One-step fabrication of TiO2/graphene hybrid mesoporous film with enhanced photocatalytic activity and photovoltaic performance

Controllable Photoreduction of Graphene Oxide/Gold Composite Using a Shaped Femtosecond Laser for Multifunctional Sensors

The mixture of graphene oxide and noble metal nanoparticles has been widely used in flexible multifunctional sensors. Femtosecond lasers are regarded as useful tools for sensor fabrication through direct inscribing. Normally, the laser power is adjusted to optimize the sensing performances. However, the process between the laser and the sample can be effectively altered by the temporal distribution of the pulse and the laser wavelength. This paper proposes a controllable photoreduction of graphene oxide/gold composite method using a shaped femtosecond laser and promotes its application on multifunctional sensors. Different from the strong reliance of the photoreduction process on laser fluence, femtosecond laser shaping expands the controllability range of the photoreduction degree. By combining the parameters of fluence, temporal distribution, laser wavelength, humidity, and strain multifunctional sensors can be both optimized by controlling the laser reduction. The strain sensor exhibits good linearity with a gauge factor of 67.2 in a strain range of 28.2%; the sensitivity of the humidity sensor is improved by 68.4%. The humidity sensor maintains its performance after 28 days, and the strain sensor maintains its stability after 5000 cycles of stretching. The multifunctional sensor can be applied to detect human breath and human pulse and holds value for human health monitoring.

Uniform decoration of UiO-66-NH2 nanooctahedra on TiO2 electrospun nanofibers for enhancing photocatalytic H2 production based on multi-step interfacial charge transfer

Metal-organic framework (MOF) materials have been extensively incorporated with inorganic semiconductor photocatalysts to improve their photocatalytic activity through an efficient charge transfer process across their heterointerface. In this work, octahedral UiO-66-NH2 MOFs with edge-lengths of 110-330 nm are uniformly decorated on the surface of TiO2 electrospun nanofibers by a traditional solvothermal method combined with activation pretreatment. Before the solvothermal growth of UiO-66-NH2, the TiO2 electrospun nanofibers were activated in NaOH solution to etch the TiO2 surface for allowing the exposure of lattice oxygen. The exposed lattice oxygen on the TiO2 surface could interact with the MOF precursor of Zr4+ ions, thus enabling octahedral UiO-66-NH2 to grow uniformly on the surface of TiO2 nanofibers with an intimate Ti-O-Zr hetero-interface. Such an intimate hetero-interface provides an effective channel for boosting the electron transfer between UiO-66-NH2 and TiO2 in their heterostructure. Thus, the UiO-66-NH2/TiO2(anatase) heterostructures exhibited enhanced photocatalytic activity for H2 production as compared to either TiO2(anatase) nanofibers or UiO-66-NH2 nanooctahedra in the presence of Rhodamine B (RhB) as a sensitizer under visible light irradiation. In particular, the decoration of UiO-66-NH2 nanooctahedra on anatase/rutile mixed TiO2 nanofibers could induce further enhancement of the photocatalytic H2 production. The enhanced photocatalytic activity is attributed to the multi-step continuous interfacial transfer of photoinduced electrons with the way of RhB → UiO-66-NH2 → TiO2(anatase) → TiO2(rutile).

Applications of Ceramic/Graphene Composites and Hybrids

Research activity on ceramic/graphene composites and hybrids has increased dramatically in the last decade. In this review, we provide an overview of recent contributions involving ceramics, graphene, and graphene-related materials (GRM, i.e., graphene oxide, reduced graphene oxide, and graphene nanoplatelets) with a primary focus on applications. We have adopted a broad scope of the term ceramics, therefore including some applications of GRM with certain metal oxides and cement-based matrices in the review. Applications of ceramic/graphene hybrids and composites cover many different areas, in particular, energy production and storage (batteries, supercapacitors, solar and fuel cells), energy harvesting, sensors and biosensors, electromagnetic interference shielding, biomaterials, thermal management (heat dissipation and heat conduction functions), engineering components, catalysts, etc. A section on ceramic/GRM composites processed by additive manufacturing methods is included due to their industrial potential and waste reduction capability. All these applications of ceramic/graphene composites and hybrids are listed and mentioned in the present review, ending with the authors' outlook of those that seem most promising, based on the research efforts carried out in this field.