title: 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.
authors.affiliation: Center for Microcrystal Assembly, Department of Chemistry, and Program of Integrated Biotechnology, Sogang University, Seoul 121-742, Korea.
authors.forename: Eunju Lee
authors.initials: EL
authors.lastname: Tae
authors.forename: Kee Eun
authors.initials: KE
authors.lastname: Lee
authors.forename: Jong Seok
authors.initials: JS
authors.lastname: Jeong
authors.forename: Kyung Byung
authors.initials: KB
authors.lastname: Yoon
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry*; D011789:Quantum Theory; D012666:Semiconductors; D013059:Spectrum Analysis, Raman; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide; D014025:Titanium