Selective adsorption of cysteamine molecules on Au/TiO2 boosts visible light-driven photocatalytic hydrogen evolution.

Photocatalytic evolution of hydrogen is becoming a research hotspot because it can help to produce clean energy and reduce environmental pollution. Titanium dioxide (TiO2) and its composites are photocatalysts that are widely used in hydrogen evolution because of their high abundance in nature, low price, and high photo/chemical stability. However, their catalytic performances still need to be further improved, particularly in the visible light spectrum. Herein, visible light-driven photocatalytic evolution of hydrogen on Au/TiO2 nanocomposite is enhanced âˆ¼ 10 folds by selectively functionalizing the nanocomposite with cysteamine molecules. It is revealed that the amine group (-NH2) in cysteamine favors the transfer and separation of photo-generated hot carriers. The rate of hydrogen produced can be further tuned by varying the ionization of the functionalized molecules at different pH values. This work provides a simple, convenient, and effective method that can be used to improve the photocatalytic evolution of hydrogen. This method can also be used for many other nanocatalysts (e.g., Au-MoS2, Au-BiVO4) and catalytic reactions (e.g., carbon dioxide reduction, nitrogen reduction).

Monitoring the Thiol/Thiophenol Molecule-Modulated Plasmon-Mediated Silver Oxidation with Dark-Field Optical Microscopy.

Surface plasmon can trigger or accelerate many photochemical reactions, especially useful in energy and environmental industries. Recently, molecular adsorption has proven effective in modulating plasmon-mediated photochemistry, however the realized chemical reactions are limited and the underlying mechanism is still unclear. Herein, by using in situ dark-field optical microscopy, the plasmon-mediated oxidative etching of silver nanoparticles (Ag NPs), a typical hot-hole-driven reaction, is monitored continuously and quantitatively. The presence of thiol or thiophenol molecules is found essential in the silver oxidation. In addition, the rate of silver oxidation is modulated by the choice of different thiol or thiophenol molecules. Compared with the molecules having electron donating groups, the ones having electron accepting groups accelerate the silver oxidation dramatically. The thiol/thiophenol modulation is attributed to the modulation of the charge separation between the Ag NPs and the adsorbed thiol or thiophenol molecules. This work demonstrates the great potential of molecular adsorption in modulating the plasmon-mediated photochemistry, which will pave a new way for developing highly efficient plasmonic photocatalysts.

Synthesis of Thin Bi9 O7.5 S6 Nanosheets for Improved Photodetection in a Wide Wavelength Range.

Bismuth-based compounds possess layered structures with a variety of stacking modes, endowing the compounds with diverse properties. As one type of bismuth oxysulfides, Bi9 O7.5 S6 nanocrystals has great applications in photodetection; however, the responsivity of bulky Bi9 O7.5 S6 is limited due to the poor charge separation. Herein, single-crystalline Bi9 O7.5 S6 thin nanosheets are successfully synthesized by using a solvothermal method. The thickness of the obtained Bi9 O7.5 S6 nanosheets is down to 15 nm and can be easily tuned by varying the reaction period. Moreover, the Bi9 O7.5 S6 nanosheets show strong light absorption in the visible and near infrared range, making it a promising candidate in optoelectronics. As a demonstration, the thin Bi9 O7.5 S6 nanosheets are used as active layer in an optoelectronic device, which exhibits sensitive photoelectric response to light in a wide range of 400-800 nm. The responsivity of the device reaches up to 1140 µA W-1 , and the performance of the device is stable after long-period illumination. This work demonstrates a great potential of the thin Bi9 O7.5 S6 nanosheets in optoelectronic devices, and these nanosheets may also be extended to various optoelectronic applications.

Preparation and applications of freestanding Janus nanosheets.

In the family of Janus nanomaterials, Janus nanosheets possess not only the advantages of Janus nanomaterials, but also the advantages of two-dimensional nanosheets, endowing them with many extraordinary properties. Therefore, Janus nanosheets have great potential in the fields of interfacial engineering, catalysis, and molecular recognition. This review summarizes and discusses the recent advances in both the preparation and applications of freestanding Janus nanosheets. After a short introduction to different types of Janus nanosheets, a variety of methods for preparing freestanding Janus nanosheets are introduced, including the surface reaction, interface reaction, emulsion reaction, self-assembly, and stripping of non-Janus nanosheets, as well as selective grafting of existing Janus nanosheets. Then, the wide applications of Janus nanosheets in the fields of emulsification, catalysis, polymer reinforcement, nanomotors, and molecular recognition are summarized in detail. Finally, a discussion on the remaining challenges and future perspectives in this field is included. This review will not only deepen the understanding of Janus nanosheets, but also benefit the designs and fabrications of extraordinary and multi-functional Janus nanosheets.