Soft Chemical Routes to Heterostructured High-T_c Superconducting Materials

Abstract

Recently, inorganic/inorganic and organic/inorganic heterostructured materials have attracted considerable research interest, due to their unusual physicochemical properties, which cannot be achieved by conventional solid-state reactions. In order to develop new hybrid materials, various synthetic approaches, such as vacuum deposition, Langmuir–Blodgett films, selfassembly, and intercalation techniques, have been explored. Among them, the intercalation reaction technique—that is, the reversible insertion of guest species into the two-dimensional host lattice—is expected to be one of the most effective tools for preparing new layered heterostructures because this process can provide a soft chemical way of hybridizing inorganic/inorganic, organic/inorganic, or biological/inorganic compounds. In fact, the intercalation/deintercalation process allows us to design high-performance materials in a solution at ambient temperature and pressure, just as “soft solution processing” provides a simple and economical route for advanced inorganic materials by means of an environmentally benign, lowenergy method. These unique advantages of the intercalation technique have led to its wide application to diverse fields of the solid-state sciences, namely, secondary (rechargeable) batteries, electrochromic systems, oxidation–reduction catalysts, separating agents, sorbents, and so on. Through these extensive studies, many kinds of low-dimensional compounds have been developed as host materials for the intercalation reaction, including graphite, transition-metal chalcogenides, transitionmetal oxides, aluminosilicates, metal phosphates, metal chalcogenohalides, and so on. Recently, the area of intercalation chemistry has been extended to high-Tc superconducting copper oxides, resulting in remarkable structural anisotropy.

A novel synthetic route to TiO2-pillared layered titanate with enhanced photocatalytic activity

“…More recently, exfoliation of various layered host materials has been extensively studied since it allows the fabrication of thin/thick films or nanoparticles through lattice engineering. [7][8][9] Among various semiconducting compounds, a caesium titanate with a lepidocrocite-like structure is known to be exfoliated into single sheets by intercalating a bulky tertiary ammonium salt. 10 In light of this, we have developed a novel exfoliation-restacking route to generate a well ordered TiO 2pillared layered titanate with enhanced photocatalytic activity.…”

Topochemical Manipulation of Perovskites: Low‐Temperature Reaction Strategies for Directing Structure and Properties

“…Extremely noteworthy are the several excellent monographs that have been published over the last three decades on various aspects of topochemical reactions. Works highlighting both ion‐exchange and intercalation chemistry17, 27–33 have appeared with some of the more recent publications specifically focusing on the use of topochemical strategies 34, 35. While this report does touch on those earlier studies, it strives more to emphasize results from the last few years with an outlook to the future.…”

“…Additional oxidative intercalation reactions involving layered perovskites include manipulations of AV‐type high‐temperature superconducting copper oxides. Iodine intercalation into AV superconductors,34, 94, 95 such as Bi 2 Sr 2 CaCu 2 O y , was found to occur with the intercalate inserting into the bismuth–oxide layers and the relative layer orientation transforming from a staggered to an eclipsed arrangement. Staging can be realized in these systems as well, where iodine occupies alternating Bi–O layers.…”

Electrophoretic deposition of negatively charged tetratitanate nanosheets and transformation into preferentially oriented TiO2(B) film

“…Since EPD makes use of the charge of particles for deposition, it is similar to the electrostatic-assembly method. Uniform films from waterswollen clay [22][23][24][25] and exfoliated-cuprate superconductors 26 have been fabricated by EPD. The use of EPD for film processing of layered titanates has recently been reported.…”