A facile, green and efficient approach was applied to synthesize multi-walled carbon nanotubes (MWNTs) decorated with silver nanoparticles (MWNT-Ag) for further potential application. Oxidized MWNTs were decorated with silver nanoparticles (Ag NPs) via a method combining ultraviolet irradiation-induced reduction and conventional silver mirror reaction without any reducing agent. The obtained product was characterized using various methods. X-ray diffraction proved that the Ag NPs were synthesized successfully. Moreover, Ag NPs with a diameter of 80 nm, attached onto MWNTs, could be clearly observed in field emission scanning electron microscopy images, which also confirmed Ag NPs. Energy-dispersive spectroscopy and transmission electron microscopy also indicated the presence of Ag NPs. Furthermore, thermogravimetric analysis was used to measure the content of Ag NPs in MWNT-Ag, the result indicating that the weight content of Ag NPs was up to 31.88%. UV–visible absorption spectroscopy was adopted to evaluate the dispersion property of MWNT-Ag. The result illustrated that MWNT-Ag had a good dispersibility and stability in water. Characterization was also carried out through Fourier transform infrared spectroscopy, Raman spectroscopy and dynamic light scattering analysis.

The selection of non-hazardous solvent systems is an important factor that can significantly influence fiber formation during polymer electrospinning. In this paper, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/polyethylene oxide (PEO) has been electrospun using different solvent systems to investigate the influence of different solution properties on nanofiber morphology and diameter, the thermal and mechanical properties, as well as the degradation kinetics of the electrospun fibers. The morphology, thermal and mechanical properties of PHBV/PEO electrospun fibers were characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), and a universal testing machine, respectively. The results showed that the binary-solvent system (dichloromethane/ethanol DCM/EtOH) gave the finest defect-free fibers, and exhibited the best thermal and mechanical properties of all the single solvents (chloroform (CHL), dichloromethane (DCM)). Therefore, the effect of DCM/EtOH in different ratios on PHBV/PEO electrospun fibers was studied in detail. In brief, the DCM/EtOH solvent system was considered to be the best candidate for PHBV/PEO for electrospinning.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/polyethylene oxide (PEO) mats were fabricated by electrospinning in different weight ratios (i.e., 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 0/100). In this paper, dichloromethane (DCM) has been used as potential solvent for electrospinning. In order to evaluate the influence of PEO and DCM on the final properties of PHBV mat, the following characterization techniques were employed: scanning electron microscopy, Fourier transform infrared attenuated total reflectance spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, differential scanning calorimetry, and the test of mechanical properties, water contact angle, porosity analysis, swelling properties, water–vapor transmission rate (WVTR) and in vitro degradation behavior. All PHBV/PEO electrospun mats consist of randomly oriented and distinctly separated fibers. The average fiber diameters and the porosity were 738–1098 nm and 80–90 %, respectively. The water contact angle, swelling ratio, WVTR, and in vitro degradation behavior of PHBV/PEO electrospun mats were 124°–55°, 265–436 %, 1977–2610 g m−2 day−1, and 17–50 %, respectively. Besides, the crystallinity degree of PHBV/PEO electrospun mats has decreased with the increasing of PEO content. Therefore, PEO imparted PHBV/PEO electrospun mats on better properties, improving the nature defects of PHBV. In particular, PHBV/PEO 70/30 electrospun mat with optimizing performance, was considered the best candidate for potential scaffold in skin tissue engineering.

PVA composites fibers with a large fraction of multi-walled carbon nanotubes modified by both covalent and non-covalent functionalization were produced by a wet-spinning process. Model XQ-1 tensile tester, thermogravimetric analysis, scanning electron microscopy, differential scanning calorimetry, and wide-angle X-ray diffraction were used to characterize the properties of PVA/MWNT composite fibers. The TGA results suggested that MWNTs content in composite fibers were ranged from 5.3 wt% to 27.6 wt%. The mechanical properties of PVA/MWNT composite fibers were obviously superior to pure PVA fiber. The Young׳s modulus of composite fibers enhanced with increasing the content of MWNTs, and it rised gradually from 6.7 GPa for the pure PVA fiber to 12.8 GPa for the composite fibers with 27.6 wt% MWNTs. Meanwhile, the tensile strength increased gradually from 0.39 GPa for the pure PVA fiber to 0.74 GPa for the composite fibers with 14.4 wt% MWNTs. Nevertheless, the tensile strength of the composite fibers decreased as the MWNTs content up to 27.6 wt%. SEM results indicated that the MWNTs homogeneously dispersed in the composite fibers, however some agglomerates also existed when the content of MWNTs reached 27.6 wt%. DSC results proved strong interfacial interaction between MWNTs and PVA chain, which benefited composite fibers in the efficient stress-transfer. WXAD characterization showed that the orientation of PVA molecules declined from 94.1% to 90.9% with the increasing of MWNTs content. The good dispersibility of MWNTs throughout PVA matrix and efficient stress-transfer between MWNTs and PVA matrix may contributed to significant enhancement in the mechanical properties.

•The multiwalled carbon nanotubes were functionalized with PLL.•MWCNTs–PLL nanocomposite was characterized with FT-IR, TGA and UV–Vis.•The dispersibilities of MWCNTs–PLL nanocomposite in water were evaluated.•MWCNTs–PLL nanocomposite in water was pH-responsive.•The method was a mild approach for MWCNTs modified with PLL.Poly-l-lysine (PLL) was synthesized using lysine as raw material by N-carboxyanhydride polymerization and characterized by Fourier transform infrared spectroscopy and 1H NMR. Multiwalled carbon nanotubes (MWCNTs) were non-covalently functionalized using PLL in order to prepare MWCNTs–PLL composite. MWCNTs–PLL was characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis and UV–Vis absorption spectroscopy. The dispersion of MWCNTs–PLL composite was investigated by UV–Vis absorption spectroscopy, dynamic light scattering analysis and digital photograph. The results showed that the dispersion of MWCNTs–PLL composite was obviously better than that of MWCNTs–SDS composite in water while it was also approximate with that of MWCNTs–SDBS. In addition, MWCNTs–PLL was pH-responsive in water so that it could be used as bio-nanomaterial in future.

The multi-walled carbon nanotubes (MWCNTs) were treated with four wet chemical oxidants (Na2ZnO2, Na3BO3, NaAlO2, NaOH) in order to prepare MWCNTs modified with hydroxyl groups. The resulting products were characterized with elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy and X-ray photoelectron spectroscopy. These results demonstrate that there are hydroxyl groups on the surface of treated MWCNTs while their structures are retained. The dispersions of untreated and treated MWCNTs indicate that treated MWCNTs can disperse more readily in chloroform than untreated MWCNTs. The concentration of hydroxyl groups of MWCNTs treated by NaAlO2 is the largest in four treated MWCNTs.Highlights► The multi-walled carbon nanotubes were treated with Na2ZnO2, Na3BO3, NaAlO2 and NaOH. ► Treated MWCNTs were characterized with EA, FTIR, TGA, Raman and XPS. ► The dispersibilities of treated MWCNTs in chloroform were evaluated. ► The concentration of hydroxyl groups of MWCNTs treated by NaAlO2 was largest. ► The method was a mild approach for MWCNTs modified with hydroxyl groups.