title: Self-assembly of nanosized 0D clusters: CdS quantum dot-polyoxotungstate nanohybrids with strongly coupled electronic structures and visible-light-active photofunctions.
abstract: Nanohybrids of CdS-polyoxotungstate with strongly coupled electronic structures and visible-light-active photofunctions can be synthesized by electrostatically derived self-assembly of very small CdS quantum dots, or QDs, (particle size ≈ 2.5 nm) and polyoxotungstate nanoclusters (cluster size ≈1 nm). The formation of CdS-polyoxotungstate nanohybrids is confirmed by high-resolution transmission electron microscopy, elemental mapping, and powder X-ray diffraction analysis. Due to the strong electronic coupling between two semiconductors, the CdS-polyoxotungstate nanohybrids show a narrow bandgap energy of around 1.9-2.7 eV, thus reflecting their ability to harvest visible light. Time-resolved photoluminescence experiments indicate that the self-assembly between nanosized CdS and polyoxotungstate is very effective in increasing the lifetime of holes and electrons, thus indicating an efficient electron transfer between two-component semiconductors. The hybridization results not only in a significant improvement in the photostability of CdS QD but also in the creation of visible-light-induced photochromism. Of particular importance is that the present nanohybrids show visible-light-driven photocatalytic activity to produce H(2) and O(2) , which is superior to those of the unhybridized CdS and polyoxotungstate. The self-assembly of nanometer-level semiconductor clusters can provide a powerful way of optimizing the photoinduced functionalities of each component (i.e., visible-induced photochromism and photocatalysis) by means of strong electronic coupling.
authors.affiliation: Center for Intelligent Nano-Bio Materials (CINBM), Department of Chemistry and Nano Sciences, Ewha Womans University, Seoul, Korea.
authors.forename: Hyo Na
authors.initials: HN
authors.lastname: Kim
authors.forename: Tae Woo
authors.initials: TW
authors.lastname: Kim
authors.forename: Kyong-Hoon
authors.initials: KH
authors.lastname: Choi
authors.forename: In Young
authors.initials: IY
authors.lastname: Kim
authors.forename: Yong-Rok
authors.initials: YR
authors.lastname: Kim
authors.forename: Seong-Ju
authors.initials: SJ
authors.lastname: Hwang
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D002384:Catalysis; D004581:Electronics; D008027:Light; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology; D010777:Photochemistry; D045663:Quantum Dots; D017973:Tungsten Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction; D000099294:Polyoxometalates
chemical_list: D019187:Cadmium Compounds; D017973:Tungsten Compounds; C102296:polyoxometalate I; D000099294:Polyoxometalates