PAN supported Ag-AgBr@Bi20TiO32 electrospun fiber mats with efficient visible light photocatalytic activity and antibacterial capability

Recent advances in electrospinning-nanofiber materials used in advanced oxidation processes for pollutant degradation

Electrospun nanofiber membranes have emerged as a novel catalyst, demonstrating exceptional efficacy in advanced oxidation processes (AOPs) for the degradation of organic pollutants. Their superior performance can be attributed to their substantial specific surface area, high porosity, ease of modification, rapid recovery, and unparalleled chemical stability. This paper aims to comprehensively explore the progressive applications and underlying mechanisms of electrospun nanofibers in AOPs, which include Fenton-like processes, photocatalysis, catalytic ozonation, and persulfate oxidation. A detailed discussion on the mechanism and efficiency of the catalytic process, which is influenced by the primary components of the electrospun catalyst, is presented. Additionally, the paper examines how concentration, viscosity, and molecular weight affect the characteristics of the spinning materials and seeks to provide a thorough understanding of electrospinning technology to enhance water treatment methods. The review proposes that electrospun nanofiber membranes hold significant potential for enhancing water treatment processes using advanced oxidation methods. This is attributed to their advantageous properties and the tunable nature of the electrospinning process, paving the way for advancements in water treatment through AOPs.

Rational construction of ZnO/CuS heterostructures-modified PVDF nanofiber photocatalysts with enhanced photocatalytic activity

PVDF/ZnO/CuS photocatalysts with ZnO/CuS heterojunctions were synthesized via electrospinning, hydrothermal, and ion-exchange techniques. As matrix materials, electrospun PVDF nanofibers are easy to be recycled and reused. ZnO nanorods anchored on PVDF nanofiber with high specific surface area provide abundant active reaction sites for photocatalysis. While the loaded CuS nanoparticles as a photosensitizer compensate the low quantum efficiency of ZnO and improve the visible-light photocatalytic efficiency. As a result, the PVDF/ZnO/CuS composited photocatalyst exhibits outstanding photocatalytic performance in exposure to UV and visible light owing to the suppressed recombination of electron-hole pairs and widened visible light absorption range. The kinetic constants of PVDF/ZnO/CuS nanocomposites under UV irradiation (9.01 × 10^-3 min^-1) and visible light (6.53 × 10^-3 min^-1) irradiation were 3.66 and 2.53 times higher than that of PVDF/ZnO (2.46 × 10^-3 min^-1 & 2.58 × 10^-3 min^-1), respectively. Furthermore, PVDF/ZnO/CuS nanocomposites demonstrate excellent robustness in terms of recycling and reuse, which is advantageous in practical applications.

Electrospun Ceramic Nanofibers for Photocatalysis

Ceramic fiber photocatalysts fabricated by electrospinning hold great potential in alleviating global environmental and energy issues. However, many challenges remain in improving their photocatalytic efficiencies, such as the limited carrier lifetime and solar energy utilization. To overcome these predicaments, various smart strategies have been invented and realized in ceramic fiber photocatalysts. This review firstly attempts to summarize the fundamental principles and bottlenecks of photocatalytic processes. Subsequently, the approaches of doping, surface plasmon resonance, and up-conversion fluorescent to enlarge the light absorption range realized by precursor composition design, electrospinning parameter control, and proper post heat-treatment process are systematically introduced. Furthermore, methods and achievements of prolonging the lifetime of photogenerated carriers in electrospun ceramic fiber photocatalysts by means of introducing heterostructure and defective composition are reviewed in this article. This review ends with a summary and some perspectives on the future directions of ceramic fiber photocatalysts.

Efficient degradation of Congo red and phenol by a new photocatalyst Ag/AgBr-Al-attapulgite composite under visible light irradiation

Nowadays the concern on the treatment of refractory organic pollutants (e.g., Congo red and phenolic compounds) in industrial wastewaters and their treated effluents with conventional technologies has been still continuously increasing. In this study, a novel visible light photocatalyst material, Ag/AgBr and Al loading on the attapulgite (ATP), was prepared for efficiently catalyzing the photodegradation of the two refractory substances, and its photocatalytic performance and recyclability were assessed. Results from transmission electron microscopy and X-ray diffraction confirmed the successful loading of Ag/AgBr and Al on the ATP. The prepared Ag/AgBr-Al-ATP composite presented substantially better catalytic performance than Ag/AgBr alone probably because the ATP as a carrier of catalyst provided more contact surface for catalyst Ag/AgBr and Congo red/phenol. In the Ag/AgBr-Al-ATP composite, the photocatalyst AgBr content increased from 20.4 to 34.9% due to the modification of ATP by Al. Correspondingly, the Ag/AgBr-Al-ATP composite presented its excellent photocatalytic performance under visible light irradiation: photodegradation efficiencies of Congo red and phenol of 1.73 mg/100 mg and 0.86 mg/100 mg were achieved. With the increase of pH, the photolysis efficiencies of Congo red and phenol both first increased and then decreased, whereas the optimal photocatalytic performance occurred at pH 7 for Congo red and pH 10 for phenol. The Ag/AgBr-Al composite presented a high catalytic activity for photolysis of Congo red and phenol in all the four consecutive reused cycles. The results in this study comprehensively demonstrated a promising photocatalyst for efficient removal of the similar refractory organics presented in industrial wastewaters, which deserves further investigation and development.

New Insights into The Photoactivity of Shape-Tailored BiVO4 Semiconductors via Photocatalytic Degradation Reactions and Classical Reduction Processes

In the present study, additive-free, pH-driven, hydrothermal crystallization was used to obtain shape-tailored monoclinic BiVO₄ photocatalysts. The as-prepared BiVO₄ products were systematically characterized, uncovering their crystallographic, morphologic and optical properties, while their applicability was verified in the visible light-driven photodegradation of oxalic acid and rhodamine B. Monoclinic clinobisvanite was obtained in most cases, with their band gap values located between 2.1 and 2.4 eV. The morphology varied from large, aggregated crystals, individual microcrystals to hierarchical microstructures. It was found that the degradation efficiency values obtained in the case of oxalic acid were directly related to the presence of (040) crystallographic plane, while the degradation of rhodamine B was partially independent by the presence of this structural feature. The importance of (040) crystallographic plane was also demonstrated via the reduction of Cu²⁺ to Cu, by analyzing the Raman spectra of the Cu containing samples, the mean primary crystallite size of Cu and Cu content. Furthermore, the presence of (040) crystallographic plane was directly proportional with the hydrodynamic properties of the powders as well.

Nanodecoration of electrospun polymeric fibers with nanostructured silver coatings by ionized jet deposition for antibacterial tissues

Silver-based nanomaterials are used as antibacterial agents in a number of applications, including wound dressing, where electrospun materials can effectively promote wound healing and tissue regeneration thanks to their biomimicry, flexibility and breathability. Incorporation of such nanomaterials in electrospun nonwovens is highly challenging if aiming at maximizing stability and antibacterial efficacy and minimizing silver detachment, without neglecting process straightforwardness and scalability. In this work nanostructured silver coatings were deposited by Ionized Jet Deposition (IJD) on Polylactic acid, a medical grade polyester-urethane and Polyamide 6,6 nanofibers. The resulting materials were thoroughly characterized to gain an in-depth view of coating morphology and substrate resistance to the low-temperature deposition process used. Morphology of silver coatings with well-cohesive grains having dimensions from a few tens to a few hundreds of nanometers was analyzed by SEM, TEM and AFM. TGA, DSC, FTIR and GPC showed that the polymers well withstand the deposition process with negligible effects on their properties, the only exception being the polylactic acid that resulted more susceptible to degradation. Finally, the efficacy against S. aureus and E. coli bacterial strains was demonstrated, indicating that electrospun fibers decorated with nanostructured silver by IJD represent a breakthrough solution in the field of antibacterial devices.

Electrospun Nanofibers Embedding ZnO/Ag2CO3/Ag2O Heterojunction Photocatalyst with Enhanced Photocatalytic Activity

The immobilization of photocatalyst onto substrate has a great potential for energy-intensive separation to avoid the costly separation process and unwanted release of photocatalyst into the treated water. In this study, electrospun nanofiber composed of polyvinylidene fluoride (PVDF) with the immobilized ZnO, ZnO/Ag2CO3, ZnO/Ag2CO3/Ag2O, and ZnO/Ag2O photocatalysts were prepared via the electrospinning process. The immobilized ZnO and heterojunctioned ZnO in the PVDF electrospun nanofiber were proven via X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The electrospinning allowed high chemical binding of the nanofiber composite with good physical interaction between the photocatalyst and the electrospun nanofiber. AFM images obtained for the nanofibers were found to be rougher than that of the pristine PVDF electrospun nanofiber. Among the photocatalyst embedded, the immobilized ZnO/Ag2CO3/Ag2O had endowed the nanofiber with an excellent photocatalytic activity and recyclability for the degradation of the RR120 under UV light irradiation. Based on the results, effective immobilization of ZnO/Ag2CO3/Ag2O in PVDF nanofiber with 99.62% photodegradation in 300 min compared to PVDF-ZnO, PVDF-ZnO/Ag2CO3, and PVDF-ZnO/Ag2O of 28.14%, 90.49%, and 96.34%, respectively. The effective ZnO/Ag2CO3/Ag2O immobilization into polymers with affinity toward organic dye pollutants could both increase the efficiency and reduce the energy requirements for water treatment via the photocatalytic application.

Antibacterial and antioxidant electrospun materials from poly(3-hydroxybutyrate) and polyvinylpyrrolidone containing caffeic acid phenethyl ester - "in" and "on" strategies for enhanced solubility

Caffeic acid phenethyl ester (CAPE) possesses a set of valuable biological properties: antioxidant, antibacterial, antitumor, anti-inflammatory, antiviral, etc. However, CAPE is poorly soluble in aqueous environment which is limiting its possible therapeutic applications. In the present study novel fibrous materials enhancing CAPE solubility and accelerating CAPE release were developed. The materials were prepared from poly(3-hydroxybutyrate) (PHB) by electrospinning and by electrospinning combined with dip-coating. The effects of the composition - without/with addition of polyvinylpyrrolidone (PVP) and of the design of fiber (CAPE in the bulk of the fiber or incorporated in the PVP coating) on some of the properties of these materials were studied. X-ray diffraction and differential scanning calorimetry analyses revealed that CAPE was in the amorphous state in CAPE-loaded fibers and in the PVP coating. The new CAPE-containing materials exhibited good antioxidant activity. The microbiological screening demonstrated that incorporation of CAPE in the fibers or in the coating induced complete killing of Gram-positive S. aureus and led to inhibition of the growth of Gram-negative E. coli by the fibrous materials. Moreover, pathogenic S. aureus did not adhere onto CAPE-containing fibrous mats. Therefore, the obtained materials are promising candidates for use as wound dressing materials.