Flexible zirconium doped strontium titanate nanofibrous membranes with enhanced visible-light photocatalytic performance and antibacterial activities

Te4+ and Er3+ doped ZrO2 nanoparticles with enhanced photocatalytic, antibacterial activity and dielectric properties: A next generation of multifunctional material

Amid rising water contamination from industrial sources, tackling toxic dyes and pathogens is critical. Photocatalysis offers a cost-effective and eco-friendly solution to this pressing challenges. Herein, we synthesized Te4+ and Er3+ doped ZrO2 photocatalysts through hydrothermal method and investigated their efficacy in degrading Congo red (CR) and pathogens under visible light. XRD and Raman Spectroscopy confirm monoclinic and tetragonal mixed-phases without any impurities. Doping-induced defects, reduced crystalline diameter, high surface area, modified bandgap (2.95 eV), photoluminescence quenching, coupled with interfacial polarization, contribute to EZO's excellent dielectric response (1.149 × 106), for achieving remarkable photocatalytic activity, verified by photoelectrochemical measurements, LC-MS and phytotoxicity analysis. Under optimal conditions, EZO achieves 99% CR degradation within 100 min (TOC 79.9%), surpassing ZO (77%) and TZO (84%). Catalyst dosages, dye concentrations, and solution pH effect on EZO's photocatalytic performance are systematically assessed. Scavenging experiment emphasized the pivotal role of · OH in CR degradation with 96.4% efficiency after 4 cycles, affirming its remarkable stability. Moreover, EZO demonstrates ROS-mediated antibacterial activity against E. faecalis and E. coli bacteria under visible light, achieving >97% and >94% inhibition rate with an inhibition zone > 3 mm. Hence, the nanoparticle's dual action offers a practical solution for treating contaminated wastewater, ensuring safe irrigation.

PVA-Based Films with Strontium Titanate Nanoparticles Dedicated to Wound Dressing Application

Bioactive materials may be applied in tissue regeneration, and an example of such materials are wound dressings, which are used to accelerate skin healing, especially after trauma. Here, we proposed a novel dressing enriched by a bioactive component. The aim of our study was to prepare and characterize poly(vinyl alcohol) films modified with strontium titanate nanoparticles. The physicochemical properties of films were studied, such as surface free energy and surface roughness, as well as the mechanical properties of materials. Moreover, different biological studies were carried out, like in vitro hemo- and cyto-compatibility, biocidal activity, and anti-biofilm formation. Also, the degradation of the materials' utilization possibilities and enzymatic activity in compost were checked. The decrease of surface free energy, increase of roughness, and improvement of mechanical strength were found after the addition of nanoparticles. All developed films were cyto-compatible, and did not induce a hemolytic effect on the human erythrocytes. The PVA films containing the highest concentration of STO (20%) reduced the proliferation of Eschericha coli, Pseudomonas aeruginosa, and Staphylococcus aureus significantly. Also, all films were characterized by surface anti-biofilm activity, as they significantly lowered the bacterial biofilm abundance and its dehydrogenase activity. The films were degraded by the compost microorganism. However, PVA with the addition of 20%STO was more difficult to degrade. Based on our results, for wound dressing application, we suggest using bioactive films based on PVA + 20%STO, as they were characterized by high antibacterial properties, favorable physicochemical characteristics, and good biocompatibility with human cells.

Improvement strategies for oil/water separation based on electrospun SiO2 nanofibers

Oil spills and oily effluents from industry and daily life pose a great threat to all organisms in the ecosystem, while aggravating the problem of water scarcity, which has developed into a global challenge. Therefore, the development of advanced materials and technologies for oil/water separation has become a focus of attention. One-dimensional (1D) SiO2 nanofibers (SNFs) have become one of the most widely used inorganic nanomaterials in the past due to their stable chemical properties, excellent biocompatibility, and high temperature resistance etc. Meanwhile, electrospinning technique, as an emerging technology for treating oil/water emulsions, electrospun SNFs on this basis also has a number of advantages such as adjustable wettability, diverse structure and good connectivity. This review provides a systematic overview of the research progress of electrospun SNFs in different aspects. In this review, we first introduce the basic principles of electrospun SNFs, then focus on the design structures of various SNFs, propose corresponding strategies for the property improvement of SNFs, also analyze and consider the applications of SNFs. Finally, the challenges faced by electrospun SNFs in the field of oil/water separation are analyzed, and the future directions of electrospun SNFs are summarized and prospected.

Enhanced Visible-Photocatalytic Activities in Strong Acids and Strong Alkalis of Flexible Iron-SrTiO3 Nanofibrous Membranes

Traditional SrTiO₃ (STO) materials have high brittleness and poor deformation resistance. In this work, macroscopically flexible iron-doped SrTiO₃ (SFTO) nanofibrous membranes were prepared by electrospinning and calcination, which can be easily isolated and can maintain integrity to recycle as photocatalysts. Moreover, the SFTO nanofibrous membranes showed enhanced photocatalytic performance under strong acids (pH = 2) and strong alkalis (pH = 12). The SFTO nanofibrous membranes increased the catalytic rate of Congo red (CR) dye by about 10 times in visible light. The mechanism of photocatalytic activity enhancement was discussed by the combined effects of hydroxyl radicals and superoxide radicals. The successful preparation of SFTO nanofibrous membranes has offered a simple and economical approach to photocatalysis as well as environmental remediation.

Elastic and compressible Al2O3/ZrO2/La2O3 nanofibrous membranes for firefighting protective clothing

Developing ceramic nanofibrous membranes for the thermal insulation layer of firefighting protective clothing is vital. However, previous ceramic nanofibrous membranes were brittle and easy to break during service in high-temperature environments. The lack of elastic and compressible properties has limited the high-end applications of ceramic nanofibrous membranes. In this work, elastic and compressible Al₂O₃/ZrO₂/La₂O₃ nanofibrous membranes were fabricated via sol-gel electrospinning and calcination in air at different temperatures. The as-fabricated Al₂O₃/ZrO₂/La₂O₃ nanofibrous membranes can maintain excellent elasticity and compressibility in the temperature ranging from -196 to 1400 °C. Moreover, they have low thermal conductivity and high working temperatures. These favorable characteristics make the Al₂O₃/ZrO₂/La₂O₃ nanofibrous membranes a promising candidate for the thermal insulation layer of firefighting protective clothing.

From 1D Nanofibers to 3D Nanofibrous Aerogels: A Marvellous Evolution of Electrospun SiO2 Nanofibers for Emerging Applications

One-dimensional (1D) SiO₂ nanofibers (SNFs), one of the most popular inorganic nanomaterials, have aroused widespread attention because of their excellent chemical stability, as well as unique optical and thermal characteristics. Electrospinning is a straightforward and versatile method to prepare 1D SNFs with programmable structures, manageable dimensions, and modifiable properties, which hold great potential in many cutting-edge applications including aerospace, nanodevice, and energy. In this review, substantial advances in the structural design, controllable synthesis, and multifunctional applications of electrospun SNFs are highlighted. We begin with a brief introduction to the fundamental principles, available raw materials, and typical apparatus of electrospun SNFs. We then discuss the strategies for preparing SNFs with diverse structures in detail, especially stressing the newly emerging three-dimensional SiO₂ nanofibrous aerogels. We continue with focus on major breakthroughs about brittleness-to-flexibility transition of SNFs and the means to achieve their mechanical reinforcement. In addition, we showcase recent applications enabled by electrospun SNFs, with particular emphasis on physical protection, health care and water treatment. In the end, we summarize this review and provide some perspectives on the future development direction of electrospun SNFs.

Dependence of Photocatalytic Activity on the Morphology of Strontium Titanates

Strontium titanates were prepared with different morphologies by varying the ratio of solvents used during the synthesis. The effects of morphology and solvent (ethylene glycol to water) ratio were investigated both on the structure and photocatalytic activity of the samples. Structural properties were determined by X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and nitrogen adsorption measurements. The photocatalytic activity of the samples was evaluated by the photocatalytic oxidation of phenol and by the photocatalytic reduction of carbon dioxide. The ratio of solvents notably influenced the morphology, strontium carbonate content, primary crystallite size, and specific surface area of the samples. Samples prepared at low ethylene glycol to water ratios were spherical, while the ones prepared at high ethylene glycol to water ratios could be characterized predominantly by lamellar morphology. The former samples were found to have the highest efficiency for phenol degradation, while the sample with the most well-defined lamellar morphology proved to be the best for CO2 reduction.

Valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment: Approaching green chemistry and circular economy principles

Water pollution is one of the most critical issues worldwide and is a priority in all scientific agendas. Green nanotechnology presents a plethora of promising avenues for wastewater treatment. This review discusses the current trends in the valorization of zero-cost, biodegradable, and readily available agro-industrial biowaste to produce green bio-nanocatalysts and bio-nanosorbents for wastewater treatment. The promising roles of green bio-nanocatalysts and bio-nanosorbents in removing organic and inorganic water contaminants are discussed. The potent antimicrobial activity of bio-derived nanodisinfectants against water-borne pathogenic microbes is reviewed. The bioactive molecules involved in the chelation and tailoring of green synthesized nanomaterials are highlighted along with the mechanisms involved. Furthermore, this review emphasizes how the valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment adheres to the fundamental principles of green chemistry, circular economy, nexus thinking, and zero-waste manufacturing. The potential economic, environmental, and health impacts of valorizing agro-industrial biowaste to green nanomaterials are highlighted. The challenges and future outlooks for the management of agro-industrial biowaste and safe application of green nanomaterials for wastewater treatment are summarized.

Multifunctional Photocatalytic Filter Paper Based on Ultralong Nanowires of the Calcium-Alendronate Complex for High-Performance Water Purification

Semiconductor photocatalysts and membrane separation technology have been widely used in the field of water treatment. Usually, the particles of traditional semiconductor photocatalysts are easy to aggregate, difficult to separate from the liquid phase after photocatalysis, and may even cause secondary pollution. On the other hand, the membrane separation technology is also facing the problem of sharp decreases in removal efficiency and water flux caused by the membrane fouling. However, it is an attractive and promising solution to combine two technologies of photocatalysis and membrane separation for high-performance water treatment. In this work, we have developed the calcium oleate precursor solvothermal method to synthesize ultralong nanowires (UNWs) of Ca-alendronate (Ca-ALN) complex for the first time. Experimental results and data analysis indicate that the as-prepared Ca-ALN ultralong nanowires are an n-type semiconductor with an energy band gap of 3.41 eV. A new type of multifunctional photocatalytic filter paper has been developed based on ultralong nanowires of Ca-ALN complex (Ca-ALN-UNWs) and cellulose fibers (CFs). The as-prepared Ca-ALN-UNW/CF photocatalytic filter paper exhibits multifunctions of photocatalysis, adsorption, and filtration, which can be used for high-performance treatment of the wastewater containing various pollutants such as heavy-metal ions, dyes, antibiotics, and bacteria. The active oxygen species produced by the Ca-ALN-UNW/CF photocatalytic filter paper under light illumination are determined by electron spin resonance, and the energy band gap and photoelectric properties of the material are tested by ultraviolet-visible diffuse reflectance spectroscopy and electrochemical workstation. The pure water flux of the Ca-ALN-UNW/CF photocatalytic filter paper is very high, which can reach 2230.5 L m^-2 h^-1 under a working pressure of 0.1 MPa. The Ca-ALN-UNW/CF photocatalytic filter paper is promising for various applications such as highly efficient water purification and in the biomedical field.

Broccoli-liked silver phosphate nanoparticles supported on green nanofiber membrane for visible-light driven photodegradation towards water pollutants

In view of the practical application, it is imperative to develop efficient, exercisable, and visible light driven water pollution treatment materials. Herein, a high-efficiency green photocatalytic membrane for water pollution treatment is proposed and fabricated conveniently. Firstly, silver phosphate (Ag₃PO₄) nanoparticles with controlled morphology were prepared by simple liquid-phase precipitation method, and then a hierarchical structured Ag₃PO₄@polylactic acid (PLA) composite nanofiber membrane was prepared by electrospinning. Using electrospun PLA nanofiber membrane as a carrier of photocatalysts can significantly improve the dispersion of Ag₃PO₄nanoparticles, and increase the contact probability with pollutants and photocatalytic activity. The prepared PLA@Ag₃PO₄composite membrane was used to degrade methylene blue (MB) and tetracycline hydrochloride (TC) under visible light irradiation. The results showed that the removal ratio of pollutants on Ag₃PO₄@PLA composite nanofiber membrane was 94.0% for MB and 82.0% for TC, demonstrating an outstanding photocatalytic activity of composite membrane. Moreover, the PLA nanofiber membrane is a self-supported and biodegradable matrix. After five cycles, it can still achieve 88.0% of the initial photocatalytic degradation rate towards MB, showing excellent recyclability. Thus, this composite nanofiber membrane is a high-efficiency and environmental-friendly visible light driven water pollution treatment material that could be used in real applications.

Flexible Stannum-Doped SrTiO3 Nanofiber Membranes for Highly Sensitive and Reliable Piezoresistive Pressure Sensors

Mechanically flexible ceramic fiber-based electronic skins are attractive materials ascribed to the features of monitoring signals of various physical parameters in a harsh environment, but the inherent brittleness of the ceramic fibers has limited their wide applications in emerging fields, such as fire-protecting clothing. Herein, a strategy to fabricate the flexible stannum(IV)-doped SrTiO3 (SSTO) nanofiber membranes by a facile sol-gel electrospinning method is reported. The calcination temperature and Sn4+ doping content play vital roles in regulating the crystalline and pore structures that are closely relevant to the flexibility and mechanical properties of the resultant SSTO nanofiber membranes. The as-prepared SSTO nanofiber membranes exhibited exceptional flexibility with an optimum tensile strength of 0.22 MPa, an elongation rate of 1.8%, and a Young's modulus of 13.3 MPa. Significantly, the flexible SSTO nanofiber-based piezoresistive sensors exhibited intriguing sensing performance toward pressure involving high sensitivity (2.24 kPa-1) in a low-pressure range (<400 Pa), fast response time (12 ms) and recovery time (32 ms), good durability (>1000 cycles), and excellent stability at different humidity levels and elevated temperatures. Furthermore, the sensor can also accurately monitor the signals of human motion such as finger bending, throat swallowing, and radial pulse. The fabrication of flexible ceramic nanofiber-based piezoresistive sensors would pave the way to fabricate wearable devices for fire-protecting clothing, personal healthcare, real-time human activity detection.

The electrochemical, dielectric, and ferroelectric properties of Gd and Fe doped LaNiO3 with an efficient solar-light driven catalytic activity to oxidize malachite green dye

This work investigates the effects of double ion substitution on the ferroelectric, electrochemical, dielectric and photocatalytic properties of Gd and Fe doped La_1-yGd_yNi_1-xFe_xO₃ nanoparticles (NPs). La_1-yGd_yNi_1-xFe_xO₃ was fabricated by facile micro-emulsion path and its properties were studied by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman scattering, Fourier Transform of Infrared (FTIR), energy dispersive x-rays (EDX) techniques. It has a distorted rhombohedral shape with crystallite size within the range of 17-23 nm. The doped material has a spherical heterogeneous morphology, and its surface area increased with increased doping. The electrochemical (CV, EIS, and I-V), conductivity and dielectric (dielectric constant and low dielectric & tangent loss) properties of La_1-yGd_yNi_1-xFe_xO₃ were dependent on the contents of the dopants (Gd and Fe). The doped material had improved specific capacitance compared to the undoped LaNiO₃ due to the synergistic effect of Gd and Fe on the doped materials. The conductivity of Gd and Fe doped LaNiO₃ 5.16 × 10⁴ Sm^-1 was enhanced compared to the undoped LaNiO₃ 3.52 × 10^-2 Sm¹. Furthermore, hysteresis loop was used to investigate the coercivity (Hc), saturation magnetization (Ms) and remanence (Mr) of the material. The Ms and Mr values were enhanced with the content of the dopants. The photocatalytic activity (PCA) of the material in degrading malachite green (MG) dye was studied. La_1-yGd_yNi_1-xFe_xO₃ NPs was able to degrade up to 96.4% of the dye under visible light irradiation in 50 min. La_1-yGd_yNi_1-xFe_xO₃ has remarkable dielectric, electrochemical, ferroelectric and photo-catalytic properties and have potential applications in microwave, electrical, electronic, energy storage devices. It is also an active photo-catalyst material for the removal/oxidation of toxic pollutants from the environment.