Continuous flow synthesis and cleaning of nano layered double hydroxides and the potential of the route to adjust round or platelet nanoparticle morphology

Abstract

Here, we report a continuous flow synthesis of nano LDH, comprising a continuous precipitation process using static mixers and followed by an immediate cleaning process via a semi-continuous centrifuge to obtain the final product in one-go. Via this synthesis setup, it is possible to independently vary the concentrations of the reactants during precipitation and at the same time ensure constant reaction conditions and an immediate “quenching” of the precipitate due to “on the flow”-washing. We found that this paves the way to adjust the synthesis parameters in a way that the final morphology of the nano-LDH particles can be controlled to be either round or platelet-like

Continuous synthesis of doped layered double hydroxides in a meso-scale flow reactor

“…In a study using a meso-scale reactor with embedded static mixer elements, particles with the mean size of ∼ 40-45 nm were obtained, similar to some of micro-reactor studies, but with a very broad size distribution [14]. There is no data in the paper to calculate residence time or micromixing time for their specific system.…”

“…We hypothesised that achieving reproducible outcome in the co-precipitation step is critically important for attaining a narrow distribution of properties of the final LDHs in the two-step synthesis method. Although there are several reports of LDH synthesis under continuous flow conditions using micro-scale [11][12][13] and meso-scale reactors [14][15][16][17][18], there are no studies detailing systematic characterizations of morphological properties and thermal stability of the produced materials. In most of the earlier studies the produced materials are characterized by broad particle size distribution.…”

Synthesis of layered double hydroxides through continuous flow processes: A review

“…It is noteworthy that these processes were all achieved without aging and washing steps. So an approach which deserves interest was developed with the objective to include in situ cleaning of the LDH particles in the continuous flow procedure, although it leads to a more complex process in two steps [87].…”

“…Also the approach developed by A. Flegler et al [87] deserves a great attention because LDH were prepared for the first time by a combination of a continuous coprecipitation followed by down-stream separation and washing in a semi-continuous tubular centrifuge [87].…”

Expanding the Horizon of Mechanochromic Detection by Luminescent Shear Stress Sensor Supraparticles

“…For the fabrication of iron oxide raspberry‐like supraparticles as quenching core material, first iron oxide nanoparticles were synthesized. This synthesis was based on procedures according to the literature . For the precipitation of iron oxide nanoparticles, FeCl 3 ⋅ 6H 2 O (8.0 mmol, 2.162 g), FeCl 2 ⋅ 4H 2 O (4.0 mmol, 0.792 g) were dissolved in water (H 2 O, 50 mL) and mixed with sodium hydroxide dissolved in water (50 mL, 1.5 m ) by pumping the two fluids with a peristaltic pump (Ismatec MCP, flow rate: 100 mL min −1 ).…”