In recent years, significant attention has been given to "green" product innovation and related manufacturing processes. This work reports the preparation of few-layer graphene (FLG) and respective PLA-based composites by an eco-friendly, efficient, and cost-effective approach. FLG was produced in a scaled-up process, based on the noncovalent functionalization of a micronized graphite with a pyrene derivate (PY), in aqueous solution. The exfoliation degree, morphology, and thermal stability of the exfoliated material were evaluated. Then, the influence of the pristine graphite and FLG on the morphology, crystallinity, thermal and mechanical properties of PLA composites produced by melt mixing is reported for the first time. The composites prepared with the lowest loading of 0.05 wt% demonstrated suitability for further processing for potential applications where product safety is crucial, such as in biomedicine.

Dual self-assembly of dipeptides into microspheres and microtapes. Quantum confinement in self-assembled structures of dipeptides. Self-assembly of dipeptides as nanospheres and nanotubes into blue luminescent electrospun fibers.

Polylactic acid (PLA) is a bio-based, biodegradable polymer that presents high potential for biomedical and sensing applications. Ongoing works reported in the literature concern mainly applications based on 3D printing, while textile applications are hindered by the limited flexibility of PLA and its composite filaments. In the present work, PLA/multiwall carbon nanotube (MWCNT) composite filaments were produced with enhanced flexibility and electrical conductivity, which may be applied on a textile structure. A biodegradable plasticizer was incorporated in the nanocomposites, aiming at improving MWCNT dispersion and increasing the flexibility of the filaments. Filaments were produced with a range of compositions and their morphology was characterized as well as their thermal, thermomechanical, and electrical properties. Selected compositions were tested for sensing activity using saturated acetone vapor, demonstrating a suitable response and potential for the application in fabrics with sensing capacity.

Driven by the need to deliver new, lead-free, eco-friendly solder pastes for soldering electronic components to Printed Circuit Boards (PCB), electrically conductive adhesives (ECAs) based on epoxy, carbon nanotubes (CNT), and exfoliated graphite (EG) were designed. The rheology of the adhesives prepared is paramount for the success of the deposition process, which is based on stencil printing. Thus, a rheological analysis of the process was first performed. Then, an experimental protocol was defined to assess the relevant viscoelastic characteristics of the adhesives for stencil printing application. Different composite formulations of epoxy/CNT/EG were produced. Their rheological characteristics were established following the designed protocol and benchmarked with a commercial solder paste. The thermal and electrical properties of the composite formulations were also characterized. As a result, a new, electrically conductive adhesive was delivered with potential to be an eco-friendly alternative to the solder paste currently used in stencil printing of PCB.

The latest advances on the development of wearables electrochemical sensors and biosensors has been revolutionizing healthcare, allowing a faster and specific diagnosis of pathological condition. The purpose of this work was to develop the first stage of wearable conductive based-textiles using natural (cotton) and synthetic (polyamide) fabrics composed of the conductive polypyrrole and polyaniline polymers. Conductive polymers were polymerized in situ within fabrics using the correspondent monomers (pyrrole, Py and aniline, ANi) and an oxidizing agent (ammonium persulfate, APS). The obtained fabrics were characterized in terms of microstructure, hydrophobicity, chemical composition, color fastness of domestic and industrial washing, color fastness to rubbing and cytotoxicity. Optimal conductivity vales (10−6<σ < 10−4) were attained in PPy and PANi fabrics using 2:1 ratio (0.5 M Py and 0.25 M APS) and 1:1 ratio (0.5 M ANi and 0.5 M APS), respectively. Textiles maintained their morphological integrity upon the polymerization process and, in some conditions, presented hydrophobicity (θ > 90°for PA/CO fabrics containing PPy and CO fabrics containing PANi; θ < 90° for Bleached PA and PA fabrics containing PANi). The surface and volumetric conductivities of fabrics containing PPy or PANi were not affected after the color fastness to domestic and industrial washing and to rubbing testing's, except CO fabrics containing PANi. Cell viability was higher than ≈70% in both synthetic and natural fabrics containing PPy or PANi, with the exception of natural fabrics containing PANi that revealed a cell viability less than ≈50%. In conclusion, this study demonstrates the development and characterization of conductive based-textiles using synthetic and natural fabrics containing PPy and PANi with great potential to be used in future biomedical applications.

Using the electrospinning technique nanofibers consisting of organic nonlinear optical 3-nitroaniline (3NA, C6H6N2O2) nanocrystals embedded in poly-ε-caprolactone (PCL) polymer, 3NA@PCL nanofibers, were produced. Polarimetry optical second harmonic generation and X-ray diffraction studies show that 3NA push-pull molecules crystallize inside the polymer fibers with a strong preferential orientation giving rise to an alignment of the molecular dipole moments along the nanofibers longitudinal axis. This alignment strongly enhances the second order nonlinear optical response of the fibers. Intense second harmonic generation emission was observed from a single nanofiber, corresponding to an effective second order susceptibility of 80 pm V-1, four times greater than the largest second order susceptibility tensor element (21 pm V-1) associated with a macroscopic 3NA crystal. Moreover, when subjected to a modest periodically applied force of 3 N, a piezoelectric current of 70 nA generated by a 4 cm2 electrospun nanofiber mat amounted to 122 nW cm-2 of instantaneous density power, sufficient to power a LCD display. The results show that the electrospinning technique is a powerful technique to fabricate organic functional materials with oriented nanocrystals made of highly polarizable molecules, embedded in a polymer matrix.

The increasing complexity of printed circuit boards (PCBs) due to miniaturization, increased the density of electronic components, and demanding thermal management during the assembly triggered the research of innovative solder pastes and electrically conductive adhesives (ECAs). Current commercial ECAs are typically based on epoxy matrices with a high load (>60%) of silver particles, generally in the form of microflakes. The present work reports the production of ECAs based on epoxy/carbon nanomaterials using carbon nanotubes (single and multi-walled) and exfoliated graphite, as well as hybrid compositions, within a range of concentrations. The composites were tested for morphology (dispersion of the conductive nanomaterials), electrical and thermal conductivity, rheological characteristics and deposition on a test PCB. Finally, the ECA’s shelf life was assessed by mixing all the components and conductive nanomaterials, and evaluating the cure of the resin before and after freezing for a time range up to nine months. The ECAs produced could be stored at −18 °C without affecting the cure reaction.

Electronic packaging, or assembly of packed electronic components on printed circuit boards, present challenges that require innovative solder pastes and electrically conductive adhesives to face the increasing complexity of PCB assembly, with denser board occupation and demanding thermal management during assembly. Our aim is to prepare carbon particle based conductive adhesives. The first step to achieve this goal was to prepare composites with epoxy resin and a variety of nano to micron scale carbon particle, produced by mixing on a three roll mill. The percolation threshold for each particle type was determined as well as the conductivity level reached after percolation.

Dipeptide biomaterials are strong piezoelectric materials that can convert applied mechanical forces into electricity. We have developed large-scale hybrid electrospun arrays containing N-tert-butoxycarbonyl (Boc) diphenylalanine in the form of nanotubes embedded in biocompatible polymers. These nanofibers exhibit strong piezoelectric properties when a periodic mechanical force is applied. The nanostructured hybrid materials were produced by the electrospinning technique. Optical absorption measurements show four bands in the spectral region 240-280 nm indicating quantum confinement due to nanotube formation of Boc-diphenylalanine in dichloromethane solutions. A strong blue photoluminescence emission was observed from nanotubes crystallized inside the fiber arrays during the electrospinning process. These two dimensional hybrid biomaterial structures are able to generate voltage, current and density power of up to 30 V, 300 nA and 2.3 μW cm-2, respectively, when a periodical force of 1.5 N is applied. The dipeptide-polymer electrospun arrays can power several liquid-crystal display panels and may be used for biomedical applications and as bio-energy sources.

Intense well-polarized second harmonic light was generated by para-Nitroaniline self-assembled thin films in different polymeric host matrices. The large area films of the organic chromophore with micron thickness were produced using a modified version of capillary growth. Analysis of the generated second harmonic light indicates that the para-Nitroaniline molecules, which nominally crystalize in a centrosymmetric space group, were organized into structures with an appreciable second order susceptibility dominated by a single tensor element. Under the best conditions, the film's effective second order optical susceptibility is slightly greater than that of beta barium borate for incident light at 800 nm. Generalizing this approach to a broad range of organic molecules with strong individual molecular second order nonlinear responses, but which ordinarily form centrosymmetric organic crystals, could open a new pathway for the fabrication of efficient thin film second harmonic light generators.

Intense well polarized second harmonic light was generated by poly(methyl methacrylate) nanofibres with embedded para-nitroaniline nanocrystals. Subwavelength diameter fibres were electro-spun using a 1.2 weight ratio of chromophore to polymer. Analysis of the generated second harmonic light indicates that the para-nitroaniline molecules, which nominally crystalize in the centrosymmetric space group, were organized into noncentrosymmetric structures leading to a second order susceptibility dominated by a single tensor element. Under the best deposition conditions, the nanofibrers display an effective nonlinear optical susceptibility approximately two orders of magnitude greater than that of potassium dihydrogen phosphate. Generalizing this approach to a broad range of organic molecules with strong individual molecular second order nonlinear responses, but which nominally form centrosymmetric organic crystals, could open a new pathway for the fabrication of efficient sub-micron sized second harmonic light generators.

The search for graphene or few-layer graphene production methods that are simple, allow mass production, and yield good quality material continues to provoke intense investigation. The present work contributes to this investigation through the study of the aqueous exfoliation of four types of graphene sources, which are namely graphite and graphite nanoflakes with different morphologies and geographical origins. The exfoliation was achieved in an aqueous solution of a soluble pyrene derivative that was synthesized to achieve maximum interaction with the graphene surface at low concentration (5 × 10−5 M). The yield of bilayer and few-layer graphene obtained was quantified by Raman spectroscopic analysis, and the adsorption of the pyrene derivative on the graphene surface was studied by thermogravimetric analysis and X-ray diffraction. The whole procedure was rationalized with the help of molecular modeling.

The work reported demonstrates an simple method of extracting cellulose nanofibers (CNF) from cellulose microfibers (CMF) obtained from the plant Stipatenacissima. Here, a method for the production of CNF from CMF extracted from Alfa grass by exfoliation in polyvinyl alcohol (PVA) solution, is demonstrated. The CMF were produced in powder form and exfoliated in PVA aqueous solution to produce composites with 2, 4, 5 and 10 wt-% of CNF. Scanning Electron Microscopy demonstrated exfoliation of CMF, dispersion of the CNF and wetting by the polymer. The composites were characterised by thermogravimetry, differential scanning calorimetry, X-ray diffraction and tensile testing. The addition of CNF to PVA reduced the crystallinity degree of PVA. The large increase of the Young's modulus from 38 to 113% (relative to pure PVA) for composites with 2 to 10 wt-% of CNF incorporation is consistent with the extensive exfoliation of CMF into CNF and its excellent interface with PVA.

Graphene nanoribbons (GNR) were generated in ethanol solution by unzipping pyrrolidine-functionalized carbon nanotubes under mild conditions. Evaporation of the solvent resulted in regular few-layer stacks of graphene nanoribbons observed by transmission electron microscopy (TEM) and X-ray diffraction. The experimental interlayer distance (0.49-0.56 nm) was confirmed by computer modelling (0.51 nm). Computer modelling showed that the large interlayer spacing (compared with graphite) is due to the presence of the functional groups and depends on their concentration. Stacked nanoribbons were observed to redissolve upon solvent addition. This preparation method could allow the fine-tuning of the interlayer distances by controlling the number and/or the nature of the chemical groups in between the graphene layers.

1 Institute for Polymers and Composites/I3N, University of Minho, Campus de Azurem, 4800-058 Guimaraes, Portugal 2 Department of Chemistry, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal 3 3B’s Research Group – Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine. AvePark, 4806-909, Caldas das Taipas, Guimaraes, Portugal. 4 ICVS/3B s PT Government Associate Laboratory, Braga/Guimaraes, Portugal 5 Computer Science and Technology Center, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal 6 International Iberian Nanotechnology Laboratory (INL), Av. Mestre Jose Veiga, 4715330 Braga, Portugal 7 Pole for Innovation in Polymer Engineering (PIEP), University of Minho, Campus of Azurem, 4800-058 Guimaraes, Portugal *mcpaiva@dep.uminho.pt

Processing polymers by microinjection molding (mu IM) generate specific constraints upon the polymer melt such as high shear stress and rapid cooling, leaving a mark upon the microstructure of the micropart. The present work compares the morphology and structure of polyamide 6 samples produced by melt extrusion and mu IM. The specimens obtained were analyzed by polarized light microscopy, differential scanning calorimetry, and wide-angle X-ray diffraction. alpha and gamma crystalline forms were formed in polyamide 6 samples prepared by both methods. The gamma form was dominant in the skin of the microinjection molded part, with larger contribution for these samples compared with extruded samples. The conditions used in mu IM lead to considerable orientation at the skin region, decreasing toward the core, while the extruded samples showed almost no orientation. The overall degree of crystallinity of the microinjection molded part was lower compared with the extruded sample. Copyright (C) 2014 John Wiley & Sons, Ltd.

Microinjection molding is a powerful technology in micro-manufacture, providing millimeter scale parts at large scale production rate. In order to produce homogeneous composite parts, good dispersion of the nanoreinforcement in the polymer matrix is required. In the present work the carbon nanotube (CNT) reinforcement was dispersed in polyamide 6 (PA6) using a mini twin-screw extruder. Nanocomposites were prepared with different compositions (1% and 4,5%) of pure CNT (p-CNT) and functionalized CNT (f-CNT). 1 The effect of CNT functionalization on the PA6/CNT interface, the CNT dispersion, the nanocomposite morphology and structure, for the microinjection moulded parts, were studied by optical and electron microscopies, differential scanning calorimetry and X-ray diffraction. It was observed that CNT functionalization improved dispersion, showing the formation of a larger number of smaller agglomerates as compared to the p-CNT composites. The incorporation of CNT increased the electrical conductivity of the microinjection molded composites, and, at low CNT loading, f-CNT improved mechanical properties relative to p-CNT. DSC and X-ray analysis showed that the total crystallinity of the PA6 was marginally affected by the presence of CNTs, but a large change in the relative amount of  and  crystalline forms of the PA6 was observed from pure polymer to the nanocomposites, as depicted in Figure 1.

Graphene nanoribbons (GNR) have received a great deal of attention due their promise for electronics and optoelectronic applications [1]. Recently, the formation of GNR was observed “in situ” by unzipping of carbon nanotubes under ultra-high vacuum scanning tunneling microscopy (UHV STM) [2]. The CNT under observation were functionalized by the 1,3-dipolar cycloaddition reaction [3], in which the concentration of covalently bonded functional groups can be controlled by the experimental functionalization conditions. This functionalization route was responsible for the unzipping of the CNT, and thus the GNR formation by unzipping of functionalized CNT was repeated in ethanol suspension. The present work demonstrates the formation of graphene nanoribbons in solution by unzipping of functionalized carbon nanotubes. The formation of the GNR prepared in solution was studied by UV-visible spectroscopy, and the GNR obtained by solvent evaporation were analyzed by Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and scanning tunneling microscopy (STM). TEM and STM images demonstrated the formation of few layer graphene ribbons, and this result was confirmed by Raman spectroscopy. Molecular modeling was applied to study the crystalline stacking of functionalized GNRs yielding interlayer distances of 0.51 nm, in agreement with STM and XRD analysis. It was demonstrated that this interlayer distance was required to accommodate the functional groups attached to the graphene. Figure 1 depicts the Raman spectra of the functionalized carbon nanotubes and resulting GNR, showing evidence for the formation of few-layer graphene.

In the title compound, C(20)H(18)N(2)O(2)S, the indole mean plane and benzene ring form a dihedral angle of 65.0 (1)°. In the crystal structure, weak inter-molecular N-H⋯π and C-H⋯O inter-actions link the mol-ecules into ribbons propagated along [100].