Crystallization of Silver Stearate from Sodium Stearate Dispersions

Abstract

Silver carboxylates, the common silver source used for photothermographic imaging materials, are normally obtained from the reaction between sodium soap (e.g., sodium stearate) and silver nitrate. They form platelet-like crystals with a lamellar structure in water at room temperature. Light microscopy investigations reveal that the formation of silver stearate (AgSt) crystals follows a diffusion-controlled mechanism. The reaction between the sodium soap and silver nitrate preferentially occurs in solution rather than on the soap fiber solid interface. Cryogenic transmission electron microscopy, together with an on-the-grid reaction technique, provides a useful tool to directly image silver stearate microstructures at the initial stages of AgSt precipitation. The AgSt reaction product first forms particles about 5 nm in size, which is similar to the d-spacing of final AgSt crystals. Those particles aggregate to produce larger and loosely packed embryonic crystals, the precursors to the ultimate silver stearate crystals.

Ag(i)-mediated self-assembly of anisotropic rods and plates in the surfactant mixture of CTAB and Pluronics

“…These hydrophilic areas are composed of the ammonium head group of CTAB and PEO groups in which chains of linear O-Ag-O bonding occurs. Lamellar formation of silver carboxylates are well known, 28,41 and based on this layer-by-layer formation of micronscale rods are obtained with silver carboxylates. 42…”

Facile Synthesis of Silver Nanoparticles in CO2-Expanded Liquids from Silver Isostearate Precursor

“…The XRD patterns reveals that AgSt exists a set of well-defined diffraction peaks, indexed as (0 k 0) planes, whereas AgISt showed only one major reflection, indexed as (030) plane. It is well-known that solid-state AgSt is an eight-membered-ring dimer composed of two Ag + ions bridged by two bidentate carboxylate groups of the stearate molecules. , The dimers are stacked in an orderly manner one next to another through the intermolecular interactions of Ag−O bonds, and the straight long alky chains in AgSt are regularly extended to grow the preferred crystal-like layered structure ,, resulting in a set of well-defined peaks in the XRD diffraction. In addition, the strong Ag−O bonds between dimers and the perfect layered structure lead to the poor solubility of AgSt in solvents.…”

Cation-Controlled Crystal Growth of Silver Stearate: Cryo-TEM Investigation of Lithium vs Sodium Stearate

“…Cryogenic transmission electron microscopy (cryo-TEM) experiments followed the procedures described previously . In preparing the specimen for cryo-TEM, an on-the-grid mixing method was used to capture the structures at reaction times of 30 s, 1 min, and 3 min, i.e., a small drop of the 0.1 wt % LiSt dispersion and a small drop of 1 wt % AgNO 3 were attached to the same holey carbon grid.…”

“…Previously, we reported the reaction and crystallization process of silver carboxylates from sodium salts of several fatty acids. − Regardless of the chain length of the carboxylate tail group (molecules with carbon numbers of 18, 20, and 22, i.e., stearate, arachidate, and behenate, were chosen), the silver carboxylate crystallization always started from AgSt spherical micelles and micelle aggregations. Such initial structures, although not thermodynamically stable, play a major role in controlling the final, stable crystal morphology and size of AgSt .…”