Papers by Keyword: Electrostatic Interaction

Abstract: One step polyacrylamide gel method was used to synthesize the ZnO/MgO adsorbents and the adsorption behavior with Congo red (CR) from wastewater was extensively investigated. Various advanced techniques were applied to confirm the ZnO/MgO adsorbents consist of Zn, C, Mg and O elements and do not contain any other impurity elements. With the increase of MgO content, the morphology of ZnO/MgO adsorbent changes from the agglomeration of large particles to evenly dispersed fine particles and then to icicle structure. Results demonstrated that the adsorption process of ZnO/MgO adsorbents was significantly affected by the change in initial dye solution pH, initial adsorbent dosage, contact time and reaction temperature. The optimum pH, adsorbent dosage, contact time and reaction temperature is 9.81, 2 g /L, 65 min and 293 K, respectively. The maximum adsorption capacity of ZnO/MgO (nZnO:nMgO = 8:2) adsorbents (295.138 mg/g) for the adsorption of CR dye was approximately double that of previous reports (125 mg/g). The adsorption equilibrium data are well fitted by the Freundlich and Langmuir isotherm models. Thermodynamic studies indicate that the adsorption process of ZnO/MgO adsorbents is an exothermic process. Based on the experimental and theoretical analysis, the adsorption mechanism for the ZnO/MgO adsorbents consisted of hydrogen bonding, n-π interaction and electrostatic interaction. The present work pioneers the potential application of ZnO/MgO adsorbents for the adsorption of CR dye and further provides experimental evidence for the synthesis of other adsorbents.

Abstract: Electrostatic interactions of polymeric charges become one of the important factors to form the polyelectrolyte complexes (PECs). In this work, PECs has successfully created through the interaction between positive charges of chitosan (CS) and negative charges of pectin (PE) based on the effect of pH and pKa of the polymers. The formation of PECs provides small particle size, positive surface charge, and high %entrapment efficiency (%EE) after loaded metronidazole (MTZ). Dropwise addition of PE solution into CS solution was carried out to form PECs. A certain concentration of chitosan and pectin fixed at ratio 3:1 while the pH of both polymers varied as pH 1, 3, 5, and 9. The alterations after forming PECs observed particle size, zeta potential, and turbidity of the solution along with FTIR, DSC, and TAG. Precipitation of PECs solution was found in the fixed pH 5 of PE solution dropwise into pH 7 and 9 CS solution, which referred to the unstable of the PECs system. The pH 1 and 9 of PE and CS obtained the large size which about 600-1200 nm, while zeta potential found a low positive charge of 5.54-11.90 mV. Thus, only the fixed pH 5 of CS solution and pH 3, 5, or 7 of PE solution to form PECs were used to load MTZ. After loaded MTZ, the particle size of the PECs was about 400-500 nm and the zeta potential was about 20-50 mV. Electrostatic interactions resulted from FTIR detected the changes in amino groups of CS and carboxyl groups of PE. Thermal analysis on DSC for determinations of melting points or transition temperatures and TGA to monitor weight loss by heat were confirmed the PECs and MTZ-PECs formation. The pH 5 of PE interacts with pH 5 of CS offered the smallest particle size as 438 nm, zeta potential about 23.5 mV, and the highest percentage of EE as about 50% of the drug-loaded. The pH 5 of PE and CS were the pH-responsive to the pKa, thus, the acidity of the polymers may provide a suitable condition to form the appropriate polyelectrolyte complexes. Keywords: Polyelectrolyte complex, polycation, polyanion, charge density

Abstract: The rheological behaviors of polyacrylonitrile (PAN) in NaSCN aqueous solutions containing different amount of Graphene oxide (GO) were investigated through both steady-state and dynamic rheological measurements. The parameters such as apparent viscosity (η_α), flow activation energy (E_η), structural viscosity index (Δη), storage modulus (G’), loss modulus (G’’) and mechanical loss factor (tanδ) were measured to illustrate the rheological behaviors of these solutions. The results showed that the apparent viscosity decreased with adding appropriate amount of GO, while the structural viscosity index, the flow activation energy and the mechanical loss factor of GO/PAN spinning solutions increased. Accordingly, a possible mechanism of GO effect on rheological behaviors of PAN solution was proposed in this work.

Abstract: Molecular self-assembly is ubiquitous in nature and has now emerged as a new approach in chemical synthesis, engineering, nanotechnology, polymer science, and materials. Molecular self-assembly has been attracting increasing interest from the scientific community in the recent years due to its importance in understanding biology and a variety of diseases at the molecular level. In the last few years, considerable advances have been made in the use of peptides as building blocks to produce biological materials for wide range of applications, including fabricating novel supra-molecular structures and scaffolding for tissue repair. Today, the study of biological self-assembly systems represent a significant advance in the molecular engineering and is a rapidly growing scientific and engineering field that crosses the boundaries of existing disciplines. Many self-assembling systems are range from bi-and tri-block copolymers to complex DNA structures as well as simple and complex proteins and peptides. The attractiveness of such bottom-up processes lies in their capability to build uniform, functional units or arrays and the possibility to exploit such structures at meso-and macroscopic scale for life and non-life science applications.

Abstract: The Cadmium^II Isophthalicacid Benzimidazole complex [Cd₂(C₈H₄O₄)₂ (C₇H₆N₂)₄(H₂O)₃], Triqua-bis (isophthalicacidato-O,O')-tetra (benzimidazole) bis (Cadmium^II),the Cd^II atom is coordinated by two isophthalicacid anions and two benzimidazole and one water molecule in a distorted octahedral configuration with six-coordinations geometry. And one isophthalicacid ligand chelates to the Cd^II atom through its one carboxylic O atoms, but the other isophthalicacid ligand chelates to the Cd^II atom through its two carboxylic O atoms. The same as another Cd^II atom. So we get a Binuclear Cd^II metal complexe. The fact clearly suggests not so much significant contribution from the electrostatic interaction in the Cd-O bonding in bidentate Binuclear Cd^II metal complexes as we gotten in mononuclear Mn^II metal complexes. Adjacent complex link to each other via hydrogen bonds forming the three-dimensional supramolecular structure.

Abstract: The Manganese^II Isovanillin complex [Mn₂(C₈H₇O₃)₄(H₂O)₂], Diaqua-tetra (isovanillinato-O,O')-bis (manganese^II),the Mn^II atom is coordinated by three isovanillinate anions and one water molecule in a distorted trigonal bipyramidal configuration with five-coordinations geometry. And one isovanillinate ligand chelates to the Mn^II atom through its methyl and hydroxy O atoms, the other two isovanillinate ligand chelates to the Mn^II atom only through its hydroxy O atoms. The same as another Mn^II atom. So we get a Binuclear Mn^II metal complexe. The fact clearly suggests not so much significant contribution from the electrostatic interaction in the Mn-O bonding in Binuclear Mn^II metal complexes as we gotten in mononuclear Mn^II metal complexes. Adjacent complex link to each other via hydrogen bonds forming the three-dimensional supramolecular structure.

Abstract: The manganese^II complex [Mn (C₉H₉O₃)₂(H₂O)₂], the Mn^II atom is located on a twofold axis and is coordinated by two ethylvanillinate anions and two water molecule in a distorted octahedral geometry. The ethylvanillinate ligand chelates to the Mn^II atom through its ethyl and hydroxyl O atoms, with greatly differing Mn-O bond distances (2.3988(15)Å and 2.0675(13)Å).Adjacent complex link to each other via hydrogen bonds forming the three-dimensional supramolecular structure.

Abstract: The cobalt^II complex [Co (C₉H₉O₃)₂(H₂O)₂], Diaqua-bis (ethylvanillinato-O,O')-cobalt^II, the Co^II atom is located on a twofold axis and is coordinated by two ethylvanillinate anions and two water molecule in a distorted octahedral geometry . The ethylvanillinate ligand chelates to the Co^II atom through its ethyl and hydroxy O atoms,with differing Co-O bond distances (2.282(2) Å and 1.9914(18) Å).Adjacent complex link to each other via hydrogen bonds forming the three-dimensional supramolecular structure.

Abstract: The nickel^II complex [Ni (C₉H₉O₃)₂(H₂O)₂], Diaqua-bis (ethylvanillinato-O,O')-nickel^II, the Ni^II atom is located on a twofold axis and is coordinated by two ethylvanillinate anions and two water molecule in a distorted octahedral geometry . The ethylvanillinate ligand chelates to the Ni^II atom through its ethyl and hydroxy O atoms,with greatly differing Ni-O bond distances (2.282(2) Å and 1.9792(16)Å). Adjacent complex link to each other via hydrogen bonds forming the three-dimensional supramolecular structure.

Abstract: Protein adsorption is driven by various interactions. The contribution of surface charge to bovine serum albumin (BSA) adsorption on hydroxyapatite (HA) ceramic was investigated by adjusting the liquid environment in which the solid particles dispersed. Zeta potentials of HA and the adsorption of BSA on the surface were tested as a function of pH, ionic strength, Ca2+ and PO4 3- concentrations in the aqueous solutions, and the results showed that both of them were greatly affected by those experimental variations. Besides, the amount of adsorbed BSA was related to the variation of zeta potential of HA, as could be well understood in terms of electrostatic interactions.