Metal Oxide Nanostructures (MONs) as Photocatalysts for Ciprofloxacin Degradation

In recent years, organic pollutants have become a global problem due to their negative impact on human health and the environment. Photocatalysis is one of the most promising methods for the removal of organic pollutants from wastewater, and oxide semiconductor materials have proven to be among the best in this regard. This paper presents the evolution of the development of metal oxide nanostructures (MONs) as photocatalysts for ciprofloxacin degradation. It begins with an overview of the role of these materials in photocatalysis; then, it discusses methods of obtaining them. Then, a detailed review of the most important oxide semiconductors (ZnO, TiO₂, CuO, etc.) and alternatives for improving their photocatalytic performance is provided. Finally, a study of the degradation of ciprofloxacin in the presence of oxide semiconductor materials and the main factors affecting photocatalytic degradation is carried out. It is well known that antibiotics (in this case, ciprofloxacin) are toxic and non-biodegradable, which can pose a threat to the environment and human health. Antibiotic residues have several negative impacts, including antibiotic resistance and disruption of photosynthetic processes.

Biogenic Synthesis, Characterization and Antibacterial Potential Evaluation of Copper Oxide Nanoparticles Against Escherichia coli

The development of resistance against antibiotics used to treat bacterial infections along with the prevalence of medication residues presents significant public health problems globally. Antibiotic-resistant germs result in infections that are difficult or impossible to treat. Decreasing antibiotic effectiveness calls for rapid development of alternative antimicrobials. In this respect, nanoparticles (NPs) of copper oxide (CuO) manifest a latent and flexible inorganic nanostructure with noteworthy antimicrobial impact. Green synthesis of CuO NPs was performed in the current study, which was then doped with varying amounts of ginger (Zingiber officinale, ZO) and garlic (Allium sativum, AS) extracts. In low and high doses, the synthesized compound was used to measure the antimicrobial effectiveness against pathogenic Escherichia coli. The present research successfully demonstrated a renewable, eco-friendly synthesis technique with natural materials that is equally applicable to other green metal oxide NPs.

Theoretical and experimental study of the influence of PEG and PEI on copper electrodeposition

Through theoretical calculation and experimental research, the electrodeposition process of preparing copper catalyst in an acid electrolyte with polyethylene glycol (PEG) and polyethylene imine (PEI) as mixed additives is determined.

A novel 2D/1D core-shell heterostructures coupling MOF-derived iron oxides with ZnIn2S4 for enhanced photocatalytic activity

1D spindle-like iron oxides with controllable phase were synthesized by using MIL-88A-templated pyrolysis under different atmospheres, thermal annealing in N₂ to obtain Fe₃O₄ and in air to obtain α-Fe₂O₃. Then, 2D/1D core-shell heterostructures (ZnIn₂S₄@Fe₃O₄ and ZnIn₂S₄@α-Fe₂O₃) were constructed by in-situ self-assembly strategy. Characterizations indicated that the 2D ultra-thin ZnIn₂S₄ shell with 0.3 μm was homogeneously coated on the surface of 1D Fe₃O₄/α-Fe₂O₃ core with 1 μm, and ZnIn₂S₄@Fe₃O₄ exhibited higher BET surface area (84.5 m² g^-1) compared with ZnIn₂S₄@α-Fe₂O₃ (17.8 m² g^-1), providing more exposed active sites and larger contact area. The ZnIn₂S₄@Fe₃O₄-5 showed the best photocatalytic activity of RhB degradation as compared to ZnIn₂S₄, Fe₃O₄ and ZnIn₂S₄@α-Fe₂O₃. In addition, the degradation rates of MB, BPA and MO over ZnIn₂S₄@Fe₃O₄ were much higher than that of ZnIn₂S₄@α-Fe₂O₃. The proposed photocatalytic mechanism was also discussed: the Fe₃O₄ as an electron acceptor caused Fe³⁺/Fe²⁺ cycle in ZnIn₂S₄@Fe₃O₄ and ZnIn₂S₄@α-Fe₂O₃ followed the Z-scheme mechanism.

Hydrothermal Synthesis of Silver Decorated Reduced Graphene Oxide (rGO) Nanoflakes with Effective Photocatalytic Activity for Wastewater Treatment

Graphene oxide (GO) was obtained through modified hummers method, and reduced graphene oxide (rGO) was acquired by employing heat treatment. Various concentrations (2.5, 5, 7.5, and 10 wt. %) of silver (Ag) were incorporated in GO nanosheets by adopting hydrothermal approach. Synthesized Ag decorated rGO photocatalyst Ag/rGO was characterized using X-ray diffraction (XRD) to determine phase purity and crystal structure. XRD patterns showed the formation of GO to Ag/rGO. Molecular vibration and functional groups were determined through Fourier Transform Infrared spectroscopy (FTIR). Optical properties and a decrease in bandgap with insertion of Ag were confirmed with UV-Visible (Uv-Vis) spectrophotometer and photoluminescence (PL). Electronic properties and disorders in carbon structures were investigated through Raman spectroscopy that revealed the existence of characteristic bands (D and G). Surface morphology of prepared samples was examined with field emission scanning electron microscope (FESEM). Homogeneous distribution, size, and spherical shape of Ag NPs over rGO sheets were further confirmed with the help of high-resolution transmission electron microscope (HR-TEM). Dye degradation of doped and undoped samples was examined through Uv-Vis spectra. Experimental results indicated that photocatalytic activity of Ag@rGO enhanced with increased doping ratio owing to diminished electron-hole pair recombination. Therefore, it is suggested that Ag@rGO can be used as a beneficial and superior photocatalyst to clean environment and wastewater.

Active faceted Cu2O hollow nanospheres for unprecedented adsorption and visible-light degradation of pollutants

We report the well-designed active {1 1 0} and {1 1 1} faceted Cu₂O hollow nanospheres (Cu₂O-HNs) for the quick removal of the high concentration pollutants in water. For the first time, these Cu₂O-HNs combine the advantages of the active facets, hollow structure and nanostructures. The abundance of dangling Cu atoms in two active facets results in positively charged surface to effectively react with the negatively charged pollutants. The hollow structure provides the opportunity to take full use of these active sites. Consequently, the active faceted Cu₂O-HNs demonstrate excellent adsorption and photodegradation capacities for high concentrated anionic dyes. The smallest Cu₂O-HNs (~100 nm) can adsorb ~90% of methyl blue (MB) (100 mg L^-1) in 10 min and degrade ~92% of MB (100 mg L^-1) in 10 min under visible-light. In particular, a film consisting of the smallest Cu₂O-HNs can quickly remove high concentrated organic dyes and be reused after solar light irradiation for 10 min in air, showing the promising practical application for the removal of organic pollutants.

Two-way desorption coupling to enhance the conversion of syngas into aromatics by MnO/H-ZSM-5

We herein report a composite catalyst containing partially reducible and highly active manganese oxide and nano-size H-ZSM-5 with short b-axis, prepared for the direct conversion of syngas into aromatics.

Synchronous synthesis of Cu2O/Cu/rGO@carbon nanomaterials photocatalysts via the sodium alginate hydrogel template method for visible light photocatalytic degradation

A series of Cu₂O/Cu/rGO@carbon nanomaterial (Cu₂O/Cu/rGO@CN) heterogeneous photocatalysts were successfully synthesized synchronously via a novel sodium alginate hydrogel method. Cu₂O nanoparticles (~50nm) were synthesized by calcination under the protection of a nitrogen atmosphere. Cu nanoparticles (~6nm) inevitably appeared on the surface of Cu₂O, thereby forming a Cu₂O/Cu heterostructure which is known as a Schottky junction. Graphene oxide (GO) nanosheets were synchronously reduced in situ by sodium alginate during the synthesis process and eventually acted as a 3-D structure with the assistance of the hydrogel skeleton. Because of the 3-D rGO modification, both the adsorption capacity and the photocatalytic activity of Cu₂O/Cu/rGO@CN were significantly improved. The rate of p-nitrochlorobenzene (p-NCB) degradation catalyzed by Cu₂O/Cu/rGO@CN was ~1.97×10^-2min^-1, which was much higher than that of the degradation catalyzed by Cu₂O/Cu@CN (~0.239×10^-2min^-1). This result could be attributed to the two-stage Cu₂O/Cu/rGO heterostructure, which facilitated efficient electron-hole separation. This method has the advantages of nontoxic raw materials, facile synthesis and reduced auxiliary usage, providing a new technique for designing heterogeneous photocatalysts.

Rational design of yolk–shell nanostructures for photocatalysis

Yolk–shell structures provide an ideal platform for the rational regulation and effective utilization of charge carriers because of their void space and large surface areas. Furthermore, the efficiency of charge behavior in every step can be further improved by many strategies. This review describes the synthesis of yolk–shell structures and their effect for the enhancement of heterogeneous photocatalysis.

Fabrication of a kinetically sprayed CuO ultra-thin film to evaluate CO gas sensing parameters

We have introduced a new fabrication process for a CO gas sensor using a kinetically sprayed Cu thin layer, followed by oxidation at 250 °C.

A Template-Free Microwave Synthesis of One-Dimensional Cu₂O Nanowires with Desired Photocatalytic Property

One-dimensional Cu₂O nanowires were successfully prepared with a template-free microwave synthesis. Neither a surfactant was needed (to induce the growth), nor a long reaction time was required for this method. The structural investigation confirmed the successful preparation of Cu₂O. The morphology images showed that the radial size of the Cu₂O nanowires was 10 nm. The possible growth mechanism was hypothesized according to morphology evolution and references. A series of time-dependent experiments indicated that as time increased, Cu₂O primary particles grew radially into nanowires under microwave energy irradiation. The condition-variable tests revealed that the suitable quantity of NaOH played a vital role in Cu₂O nanowire formation. The photocatalytic property of the sample was investigated by degradation of methyl orange under the irradiation of visible light at room temperature. Benefiting from its unique large surface area, 4 mg of the prepared catalyst degraded 73% of methyl orange (10 mg L⁻¹) in 120 min.

Strong Electromagnetic Wave Response Derived from the Construction of Dielectric/Magnetic Media Heterostructure and Multiple Interfaces

A novel yolk-shell structure of cobalt nanoparticle embedded nanoporous carbon@carbonyl iron (Co/NPC@Void@CI) was synthesized via metal organic chemical vapor deposition (MOCVD) and subsequent calcination treatment. The in situ generation of void layer, which originated from the shrink of a Co-based zeolitic imidazolate framework (ZIF-67) during carbonization, embodies distinct advantage compared to the conventional template method. Thanks to the introduction of custom-designed dielectric/magnetic media heterostructure and multiple interfaces, the composites filled with 40 wt % of Co/NPC@Void@CI samples in paraffin exhibit a maximum reflection loss of -49.2 dB at 2.2 mm; importantly, a broad absorption bandwidth (RL < -10 dB) of 6.72 GHz can be obtained, which covers more than one-third of the whole frequency region from 10.56 to 17.28 GHz. This study not only develops the application of carbonyl iron as a high-efficiency light absorber but also initiates a fire-new avenue for artificially designed heterostructures with target functionalities.

Design and Synthesis of Cu@CuS Yolk-Shell Structures with Enhanced Photocatalytic Activity

Non-spherical Cu@CuS yolk-shell structures are successfully obtained using Cu₂O cube templates in a process combining rapid surface sulfidation followed by disproportionation of the Cu₂O core upon treatment with a hydrochloric acid solution. By employing the above method, Cu@CuS yolk-shell structures with different morphologies, including octahedral, truncated octahedral, and cuboctahedral shapes, can be synthesized. The void space within the hollow structures provides a unique confined space, where the metallic copper present in the core of a shell can be protected from agglomeration and oxidation. Furthermore, the presence of metal copper in these hollow structures contributes to improvement in the photocatalytic properties of these materials. The application of these Cu@CuS structures indeed shows clearly improved photocatalytic performance.

Hollow CuxO (x = 2, 1) micro/nanostructures: synthesis, fundamental properties and applications

In this review, we comprehensively summarize the important advances in hollow Cu_xO micro/nanostructures, including the universal synthesis strategies, the interfacial Cu–O atomic structures as well as the intrinsic properties, and potential applications. Remarks on emerging issues and promising research directions are also discussed.

Singlet oxygen formation in bio-inspired synthesis of a hollow Ag@AgBr photocatalyst for microbial and chemical decontamination

Singlet oxygen has been identified as a contributor to the degradation of contaminants using biosynthesised hollow Ag@AgBr catalysts.

Solution combustion synthesis and enhanced gas sensing properties of porous In2O3/ZnO heterostructures

Self-assembled porous In₂O₃/ZnO heterostructures are synthesized via a low temperature solution combustion method. An extremely high gas sensitivity can be reached when exposed to Cl₂ at 370 °C.

Polymer-Mediated Self-Assembly of TiO2@Cu2O Core-Shell Nanowire Array for Highly Efficient Photoelectrochemical Water Oxidation

Phototoelectrochemical (PEC) water splitting represents a highly promising strategy to convert solar energy to chemical energy in the form of hydrogen, but its performance is severely limited by the water oxidation reaction. We conformally grew an ultrathin and continuous coating of Cu2O on TiO2 nanowire array (NWA) to form a truly core-shell TiO2@Cu2O NWA via a new facile, economical, and scalable polymer-mediated self-assembly approach, in which the polymer serves as a stabilizer, reductant, and linker simultaneously. This heteronanostructure was subsequently directly used as a photoanode for PEC water splitting, showing a photocurrent density of 4.66 mA cm(-2) at 1.23 V vs RHE in 0.5 M Na2SO4 solution and a maximum photoconversion efficiency of 0.71%, both of which are the highest reported for TiO2-based photoanodes measured under the same conditions (neutral conditions and without any sacrificial agent). The superior PEC performance of the TiO2@Cu2O NWA toward water oxidation is primarily due to much enhanced visible light collection and charge separation for high charge carrier density as well as greatly facilitated charge transfer and transport. This work not only offers a novel TiO2@Cu2O core-shell NWA photoanode for highly efficient PEC water oxidation and investigate its enhancement mechanism but also provides scientific insights into the mechanism of the polymer-mediated self-assembly, which can be further extended to fabricate various other core-shell nanoarchitectures for broad applications.

Hierarchical heterostructures based on prickly Ni nanowires/Cu2O nanoparticles with enhanced photocatalytic activity

Metal-semiconductor-based photocatalysts show high efficiencies and catalytic activities in the photocatalysis process.

Synthesis and applications of porous non-silica metal oxide submicrospheres

A variety of metal oxide particles of spherical morphology from nano to micrometer size have been reviewed with a special emphasis on the appraisal of synthetic strategies and applications in biomedical, environmental and energy-related areas.

Controlling core/shell formation of Nanocubic p-Cu2O/n-ZnO toward enhanced photocatalytic performance

p-Type Cu2O/n-type ZnO core/shell photocatalysts has been demonstrated to be an efficient photocatalyst as a result of their interfacial structure tendency to reduce the recombination rate of photogenerated electron-hole pairs. Monodispersed Cu2O nanocubes were synthesized and functioned as the core, on which ZnO nanoparticles were coated as the shells having varying morphologies. The evenly distributed ZnO decoration as well as assembled nanospheres of ZnO were carried out by changing the molar concentration ratio of Zn/Cu. The results indicate that the photocatalytic performance is initially increased, owing to formation of small ZnO nanoparticles and production of efficient p-n junction heterostructures. However, with increasing Zn concentration, the decorated ZnO nanoparticles tend to form large spherical assemblies resulting in decreased photocatalytic activity due to the interparticle recombination between the agglomerated ZnO nanoparticles. Therefore, photocatalytic activity of Cu2O/ZnO heterostructures can be optimized by controlling the assembly and morphology of the ZnO shell.

Assembly synthesis of Cu2O-on-Cu nanowires with visible-light-enhanced photocatalytic activity

The designed visible-light-driven Cu₂O-on-Cu nanowire photocatalysts exhibit high-performance catalytic degradation of dye pollutants, suggesting potential applications in aquatic environments.