Advanced and Smart Textiles during and after the COVID-19 Pandemic: Issues, Challenges, and Innovations.

The COVID-19 pandemic has hugely affected the textile and apparel industry. Besides the negative impact due to supply chain disruptions, drop in demand, liquidity problems, and overstocking, this pandemic was found to be a window of opportunity since it accelerated the ongoing digitalization trends and the use of functional materials in the textile industry. This review paper covers the development of smart and advanced textiles that emerged as a response to the outbreak of SARS-CoV-2. We extensively cover the advancements in developing smart textiles that enable monitoring and sensing through electrospun nanofibers and nanogenerators. Additionally, we focus on improving medical textiles mainly through enhanced antiviral capabilities, which play a crucial role in pandemic prevention, protection, and control. We summarize the challenges that arise from personal protective equipment (PPE) disposal and finally give an overview of new smart textile-based products that emerged in the markets related to the control and spread reduction of SARS-CoV-2.

Characterization of Electrospun Polysuccinimide-Dopamine Conjugates and Effect on Cell Viability and Uptake.

Biocompatible nanofibrous systems made by electrospinning have been studied widely for pharmaceutical applications since they have a high specific surface and the capability to make the entrapped drug molecule amorphous, which increases bioavailability. By covalently conjugating drugs onto polymers, the degradation of the drug as well as the fast clearance from the circulation can be avoided. Although covalent polymer-drug conjugates have a lot of advantages, there is a lack of research focusing on their nano-formulation by electrospinning. In this study, polysuccinimide (PSI) based electrospun fibrous meshes conjugated with dopamine (DA) are prepared. Fiber diameter, mechanical properties, dissolution kinetics and membrane permeability are thoroughly investigated, as these are crucial for drug delivery and implantation. Dopamine release kinetics prove the prolonged release that influenced the viability and morphology of periodontal ligament stem cells (PDLSCs) and SH-SY5Y cells. The presence of dopamine receptors on both cell types is also demonstrated and the uptake of the conjugates is measured. According to flow cytometry analysis, the conjugates are internalized by both cell types, which is influenced by the chemical structure and physical properties. In conclusion, electrospinning of PSI-DA conjugates alters release kinetics, meanwhile, conjugated dopamine can play a key role in cellular uptake.

Enhancement of Interfacial Hydrogen Interactions with Nanoporous Gold-Containing Metallic Glass.

Contrary to the electrochemical energy storage in Pd nanofilms challenged by diffusion limitations, extensive metal-hydrogen interactions in Pd-based metallic glasses result from their grain-free structure and presence of free volume. This contribution investigates the kinetics of hydrogen-metal interactions in gold-containing Pd-based metallic glass (MG) and crystalline Pd nanofilms for two different pore architectures and nonporous substrates. Fully amorphous MGs obtained by physical vapor deposition (PVD) co-sputtering are electrochemically hydrogenated by chronoamperometry. High-resolution (scanning) transmission electron microscopy and corresponding energy-dispersive X-ray analysis after hydrogenation corroborate the existence of several nanometer-sized crystals homogeneously dispersed throughout the matrix. These nanocrystals are induced by PdHx formation, which was confirmed by depth-resolved X-ray photoelectron spectroscopy, indicating an oxide-free inner layer of the nanofilm. With a larger pore diameter and spacing in the substrate (Pore40), the MG attains a frequency-independent impedance at low frequencies (∼500 Hz) with very high Bode magnitude stability accounting for enhanced ionic diffusion. On the contrary, on a substrate with a smaller pore diameter and spacing (Pore25), the MG shows a larger low-frequency (0.1 Hz) capacitance, linked to enhanced ionic transfer in the near-DC region. Hence, the nanoporosity of amorphous and crystalline metallic materials can be systematically adjusted depending on AC- and DC-type applications.

Origin of Electrocatalytic Activity in Amorphous Nickel-Metalloid Electrodeposits.

In transition metal-based alloys, the nonlinearity of the current at large cathodic potentials reduces the credibility of the linear Tafel slopes for the evaluation of electrocatalytic hydrogen activity. High-precision nonlinear fitting at low current densities describing the kinetics of electrochemical reactions due to charge transfer can overcome this challenge. To show its effectiveness, we introduce a glassy alloy with a highly asymmetric energy barrier: amorphous NiP electrocoatings (with different C and O inclusions) via changing the applied DC and pulsed current and NaH2PO2 content. The highest hydrogen evolution reaction (HER) activity with the lowest cathodic transfer coefficient α = 0.130 with high J0 = -1.07 mA cm-2 and the largest surface areas without any porosity are observed for the pulsed current deposition. The calculated α has a direct relation with morphology, composition, chemical state and coating thickness defined by the electrodeposition conditions. Here, a general evaluation criterion with practicality in assessment and high accuracy for electrocatalytic reactions applicable to different metallic alloy systems is presented.

Effective electrocatalytic methanol oxidation of Pd-based metallic glass nanofilms.

Compared to their conventional polycrystalline Pd counterparts, Pd79Au9Si12 (at%) - metallic glass (MG) nanofilm (NF) electrocatalysts offer better methanol oxidation reaction (MOR) in alkaline medium, CO poisoning tolerance and catalyst stability even at high scan rates or high methanol concentrations owing to their amorphous structure without grain boundaries. This study evaluates the influence of scan rate and methanol concentration by cyclic voltammetry, frequency-dependent electrochemical impedance spectroscopy and a related equivalent circuit model at different potentials in Pd-Au-Si amorphous NFs. Structural and compositional differences for the NFs are assessed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray (EDX) mapping and X-ray diffraction (XRD). The ratio of the forward to reverse peak current density ipf/ipb for the MG NFs is ∼2.2 times higher than for polycrystalline Pd NFs, evidencing better oxidation of methanol to carbon dioxide in the forward scan and less poisoning of the electrocatalysts by carbonaceous (e.g. CO, HCO) species. Moreover, the electrochemical circuit model obtained from EIS measurements reveals that the MOR occurring around -100 mV increases the capacitance without any significant change in oxidation resistance, whereas CO2 formation towards lower potentials results in a sharp increase in the capacitance of the Faradaic MOR at the catalyst interface and a slight decrease in the corresponding resistance. These results, together with the high ipf/ipb = 3.37 yielding the minimum amount of carbonaceous species deposited on the thin film during cyclic voltammetry and stability in the alkaline environment, can potentially make these amorphous thin films potential candidates for fuel-cell applications.

Effect of a Single Application of CPP-ACPF Varnish on the Prevention of Erosive Tooth Wear: An AAS, AFM and SMH Study.

PURPOSE: The aim of this study was to investigate the in vitro effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride-containing varnish on prevention enamel erosive tooth wear. MATERIALS AND METHODS: A total of 28 enamel samples were prepared from human molars, divided into four groups: CPP-ACPF varnish, TCP-F varnish, NaF varnish, and deionised water. For the remineralisation process stimulated human pooled saliva was used. After treatment, all enamel samples were exposed to 10 ml of Coca Cola. Ca++ release was determined by atomic absorption spectroscopy (AAS). The surface topography was evaluated by atomic force microscopy (AFM). Surface microhardness of enamel was analysed and SMHR % (surface microhardness reduction ) was calculated. Data were analysed with repeated measures analysis of variance (ANOVA). RESULTS: Deionised water demonstrated a statistically significantly higher Ca+2 release compared to those of groups NaF > fTCP > CPP-ACPF, respectively (p <0.01). All groups measured for root-mean-square-roughness (Rrms) showed a statistically significantly difference of 6 × 6 µm2 and 12 × 12 µm2 enamel area (p <0.05) compared with a negative control group. CPP-ACPF varnish showed rougher surfaces than all remineralisation groups. SMHR % of enamels were as follows: CPP-ACPF < fTCP < NaF < deionised water (p <0.01). CONCLUSION: According to the findings of this study; CPP-ACP containing agents have a statistically statistically significant effect on preventing dental erosion. Among these, CPP-ACPF-containing remineralisation agents have the most effect on the remineralisation process.

Metallic Glass Films with Nanostructured Periodic Density Fluctuations Supported on Si/SiO2 as an Efficient Hydrogen Sorber.

Nanostructured metallic glass films (NMGF) can exhibit surface and intrinsic effects that give rise to unique physical and chemical properties. Here, a facile synthesis and electrochemical, structural, and morphologic characterization of Pd-Au-Si based MGs of approximately 50 nm thickness supported on Si/SiO2 is reported. Impressively, the maximum total hydrogen charge stored in the Pd-Au-Si nanofilm is equal to that in polycrystalline Pd films with 1 µm thickness in 0.1 m H2 SO4 electrolyte. The same NMGF has a volumetric desorption charge that is more than eight times and 25 % higher than that of polycrystalline PdNF and Pd-Cu-Si NMGF with the same thickness supported on Si/SiO2 , respectively. A significant number of nanovoids originating from PdHx crystals, and an increase in the average interatomic spacing is detected in Pd-Au-Si NMGF by high-resolution TEM. Such a high amount of hydrogen sorption is linked to the unique density fluctuations without any chemical segregation exclusively observed for this NMGF.

Effects of Polyvinylpyrrolidone and Ethyl Cellulose in Polyurethane Electrospun Nanofibers on Morphology and Drug Release Characteristics.

OBJECTIVES: Polyurethanes (PUs) are a popular choice for composing nanofibers due to their spinnability, biocompatibility, high chemical stability, and good mechanical and elasticity properties. The desired release behaviors are also achieved by using combinations of PUs and various polymers. In this study, we investigated effects of polyvinylpyrrolidone (PVP) and ethyl cellulose (EC) on PU electrospun nanofibers in terms of morphological structures and drug release characteristics. MATERIALS AND METHODS: Nanofibers were prepared using blends of PU with either EC or PVP in different ratios by electrospinning. The effects of PVP or EC on the morphology and diameter of the prepared nanofibers were examined with scanning electron microscope (SEM). The compatibility of the components used in the formulations of nanofibers was determined by attenuated total reflection (ATR)-fourier-transform infrared (FTIR). Donepezil hydrochloride (DNP), a water soluble compound, was selected as a model drug to examine its release characteristics from both PU/PVP and PU/EC electrospun nanofibers. In vitro drug release studies from electrospun nanofibers were performed according to the method defined in the monograph as the "paddle over disk method" of United States Pharmacopeia 38. RESULTS: The SEM images showed that addition of EC or PVP to PU solutions did not affect the generation of nanofibers, and those formed had a smooth surface without beads in nanoscale. The ATR-FTIR spectra disclosed that EC and PVP were separately incorporated into the PU matrix. The in vitro release data indicated that the presence of EC or PVP in PU nanofibers dramatically changed the release behavior of DNP. PU/EC nanofibers (F4) provided sustained drug release with the Korsmeyer-Peppas drug release kinetic mechanism, in which the release rate was controlled by diffusion of the drug, while all of the PU/PVP nanofibers exhibited fast drug release. CONCLUSION: Overall, these characteristics of PU/EC (10/8) electrospun nanofibers has suggested their potential use as a drug carrier from which water-soluble drug release may occur in a sustained fashion.

Hydrogen storage performance of the multi-principal-component CoFeMnTiVZr alloy in electrochemical and gas-solid reactions.

The single-phase multi-principal-component CoFeMnTiVZr alloy was obtained by rapid solidification and examined by a combination of electrochemical methods and gas-solid reactions. X-ray diffraction and high-resolution transmission electron microscopy analyses reveal a hexagonal Laves-phase structure (type C14). Cyclic voltammetry and electrochemical impedance spectroscopy investigations in the hydrogen absorption/desorption region give insight into the absorption/desorption kinetics and the change in the desorption charge in terms of the applied potential. The thickness of the hydrogen absorption layer obtained by the electrochemical reaction is estimated by high-resolution transmission electron microscopy. The electrochemical hydrogen storage capacity for a given applied voltage is calculated from a series of chronoamperometry and cyclic voltammetry measurements. The selected alloy exhibits good stability for reversible hydrogen absorption and demonstrates a maximum hydrogen capacity of ∼1.9 wt% at room temperature. The amount of hydrogen absorbed in the gas-solid reaction reaches 1.7 wt% at 298 K and 5 MPa, evidencing a good correlation with the electrochemical results.

A Novel Carbon Nanofiber Precursor: Poly(acrylonitrile-co-vinylacetate-co-itaconic acid) Terpolymer.

This study aimed to produce poly(acrylonitrile-co-vinylacetate-co-itaconic acid) (poly(AN-co-VAc-co-IA)) terpolymer as a carbon nanofiber precursor. In this respect, terpolymer samples with different IA amounts were synthesized by free radical polymerization. Produced terpolymer samples were electrospun in order to obtain nanofibers which were then converted to carbon nanofibers. Obtained electrospun nanofibers were oxidized at different temperatures between 200-325 °C. After the oxidation process, carbonization process was applied at 1100 °C in the presence of N2. Viscosity and molecular weight distribution of produced samples were measured with ubbelohde viscosimeter and gel permeation chromatography (GPC), respectively. Thermal features of the ter-polymer samples were analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Spectroscopic characterization of terpolymer samples, oxidized and carbonized nanofibers were performed by Fourier transform infrared-attenuated total reflectance (FTIR-ATR). Original electrospun nanofibers, oxidized and carbonized nanofibers were investigated morphologically by scanning electron microscope (SEM). Inclusion of IA had considerable effect on terpolymer properties and electrospun nanofibers. Moreover, it was proven that oxidation temperature was a crucial parameter for carbon nanofiber production from terpolymer. Both morphology and color of the produced nanofiber mats changed when carbonization process was accomplished. It was observed that poly(AN-co-VAc-co-IA) terpolymer has lower initiation temperature when compared to poly(AN-co-VAc) and poly(AN-co-IA) copolymers, giving the opportunity to obtain carbon nanofibers easier, and poly(AN-co-VAc-co-IA) terpolymer can be used as an effective precursor for carbon nanofiber production.

Oxidative stabilization of polyacrylonitrile nanofibers and carbon nanofibers containing graphene oxide (GO): a spectroscopic and electrochemical study.

In this study, a precursor for carbon nanofibers (CNF) was fabricated via electrospinning and carbonized through a thermal process. Before carbonization, oxidative stabilization should be applied, and the oxidation mechanism also plays an important role during carbonization. Thus, the understanding of the oxidation mechanism is an essential part of the production of CNF. The oxidation process of polyacrylonitrile was studied and nanofiber webs containing graphene oxide (GO) are obtained to improve the electrochemical properties of CNF. Structural and morphological characterizations of the webs are carried out by using attenuated total reflectance Fourier transform infrared spectroscopy and Raman spectroscopy, scanning electron microscopy, atomic force microscopy and transmission electron microscopy. Mechanical tests are performed with a dynamic mechanical analyzer, and thermal studies are conducted by using thermogravimetric analysis. Electrochemical impedance spectroscopy, and cyclic voltammetry are used to investigate capacitive behavior of the products. The proposed equivalent circuit model was consistent with charge-transfer processes taking place at interior pores filled with electrolyte.

Incorporation of growth factor loaded microspheres into polymeric electrospun nanofibers for tissue engineering applications.

Nanofibrous double-layer matrices were prepared by electrospinning technique with the bottom layer formed from PCL (poly-ε-caprolactone)/PLLA (poly-l-lactic acid) nanofibers and the upper layer from PCL/Gelatin nanofibers. Bottom layer was designed to give mechanical strength to the system, whereas upper layer containing gelatin was optimized to improve the cell adhesion. Gelatin microspheres were incorporated in the middle of two layers for controlled growth factor delivery. Successful fabrication of the blend nanofibers were shown by spectroscopy. Scanning electron microscopy results demonstrated that bead-free nanofibers with uniform morphology could be obtained by 10% w/v concentrations of PCL/PLLA and PCL/Gelatin solutions. Microspheres prepared by 15% gelatin concentration and cross-linked with 7.5% glutaraldehyde solution were chosen after in vitro release studies for the incorporation to the double-layer matrices. The optimized conditions were used to prepare fibroblast growth factor-2 (FGF-2) loaded microspheres. Preliminary cell culture studies showed that the FGF-2 could be actively loaded into the microspheres and enhanced the cell attachment and proliferation. The complete system had a slow degradation rate in saline (18% weight loss in 2 months) and it could meanwhile preserve its integrity. This sandwich system prevented microsphere leakage from the scaffold, and the hydrophilic and bioactive nature of the fibers at the upper layer promoted cell attachment to the surface. PLLA/PCL layer, on the other hand, improved the mechanical properties of the system and enabled better handling.

Impedance and morphology of hydroxy- and chloro-functionalized poly(3,4-propylenedioxythiophene) nanostructures.

The new 3,4-propylenedioxythiophenes (ProDOT) bearing hydroxy- or chloro-functionalized side chains of varying length and polarity were synthesized and electropolymerized on single carbon fiber microelectrode (SCFME) using cyclo-voltammetry. Electrochemical impedance spectroscopy (EIS) revealed highest capacitance values for the hydroxy-functionalized Poly 5 carrying a side chain of medium length. The EIS data were fitted with an equivalent electrical circuit giving a good correlation. AFM analysis of the topography showed higher roughness values for Poly 5 than for the two other polymers bearing longer side chains. Due to their reactive end groups the polymers should be useful for post-polymerization functionalization of the electrode surface.

Nanofiber network of electropolymerized 3,4-(2-benzylpropylenedioxy)thiophene on single carbon fiber microelectrode.

Electropolymerization of 3,4-(2-benzylpropylene)-dioxythiophene (ProDOT-Bz) on (approximately 7 microm diameter) single carbon fiber microelectrodes (SCFMEs) in different electrolytes resulted the network of nanofiber structure. Electropolymerization performed in different electrolytes by using cyclovoltammetric technique. Surface morphology of coatings was investigated by Scanning Electron Microscopy (SEM), the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used for the characterization. A linear relationship between peak currents of films with polymerization charge, and capacitances and coating thickness were obtained. The size of nanofiber network (and pores) can be controlled by the scan rate of the cyclovoltammetric process. Electrochemical impedance spectroscopic investigation of these nanostructures has been indicated the capacitive behavior of electrode system. Electrochemical Impedance Spectroscopic characterization (Capacitance) of the PProDOTBz/SCFME consisting cell was simulated at applied potential and parameters explained by equivalent circuit modeling.

Effect of electrolyte on the electropolymerization of 2,2-dibutyl-3,4-propylenedioxythiophene on carbon fiber microelectrodes.

Electrocoating of 2,2 dibutylpropylene dioxythiophene on carbon fiber microelectrodes (CFMEs) in different electrolytes in acetonitrile was performed, and surface morphology and electrochemical impedance spectroscopic investigation has been carried out. Impedance spectra showed the typical form of Z(IM) versus Z(RE) for transmission-line at frequencies 10 Hz, with transition to almost pure capacitive behaviour down to 10 mHz (the lower limit of frequency scan).

Nanoscale surface morphology and monomer concentration dependence on impedance of electrocoated 2,2-dimethyl-3,4-propylene-dioxythiophene on carbon fiber microelectrode.

Poly(2,2-Dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) thin films have been cyclovoltametrically coated onto carbon fiber microelectrode (CFME) as an active functionalized microelectrode. An electrochemical impedance spectroscopic study on the prepared electrodes is reported in this paper which electropolymerization performed under different initial monomer concentrations. The electrochemical impedance data fitted to equivalent circuit model, used to find out numerical values of the proposed components. Effect of the parameters on the capacitive behavior of the (PProDOT-Me2) coated carbon fiber microelectrode and morphology of films obtained by AFM and SEM was discussed. Highly porous coating was obtained at 100 mV/s scan rate and 10 cycles. EDX and ATR-FTIR results indicated the doping of anion of electrolyte due to formation of polaronic and bipolaronic sites. The presence of surface functional groups were determined by ATR-FTIR. Nanoscale conjugated polymer modified carbon fiber microelectrodes exhibited high capacitance of approximately 90 degrees phase angle, and vertical line in Nyquist plot. The capacitive behavior of CFME was increased by this very thin film coating of PProDOT-Me2. The electroactivity of Poly 2,2-Dimethyl-3,4-propylenedioxythiophene on the carbon fiber microelectrode open the possibility of using these coated electrodes for electrochemical microsupercapacitors and biosensor electrodes.

Nanoscale characterization of carbazole-indole copolymers modified carbon fiber surfaces.

Polycarbazole, carbazole and indole containing copolymers were electrochemically coated onto carbon fiber. The resulting polymers and copolymers were characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Characterization of the thin polymer films were performed on the polymer-coated surface of the carbon fiber. Therefore, the results obtained could elucidate the relationship between the initial feed monomer ratio, the resulting polymer/copolymer film morphology and the surface structure formed. The thickness increase (in diameter) was 0.3 and 0.9 microm, for two different composition of carbazole/indole on the carbon fiber. The carbon fibers coated with copolymer thin films were from 6.5 to 8.2 microm in diameter (from AFM measurement).