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![Pickering emulsion prepared with chitosan-modified silica nanoparticles. Reproduced from Ref. [57] with permission of American Chemical Society, Ó 2016.](publication/339287812/figure/fig4/AS:873036903358464@1585159626377/Pickering-emulsion-prepared-with-chitosan-modified-silica-nanoparticles-Reproduced-from.png)
Pickering emulsion prepared with chitosan-modified silica nanoparticles. Reproduced from Ref. [57] with permission of American Chemical Society, Ó 2016.
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In recent years, Pickering emulsions and their applications have attracted a great deal of attention due to their special features, which include easy preparation and enhanced stability. In contrast to classical emulsions, in Pickering emulsions, solid microparticles or nanoparticles that localize at the interface between liquids are used as stabil...
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... such emulsions are stable for up to 1.5 years. Stimulated by the emulsion stability improvement that was obtained using modified silica nanoparticles, other researchers investigated other modifications. Alison et al. [57] found that emulsions can also be stabilized by modifying silica nanoparticles using non-covalently bound chitosan oligomers (Fig. 6). Thanks to their interfacial adsorption, these particles make it possible to produce O/W emulsions with small droplets sizes (i.e., a few micrometers) by means of high-pressure homogenization. Otero et al. [63] studied how two adjacent water drops (one enriched in ethanol and the other pure water) could be stabilized in a bath of ...
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... Pickering emulsions stabilized by nanoparticles can reduce aggregations and improve the wettability of the stabilizing particles on the fluid interface [112]. There has been various research that functionalizes bio-nanoparticles including nanocellulose [113,114], nanostarch [70], and nanolignin [115], to be used as Pickering emulsifier, to develop nanocomposite emulsion system serving for consumable good applications. ...
Fabrication and operation on increasingly smaller dimensions have been highly integrated with the development of smart and functional materials, which are key to many technological innovations to meet economic and societal needs. Along with researchers worldwide, the Waterloo Institute for Nanotechnology (WIN) has long realized the synergetic interplays between nanotechnology and functional materials and designated ‘Smart & Functional Materials’ as one of its four major research themes. Thus far, WIN researchers have utilized the properties of smart polymers, nanoparticles, and nanocomposites to develop active materials, membranes, films, adhesives, coatings, and devices with novel and improved properties and capabilities. In this review article, we aim to highlight some of the recent developments on the subject, including our own research and key research literature, in the context of the UN Sustainability development goals.
... Pickering emulsions were first described in the early 20th century as particle-stabilized emulsions (Pickering 1907), and their study has considerably increased in the past two decades due to their potential for higher stability compared to surfactant-stabilized emulsions (Aveyard 2012). This characteristic is driven by the adsorption of solid particles to the liquid-liquid interface, creating a physical barrier that prevents droplet coalescence (Gonzalez Ortiz et al. 2020). By accumulating at the interface, the particles lower the interfacial tension between the dispersed and the dispersing phases, allowing the formation of long-stable Pickering emulsions (Levine et al. 1989). ...
In recent years, there has been growing interest in replacing petroleum-based water-in-oil (W/O) emulsifiers with sustainable and less toxic natural materials. Pickering emulsifiers are considered well-suited candidates due to their high interfacial activity and the ability to form emulsions with long-term stability. However, only sporadic examples of natural materials have been considered as inverse Pickering emulsifiers. This study describes the synthesis of a series of hydrophobic cellulose nanospheres by bulk modification with acyl groups of different chain lengths followed by nanoprecipitation, and their application as inverse emulsifiers. Modification with acyl groups of longer chain length (C16, C18) afforded lower degrees of substitution, but resulted in greater thermal stability than groups with shorter acyl chains (C12, C14). Formation of nanospheres with low aspect ratios and narrow size distributions required low initial cellulose concentrations (< 1% w/v), high volumetric ratios of antisolvent to solvent (> 10:1), and slow addition rates (< 20 mL/h). The modified cellulose nanospheres were able to reduce the interfacial tension between water and hexane from 45.8 mN/m to 31.1 mN/m, with an effect that increased with the number of carbons in the added acyl chains. The stearate-modified nanospheres exhibited superhydrophobic behavior, showing a contact angle of 156° ± 4° with water, and demonstrated emulsification performance comparable to the commonly used molecular surfactant sorbitan stearate. Our findings suggest that hydrophobically modified cellulose nanospheres have the potential to be a bio-derived alternative to traditional molecular W/O emulsifiers.
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... However, as reported by Yang et al. [99], wettability, particle size, and surface charge of the particles play an important role during the formation of Pickering emulsions, as the particles can adsorb and anchor at the interface to prevent droplet aggregation, creating steric hindrance [5]. Surface wettability of the particle determines the adsorption location of the particle at the interface and the resulting emulsion type, which can be characterized by a triphasic contact angle [100]. For hydrophilic particles with θ < 90°, they tend to reside in the aqueous phase and form Pickeringtype O/W emulsions. ...
This article discusses alternatives for modifying native starch through pre-treatments, with a focus on environmentally friendly methods, in order to assess how the type of modification affects the stability of Pickering emulsions. The affinity of native starch granules for aqueous and oily phases is impaired due to low steric repulsion, causing droplets to tend to aggregate. Therefore, it is essential to study the mechanisms governing the interface of emulsions. Waxy starches are the most commonly used for Pickering emulsion stabilization due to their high amylopectin content and, consequently, high crystallinity. Most of the modified starches presented in the literature in the last 5 years for Pickering emulsion stabilization involve chemical treatment with organic acids, such as octenyl succinic anhydride (OSA), which may, however, leave toxic and harmful acidic residues that are harmful to health. In this context, the article aims to broaden horizons by highlighting emerging physical techniques (thermal and non-thermal) applied in a simple and combined manner for starch modification. The use of modified starch aims to facilitate interactions between the aqueous and oily phases, thereby improving stability through enhanced interfacial and steric interactions. From future perspectives, enzymatic modification routes of native starch deserve special attention, as they are selective in attacking the amorphous zones of starch, while also respecting green chemistry.
... In order to restructure the electronic, diagnostic, and therapeutic applications of the nanoparticles, there is a mandate to manipulate the physicochemical properties [89,90]. Scanning electron microscopy can detect the basic morphological characteristics of the nanostructures, although transmission electron microscopy can give more precision [91]. ...
The current review aims to uphold all the attributes of protein-based nanostructures and their applications in therapeutics. Nanostructures have successfully revolutionized the era of novel drug delivery systems. Owing to the paramount advantages of nanoscale preparations, they have gained importance exponentially in recent years. Among the varied range of nanostructures, protein-based nanostructures have acquired a predominant orientation. Being a natural biomolecule, proteins have zero levels of toxicity, biodegradability, and biocompatibility. The present scenario states that the fourth generation of nanomedicines is being formulated which implements biomolecule nano-vectors that can exhibit the virtues of target specificity, multifunctionality, and stimuli-responsiveness. By virtue of possessing these attributes, apart from being able to partake in complex supramolecular assemblage, proteins have proven to be the best approach in the development of nanoscale structures. The review studies the supremacy of various protein-based nanoparticles over other nanostructures, their mode of preparation, efficacious delivery of a plethora of drugs, and their implementation in the field of nanomedicines along with various characterization techniques. As our insightfulness of protein-based nanoparticles expands, they grip boundless potential for revolutionizing drug delivery and renovating the treatment scenario for a widespread range of disorders.
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... These findings demonstrate that Fe3O4@OA particles play an active role in the formation of the raspberry-like or multi-hollow-like morphology of the composite microparticles produced. Hydrophobic nanoparticles and microparticles are capable of stabilizing water/oil emulsions during polymerization [62][63][64][65]. It is probable that, thanks to this feature, the hydrophobic nanoparticles of Fe3O4@OA can easily disperse in the monomer phase and participate in the formation of 'giga' pores in the polymer composite microbeads provided as a consequence of polymerization. ...
... These findings demonstrate that Fe 3 O 4 @OA particles play an active role in the formation of the raspberry-like or multi-hollow-like morphology of the composite microparticles produced. Hydrophobic nanoparticles and microparticles are capable of stabilizing water/oil emulsions during polymerization [62][63][64][65]. It is probable that, thanks to this feature, the hydrophobic nanoparticles of Fe 3 O 4 @OA can easily disperse in the monomer phase and participate in the formation of 'giga' pores in the polymer composite microbeads provided as a consequence of polymerization. ...
... The experiments also showed that 3e with higher palladium (1.07 mmol/g) and magnetite loadings (0.068 wt.% Fe determined by ICP) turned out to be slightly more active than 3d (0.81 mmol Pd(II)/g; 0.048 wt.% Fe from ICP analysis). Furthermore, it was concluded that the catalytic activities of 3d and 3e were considerably higher compared to the activity of the palladium catalyst based on gel-type polymer particles that were prepared without the addition of magnetite nanoparticles [65]. The presence of magnetite nanoparticles embedded within a gel-type polymer matrix can improve the dispersion of Pd(0) species on the surface and inside of a polymeric support, making them more active in the Suzuki reaction. ...
The modified suspension polymerization technique has been used for the preparation of composite microparticles from the mixture of glycidyl methacrylate (GMA), styrene (S), and divinylbenzene (DVB) in the presence of hydrophobized Fe3O4 nanoparticles. The obtained polymer microspheres were characterized using different instrumental and physicochemical techniques, modified with a zero-order PAMAM dendrimer, and impregnated with palladium(II) acetate solutions to immobilize palladium(II) ions. The resulting materials were preliminarily examined as catalysts in the Suzuki reaction between 4-bromotoluene and phenylboronic acid. It was found that the addition of magnetite particles to the composition of monomers provided polymer microparticles with embedded magnetic nanoparticles. The composite microparticles obtained showed a complex, multi-hollow, or raspberry-like morphology. After their modification, they could serve as recyclable catalysts for reactions that include both 4-bromotoluene and several other aryl bromides.
... The relative wettability of water concerning the solid particles is characterized by the three-phase contact angle, θ (Niroula et al., 2021). Depending on the relative wettability of water to the solid particles, as illustrated in Fig. 2D: when θ o-w < 90 • , measured through the aqueous phase, the solid particles lean towards hydrophilicity, resulting in O/W emulsions; for θ o-w > 90 • , the particles exhibit hydrophobicity, leading to W/O emulsions (Gonzalez Ortiz et al., 2020). The emulsion stability is intrinsically linked to the free energy required for the desorption of solid particles from the oil-water interface, as expressed in Eq. (1) (Binks, 2002;Binks and Lumsdon, 2000a). ...
... Researchers have also carried out multifaceted property modulation for various materials to meet different needs. Notably, unlike conventional surfactant-stabilized emulsions, the nanoparticles of Pickering emulsions can exhibit a wide variety of morphologies, such as solid particles, nanofibrils, hollow nanoparticles, nanotubes, and nanogels (Gonzalez Ortiz et al., 2020;Wang et al., 2019a;Wang et al., 2018;Wang et al., 2019b;Yao et al., 2020;Zhang et al., 2019) (Fig. 4B). Therefore, targeted wettability and surface morphology design are critical for constructing stable Pickering emulsion biocatalytic systems and improving their reaction efficiency. ...
... This phenomenon is most pronounced when the solid particles exhibit a preferential wettability towards the oil phase, leading to the formation of a densely packed particle layer around the droplet. Consequently, the energy barrier to oil droplet coalescence becomes equivalent to the energy required to displace these adsorbed particles [17]. Beyond this, electrostatic repulsion among charged particles further contributes to the emulsion's stability by preventing droplet fusion. ...
The presence of high permeability zones causes the injected fluid/gas to bypass the low permeability pores, initiating an early breakthrough. One of the most influential and promising methods to control fluid bypass is fluid diversion using an emulsion/chemical agent placed at the highly permeable zone, which eventually diverts the injected fluids to a less permeable region. Chitin Nanocrystal (ChiNCs), a naturally abundant nanomaterial with high oil-water interfacial adsorption, has attracted significant interest as an emulsion stabilizer in various applications. Unlike traditional surfactants, ChiNCs offer a sustainable alternative by stabilizing the emulsion, providing long-term stability and enhanced viscoelasticity. This study presents a novel, eco-friendly solution by exploring ChiNCs as pickering emulsions stabilizers for conformance control in porous media. The ChiNCs were prepared through acid hydrolysis of chitin powder derived from crab shells. ChiNCs and their emulsions were analysed using Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), Zeta (ζ)-Potential, Cross-Polarized Microscopy (CPM), and rheometer. The presence of ChiNCs in the emulsion resulted in shear-thinning behaviour, making it suitable for conformance control. Core-flood experiment results confirmed the effectiveness of ChiNCs-stabilized emulsions for permeability reduction. Pressure drops and permeability reductions increased with larger emulsion slug sizes, indicating successful pore plugging and improved fluid diversion. The highest-permeability reduction with 85.6% were obtained with 0.7 pore volume (PV) of emulsion injection for a short time. In contrast, injecting 0.5 PV of the emulsion led to a significant and sustained permeability reduction of 80.8%. To the best of the authors' knowledge, this is the first application of chitin nanocrystals in fluid diversion and conformance control. The ζ-potential over +20 mV within the pH range 3–6 was sufficient to achieve the highest colloidal stability via electrostatic effect and good ChiNCs suspension transparency. The microstructure observed under the CPM correlates with the rheological behavior, showing that the ChiNCs provide a significant steric barrier to coalescence, thus enhancing the emulsion's resistance to flow and deformation.
... Pickering emulsions have been recently developed as substitutes to conventional emulsions stabilized by surfactants for food applications (Sarkar & Dickinson, 2020). They are advantageous because they can be safe, biodegradable, stable and economic, making them very attractive for use in packaging applications (Gonzalez Ortiz et al., 2020). Incorporating multifunctional Pickering emulsions, usually oil-in-water (O/W) emulsions, into the polymer matrix to make different bio-based packaging films with enhanced physicochemical features has attracted attention (Niro et al., 2021). ...
... In general, amorphous silica used in Pickering emulsions are nonporous silica nanoparticles (SNPs), which are highly hydrophilic. However, the SNPs hydrophobicity and, therefore, their affinity at the oil-water interface may be improved by modification of the silica surface by chemical reaction or physical adsorption of several compounds (Arriagada et al., 2020), obtaining particles that are preferentially wetted by oil and, therefore, suitable to stabilize the inner interface (W 1 : O) of DEs, or preferentially wetted by water, and suitable to stabilize the outer interface (O:W 2 ) (González Ortiz et al., 2020;Guan & Ngai, 2021;Zhang et al., 2023). In this context, colloidal silica covalently linked with hydrophobic groups (such as propyl, methyl or octyl groups) instead of unmodified silica has been reported to produce emulsions with smaller droplets, due to an increase in the SNPs hydrophobicity (Björkegren et al., 2017). ...
... Both the droplet size and emulsion stability have been reported to be highly influenced by the particle concentration. A higher concentration of SNPs allows the stabilization of a greater interfacial area and the formation of a packed monolayer of particles at the droplets surface (González Ortiz et al., 2020). However, the increase of the SNPs concentration up to 6 % (w/w) did not significantly decrease the water droplet size (Fig. 1C and 1D), and therefore 4 % (w/w) of SNPs was selected to stabilize the W 1 /O emulsions with ratio W 1 :O 20:80 (w/w). ...
... The response surface graphics ( Fig. 2A and 2B) showed that the higher the homogenization time and homogenization speed, the higher the S 10 and the lower the EE of CA. This behavior was expected since an increase in the intensity or duration of the shear forces applied during homogenization reduces the oil droplet size (González Ortiz et al., 2020), but when the oil droplets become smaller than the inner water droplets, these are released to W 2 together with the encapsulated CA, leading to a decrease in EE of CA. The desirability function (Fig. 2C), used for multiple response optimization, reached the highest value at 6097 rpm (adjusted to 6000 rpm for practical reasons) and 3.41 min. ...
... The hydrophobic silica particles were dispersed in the canola oil before emulsification. The hydrophobic nature of the has led to the formation of water-in-oil Pickering emulsions.34 The emulsions were prepared at water/oil phase ratios (vol%) of 10:90, 20:80, 30:70, 40:60, and 50:50, respectively, with silica contents of 0.5 and 1 wt%. ...
The soil‐borne virus known as tomato brown rugose fruit virus (ToBRFV) has a low rate of around 3% soil‐mediated infection when the soil has root debris from a previous 30–50 day development cycle of tomato plants infected with ToBRFV. This study presents anti‐viral coating formulations based on Pickering emulsion. The coating formulation is based on water‐in‐canola oil emulsions stabilized using commercial hydrophobic silica, with water‐soluble polymer (sodium polyacrylic acid). The structure of the emulsions and their stability were characterized by confocal microscopy, centrifugal analysis using a LUMiSizer®, used to confirm the emulsion stability. We tested a few different silica concentration‐based formulations, which were prepared with or without the addition of various virus disinfectants. We found that under conditions of 100% soil‐mediated ToBRFV infection of uncoated positive control plants, root‐coating with formulations based on silica Pickering emulsion were prepared with the disinfectant chlorinated‐trisodium phosphate (TSP‐Cl) showed low percentages of soil‐mediated ToBRFV infection. These formulations had no adverse effect on plant growth parameters when compared to negative control plants grown under non ToBRFV inoculation conditions.
