New approach for the transformation of metallic waste into nanostructured Fe3O4 and SnO2-Fe3O4 heterostructure and their application in treatment of organic pollutant

Fabrication of novel three-dimensional Fe3O4-based particles electrodes with enhanced electrocatalytic activity for Berberine removal

Reasonable design of three-dimensional (3D) catalytic particle electrodes (CPEs) is crucial for achieving efficient electrocatalytic oxidation of organic pollutants. Herein, the novel Fe₃O₄/SnO₂/GO (FO/SO/GO) particle electrode has been developed and serviced to the 3D electrocatalytic berberine hydrochloride oxidation system with DSA (RuO₂-IrO₂-SnO₂/Ti) electrode as anode and GDE (gas diffusion electrode) electrode as the cathode. Compared with 2D systems and other CPEs, FO/SO/GO electrode shows excellent electrocatalytic activity and remarkable stability for BH removal, that is, the removal rate of BH is 94.8% within 90 min, and the rate constant is 0.03095 min^-1. More importantly, after five cycles, the ternary composite still maintains a strong ability to oxidize pollutants. The structural characterization and electrochemical measurement further uncover that the electron transfer ability and electrocatalytic oxidation efficiency are highly dependent on the surface structure regulation of CPEs. Furthermore, the quenching experiments show that hydroxyl radicals are the main active species in the 3D electro-Fenton (EF) system, which can oxidize BH molecules adsorbed on the surface of GO to CO₂, H₂O, or other products. The results could potentially provide new insights for designing and fabricating more stable and efficient 3D CPEs electrocatalytic removal of organic pollutants in the future.

Photocurable acrylate epoxy/ZnO–Ag nanocomposite coating: fabrication, mechanical and antibacterial properties

In this study, a UV-curable acrylate epoxy nanocomposite coating has been prepared by incorporation of ZnO–Ag hybrid nanoparticles. For this purpose, firstly ZnO–Ag hybrid nanoparticles were fabricated by a seed-mediated growth method. Then, these ZnO–Ag hybrid nanoparticles (2 wt%) were added into the UV-curable acrylate resin matrices. The photocuring process of nanocomposite was evaluated by various factors, such as the conversion of acrylate double bonds, pendulum hardness and gel fraction. Under the 4.8 s UV-exposure time for full crosslinking, the obtained data indicated that incorporation of ZnO–Ag nanohybrids into the coating matrix changed the crosslinking process of coating significantly. A mechanical teat indicated that the presence of nanohybrids in photocurable coating matrix enhanced its abrasion resistance from 98.7 to 131.6 L per mil (33.3%). The antibacterial test against E. coli over 7 h indicated that E. coli bacteria were killed totally by nanocomposite coating, whereas it was 2.6 × 10⁴ CFU mL⁻¹ for the neat coating without nanoparticles.

ZnO-Ag hybrid nanoparticles were fabricated by seed-mediated growth method and incorporated into the UV-curable acrylate resin matrice to form a composite. This improved the mechanical property of UV-cured coating and exhibited high antibacterial activity against E. coli.

Conversion of scrap iron into ultrafine α-Fe2O3 nanorods for the efficient visible light photodegradation of ciprofloxacin

The present study illustrates a feasible approach of utilizing scrap iron for the synthesis of iron(ii) oxide.

Surface photosensitization of ZnO by ZnS to enhance the photodegradation efficiency for organic pollutants

It is challenging to develop a material which has low cost, high activity, good stability and recyclability under light exposure. Apart from these properties, the photocatalyst should also have good visible region absorbance and low electron-hole pair recombination rate. Keeping all this in view, we have designed a simple scalable synthesis of ZnO–ZnS heterostructures for the photocatalytic treatment of industrial waste (p-nitrophenol and methyl orange). The ZnO–ZnS heterostructures are synthesized via a solvent-free route by thermal annealing of solid-state mixture of ZnO and thiourea (a sulphur source) which results in ZnO–ZnS core shell kind of heterostructure formation. The interface formation between the ZnO–ZnS heterostructure favored the band-gap reduction in comparison to the bare ZnO and ZnS nanoparticles. Further, these ZnO–ZnS heterostructures were utilized as a photocatalyst for the degradation of toxic phenolic molecules (p-nitrophenol) and harmful organic dyes (methyl orange) present in the water under the light exposure (> 390 nm).

Synthesis of TiO2 modified self-assembled honeycomb ZnO/SnO2 nanocomposites for exceptional photocatalytic degradation of 2,4-dichlorophenol and bisphenol A

In this study, we have successfully synthesized honeycomb-like self-assembled structure of TiO₂ modified ZnO/SnO₂ nanostructure via co-precipitation method with exceptional high degradation activities for 2,4-dichlorophenol (2,4-DCP) and bisphenol A (BPA) pollutants. The as-prepared samples were calcined in tube furnace at high elevated temperature (700, 800 and 900 °C) for 1 h. Among the TiO₂ modified samples, ZST10-700 showed higher charge separation as demonstrated from surface photovoltage spectroscopy, photoluminance and electrochemical curve. Surface morphology, crystallinity, optical property and different functional groups in the samples were determined with SEM, EDX, XRD, UV-Vis DRS and FTIR, respectively. Interestingly, 72% and 58% photocatalytic degradation efficiencies were achieved with optimized ZST10-700 for 2,4-DCP and BPA, respectively. In comparison, the pure ZS-700 only showed 36% and 29% photocatalytic degradation efficiencies, respectively. The improved photocatalytic degradation efficiencies of the optimized ZST10-700 are mainly due to improved charge separation and prolonged charge lifetime. It was further verified that by increasing calcination temperature, the photocatalytic activity decreased, and this is attributed to the formation of photo-inactive phases like Zn₂SnO₄ and ZnTiO₃. We believe that this work will provide an effective strategy to construct ternary heterojunction for the elimination of pollutants.

Green light-driven enhanced ammonia sensing at room temperature based on seed-mediated growth of gold-ferrosoferric oxide dumbbell-like heteronanostructures

Since there is excellent synergy between heterostructures and noble metals due to their unique electro-optical and catalytic properties, the introduction of noble metals into metal oxide semiconductors has substantially improved the performance of gas sensors. However, most of the reported noble metal-metal oxide composites are generally prepared as simple hybrids; hence, there is lack of control over their structure, morphology and dimension. Herein, we report a seed-mediated growth of dumbbell-like Au-Fe₃O₄ heteronanostructured gas sensors for ammonia detection under green light illumination, in which the particle sizes of Au and Fe₃O₄ were readily tuned in a wide range. The ammonia gas-sensing performances of Au-Fe₃O₄ heteronanostructures were greatly improved at room temperature by regulating their dimensions. In particular, the sensitivity improved by 30% while the response and recovery time shortened by 20 s and 50 s for the 7.5 nm Au-loaded Fe₃O₄-based sensor toward 5 ppm ammonia under 520 nm green light illumination as compared to that in the absence of light. This can be ascribed to the localized surface plasmon effect of Au and the Schottky junction formed at the interface between Au and Fe₃O₄. Interestingly, the Au-Fe₃O₄ heteronanostructure exhibits a unique p-type to n-type reversible transition for ammonia detection due to the nature of Fe₃O₄ NPs related to the trade-off between oxygen vacancies and electron transfer caused by ammonia adsorption. In addition, the calculation based on first-principle theory reveals enhanced adsorption capacities of Fe₃O₄ for ammonia after Au-doping.

Facilely synthesized cobalt doped hydroxyapatite as hydroxyl promoted peroxymonosulfate activator for degradation of Rhodamine B

Hydroxyapatite (HAP) is a promising supporter of catalyst due to its potential in immobilizing metals stably. HAP supported cobalt-based catalyst (Co-HAP) was synthesized via a facile ion exchange-calcination method to reduce the Co leaching. The synthesized Co-HAP was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET) analysis and X-ray photoelectron spectroscopy (XPS). Cobalt ions were incorporated into HAP structure and Co₃O₄ on HAP surface. Co-HAP showed satisfactory performance in peroxymonosulfate (PMS) activation for eliminating Rhodamine B (RhB) in aqueous solution. Co-HAP even revealed a better activity than that of CoFe₂O₄. •OH, SO₄^•- and ¹O₂ were all involved in RhB degradation and ¹O₂ played a leading role. High content of surface oxygen groups could be found on Co-HAP after RhB degradation, which might be resulted from the high amounts of hydroxyl groups. The presence of hydroxyl groups performed the co-catalytic activity of PMS activation in Co-HAP/PMS system.