption bands in the 200-;400 nm range, with extended conjugation in neem bark, cashew bark, and brimstone root. Fastness evaluation showed that cotton consistently outperformed silk in wash, light, and rubbing fastness, with bark-derived dyes demonstrating the highest performance (ratings 4–5). Alum and cocoa pod ash mordants produced superior fastness compared to lemon juice. The findings demonstrate the viability of these plant-derived dyes for sustainable textile applications and contribute scientific evidence to support their adoption in studio practice and cottage textile industries.