Functional Materials Letters

Spin-coated poly (vinylidene fluoride) (PVDF) membrane and electrospun PVDF nanofibers were fabricated and surface modified with in-situ self-polymerization of dopamine or surface deposition of polydopamine. The morphology, composition and phase, hydrophilicity and dye degradation effects of these composite were quantitatively investigated. The results indicated that surface modified PVDF membrane and nanofibers exhibited excellent dye degradation capacity. Specifically, in-situ self-polymerization of dopamine could induce homogeneous distribution of polydopamine on the piezo-catalysis materials, providing favorable spatial conditions for the adsorption of dye molecules and enhancing dye degradation.

Novel Pt/ZrSn${}_{1-x}$Sr${}_x$O${}_{4-\delta }$/SBA-16 (SBA-16: Santa Barbara Amorphous No. 16) catalysts were developed for liquid-phase phenol oxidation. As the promoter to accelerate phenol oxidation on Pt, a ZrSnO₄ solid with an $\alpha$-PbO₂-type structure was chosen because its interstitial open spaces are expected to facilitate phenol adsorption. Additionally, the redox reaction of Sn${}^{4+/2+}$ provides oxygen release and storage abilities, and the introduction of low-valent Sr${}^{2+}$ ions into the ZrSnO₄ lattice improves oxide ion migration via the generation of oxygen vacancies in the lattice structure. Among the samples prepared, the 9.0 wt.% Pt/8.1 wt.% Zr${}_{1.11}$Sn${}_{0.85}$Sr${}_{0.04}$O${}_{4-}$${}_{\delta }$/SBA-16 catalyst showed the highest activity, resulting in a phenol removal percentage of up to 99.7% after 6 h of reaction at 80${}^{\circ }$C under atmospheric pressure.

Handwriting recognition has been widely studied as an important signal transmission method in the field of human–computer interaction. Flexible capacitive three-dimensional (3D) force sensor is widely used in this field because of its high sensitivity, large dynamic response range and good mechanical stability. However, traditional flexible capacitive 3D force sensors based on the array structure usually only sense 3D force with equivalent forward pressure rather than the decoupling of real 3D force in space. Herein, we design a flexible capacitive 3D force sensor with petal-like electrode to capture various hand movements in 3D space and further decouple 3D force to 1D force along $X$, $Y$ and $Z$ directions. The sensor presents a high sensitivity (1.1 kPa${}^{-1}$at the pressures below 1 kPa), a fast response (63 ms) and excellent repeatability under continuous pressure. In addition, the electrode with eight-petal structure helps simplify the decoupling process of 3D force. Through handwriting test, the sensor presents good sensing performance for hand motion capture and handwriting recognition, which is expected to be applied in the field of human–computer interaction.

The preparation of N-doped TiO₂ with excellent photocatalytic performance is reported. The study of the synthesis process involves the control of N-doping and the crystalline phase. The incorporation of urea provides dual features; it introduces a nitrogen source and also reduces the phase transition temperature of anatase to rutile. The optimal N-doped catalyst that possesses both anatase and rutile phases shows excellent catalytic efficiency in the degradation of ciprofloxacin under illumination by visible light and sunlight.

Implementing bottom-up approaches to control the columnar architecture of thin films at the nanoscale is a powerful tool for developing surface properties. While inclined columns, zigzags or helices made of a single material are now commonly produced by oblique angle deposition processes, the creation of more complex and original structures associating at least two different materials still remains a challenging task, even more on silicon substrate. Herein, we show how to prepare tungsten/molybdenum columns exhibiting a checkerboard-like structure with motifs of a few tens of nanometers. Although understanding the growth phenomena becomes more problematic when two components are simultaneously provided during the film fabrication, this original combination of controlled mosaics in columnar thin films enables new opportunities to produce some unusual nanostructures for functional materials.

Cubic Zn₂TiO₄ films were deposited on MgO (111) single crystal substrates using pulsed laser deposition (PLD). With the assistance of post-annealing process, the best epitaxial Zn₂TiO₄ film with only (111) single plane was obtained at 950${}^{\circ }$C. For the best Zn₂TiO₄ single crystalline film, the full width at half maximum (FWHM) of the XRD $\omega$ rocking curve for the Zn₂TiO₄ (111) diffraction peak was only 0.12${}^{\circ }$. From the TEM spectrum, the film had a regular lattice arrangement and strong periodicity. Structural analysis indicated that the out-plane and in-plane epitaxial arrangement of the film/substrate separately were Zn₂TiO₄ (111)//MgO (111) and Zn₂TiO4 [10$\overline{1}$]//MgO <10$\overline{1}$>. The optical properties of the films were investigated in detail. After removing the influence of the transmittance of the substrate, the relative transmittance of the films exceeded 90% and the optical band gap of the films varied between 3.84 and 4.38 eV.

In this study, a novel lanthanum oxide-loaded porous mullite–corundum ceramic was prepared and adopted to remove Cr(VI) from aqueous solution. The lanthanum oxide-loaded porous mullite–corundum ceramic was characterized by XRD, SEM-EDS, and XPS, and batch adsorption experiments were employed to investigate the effect of main interfering factors on Cr(VI) adsorption. The results showed that the adsorption capacity of lanthanum oxide-loaded porous mullite–corundum ceramic was significantly improved, and the dynamic adsorption equilibrium could be reached at 720 min; the adsorption capacity almost did not decrease after five adsorption cycles. Cr(VI) adsorption process abided by pseudo-second-order kinetic model and Freundlich model, indicating that Cr(VI) adsorption onto lanthanum oxide-loaded porous mullite–corundum ceramic was multi-molecular layer chemical adsorption. Therefore, lanthanum oxide- loaded porous ceramics are an efficient and highly reusable adsorbent, which is expected to be used for the treatment of Cr(VI) in wastewater.

Sn–ZnO nanorod array coatings with a low concentration of tin dioxide (0, 0.5, 1, 5 mol.%) were obtained by hydrothermal method on glass or polycore substrates. The synthesized materials are crystallized in the wurtzite structure, which was confirmed by X-ray diffraction analysis. According to scanning electron microscopy arrays of nanorods have an average length 120–180 nm and a diameter of 57–77 nm. It was established that an increase in the temperature of hydrothermal synthesis (from 95${}^{\circ }$C to 200${}^{\circ }$C) leads to a decrease in particle sizes of pure ZnO. All obtained materials have photocatalytic activity in the visible light range. The best photocatalytic activity — 82% degradation of methylene blue in 3 h of visible light irradiation — was shown for material containing 1 mol.% of tin dioxide. This hydrothermal method opens a new pathway for developing new nanostructured photocatalysts.

Silver-doped zinc oxide nanoparticles (NPs) were synthesized employing a facile hydrothermal method supported by the seaweed Turbinaria ornata (TO). TO extract was used as a capping agent. The prepared NPs were accounted for using instrumentational analysis such as FE-SEM, EDS, XRD, FTIR, and UV-Vis. Their characteristic study showed an average size of 26 nm with 81% crystallinity with X-ray Diffraction and the band-gap value as 3.25 eV. The biosynthesized doped particle exhibited rod-shaped morphology for better efficiency in dye degradation of Methylene Blue (MB) dye. They were also tested for adsorption kinetics and photocatalytic degradation of MB using sunlight. The efficiency in degrading the MB dye proclaimed a remarkable change in solar irradiation of about 90% reduction to visible light, which leads to the betterment in solar degradation of dye pollutants at a minimal cost.

Although nickel-based phosphides as a promising category of electrode materials in supercapacitors have high intrinsic electrical conductivity, they still present unsatisfied electrochemical performance and cycling life so far, which is mostly attributed to the low-surface area or inappropriate microstructure. Therefore, constructing a microstructure that meets the requirements of supercapacitors is the key for improving the performance of nickel-based phosphides. In this work, we prepared the cobalt ions-doped Ni₂P with a nanosheets-self-supported nanostructure by phosphating its precursor of cobalt ions-doped nickel hydroxynitrate. Ascribed to appropriate microstructure and elevated electrical conductivity, the cobalt ions-doped Ni₂P exhibits high electrochemical and cycling performance. The cobalt ions-doped Ni₂P not only shows high specific capacity of 1150.0 C g${}^{-1}$ at the low current density 2.5 A g${}^{-1}$, but also exhibits excellent high-rate performance about the capacity retention of 53% at high current density of 49.1 A g¹, attributed to its nanosheet morphology and elevated electrical conductivity. By virtue of the nanosheets-self-supported structure, the cobalt ions-doped Ni₂P also shows high cycling performance on capacity retention of 81% for 10,000 charge-discharge cycles. The high performance of cobalt ions-doped Ni₂P obtained from electrochemical measurement confirms its prospect as a candidate electrode material for advanced application in supercapacitors.