Charge density matching

Layered Heterometallic Vanadates Charge Density Matching... 

The charge densities and compositions of many known solids with VxOy layers were screened for possible charge density matches with M(pyz)x (M = Fe, Co, Ni, Cu, Zn) layers [35, 52], as an aid in the synthesis of new heterometallic multilayered vanadates. Close matches were found with M(pyz)x (M = Fe, Co, Ni) coordination polymers, ranging from 0.022/A -0.053/A, and which might suitably form in the presence of the flexible types of V2O5 layers. For example, Co(pyz) layers of chains in Co(pyz)(V03)2 [53] have a charge density of... 

El Haskouri, J., M. Roca, S. Cabrera, J. Alamo, A. Beltran-Porter, D. Beltran-Porter, M. D. Marcos, and P. Amoros. 1999. Interface charge density matching as driving force for new mesostruc-tured oxovanadium phosphates with hexagonal structure, [CTA]xVG BI 0. Chem. Mater. 11 1446-1454. 

Charge-density matching principle and its application to uranyl oxocompounds... 

These examples demonstrate clearly that charge densities of uranyl-based sheets are in general smaller than charge densities of metal phosphate and vanadate units in lamellar compounds. However, the very existence of nanocomposite vanadates and metal phosphates means that the charge-density matching principle in these compounds is observed. Then how does it work for... 

Actinide peroxide nanospheres [3] and uranyl selenate nanotubules [4,5] represent the first examples of nanoscale stmctures in actinide compounds. It is noteworthy that, very frequently, formation of nanostmctures corresponds to organic-inorganic composites with clearly defined interfacial interactions. To describe the character of these interactions, one can use the charge-density matching concept with some modifications related to the basic chemical properties of actinides. 

Stucky s mechanism can explain more experimental results in a wide range. After improvements/151 it guides the synthesis of mesoporous inorganic materials. In fact, the initial basis of Stucky s mechanism is the charge-density-matching model based on the fact of phase transformation from lamellar phase to hexagonal phase. 

The generalized liquid-crystal-template mechanism focuses on the interaction between surfactant molecules and inorganic species. Surfactant molecules assemble with inorganic species to form the liquid-crystal-like mesophase. The three main interactions between surfactant and inorganic species are (i) electrostatic interaction (the charge-density match plays the key role), (2) hydrogen bond, in particularly for those neutral templates, and (iii) covalent bond. 

In the real synthesis systems, the surfactant effective packing parameter, g, are mainly affected by the following factors (1) charge, composition, molecular shape, and structure of surfactant, (2) the interactions between surfactant and inorganic species (e.g., charge-density matching), (3) reaction parameters and conditions concentration, pH, ion strength, temperature, etc. 

In mesophase synthesis, both the silica and surfactant show similar effects on the formation of mesophases. The effects of the surfactant concentration can be explained in two ways. One is packing of the surfactant, and the other is charge density matching... 

S.H. Tolbert, C.C. Landry, G.D. Stucky, B.F. Chmelka, P. Norby, J.C. Hanson, and A. Monnier, Phase Transitions in Mesostructured Silica/Surfactant Composites Surfactant Packing and the Role of Charge Density Matching. Chem. Mater., 2001, 13, 2247-2256. 

Table 2.2 Surfactants used for templating, conditions under which mesoporous silicas have been formed, and the interaction between surfactant (S) and inorganic species (I), from the charge-density matching model.Note, X is the surfactant counterion, H is a hydrogen ion...

Egger et challenged both the formation of silica coated micelles and the idea of charge density matching in the case of acidic syntheses of SBA-1... 

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