Characterisation of amino acid modified cellulose surfaces using ToF-SIMS and XPS

Cellulosic fibrous networks are modified using 3 different amino acids; small (Glycine, Gly), aliphatic (Leucine, Leu) and aromatic (Phenylalanine, Phe). The effect of amino acid functionality on chemical coupling to cellulose fibres in terms of their coverage and packing density are investigated. Different amino acid modified cellulose networks are characterised by using Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS). The presence of amino acids is confirmed using ToF-SIMS. The quantitative distribution of different amino acids across the cellulose surface is assessed by using XPS. It is shown that the packing density of amino acids depends on the size of the side chain; smaller amino acids (Gly, Leu) tend to couple to the surface at higher density compared to larger ones (Phe). This study has implications for the functionalisation of polysaccharide materials for a wide range of applications.