Crystallographic features and cleavage nanomorphology of chlinochlore; specific applications

• Published in: Clays and clay minerals Vol. 57; no. 2; pp. 183 - 193
• Main Authors: Valdre, Giovanni, Malferrari, Daniele, Brigatti, Maria Franca
• Format: Journal Article
• Language: English
• Published: Cham Clay Minerals Society 01-04-2009; The Clay Minerals Society; Springer International Publishing
• Subjects: AFM; applications; Biogeosciences; cation exchange capacity; chemical composition; chemical properties; chlinochore; chlorite; chlorite group; clay mineralogy; cleavage; Clinochlore; crystal chemistry; Crystal Structure; crystallography; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Exact sciences and technology; foliation; Geochemistry; Medicinal Chemistry; mica group; Mineralogy; nanomorphology; Nanoscale Science and Technology; polyhedra; rock, sediment, soil; sed rocks, sediments; Sedimentary petrology; sheet silicates; Silicates; Soil Science & Conservation; structural analysis; Surface Applications; Xas; AFM; Crystal Structure; Surface Applications; XAS; Clinochlore; adsorption; cations; crystal chemistry; morphology; topology; unit cell; chlorite; mica; cleavage; clinochlore; symmetry; DNA; crystal structure; substrates; sheet silicates; silicates; site occupancy; chemical composition; direction
• ISSN: 0009-8604; 1552-8367
• DOI: 10.1346/CCMN.2009.0570205

Natural and synthetic micas have been used widely as substrates to study biological systems; but, as in the case of negatively charged DNA, anionic charge repulsion may render micas a less than ideal templating surface for many biological systems. The purpose of this study was to investigate the potential for the chlorite clinochlore, which contains a positively charged interlayer octahedral sheet, to serve as a substrate for DNA adsorption. The relationships between clinochlore cleavage characteristics, in terms of nano-morphology, and surface potential are investigated, as are its average crystal chemistry and topology. That the structural features of clinochlore can be used successfully to condense, order, and self assemble complex biomolecules, such as DNA is also proven. A natural IIb-4 clinochlore [C1̄ symmetry, unit-cell parameters a=0.53301(4); b=0.92511(6); c=1.4348(1) (nm); α=90.420(3); β=97.509(3); γ=89.996(4)(°)] with chemical composition (Mg1.701Fe0.2452+Ti0.004Al0.998Cr0.0523+)Mg3 (Si2.939Al1.015Fe3+0.046)O10(OH7.913F0.087) was selected. The octahedral sites of the silicate layer (<M(1)-O>=0.2080 nm and <M(2)-O>=0.2081 nm) are equal and occupied by Mg, whereas the octahedral sites in the interlayer M(3) and M(4) (<M(3)-O>=0.2088 nm and <M(4)-O>=0.1939 nm) show different sizes and are mostly completely occupied by divalent (Mg2+ and Fe2+) and trivalent (Al3+) cations, respectively. The clinochlore cleaved surface is present in two forms: (1) the stripe type (0.40 nm in height, up to several micrometers long and ranging from some nanometers to a few microns in lateral size); and (2) the triangular type (0.40 nm in height). Both features may result either from interlayer sheets whose cleavage weak directions are related to the different M(3) and M(4) site occupancy, or from weak interlayer bonding along specific directions to the 2:1 layer underneath. The cleaved surface, particularly at the cleaved edges, presents high DNA affinity, which is directly related to an average positive surface and ledge potential.