Characterization of crystalline cellulose in biomass: Basic principles, applications, and limitations of XRD, NMR, IR, Raman, and SFG

Cellulose is among the most important and abundant biopolymers in biosphere. It is the main structural component of a vast number of plants that carries vital functions for plant growth. Cellulose-based materials have been used in a variety of human activities ranging from papers and fabrics to engineering applications including production of biofuels. However, our understanding of the cellulose structure in its native form is quite limited because the current experimental methods often require separation or purification processes and provide only partial information of the cellulose structure. This paper aims at providing a brief background of the cellulose structure and reviewing the basic principles, capabilities and limitations of the cellulose characterization methods that are widely used by engineers dealing with biomass. The analytical techniques covered in this paper include x-ray diffraction, nuclear magnetic resonance, and vibrational spectroscopy (infrared, Raman, and sum-frequency-generation). The scope of the paper is restricted to the application of these techniques to the structural analysis of cellulose.