Synthesis and metrology of cellulose nanocrystal films

Cellulose nanocrystal (CNC) is an emerging nanomaterial that has drawn increasing attention recently. It is abundant, sustainable, renewable, and biodegradable. They have unique chemical and mechanical characteristics that cannot be met by traditional cellulose-derived materials, such as high aspect ratio, low density, high stiffness, high tensile strength and very low coefficients of thermal expansion. This paper is focused on the formation and characterization of CNC films and the subsequent traceable metrology of CNC film thickness by atomic force microscopy (AFM). The AFM is calibrated by a series of certified reference materials, and thus the measured values can be traceable to the laser wavelength reference (meter definition). Results show that CNC films with negative charges on surface can be formed via physisorption to an amine-terminated thiol layer on gold through spin coating. The CNC film thickness can be controlled by CNC solution concentration. A thorough understanding of CNC metrology is the foundation for further study of CNC chemical and mechanical characteristics and applications.