Atomic Force Microscopic Imaging of Biomineral Powder Samples Formed by Deposits from Ethanolic Suspensions
A sample preparation method was developed that facilitates imaging of powders by force microscopy. The feasibility of the method was tested by imaging a NaC1 sample prepared in a like manner. The characteristic face-centered cubic (fcc) structure common to the sodium halide salts was apparent in NaC1 atomic scale images. A periodicity of 0.60 nm, which is within 6% of the value of the NaC1 lattice constant, was measured.
By suspending biomineral powders in ethanol and depositing an aliquot onto a suitable substrate, the images of hydroxyapatite ([Ca10(PO4)6(OH)2]) and brushite ([CaHPO4. 2H2O]) were obtained. On glass substrates, brushite formed flat platelets. Atomic spacings were found to be 0.45 nm and 0.60 nm, which agree well with published values for its <110> crystal plane. In contrast, hydroxyapatite primarily formed well-isolated clusters with atomic spacings of 0.43 nm and 0.68 nm, in agreement with published values for its <110> and <001> crystal planes, respectively.
Preliminary results indicate that substrates affect the structure of the deposits. Structural differences of the two mineral deposits on glass and mica were observed.
KeywordsAtomic Force Microscopy Crystal Plane Dicalcium Phosphate Atomic Spacing Phosphate Dihydrate
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