Synthesis of Diamond-Shape Titanate Molecular Sheets with Different Sizes and Realization of Quantum Confinement Effect during Dimensionality Reduction from Two to Zero

Abstract

Synthesis of semiconductor nanoparticles with uniform shapes, sizes, and compositions in series with a gradual size reduction has not been achieved for two-dimensional molecular sheets. We report a large-scale (>2.6 g) synthesis of 0.75-nm-thick diamond-shape lepidocrocite-type titanate molecular sheets with the sizes decreasing from (27.3, 19.1) to (7.7, 5.5), where the numbers in parentheses represent the long and short diagonal lengths, respectively, in nm. This is the first example of synthesizing semiconductor nanoparticles in series with the dimensionality reduction from two to zero, without coating the surfaces with surface-passivating ligands. The titanate molecular sheets showed three exciton-absorption bands in the 4.0-6.5 eV region, the absorption energies of which increased with decreasing the area. Contrary to the common belief, the per-unit cell oscillator strengths gradually increased with increasing area and the per-particle oscillator strengths increased in proportion to the area. The average reduced exciton masses along the two diagonal axes were 0.10 and 0.11 m e, respectively, which were much smaller than those of bulk titanates (by 60-130 times). The estimated average Bohr radii along the two-diagonal axes were 4.8 and 4.3 nm, respectively.

Synthesis of Uniform Layered Protonated Titanate Hierarchical Spheres and Their Transformation to Anatase TiO2 for Lithium‐Ion Batteries

“…[14][15][16][17][18][19] Moreover, from the perspective of materials synthesis, LPTs are very important because they could serve as unique precursors for the synthesis of different nanostructured TiO 2 -based functional materials. [20,21] Besides the sporadic reports on the direct synthesis of single-or multiple-layered protonated titanate nanosheets, [18,22] traditional alkaline hydrothermal methods usually result in alkali metal titanates with one-dimensional (1D) structures (for example, nanotubes, nanobelts, and nanorods), [23][24][25] which require an additional ion-exchange step to transform to their protonated forms. On the other hand, intercalation and exfoliation of lamellar compounds have been a classic research topic in inorganic and materials chemistry, [26][27][28] and single-layered titanate nanosheets have already been synthesized through a "top-down" approach.…”

Morphology of anatase crystals and their aggregates synthesized hydrothermally from aqueous mixtures of titanium alkoxide and different alkylammonium hydroxides

“…The solutions were prepared by mixing Ti(OPr i )4 and N(CH3)4OH, 7), 8) and included layered titanate colloids with a lepidocrocite-type structure. 4), 9) TEM observation of the aggregates suggested that the stacking of the titanate colloids and sequential topotactic structural conversion of the titanate to anatase play an important role in the formation of the acicular anatase crystals, as shown in Fig. 2.…”

Fluorescence Properties of the Lanthanide Supported onto Titanate Nanosheets

“… Low-dimensional structures such as nanotubes and nanosheets continue to attract increased research attention [1][2][3][4], as exemplified by the wide use of TNSs (Titanate Nanosheets) in a variety of engineering, chemical and optical applications. Single nanosheets comprise ultra-thin (10 -10 -10 -8 m) monocrystals and can be stacked to form a layered structure.…”

“…Recently, several groups have synthesized TNSs by liquid-phase methods [1,12], revealing that these materials exhibit diamond-like shape, water dispersibility and photocatalytic activity [13]. The photocatalytic activity of TNSs can be enhanced by decorating their surface with suitable metals to obtain metal/TNS composited.…”