High Coverage Formation of CdS Quantum Dots on TiO₂ by the Photocatalytic Growth of Preformed Seeds

Photoelectrochemical experiments and density functional theory calculations indicated that visible-light irradiation of the CdS quantum dots (QDs)–TiO₂ direct coupling system (CdS/TiO₂) causes the electron injection from the valence band (VB) of CdS into the conduction band (CB) of TiO₂ (path 2) in addition to the inter-CB electron transfer from CdS to TiO₂ (path 1). Path 2 can be induced by the sub-bandgap excitation of CdS QDs to extend the spectral response of the CdS/TiO₂ system. For path 2 as well as path 1 to effectively work, CdS QDs should be directly deposited on the TiO₂ surface with high coverage. According to the guideline, a photocatalytic growth of the preformed seed (PCGS) technique has been developed. Transmission electron microscopy observation and X-ray photoelectron spectroscopy measurements of the CdS/TiO₂ prepared by the PCGS technique indicated that the TiO₂ surface is highly covered by CdS QDs. The technique was applied to mesoporous TiO₂ nanocrystalline films (mp-TiO₂) to yield CdS/mp-TiO₂. CdS QD-sensitized photoelectrochemical (QD-SPEC) cells with a structure of CdS/mp-TiO₂ (photoanode)|aqueous sulfide solution|Ag/AgCl (reference electrode)|Pt (cathode) were fabricated. The rate of hydrogen (H₂) generation in the QD-SPEC cell under illumination of simulated sunlight (AM 1.5, 1 sun, λ > 430 nm) increases with an increase in the TiO₂-surface coverage by CdS QDs

Hypergravity Stimulus Enhances Primary Xylem Development and Decreases Mechanical Properties of Secondary Cell Walls in Inflorescence Stems of Arabidopsis thaliana

• Background and Aims The xylem plays an important role in strengthening plant bodies. Past studies on xylem formation in tension woods in poplar and also in clinorotated Prunus tree stems lead to the suggestion that changes in the gravitational conditions affect morphology and mechanical properties of xylem vessels. The aim of this study was to examine effects of hypergravity stimulus on morphology and development of primary xylem vessels and on mechanical properties of isolated secondary wall preparations in inflorescence stems of arabidopsis