Ag Nanofibers Research Articles

Effect of heating temperature on Ag nanofiber formation via self-reduction of Pt nanoparticle-doped AgNO3/PVA nanofibers

Effect of heating temperature on Ag nanofiber formation via self-reduction of Pt nanoparticle-doped AgNO3/PVA nanofibers

Just laser irradiation of silver benzoate water solution — A direct way of Ag nanofibers synthesis for broadband SERS detection

Highly efficient, homogeneous and reproducible substrates for surface enhanced Raman spectroscopy (SERS) are in high demand for practical broadband sensing and the detection of various analytes. The most promising SERS structures in terms of morphology are nanofibers, forming homogeneous coatings with broadband electric field enhancement. However, existing synthesis methods for the formation of nanofibers are multistage, requiring the preliminary synthesis of templates, using additional components, such as surfactants and capping agents, species extraction from the reaction mixture, washing and sedimentation onto a substrate. Here, we present a simple and scalable synthesis approach allowing the fabrication of long winding silver nanofibers directly on a substrate surface, without any additional stages. The process proposed is ecologically friendly and based on laser irradiation of a substrate–solution interface using a low intensity continuous wave unfocused laser beam with a wavelength of 448 nm. As the liquid phase, a silver benzoate water solution without any additional chemicals was used. The deposited nanofibers formed a continuous coating with an area corresponding to the laser beam, ca. 3 mm2, and were characterized by an enhancement factor as high as 107 in the broad spectral region, a low experimental detection limit of 10−11 M and high reproducibility of the SERS signal with a variation of ∼10%.

Exploring the potential of electrospun polymer-coated Ag nanofibers for synergistic SERS performance and real-world applications

Electrospinning is a prominent technique for fabricating polymer-stabilized composite nanofibers for surface-enhanced Raman scattering (SERS). However, further exploration of the surface chemistry of these electrospun composite substrates is crucial to manipulate the charge transfer (CT) effect and achieve synergistic effects between CT and localized surface plasmon resonance (LSPR) for enhanced bio-labeling and pesticide detection. Here, we present the development of a flexible and self-supporting SERS substrate using electrospinning, consisting of polymer-coated silver nanowires (AgNWs). By employing different polymer shells and probe molecules, we strategically adjusted the energy levels of the frontier orbitals, enabling effective control over the CT effect. The resulting nanofibers exhibited optimized selectivity and sensitivity through multiple CT routes, enabling the detection of thiram in apple skin using a convenient wiping sampling method with a low limit of detection (LOD) of 5 ng/cm². We also investigated other pesticides without viable CT routes to demonstrate the versatility of the composite substrates, although they exhibited relatively lower selectivity and sensitivity due to the absence of synergistic effects. This study highlights the potential of CT manipulation in harnessing synergistic effects in electrospun 2D composite nanofibers, thereby advancing the practical applications of SERS technology.

Preparation of photothermal responsive, antibacterial hydrogel by using PVA-Alg and silver nanofibers as building blocks.

Introduction: Photothermal responsive, antimicrobial hydrogels are very attractive and have great potential in the field of tissue engineering. The defective wound environment and metabolic abnormalities in diabetic skin would lead to bacterial infections. Therefore, multifunctional composites with antimicrobial properties are urgently needed to improve the current therapeutic outcomes of diabetic wounds. We prepared an injectable hydrogel loaded with silver nanofibers for efficient and sustained bactericidal activity. Methods: To construct this hydrogel with good antimicrobial activity, homogeneous silver nanofibers were first prepared by solvothermal method and then dispersed in PVA-lg solution. After homogeneous mixing and gelation, injectable hydrogels (Ag@H) wrapped with silver nanofibers were obtained. Results: By virtue of Ag nanofibers, Ag@H exhibited good photothermal conversion efficiency and good antibacterial activity against drug-resistant bacteria, while the in vivo antibacterial also showed excellent performance. The results of antibacterial experiments showed that Ag@H had significant bactericidal effects on MRSA and E. coli with 88.4% and 90.3% inhibition rates, respectively. Discussion: The above results indicate that Ag@H with photothermal reactivity and antibacterial activity is very promising for biomedical applications, such as wound healing and tissue engineering.

Facile Synthesis of Zinc Indium Oxide Nanofibers Distributed with Low Content of Silver for Superior Antibacterial Activity

Exploring new antibacterial materials is of great significance for limiting the transmission of germs and protecting human health. Although Ag and oxide nanoparticles have both been extensively used in the field of antibacterial, it is still urgently need to figure out how to combine their characteristics for sterilization. Herein, ZnO/In2O3‐Ag nanofibers are prepared with uniformly dispersed Ag through a facile method of electrospinning and subsequent sintering. The obtained nanofibers are of high purity and have diameters from 90 to 110 nm. The silver is in a zero‐valent state, which is beneficial for sterilization. The quantitative test of bacterial activity shows that the nanofibers are bactericidal for both Staphylococcus aureus and Escherichia coli, with an especially strong inhibitory effect on E. coli. At relatively low concentrations, 98% of E. coli can be killed. Herein, light is shed on exploring more complexes of oxide nanomaterials and Ag for sterilization.

Bifunctional porous SnO2/Ag nanofibers for efficient electroreduction of carbon dioxide to formate and its mechanism elucidation by in-situ surface-enhanced Raman scattering

Monitoring the reaction intermediates and revealing the real active sites are of great importance for elucidation mechanism and designing ideal catalysts. Here, bifunctional porous SnO2/Ag nanofibers (P-SnO2/Ag) are prepared and present high Faradaic efficiency (FE) of 92.4% for formate with a current density of 24.6 mA cm−2 at − 0.9 V (vs. RHE). The in-situ SERS spectra reveal that tin-oxide in P-SnO2/Ag nanofibers are easy reduced, indicates metallic tin likely be the real active site rather than Sn (IV) and Sn (II) oxide species in CO2RR. The characteristic SERS peak at around 1420 cm−1 corresponding to the key *OCHO* intermediate for HCOO- production is also captured, favorably formed after the first *CO2- intermediate suitably adsorbed on P-SnO2/Ag nanofibers via oxygen atoms. Combining the intrinsic SERS properties and excellent catalytic performance of P-SnO2/Ag nanofibers, a real correlation is established between the composition and chemical structure of the materials and their catalytic performance.

Preparation of poly(ε-caprolactone) nanofibrous mats incorporating graphene oxide-silver nanoparticle hybrid composite by electrospinning method for potential antibacterial applications

In this study, poly(ε-caprolactone) based fibrous mats incorporating graphene oxide-silver hybrid nanocomposite as a nanofiller were successfully prepared by electrospinning method for potential biomedical applications. First, graphene oxide-silver nanoparticles (GO-AgNPs) were synthesized and the obtained GO-AgNPs nanohybrid was characterized by different analytical techniques. It was observed that the obtained AgNPs, with an average size of 5 ± 0.5 nm and spherical shape, were uniformly anchored on the surface of GO. Then, the synthesized GO-AgNPs were added into PCL to improve its tensile and bactericidal performances. The structural, morphological, mechanical and wettability properties of PCL-based fibrous mats as well as the release of silver ion release from PCL matrix were examined. Based on the results, we found that the addition of GO to the PCL-3.0%Ag nanofibers resulted in increased hydrophilicity, tensile strength and resistance to elastic deformation, and the PCL-GO-3.0%Ag sample also had a significantly higher release of silver ions. Besides, PCL-GO–3.0%Ag mats showed good antibacterial activity against Staphylococcus aureus and Escherichia coli compared to the PCL, PCL-GO and PCL-Ag nanofibrous mats. In summary, this study showed that PCL-GO–3.0%Ag nanofibrous mats could be a promising biomaterial for potential antibacterial applications.

Ag Nanofibers with Ultrahigh Aspect Ratios Fabricated by Catalytic Reduction of Solution Blowspun AgNO<sub>3</sub>/PVA/PVP-mixed Nanofibers

Ag Nanofibers with Ultrahigh Aspect Ratios Fabricated by Catalytic Reduction of Solution Blowspun AgNO<sub>3</sub>/PVA/PVP-mixed Nanofibers

Synthesis of Electrospun PAN/TiO2/Ag Nanofibers Membrane As Potential Air Filtration Media with Photocatalytic Activity.

The PAN/TiO2/Ag nanofibers membrane for air filtration media was successfully synthesized with electrospinning method. The morphology, size, and element percentage of the nanofiber were characterized by a scanning electron microscopy–energy dispersive spectroscopy, while X-ray fluorescence and FTIR were used to observe the chemical composition. The water contact angle and UV–vis absorption were measured for physical properties. Performance for air filtration media was measured by pressure drop, efficiency, and quality factor test. TiO2 and Ag have been successfully deposited in nonuniform 570 nm PAN/TiO2/Ag nanofibers. The nanofiber membrane had hydrophilic surface after TiO2 and Ag addition with a water contact angle of 34.58°. UV–vis data showed the shifting of absorbance and band gap energy of nanofibers membrane to visible light from 3.8 to 1.8 eV. The 60 min spun PAN/TiO2/Ag nanofibers membrane had a 96.9% efficiency of PM2.5, comparable to results reported in previous studies. These properties were suitable to be applied on air filtration media with photocatalytic activity for self-cleaning performance.

Multifunctional poly(vinyl alcohol)/Ag nanofibers-based triboelectric nanogenerator for self-powered MXene/tungsten oxide nanohybrid NO2 gas sensor

Triboelectric nanogenerators (TENGs) have broad application prospects in flexible electronics and self - powered sensing devices. In this paper, a poly(vinyl alcohol)/silver (PVA/Ag) nanofibers - based TENG was developed for human respiration, movement and harmful gas monitoring. The peak - to - peak value of open - circuit voltage and powered density from the wind - driven PVA/Ag - based TENG can reach up to 530 V and 359 mW/m 2 , respectively. Constant voltage output can be achieved at a large range of wind speeds (2.5–8 m/s) and humdity levels (30–65% RH) by integrating a voltage regulator module with the wind - driven TENG, which provides a feasible solution for the wind - driven TENG as a stable voltage source under different wind strength. The self - powered Ti 3 C 2 T x MXene/WO 3 sensor driven by TENG has an excellent response (ΔUs/Us a = 510% @ 50 ppm) for NO 2 gas at room temperature, which is 15 times larger than that of the resistive MXene/WO 3 sensor. A multifunctional self - powered detection system was developed by integrating four TENGs with a gas sensor for detection of wind direction and wind - borne NO 2 , which can be used to trace the source of harmful gases. The wind - driven self - powered sensor system provides a sustainable and maintenance - free detection platform, which has great application potential in the field of environmental monitoring. • A wind-driven triboelectric nanogenerator (TENG) based on poly(vinyl alcohol)/Ag nanofibers film was fabricated. • The PVA/Ag-based TENG was demonstrated for human respiration and movement stimulation monitoring. • A high-performance Ti 3 C 2 T x MXene/tungsten oxide nanofibers-based NO 2 sensor was fabricated. • A multifunctional self-powered detection system was developed for detection of wind direction and wind-borne NO 2 .

Surface Enhanced Infrared Absorption Studies of SiO2–TiO2–Ag Nanofibers: Effect of Silver Electrodeposition Time on the Amplification of Signals

Surface Enhanced on Infrared Absorption (SEIRAS) and Raman Spectroscopy (SERS) are nondestructive analytic techniques used to detect low concentrations and recognize the fingerprints of molecules. The recognition of the absorption from samples by conventional infrared spectroscopy (IR) via Attenuated Total Reflection (ATR) is difficult for molecules with a low signal strength. However, developed structures with SERS and SEIRAS effect present problems such as high cost, low stability, and low compatibility. Research into new media to obtain greater amplification is largely based on the creation of nanoscale structures with symmetrical arrangements and reproducible distances, resulting in aggregates of nanoparticles that help generate hot spots which are active for amplification. The sol-gel and electrospinning method for the obtention of ceramics provides an alternative means by which to produce said substrates. Fibers of nanometric scale provide an increase of surface area which allows more contact to occur with analytes. Consequently, in this study, a silica-titania-silver nanostructured support that amplifies signal intensity for Raman and infrared spectroscopy was developed. The silica-titania support was developed by sol-gel and electrospinning techniques, and the as spun fibers were treated at 800 °C. Then, the ceramic fibrous membrane was placed on conductive indium tin oxide plastic to be doped with silver using an electroplating technique, varying the silver nitrate concentration (5, 10 and 20 mM), as well as electrodeposition times (1, 2, 5 and 10 min), with a constant voltage (1 V). Twelve different supports were obtained that showed amplification. The enhancement of infrared signals from pyridine and crystal violet molecules adsorbed on silica-titania-silver (SiO2–TiO2–Ag) nanofibers was studied in situ by Attenuated Total Reflection-Fourier Transformed Infrared Spectroscopy (ATR-FTIR). The highest amplification was obtained by the support doped at 10 min in a 10 mM concentration, with an amplification factor of 2.74 in the band localized at 3301 cm−1. In Raman spectroscopy, the highest amplification factor was 27.03, on the support doped for 5 min at a concentration of 5 mM.

Flexible Tactile Sensor Based on Patterned Ag-Nanofiber Electrodes through Electrospinning.

The growing demand for intelligent equipment has greatly inspired the development of flexible devices. Thus, disparate flexible multifunctional devices, including pressure sensitive flexible/stretchable displays, have drawn worldwide research attention. Electrodes maintaining conductivity and mechanical strength against deformations are indispensable components in all prospective applications. In this work, a flexible pressure mapping sensor array is developed based on patterned Ag-nanofibers (Ag-NFs) electrode through electrospinning and lithography. The metallic Ag layer is sputtered onto the electrospinning polyvinyl alcohol (PVA) NFs. A uniform and super conductive electrode layer with outstanding mechanical performance is thus formed after dissolving PVA. Followed by the traditional lithography method, a patterned electrode array (4 × 4 sensors) is obtained. Based on the newly developed triboelectric nanogenerator (TENG) technology, a flexible pressure-mapping sensor with excellent stability towards bending deformations is further demonstrated. Moreover, a letter “Z” is successfully visualized by this pressure sensor array, encouraging more human–machine interactive implementations, such as multi-functional tactile screens.

Antibacterial activities of centrifugally spun polyethylene oxide/silver composite nanofibers

AbstractComposite nanofibers were prepared successfully by centrifugal spinning of poly(ethylene oxide) aqueous solutions containing silver nanoparticles. The core focus of the present work is to carefully evaluate the antibacterial activity of poly(ethylene oxide)–Ag composite nanofibers in the presence of Escherichia coli (E. coli) and Bacillus cereus (B. cereus) bacteria. Centrifugally spun nanofibers were obtained from poly(ethylene oxide)–Ag precursor solutions with different Ag nanoparticle loadings. The process parameters such as the spinneret rotational speed, collector‐spinneret distance, and relative humidity were optimized to obtain fine fibers. The complex morphology and flexible structure of the poly(ethylene oxide)–Ag composite fibers were investigated by scanning electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, and Raman spectroscopy. The composite nanofibers have been proven as a strong antibacterial agent against E. coli and B. cereus due to their capacity to form superior inhibition zones. The efficiency of inhibiting bacteria by nanofibers was over 98%. The workability of the bacteria was impeded by the nanofibrous membrane as the Ag nanoparticles presented an effective chemical ability to dysfunction the bacterial structure at the nanoscale. These results demonstrate that the centrifugally spun poly(ethylene oxide)–Ag nanofibers are promising antibacterial agents for biomedical applications.

PEDOT:PSS-glued MoO3nanowire network for all-solid-state flexible transparent supercapacitors

Flexible transparent supercapacitors (FTSCs) are essential for the development of next-generation transparent electronics, however, a significant challenge is to achieve high-areal-capacitance FTSCs without sacrificing optical transparency. Herein, poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)-glued MoO3 nanowires anchored on the Ag nanofiber (AgNF) network are employed as FTSC film electrodes, in which the AgNF network provides primary conducting pathways and guarantees rapid electron transport, while wide-bandgap semiconductor MoO3 nanowires glued by the ultrathin PEDOT:PSS layer provide abundant redox-active sites to store energy. Benefiting from the PEDOT:PSS as the conducting glue to promote the connection at the junctions between AgNFs and MoO3 nanowires, the as-prepared AgNFs/MoO3/PEDOT:PSS (AMP) film electrode demonstrates a high transmittance (82.8%) and large areal capacitance (15.7 mF cm−2), and has outperformed all the transparent conductive films known to date. Even after 11 000 charge/discharge cycles, the capacitance still remains at 92.4% of the initial value. The assembled all-solid-state FTSC device delivers an energy density of 0.623 μW h cm−2, a power density of 40 μW cm−2, and excellent mechanical robustness, implying a great potential in high performance FTSCs.

High precision epidermal radio frequency antenna via nanofiber network for wireless stretchable multifunction electronics

Recently, stretchable electronics combined with wireless technology have been crucial for realizing efficient human-machine interaction. Here, we demonstrate highly stretchable transparent wireless electronics composed of Ag nanofibers coils and functional electronic components for power transfer and information communication. Inspired by natural systems, various patterned Ag nanofibers electrodes with a net structure are fabricated via using lithography and wet etching. The device design is optimized by analyzing the quality factor and radio frequency properties of the coil, considering the effects of strain. Particularly, the wireless transmission efficiency of a five-turn coil drops by approximately only 50% at 10 MHz with the strain of 100%. Moreover, various complex functional wireless electronics are developed using near-field communication and frequency modulation technology for applications in content recognition and long-distance transmission (>1 m), respectively. In summary, the proposed device has considerable potential for applications in artificial electronic skins, human healthcare monitoring and soft robotics.

Investigation on Photoanode Modified With TiO2–ZnO–Ag Nanofibers in Dye-Sensitized Solar Cell Under Different Intensities of Illuminations

A photoanode modified with silver (Ag)–zinc oxide (ZnO)–titanium dioxide (TiO2) composite nanofibers (NFs) was prepared and used in dye-sensitized solar cells (DSSCs). TiO2–ZnO–Ag NFs were added as an additional layer between the TiO2 layer and the electrolyte of the DSSC to improve photovoltaic performance. Photovoltaic parameters of DSSC were measured under air mass 1.5 (AM 1.5, 100 mW/cm2). The impedance between the interface of photoanode/dye/electrolyte was identified by electrochemical impedance spectroscopy (EIS). We also investigated power conversion efficiencies under various intensities of the incident light through filters. The results of the photovoltaic measurements show that the power conversion efficiency ( $\eta $ ) of the DSSC modified with Ag–ZnO–TiO2 composite NFs is 6.43%. Compared with the power conversion efficiency of the DSSC without modification (5.44%), it is increased by 18%. The incorporation of ZnO and Ag into TiO2 NFs can enable the rapid transport of electrons and suppresses the opportunity for electron recombination. From Nyquist plot, the DSSC modified with Ag–ZnO–TiO2 composite NFs shows higher impedance than the DSSC without modification. It means that the photoanode modified with Ag–ZnO–TiO2 composite NFs can successfully suppress electron recombination. Under the intensity of incident light at 30 W/cm2, the DSSC modified with Ag–ZnO–TiO2 composite NFs has the highest power conversion efficiency of 9.16%.

Graphene Oxide Coated Silver Nanofiber Transparent Conducting Electrode

We fabricated a transparent conducting electrode composed of graphene oxide (GO) and silver (Ag) nanofibers. The graphene oxide was spray-coated on the Ag nanofiber film, which was fabricated by electrospinning process. Ag/poly(vinyl alcohol) ink was fabricated in a polymer matrix solution using the solgel method. The sprayed film was sintered at 200 <sup>o</sup>C for 100 min under H<sub>2</sub>/Ar atmosphere. The optical transmittance of the transparent electrodes was measured by UV/VIS spectroscopy, and sheet resistance was measured using I-V measurement system. As the amount of GO sprayed on the nanofibers increased, the diameters of the nanofibers increased, therefore, the transmittance of the electrode linearly decreased. However, the conductivity of the electrode increased. This is because the sprayed GO filled the gap between the nanofibers, and GO deposited on the surface of the nanofibers will form more effective electron pathways, resulting in increased conductivity. The GO-Ag nanofiber electrode also exhibited excellent environmental stability, and the sheet resistance of the electrode remained very stable during 30 days testing. The lowest sheet resistance of the transparent electrode was 250 ohm/sq with approximately 83% transparency at a wavelength of 550 nm. This excellent electrical properties and environmental stability might facilitate applications of the GO-Ag nanofiber electrode in optoelectronic devices.

Small‐Scale Nanoparticles Pyrolyzed from Layered Hydrotalcite between Graphene Interlayers as Intermediates for Self‐Assembly into Metal Oxide Nanosheets and Hollow Nanospheres

AbstractAlthough significant advances have been made in the synthesis of various two‐dimensional (2D) nanomaterials, problems of inefficient and difficult to scale applications remain. Here, a novel strategy is reported for obtaining 2D nanosheets from the 2D interlayer space of a graphene oxide (GO) membrane through combustion, which provides a simple and rapid method for the fabrication of 2D nanosheets as well as hollow nanospheres. Layered hydrotalcite from metal nitrates is formed between GO interlayers, which can be pyrolyzed into small‐sized oxide nanoparticles (3–5 nm) and then aggregated as intermediates into large‐sized nanosheets by combustion with Co, Ni, and Cr nitrates. However, the oxide intermediates self‐assemble into hollow oxide nanospheres for nitrates of more active Cd, Ce, and Eu. Moreover, the intermediates of inactive Ag, Pb, and Bi nitrates are reduced by GO into metal nanoparticles, which can fuse into Ag nanofiber network films, or Pb and Bi composite spheres because of their low melting point. This work is helpful to understand the nature of 2D space and develops a class of micro‐scale reactors between graphene layers.

Stretchable and Heat‐Resistant Protein‐Based Electronic Skin for Human Thermoregulation

AbstractSilk protein is one of the a promising materials for on‐skin and implantable electronic devices due to its biodegradability and biocompatibility. However, its intrinsic brittleness as well as poor thermal stability limits its applications. In this work, robust and heat‐resistant silk fibroin composite membranes (SFCMs) are synthesized by mesoscopic doping of regenerated silk fibroin (SF) via the strong interactions between SF and polyurethane. Surprisingly, the obtained SFCMs can endure the tensile test (>200%) and thermal treatment (up to 160 °C). Attributed to these advantages, traditional micromachining techniques, such as inkjet printing, can be carried out to print flexible circuits on such protein substrate. Based on this, Ag nanofibers (NFs) and Pt NFs networks are successfully constructed on both sides of the SFCMs to function as heaters and temperature sensors, respectively. Furthermore, the integrated protein‐based electronic skin (PBES) exhibits high thermal stability and temperature sensitivity (0.205% °C−1). Heating and temperature distribution detection are realized by array‐type PBES, contributing to potential applications in dredging of the blood vessel for alleviating arthritis. This PBES is also inflammation‐free and air‐permeable so that it can directly be laminated onto human skin for long‐term thermal management.

Electrospun nanofibers of poly (acrylonitrile-co-itaconic acid)/silver and polyacrylonitrile/silver: In situ preparation, characterization, and antimicrobial activity

In this study, it was aimed to prepare silver nanoparticles by reduction of silver salt (AgNO3) in situ by means of only synthesized polyacrylonitrile (PAN) and poly(acrylonitrile-co-itaconic acid) (P(AN-co-IA)) polymers, and N,N dimethylformamide (DMF). Thereafter, PAN/Ag and P(AN-co-IA)/Ag nanofibers were prepared via electrospinning. Spectroscopic and morphologic characterizations, electrical and thermal features, and antimicrobial activities of the prepared nanofibers against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were carried out in detail. It was observed that P(AN-co-IA) was much more effective than PAN on the reduction of AgNO3 and formation of silver nanoparticles. Silver nanoparticles and also itaconic acid contributed to decrease the cyclization temperature of PAN by generating sharp exothermic peaks. In addition, electrical conductivity of the nanofibers increased dramatically from E−13 to E−4 related to the presence of silver nanoparticles. Furthermore, incorporation of silver nanoparticles to the nanofiber membranes let bactericidal/fungicidal activities, which started at 6–24 h and continued for up to 168 h, against S. aureus, E. coli, P. aeruginosa, and C. albicans. The prepared silver containing nanofibers can be regarded as good candidates for potential use in the biomedical and pharmaceutical applications.