Shuang Gao

Internal Polarization Modulation in Bi2MoO6 for Photocatalytic Performance Enhancement under Visible-Light Illumination

A built-in electric field from polarization inside polar photocatalysts could provide the driving force for photogenerated electrons and holes to move in opposite directions for better separation to improve their photocatalytic performance. The photocatalytic performance of a polar photocatalyst of Bi2 MoO6 has been enhanced through the precise control of its structure to increase internal polarization. DFT calculations predicted that a shortened crystal lattice parameter b in Bi2 MoO6 could induce larger internal polarization, which was achieved by the modulation of the pH of the reaction solution during a solvothermal synthetic process. A series of Bi2 MoO6 samples were created with reaction solutions of pH≈1, 4, and 8; the crystal lattice parameter b was found to decrease gradually with increasing solution pH. Accordingly, these Bi2 MoO6 samples demonstrated a gradually enhanced photocatalytic performance with decreasing crystal lattice parameter b, as demonstrated by the photocatalytic degradation of sulfamethoxazole/phenol and disinfection of Staphylococcus aureus bacteria under visible-light illumination due to improved photogenerated charge-carrier separation. This study demonstrates an innovative design strategy for materials to further enhance the photocatalytic performance of polar photocatalysts for a broad range of technical applications.

Photoinduced reversible lattice expansion in W-doped TiO2 through the change of its electronic structure

External stimulations of applied force or voltage have been reported to induce crystal lattice dimension changes with the order of 0.1% or above by imposing external mechanical or electric forces on atoms forming the lattice for various types of materials, including oxides, metals, polymers, and carbon nanostructures. As far as we know, however, no report is available for similar level changes in oxides from their internal electronic structure changes induced by photoirradiation. We show that reversible lattice expansion comparable to those by applied force or voltage can be induced by UV-irradiation on an oxide of W-doped TiO2 nanotubes through the reversible changes of its internal electronic structure by the accumulation and release of photogenerated electrons in W-dopants when UV-illumination is on and off. This photoirradiation-induced reversible lattice expansion and subsequent optical, electric, and magnetic property changes may also be present in other material systems by proper material design if...

4D Printing of Complex Structures with a Fast Response Time to Magnetic Stimulus

A poly(dimethylsiloxane)/Fe (PDMS/Fe) composite ink was developed for reversible four-dimensional (4D) printing to create magnetically responsive three-dimensional (3D) structures with a fast response time for their structure evolvements under external magnetic field. These 3D structures could obtain or lose high magnetization immediately by the on or off of an external magnetic field due to the low magnetic coercive force and the high magnetic permittivity of soft magnetic Fe particles in this composite ink, whereas PDMS in this composite ink served as the flexible matrix component to ensure their shape recovery. As exampled by a 3D butterfly with the fast flapping of its wings under an external magnetic field, complex 3D structures created by 4D printing with this PDMS/Fe ink could have the reversible magnetically stimulated structure evolvement property and develop designed magnetically induced motions with a fast response time for various magnetomechanical applications. Furthermore, structure evolvements of these 3D structures could also induce structure-related property changes, as demonstrated by a 3D terahertz photonic crystal (3D-TPC) device with remotely tunable terahertz properties, which could create novel functionalities for various functional devices created by 4D printing from this kind of ink through external magnetic field stimulation.