Characterization of Calcined and Reduced Multi-Component Co−Ni−Mg−Al-Layered Double Hydroxides

Synthesis and Thermal Decomposition of High-Entropy Layered Rare Earth Hydroxychlorides

The synthesis of multicomponent and high-entropy compounds has become a rapidly developing field in advanced inorganic chemistry, making it possible to combine the properties of multiple elements in a single phase. This paper reports on the synthesis of a series of novel high-entropy layered rare earth hydroxychlorides, namely, (Sm,Eu,Gd,Y,Er)2(OH)5Cl, (Eu,Gd,Tb,Y,Er)2(OH)5Cl, (Eu,Gd,Dy,Y,Er)2(OH)5Cl, and (Eu,Gd,Y,Er,Yb)2(OH)5Cl, using a homogeneous hydrolysis technique under hydrothermal conditions. Elemental mapping proved the even distribution of rare earth elements, while luminescence spectroscopy confirmed efficient energy transfer between europium and other rare earth cations, thus providing additional evidence of the homogeneous distribution of rare earth elements within the crystal lattice. The average rare earth cation radii correlated linearly with the unit cell parameters (0.868 < R2 < 0.982) of the high-entropy layered rare earth hydroxychlorides. The thermal stability of the high-entropy layered rare earth hydroxychlorides was similar to that of individual hydroxychlorides and their binary solid solutions.

General synthesis and delamination of highly crystalline transition-metal-bearing layered double hydroxides

In this paper, we describe a general process for the synthesis and delamination of a family of highly crystalline Al-based and transition-metal-bearing layered double hydroxides (LDHs). Large-sized and monodispersed hexagonal platelike particles of binary-component M(II)-Al-CO3 and ternary-component M(II)-M'(II)-Al-CO3 LDHs (M(II) and M'(II) = Fe, Co, Ni, or Zn) were prepared at first by the urea method under optimized conditions. These CO32--LDHs were converted into other monovalent-anion-containing LDHs by means of a salt-acid treatment and subsequent anion-exchange processes. Finally, well-defined LDH nanosheets were obtained by delamination of NO3--LDHs in formamide.

Layered double hydroxide minerals as possible prebiotic information storage and transfer compounds

One of the fundamental difficulties when considering the origin of life on Earth is the identification of an emergent system that not only replicated, but also had the capacity to undergo discrete mutation in such a way that following generations might inherit and pass on the mutation. We speculate that the layered double hydroxide (LDH) minerals are plausible candidates for a proto-RNA molecule. We describe a hypothetical LDH-like system which, when intercalated with certain anions, forms crystals with a high degree of internal order giving rise to novel information storage structures in which replication fidelity is maintained, a concept we use to propose an explanation for interstratification in terephthalate LDHs. The external surfaces of these hypothetical crystals provide active sites whose structure and chemistry is dictated by the internal information content of the LDH. Depending on the LDH polytype, the opposing external surfaces of a crystal may give rise to reactive sites that are either complementary or mirror images of each other, and so may be chiral. We also examine similarities between these proposed "proto-RNA" structures and the DNA that encodes the hereditary information in life today, concluding with a hypothetical scenario wherein these proto-RNA molecules predated the putative RNA-world.