Metal Oxide Nanofibers Research Articles

Nanofiber array growth mechanism based on dealloying of Ti-Cu/Cu multilayer precursor film

Metal oxide nanofiber array materials are a type of material with outstanding performance and application potential. Recently, an efficient dealloying method using Ti–Cu/Cu multilayer film as a precursor was proposed to prepare titanium oxide nanofiber array structure. However, the growth mechanism and formation process of such an oxide nanofiber array grown on multilayer-film is not clear. In this work, we use Ti-Cu/Cu multilayer film as the precursor, NaOH solution as the dealloying corrosion solution, and free dealloying at room temperature. On the basis of successfully obtaining TiO2 nanofiber array films, the morphology formation and evolution process of the nanoarray were carefully monitored, and the atomic percentage changes of Ti, Cu and O elements in the dealloying precursor films were tested, as well as the formation and crystalline phase evolution trends of TiO2. Based on the experimental data, we tried to draw a schematic diagram of the formation process of this TiO2 nanofiber array, and proposed that the growth mechanism of the TiO2 nanofiber array is the precipitation growth process both with Ostwald Ripening and Oriented Attachment mechanisms. Then, the photocurrent response characteristics of the obtained nanofiber array structure samples were analyzed, and it was found that the nanofiber array structure had a certain effect on the photocurrent response performance. The completion of the present work is expected to provide a theoretical reference for the preparation and application of other metal oxide nanofiber array by dealloying method.

Cobalt-Doped Ceria Sensitizer Effects on Metal Oxide Nanofibers: Heightened Surface Reactivity for High-Performing Chemiresistive Sensors.

Chemiresistive gas sensors based on semiconducting metal oxides typically rely on noble metal catalysts to enhance their sensitivity and selectivity. However, noble metal catalysts have several drawbacks for practical utilization, including their high cost, their propensity for spontaneous agglomeration, and poisoning effects with certain types of gases. As such, in the interest of commercializing the chemiresistive gas sensor technology, we propose an alternative design for a noble-metal-free sensing material through the case study of Co-doped ceria (Co-CeO2) catalysts embedded in a SnO2 matrix. In this investigation, we utilized electrospinning and subsequent calcination to prepare Co-CeO2 catalyst nanoparticles integrated with SnO2 nanofibers (NFs) with uniform particle distribution and particle size regulation down to the sub-2 nm regime. The resulting Co-CeO2@SnO2 NFs exhibited superior gas sensing characteristics toward isoprene (C5H8) gas, a significant biomarker for monitoring the onset of various diseases through breath diagnostics. In particular, we identified that the Co-CeO2 catalysts, owing to the transition metal doping, facilitated the spillover of chemisorbed oxygen species to the SnO2 sensing body. This resulting in the sensor having a 27.4-fold higher response toward 5 ppm of C5H8 (compared to pristine SnO2), exceptionally high selectivity, and a low detection limit of 100 ppb. The sensor also exhibited high stability for prolonged response-recovery cycles, attesting to the strong anchoring of Co-CeO2 catalysts in the SnO2 matrix. Based on our findings, the transition metal-doped metal oxide catalysts, such as Co-CeO2, demonstrate strong potential to completely replace noble metal catalysts, thereby advancing the development of the commercially viable chemiresistive gas sensors free from noble metals, capable of detecting target gases at sub-ppm levels.

Performance enhancement of rechargeable zinc-air battery through synergistic ex-solution of multi-component Pt/CoWO4-x catalysts

Advancing zinc-air battery (ZAB) technology necessitates the development of air cathode electrocatalyst systems that demonstrate high reactivity and stability. We introduce a novel method to fabricate a robust catalyst-support hybrid. This hybrid comprises Co-doped Pt nanoparticles (NPs) anchored on metal oxide (Ex-PtCoWO) nanofibers (NFs), synthesized via electrospinning followed by selective metal ex-solution. Controlling the ex-solution of metal NPs leads to a highly active and stable oxygen reduction reaction (ORR). Moreover, the three-dimensional CoWO4-x NFs network enhances the surface exposure of ex-solved metal NPs, thereby aiding both selective ex-solution and the provision of active sites for the oxygen evolution reaction (OER) during ZAB recharge. The Ex-PtCoWO NF exhibits an ORR half-wave potential of 0.89 V and an OER potential of 1.69 V at 10 mA cm−2 in alkaline media. ZABs utilizing Ex-PtCoWO NF show an extended cycle life of over 240 h with reduced charge-discharge polarization, compared to commercial catalysts.

Recent advances in developing electrochemical (bio)sensing assays by applying natural polymer-based electrospun nanofibers: A comprehensive review

Electrospinning is a very powerful technique to produce highly complex nanofibers with tunable properties. This technique provides efficiency, versatility, and low cost to create nanofiber assemblies from a rich variety of natural and synthetic polymers combined with different types of nanoparticles. Electrospun nanofiber materials have demonstrated significant potential in various applications, such as sensors and biosensors, tissue engineering, drug delivery, energy conversion, and storage. This is mainly due to their unique characteristics including mechanical strength, large specific surface area, diverse polymer composition, and simple manufacturing process. Nanofiber-based biosensors offer several advantages over conventional biosensors, including enhanced responsiveness, wider linear range, higher sensitivity, lower limit of detection (LOD), and cost-effectiveness. Recently, there has been considerable interest in developing nanobiocomposites by integrating bioreceptors and conductive nanomaterials into carbon, metal oxide, or polymer electrospun nanofibers. In this comprehensive review, we explore advanced biosensors based on electrospinning technology, including biosensors modified with electrospun carbon, metal/metal oxide, as well as polymer-based and polymer-modified biosensors. After a general and short description of the electrospinning process and electrospinning conditions affecting the production of different nanofibers, the application of electrospun nanofibers for the design of electrochemical (bio)sensors is discussed.

Flexible, cuttable, origami-enabling ceramic nanofiber mat for visible light-driven catalysts

Despite possessing abundant potential, the brittleness of oxide ceramic nanofibers limits their use in self-standing flexible photocatalysts with easy separation/recycling and customized shaping. Here, we have reported a novel flexible ceramic constructed using electrospinning of metal oxide nanofiber mats of two different phases (CeO2–TiO2 [CTO]) with controllable composition. Although pure TiO2 and CeO2 nanofibers are too brittle to endure bending, CTO nanofibers show enhanced mechanical properties that make them flexible, bendable, cuttable, and origami-enabled. To study mechanical resilience and nanofiber structures, we have made a series of CTO nanofiber mats with different ratios of TiO2 and CeO2. The results reveal that the heterogeneous TiO2 and CeO2 interface creates stress transfer pathways, while the amorphous TiO2 phase absorbs stress. The CTO nanofiber mats can act as an efficient photocatalyst for the degradation of organic pollutants under visible light. The photocatalytic activity of the oxide ceramic mats is closely related to energy band positions and Ce3+ content. The decrease in the band gap of the CTO nanofiber mats enables the absorption of visible light, and the conduction band is positioned adequately to produce oxygen radicals via electron transfer. Consequently, the efficient degradation of organic pollutants can be achieved in the presence of the CTO nanofiber mat under visible light. Furthermore, the CTO nanofiber mats are coated with other metal oxides to form p–n junction band structures, which facilitate the separation of holes and electrons, resulting in even higher catalytic activity.

Defect-Rich SnO2 Nanofiber as an Oxygen-Defect-Driven Photoenergy Shield against UV Light Cell Damage.

Usually, most studies focus on toxic gas and photosensors by using electrospinning and metal oxide polycrystalline SnO2 nanofibers (PNFs), while fewer studies discuss cell-material interactions and photoelectric effect. In this work, the controllable surface morphology and oxygen defect (VO) structure properties were provided to show the opportunity of metal oxide PNFs to convert photoenergy into bio-energy for bio-material applications. Using the photobiomodulation effect of defect-rich polycrystalline SnO2 nanofibers (PNFs) is the main idea to modulate the cell-material interactions, such as adhesion, growth direction, and reactive oxygen species (ROS) density. The VO structures, including out-of-plane oxygen defects (op-VO), bridge oxygen defects (b-VO), and in-plane oxygen defects (ip-VO), were studied using synchrotron analysis to investigate the electron transfer between the VO structures and conduction bands. These intragrain VO structures can be treated as generation-recombination centers, which can convert various photoenergies (365-520 nm) into different current levels that form distinct surface potential levels; this is referred to as the photoelectric effect. PNF conductivity was enhanced 53.6-fold by enlarging the grain size (410 nm2) by increasing the annealing temperature, which can improve the photoelectric effect. In vitro removal of reactive oxygen species (ROS) can be achieved by using the photoelectric effect of PNFs. Also, the viability and shape of human bone marrow mesenchymal stem cells (hMSCs-BM) were also influenced significantly by the photobiomodulation effect. The cell damage and survival rate can be prevented and enhanced by using PNFs; metal oxide nanofibers are no longer only environmental sensors but can also be a bio-material to convert the photoenergy into bio-energy for biomedical science applications.

Bimetallic Ru1−xVxO2 and trimetallic Ru1−x−yVxCryO2 alloy nanofibers for efficient, stable and pH-independent oxygen evolution reaction catalysis

We present ruthenium-vanadium mixed alloy metal oxide (Ru1−xVxO2) nanofibers as well as chromium (Cr) doped Ru1−x−yVxCryO2 nanofibers using electrospinning and subsequent thermal annealing procedures as cost-effective, highly active and stable electrocatalyst for oxygen evolution reaction (OER). Both Ru1−xVxO2 and Ru1−x−yVxCryO2 nanofibers exhibited tetragonal crystalline structure, confirming that Ru, V, and Cr ions randomly occupied the tetragonal lattice sites due to the similar ionic sizes. Both Ru1−xVxO2 and Ru1−x−yVxCryO2 nanofibers showed excellent OER electrocatalytic activity, characterized by low overpotentials and small Tafel slopes, in both acidic and alkaline conditions. Ru1−xVxO2 (x = 0.52) nanofibers demonstrated an enhanced elemental substitution effect, leading to an enlarged active surface area that contributed to their exceptional OER activity. Ru1−x−yVxCryO2 nanofibers, achieved through optimal doping with Cr4+ ions, not only displayed significantly improved stability but also exhibited high OER activity. Interestingly, both Ru1−xVxO2 and Ru1−x−yVxCryO2 nanofibers consistently catalyzed alkaline OER, even under conditions of reactant depletion. These nanofibers, containing noble Ru with less than half of the total metal content, are proposed as efficient and cost-effective OER catalysts for use in both acidic and alkaline media.

Understanding the interplay of solution and process parameters on the physico-chemical properties of ZnO nanofibers synthesized by sol-gel electrospinning

Aging populations and the increase in chronic diseases worldwide demand efficient healthcare tools for simple, rapid, and accurate diagnosis and monitoring the human health. In this context, gas sensors are used to analyze the type of gas in the breath to diagnose chronic diseases. Metal oxide and ceramic nanofibers (NFs) produced by the electrospinning (ES) method have been investigated for potential use as gas sensors in the engineering and medical sectors. The material and process parameters are the main influencing factors on the functional performance of electrospun metal oxide NFs. Zinc oxide (ZnO) based NFs are used in various gas sensors due to the wide band gap (3.37eV), large exciton binding energy, and high mobility of charge carriers of ZnO. In this research, we made an attempt to study the effect of poly(vinyl alcohol) (PVA) and zinc acetate dihydrate (ZnAc2) concentrations and feed rate, voltage, spinneret tip-to-collector distance (TCD), and pyrolysis temperature on the physical properties of ZnO NFs. An average fiber diameter of 119 nm was obtained after pyrolysis at 600 °C of electrospun fiber produced from an aqueous PVA solution of concentration 15 w% with 7.5 w% ZnAc2 based on the weight of PVA. The grain size, transmittance, structural defects, and band gap energy of NFs were found to increase as a function of the pyrolysis temperature, which could be beneficial for the functional applications of these NFs.

Electronic nose based on multiple electrospinning nanofibers sensor array and application in gas classification

To mimic the human olfactory system, an electronic nose (E-nose, also known as artificial olfactory) has been proposed based on a multiple gas sensor array and a pattern recognition algorithm. Detection of volatile organic components (VOCs) has many potential applications in breath analysis, food quality estimation, and indoor and outdoor air quality monitoring, etc. In this study, a facile single-needle electrospinning technology was applied to develop the four different semiconductor metal oxide (MOS) nanofibers sensor arrays (SnO2, CuO, In2O3 and ZnO, respectively). The array shows a smooth surface and constant diameter of nanofiber (average of 150 nm) resulting in high sensitivity to multiple target analyte gases. Five human health related VOCs gases were measured by fabricated E-nose and different response patterns were obtained from four MOS nanofibers sensors. Combined with feature extraction from the response curves, a principal component analysis (PCA) algorithm was applied to reduce the dimension of feature matrix, Thus, the fabricated E-nose system successfully discriminated five different VOCs gases. Real-time and non-invasive gas monitoring by E-nose is very promising for application in human health monitoring, food monitoring, and other fields.

SiO2 anchored stacked-petal structure CoO-NiO/CNF as electrodes for high-rate-performance supercapacitors

The composites of transition metal oxide and carbon nanofibers (CNF) are promising electrode materials for supercapacitors in alkali solutions. However, the weak binding and unsatisfactory rate performance limit their application. To improve the weak binding, this study prepared the SiO2-modified carbon nanofibers (Si1-C) via electrospinning. Then the fully encapsulated CoO-NiO ([email protected]1-C) was fabricated on Si1-C by solvent-thermal and calcination. As is revealed, CNF containing SiO2 is conducive to forming a full coverage of CoO-NiO coating with a stacked petal structure. More importantly, nano-SiO2 plays the anchoring role of NiO-CoO and CNF, making the combination more firmly. The [email protected]1-C delivers a specific capacitance of 518.1 F g−1 at 0.5 A g−1, almost 2.25 times that of [email protected]0-C (229.9 F g−1 at 0.5 A g−1). When the current density increases to 50 A g−1, it is only 3.9 % lower than the capacitance (497.9 F g−1), which means a high rate performance. Moreover, asymmetric supercapacitor devices are assembled with activated carbon ([email protected]1-C//AC) with an energy density of 11.7 Wh kg−1, even at a high power density of 14,000.7 W kg−1.

Metal Oxide Electrospun Nanofibrous Membranes for Effective Dye Degradation and Sustainable Photocatalysis

The fabrication of metal oxide nanofibers using (titanium (IV) isopropoxide) and (tin (IV) tert-butoxide) of weight ratio 1:1 precursor in presence of poly (vinyl pyrrolidone) as a binder using a well-known electrospinning technique is reported. The average diameter of TiO2, SnO2, and composite TiO2-SnO2 nanofibers were found to be in the range 75–110 nm. The nanofibers were characterized using thermogravimetric analysis (TGA) to understand the polymer evaporation temperature and further analyzed using scanning electron microscopy (SEM) to study the morphology of the nanofibers. The oxidation states of titanium (Ti) and tin (Sn) ions were analyzed using X-ray photoelectron spectroscopy (XPS), indicating that the TiO2 undergoes a change even after loading SnO2. The photocatalytic efficiency of the composite TiO2-SnO2 fibers was investigated to study the degradation capabilities under ultraviolet (UV) light towards industrial polluting dyes such as Alcian Blue, Alizarin Red S, Bilirubin, Brilliant Blue, Bromophenol Blue, and Rhodamine B ITC. Rhodamine B showed a significant degradation rate of about 0.0064 min−1 in comparison to the other dyes.

The influence of the oxidation method on the properties of reduced graphene oxide

Derivatives of graphene have become important materials due to their excellent properties. Graphene oxide and reduced graphene oxide are especially interesting because they are produced relatively easily, cheaply and quickly. Among many possible applications, reduced graphene oxide is a good candidate for sensor applications. Its properties can be controlled at the production stage. The precursor used and the method of oxidation have a significant influence on its properties. Therefore, it is worth take a closer look at them. In this paper we analyse the influence of the oxidation method on the size of the reduced graphene stock which determine the sensitivity of the rGO layer. We used AFM microscopy for this purpose. Full Text: PDF ReferencesS.M. Majhi, A. Mirzaei, H.W. Kim, S.S. Kim, "Reduced Graphene Oxide (rGO)-Loaded Metal-Oxide Nanofiber Gas Sensors: An Overview", Sensors 21, 4 (2021). CrossRef M. Pumera, "Graphene-based nanomaterials for energy storage", Energy Environ. Sci. 4 3 (2011). CrossRef X. Yu, H. Cheng, M. Zhang, Y. Zhao, L. Qu, G. Shi, "Graphene-based smart materials", Nat. Rev. Mater. 2, 9 (2017). CrossRef M.Y. Xia, Y. Xie, C.H. Yu, G.Y. Chen, Y.H. Li, T., Zhang, Q. Peng, "Graphene-based nanomaterials: the promising active agents for antibiotics-independent antibacterial applications", J. Control. Release 10 (2019). CrossRef X. Zhu, Y. Zhou, Y. Guo, H. Ren, C. Gao, "Nitrogen dioxide sensing based on multiple-morphology cuprous oxide mixed structures anchored on reduced graphene oxide nanosheets at room temperature", Nanotechnology 30 45 (2019). CrossRef Z. Wu, Y. Wang, S. Ying, M. Huang, C. Peng, "Fabrication of rGO/Cuprous Oxide Nanocomposites for Gas Sensing", IOP Conf. Ser.: Earth Environ. Sci. 706, 1 (2021). CrossRef S. Pei, H.M. Cheng, "The reduction of graphene oxide", Carbon 50, 9 (2012). CrossRef K. Spilarewicz-Stanek, A. Kisielewska, J. Ginter, K. Bałuszyńska, I. Piwoński, "Elucidation of the function of oxygen moieties on graphene oxide and reduced graphene oxide in the nucleation and growth of silver nanoparticles", RSC Adv. 6, 65 (2016). CrossRef R. Muzyka, S. Drewniak, T. Pustelny, M. Sajdak, Ł. Drewniak, "Characterization of Graphite Oxide and Reduced Graphene Oxide Obtained from Different Graphite Precursors and Oxidized by Different Methods Using Raman Spectroscopy Statistical Analysis", Materials 14, 4 (2021) CrossRef B. Lesiak, G. Trykowski, J. Tóth, et al. "Chemical and structural properties of reduced graphene oxide—dependence on the reducing agent", J Mater. Sci. 56 (2021). CrossRef .

Ultrafast Ambient-Air Exsolution on Metal Oxide via Momentary Photothermal Effect

The process of exsolution for the synthesis of strongly anchored metal nanoparticles (NPs) on host oxide lattices has been proposed as a promising strategy for designing robust catalyst-support composite systems. However, because conventional exsolution processes occur in harsh reducing environments at high temperatures for long periods of time, the choice of support materials and dopant metals are limited to those with inherently high thermal and chemical stability. Herein, we report the exsolution of a series of noble metal catalysts (Pt, Rh, and Ir) from metal oxide nanofibers (WO3 NFs) supports in an entirely ambient environment induced by intense pulsed light (IPL)-derived momentary photothermal treatment (>1000 °C). Since the exsolution process spans an extremely short period of time (<20 ms), unwanted structural artifacts such as decreased surface area and phase transition of the support materials are effectively suppressed. At the same time, exsolved NPs (<5 nm) with uniform size distributions could successfully be formed. To prove the practical utility of exsolved catalytic NPs functionalized on WO3 NFs, the chemiresistive gas sensing characteristics of exsolved Pt-decorated WO3 NFs were analyzed, exhibiting high durability (>200 cyclic exposures), enhanced response (Rair/Rgas > 800 @ 1 ppm/350 °C), and selectivity toward H2S target gas. Altogether, we successfully demonstrated that ultrafast exsolution within a few milliseconds could be induced in ambient conditions using the IPL-derived momentary photothermal treatment and contributed to expanding the practical viability of the exsolution-based synthetic approaches for the production of highly stable catalyst systems.

TiO2-Based Nanofibrous Membranes for Environmental Protection.

Electrospinning is a unique technique that can be used to synthesize polymer and metal oxide nanofibers. In materials science, a very active field is represented by research on electrospun nanofibers. Fibrous membranes present fascinating features, such as a large surface area to volume ratio, excellent mechanical behavior, and a large surface area, which have many applications. Numerous techniques are available for the nanofiber’s synthesis, but electrospinning is presented as a simple process that allows one to obtain porous membranes containing smooth non-woven nanofibers. Titanium dioxide (TiO2) is the most widely used catalyst in photocatalytic degradation processes, it has advantages such as good photocatalytic activity, excellent chemical stability, low cost and non-toxicity. Thus, titanium dioxide (TiO2) is used in the synthesis of nanofibrous membranes that benefit experimental research by easy recyclability, excellent photocatalytic activity, high specific surface areas, and exhibiting stable hierarchical nanostructures. This article presents the synthesis of fiber membranes through the processes of electrospinning, coaxial electrospinning, electrospinning and electrospraying or electrospinning and precipitation. In addition to the synthesis of membranes, the recent progress of researchers emphasizing the efficiency of nanofiber photocatalytic membranes in removing pollutants from wastewater is also presented.

High performance and illumination stable In2O3 nanofibers-based field effect transistors by doping praseodymium

Although different kinds of one dimensional (1D) metal oxide nanofibers (MO-NFs) based field effect transistors (FETs) have been developed in recent years, their intrinsic deficiency in illumination instability are not addressed yet, which further prevented their application in practical life. In this work, due to the outstanding performance of suppressing oxygen vacancies and the blue light down-conversion with low charge transfer transition energy, praseodymium (Pr) is demonstrated an ideal candidate to dope into In2O3 NFs for both transferring the depletion mode to the enhancement mode and enhancing the illumination stability of the FETs. The optima In2O3 NFs-based FET was achieved by doping with 3 mol% Pr and exhibited an excellent electrical performance with a carrier mobility of 6.92 cm2V−1s−1, an on/off current ratio of ∼5.4 × 107, threshold voltage of 5.2 V, and subthreshold swing of 0.37 V/dec. Moreover, the FETs exhibited good illumination stability under 3600 s negative gate bias stress test with illumination (NBIS). Finally, the FET was also used as a switch to bright the LED in this work, demonstrating its great promise of Pr-doped In2O3 NFs in future one-dimensional electronic devices.

Ultra-small-sized multi-element metal oxide nanofibers: an efficient electrocatalyst for hydrogen evolution.

Compared to noble metals, transition metal oxides (TMOs) have positive development prospects in the field of electrocatalysis, and the synergy between the elements in multi-element TMO-based materials can improve their catalytic activity. However, it is still a challenge to synthesize multi-component TMO-based catalysts and deeply understand the effects of components on the catalytic performance of the catalysts. Here, we demonstrate multi-element ultra-small-sized nanofibers for efficient hydrogen production. The ternary NiFeCoO nanofiber-based electrode reached an overpotential of 82 mV at the current density of 10 mA cm−2 with a Tafel slope of 56 mV dec−1 in 1 M KOH, which are close to those of Pt plate (66 mV at 10 mA cm−2; the Tafel slope is 32 mV dec−1). In addition, the current density maintained 97% of its initial value after 10 h operation. We used the ternary NiFeCoO nanofiber-based electrode as an efficient counter electrode in photoelectrochemical hydrogen production to demonstrate the versatility of these nanofibers.

Self-organization of unimolecular micelles in beam stream for functional mesoporous metal oxide nanofibers

The use of linear amphiphilic block copolymers as templates is an important method for the preparation of mesoporous materials. However, the obtained assemblies are usually sensitive to synthetic conditions, which impedes the preparation of such mesoporous materials in certain environments. Herein, we report a universal strategy applying an amphiphilic multi-arm triblock copolymer in the preparation of mesoporous metal oxide nanofibers (NFs) using one metal oxide (TiO2, ZrO2, WO3, CeO2), or two (TiO2/WO3, TiO2/ZrO2, TiO2/CeO2) and three (TiO2/WO3/CuO) metal oxides as composites. The template consists of modified β-cyclodextrin as the center of the macromolecule which is attached sequentially to a block of polystyrene, poly(acrylic acid), and poly(ethylene oxide). Under electrospinning conditions, stable unimolecular micelles are formed and effectively co-assemble with metal ions to form fibrous nanostructures. As indicated by various characterization methods, the synthesized TiO2 and its derived composite NFs maintain a straight and continuous fibrous structure after calcination, and TiO2 NFs exhibit uniform mesopores of 10.8 nm in diameter and a large Brunauer-Emmett-Teller surface area of 143.3 m2 g−1. Benefiting from the characteristic structure, still present after modification, Pt-decorated mesoporous TiO2 NFs display excellent ability in the visible-light photocatalytic degradation of tetracycline, which is superior to the commercial P25 catalyst. This study reveals a promising strategy for the preparation of fibrous mesoporous metal oxides.

Overview on immobilization of enzymes on synthetic polymeric nanofibers fabricated by electrospinning.

The arrangement and type of support has a significant impact on the efficiency of immobilized enzymes. 1-dimensional fibrous materials can be one of the most desirable supports for enzyme immobilization. This is due to their high surface area to volume ratio, internal porosity, ease of handling, and high mechanical stability, all of which allow a higher enzyme loading, release and finally lead to better catalytic efficiency. Fortunately, the enzymes can reside inside individual nanofibers to remain encapsulated and retain their three-dimensional structure. These properties can protect the enzyme's tolerance against harsh conditions such as pH variations and high temperature, and this can probably enhance the enzyme's stability. This review article will discuss the immobilization of enzymes on synthetic polymers, which are fabricated into nanofibers by electrospinning. This technique is rapidly gaining popularity as one of the most practical ways to fibricate polymer, metal oxide, and composite micro or nanofibers. As a result, there is interest in using nanofibers to immobilize enzymes. Furthermore, present research on electrospun nanofibers for enzyme immobilization is primarily limited to the lab scale and industrial scale is still challanging. The primary future research objectives of this paper is to investigate the use of electrospun nanofibers for enzyme immobilization, which includes increasing yield to transfer biological products into commercial applications.

Electrospun Metal Oxide Nanofibers and Their Conductometric Gas Sensor Application. Part 2: Gas Sensors and Their Advantages and Limitations.

Electrospun metal oxide nanofibers, due to their unique structural and electrical properties, are now being considered as materials with great potential for gas sensor applications. This critical review attempts to assess the feasibility of these perspectives. This article discusses approaches to the manufacture of nanofiber-based gas sensors, as well as the results of analysis of the performances of these sensors. A detailed analysis of the disadvantages that can limit the use of electrospinning technology in the development of gas sensors is also presented in this article. It also proposes some approaches to solving problems that limit the use of nanofiber-based gas sensors. Finally, the summary provides an insight into the future prospects of electrospinning technology for the development of gas sensors aimed for the gas sensor market.

Electrospun Metal Oxide Nanofibers and Their Conductometric Gas Sensor Application. Part 1: Nanofibers and Features of Their Forming.

Electrospun metal oxide nanofibers, due to their unique structural and electrical properties, are now being considered as materials with great potential for gas sensor applications. This critical review attempts to assess the feasibility of these perspectives. The article in Part 1 discusses the basic principles of electrospinning and the features of the formation of metal oxide nanofibers using this method. Approaches to optimization of nanofibers’ parameters important for gas sensor application are also considered.