Affinity Barrier Research Articles

Surface and interface engineering of Z-scheme 1D/2D imprinted CoZn-LDH/C3N4 nanorods for boosting selective visible-light photocatalytic activity

Recently, the emergence of more and more coexisting organic contaminants aggravates the difficulty of water treatment and poses a threat to public health. Molecularly imprinted photocatalysts allow a highly selective removal of target active compounds, rendering wide applications in complex environmental treatment. However, the synergistic recognition and degradation performance is usually restricted by the intrinsic structural characteristics of traditional photocatalysts and the affinity barrier between semiconductor substrate and organic imprinted layer. Herein, we synthesized Z-scheme molecularly imprinted photocatalysts with CoZn-LDH heterostructure supported by porous C3N4 nanorods (MIP-CoZn-LDH@C3N4). Due to the excellent light capture and high active cavities, the photodegradation rate of MIP-CoZn-LDH@C3N4 to tetracycline (TC) target could reach 79.8% under visible light within 60 min. Noticeably, the material possessed outstanding ability of selective recognition and photodegradation of TC in coexisting interference solution (kimprinted was 2.18 to ciprofloxacin and 2.33 to cephalothin, respectively). The mode of selective photodegradation and pathways were systematically discussed based on the deep evaluation of the mechanism experiments. Our study opens a new insight into the design of photocatalyst with selective degradation performance for the requirements of practical environmental applications.

An XPS and SEMS study of silica sol‐gel/metal substrate interaction

AbstractSome applications of ceramic materials are difficult because of the markedly differing lattice bonding characteristics of ceramic and metals. This ‘affinity barrier’ can be overcome by the modifying of structure and composition in the interphase region. In our work the silica sublayer was deposited by the sol‐gel method on metal implants prior to electrophoretical deposition of hydroxyapatite coatings to improve the oxidation resistance of the metal surface and the adhesion of apatite to metal during the annealing. The aim of this study is to determine changes in chemical state and structure of the coatings caused by thermal treatment for the better understanding of a relation between their composition and properties. Plates of titanium, WT 1‐0, FeCrNi stainless steel and of low‐carbon steel were covered with silica layer by the sol‐gel method. The coating on low‐carbon steel was produced by the deposition of silica sol‐gel directly on the metal or, the silica–titania opacified porcelain enamel was obtained by electrophoresis. In the case of direct deposition, below 400 °C, an amorphous layer was formed while at 800–900 °C for only 2‐4 min the dense, fine crystalline structure was obtained including small amount of silicates and iron scales. The silica–titania enamel was electrophoretically applied on low‐carbon steel pre‐coated with nickel. During annealing nickel is alloyed with iron and decreases oxygen transport towards iron decreasing the rate of FeO formation. The silica from the enamel reacts with FeO producing a small amount of silicates. Titania partially precipitates at the metal boundary in the form of the needle‐like crystals of FeTiO3, growing from the steel surface into the enamel. When stainless steel was annealed at 700 °C in air, the surface oxide was enriched in chromium and manganese while the silica surface was enriched in iron and manganese.