Cellulose nanocrystal stabilized pickering nanoemulsions and their coalescence stability studied by fluorescence microscopy

Cellulose nanocrystals (CNCs) have been used as Pickering emulsifiers by forming rigid interfacial layer coated around oil droplets. Sulfated and desulfated CNCs were used to emulsify squalane oil to produce Pickering nanoemulsions. The formation of CNCs-Pickering nanoemulsions was investigated and their stability against mechanical stresses was studied using fluorescence microscopy with a lab-made image analysis program. The formation of Pickering nanoemulsions using CNC particles was tuned by screening their surface charges with cations. Sulfated and desulfated CNC nanoemulsions showed submicron droplet size of 619 and 555 nm, respectively. The mechanical stresses could induce droplet encounter leading to physical instability. The sulfated CNCs displayed superior stability than the desulfated CNCs in terms of droplet aggregation after treatment with mechanical stresses. Fluorescence microscopy image analysis revealed the physical instability of Pickering nanoemulsions at the microscopic level, which is a useful tool for studying the destabilization mechanisms.