Piezo-, photo- and piezophotocatalytic activity of electrospun fibrous PVDF/CTAB membrane

A composite material based on polyvinylidene fluoride (PVDF) nanofibers modified with cetyltrimethylammonium bromide (CTAB) was synthesized by coaxial electrospinning. The morphology and structure of the material were studied by SEM, FTIR spectroscopy, X-ray diffraction analysis, XPS, and the piezo-photo- and piezo-photocatalytic activity during the decomposition of the organic dye Methylene blue (MB) was studied. It is shown that the addition of CTAB promotes additional polarization of the PVDF structure due to ion-dipole interaction. It has been shown for the first time that the addition of CTAB promotes the photosensitivity of the wide-gap dielectric polymer PVDF (the band gap is more than 6 eV). It was demonstrated that the photocatalytic decomposition efficiency was 91% in 60 minutes. The material exhibits piezocatalytic activity – 73% in 60 minutes. Experiments on trapping active oxidizing forms have established that OH hydroxyl radicals play the main role in the photocatalytic process

Macroporous bioceramic scaffolds based on tricalcium phosphates reinforced with silica: microstructural, mechanical, and biological evaluation

The positive effect of silica on microstructural, mechanical and biological properties of calcium phosphate scaffolds was investigated in this study. Scaffolds containing 3D interconnected spherical macropores with diameters in the range of 300-770 mu m were prepared by the polymer replica technique. Reinforcement was achieved by incorporating 5 to 20 wt % of colloidal silica into the initial hydroxyapatite (HA) powder. The HA was fully decomposed into alpha and beta-tricalcium phosphate, and silica was transformed into cristobalite at 1200 degrees C. Silica reinforced scaffolds exhibited compressive strength in the range of 0.3 to 30 MPa at the total porosity of 98-40%. At a nominal porosity of 75%, the compressive strength was doubled compared to scaffolds without silica. When immersed into a cultivation medium, the formation of an apatite layer on the surfaces of scaffolds indicated their bioactivity. The supportive effect of the silicon enriched scaffolds was examined using three different types of cells (human adipose-derived stromal cells, L929, and ARPE-19 cells). The cells firmly adhered to the surfaces of composite scaffolds with no sign of induced cell death. Scaffolds were non-cytotoxic and had good biocompatibility in vitro. They are promising candidates for therapeutic applications in regenerative medicine

A brief introduction and current state of polyvinylidene fluoride as an energy harvester

This review summarizes the current trends and developments in the field of polyvinylidene fluoride (PVDF) for use mainly as a nanogenerator. The text covers PVDF from the first steps of solution mixing, through production, to material utilization, demonstration of results, and future perspective. Specific solvents and ratios must be selected when choosing and mixing the solution. It is necessary to set exact parameters during the fabrication and define whether the material will be flexible nanofibers or a solid layer. Based on these selections, the subsequent use of PVDF and its piezoelectric properties are determined. The most common degradation phenomena and how PVDF behaves are described in the paper. This review is therefore intended to provide a basic overview not only for those who plan to start producing PVDF as energy nanogenerators, active filters, or sensors but also for those who are already knowledgeable in the production of this material and want to expand their existing expertise and current overview of the subject

Structure Tuning and Electrical Properties of Mixed PVDF and Nylon Nanofibers

The paper specifies the electrostatic spinning process of specific polymeric materials, such as polyvinylidene fluoride (PVDF), polyamide-6 (PA6, Nylon-6) and their combination PVDF/PA6. By combining nanofibers from two different materials during the spinning process, new structures with different mechanical, chemical, and physical properties can be created. The materials and their combinations were subjected to several measurements: scanning electron microscopy (SEM) to capture topography; contact angle of the liquid wettability on the sample surface; Raman spectroscopy; X-ray photoelectron spectroscopy (XPS); and Fourier-transform infrared spectroscopy ({FT-IR}) to describe properties and their changes at the chemical level. Crystallization events were determined by differential scanning calorimetry (DSC). Furthermore, the contact angle of the wettability of the liquid on the surface was measured for the materials, and the permittivity was measured to observe the dielectric properties. The advantage of the addition of co-polymers was to control the properties of PVDF samples and understand the reasons for the changed functionality. The innovation point of this work is the complex analysis of PVDF modification caused by mixing with nylon PA6. Here we empathize that the application of nylon during the spin influences the properties and structure (polarization, crystallization) of PVDF

The Effect of the Thermosensitive Biodegradable PLGA–PEG–PLGA Copolymer on the Rheological, Structural and Mechanical Properties of Thixotropic Self-Hardening Tricalcium Phosphate Cement

The current limitations of calcium phosphate cements (CPCs) used in the field of bone regeneration consist of their brittleness, low injectability, disintegration in body fluids and low biodegradability. Moreover, no method is currently available to measure the setting time of CPCs in correlation with the evolution of the setting reaction. The study proposes that it is possible to improve and tune the properties of CPCs via the addition of a thermosensitive, biodegradable, thixotropic copolymer based on poly(lactic acid), poly(glycolic acid) and poly(ethylene glycol) (PLGA-PEG-PLGA) which undergoes gelation under physiological conditions. The setting times of alpha-tricalcium phosphate (-TCP) mixed with aqueous solutions of PLGA-PEG-PLGA determined by means of time-sweep curves revealed a lag phase during the dissolution of the -TCP particles. The magnitude of the storage modulus at lag phase depends on the liquid to powder ratio, the copolymer concentration and temperature. A sharp increase in the storage modulus was observed at the time of the precipitation of calcium deficient hydroxyapatite (CDHA) crystals, representing the loss of paste workability. The PLGA-PEG-PLGA copolymer demonstrates the desired pseudoplastic rheological behaviour with a small decrease in shear stress and the rapid recovery of the viscous state once the shear is removed, thus preventing CPC phase separation and providing good cohesion. Preliminary cytocompatibility tests performed on human mesenchymal stem cells proved the suitability of the novel copolymer/-TCP for the purposes of mini-invasive surgery

Influence of Hydroxyapatite Nanoparticles and Surface Plasma Treatment on Bioactivity of Polycaprolactone Nanofibers

Nanofibers are well known as a beneficial type of structure for tissue engineering. As a result of the high acquisition cost of the natural polymers and their environmentally problematic treatment (toxic dissolution agents), artificial polymers seem to be the better choice for medical use. In the present study, polycaprolactone nano-sized fibrous structures were prepared by the electrospinning method. The impact of material morphology (random or parallelly oriented fibers versus continuous layer) and the presence of a fraction of hydroxyapatite nanoparticles on cell proliferation was tested. In addition, the effect of improving the material wettability by a low temperature argon discharge plasma treatment was evaluated, too. We have shown that both hydroxyapatite particles as well as plasma surface treatment are beneficial for the cell proliferation. The significant impact of both influences was evident during the first 48 h of the test: the hydroxyapatite particles in polycaprolactone fibers accelerated the proliferation by 10% compared to the control, and the plasma-treated ones enhanced proliferation by 30%

SEM imaging and XPS characterization of doped PVDF fibers

Polyvinylidene fluoride (PVDF) is one of the most promising electroactive polymers; it exhibits excellent electroactive behaviours, good biocompatibility, excellent chemical resistance, and thermal stability, rendering it an attractive material for biomedical, electronic, environmental and energy harvesting applications. This work aims to further improve its properties by the inclusion of powders of piezoactive materials. Polyvinylidene fluoride was formed by electrospinning into fibres with a thickness of 1.5-0.3 µm and then examined in a scanning electron microscope. The work offers a description of the current procedure in the preparation of samples and their modification for examination in a scanning electron microscope, characterizes the individual components of doped fibres and deals with specific instruments used for various analytical methods. The work contains a theoretical introduction to the analytical methods to which the samples will be further subjected, such as energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS). The obtained excellent properties of doped PVDF could be used in the design of sensor

Processing of 0.55(Ba0.9Ca0.1)TiO3-0.45Ba(Sn0.2Ti0.8)O-3 lead-free ceramics with high piezoelectricity

We report a large piezoelectric constant (d(33)), 720 pC/N and converse piezoelectric constant (d(33)*), 2215 pm/V for 0.55(Ba0.9Ca0.1)TiO3-0.45Ba(Sn0.2Ti0.8)O-3 ceramics; the biggest value achieved for lead-free piezoceramics so far. The ceramic powders were calcined between 1050 degrees C-1350 degrees C and sintered at 1480 degrees C. The best properties were obtained at a calcination temperature (CT) of 1350 degrees C. The fitting combination of processing and microstructural parameters for example, initial powder particle size >2 mu m, ceramics density similar to 95%, and grain size similar to 40 mu m led to a formation of orthorhombic-tetragonal-pseudo-cubic (O-T-PC) mixed phase boundary near room temperature, supported by Raman spectra, pointed to the extremely high piezoelectric activity. These conditions significantly increase piezoelectric constants, together with high relative permittivity (epsilon(r)) >5000 and a low loss tangent (tan delta) of 0.029. In addition, the d(33) value stabilizes in the range of 400-500 pC/N for all samples calcined between 1050 degrees C and 1250 degrees C. The results entail that the (Ba,Ca)(Sn,Ti)O-3 ceramics are strong contenders to be a substitute for lead-based materials for room temperature applications