Depletion Effects and Stabilization of Pickering Emulsions Prepared from a Dual Nanocellulose System

Abstract

Nonadsorbing cellulose nanofibrils (CNF) are shown to induce stabilization of dilute oil-in-water Pickering emulsions formed by interfacial adsorption of highly charged TEMPO-oxidized CNF (TOCNF). The correlative interactions that occur upon sequential addition of the two types of nanofibrils (TOCNF and CNF) afford control of the properties of the obtained emulsions. For instance, the emulsions undergo (1) creaming of nonflocculated droplets at low CNF concentrations, (2) destabilization by depletion flocculation at intermediate concentrations of the nonadsorbing CNF, and (3) stabilization by formation of a fibrillar network and gelation above a critical CNF concentration (∼0.15 wt %). The observed phenomena are reproduced in TOCNFstabilized emulsions of varying droplet sizes (3.6, 6.9, and 11 μm). The interactions induced by the presence of CNF in TOCNF-based Pickering emulsions allow tailoring emulsion stability, most useful in fully green, all-cellulose foodstuff, cosmetic, and pharmaceutical formulations.

Formulation of Silk Fibroin Nanobrush-Stabilized Biocompatible Pickering Emulsions

“…In general, the mean droplet diameter (Figure 7b, except incomplete emulsions) showed a decreasing tendency with the increase of SNB concentration at day 1, and it became larger than that of day 1 after storage for 4 days, which was in agreement with previous studies. 28 Certainly, unstable emulsions presented the largest range of droplet diameter from 3.87 ± 1.07 to 9.87 ± 2.99 μm, and after storage for 4 days, even 13.57 ± 6.05 μm of diameter could be measured and apparent coalescence occurred (0.05 wt % SNB-stabilized emulsion), which further proved the instability of unstable emulsions. In terms of stable emulsions, from the images, it could be seen that the emulsion droplets with a mean diameter of around 2.5 μm were well separated and no apparent coalescence occurred, indicating that the appropriate SNB networks were formed in the oil-water interfaces and adequately stabilized the emulsions.…”

“…In general, the mean droplet diameter (Figure b, except incomplete emulsions) showed a decreasing tendency with the increase of SNB concentration at day 1, and it became larger than that of day 1 after storage for 4 days, which was in agreement with previous studies . Certainly, unstable emulsions presented the largest range of droplet diameter from 3.87 ± 1.07 to 9.87 ± 2.99 μm, and after storage for 4 days, even 13.57 ± 6.05 μm of diameter could be measured and apparent coalescence occurred (0.05 wt % SNB-stabilized emulsion), which further proved the instability of unstable emulsions.…”

Durable Nanocellulose-Stabilized Emulsions of Dithizone/Chloroform in Water for Hg2+ Detection: A Novel Approach for a Classical Problem

“…52 Most applications of nanocellulose as Pickering stabilizer involve alkanes, vegetable oils, and several sorts of long-chain aliphatic compounds as the organic phase. 27,31,43 However, in our case, chloroform has a dipole moment of 1.15 D and it is a fair hydrogen bond donor. 53 Although the aforementioned simulation of a chloroform-solvated oxidized cellobiose molecule returned a positive value for free energy, dipole− dipole interactions were the highest contributors to energy minimization.…”

“…Our proposal involves nanocellulose to stabilize a resembling system, although with less CHCl 3 and much less acid. Negatively charged cellulose nanofibers (CNFs) can simultaneously fulfill the roles of rheology modifier and Pickering stabilizer, which are generally closely related. , …”

Evaluating the Stability of Cellulose Nanofiber Pickering Emulsions Using MRI and Relaxometry

“…Cellulose nanofibers (CNFs) are promising emulsifiers for Pickering emulsions offering amphiphilic character, biocompatibility, and sustainability. − Several works demonstrated that surface-carboxylated CNFs by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) exhibited higher stability than unmodified CNFs owing to the negative surface charge. − Fujisawa et al reported that the cellulose origin should not significantly impact the formation of Pickering emulsions. Inspired by their research, we previously studied TEMPO-oxidized CNFs isolated from agricultural waste hop stems (HS) as an emulsifier for oil-in-water Pickering emulsions using dodecane or olive oil as the oil .…”