The preparation and properties of marine diesel oil-in-water (o/w) emulsion stabilized by bifunctionalized cellulose nanocrystals (But-CNCs) were investigated. Bifunctional But-CNCs containing both carboxylic and n-butylamino groups were obtained using partial, sequential periodate-chlorite oxidation and reductive amination, followed by a homogenization treatment to liberate individualized nanocrystals with amphiphilic characteristics. The fabricated But-CNC suspensions were optically transparent, and the nanocrystals that were isolated were rod-like, with lengths ranging between 35 and 120 nm and with lateral dimensions varying from 2 to 4 nm. Bifunctionalized CNCs at low concentrations (up to 0.45 wt%) were investigated as possible surface-active stabilizers in o/w emulsions. In particular, their ability to enhance the emulsification of marine diesel oil in an aqueous environment was addressed in order to evaluate their potential to be used as "green" oil spill response agents. But-CNCs at 0.1 wt% concentration in dispersion reduced the oil particle size from 50 gm to 9-16 gm, and the stability against coalescence was improved in emulsions where bifunctionalized CNCs were used compared to plain o/w emulsion. In addition, the influence of But-CNC dosage and emulsion salinity (0-5% NaCl by weight) was investigated. The background salt concentration only had a minor effect on droplet size, and the stabilization effect was still apparent, with high electrolyte concentration. These results demonstrate the potential of bifunctionalized cellulose (with surface-active groups attached) to act as a nanoparticle emulsifier in oil-water emulsions, thus enabling its utilization in oil-destruction activities. (C) 2015 Elsevier B.V. All rights reserved.