Visible light-induced photo-degradation of methylene blue by n–p heterojunction CeO2/CuS composite based on ribbon-like CeO2 nanofibers via electrospinning

Optical Properties of Electrospun Nanofiber Mats

Electrospun nanofiber mats are usually applied in fields where their high specific surface area and small pore sizes are important, such as biotechnology or filtration. Optically, they are mostly white due to scattering from the irregularly distributed, thin nanofibers. Nevertheless, their optical properties can be modified and become highly important for different applications, e.g., in sensing devices or solar cells, and sometimes for investigating their electronic or mechanical properties. This review gives an overview of typical optical properties of electrospun nanofiber mats, such as absorption and transmission, fluorescence and phosphorescence, scattering, polarized emission, dyeing and bathochromic shift as well as the correlation with dielectric constants and the extinction coefficient, showing which effects may occur and can be measured by which instruments or used for different applications.

ZnO/CeO2 Nanocomposites: Metal-Organic Framework-Mediated Synthesis, Characterization, and Estimation of Cellular Toxicity toward Liver Cancer Cells

The Zinc-doped cerium oxide nanocomposite (ZnO/CeO₂ NC) was synthesized using a metal-organic framework as a precursor through the combustion method. It was characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), field emission electron microscopy (FESEM), energy dispersive analysis (EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS), and ξ-potential. The PXRD demonstrated the successful synthesis of ZnO/CeO₂ NC with a crystallite size of 31.9 nm. FESEM and TEM images displayed hexagonal and spherical morphologies, and the solid-phase size was 65.03 ± 30.86 nm for ZnO/CeO₂ NCs. DLS, TEM, and FESEM showed that the NCs have a high tendency for agglomeration/aggregation in both aqueous media and solid phase. The anticancer attributes of ZnO/CeO₂ NC were investigated against Liver cancer cells (HepG2), which showed inhibition of cancer cell growth on a concentration-dependent gradient. The cell toxicity effects of ZnO/CeO₂ nanocomposites were also studied toward NIH-3T3, in which the data displayed the lower toxicity of NC compared to the HepG2 cell line.

Electrospun 1D-NiO hollow nanowires on glass support for the sunlight-driven photodegradation of methylene blue

Sunlight-driven semiconductor photocatalysts have received substantial attention due to environmental degradation, but a simple and reusable photocatalyst design has been a challenging task. Herein, we report the fabrication of a one-dimensional hollow semiconducting nanowire structure by electrospun-mediated nickel oxide nanowires (NiO NWs) as a reusable photocatalyst by direct deposition on glass substrates. The effective control of the sunlight-driven hollow nanowires as the photocatalyst has a high surface area for multiple light-harvesting and interface redox reactions, a nanostructured thin shell for accelerated charge separation, transportation, and a large length-diameter ratio for easy recycling. The electrospun NiO NWs were nest-like hollow nanostructure fibers, crystalline, and with a high density, and the synthesis and parameters were thoroughly investigated to achieve the characteristic shape of the hollow NiO NWs. Further, the photocatalytic activity of the NiO NWs on glass substrates for the selective breakdown of methylene blue (MB) under sunlight irradiation to optimize the efficiency of the NiO NWs, such as degradation techniques, concentration, and pH of the MB solution. The stability and reusability of the NiO NWs were tested successfully in several reusable cycles, with only a 2% degradation difference. The reaction rate was found to be 0.054 min⁻¹ for MB (5 μM) and 0.033 min⁻¹ for MB (10 μM) at pH 11 for 60 min, and the higher activity parameter was calculated to be 3.3 × 10⁻³ min⁻¹ mg⁻¹ L⁻¹ due to their hollow structure and effective area of the NiO NWs. They contain more superficially-entrapped holes that change with chemisorbed oxyhydroxyl OH or H₂O to form OH⁻ radicals. The specific active hollow surface area rises, whereas the rate of optical-electronic hole recombination drops. The photocatalytic degradation performance of the fabricated one-step electrospun hollow NiO NW-based photocatalyst on substrates showed speed, reusability, and promoted the formation of radicals capable of decomposing organic pollutants, which were shown to have application in photocatalysis.

One-step fabrication of hollow NiO NWs photocatalyst on glass substrate by electrospun then tested for their capacity to break down MB in solutions exposed to sunlight.

MOF-Mediated Synthesis of CuO/CeO2 Composite Nanoparticles: Characterization and Estimation of the Cellular Toxicity against Breast Cancer Cell Line (MCF-7)

A copper oxide/cerium oxide nanocomposite (CuO/CeO₂, NC) was synthesized via a novel method using a metal–organic framework as a precursor. This nanomaterial was characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), dynamic light scattering size analysis (DLS), and zeta potential. The PXRD showed the successful synthesis of the CuO/CeO₂ NC, in which the 2theta values of 35.55° (d = 2.52 Å, 100%) and 38.73° (d = 2.32 Å, 96%) revealed the existence of copper (II) oxide. FTIR analysis showed the CeO₂, hydroxyl groups, absorbed water, and some residual peaks. The solid phase analysis by FESEM and TEM images showed mean particle sizes of 49.18 ± 24.50 nm and 30.58 ± 26.40 nm, respectively, which were comparable with crystallite size (38.4 nm) obtained from PXRD, but it appears the CuO/CeO₂ NC was not evenly distributed and in some areas, showed it was highly agglomerated. The hydrodynamic size (750.5 nm) also showed the agglomeration of the CuO/CeO₂ NCs in the solution, which had a negatively charged surface. The CuO/CeO₂ NCs showed anti-proliferative activity against human breast cancer cell line (MCF-7) in a dose- and time-dependence way, while affecting normal cells less significantly.

Transition metal sulfides meet electrospinning: versatile synthesis, distinct properties and prospective applications

One-dimensional (1D) electrospun nanomaterials have attracted significant attention due to their unique structures and outstanding chemical and physical properties such as large specific surface area, distinct electronic and mass transport, and mechanical flexibility. Over the past years, the integration of metal sulfides with electrospun nanomaterials has emerged as an exciting research topic owing to the synergistic effects between the two components, leading to novel and interesting properties in energy, optics and catalysis research fields for example. In this review, we focus on the recent development of the preparation of electrospun nanomaterials integrated with functional metal sulfides with distinct nanostructures. These functional materials have been prepared via two efficient strategies, namely direct electrospinning and post-synthesis modification of electrospun nanomaterials. In this review, we systematically present the chemical and physical properties of the electrospun nanomaterials integrated with metal sulfides and their application in electronic and optoelectronic devices, sensing, catalysis, energy conversion and storage, thermal shielding, adsorption and separation, and biomedical technology. Additionally, challenges and further research opportunities in the preparation and application of these novel functional materials are also discussed.

Ce-based catalysts used in advanced oxidation processes for organic wastewater treatment: A review

Refractory organic pollutants in water threaten human health and environmental safety, and advanced oxidation processes (AOPs) are effective for the degradation of these pollutants. Catalysts play vital role in AOPs, and Ce-based catalysts have exhibited excellent performance. Recently, the development and application of Ce-based catalysts in various AOPs have been reported. Our study conducts the first review in this rapid growing field. This paper clarifies the variety and properties of Ce-based catalysts. Their applications in different AOP systems (catalytic ozonation, photodegradation, Fenton-like reactions, sulfate radical-based AOPs, and catalytic sonochemistry) are discussed. Different Ce-based catalysts suit different reaction systems and produce different active radicals. Finally, future research directions of Ce-based catalysts in AOP systems are suggested.

Polysaccharide-Based Hydrogels Derived from Cellulose: The Architecture Change from Nanofibers to Hydrogels for a Putative Dual Function in Dye Wastewater Treatment

Agricultural production-caused water contamination has become an urgent environmental issue that has drawn much attention in recent years. One such contamination case is the environmental disposal of colored effluents from the food processing industry (i.e., food dyes). Effective methods for removing dye contaminants from water have been increasingly sought, and different adsorbents have been developed for this purpose. Here, polysaccharide-based hydrogels derived from cellulose were constructed and used in the removal of methylene blue (MB) (as the representative dye) from an aqueous medium (as simulated dye liquor wastewater). To improve the purification efficiency, TiO₂ nanoparticles were encapsulated into cellulose nanofibers, which were consequently changed to hydrogels with respective advantages. The morphology, chemical composition, and structure of the as-prepared polysaccharide-based hydrogels and the transformation process from nanofibers to hydrogels were revealed by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction, and the presence of a gel network structure and TiO₂ nanoparticles was confirmed. As expected, the polysaccharide-based hydrogels exhibited good MB removal performance because of their synergistic effects of absorption and photocatalytic degradation. Furthermore, the cell cytotoxicity test showed that the polysaccharide-based hydrogels possessed good biocompatibility. The facile, noncytotoxic, and general strategy presented here could be extended to the preparation of other polysaccharide-based hydrogel materials and has good prospects for application in wastewater treatment.

Bio-inspired construction of melanin-like polydopamine-coated CeO2 as a high-performance visible-light-driven photocatalyst for hydrogen production

In recent years, cerium oxide has been the most widely studied photocatalyst due to its unique properties.

Enhanced visible light-active CeO2/CuO/Ag2CrO4 ternary heterostructures based on CeO2/CuO nanofiber heterojunctions for the simultaneous degradation of a binary mixture of dyes

CeO₂/CuO/Ag₂CrO₄ composite is fabricated using an electrospinning and precipitation. Also, composite can photodegrade RB and MB under visible light irradiation. CeO₂/CuO/Ag₂CrO₄ can enhanced photocatalytic activity due to formed heterojunction.

Removal of paraquat from aqueous solutions by a bentonite modified zero-valent iron adsorbent

Bentonite-supported zero-valent iron (B-ZVI) composite is synthesized from bentonite, which was then used as an adsorbent to remove paraquat from aqueous solutions.

Conductive Electrospun Nanofiber Mats

Conductive nanofiber mats can be used in a broad variety of applications, such as electromagnetic shielding, sensors, multifunctional textile surfaces, organic photovoltaics, or biomedicine. While nanofibers or nanofiber from pure or blended polymers can in many cases unambiguously be prepared by electrospinning, creating conductive nanofibers is often more challenging. Integration of conductive nano-fillers often needs a calcination step to evaporate the non-conductive polymer matrix which is necessary for the electrospinning process, while conductive polymers have often relatively low molecular weights and are hard to dissolve in common solvents, both factors impeding spinning them solely and making a spinning agent necessary. On the other hand, conductive coatings may disturb the desired porous structure and possibly cause problems with biocompatibility or other necessary properties of the original nanofiber mats. Here we give an overview of the most recent developments in the growing field of conductive electrospun nanofiber mats, based on electrospinning blends of spinning agents with conductive polymers or nanoparticles, alternatively applying conductive coatings, and the possible applications of such conductive electrospun nanofiber mats.

Enhanced Visible-Light Photocatalytic Activity of Ag QDs Anchored on CeO2 Nanosheets with a Carbon Coating

Ag quantum dots (QDs) anchored on CeO₂ nanosheets with a carbon coating (Ag/CeO₂@C) (composites) were prepared via an in situ reduction approach for the photocatalytic degradation of Cr(VI) and tetracycline hydrochloride (TCH) in the visible-light region. The photocatalytic activity of Ag/CeO₂@C was greatly affected by carbon content, Ag-doping content, Cr(VI) concentration, pH value, and inorganic ions. Enhanced photocatalytic activity was obtained by Ag/CeO₂@C (compared to CeO₂ and CeO₂@C), of which 3-Ag/CeO₂@C-2 with an Ag-doping content of 5.41% presented the best removal efficiency and the most superior stability after five cycles. ·O₂⁻ and ·OH radicals were crucial for the photocatalytic capacity of 3-Ag/CeO₂@C-2. The combined effect of the surface plasma resonance (SPR) of Ag QDs, an electron trapper of carbon shells, and the redox activity of the Ce(III)/Ce(IV) coupling induced efficient charge transfer and separation, suppressing the recombination of electron–hole pairs.