Nanoparticle wettability

Figure 13.11 The patterning of nanoparticle crystals by combination of photolithography and surface wettability.75 A concentrated nanoparticle solution slowly evaporated in the gaps between the patterned substrate and a glass substrate. When the structure was peeled off, patterned nanoparticle crystals on both surfaces were formed.

In addition to the size of the nanoparticles, the interfacial tension and, therefore, the wettability of a particle surface, also dictates the desorption energy [4]. The wettability is described by the contact angle 0 between the solid and the oil-water interface. The stability of oil-in-water (O/W) emulsions or water-in-oil (W/O) emulsions depends on this contact angle. In general, the less-wetting liquid becomes the dispersed phase. If 0 is lower than 90°, O/W emulsions are more stable at contact angles greater than 90°, W/O emulsions are favored (Fig. 2) [14]. 

The variation of the desorption energy with the contact angle is displayed in Fig. 3. Binks and Lumsdon investigated a toluene-water system with constant interfacial tension of 36mN/m by using silica nanoparticles of constant radius of lOnm and various wettabilities [4]. At a contact angle of 90°, a maximum in desorption... 

Ma and Dai [121] reported the synthesis of polystyrene latexes armored with silica nanoparticles (10-15nm in diameter, PA-ST silica sol, Nissan Chemicals) via solids-stabilized emulsion polymerization. They used VA-086, 2,2 -azobis [2-methyl-lV-(2-hydroxyethyl)propionamide], as nonionic initiator. Whereas we found that Pickering emulsion polymerization of styrene using Ludox TM-40 and a low flux of radicals generated from potassium persulfate did not result in an armored latex, the hydroxyethyl groups probably enhance the wettability of the surface of the latex particles to promote silica adhesion. This was confirmed by a... 

B.X. Wang, Y. Zhao, X.P. Zhao, The wettability, size effect and electrorheological activity of modified titanium oxide nanoparticles, Colloids Surf. A, 2007, 295, 27. 

Effect of Plasma Treatment Time The water surface contact angle measurement and thermal conductivity measurement showed that plasma treatment of diamond nanoparticles with 1 1 ratio of O2/CH4 gave rise to the best surface wettability and the highest thermal conductivity of the resulting nanofluids. Using plasma gas mixture with a fixed O2/CH4 ratio of 1 1, therefore, effects of plasma treatment time on thermal conductivities of the resulting... 

For the self-assembly driven by solvent evaporation, the narrow size distribution of building blocks is not the only requirement for achieving long-range order in the particles ensemble. Other conditions, such as solvent composition, temperature and evaporation kinetics are also very important. Fast drying procedure for less than 10s has been carried out in the suspensions of Ni nanoparticles (9 nm) in pentane deposited on amorphous carbon substrate. As a result, the two-dimensional densely packed monolayer of nanoparticles has been obtained. Deposition of the same particles of nickel from its suspension in mixed 80 % hexane with 20 % octane followed by slow evaporation (about 5 min) of liquid leads to 3D superlattice of Ni nanoparticles [344]. In addition, the wettability of the substrate by the suspension affects the superlattice morphology. If the nanoparticles suspension wets the sub-... 

These silica nanoparticles generate surface roughness on the polybenzoxazine nanocomposite film, possessing both micro- and nanoscale binary structures. In addition, its appropriate chemical structure allows for reversible wettability operation. The as-prepared superhydrophobic surface is not wettable by pure water. Mohammad et al. [13] reported that aqueous solutions of various surfactants were able to wet a superhydrophobic surface since these surfactants reduced the siuface tension of the solutions. Soeno and co-workers [14] also reported wetting of their superhydrophobic surfaces with a water/ethanol mixture. In this study, ethanol was chosen to reduce the surface tension of the solvent and shift the superhydrophobic polymer film into wettable film through a relatively milder condition. 

Figure 4. Reversible wettability transition of polybenzoxazine-silica hybrid films with 50 phr (circle) and 120 phr (triangle) silica nanoparticle contents.

The combination of changes in surface chemistry and surface roughness can enhance stimuli-responsive wettability. Here, we have presented a simple one-step method to prepare apolybenzoxazine-silica nanoparticle film, displaying reversible wettability via a solvent treatment. The difference in the water CAs of the same composite film, before and after solvent treatment was achieved to be 19° with silica content of 120 phr. Compared with a traditional superhydrophobic surface, the as-prepared film can be modified to show not only hydrophobicity but also a high adhesion force with water. Our results are considered to be significant in terms of their importance to academic research and industrial applications. 

Cellulose whiskers without surface modification display strong interactions and have been reported as difficult to disperse in water. Sulfate-functionalized tunicate whiskers were prepared by sulfuric acid hydrolysis of cellulose pulp derived from tunicates (StyelacldVa). These high aspect ratio nanoparticles formed colloidal suspensions in water (Figure 14.4). A stable suspension of tunicin whiskers was obtained in an organic solvent (Af,Af-dimethylformamide) without surfactant addition or chemical surface modification. Both the high value of the dielectric constant of DMF and the medium wettability of tunicin whiskers were supposed to control the stability of the suspension (Figure 14.5). 

Fenouillot et ol. [368] reviewed polymer blends with solid nanopartides. The authors briefly discussed oil/water emulsions with solid colloidal partides, considering their wettability and location. Next, polymer blends with nanopartides were discussed, starting with systems near the phase separation, and then within the immiscibility region. Some similarities and differences between the low- and high-viscosity emulsions were highlighted. The particular reason for preparing the review seems to be the authors search for factors that may affect nanoparticle localization at the thermodynamic equilibrium. Diverse polymer blends with pseudo-spherical... 

Lee MW, An S, Joshi B, Latthe SS, Yoon SS (2013) Highly efficient wettability control via three-dimensional (3D) suspension of titania nanoparticles in polystyrene nanofibers. ACS Appl Mater Interfaces 5 1232-1239... 

Dmg loading in micro- and nanoparticulate systems is generally carried out by one of two methods, i.e. during the preparation of particles (incorporation) or after their formation (incubation). The dmg delivery properties are also essentially dependent on the chemical and textural properties of the matrices, the porosity, wettability, erosion and the surface area. The matrix equally has an impact on the discharge profile for the bioavailability of the entrapped dmg. Nanoparticle-based delivery systems have the potential power to improve dmg stability, increase the duration of the therapeutic effect and permit enteral or parenteral administration, which may prevent or minimize dmg degradation and metabolism as well as cellular efflux [70, 71]. Protein nanoparticles can conveyance medications transversely across the blood-brain barrier that are not usually passed across after injection. A number of authors have demonstrated a considerable tendency for an accumulation of protein nanoparticles in certain tumours. The binding of a variety of cytotoxic dmgs, such as 5-fluorouracil,... 

Fig. 2 Top -view microscopy images of different substrates considered in this work, (top) Flat silicon and silica sphere arrays before chemical treatment, (middle) Similar substrates after PFOTS treatment, (bottom) Images of flat silicon and silica sphere arrays decorated by gold nanoparticles. The wettability results (insets) show that superhydrophobicity is achieved on hierarchical structures as depicted by a large contact angle for identical surface chemistry...

Monolayers of nanoparticles at liquid-fluid interfaces have attracted considerable attention over several decades [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]. Among others, the examinations focused on thin-layer preparation [10, 18, 19, 20, 21, 22, 23], emulsion stabilisation [15, 24] and particle characterisations [25, 26, 27]. The Stober silica (synthesised by controlled hydrolysis of tetraethylorthosilicate in ethanol in the presence of ammonia and water) [28] has many advantageous properties for model investigations. The nearly spherical particles show a narrow size distribution and are compact above a certain particle size (around 20 nm diameter) [29]. The particles, on the one hand, show partial wettability and, on the other hand, form a weakly cohesive two-dimensional dispersion at the water-air interface [10, 14]. All that makes them suitable to determine the total repulsive interparticle energies in a film balance by measuring the effective surface tension of the monoparticulate layer [30, 31, 32, 33, 34, 35, 36]. 

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