Search Results (72)

As a ternary metal oxide, indium gallium zinc oxide (IGZO) has gathered much attention for various applications, including gas sensors, due to its remarkable semiconducting properties, even in amorphous phases and at a low process temperature. For gas sensing applications, as surface area is an important factor affecting the response and performance of a gas sensor, nanofibers (NFs) with 1D morphology are expected to have good sensing performance. In this research, IGZO NFs were synthesized using an electrospinning process, which is a suitable technique for the large-scale and low-cost fabrication of NFs. Various characterizations were performed on the synthesized IGZO NFs, and the desired NF morphology and chemical composition were confirmed. Gas sensing experiments showed that the sensor was sensitive and selective to H₂S gas at 250 °C with a response of 40.5 to 100 ppm gas. This study demonstrates the strong potential of IGZO for use in sensitive and selective H₂S gas sensors. Full article

This research developed an active food packaging system featuring a tailored controlled-release mechanism. The system was fabricated using temperature-responsive poly(N-vinylcaprolactam) (PNVCL) nanofibers with a core-shell architecture. The resulting film incorporated cinnamon essential oil (CEO) as a natural preservative within a composite structure consisting of PNVCL, polyvinyl alcohol (PVA), polylactic acid (PLA) and CEO. The nanofiber film obtained via coaxial electrospinning exhibited a sandwich-like structure; the obtained fiber membrane is abbreviated as PP/PC, and the number represents the essential oil content. The PP/PC-4 composite demonstrated exceptional physical barrier properties and mechanical strength, with a WVP as high as 5.74 ± 0.37 (g·mm)/(m²·h·kPa). It also achieved the highest maximum force, elastic modulus, and tensile strength, recorded at 3.08 ± 0.31 N, 228.86 ± 15.46 MPa, and 5.26 ± 0.72 MPa, respectively, along with superior thermal stability. FTIR spectroscopy confirmed molecular interactions, specifically through C–H bonding, between the PLA/CEO core and the PNVCL shell layers. After 5 d of storage at 40 °C, the PP/PC-4 film retained substantial antibacterial efficacy. The antifungal efficacy demonstrated the highest performance, exceeding the control group by 32%. The weight loss rate on day four was 28%, significantly lower than other groups, while the hardness retention rate was 73% higher than the control group and 44% higher than PLA/CEO (4%). Application of this material prolonged the shelf life of Chinese bayberry (Myrica rubra) by 4 d while enhancing key preservation metrics. Owing to its advanced barrier properties, mechanical performance and temperature-modulated release characteristics, this PNVCL-based nanofiber film demonstrated strong potential as an intelligent packaging material for prolonging the freshness of perishable food products. Full article

This paper introduces a streamlined three-step synthesis method for crafting porous Fe₂O₃/ZnO nanofibers (NFs). Initially, Fe₂O₃ nanoparticles (NPs) were synthesized using the hydrothermal method. Subsequently, PVP NFs laden with Fe₂O₃ NPs and zinc salt were synthesized via an electrospinning method. Finally, porous Fe₂O₃/ZnO NFs were fabricated through calcination, resulting in an average diameter of approximately 100 nm. Gas-sensing experiments illuminate that the porous Fe₂O₃/ZnO NFs exhibit outstanding sensitivity, selectivity, and robust long-term stability. Although the response magnitude decreased under high relative humidity (RH) due to competitive adsorption, the sensor maintained distinct detectable responses towards NO₂ vapor at an optimum temperature of 225 °C. Particularly noteworthy is the substantial enhancement in NO₂ sensing properties observed in the Fe₂O₃/ZnO composite compared to pure ZnO NFs. This enhancement can be ascribed to the distinctive microstructure and heterojunction formed between Fe₂O₃ and ZnO. Full article

Relative humidity (RH) and temperature are crucial parameters in environmental monitoring and have attracted significant attention. However, traditional commercial sensors typically suffer from inherent limitations such as structural complexity, bulkiness, and high manufacturing costs. To address these issues, this study proposes a novel tilted fiber Bragg grating (TFBG)-based optical fiber humidity sensor, coated with a composite film of polyvinyl alcohol (PVA) and graphene oxide (GO). First, the sensing mechanisms of the TFBG functionalized with nanofiber films were theoretically analyzed, and the transmission spectra of TFBG under varied structural parameters were simulated. These theoretical investigations laid a solid foundation for subsequent experimental validation. Subsequently, PVA/GO composite nanofiber films tailored for humidity sensing were fabricated by electrospinning technology, and the proposed TFBG sensor was experimentally implemented in accordance with the theoretical design. The experimental results indicate that the developed sensor exhibits a humidity sensitivity of −0.24 pm/%RH within the RH range of 35–85%. Furthermore, we calculated temperature and RH changes while discounting cross-sensitivity, thereby enabling simultaneous decoupling of temperature and RH measurements. Owing to its distinctive advantages of compact size, light weight, and cost-effectiveness, the proposed TFBG sensor holds great promise for practical applications in environmental monitoring. Full article

This study explores the development of new room-temperature NO₂ sensors utilizing carbon nanofibers (CNFs), single-walled carbon nanotubes (SWCNTs), and their hybrids with reduced graphite oxide (rGO), fabricated via a facile drop casting method with varying concentrations of carbon/ethanol mixtures. The concentration-dependent relation of sensor response to NO₂ has been found. Comprehensive characterization techniques, including electron microscopy, Raman spectroscopy, optical microscopy, and X-ray diffraction were employed to analyze the sensing materials. Our results reveal that CNFs exhibit superior sensitivity, reaching −1.32%/ppm at an optimal suspension concentration of 1.5 mg/mL, outperforming SWCNTs. The creation of hybrid composites, specifically CNFs/rGO and SWCNTs/rGO, further enhances sensing performance due to synergistic effects. Molecular dynamics simulations revealed increased adsorption behavior of the CNFs/rGO hybrid sensing material. The fabricated devices, based on all-carbon composites, are effective and energy-efficient platforms for NO₂ detection, offering promising solutions for environmental monitoring, the chemical industry, and industrial safety applications. Full article

(1) Background: Developing fully bio-based lubricating greases requires eco-friendly alternatives to conventional harmful components. This study highlights unmodified nanocellulose as an effective structuring agent in vegetable oils, enabling 100% bio-based formulations. (2) Methods: Three bio-based greases were formulated using 1.4 wt.% cellulose nanofibers (CNFs), derived from elm wood pulp through mechanical and chemical pretreatment, as thickening agents in castor oil. Their tribological performance was evaluated under varying temperatures and contact loads and compared to a reference lithium-based grease (LBG) containing 14 wt.% thickener, also formulated with castor oil. (3) Results: Among the CNFs, the unbleached variant (CNF-U) which retained the highest lignin content exhibited the highest coefficient of friction (COF), ranging from 0.09 to 0.14 across test conditions, along with a wear scar diameter of approximately 615 µm at 60 °C. Notable differences in shear stress sensitivity were observed between mechanically and chemically treated nanofibers. The TEMPO-oxidized nanofiber (CNF-TO) grease demonstrated outstanding lubrication stability across contact loads of 10–40 N and temperatures from 25 to 100 °C, maintaining COF values below 0.1—comparable to the reference LBG at 40 N load. Wear scar analysis confirmed that CNF-based greases significantly reduced wear relative to the lithium reference: CNF-B produced the smallest scar diameter (188 µm at 25 °C) while CNF-TO yielded the lowest at 60 °C (457 µm). (4) Conclusions: Nanofiber type and pretreatment significantly impact the tribological performance of CNF-based biogreases. TEMPO-oxidized CNFs provided stable lubrication under varied loads and temperatures, while all CNFs showed strong thermal adaptability, supporting their use in sustainable lubrication. Full article

The widespread use of formaldehyde in both industrial and household products has raised significant health concerns, emphasizing the need for highly sensitive sensors to monitor formaldehyde concentrations in the environment in real time. In this study, we report the fabrication of a highly sensitive formaldehyde gas sensor based on Ag₂O and PtO₂ co-decorated LaFeO₃ nanofibers, prepared by electrospinning, with an ultra-low detection limit of 10 ppb. Operating at an optimal temperature of 210 °C, the sensor exhibits high sensitivity, with a response value of 283 to 100 ppm formaldehyde—nearly double the response of the Ag-only decorated LaFeO₃ sensor. Additionally, the sensor demonstrated good selectivity, repeatability, and long-term stability over 80 days. The enhanced sensitivity is attributed to the strong adsorption ability of Ag towards both oxygen and formaldehyde, Ag’s catalytic oxidation of formaldehyde, PtO₂’s catalytic action on oxygen, and the spillover effect of PtO₂ on oxygen. This sensor holds significant potential for environmental monitoring due to its ultrahigh sensitivity and ease of fabrication. Full article

Advancements in thermoregulating textiles have been propelled by innovations in nanotechnology, composite materials, and smart fiber engineering. This article reviews recent scholarly papers on experimental passive and active thermoregulating textiles to present the latest advancements in these fabrics, their mechanisms of thermoregulation, and their feasibility for use. The review underscores that phase-change materials enhanced with graphene, boron nitride, and carbon nanofibers offer superior thermal conductivity, phase stability, and flexibility, making them ideal for wearable applications. Shape-stabilized phase-change materials and aerogel-infused fibers have shown promising results in outdoor, industrial, and emergency settings due to their durability and high insulation efficiency. Radiative cooling textiles, engineered with hierarchical nanostructures and Janus wettability, demonstrate passive temperature regulation through selective solar reflection and infrared emission, achieving substantial cooling effects without external energy input. Thermo-responsive, shape-memory materials, and moisture-sensitive polymers enable dynamic insulation and actuation. Liquid-cooling garments and thermoelectric hybrids deliver precise temperature control but face challenges in portability and power consumption. While thermoregulating textiles show promise, the main challenges include achieving scalable manufacturing, ensuring material flexibility, and integrating multiple functions without sacrificing comfort. Future research should focus on hybrid systems combining passive and active mechanisms, user-centric wearability studies, and cost-effective fabrication methods. These innovations hold significant potential for applications in extreme environments, athletic wear, military uniforms, and smart clothing, contributing to energy efficiency, health, and comfort in a warming climate. Full article

In this work, we report the synthesis of perovskite-type Ba-doped LaFeO₃ (La_1−xBa_xFeO₃, x = 0.00, 0.02, 0.04, and 0.06) nanofibers (NFs) using the electrospinning method. The synthesized La_1−xBa_xFeO₃ materials have a fibrous structure with an average fiber diameter of 250 nm. The fibers, in turn, consist of smaller crystalline particles of 20–50 nm in size. The sensor properties of La_1−xBa_xFeO₃ nanofibers were studied when detecting 20 ppm CO, CH₄, methanol, and acetone in dry air in the temperature range of 50–350 °C. Doping with barium leads to a significant increase in sensor response and a decrease in operating temperature when detecting volatile organic compounds (VOCs). The process of acetone oxidation on the surface of the most sensitive La_0.98Ba_0.02FeO₃ material was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed desorption in combination with mass spectrometry (TPD-MS). A mechanism for the sensor signal formation is proposed. Full article

Excessive water produced in oil reservoirs reduces oil recovery and increases the cost of water treatment. Conventional water control methods use synthetic polymer gels like PAM-PEI, which are sensitive to harsh reservoir conditions. This study investigates the use of cellulose nanofibers (CNF) to enhance polymer gels for oilfield water control under various temperatures, salinities, and pH conditions. Polymer gels were prepared by combining PAM and PEI with CNF concentrations of 1–4 wt% in deionized water. Salinity effects were studied by adding NaCl (1.5–2.5 g), while pH effects were assessed under acidic (pH 2–3), neutral, and alkaline (pH 13–14) conditions. The mixtures were stirred, homogenized, and subjected to thermal treatment in a water bath oven at temperatures ranging from 70 °C to 90 °C for gel formation. Gelation time was determined by the Sydansk gel code, and gel strength was assessed through storage modulus (G′) and loss modulus (G″) from oscillatory rheometry tests. Results show that lower temperatures increase gelation time, with higher CNF concentrations needed to elongate gelation at higher temperatures. At 30,000 ppm NaCl, gelation time decreases with increasing CNF, while at 50,000 ppm NaCl, it increases. Extreme pH conditions (pH 2–3 and pH 13–14) lead to longer gelation times with decreasing CNF concentration. While high salinity and extreme pH reduce gel strength, the addition of CNF enhances it, though this effect is minimal beyond 2–3 wt%. These findings suggest that CNF can improve the performance of polymer gels under challenging reservoir conditions. Full article

ZnO/MO_x (M = Fe^III, Co^II,III, Ni^II, Sn^IV, In^III, Ga^III; [M]/([Zn] + [M]) = 15 mol%) nanofiber heterostructures were obtained by co-electrospinning and characterized by X-ray diffraction, scanning electron microscopy and X-ray fluorescence spectroscopy. The sensor properties of ZnO and ZnO/MO_x nanofibers were studied toward reducing gases CO (20 ppm), methanol (20 ppm), acetone (20 ppm), and oxidizing gas NO₂ (1 ppm) in dry air. It was demonstrated that the temperature of the maximum sensor response of ZnO/MO_x nanofibers toward reducing gases is primarily influenced by the binding energy of chemisorbed oxygen with the surface of the modifier’s oxides. When detecting oxidizing gas NO₂, high sensitivity at a low measurement temperature can be achieved with a high concentration of free electrons in the near-surface layer of zinc oxide grains, which is determined by the band bending at the ZnO/MO_x interface characterized by the difference in the electron work function of ZnO and MO_x. Full article

Piezoelectric sensors convert mechanical stress into electrical charge via the piezoelectric effect, and when fabricated as fibers, they offer flexibility, lightweight properties, and adaptability to complex shapes for self-powered wearable sensors. Polyvinylidene fluoride (PVDF) nanofibers have garnered significant interest due to their potential applications in various fields, including sensors, actuators, and energy-harvesting devices. Achieving optimal piezoelectric properties in PVDF nanofibers requires the careful optimization of polarization. Applying a high electric field to PVDF chains can cause significant mechanical deformation due to electrostriction, leading to crack formation and fragmentation, particularly at the chain ends. Therefore, it is essential to explore methods for polarizing PVDF at the lowest possible voltage to prevent structural damage. In this study, a Design of Experiments (DoE) approach was employed to systematically optimize the polarization parameters using a definitive screening design. The main effects of the input parameters on piezoelectric properties were identified. Heat treatment and the electric field were significant factors affecting the sensor’s sensitivity and β-phase fraction. At the highest temperature of 120 °C and the maximum applied electric field of 3.5 kV/cm, the % β-phase (F(β)) exceeded 95%. However, when reducing the electric field to 1.5 kV/cm and 120 °C, the % F(β) ranged between 87.5% and 90%. The dielectric constant (ɛ′) of polarized PVDF was determined to be 30 at an electric field frequency of 1 Hz, compared to a value of 25 for non-polarized PVDF. The piezoelectric voltage coefficient (g₃₃) for polarized PVDF was measured at 32 mV·m/N at 1 Hz, whereas non-polarized PVDF exhibited a value of 3.4 mV·m/N. The findings indicate that, in addition to a high density of β-phase dipoles, the polarization of these dipoles significantly enhances the sensitivity of the PVDF nanofiber mat. Full article

Various electrospinning techniques can be used to produce nanofiber mats with randomly oriented or aligned nanofibers made of different materials and material mixtures. Such nanofibers have a high specific surface area, making them sensitive as sensors for health monitoring. The entire nanofiber mats are very thin and lightweight and, therefore, can be easily integrated into wearables such as textile fabrics or even patches. Nanofibrous sensors can be used not only to analyze sweat but also to detect physical parameters such as ECG or heartbeat, movements, or environmental parameters such as temperature, humidity, etc., making them an interesting alternative to other wearables for continuous health monitoring. This paper provides an overview of various nanofibrous sensors made of different materials that are used in health monitoring. Both the advantages of electrospun nanofiber mats and their potential problems, such as inhomogeneities between different nanofiber mats or even within one electrospun specimen, are discussed. Full article

Polyaniline−magnesia (PANI/MgO) composites with a fibrous nanostructure were synthesized via in situ oxidative polymerization, enabling uniform MgO integration into the polyaniline matrix. These composites were characterized using FTIR spectroscopy to analyze intermolecular bonding, XRD to assess crystallographic structure and phase purity, and SEM to examine surface morphology and topological features. The resulting PANI/MgO nanofibers were utilized to develop ammonia (NH₃) gas-sensing probes with evaluations conducted at room temperature. The study addresses the critical challenge of achieving high sensitivity and selectivity in ammonia detection at low concentrations, which is a problem that persists in many existing sensor technologies. The nanofibers demonstrated high selectivity and optimal sensitivity for ammonia detection, which was attributed to the synergistic effects between the polyaniline and MgO that enhance gas adsorption. Furthermore, the study revealed that the MgO content critically influences both the morphology and the sensing performance, with higher MgO concentrations improving sensor response. This work underscores the potential of PANI/MgO composites as efficient and selective ammonia sensors, highlighting the importance of MgO content in optimizing material properties for gas-sensing applications. Full article

Perovskite oxide LaFeO₃(LFO) emerges as a potential candidate for formaldehyde (HCHO) detection due to its exceptional electrical conductivity and abundant active metal sites. However, the sensitivity of the LFO sensor needs to be further enhanced. Herein, a series of La_xIn_1-xFeO₃ (x = 1.0, 0.9, 0.8, and 0.7) nanofibers (L_xIn_1-xFO NFs) with different ratios of La/In were obtained via the electrospinning method followed by a calcination process. Among all these L_xIn_1-xFO NFs sensors, the sensor based on the L_0.8In_0.2FO NFs possessed the maximum response value of 18.8 to 100 ppm HCHO at the operating temperature of 180 °C, which was 4.47 times higher than that based on pristine LFO NFs (4.2). Furthermore, the L_0.8In_0.2FO NFs sensor also exhibited a rapid response/recovery time (2 s/22 s), exceptional repeatability, and long-term stability. This excellent gas sensing performance of the L_0.8In_0.2FO NFs can be attributed to the large number of oxygen vacancies induced by the replacement of the A-site La³⁺ by In³⁺, the large specific surface area, and the porous structure. This research presents an approach to enhance the HCHO gas sensing capabilities by adjusting the introduced oxygen vacancies through the doping of A-sites in perovskite oxides. Full article