In the past few decades, many novel non-metal doped ZnO materials have developed hasty interest due to their adaptable properties such as low recombination rate and high activity under the solar light exposure. In this article, we compiled recent research advances in non-metal (S, N, C) doped ZnO, emphasizing on the related mechanism of catalysis and the effect of non-metals on structural, morphological, optical and photocatalytic characteristics of ZnO. This review will enhance the knowledge about the advancement in ZnO and will help in synthesizing new ZnO-based materials with modified structural and photocatalytic properties.
Graphene is a remarkable material with great potential in many applications due to its chemical and physical properties. In this review we briefly present the recent research progress (2016–2018) in graphene and graphene-based nanomaterials synthesis and discuss the practical aspects of using the materials produced via these methods for different graphene-based applications.
A simple approach to synthesize ZnO microstructures was reported using dodecylamine, hexadecylamine and oleylamine as template agents. The synthesized ZnO was characterized by XRD, FESEM, TEM, EDS mapping, FTIR, UV–vis DRS, Raman spectroscopy and BET analysis. Hierarchical oriented ZnO microstructures were obtained. The photocatalytic performance of ZnO prepared with different types of alkylamines was evaluated by the degradation of methylene blue (MB) and methyl orange (MO). The results suggested that alkylamine control the nucleation, growth and morphology of ZnO. The photocatalytic properties of ZnO on the degradation of MB and MO decreased with increasing the alkyl chain length in alkylamine.
ZnO nanocone arrays (NCAs) decorated with black TiO2 nanoparticles (B-TiO2 NPs) were uniformly anchored on the surface of carbon cloth (CC) directly by a simply electrochemical deposition method. Thus a novel B-TiO2 NPs/ZnO NCAs–CC hierarchical heterostructure was formed. It displayed superior performance and achieved a higher photocurrent over 0.4 mA·cm−2 before the onset of the dark current, attributed to the separation of the photogenerated electron–hole pair. Based on the B-TiO2 NPs/ZnO NCAs–CC heterostructure, the catalyst was fabricated for promoting the separation of charge carriers. Moreover, the introduction of Ti3+ and oxygen vacancies on the surface of TiO2 NPs expanded the absorption band edge and enhanced the electrical conductivity as well as the charge transportation on the catalytic surface. It indicates that the B-TiO2 NPs/ZnO NCAs–CC composite is beneficial to the improvement of the photoelectrochemical (PEC) activity.
A polyacrylic acid (PAA)/gelatin (Gela)/polyvinyl alcohol (PVA) hydrogel was prepared by copolymerization, cooling, and freezing/thawing methods. This triple-network (TN) structure hydrogel displayed superior mechanical properties, low swelling ratio and self-healing properties. The superior mechanical properties are attributed to the triple helix association of Gela and PVA crystallites by reversible hydrogen bonding. The characterization results indicated that the fracture stress and the strain were 808 kPa and 370% respectively, while the compression strength could reach 4443 kPa and the compressive modulus was up to 39 MPa under the deformation of 90%. The hydrogen bonding in PVA contributed to maintain and improve the self-healing ability of hydrogels. Every type of hydrogels exhibited a higher swelling ratio under alkaline conditions, and the swelling ratios of PAA, PAA/PVA and PAA/Gela hydrogels were 27.71, 12.30 and 9.09, respectively. The PAA/Gela/PVA TN hydrogel showed the lowest swelling ratio (6.57) among these hydrogels. These results indicate that the novel TN hydrogels possess good environmental adaptability and have potential applications in the biomedical engineering and sensor field.
A series of flexible poly(m-phenylene isophthalamide) (PMIA)-based composites with different sizes and mass fractions of hexagonal boron nitride (hBN) were successfully manufactured for the first time via the casting technique. The effects of modified hBN particles on microstructure, mechanical properties, dielectric properties and thermal conductivities of fabricated composites were investigated. The results indicate that modified hBN particles manifest good compatibility with the PMIA matrix. The Young’s modulus and Theat-resistance index of PMIA-based composites are increased with increasing the mass fraction of hBN particles. Due to additional thermal conductive paths and networks formed by nano-sized hBN particles, the K-m/n-hBN-30 composite displays the thermal conductivity of 0.94 W·m−1·K−1, higher than that of the K-m-hBN-30 composite (0.86 W·m−1·K−1), and more than 4 times higher than that of neat PMIA. Moreover, the obtained PMIA-based composites also show low dielectric constant and ideal dielectric loss. Owing to the excellent comprehensive performance, hBN/PMIA composites present potential applications in the broad field of electronic materials.
The yolk–shell LaMnO3 perovskite microspheres were fabricated by a novel, simple and mild soft template approach. A series of template-P123 concentrations (0–6.12 mmol∙L−1) were employed to optimize the most complete spheres. When the concentration of P123 is 3.0 mmol·L−1, the obtained yolk–shell microspheres with a diameter of 200–700 nm were constructed by nanoparticles. The possible formation mechanism of the yolk–shell microspheres was revealed step by step via XRD, SEM, TEM, EDS and HRTEM. Molecules of P123 were suitably mixed with solvents for double shelled vesicles through self-assembly, which interacted with metal complexes to form P123–metal vesicles. After the removal of P123 and citric acid by calcination at 700 °C, the yolk–shell LaMnO3 microspheres with through-channels were obtained. Through-channels on the surface were due to citric acid and the solid core was attributed to the shrink of inner vesicles. Prepared yolk–shell microsphere samples possessed a larger surface area and a higher maximum NO conversion value of 78% at 314 °C for NO oxidation, compared with samples without the yolk–shell structure.
Magnesium (Mg) alloys have attracted considerable research attention as potential biocompatible implant materials. However, the major barriers to the extended use of such medical devices are the possibility of high corrosion rate and implant-associated infections. To solve them, a novel polyacrylic acid (PAA)/gentamicin sulfate (GS)-hydroxyapatite (HAp) coating was synthesized by a one-step hydrothermal deposition method. Characteristics of functional coatings were investigated by SEM, FTIR and XRD. Corrosion properties of samples were evaluated by electrochemical and hydrogen evolution tests. Antibacterial activities of the coatings against Staphylococcus aureus (S. aureus) were measured by the plate-counting method. Results showed that the as-prepared HAp coating with dense and flawless morphologies could not only enhance the corrosion resistance of Mg alloys, but also improve the adhesion strength between the HAp coating and the substrate. In addition, the induction of the apatite coating during immersion confirmed the excellent mineralization ability of the HAp coating. Moreover, the obtained HAp coating possessed antibacterial properties and could prolong the release of GS. Thus, the PAA/GS-HAp coated Mg alloy could serve as a better candidate for biomedical applications with good anti-corrosion and antibacterial properties.
Er3+-doped SrBi4Ti4O15–Bi4Ti3O12 (SBT–BIT–xEr3+, x = 0.00, 0.05, 0.10, 0.15 and 0.20) inter-growth ceramics were synthesized by the solid-state reaction method. Structural, electrical and up-conversion properties of SBT–BIT–xEr3+ were investigated. All samples showed a single phase of the orthorhombic structure. Raman spectroscopy indicated that the Er3+ substitution for Bi3+ at A sites of the pseudo-perovskite layer increases the lattice distortion of SBT–BIT–xEr3+ ceramics. The substitution of Bi3+ by Er3+ leads to a decrease of dielectric loss tanδ and an increase of conductivity activation energy. Piezoelectric constant d33 was slightly improved, but dielectric constant was decreased with the Er3+ doping. The SBT–BIT–xEr3+ ceramic with x = 0.15 exhibits the optimized electrical behavior (d33 ~17 pC/N, tanδ ~0.83%). Moreover, two bright green (532 and 548 nm) and one red (670 nm) emission bands were observed under the 980 nm excitation. Optimized emission intensity was also obtained when x = 0.15 for the SBT–BIT–xEr3+ ceramic. Therefore, this kind of ceramics ought to be promising candidates for multifunctional optoelectronic applications.