Role of Surfactant in Other Organs
Jacques R. Bourbon in Pulmonary Surfactant: Biochemical, Functional, Regulatory, and Clinical Concepts, 2019
Adsorption is a particularly common process, especially of the weak physical type where van der Waals’ forces may hold layers several hundred molecules in thickness in loose association with the surface. Much stronger adsorption can be effected when one of the chemical groups (moieties) in the molecule forms a chemical bond with the surface known as chemisorption.1,2 This is still not obvious to an observer unless the two ends of the adsorbed molecule are of widely differing character, especially in their affinity for water, as one finds between the polar and nonpolar moieties of surfactant molecules. The attachment of a surfactant molecule by, for instance, electrostatic attraction between the polar moiety and a fixed charge on the surface orientates the molecule with its nonpolar group facing outward. This effects a total “change of personality” in which a highly wettable surface such as glass or cotton can be rendered hydrophobic and water repellent. Thus, droplets of water which would have spread spontaneously on clean glass now “bead up” to display a contact angle which provides a convenient index of the change in surface energy upon adsorption.3
Polymer–Silver Nanocomposites: Preparation, Characterisation and Antibacterial Mechanism
Huiliang Cao in Silver Nanoparticles for Antibacterial Devices, 2017
After the preparation of Ag NPs, the nanoparticles can be modified via ligand exchange reactions wherein the capping molecules of the obtained nanoparticle surface are instead of a polymer, or via chemical alteration of the capping molecule. Sodium citrate and various cationic surfactants, such as cetyltrimethylammonium bromide (Jana et al. 2001), benzyldimethyl hexadecylammonium chloride (Nikoobakht and El-Sayed 2003; Park et al. 2010) and cetylpyridinium chloride monohydrate (Bronstein et al. 2000; Setua et al. 2010), are commonly used as capping molecules. However, these capping molecules are labile with weakly chemisorption to the nanoparticle surface. As a result, ligand exchange reactions become a general strategy for surface modification of nanoparticles with polymer grafts (Figure 5.2). The capping molecules are substituted through covalent binding of the graft to the nanoparticle surface or physisorption of the polymer graft. The effectiveness of this displacement depends on the affinity of the polymer graft with the nanoparticle surface. Therefore, postsynthetic modification of Ag NPs is a typical method for polymer grafts that display strong binding affinity to the nanoparticle surface. For example, thiol-functionalised polymer grafts are widely used in the surface modification of plasmonic nanoparticles, because the high affinity of the thiol to Ag makes the terminus of the polymer easily graft to the Ag NPs surface (Love et al. 2006; Rucareanu et al. 2008).
Chemical, Biochemical, and Medicinal Properties of the Diphosphonates
Richard L. Hilderbrand in The Role of Phosphonates in Living Systems, 2018
The chemisorption of the diphosphonates to calcium phosphate nuclei during their formation leads to a physical chemical inhibition of crystal growth of apatite. This effect produces an apparent increase in solubility of hydroxyapatite and can block apatite deposition as in calculus formation (see Section III.C). The possible role of chemisorption as it relates to biological mineralization of mammalian hard tissue is discussed below.
Surgical applications of intracorporal tissue adhesive agents: current evidence and future development
Published in Expert Review of Medical Devices, 2020
Nicholas Gillman, David Lloyd, Randy Bindra, Rui Ruan, Minghao Zheng
In the context of adhesion, molecular bonding is divided into chemisorption and physisorption. Chemisorption refers to interactions between adhesive compounds and a biological surface that results in primary bond formation such as covalent and ionic bonds. Common interactions including amide [16,17] and Schiff base formation [18]. Physisorption refers to interactions between molecules and compounds resulting in secondary bond formation, with common interactions including π-π stacking, hydrogen bonding, dipole–dipole interactions and Van der Waals instantaneous dipoles. These forces create weak interactions at the tissue surface which can reinforce adhesive and cohesive strength [19]. In terms of cohesive strength, the density of crosslinking plays a predominant role [20]. Common interactions include amide linkages and covalent imine bond formation between carbonyl and amide functional groups (Schiff base formation) [18,21].
Optimum isotherm by linear and nonlinear regression methods for lead (II) ions adsorption from aqueous solutions using synthesized coconut shell–activated carbon (SCSAC)
Published in Toxin Reviews, 2021
Onyedikachi Godwin Okpara, Osareme Mercy Ogbeide, Ozoemena Christain Ike, Kosoluchi Chisom Menechukwu, Eric Chidozie Ejike
The Temkin isotherm model whose adsorption is characterized by a uniform distribution of the binding energies, up to a notable maximum binding energy was verified. The model describes a chemisorption process (Wang et al. 2015, Lau et al. 2016), and assumes that the heat of adsorption of all the molecules in the layer reduces linearly rather than logarithmically (as implied in the Freundlich equation) with surface coverage due to adsorbent–adsorbate interactions (Piccin et al. 2011). The calculated Temkin model parameters are presented in Table 3, where it R2 value (0.7893) reflected unacceptable linearity less than other linear isotherm equations, which suggests that the adsorption of Pb (II) ions is obviously does not follow the postulates of the Temkin model. Nevertheless, the positive value of the constant B (9.197)>0 corresponds to a positive value of the variation of adsorption energy parameter bT (264.87 Jmol−1) suggesting that the adsorption of Pb (II) onto the SCSAC is exothermic in nature. That is, bT = (-ΔH). As earlier stated, the correlation coefficient being 0.789, implied that Temkin isotherm did not well describe the experimental data. Meaning that the Pb (II) ions adsorption using SCSAC adsorbent is not really a chemical adsorption process but a physical adsorption process due to the low R2 value. To further determine the goodness of fit of this isotherm model, the SSE, RMSE, X2, ARE and MPSD were verified. Their values were 3.425, 1.309, 2.517, 42.520 and 68.582, respectively, which were by far higher than the error values obtained from other linear and nonlinear isotherm models as shown clearly in Table 4 and Figure 2(a,c). Thus, the linearized Temkin model does not describe the equilibrium data adequately, because of the low coefficient of determination (R2) and higher values of SSE, RMSE, X2, ARE and MPSD.
Arabian Primrose leaf extract mediated synthesis of silver nanoparticles: their industrial and biomedical applications
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2020
Shruti Nindawat, Veena Agrawal
From the results obtained, it is clear that the rate of Ah-AgNPs catalysed reaction is very fast. This might be due to the smaller size, spherical shape and crystal structure of nanoparticles which are chemically active and prone to dissolve easily producing catalytically active sites. This results in the availability of large number of binding sites for the chemisorption of reactants thereby enhancing the reaction rate [40].
Related Knowledge Centers
- Adsorption
- Corrosion
- Heterogeneous Catalysis
- Substrate
- Thiol
- Gold
- Lennard-Jones Potential
- Activation Energy
- Effective Medium Approximations
- Reactions On Surfaces