Smart and robust electrospun fabrics of piezoelectric polymer nanocomposite for self-powering electronic textiles

The present work designs a piezoelectric nanogenerator (PENG) based on the electrospun nanofibers of the piezoelectric polymer, polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), by uniformly drawing the spun membranes containing cellulose nanocrystals (CNC, 2 wt%) and the Fe-doped nano ZnO (2 wt%). The hybrid nanocomposite fibers were made in double layers, with CNC/PVDF-HFP composite on one side and the Fe-doped ZnO/PVDF-HFP on the other side. This ferroelectric polymer composite exhibited maximum peak-to-peak output voltage of 12 V with a current density, 1.9 ?Acm?2, which are respectively higher by 60 and 2.3 times compared to the neat polymer fibers. The PENG is tested for its energy harvesting ability by exposing it to different environments such as ultrasound vibrations and human body movements during hand tapping, elbow movements and by attaching with the textile fabrics. While the finger tapping generated peak-to-peak output voltage of 6.5 V, elbow movements resulted in 5.5 V generation. In all sorts of movements, the nanogenerator shows good output performance indicating its compatibility with textile materials. The mechanical properties, breakdown strength and dielectric properties of the material are also in accordance with its possible applications in wearable electronic textiles. - 2019 The AuthorsThis publication is made possible by NPRP grant 6-282-2-119 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Cytocompatibility and Dielectric Properties of Sr2+ Substituted Nano-Hydroxyapatite for Triggered Drug Release

Hydroxyapatite (Ca5(PO4)3OH) is a well-known bioceramics material used in medical applications because of its ability to form direct chemical bonds with living tissues. In this context, we investigate the biocompatibility and dielectric properties of Sr2+-substituted hydroxyapatite nanoparticles were synthesized by sol-gel method. The influence of strontium on the crystal structure, functional group, morphological, electrical properties, and biocompatibility of as-synthesized nano-hydroxyapatite samples was analyzed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FE-SEM). Dielectrical properties of the bioactive Sr-HA sample were investigated by a dielectric impedance spectroscopy method. The observed results illustrate the incorporation of Sr2+ ions in the apatite lattice could influence the pure HA properties, by reducing the crystallite size and crystallinity quite consistent with the morphology variation. The ac conductivity (σac) increased with an increasing applied frequency confirmed that prepared HA sample exhibited the universal power law nature. Further, the in vitro drug loading and release studies using doxycycline as a model drug demonstrate that the Sr2+ -HA nanoparticles show high drug adsorption capacity and sustained drug release. Thus, the improved bioceramics system could be a promising candidate for future biomedical applications

Designing carbon nanotube-based oil absorbing membranes from gamma irradiated and electrospun polystyrene nanocomposites

Carbon-based materials are outstanding candidates for oil spill clean-ups due to their superhydrophobicity, high surface area, chemical inertness, low density, recyclability, and selectivity. The current work deals with the fabrication of membrane oil absorbents based on carbon nanotube (CNT) reinforced polystyrene (PS) nanocomposites by electrospinning technique. The spun membranes are also irradiated with the gamma radiation to induce enough crosslinks and thus good polymer-filler interactions. The structural, morphological, and surface properties in addition to the oil/water separation efficiency were investigated by varying the concentration of CNT and the dose of γ-irradiation. Fabricated nanofiber membranes show superior hydrophobicity and selective oil absorption at 0.5 wt.% of CNT concentration. The best mechanical properties are also obtained at this particular concentration and at 15 KGy optimum γ-irradiation dosage. The gamma irradiated PS/0.5 wt.% CNT membrane also exhibits good antibacterial effects against the bacteria, Escherichia coli, in the form of bacterial inhibition rings around the membranes. The present study thus shows the environmental applicability of the fabricated PS/CNT membranes in treating oil-contaminated water

Designing piezoelectric nanogenerator from PVDFHFP nanocomposite fibers containing cellulose nanocrystals and Fedoped ZnO

Self-powering devices harvest energy from the environment and perform based on a maintenance free approach. These materials are of utmost significance as they solve the problems associated with the energy crisis and management, to greater extends. Advances in material science and the design of various polymer nanocomposites developed many self-powering devices that are flexible, sensitive, less power consuming and of low cost. The semi-crystalline polymer, poly vinylidene fluoride (PVDF) and its co-polymers are notable for mechanical energy harvesting because of the typical crystalline phases in their structure. Various nanoparticles are added to such polymers to enhance their dielectric and piezoelectric properties as well. Since the alignment of crystalline phases improve the energy harvesting properties, techniques such as electrical poling are practiced to enhance their applicability. Among various alignment procedures, electrospinning stands as unique since the high voltage applied to the polymer solution generates nanofiber scaffolds in perfect alignments. The present work aims to develop electrospun composite fibers in nano-dimensions for designing self-powering nanogenerators. The co-polymer of PVDF, polyvinylidene fluoride hexa fluoropropylene (PVDF-HFP) was used as the base polymer and the iron-doped zinc oxide (Fe-ZnO) and cellulose nanocrystals (CNC) as the filler reinforcements. Fe-ZnO nanostructures were obtained by hydrothermal synthesis method from the ZnO precursor, while the CNC were synthesized following the acid hydrolysis of cellulose microfibers. The optimized concentration of 20 wt.% was used for obtaining the electrospun fibers of neat PVDF-HFP and various concentrations of nanoparticles were mixed with this base solution. Simple solvent mixing was employed using the acetone/DMF solvent mixture to prepare the composite solutions prior to electrospinning. The electrospinning conditions were also optimized by varying the applied voltage, tip to collector distance and speed of the rotating collector. Nice fibers were obtained at a voltage of 12-13 eV and rotating collector speed of 200 rpm. Composites of CNC with PVDF-HFP, Fe-ZnO with PVDF-HFP and the hybrid material of CNC/Fe-ZnO with PVDF-HFP were prepared and properties were investigated. All the fibers were tested for the morphology, structural, thermal and dielectric properties. The mechanical energy harvesting was performed using an assembled set up containing a frequency generator, shaker and data acquisition system. At 2 wt. % of the nanofillers, the PVDF-HFP/CNC generated about 2 V, the PVDF-HFP/Fe-ZnO generated about 4 V and the hybrid nanocomposite containing both nanoparticles generated about 6 V. The filler synergy plays a major role in regulating the material properties and here the combined effect of the piezoelectric performance of the cellulose nanocrystals and the modified ZnO nanoparticles enhanced the mechanical energy harvesting capability of the final nanocomposite. A nanogenerator is designed based on the developed polymer nanocomposite fibers and the piezoelectric performance on various conditions of stretching, pressing and twisting were also investigated. In all the cases the hybrid composite showed notable performance substantiating its application in designing self-powered nanogenerators. The dielectric properties of the hybrid material showed many fold increase in its dielectric constant, making it useful in electrical energy storage. In short, the designed device by electrospinning technique is highly useful in adding to the energy management and is environmentally safe and of good efficiency.qscienc

Effect of anions on the structural, morphological and dielectric properties of hydrothermally synthesized hydroxyapatite nanoparticles

Synthetic nano hydroxyapatites (HA) have been considered as potential biomaterials for bone tissue engineering applications because of its excellent biological properties. The present work deals with the synthesis of HA nanoparticles from different anion source materials via autoclave assisted hydrothermal method. All the prepared HA nanoparticles were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectra, field emission scanning electron microscopy, energy dispersive spectra and high resolution transmission electron microscopy. The XRD patterns reveal the pure and hexagonal phase structure with smaller crystallite size for HA obtained from various calcium salt precursors. HA particles prepared from nitrate precursors show spherical morphology with 32 nm grain size whereas those derived from the acetate, chloride and egg shell precursors respectively show needle-like, irregular and oval morphology. The effect of different anions on the dielectric properties and alternating conductivity of HA is investigated, as a polarized surface can trigger biological reactions. For the particles obtained from nitrate, acetate, chloride and egg shell precursors respectively give dielectric constant (εʹ) values of 9.96, 13.22, 9.92 and 10.86 at 5 MHz. The εʹ and dielectric loss (εʹʹ) values for the HA nanoparticles decrease with increase in the applied frequency as well. The alternating current conductivity values confirm that the as-synthesized HA samples exhibit insulating behavior. In short this article provides the various applicability of HA particles in optoelectronics and drug delivery.Open access funding provided by the Qatar National LibraryScopu

Comparative Study on Gas-Sensing Properties of 2D (MoS2, WS2)/PANI Nanocomposites-Based Sensor

NH3 is a highly harmful gas; when inhaled at levels that are too high for comfort, it is very dangerous to human health. One of the challenging tasks in research is developing ammonia sensors that operate at room temperature. In this study, we proposed a new design of an NH3 gas sensor that was comprised of two-dimensional (TMDs, mainly WS2 and MoS2) and PANI. The 2D-TMDs metal was successfully incorporated into the PANI lattice based on the results of XRD and SEM. The elemental EDX analysis results indicated that C, N, O, W, S and Mo were found in the composite samples. The bandgap of the materials decreased due to the addition of MoS2 and WS2. We also analyzed its structural, optical and morphological properties. When compared to MoS2 and PANI, the proposed NH3 sensor with the WS2 composite was found to have high sensitivity. The composite films also exhibited response and recovery times of 10/16 and 14/16 s. Therefore, the composite PANI/2D-TMDs is a suitable material for NH3 gas detection applications.This work is supported by the Qatar National Research Fund (Project number UREP 25-057-2-023). The funding achieved herein are solely the responsibility of the autors. The characterizations of this work are accomplished in the Central Laboratories Unit, Qatar University

Liquid exfoliated MoS2 sheet coupled with conductive polyaniline for gas sensor

Polyaniline (PANI)/MoS2 composites with porous microspheres were prepared by a hydrothermal and in situ polymerization method. The structural, optical, and morphological properties were characterized by X-ray powder diffraction, FTIR, scanning electron microscope, transmission electron microscope. The XRD results confirmed that the PANI/MoS2 composite was formed. Morphological characterization reveals that the successful formation of few to multilayered MoS2 nanosheet intercalated with the PANI nanoparticles

Synthesis and photoelectrochemical performance of Co doped SrTiO3 nanostructures photoanode

It is pertinent to realize that scientific research indicates that the most promising method for producing H2 is photo electrochemical water splitting through a photo anode. Cobalt-doped SrTiO3 (Co-SrTiO3) composite nanostructures were created in this study via hydrothermal synthesis. The impact of cobalt concentration change on Co-SrTiO3 has been identified using morphological, structural, and photo electrochemical research. Surface morphology of pure SrTiO3 nanoparticles using SEM and TEM reveals that the particles are intermittently agglomerated. The inclusion of Cobalt lowered the particle size of the nanostructures to 23 nm than pure SrTiO3 (41 nm). In addition, the peak profile has been influenced by cubic phase also identified from the x-ray diffraction analysis. The purity and composition of the materials were revealed by XPS analysis. The Co-SrTiO3 composite's produced the best charge transfer and recombination capabilities at 3% Co doping, according to electrochemical chemical impedance (EIS) spectroscopy. At 0.2 V applied potential, the obtained 3% Co-doped SrTiO3 photoanode system displays a photocurrent density of around 3.45 mA/cm2. The outcomes show that a promising application for the Co-doped SrTiO3 photoanode in photoelectrochemical water splitting.This publication was made possible by the support of an Qatar University Internal Grant (QUCG-CAM-20/21-6). The statements made herein are solely the responsibility of the authors. The characterizations of this work are accomplished in the Gas Processing Unit and in the Centra Laboratory Unit, at Qatar University

Enhanced corrosion protection of Epoxy/ZnO-NiO nanocomposite coatings on steel

ZnO-NiO nanocomposite with epoxy coating on mild steel has been fabricated by the sol–gel assisted method. The synthesized sample was used to study corrosion protection. The analysis was performed by electrochemical impedance spectroscopy in 3.5% NaCl solution. The structural and morphological characterization of the metal oxide nanocomposite was carried out using XRD and SEM with Energy Dispersive Absorption X-ray (EDAX) analysis. XRD reveals the ZnO-NiO (hexagonal and cubic) structure with an average ZnO-NiO crystallite size of 26 nm. SEM/EDAX analysis of the ZnO-NiO nanocomposite confirms that the chemical composition of the samples consists of: Zn (8.96 ± 0.11 wt.%), Ni (10.53 ± 0.19 wt.%) and O (80.51 ± 3.12 wt.%). Electrochemical Impedance Spectroscopy (EIS) authenticated that the corrosion resistance has improved for the nanocomposites of ZnO-NiO coated along with epoxy on steel in comparison to that of the pure epoxy-coated steelThis research was funded by the Undergraduate Research Experience Program project no. UREP24-133-2-036 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. This work was supported by the UREP grant # UREP24-133-2-036 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The authors would like to thank the Central laboratory Unit (CLU), Qatar University, 2713, Doha, Qatar, for SEM with EDAX analysis facility.Scopu

Electroactive poly(vinylidene fluoride) based materials: recent progress, challenges and opportunities

A poly(vinylidene fluoride) (PVDF) and its copolymers are polymers that, in specific crystalline phases, show high dielectric and piezoelectric values, excellent mechanical behavior and good thermal and chemical stability, suitable for many applications from the biomedical area to energy devices. This chapter introduces the main properties, processability and polymorphism of PVDF. Further, the recent advances in the applications based on those materials are presented and discussed. Thus, it shown the key role of PVDF and its copolymers as smart and multifunctional material, expanding the limits of polymer-based technologies.FCT (Fundação para a Ciência e Tecnologia) for financial support under the framework of Strategic Funding grants UID/FIS/04650/2019, and UID/QUI/0686/2019 and project PTDC/FIS-MAC/28157/2017, PTDC/BTMMAT/28237/2017, PTDC/EMD-EMD/28159/2017. The author also thanks the FCT for financial support under grant SFRH/BPD/112547/2015 (C.M.C.), SFRH/BPD/98109/2013 (V.F.C.), SFRH/BD/140698/2018 (R.B.P.), SFRH/BPD/96227/2013 (P.M.), SFRH/BPD/121526/2016 (D.M.C.), SFRH/BPD/97739/2013 (V. C.), SFRH/BPD/90870/2012 (C.R.). Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including FEDER financial support) and from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06)