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Directional motion in response to specific signals is critically important for micro/nanomotors in precise cargo transport, obstacle avoidance, collective control, and complex maneuvers. In this work, a kind of isotropic light-driven micromotor that is made of hedgehog-shaped TiO2 and functional multiwall carbon nanotubes (Hs-TiO2@FCNTs) has been developed. The FCNTs are closely entangled with Hs-TiO2 and form a close-knit matrix on the surface of Hs-TiO2, which facilitates the transfer of electrons from Hs-TiO2 to FCNTs. Due to the high redox potential of Hs-TiO2, excellent electron-hole separation efficiency by the addition of FCNTs, and isotropic morphology of the micromotor, these Hs-TiO2@FCNT micromotors show phototactic and fuel-free propulsion under unidirectional irradiation of UV light. It is the first time to demonstrate isotropic micromotors that are propelled by self-electrophoresis. The isotropy of Hs-TiO2@FCNT micromotors makes them immune to the rotational Brownian diffusion and local flows, exhibiting superior directionality. The motion direction of our micromotors can be precisely tuned by light and a velocity of 8.9 μm/s is achieved under 160 mW/cm2 UV light illumination. Photodegradation of methylene blue and active transportation of polystyrene beads are demonstrated for a proof-of-concept application of our micromotors. The isotropic design of the Hs-TiO2@FCNT micromotors with enhanced photocatalytic properties unfolds a new paradigm for addressing the limitations of directionality control and chemical fuels in the current asymmetric light-driven micromotors.

Transition metal orthovanadates are emerging 2D materials for promising electrochemical energy storage applications. Facile hydrothermal method for nanocrystalline indium vanadate (InVO4) semiconducting materials’ fabrication is economical because of its direct chemical synthesis. X‐ray diffraction studies, field emission scanning electron microscope (SEM) images, transmission electron microscopy (TEM), and photoelectron X‐ray spectrum are used to describe the semiconductor materials as synthesized. InVO4 microspheres have attracted a lot of attention in the energy and environmental sector. These microsphere‐derived semiconductor materials are recognized to offer the advantages of their large surface area, tunable pore sizes, enhanced light absorption, efficient carrier (electron–hole) separation, superior electronic and optical behavior, and high durability. From the results of SEM and TEM, InVO4 shows a microsphere construction with a mixture of nanosized particles. Diffuse reflectance UV–visible measurements are used to determine the bandgap, and it is found to be 2.1 eV for InVO4. The electrochemical analysis reveals a superior performance of the pseudocapacitor with hydrothermally derived microspheres of InVO4. Alongside an improved pseudocapacity, developed after 4000 cycles, it has excellent cycling stability with a retention of ≈94% of its original specific capacitance efficiency., A simple hydrothermal method is utilized to synthesize InVO4 and InVO4–SiO2 nanostructures. InVO4 exhibits typical hierarchical morphology with a superior electrochemical performance of 1710 F g−1 at 2 A g−1. Also, encapsulation of SiO2 on InVO4 provides an added potential in energy storage applications. A stability retention of ≈91% pseudocapacitance is achieved after 4000 cycles for InVO4.

A metal doped coupled semiconductor oxide, Ag–ZnO–CdO was fabricated by a simple co-precipitation method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), elemental mapping, high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area measurement, UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). XRD and EDS reveal the presence of CdO and metallic Ag in the catalyst. FESEM shows a mixture of hexagonal nanosheets, nanoclusters and nanoparticles with a large number of cavities. HR-SEM and TEM images of the catalyst show that ZnO particles have pentagonal or hexagonal plate-like structure. Cadmium oxide and silver clusters are formed on the clear smooth surface of ZnO. Ag–ZnO–CdO has increased absorption in the UV and Visible region when compared to ZnO. This three component nanojunction system exhibited enhanced photocatalytic activity for the degradation of acid black 1 (AB 1) and acid violet 7 (AV 7) under sunlight far exceeding those of the single and two component systems. Ag–ZnO–CdO was found to be stable and reusable without appreciable loss of catalytic activity up to five runs. This metal doped coupled oxide shows increased hydrophobicity, when compared to CdO or ZnO. Our results provide new insights of the performance of a solar active photocatalyst with self-cleaning properties.

The development of coupled semiconductor photocatalysts makes a significant advancement in catalytic functional materials. A new heterostructured Bi2O3–ZnO, synthesized by a simple hydrothermal–thermal decomposition method, exhibited higher photocatalytic activity for the degradation of Acid Black 1 (AB 1) under UV light than pure ZnO, Bi2O3, and commercial Degussa P25. X-ray powder diffraction analysis reveals that the as-synthesized product has the monoclinic lattice phase of Bi2O3 and the hexagonal wurtzite phase of ZnO. HR-SEM images show that Bi2O3–ZnO has an ordered mixture of nanofiber and nanochain structures. This heterostructured Bi2O3–ZnO has increased UV absorption when compared with ZnO. The enhanced photocatalytic activity of Bi2O3–ZnO is attributed to the low recombination rates of photoinduced electron–hole pairs, caused by the vectorial transfer of electrons and holes between ZnO and Bi2O3. Higher efficiency at neutral pH 7 and reusability in the degradation of AB 1 makes Bi2O3–ZnO, a pro...

In this article, we report the fabrication of a stable Ag-ZnO-SnO2 nanochain by template free hydrothermal method and its photocatalytic activity for the first time. This composite material represents a potential new class of photocatalysts with enhanced light absorption, hydrophobic and electronic properties of ZnO. This catalyst has been characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), field emission scanning electron microscopy (FESEM), elemental mapping, energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). XRD and elemental mapping reveal the presence of SnO2 and Ag in the catalyst. Ag-ZnO-SnO2 has increased absorption in the visible region when compared to ZnO. This three component nano junction system exhibits enhanced photocatalytic activity for the degradation of azo dyes, Acid Black 1 (AB 1) and Acid Violet 7 (AV 7) under UV light (365 nm), far exceeding those of the single and two component systems. Ag-ZnO-SnO2 is found to be reusable without appreciable loss of catalytic activity up to four runs. Based on the band gap energies of ZnO and SnO2, a mechanism is proposed for the photodegradation of dyes. Hydrophobicity and photoconductivity of Ag-ZnO-SnO2 have been evaluated. Nanochain exhibiting higher positive photoconductivity can be useful for soliton wave communication as well as solar cell applications. Our results provide some new insights on the fabrication of Ag-ZnO-SnO2 and its performance as an active photocatalyst, self cleaning and conducting material.