Electrospun cobalt-doped 2D-MoSe2/polypyrrole hybrid-based carbon nanofibers as electrochemical sensing platforms.

A novel cobalt-doped two-dimensional molybdenum diselenide/polypyrrole hybrid-based carbon nanofiber (Co/MoSe2/PPy@CNF) was prepared using the hydrothermal method followed by electrospinning technique. The structural and morphological properties of the 2D-TMD@CNF-based hybrids were characterized through X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and transmission electron microscopy (TEM). The Co-MoSe2/PPy@CNF exhibited large surface area, porous structure, and improved active sites due to the synergistic effect of the components. The electrochemical and electrocatalytic characteristics of the 2D-TMD@CNF-modified electrodes were also investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Co/MoSe2/PPy@CNF electrode was used as an electrochemical sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) and showed enhanced catalytic activity and sensitivity. Using DPV measurements, the Co/MoSe2/PPy@CNF demonstrated wide linear ranges of 30-3212 µM for AA, 1.2-536 µM for DA, and 10-1071 µM for UA with low detection limits of 6.32, 0.45, and 0.81 µM, respectively. The developed sensor with the Co/MoSe2/PPy@CNF-modified electrode was also applied to a human urine sample and gave recoveries ranging from 94.0 to 105.5% (n = 3) for AA, DA, and UA. Furthermore, the Co/MoSe2/PPy@CNF-based sensor exhibited good selectivity and reproducibility for the detection of AA, DA, and UA.

A synergistic effect of the ion beam sputtered NiOxhole transport layer and MXene doping on inverted perovskite solar cells.

The synergistic effect of high-quality NiOxhole transport layers (HTLs) deposited by ion beam sputtering on ITO substrates and the Ti3C2TxMXene doping of CH3NH3PbI3(MAPI) perovskite layers is investigated in order to improve the power conversion efficiency (PCE) of p-i-n perovskite solar cells (PSCs). The 18 nm thick NiOxlayers are pinhole-free and exhibit large-scale homogeneous surface morphology as revealed by the atomic force microscopy (AFM). The grazing-incidence x-ray diffraction showed a 0.75% expansion of the face-centered cubic lattice, suggesting an excess of oxygen as is typical for non-stoichiometric NiOx. The HTLs were used to fabricate the PSCs with MXene-doped MAPI layers. A PSC with undoped MAPI layer served as a control. The size of MAPI polycrystalline grains increased from 430 ± 80 nm to 620 ± 190 nm on the doping, as revealed by AFM. The 0.15 wt% MXene doping showed a 14.3% enhancement in PCE as compared to the PSC with undoped MAPI. The energy-resolved electrochemical impedance spectroscopy revealed one order of magnitude higher density of defect states in the band gap of MXene-doped MAPI layer, which eliminated beneficial effect of reduced total area of larger MAPI grain boundaries, decreasing short-circuit current. The PCE improvement is attributed to a decrease of the work function from -5.26 eV to -5.32 eV on the MXene doping, which increased open-circuit voltage and fill factor.

Size effect of hybrid carbon nanofillers on the synergetic enhancement of the properties of HDPE-based nanocomposites.

High-density polyethylene (HDPE)-based hybrid nanocomposites containing graphene nanoplatelets (GnPs) and multiwall carbon nanotubes (MWCNTs) were fabricated using melt mixing followed by compression molding. The influences of size and weight ratio of both carbon-based nanofillers on the electrical, thermal, and mechanical properties of hybrid nanocomposites were evaluated. This study proves that the size and weight ratio of carbon-based nanofillers play a critical role in determining these properties. The optimum size and weight ratio of GnPs and MWCNTs are determined at the maximum achieved enhancement for each property. The HDPE-based nanocomposites containing GnPs with larger surface area and MWCNTs with higher aspect ratio display the highest electrical conductivity at GnPs/MWCNTs weight ratio of 2/3. The combination of GnPs with larger surface area and MWCNTs with lower aspect ratio provides the maximum Young's modulus enhancement of hybrid nanocomposites at 1/4 weight ratio of GnPs and MWCNTs. The nanocomposite containing GnPs with the largest lateral size and MWCNTs with a higher aspect ratio at a 3/2 weight ratio exhibits the highest thermal conductivity. Also, at around the percolation threshold of GnPs, the incorporation of MWCNTs with larger aspect ratio into the HDPE-based nanocomposites containing GnPs with the largest lateral size shows a distinct synergic effect on the thermal conductivity and Young's modulus, while an additive effect on the electrical conductivity and thermal stability.

Strain Sensing Coatings for Large Composite Structures Based on 2D MXene Nanoparticles.

Real-time strain monitoring of large composite structures such as wind turbine blades requires scalable, easily processable and lightweight sensors. In this study, a new type of strain-sensing coating based on 2D MXene nanoparticles was developed. A Ti3C2Tz MXene was prepared from Ti3AlC2 MAX phase using hydrochloric acid and lithium fluoride etching. Epoxy and glass fibre-reinforced composites were spray-coated using an MXene water solution. The morphology of the MXenes and the roughness of the substrate were characterised using optical microscopy and scanning electron microscopy. MXene coatings were first investigated under various ambient conditions. The coating experienced no significant change in electrical resistance due to temperature variation but was responsive to the 301-365 nm UV spectrum. In addition, the coating adhesion properties, electrical resistance stability over time and sensitivity to roughness were also analysed in this study. The electromechanical response of the MXene coating was investigated under tensile loading and cyclic loading conditions. The gauge factor at a strain of 4% was 10.88. After 21,650 loading cycles, the MXene coating experienced a 16.25% increase in permanent resistance, but the response to loading was more stable. This work provides novel findings on electrical resistance sensitivity to roughness and electromechanical behaviour under cyclic loading, necessary for further development of MXene-based nanocoatings. The advantages of MXene coatings for large composite structures are processability, scalability, lightweight and adhesion properties.

Molecular targeting of bioconjugated graphene oxide nanocarriers revealed at a cellular level using label-free Raman imaging.

Two-dimensional materials as graphene oxide (GO) are able to accommodate labels as well as toxins for diagnostics and therapy, respectively. The transmembrane protein carbonic anhydrase (CA IX) is one of the molecules selectively expressed by tumor cells. Here, we demonstrate bioconjugation of GO to biotinylated M75 antibody highly selective towards CA IX. Based on a model system, binding between the bioconjugated GO-M75 and Madin-Darby Canine Kidney (MDCK) cells was evaluated. As proven by fluorescence-activated cell sorting, higher intake was observed for GO-M75 towards MDCK cells ectopically expressing CA IX protein on their surface when compared to control MDCK. In particular, we were able to localize GO nanocarrier crossing the membrane during endocytosis, thanks to the optical cross-sectioning of living cells in real-time employed the label-free confocal Raman microscopy. The increased affinity of the prepared GO-M75 molecular complexes validates the use of two-dimensional materials for future strategies of targeted cancer treatment.

An elevated concentration of MoS2 lowers the efficacy of liquid-phase exfoliation and triggers the production of MoOx nanoparticles.

It is generally accepted that liquid-phase exfoliation (LPE) enables large-scale production of few-layer MoS2 flakes. In our work, we studied in detail few-layer MoS2 oxidation in the course of standard LPE in a water/ethanol solution. We demonstrate that an increase of the initial MoS2 concentration above a certain threshold triggers a pronounced oxidation and the exfoliation process starts to produce MoOx nanoparticles. A subsequent decrease of the water pH along with an increased content of SO42- suggests an oxidation scenario of few-layer MoS2 oxidation towards MoOx nanoparticles. Moreover, the lowered pH leads to agglomeration and sedimentation of the few-layer MoS2 flakes, which significantly lowers their production yield. We employed a large number of physico-chemical techniques to study the MoS2-to-MoOx transformation and found a threshold value of 10 mg ml-1 of the initial MoS2 concentration to trigger this transformation.

Remarkable differences in the voltammetric response towards hydrogen peroxide, oxygen and Ru(NH3)63+ of electrode interfaces modified with HF or LiF-HCl etched Ti3C2Tx MXene.

An electrochemical study was performed on the behavior of Ti3C2Tx MXenes prepared by using either HF (MXene1) or LiF/HCl as etchants (MXene2). The use of two redox probes indicates the presence of a higher negative charge density on MXene2 in comparison to MXene1. The characterization of two nanomaterials shows that titanium and fluoride are present higher by one order of magnitude at the interface of MXene2, compared to MXene1. The high Ti and F content is accompanied by a 82-fold larger (249 µA·cm-2 vs. 5.64 µA·cm-2) anodic peak at the peak potential near 0.4 V (vs. Ag/AgCl). Similarly, the peak current on MXene2 is 317-fold higher for the oxygen reduction at pH 7.0 (at a voltage of -0.84 V) and 215-fold higher for the reduction of H2O2 at -0.89 V, when compared to MXene1. Graphical abstractDifference in electrochemical behavior of MXene prepared by HF (MXene1) and LiF/HCl (MXene2) as etchants.

Label-free tracking of nanosized graphene oxide cellular uptake by confocal Raman microscopy.

Graphene oxide (GO), a partially oxidized two-dimensional allotrope of carbon, is an attractive nanocarrier for cancer diagnostics and therapy. The nanometer-sized GO is known to permeate cell membranes. Herein we studied the cellular uptake pathways of GO nanoflakes by cancer and non-cancerous cell lines. By employing confocal Raman imaging, we were able to track the GO cellular uptake in living cells (C33 and MDCK) without any additional fluorescent or plasmonic labels. This specific progress in label-free Raman imaging of GO facilitates the monitoring of nanoflakes at the cellular level.

Efficient Covalent Modification of Multiwalled Carbon Nanotubes with Diazotized Dyes in Water at Room Temperature.

Tetrafluoroborate salts of diazotized Azure A (AA-N2+), Neutral Red (NR-N2+) and Congo Red (CR-N2+) dyes were prepared and reacted with multiwalled carbon nanotubes (MWCNTs) at room temperature, in water without any reducing agent. The as-modified MWCNTs were examined by IRATR, Raman spectroscopy, XPS, TGA, TEM, and cyclic voltammetry. The diazonium band located at ∼2350 cm-1 in the diazotized dye IR spectra vanished after attachment to the nanotubes whereas the Raman D/G peak ratio slightly increased after dye covalent attachment at a high initial diazonium/CNT mass ratio. XPS measurements show the loss of F 1s from the BF4- anion together with a clear change in the high-resolution C 1s region from the modified nanotubes. Thermogravimetric analyses proved substantial mass loadings of the organic grafts leveling off at 40.5, 34.3, and 50.7 wt % for AA, NR, and CR, respectively. High-resolution TEM pictures confirmed the presence of 1.5-7-nm-thick continuous amorphous layers on the nanotubes assigned to the aryl layers from the dyes. Cyclic voltammetry studies in acetonitrile (ACN) confirmed the grafting of the dyes; the latter retain their electrochemical behavior in the grafted state. The experimental results correlate remarkably well with quantum chemical calculations that indicate high binding energies between the dyes and the CNTs accounting for true covalent bonding (140-185 kJ/mol with the CNT-aryl distance <1.6 nm), though attachment by π stacking also contributes to obtaining stable hybrids. Finally, the pH-responsive character of the robust hybrids was demonstrated by a higher degree of protonation of Neutral Red-grafted CNTs at pH 2 compared to that of the neutral aqueous medium. This work demonstrates that diazotized dyes can be employed for the surface modification of MWCNTs in a very simple and efficient manner in water and at room temperature. The hybrids could be employed for many purposes such as optically pH-responsive materials, biosensors, and optothermal composite actuators to name a few.

Fast low-temperature plasma reduction of monolayer graphene oxide at atmospheric pressure.

We report on an ultrafast plasma-based graphene oxide reduction method superior to conventional vacuum thermal annealing and/or chemical reduction. The method is based on the effect of non-equilibrium atmospheric-pressure plasma generated by the diffuse coplanar surface barrier discharge in proximity of the graphene oxide layer. As the reduction time is in the order of seconds, the presented method is applicable to the large-scale production of reduced graphene oxide layers. The short reduction times are achieved by the high-volume power density of plasma, which is of the order of 100 W cm-3. Monolayers of graphene oxide on silicon substrate were prepared by a modified Langmuir-Schaefer method and the efficient and rapid reduction by methane and/or hydrogen plasma was demonstrated. The best results were obtained for the graphene oxide reduction in hydrogen plasma, as verified by x-ray photoelectron spectroscopy and Raman spectroscopy.

Gross morphology and adhesion-associated physical properties of Drosophila larval salivary gland glue secretion.

One of the major functions of the larval salivary glands (SGs) of many Drosophila species is to produce a massive secretion during puparium formation. This so-called proteinaceous glue is exocytosed into the centrally located lumen, and subsequently expectorated, serving as an adhesive to attach the puparial case to a solid substrate during metamorphosis. Although this was first described almost 70 years ago, a detailed description of the morphology and mechanical properties of the glue is largely missing. Its main known physical property is that it is released as a watery liquid that quickly hardens into a solid cement. Here, we provide a detailed morphological and topological analysis of the solidified glue. We demonstrated that it forms a distinctive enamel-like plaque that is composed of a central fingerprint surrounded by a cascade of laterally layered terraces. The solidifying glue rapidly produces crystals of KCl on these alluvial-like terraces. Since the properties of the glue affect the adhesion of the puparium to its substrate, and so can influence the success of metamorphosis, we evaluated over 80 different materials for their ability to adhere to the glue to determine which properties favor strong adhesion. We found that the alkaline Sgs-glue adheres strongly to wettable and positively charged surfaces but not to neutral or negatively charged and hydrophobic surfaces. Puparia formed on unfavored materials can be removed easily without leaving fingerprints or cascading terraces. For successful adhesion of the Sgs-glue, the material surface must display a specific type of triboelectric charge. Interestingly, the expectorated glue can move upwards against gravity on the surface of freshly formed puparia via specific, unique and novel anatomical structures present in the puparial's lateral abdominal segments that we have named bidentia.

Anticorrosion and Antimicrobial Tannic Acid-Functionalized Ti-Metallic Glass Ribbons for Dental Abutment.

In this study, a recently reported Ti-based metallic glass (MG), without any toxic element, but with a significant amount of metalloid (Si-Ge-B, 18 atom %) and minor soft element (Sn, 2 atom %), was produced in ribbon form using conventional single-roller melt-spinning. The produced Ti60Zr20Si8Ge7B3Sn2 ribbons were investigated by differential scanning calorimetry and X-ray diffraction to confirm their amorphous structure, and their corrosion properties were further investigated by open-circuit potential and cyclic polarization tests. The ribbon's surface was functionalized by tannic acid, a natural plant-based polyphenol, to enhance its performance in terms of corrosion prevention and antimicrobial efficacy. These properties can potentially be exploited in the premucosal parts of dental implants (abutments). The Folin and Ciocalteu test was used for the quantification of tannic acid (TA) grafted on the ribbon surface and of its redox activity. Fluorescent microscopy and ζ-potential measurements were used to confirm the presence of TA on the surfaces of the ribbons. The cytocompatibility evaluation (indirect and direct) of TA-functionalized Ti60Zr20Si8Ge7B3Sn2 MG ribbons toward primary human gingival fibroblast demonstrated that no significant differences in cell viability were detected between the functionalized and as-produced (control) MG ribbons. Finally, the antibacterial investigation of TA-functionalized samples against Staphylococcus aureus demonstrated the specimens' antimicrobial properties, shown by scanning electron microscopy images after 24 h, presenting a few single colonies remaining on their surfaces. The thickness of bacterial aggregations (biofilm-like) that were formed on the surface of the as-produced samples reduced from 3.5 to 1.5 µm.

SERS Performance of Ti3C2Tx MXene-Based Substrates Correlates with Surface Morphology.

The surface-enhanced Raman scattering (SERS) properties of low-dimensional semiconducting MXene nanoflakes have been investigated over the last decade. Despite this fact, the relationship between the surface characteristics and SERSing performance of a MXene layer has yet to be comprehensively investigated and elucidated. This work shows the importance of surface morphology on the overall SERS effect by studying few-layer Ti3C2Tx MXene-based SERS substrates fabricated by vacuum-assisted filtration (VAF) and spray coating on filter paper. The VAF deposition results in a dense MXene layer suitable for SERS with high spot-to-spot and substrate-to-substrate reproducibility, with a significant limit of detection (LoD) of 20 nM for Rhodamine B analyte. The spray-coated MXenes film revealed lower uniformity, with a LoD of 50 nM for drop-casted analytes. Moreover, we concluded that the distribution of the analyte deposited onto the MXene layer is affected by the presence of MXene aggregates created during the deposition of the MXene layer. Accumulation of the analyte molecules in the vicinity of MXene aggregates was observed for drop-casted deposition of the analyte, which affects the resulting SERS enhancement. Ti3C2Tx MXene layers deposited on filter paper by VAF offer great potential as a cost-effective, easy-to-manufacture, yet robust, platform for sensing applications.

Ultrasensitive impedimetric lectin biosensors with efficient antifouling properties applied in glycoprofiling of human serum samples.

Ultrasensitive impedimetric lectin biosensors recognizing different glycan entities on serum glycoproteins were constructed. Lectins were immobilized on a novel mixed self-assembled monolayer containing 11-mercaptoundecanoic acid for covalent immobilization of lectins and betaine terminated thiol to resist nonspecific interactions. Construction of biosensors based on Concanavalin A (Con A), Sambucus nigra agglutinin type I (SNA), and Ricinus communis agglutinin (RCA) on polycrystalline gold electrodes was optimized and characterized with a battery of tools including electrochemical impedance spectroscopy, various electrochemical techniques, quartz crystal microbalance (QCM), Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) and compared with a protein/lectin microarray. The lectin biosensors were able to detect glycoproteins from 1 fM (Con A), 10 fM (Ricinus communis agglutinin (RCA), or 100 fM (SNA) with a linear range spanning 6 (SNA), 7 (RCA), or 8 (Con A) orders of magnitude. Furthermore, a detection limit for the Con A biosensor down to 1 aM was achieved in a sandwich configuration. A nonspecific binding of proteins for the Con A biosensor was only 6.1% (probed with an oxidized invertase) of the signal toward its analyte invertase and a negligible nonspecific interaction of the Con A biosensor was observed in diluted human sera (1000×), as well. The performance of the lectin biosensors was finally tested by glycoprofiling of human serum samples from healthy individuals and those having rheumatoid arthritis, which resulted in a distinct glycan pattern between these two groups.

Insight into the Li-Storage Property of Surface-Modified Ti2Nb10O29 Anode Material for High-Rate Application.

Ti-based anode materials are considered to be an alternative to graphite anodes to accomplish high-rate application requirements. Ti2Nb10O29 (TNO15) has attracted much attention due to its high lithium storage capacity through the utilization of multiple redox couples and a suitable operating voltage window of 1.0 to 2.0 V vs Li/Li+. However, poor intrinsic electronic conductivity has limited the futuristic applicability of this material to the battery anode. In this work, we report the modification of TNO15 by introducing oxygen vacancies and using few-layered carbon and copper coatings on the surface to improve its Li+ storage property. With the support of the galvanostatic intermittent titration technique (GITT), we found that the diffusion coefficient of carbon/copper coated TNO15 is 2 orders of magnitude higher than that of the uncoated sample. Here, highly conductive copper metal on the surface of the carbon-coated oxygen-vacancy-incorporated TNO15 increases the overall electronic and ionic conductivity. The prepared TNO15-800-C-Cu-700 half-cell shows a significant rate capability of 92% when there is a 10-fold increase in the current density. In addition, the interconnected TNO15 nanoparticles create a porous microsphere structure, which enables better Li-ion transportation during charge/discharge process, and experiences an enhancement after the carbon and copper coating on the surface of the primary TNO15 nanocrystallites.

Preparation and properties of novel binary and ternary highly amorphous poly(vinyl alcohol)-based composites with hybrid nanofillers.

Smart protective coatings and devices are currently of great interest. In particular, they can absorb or reflect harmful waves of electromagnetic interference (EMI). In this work, novel binary and ternary composites with highly amorphous poly(vinyl alcohol) (HAVOH) as a matrix and single-walled carbon nanotubes (SWCNTs) and MXenes as nanofillers were prepared. HAVOH is a recently patented kind of poly(vinyl alcohol) (PVOH) that was modified with diol monomers. MXenes are a new type of inorganic two-dimensional (2D) nanoparticle consisting of carbides, nitrides and carbonitrides. Three series of composites, HAVOH/SWCNTs, HAVOH/MXenes and HAVOH/SWCNTs/MXenes, were prepared using the solvent casting method. Samples were tested with various methods to study their structure, electrical properties, thermal behavior and EMI-shielding properties. HAVOH/3.0 wt.% SWCNTs/3.0 wt.% MXene specimens revealed a shielding effectiveness of 55 dB, which is 122 times better than that of the neat matrix. These results are promising for the fabrication of films with protective effects against EMI.

Effect of surfactants and manufacturing methods on the electrical and thermal conductivity of carbon nanotube/silicone composites.

The effect of ionic surfactants and manufacturing methods on the separation and distribution of multi-wall carbon nanotubes (CNTs) in a silicone matrix are investigated. The CNTs are dispersed in an aqueous solution of the anionic surfactant dodecylbenzene sulfonic acid (DBSA), the cationic surfactant cetyltrimethylammonium bromide (CTAB), and in a DBSA/CTAB surfactant mixture. Four types of CNT-based composites of various concentrations from 0 to 6 vol.% are prepared by simple mechanical mixing and sonication. The morphology, electrical and thermal conductivity of the CNT-based composites are analyzed. The incorporation of both neat and modified CNTs leads to an increase in electrical and thermal conductivity. The dependence of DC conductivity versus CNT concentration shows percolation behaviour with a percolation threshold of about 2 vol.% in composites with neat CNT. The modification of CNTs by DBSA increases the percolation threshold to 4 vol.% due to the isolation/separation of individual CNTs. This, in turn, results in a significant decrease in the complex permittivity of CNT–DBSA-based composites. In contrast to the percolation behaviour of DC conductivity, the concentration dependence of thermal conductivity exhibits a linear dependence, the thermal conductivity of composites with modified CNTs being lower than that of composites with neat CNTs. All these results provide evidence that the modification of CNTs by DBSA followed by sonication allows one to produce composites with high homogeneity.

In Situ Deformation Monitoring of 3D Woven Composite T-Profile Using MXene Nanoparticles.

The aim of this study was to develop a process-efficient smart three-dimensional (3D) woven composite T-profile by depositing MXene nanoparticles at the junction for sensing damage and deformation at the junction. Such smart composites could find application in the online health monitoring of complex-shaped parts. The composites were manufactured by infusing epoxy resin in a single-layer fabric T-profile preform, woven in folded form on a dobby shuttle loom using 300 tex glass roving. The chemically etched Ti3C2Tz MXene nanoparticles were dispersed in deionised water and 10 layers were sprayed at the junction of the composite to form a conductive coating. The MXene-coated composite T-profile specimens were subjected to tensile and fatigue loading to study the electromechanical response of the MXene coating to applied displacement. The results showed that the MXene coating was able to sense the sample deformation till ultimate failure of the composite. The MXene coating was also able to effectively sense the tensile-tensile fatigue loading, carried out at 2000 cycles and 4000 cycles for a 50 N-0.5 Hz and a 100 N-1 Hz load-frequency combination, respectively, while being sensitive to the overall deformation of the composite. The smart complex-shaped composites developed in this work were capable of monitoring their health under tensile and fatigue loading in real time.

Scalable MXene and PEDOT-CNT Nanocoatings for Fibre-Reinforced Composite De-Icing.

In this study, the de-icing performance is investigated between traditional carbon fibre-based coatings and novel MXene and poly(3,4-ethylenedioxythiophene)-coated single-walled carbon nanotube (PEDOT-CNT) nanocoatings, based on simple and scalable coating application. The thickness and morphology of the coatings are investigated using atomic force microscopy and scanning electron microscopy. Adhesion strength, as well as electrical properties, are evaluated on rough and glossy surfaces of the composite. The flexibility and electrical sensitivity of the coatings are studied under three-point bending. Additionally, the influence of ambient temperature on coating's electrical resistance is investigated. Finally, thermal imaging and Joule heating are analysed with high-accuracy infrared cameras. Under the same power density, the increase in average temperature is 84% higher for MXenes and 117% for PEDOT-CNT, when compared with fibre-based coatings. Furthermore, both nanocoatings result in up to three times faster de-icing. These easily processable nanocoatings offer fast and efficient de-icing for large composite structures such as wind turbine blades without adding any significant weight.

Morphological, Mechanical and Gas Penetration Properties of Elastomer Composites with Hybrid Fillers.

Ethylene-propylene-diene monomer (EPDM)-based composites including four different types of graphene nanoplatelets (GnPs) were prepared to evaluate the size effects of GnPs in terms of both specific surface area and lateral size on the morphological, mechanical, and viscoelastic properties, swelling ratio, crosslink density, and oxygen permeability. EPDM-based hybrid composites with GnPs and carbon black (CB) fillers were prepared, with the concentrations of 20 and 50 phr of CB and GnPs up to 7 phr. All samples were prepared using the melt mixing method, followed by compression molding. The specific surface area of GnPs is a more important key factor for mechanical and viscoelastic properties than its lateral size. The presence of GnPs leads to a decrease in the swelling ratio and oxygen permeability of the matrix while an increase in the crosslinking density. For a given specific surface area of GnPs (170 m2/g) and the same thickness (5 nm), the optimum lateral size for mechanical properties, swelling ratio, and crosslinking density is about 30 µm. There is a distinct synergic effect on the mentioned properties when hybrid fillers are used. For hybrid composites, the optimum total and each filler concentration are found to be important for achieving the best performance in terms of mechanical properties, swelling ratio, and crosslink density.