Wetting and emulsification properties of cellulose nanocrystals modified with tannic acid and alkyl cellulose derivatives.

Hypothesis: Cellulose nanocrystals (CNCs) are sustainable rod-like nanoparticles that can be used to stabilize oil-in-water emulsions and can create hydrophilic coatings. Modifying the surface of CNCs can improve emulsion properties and allow for adjustable wettability.

Experiments: This study explores the improvement of Pickering emulsion properties for various oils and the adjustability of coated surfaces through the physical modification of CNCs, without chemical functionalization.

Thermo-rheological properties of xanthan solutions: from shear thinning to elasto-viscoplastic behavior.

The thermo-rheological behavior of xanthan solutions with concentrations spanning a wide range is investigated experimentally. After carefully identifying four distinct regimes of concentration we focused on highly concentrated xanthan solutions. By combining several rheological techniques, it is shown for the first time that such solutions belong to the broad class of elasto-viscoplastic materials by exhibiting both a yield stress and elasticity that manifests around the solid-fluid transition.

Modulation of surface properties of cellulose nanocrystals through adsorption of tannic acid and alkyl cellulose derivatives.

Cellulose nanocrystals (CNCs) are hydrophilic nanoparticles that cannot be dispersed in non-polar solvents or hydrophobic polymer matrices. Here, we demonstrate the tunable modification of CNC surfaces by physical adsorption of tannic acid (TA) and two alkyl cellulose derivatives (ACDs), methyl cellulose (MC) and ethyl cellulose (EC), while maintaining their sustainable nature. We compare the impact of ACD adsorption when mixed with CNCs to CNCs precoated with tannic acid (CNC@TA), varying ACD weight fractions in CNC suspensions.

Interactions between proteins and cellulose in a liquid crystalline media: Design of a droplet based experimental platform.

Model systems are needed to provide controlled environment for the understanding of complex phenomena. Interaction between polysaccharides and proteins in dense medium are involved in numerous complex systems such as biomass conversion or plant use for food processing or biobased materials. In this work, cellulose nanocrystals (CNCs) were used to study proteins in a dense and organized cellulosic environment.

Influence of Low-Molar-Mass Xyloglucans on the Rheological Behavior of Concentrated Cellulose Nanocrystal Suspensions.

Hydrogels were prepared at high solid contents (70-100 g/L) with cellulose nanocrystals (CNC) and very short xyloglucans (XGs). At 70 g/L, CNCs form cholesteric liquid crystals regularly spaced by a distance of 30 nm. This structure was preserved after adsorption of XG with a molar mass () of 20,000 g/mol (XG20) but was lost at 40,000 g/mol (XG40).

Edge-On (Cellulose II) and Face-On (Cellulose I) Adsorption of Cellulose Nanocrystals at the Oil-Water Interface: A Combined Entropic and Enthalpic Process.

Nanocelluloses can be used to stabilize oil-water surfaces, forming so-called Pickering emulsions. In this work, we compare the organization of native and mercerized cellulose nanocrystals (CNC-I and CNC-II) adsorbed on the surface of hexadecane droplets dispersed in water at different CNC concentrations. Both types of CNCs have an elongated particle morphology and form a layer strongly adsorbed at the interface.

Formulation of re-dispersible dry o/w emulsions using cellulose nanocrystals decorated with metal/metal oxide nanoparticles.

This study describes for the first time the preparation of re-dispersible surfactant-free dry eicosane oil emulsion using cellulose nanocrystals (CNCs) using the freeze-drying technique. Surface properties of CNCs constitute a critical point for the stability of o/w emulsions and thus can affect both the droplet size and dispersion properties of the emulsion. Therefore, surface modification of CNCs was performed to understand its effect on the size of the obtained re-dispersible dry o/w eicosane emulsion.

Impact of Physico-Chemical Properties of Cellulose Nanocrystal/Silver Nanoparticle Hybrid Suspensions on Their Biocidal and Toxicological Effects.

There is a demand for nanoparticles that are environmentally acceptable, but simultaneously efficient and low cost. We prepared silver nanoparticles (AgNPs) grafted on a native bio-based substrate (cellulose nanocrystals, CNCs) with high biocidal activity and no toxicological impact. AgNPs of 10 nm are nucleated on CNCs in aqueous suspension with content from 0.

Hydroxyl groups on cellulose nanocrystal surfaces form nucleation points for silver nanoparticles of varying shapes and sizes.

In this study, we investigate the interactions between the cellulose surface and Ag nanoparticles (AgNPs) for the purpose of manufacturing hybrid nanomaterials using bacterial cellulose nanocrystals (BCNs) as a model substrate. We focus on the role of the BCN surface chemistry on the AgNP nucleation obtained by chemical reduction of Ag ions. Homogeneous hybrid suspensions of BCN/AgNP are produced, regardless of whether the BCNs are quasi-neutral, negatively (TBCNs) or positively charged (ABCNs).

Tuning of Ag Nanoparticle Properties in Cellulose Nanocrystals/Ag Nanoparticle Hybrid Suspensions by HO Redox Post-Treatment: The Role of the HO/AgNP Ratio.

Hybrid nanoparticles involving 10-nm silver nanoparticles (AgNPs) nucleated on unmodified rod-like cellulose nanocrystals (CNCs) were prepared by chemical reduction. HO used as a post-treatment induced a size-shape transition following a redox mechanism, passing from 10-nm spherical AgNPs to 300-nm triangular or prismatic NPs (AgNPrisms), where CNCs are the only stabilizers for AgNPs and AgNPrisms. We investigated the role of the HO/AgNP mass ratio (α) on AgNPs.

Chitin Pickering Emulsion for Oil Inclusion in Composite Films.

A film containing a stable and well-dispersed hydrophobic phase in a surfactant-free bio-based hydrophilic matrix is proposed. In this study, an aqueous suspension of rod-like chitin nanocrystals (ChiNCs), mixed with paraffin oil, form an oil-in-water Pickering emulsion with a droplet diameter of 3 μm. These emulsions mixed with a 5 wt% starch solution formed homogeneous composite films by solvent casting.

Selective radical depolymerization of cellulose to glucose induced by high frequency ultrasound.

The depolymerization of cellulose to glucose is a challenging reaction and often constitutes a scientific obstacle in the synthesis of downstream bio-based products. Here, we show that cellulose can be selectively depolymerized to glucose by ultrasonic irradiation in water at a high frequency (525 kHz). The concept of this work is based on the generation of H˙ and ˙OH radicals, formed by homolytic dissociation of water inside the cavitation bubbles, which induce the cleavage of the glycosidic bonds.

Non thermal plasma in liquid media: Effect on inulin depolymerization and functionalization.

We report the complete conversion of inulin in gas/liquid media by a dielectric barrier discharge plasma at atmospheric pressure. Depending on the plasma treatment time (from 1 to 30 min) and the chemical nature of the gases (air, oxygen, nitrogen), it was possible to depolymerize inulin into fructo-oligosaccharides with a degree of polymerization under 5 or to achieve a total conversion of inulin into its two monomeric constituents, fructose and glucose in 20 min, without any degradation products. Combined results from liquid chromatography (HPLC), solid state Nuclear Magnetic Resonance (ssNMR) and mass spectroscopy revealed that the breakage of the β 1-4-bridged oxygen occurs by an acidic attack, following the oxidation of the polymer.

Dementia, End of Life, and Euthanasia: A Survey Among Dementia Specialists Organized by the Belgian Dementia Council.

Background: Palliative care and Advance Care Planning (ACP) are increasingly recommended for an optimal management of late-stage dementia. In Belgium, euthanasia has been decriminalized in 2002 for patients who are "mentally competent" (interpreted as non-demented). It has been suggested that advance directives for euthanasia (ADE) should be made possible for dementia patients.

Macroporous hybrid Pickering foams based on carbon nanotubes and cellulose nanocrystals.

The association of nanoparticles with complementary properties to produce hybrids is an underestimated way to develop multifunctional original architectures. This strategy is used to prepare simple, low-cost, and environmentally friendly method to fabricate ultra-low density alveolar foam reinforced with carbon nanotubes (CNTs). This paper investigates the ability of cellulose nanocrystals (CNCs) to produce highly stable oil-in-water Pickering emulsions and to efficiently disperse carbon nanotubes in water to form three-dimensional macroporous conductive foam.

Exploiting Complex Formation between Polysaccharides and Protein Microgels To Influence Particle Stabilization of W/W Emulsions.

Protein particles were complexed with polysaccharides, and the effect on their capacity to stabilize water-in-water (W/W) emulsions was investigated. Protein microgels were formed by heating aqueous solutions of whey protein isolate. The microgels were subsequently mixed with anionic or cationic polysaccharides: κ-carrageenan (κ-car) or chitosan, respectively.

Water-In-Water Emulsion Gels Stabilized by Cellulose Nanocrystals.

Particle-stabilized water-in-water emulsions were prepared by mixing dextran and poly(ethylene oxide) (PEO) in water and adding cellulose nanocrystals (CNC). The CNC formed a layer at the surface of the dispersed droplets formed by the PEO-rich phase. Excess CNC partitioned to the continuous dextran phase.

Design of Pickering Micro- and Nanoemulsions Based on the Structural Characteristics of Nanocelluloses.

The development of biobased materials with lower environmental impact has seen an increased interest these last years. In this area, nanocelluloses have shown a particular interest in research and industries. Cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) are both known to stabilize oil-water interfaces, forming the so-called Pickering emulsions which are surfactant-free, highly stable emulsions armored by a layer of solid particles.

Some modification of cellulose nanocrystals for functional Pickering emulsions.

Cellulose nanocrystals (CNCs) are negatively charged colloidal particles well known to form highly stable surfactant-free Pickering emulsions. These particles can vary in surface charge density depending on their preparation by acid hydrolysis or applying post-treatments. CNCs with three different surface charge densities were prepared corresponding to 0.

Microfluidic Encapsulation of Pickering Oil Microdroplets into Alginate Microgels for Lipophilic Compound Delivery.

Alginate microgels are widely used as delivery systems in food, cosmetics, and pharmaceutical industries for encapsulation and sustained release of hydrophilic compounds and cells. However, the encapsulation of lipophilic molecules inside these microgels remains a great challenge because of the complex oil-core matrix required. The present study describes an original two-step approach allowing the easy encapsulation of several oil microdroplets within alginate microgels.

Stabilization of Water-in-Water Emulsions by Nanorods.

Water-in-water (W/W) emulsions formed by mixing incompatible water-soluble polymers cannot be stabilized with molecular surfactants. However, they can be stabilized by particles through the so-called Pickering effect. Recently, it was shown that its stabilization can be achieved also with nanoplates.

Structural Description of the Interface of Pickering Emulsions Stabilized by Cellulose Nanocrystals.

The cotton cellulose nanocrystals (CNCs) used in this study are rod-like particles with dimensions in the nanoscale (195 nm long, 23 nm width and 6 nm thick) able to stabilize Pickering emulsions. The adsorption of CNCs at an oil-water interface has been investigated by small angle neutron scattering (SANS) with and without surface charge, and varying CNC concentration from 2 to 5 g/L. Average thicknesses of the interfacial CNC layer around the emulsion droplets of 7 and 18 nm were determined for charged and uncharged CNC, respectively, regardless of their concentration in suspension.

Kinetic aspects of the adsorption of xyloglucan onto cellulose nanocrystals.

In this work, the adsorption of a neutral flexible polysaccharide, xyloglucan (XG), onto thin cellulose nanocrystal (CNC) surfaces has been investigated to get more insight into the CNC-XG association. Gold-coated quartz crystals were spin-coated with one layer of CNC, and XG adsorption was monitored in situ using a quartz crystal microbalance with dissipation (QCM-D). The adsorption of XG under flow at different concentrations did not result in the same surface concentration, which evidenced a kinetically controlled process.