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Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Xuan Yang, Miaoxin Yang, Pang Bo, Madeline Vara, Younan Xia
van der Waals forces are weak interactions, which exist widely between atoms or molecules. Using van der Waals forces, different drug molecules can be readily adsorbed onto the capping ligands on Au nanoparticles. For example, Murphy and coworkers explored the use of CTAB-stabilized Au nanorods as a platform for the delivery of 1-naphthol, which is a model hydrophobic drug [595]. The bilayer of CTAB provides a ~3 nm thick hydrophobic layer that can be used to sequester 1-naphthol from an aqueous solution. The adsorption isotherm of 1-naphthol onto the CTAB bilayer can be fitted to a Langmuir model. The maximum number of adsorbed 1-naphthol molecules was found to be 14.6 × 103 molecules per Au nanorod with an equilibrium binding constant of 1.97 × 104 M−1 at room temperature. Doxorubicin (Dox) has also been loaded onto the surface of Au nanoparticles through the van der Waals forces between Dox and DNA strands attached to Au surface [564]. The loading efficiency of Dox could reach 615 ± 34 Dox molecules per Au nanoparticle of about 12.7 nm in size.
Introduction to Nanostructured Multifunctional Materials
Published in Esteban A. Franceschini, Nanostructured Multifunctional Materials Synthesis, Characterization, Applications and Computational Simulation, 2021
As one can see, during the manufacture and processing of nanostructures, the main barrier to overcome is the enormous total free energy of the surface to create the desired nanostructures, avoiding unwanted agglomerations and restructuring. As the dimension of the nanostructured material is reduced, the Van der Waals force between nanomaterials becomes increasingly important.
Filtration: The Underutilized IAQ Asset
Published in H.E. Burroughs, Shirley J. Hansen, Managing Indoor Air Quality, 2020
H.E. Burroughs, Shirley J. Hansen
Similarly, atmospheric conditions like temperature, relative humidity (RH) and barometric pressure affect the performance of the sorption bed. Higher temperatures tend to make the molecules more active which tend to overpower the van der Waals forces. For example, carbon is normally reactivated with heat. High humidity can blind the pore structure, and void internal sorption sites by filling them with water molecules. These factors can have significant influence on the behavior of gaseous filters in the field. For example, a 10—°F shift or a 10-point RH swing can influence the sorption capacity isotherm of a carbon filter by as much as 25%.
Experimental study of the influences of water injections on CBM exploitation
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Xiangjun Chen, Liyang Li, Yuanping Cheng, Lingling Qi
Coal is a very porous material with a large specific surface area. It is a natural adsorbent and able to adsorb many substances. Intermolecular forces between molecules and adsorbates are fundamental forces that lead to the adsorption of some materials. These forces include hydrogen bonding and Van der Waals’ forces. Van der Waals’ forces are formed by a combination of dispersion forces, electrostatic forces, and induction forces. Different materials have different inner structures and molecular sizes, which lead to different intermolecular forces between molecules and adsorbents. Therefore, once a kind of molecule enters into the coal that has stronger intermolecular forces with coal than those that exist between coal and methane, methane molecules will be replaced by this molecule in a phenomenon known as replacement desorption.
Renewable biofuel production from biomass: a review for biomass pelletization, characterization, and thermal conversion techniques
Published in International Journal of Green Energy, 2018
Manar Younis, Sabla Y. Alnouri, Belal J. Abu Tarboush, Mohammad N. Ahmad
In the absence of a solid bridge, particles may bond with the help of attractive forces between solid particles. Solid particles stick to each other through short-range forces (Kaliyan and Morey, 2008) such as molecular valance forces (i.e., free chemical bonds), hydrogen bridges, van der Waals’ forces, electrostatic and magnetic forces. Molecular valance forces only take effect when the inter-molecular distance is around 10 Å. Unlike valance forces, van der Waals’ forces are considered to be the most effective forces that contribute to all attractive and adhesive effects of molecules at a distance less than 0.1 µm. As a result of milling or friction within the particles, excess charges may be generated, so that electrostatic forces become very helpful in the binding process. The presence of magnetic forces may also contribute to further particle bonding. When particle size, or inter-particle distance increases, the efficiency of short-range forces rapidly decreases (Pietsch 2001; Rumpf 1962).
The rheological and thickening properties of cationic xanthan gum
Published in Journal of Dispersion Science and Technology, 2018
Lujiao Shi, Yi Wei, Nan Luo, Tianwei Tan, Hui Cao
The loss factor (tan δ = G″/G′) is an important parameter for representing the visco-elasticity of the solution. The influences of temperature on modulus (G′ and G″) and loss factor (tan δ) of XG and CXG are shown in Figure 8b–8d. With the increase of temperature, G′ and G″ decrease, but the elasticity of solutions is the dominating factor in the range of temperature (G′ > G″). Furthermore, the visco-elasticity of CXG solution is greater than that of XG solution (CXG2 > CXG1 > XG). From the beginning, the tan δ value of all samples appears similar level, while with the increase of temperature, the difference of tan δ value among the samples becomes manifest, depending on DS. The tan δ values of XG, CXG1, and CXG2 are respectively 0.343, 0.341, and 0.313 at 25°C, and 0.675, 0.558, and 0.476 at 90°C. Although all samples show an elasticity performance, the elastic degree of the CXG solution is higher than that of XG solution, confirming that a higher DS induces a higher degree of elasticity. Increasing the temperature accelerates the motion of the molecules and weakens the van der Waals forces and hydrogen bonds.[1] This causes a loss of intermolecular intertwining and connection. However, due to the presence of electrostatic interactions among CXG molecules, CXG can maintain the strength of a gel-like structure, and CXG solution shows a higher viscosity and superior elasticity at high temperature compared with XG solution. The temperature tolerance of CXG is moreover superior to that of XG.