Role of Mass Transport in the Deposition, Growth, and Transformation of Calcium Carbonate on Surfaces at High Supersaturation

Abstract

We demonstrate how combined in-situ measurements and finite element method modeling can provide new insight into the relative contribution of mass transport to the growth of calcium carbonate on two model surfaces, glass and gold, under high-supersaturation conditions relevant to surface scaling. An impinging jet-radial flow system is used to create a highsupersaturated solution at the inlet of different cells: an optical microscope cell presenting a glass surface for deposition and quartz crystal microbalance (QCM) and in-situ IR spectroscopy cells, both presenting a gold surface. The approach described is quantitative due to the well-defined mass transport, and both time-lapse optical microscopy images and QCM data are analyzed to provide information on the growth kinetics of the calcite crystals. Initially, amorphous calcium carbonate (ACC), formed in solution, dominates the deposition process. At longer times, the growth of calcite is more significant and, on glass, is observed to consume ACC from the surface, leading to surface regions depleted of ACC developing around calcite microcrystals. On Au, the mass increase becomes linear with time in this region. Taken together, these microscopic and macroscopic measurements demonstrate that calcite growth has a significant component of mass transport control at high supersaturation. Finite element method (FEM) simulations of mass-transport-limited crystal growth support the strong mass transport contribution to the growth kinetics and further suggest that the observed growth must be sustained by more than just the Ca 2+ and CO 3 2− in solution, with dissolution/direct attachment of ACC and/or ion pairs also contributing to the growth process.

On-Demand Electrochemical Fabrication of Ordered Nanoparticle Arrays using Scanning Electrochemical Cell Microscopy

“…The experimental results (see Figure ) shown here deviate from this classical model in two significant ways. First, the transients adopt a steady-state value after a few seconds, which can be attributed to the mass-transport limitations imposed by the SECCM geometry. , Second, the currents are much larger than those predicted by eq on similar time scales. This is due to these experiments being carried out using solutions of relatively low ionic strength to avoid complications related to crystallization, and as a result, the transport of Ag + will be impacted to a significant degree by migration.…”

“…Here, we demonstrate that scanning electrochemical cell microscopy (SECCM) − can be utilized to form well-ordered NP arrays in a powerful, instantly reconfigurable manner. In SECCM, electrolyte-filled pipets are utilized to define nanometer-scale electrochemical interfaces which enable the high-resolution analysis of chemical processes spanning electrocatalysis, − anodic dissolution, , photoelectrochemistry, − ionic transport, and crystallization …”

“…In SECCM, electrolyte-filled pipets are utilized to define nanometer-scale electrochemical interfaces which enable the high-resolution analysis of chemical processes spanning electrocatalysis, 39−44 anodic dissolution, 45,46 photoelectrochemistry, 47−52 ionic transport, 53 and crystallization. 54 Here, SECCM was utilized to synthesize ordered arrays of isolated Ag NPs via electrodeposition from pipets containing metal salt precursors. Direct growth is considered more reproducible and stable compared to more commonly employed drop-casting methods, 8 and the use of SECCM allows the localized direct growth of nanoparticles in a controlled manner for patterning.…”

Calcium Carbonate Particle Synthesis in a Confined and Dynamically Thinning Layer on a Spin-Coater – in Situ Deposition for Cell Adhesion

“…To compare with a previously reported precipitation method (during the flow) [65] , a drop-casting experiment was performed. Over the same substrate dimensions, initial volume (200 µL), and salt concentrations.…”

“…From direct observation, the growth rate equals 18 × 10 -8 ± 4 × 10 -9 m/s, three times more than spin coater synthesis. We cannot compare spin and drop coating methods [65]. Both systems differ in mixing conditions and operate at different natural scales, several microns film height for drop casting and few microns in the case of typical htr for spin casting (Figure 3).…”