Graphene and polytetrafluoroethylene synergistically improve the tribological properties and adhesion of nylon 66 coatings

Abstract In this work, we exploit the bidimensional structure and high stiffness of graphene to improve the tribological response of nylon-based composites. Graphene nanoplatelets, coupled with polytetrafluoroethylene microparticles, synergistically improve the friction coefficient and wear rate, as well as the adhesion to the substrate. The enhancement, as high as threefold for both friction and wear rate at the optimal graphene concentration (0.5% in weight), depends upon the formation of a continuous, robust transfer film with the steel rubbing counterpart, as shown by Raman measurements. The graphene-nylon coating also shows three-fold improved adhesion to the underlying substrate, attributed to the high surface energy of graphene

Keratin–cinnamon essential oil biocomposite fibrous patches for skin burn care

Keratin based electrospun fibres containing cinnamon essential oil are highly antioxidant and antibacterial, and promote reduced tissue inflammation after skin burns

Investigation of the electro-spinnability of alginate solutions containing gold precursor HAuCl4

Alginate nanofibers with an average diameter of 75 nm have been prepared by the electrospinning process. In addition, the spinnability of the solutions in the presence of the gold precursor HAuCl4 was investigated. At low concentrations of HAuCl4 well-formed nanofibers were produced, whereas as its concentration increases the nanofibrous mats present an increased number of bead-like defects. Herein, the in situ preparation of gold nanoparticles (Au NPs) is discussed since sodium alginate (SA) acts as the reducing agent and a mechanism is proposed in order to explain the bead-effect as well as the surface morphology of the alginate fibers decorated with Au NPs

Graphene nanoplatelets render poly(3-hydroxybutyrate) a suitable scaffold to promote neuronal network development

The use of composite biomaterials as innovative bio-friendly neuronal interfaces has been poorly developed so far. Smart strategies to target neuro-pathologies are currently exploiting the mixed and complementary characteristics of composite materials to better design future neural interfaces. Here we present a polymer-based scaffold that has been rendered suitable for primary neurons by embedding graphene nanoplatelets (GnP). In particular, the growth, network formation, and functionality of primary neurons on poly(3-hydroxybutyrate) [P(3HB)] polymer supports functionalized with various concentrations of GnP were explored. After growing primary cortical neurons onto the supports for 14 days, all specimens were found to be biocompatible, revealing physiological growth and maturation of the neuronal network. When network functionality was investigated by whole patch-clamp measurements, pure P(3HB) led to changes in the action potential waveform and reduction in firing frequency, resulting in decreased neuronal excitability. However, the addition of GnP to the polymer matrix restored the electrophysiological parameters to physiological values. Interestingly, a low concentration of graphene was able to promote firing activity at a low level of injected current. The results indicate that the P(3HB)/GnP composites show great potential for electrical interfacing with primary neurons to eventually target central nervous system disorders

Zwitterionic nanofibers of super-glue for transparent and biocompatible multi-purpose coatings

Here we show that macrozwitterions of poly(ethyl 2-cyanoacrylate), commonly called Super Glue, can easily assemble into long and well defined fibers by electrospinning. The resulting fibrous networks are thermally treated on glass in order to create transparent coatings whose superficial morphology recalls the organization of the initial electrospun mats. These textured coatings are characterized by low liquid adhesion and anti-staining performance. Furthermore, the low friction coefficient and excellent scratch resistance make them attractive as solid lubricants. The inherent texture of the coatings positively affects their biocompatibility. In fact, they are able to promote the proliferation and differentiation of myoblast stem cells. Optically-transparent and biocompatible coatings that simultaneously possess characteristics of low water contact angle hysteresis, low friction and mechanical robustness can find application in a wide range of technological sectors, from the construction and automotive industries to electronic and biomedical devices

Thin film growth of delafossite-related derivative β-NaFeO2 on a ZnO layer by pulsed laser deposition.

Despite the fact there is a plethora of magnetic delafossite compounds in the bulk polycrystalline phase, so far,only a few of them have been fabricated as thin films. The challenges in the fabrication of delafossite thin films are imposed by the phase purity and stability of the composition related with the preparation conditions. Here we report the growth of a new delafossite related derivative thin film, a sodium iron oxide of the β-NaFeO2 phase, grown on a ZnO seed layer by pulsed laser deposition, using as target a single phase polycrystalline powder of β-NaFeO2. The purity of the thin films has been verified with X-ray diffraction, Scanning electron and Atomic Force Microscopy as well as Fourier Transform Infrared Spectroscopy. The crucial parameter for the growth of the thin films has been the partial oxygen pressure, as the β-NaFeO2 is obtained at 2 Pa. Applyinghigher or lower pressures resulted in the formation the hematite and maghemite iron oxides as secondary phases, as indicated by X-ray diffraction patterns. SEM and AFM studies confirm a good two dimensional growth for the pure phase β-NaFeO2, whereas FT-IR measurements revealed characteristic β-ΝaFeO2 bands

Polymer-based fibrous hybrid membranes by in situ synthesis of inorganic nanoparticles

We present an innovative method to fabricate hybrid polymer/inorganic nanoparticles (NPs) fibrous membranes. In particular, the proposed method is based on a solvent-free two-step process. The first step deals with the electrospinning of a polymer/NPs precursor solution, while in the second step the in situ synthesis of NPs takes place, by mean of a thermally-induced solid-state reaction. Such method (schem in Figure 1) allows to obtain fibres homogeneously decorated with NPs, overcoming the typical particles aggregation that affects nanocomposites prepared by conventional mixing methods. In addition, the in situ formation permits to have exposed NPs on the fibres surface, which combined with high surface area offered by the fibrous structure result in a multifunctional material. Herein, two examples of hybrid nanocomposite membranes obtained by this approach are reported. PMMA membranes modified with ZnO NPs have shown reversible UV-switchable wettability and permeability, improved thermal stability and antibacterial activity, which can be controlled simply varying the filler content.[1] On the other hand, PVDF/CeO2/Au fibrous nanocomposites have shown photocatalytic degradation activity induced by visible light, thanks to the modification with Au NPs, which results in a narrowing effect of the CeO2 bandgap. The Au NPs also increase the Ce+3/Ce+4 ratio that greatly enhances the radical scavenging activity of CeO2.[2] In conclusion, the versatility of the presented multifunctional membranes as well as the light-weight and flexibility offered by the polymeric fibres, make these materials valuable alternatives to the nowadays existing systems based on NPs supported on ceramic materials. Furthermore, the present findings demonstrate that the proposed fabrication method is a promising and straightforward approach to obtain polymer-based hybrid membranes for several applications such as filtration, wound management and water purification, among others. [1] Morselli D. et al., Thermally-induced in situ growth of ZnO nanoparticles in polymeric fibrous membranes, Composites Science and Technology 149 (2017) 11-19 [2] Morselli D. et al., Ceria/gold nanoparticles in situ synthesized on polymeric membranes with enhanced photocatalytic and radical scavenging activity, accepted on ACS Applied Nano Materials (2018

Paper sensors based on fluorescence changes of carbon nanodots for optical detection of nanomaterials

This article belongs to the Special Issue Sustainable Development of Nanotechnologies: Risks and Opportunities for Occupational Safety and Health.A paper sensor was designed in order to detect the presence of nanomaterials, such as ZnO and silica nanoparticles, as well as graphene nanoplatelets (GnP), based on fluorescence changes of carbon nanodots. Paper strips were functionalized with carbon nanodots using polyvinyl alcohol (PVA) as binder. The carbon nanodots were highly fluorescent and, hence, rendered the (cellulosic) paper stripes emissive. In the presence of silica and ZnO nanoparticles, the fluorescence emission of the carbon nanodots was quenched and the emission decay was shortened, whereas in the presence of GnP only emission quenching occurred. These different photoluminescence (PL) quenching mechanisms, which are evident from lifetime measurements, convey selectivity to the sensor. The change in fluorescence of the carbon dot-functionalized paper is also evident to the naked eye under illumination with a UV lamp, which enables easy detection of the nanomaterials. The sensor was able to detect the nanomaterials upon direct contact, either by dipping it in their aqueous dispersions, or by sweeping it over their powders. The use of the proposed optical sensor permits the detection of nanomaterials in a straightforward manner, opening new ways for the development of optical sensors for practical applications.This research was part of the Project “Nano and Key enabling technologies within the innovation processes: risk and opportunities in occupational settings by prevention through design (NanoKey__EPTR0003))”, funded by the Italian Workers’ Compensation Authority (INAIL) and coordinated in cooperation between the INAIL Department of Occupational and Environmental Medicine Epidemiology and Hygiene, and the Italian Institute of Technology (IIT).Peer reviewe

Self-Cleaning Organic/Inorganic Photo-Sensors

We present the fabrication of a multifunctional, hybrid organic–inorganic micropatterned device, which is capable to act as a stable photosensor and, at the same time, displaying inherent superhydrophobic self-cleaning wetting characteristics. In this framework several arrays of epoxy photoresist square micropillars have been fabricated on n-doped crystalline silicon substrates and subsequently coated with a poly­(3-hexylthiophene-2,5-diyl) (P3HT) layer, giving rise to an array of organic/inorganic p–n junctions. Their photoconductivity has been measured under a solar light simulator at different illumination intensities. The current–voltage (<i>I</i>–<i>V</i>) curves show high rectifying characteristics, which are found to be directly correlated with the illumination intensity. The photoresponse occurs in extremely short times (within few tens of milliseconds range). The influence of the interpillar distance on the <i>I</i>–<i>V</i> characteristics of the sensors is also discussed. Moreover, the static and dynamic wetting properties of these organic/inorganic photosensors can be easily tuned by changing the pattern geometry. Measured static water contact angles range from 125° to 164°, as the distance between the pillars is increased from 14 to 120 μm while the contact angle hysteresis decreases from 36° down to 2°