Rutile TiO2 is a promising photocatalyst due to its narrower band gap, higher thermodynamic stability and fewer intragrain defects. However, it has not yet to achieve comparable photocatalytic activity to anatase TiO2 owing to its higher recombination rate of electron-hole pairs. In order to effectively separate the electron-hole pairs in rutile TiO2, we propose a facet heterojunction (FH) structure to prolong the lifetime of photogenerated electrons. Ultrathin TiO2 nanosheets with different facets were in-situ coated on TiO2 nanorod substrates, where facet heterojunctions are built among nanosheets as well as between nanosheets and nanorod substrates. The as-prepared rutile TiO2 with FH mechanism (FH-TiO2) served as an effective photocatalyst for water splitting. More than 45 and 18 times higher of photogenerated current density and H2 production rate were obtained respectively, compared to pure rutile TiO2 nanorod. Moreover, FH-TiO2 delivered 0.566 mmol g -1 h -1 H2

No abstract

Of various chemosensory protocols, the color change observed by the naked eye is considered to be a conceivable and on-site way to indicate the presence of an analyte. We herein designed a ratiometric fluorescence probe by hybridizing dual-emission quantum dots (QDs) and demonstrated its efficiency for on-site visual determination of copper ions. The hybrid probe comprises two sizes of cadmium telluride QDs emitting red and green fluorescence, respectively, in which the red-emitting ones are embedded in silica nanoparticles and the green-emitting ones are covalently linked onto the surface. The fluorescence of the embedded QDs is insensitive to the analyte, whereas the green emissive QDs are functionalized to be selectively quenched by the analyte. Upon exposure to different amounts of copper ions, the variations of the dual emission intensity ratios display continuous color changes from green to red, which can be clearly observed by the naked eye. The limit of detection for copper is estimated to be 1.1 nM, much lower than the allowable level of copper (~20 μM) in drinking water set by U.S. Environmental Protection Agency. The probe is demonstrated for the determination of copper ions in lake water and mineral water samples, especially for visually monitoring copper residues on herb leaves. This prototype ratiometric probe is simple, fully self-contained, and thus potentially attractive for visual identification without the need for elaborate equipment.