The Use of Recycled PET for the Synthesis of New Mechanically Improved PVP Composite Nanofibers.

Polyethylene terephthalate (PET) waste has become a major challenge for the conservation of the environment due to difficult degradation. For this reason, it is important to develop new recycling strategies for reusing this waste. In this work, the electrospinning technique was used to synthesize composite nanofibers of polyvinylpyrrolidone (PVP), recycling PET (RPET) that was obtained from the chemical recycling of postconsumer PET with glycolysis and styrene (ST) as a crosslinking agent. The polymer solutions were analyzed by viscosity and frequency sweeping, while the composite nanofibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), and nanoindentation to compare their properties. The PVP nanofibers presented an average diameter of 257 nm; the RPET/PVP and RPET/PVP/ST composite nanofibers had average diameters of 361 nm and 394 nm, respectively; and the modulus of elasticity and hardness of the RPET/PVP/ST composite nanofibers were 29 and 20 times larger, respectively, than those of the PVP nanofibers. With the synthesis of these composite nanofibers, a new approach to PET recycling is presented.

Influence of RE (Pr3+, Er3+, Nd3+) doping on structural, vibrational and enhanced persistent photocatalytic properties of ZnO nanostructures.

Rare earth (RE- Pr, Er and Nd) doped ZnO nanostructures were prepared through simple wet chemical precipitation route. The RE doping induced interesting morphological transition from spherical to flower like structures were analyzed. The X-ray diffraction (XRD) measurements revealed that the prepared materials were of highly crystalline in nature and RE dopant ions did not altered the crystal structure of ZnO. The microstrain of ZnO was altered with respect to the nature of dopants. In the case of the Pr doped ZnO, X-ray photoelectron spectroscopy (XPS) analysis confirmed that the dopant (Pr) ions successfully substituted in the ZnO lattice. Raman spectra revealed RE doping induced lower energy side shift and variation in intensity of the peaks related to the characteristic phonon modes of ZnO. In the case of Nd doped ZnO nanostructures, dopant induced suppression in classical Raman modes and evolution of multiphonon related modes were identified. Optical diffuse reflectance spectral (DRS) measurements, along with the characteristic excitonic band of ZnO, other bands associated to the transitions of 4f energy levels related to the RE ions were observed. The partially filled 4f orbitals led to the enhanced photocatalytic activity in RE doped ZnO nanostructures. The observed enhanced photocatalytic activity in RE doped ZnO when compared to bare ZnO was discussed. The decolorization efficiency of MB ensued the following order 96 > 94 > 86 > 78% for ZnErO, ZnNdO, ZnPrO and ZnO, respectively.

Removal of Tetracycline Pollutants by Adsorption and Magnetic Separation Using Reduced Graphene Oxide Decorated with α-Fe2O3 Nanoparticles.

Nanocomposites of reduced graphene oxide (RGO) with ferromagnetic α-Fe2O3 nanoparticles have been prepared in-situ by thermal treatment. The structure and morphology of the hybrid material were studied by X-ray photoelectron spectroscopy, Raman, X-ray diffraction, and transmission electron microscopy. The results show a hybrid material highly modified with α-Fe2O3 nanoparticles distributed on the graphene surface. The adsorption kinetics show the presence of α-Fe2O3 nanoparticles on the RGO surface, and the amount of remaining functional groups dominated by ionization and dispersion. The adsorption kinetics of this adsorbent was characterized and found to fit the pseudo-second-order model. The α-Fe2O3 nanoparticles on RGO modify the electrostatic interaction of RGO layers and tetracycline, and adsorption properties decreased in the hybrid material. Adsorption isotherms fit with the Langmuir model very well, and the maximum capacity adsorption was 44.23 mg/g for RGO and 18.47 mg/g for the hybrid material. Magnetic characterization of the hybrid material shows ferromagnetic behavior due to the nanosize of α-Fe2O3 with a saturation magnetization, Ms = 7.15 Am²/kg, a remanence Mr = 2.29 Am²/kg, and a coercive field, Hc = 0.02 T.

Enzymatic hydrolysis of cellulose nanoplatelets as a source of sugars with the concomitant production of cellulose nanofibrils.

Cellulose, the most abundant biopolymer on earth, is produced at different ratios by all land plants. Since the morphology and crystallinity of cellulose are key factors involved in its enzymatic hydrolysis, in the present work, we tackled the study of the effects of such variables on the nanocellulose conversion into glucose. Cellulase from Trichoderma sp at 37 °C was used to produce glucose, the best results were found for the cellulose nanoplatelets (S-CNP) after 60 h of hydrolysis, which afforded a conversion of 47% to glucose, in contrast to 15% for the non-purified sample (W-CP) and 22% for microcrystalline cellulose (MCC20) used as control. The X-ray diffractogram recorded on the samples showed an initial crystallinity index of 45%, 54% and 72% for W-CNP, S-CNP and MCC20, respectively. Also, we showed that after 24 h of hydrolysis, long cellulose nanofibrils (∅ ≈ 30 nm) were found as a residue.

Nanostructured SnS2 Thin Films from Laser Ablated Nanocolloids: Structure, Morphology, Optoelectronic and Electrochemical Properties.

Tin disulfide (SnS2 ) is a binary chalcogenide semiconductor having applications in solar cells, energy storage, and optoelectronics. SnS2 thin films were deposited by spraying the nanocolloids synthesized by pulsed laser ablation in liquid. The structure, morphology, and optoelectronic properties were studied for films obtained from two liquid media (ethanol and isopropanol) and after heat treatments at various temperatures. X-ray diffraction analysis confirmed the hexagonal crystal structure of the films, whereas the 2-H polytype structure was identified by micro-Raman spectroscopy. Oxidation states of Sn (4+) and S (2-) identified from high resolution X-ray photoelectron spectra confirmed the composition and chemical states of the films. The SnS2 thin films exhibited distinct porous surface morphologies as the liquid medium in laser ablation was varied. All as-prepared and annealed films showed photoluminescence with a high intensity peak at 485 nm and a low intensity peak at 545 nm. Thin films annealed at 300 °C showed improved electrochemical properties upon illumination using a blue LED light source. Current-voltage curves recorded in dark and light as well as the photoresponse measurements showed their suitability for utilization in optoelectronic devices. The results of this study may trigger further research towards fabrication of nanostructured thin films in large area for optoelectronic and photoelectrochemical applications in an environment friendly and cost-effective way.

Synthesis and Properties of Tin Sulfide Thin Films from Nanocolloids Prepared by Pulsed Laser Ablation in Liquid.

Tin sulfide (SnS) nanoparticles were synthesized by pulsed laser ablation in liquid (PLAL) technique using an Nd:YAG laser operated at 532 nm. SnS thin films were deposited by spraying the colloidal suspension onto the heated substrates. The influence of different liquid media (dimethyl formamide and isopropyl alcohol) on the thin film properties were studied. Morphology, crystalline structure, and chemical composition of the nanoparticles were identified using transmission electron microscopy with energy dispersive X-ray analysis. The crystalline structure of the thin films was analyzed by using grazing incidence X-ray diffraction, and the chemical states by X-ray photoelectron spectroscopy. Scanning electron microscopy was employed for the morphological analysis of the thin films. Annealing the films at 380 °C improved the crystallinity of the films exhibiting a layered morphology, which may be useful in optoelectronic and sensing applications. Cyclic voltammetry studies showed that the films have good electrochemical properties.

Electrospun nylon nanofibers as effective reinforcement to polyaniline membranes.

This research demonstrates that a nylon nanofiber (NNF) mat can be an effective mechanical reinforcement to polyaniline (PANI) thin films. Nanofibers of ca. 250 nm diameter were produced by electrospinning of a nylon 6 solution in formic acid. Scanning electron microscopy showed that the solution impregnation method utilized was effective to embed the nanofibers into the PANI matrix. The effectiveness of NNFs as a mechanical reinforcement of a PANI thin film was assessed via dynamic mechanical analysis in tension mode. The as-cast PANI films displayed a tensile dynamic modulus, E', of ca. 0.65 GPa at room temperature. Scanning in the temperature showed that the PANI film has a usage temperature of up to about 80 degrees C, with this being limited by its glass transition temperature, and over this temperature range, the elastic modulus was nearly independent of the temperature. On the other hand, the PANI-NNF composite displayed a significantly higher tensile modulus at room temperature (1.1 GPa) and its usage temperature was extended up to just over 200 degrees C, with this being limited by the melting transition of nylon 6 (at 220 degrees C). The results therefore showed that the NNF mat increased the usage temperature of PANI films over 100 degrees C, opening up applications for PANI membranes.