Precise size control of layered double hydroxide nanoparticles through reconstruction using tripodal ligands

Abstract

Precise size control of layered double hydroxide nanoparticles (LDHNPs) is crucial for their applications in anion exchange, catalysis, and drug delivery systems. Here, we report the synthesis of LDHNPs through a reconstruction method, using tripodal ligands (e.g., tris(hydroxymethyl)aminomethane; THAM). We found that the mechanism of reconstruction at least includes a dissolution-recrystallization process rather than topotactic transformation. THAM is immobilized on the surface of recrystallized LDHNPs with tridentate linkages, suppressing their crystal growth especially in lateral directions. The particle size of the LDHNPs is precisely controlled by the concentration of THAM regardless of the synthetic routes, such as coprecipitation and reconstruction. It is suggested that the particle size is controlled on the basis of Ostwald ripening which is governed by the equilibrium of the surface modification reaction.

Selective Covalent Modification of Layered Double Hydroxide Nanoparticles with Tripodal Ligands on Outer and Interlayer Surfaces

“…Tris-NH 2 was used both as a base for coprecipitation of LDHNPs and as a modifier. In our previous studies, − MgAl LDHs and metal hydroxides were modified with tripodal ligands by the reaction at 80 °C; thus, the interlayer-modified CoAl LDHNPs were synthesized at this temperature at the first time. Because no solid product precipitated at 80 °C due to the formation of stable complexes between Co 2+ and Tris-NH 2 (Table , entry 0), the reaction solution was transferred to a tightly capped 100 mL autoclave and heated at 180 °C for 24 h. A gel precipitated in the solution after the hydrothermal treatment.…”

“…We have reported that tripodal ligands (R–C­(CH 2 OH) 3 (R = NH 2 , CH 2 OH, NHC 2 H 4 SO 3 H); denoted as Tris-R hereafter) with three bonding sites form bonds stable to hydrolysis, with outer surface hydroxy groups of MgAl LDHs − and the interlayer surface of various brucite-type metal hydroxides. , Although a monodentate M–O–C bond (M is a metal cation) is unstable to hydrolysis, a similar bond can be stabilized, forming a tridentate bond from a molecule. The modification proceeds in situ during the formation of LDHs without exclusion of CO 2 .…”

“…The LDHNPs can also be used as precursors of highly active mesoporous solid base catalysts . In addition, the surface modification with tripodal ligands was applicable to the coprecipitation method as well as to the reconstruction method . Meanwhile, when a metal hydroxide composed only of divalent cations (Mg, Co, Ni, Fe, Mn, Cu) is synthesized in the presence of the tripodal ligands, hybrid layered metal hydroxides, whose interlayer surface is hybridized homogeneously with the tripodal ligands, were obtained. , Although common layered metal hydroxides cannot be exfoliated in water, hybrid layered metal hydroxides were straightforwardly delaminated in water under sonication because of the weakened interlayer interactions.…”

Aspect Ratio Control of Layered Double Hydroxide Nanosheets and Their Application for High Oxygen Barrier Coating in Flexible Food Packaging

“…The reconstruction of an amorphous LDO back to a crystalline LDH is well-known, and this process is often referred to as “a memory effect”. , For example, during calcination of Mg 2 Al-CO 3 LDH, the layered structure collapses by dehydroxylation of the metal hydroxide layers and by interlayer carbonate ion decomposition releasing CO 2 , upon rehydration in air, the crystalline layered structure reforms with concomitant CO 2 capture from the atmosphere to form the interlayer charge compensating carbonate anions. Our earlier work indicates that reconstruction is actually a dissolution-recrystallization , process and that high aspect ratio LDH NS can be prepared using an aqueous concentrated glycine solution . Therefore, in order to gain more insight into this process we have explored if the aspect ratio of the isolated LDH nanosheets can be rationally controlled by the key process parameters such as calcination temperature and duration of reconstruction.…”

Trends in Layered Double Hydroxides‐Based Advanced Nanocomposites: Recent Progress and Latest Advancements

“…LDHs offer a peculiar characteristic feature of the memory effect, through which the structure of LDHs can be reconstructed after calcination. [ 75 ] Despite the success, the reconstruction of LDHs often results in several shortcomings of the carbonate contamination, amorphous end product, and encapsulation of some impurities. Owing to these facts, it is highly required to apply the inert atmosphere in the reconstruction of LDHs.…”