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1.
J Colloid Interface Sci ; 607(Pt 1): 367-377, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34509111

RESUMO

Harmless and breathable flexible humidity sensor has important applications in continuous and real-time detection of human physiological activities. In this work, with hydrophobic poly (vinylidene fluoride) (PVDF) membrane as both the template and substrate and cetyltrimethylammonium bromide as a structure regulator, polyaniline (PANI) was unilaterally deposited on a PVDF microporous membrane to facilely fabricate a single-sided integrated flexible humidity sensor (IFHS). Such IFHS is featured with unique micro/nano structure and good air permeability. Moreover, it exhibits good humidity sensing properties at room temperature including fast response, small hysteresis and stable response even under bending deformation. The flexible sensor could realize non-contact monitoring of human respiration and speaking activities. Unilateral deposition of PANI and good breathability of IFHS avoids direct contact between PANI and human skin, thus averting harms to human and minimizing the deterioration of humidity sensing properties of PANI layer. The simple method is universal to the preparation of single-sided, integrated, breathable, nontoxic and fast response wearable humidity sensors based on PANI and hydrophobic microporous polymer membranes, offering useful references for the construction of advanced flexible sensors.


Assuntos
Nanoestruturas , Dispositivos Eletrônicos Vestíveis , Compostos de Anilina , Humanos , Umidade , Polivinil , Compostos de Vinila
2.
J Colloid Interface Sci ; 607(Pt 1): 711-719, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34530191

RESUMO

Indoor air quality (IAQ) has assumed new significance given the extensive amount of time spent indoor due to the coronavirus pandemic and particulate matter (PM) pollution. Accordingly, the development of window air filters to effectively intercept PM from outdoor air under natural ventilation conditions is an important research topic. However, most existing filters inevitably suffer from the compromise among filtration capability, transparency, and air permeability. In this study, we fabricate a high-performance transparent air filter to improve IAQ via natural ventilation. polyvinylidene fluoride (PVDF) superfine nanofibers of size 20-35 nm are prepared using extremely dilute solution electrospinning; a multi-scale nanofiber structure is then designed. By adjusting the ratio of PVDF superfine nanofibers (SNs) to PVDF coarse fibers (CNs), we balance the structure-performance relationship. Benefiting from the multiscale structural features that include a small pore size (0.72 µm) and high porosity (92.22%), the resulting filters exhibit excellent performance including high interception efficiency (99.92%) for PM0.3, low air resistance (69 Pa), high transparency (∼80%) and stable filtration after 100 h of UV irradiation. This work describes a new strategy for the fabrication of nanofibers with true-nanoscale diameters and the design of high-performance air filters.


Assuntos
Filtros de Ar , Nanofibras , Material Particulado , Polivinil
3.
Chemosphere ; 286(Pt 2): 131705, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34333185

RESUMO

With regard to the treatment of multicomponent wastewaters, to construct multifunctional super-wetting membranes is highly attractive in current decade. In this work, a low-cost and novel NiFe2O4/TA/PVDF composite membrane was fabricated via a facile in-situ deposition method under vacuum system. In which, photo-response NiFe2O4 nanoparticles were immobilized on the surface of flexible PVDF base membrane via hydrophilic tannic acid (TA) as the binder. The resulting composite membrane exhibited a special superwettability of superamphilicity in air and underwater superoleophobicity with a nanoscale rough surface structure. One the one hand, NiFe2O4/TA/PVDF membrane can be used a reusable catalyst in Photo-Fenton degradation of organic dyes with high efficiency. On the other hand, the composite membrane can effectively separate emulsified oils from representative oil-in-water emulsions with excellent separation efficiency all above 99 % and relatively high flux (880-1525 Lm-2h-1 bar-1). More importantly, NiFe2O4/TA/PVDF composite membrane showed satisfactory processing efficiency, anti-fouling property and excellent reusability in deal with the mixed organic pollutants (water-insoluble emulsified oils and water-soluble organic dyes) existed in one aqueous system, which followed the procedure of initially photo-Fenton degradation of organic dyes emulsion and successively separation the remaining emulsion over the recovered membrane. This successful development of high-performance NiFe2O4/TA/PVDF composite membrane will provide a new candidate for both oil/water separation and organic wastewater treatment, as well as promote the utilization of spinel ferrites in the construction of multifunctional membrane for environmental purification.


Assuntos
Poluentes Ambientais , Membranas Artificiais , Polivinil , Taninos
4.
Chemosphere ; 286(Pt 2): 131756, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34365174

RESUMO

MnO2 nanorods with controllable scale were grown in the PVDF-g-PMAA modified membrane to form PVDF-g-PMAA@ MnO2 membrane through the in situ redox reaction of KMnO4 solution, which is confirmed by scanning electron microscopy (SEM) and X-ray energy-dispersion spectroscopy (EDX). The pore size of the membrane decreased with the increase of KMnO4 solution concentration. The thermodynamic stability and the hydrophilicity of the membrane were also enhanced by the MnO2 nanorods. The water flux, bovine serum albumin (BSA)/Lysozyme protein solution flux and rejection, flux recovery, etc. showed effective improvement of the anti-fouling performance of the PVDF-g-PMAA@ MnO2 membrane. More importantly, it can effectively separate BSA from lysozyme, which provided a potential application in the field of biology, food, and other industrial fields for the requirement of separation and purification.


Assuntos
Incrustação Biológica , Nanotubos , Incrustação Biológica/prevenção & controle , Compostos de Manganês , Membranas Artificiais , Óxidos , Ácidos Polimetacrílicos , Polivinil
5.
Chemosphere ; 287(Pt 2): 132092, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34826888

RESUMO

Superhydrophobic nanofibers have received prominent attention owing to their exceptional properties and researchers are focused on developing high-performing MD membranes. Herein, we fabricate superhydrophobic electrospun nanofibrous membranes using polyvinylidene fluoride (PVDF) solutions with silica nanoparticles (0 wt% to 6 wt%) to create multiscale (or hierarchical) surface roughness. For superhydrophobicity, the composite membranes (Si@PVDF) were subjected to a two-step modification that included acid pre-treatment and silanization with fluoroalkylsilane (FAS) compound of low surface energy. The acid pre-treatment enhances the hydroxyl group of SiO2 nanoparticles and create active sites in abundance for silanization. The modified membranes (FAS-Si@PVDF-A) having 6 wt% SiO2 showed excellent wetting resistance with water contact angle (WCA) up to 154.6 ± 2.2°, smaller average pore size of 0.27 ± 0.3 µm, and high liquid entry pressure (LEP) of 143 ± 4 kPa. It was observed, increasing silica content decreased the fiber diameter and average pore size and increased WCA and LEP of modified membranes. The modified superhydrophobic membranes gave stable permeate flux, exhibited strong wetting resistance and excellent salt rejection in vacuum membrane distillation (VMD) test. The optimal FAS-Si@PVDF-A membrane (6 wt% SiO2) of thickness 98 ± 5 µm produced a stable permeate flux of more than 11.5 kg m-2 h-1 and salt rejection as high as 99.9% after 22 h of continuous operation using NaCl solution (3.5 wt%) as feed. Therefore, this modification provided superhydrophobic membranes possessing robust anti-wetting properties with significant permeability and has encouraging application in membrane distillation for desalination.


Assuntos
Nanofibras , Purificação da Água , Destilação , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais , Polivinil , Dióxido de Silício , Vácuo
6.
Chemosphere ; 287(Pt 3): 132212, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34547558

RESUMO

Amphiphilic copolymers containing hydrophilic and hydrophobic blocks represented by surfactants have proven to be more effective for modifying membranes than hydrophilic copolymers. However, studies on the effects of additive and coagulation bath pH on the morphology and properties of surfactant-modified membranes have rarely been reported. Hence, this study aims to investigate the effects of the additive dosage and the coagulation bath pH on the mechanisms of phase inversion and performance improvement of amphoteric fluorocarbon special surfactant (FS-50) blended PVDF membranes. It was observed that the pure water flux increased from 114.68 LMH/bar of the original membrane M0 to 205.02 LMH/bar of the blend membrane M1, and then to 615.88 LMH/bar of the coagulation-bath-regulated membrane MPH9 with a high BSA rejection rate of 90.86%, showing a two-stage jump. The addition of FS-50 promoted the instantaneous phase inversion of the membrane, allowing the blend membrane to exhibit a higher proportion of pore characteristics and stronger permeability. After that, the mechanisms of the membrane phase inversion process affected by the coagulation bath pH were interpreted according to the pH-response characteristics of FS-50 in terms of charge repulsion effect and compressed double-electron layer effect. Furthermore, the cross-sectional morphology and the surface structure of the membrane prepared in acidic and alkaline coagulation baths were significantly affected by the pH of the coagulation bath, exhibiting different features. For one, the porosity of the membranes gradually decreased as the acidity and alkalinity of the coagulation bath increased, and the membrane MPH9 exhibited both maximum surface and overall porosity. For another, the coagulation bath pH did not negatively affect the contact angle, surface roughness and tensile strength of the membranes. Overall, adjusting the dosage of FS-50 and the pH of the coagulation bath is a promising approach to greatly enhance membrane performance.


Assuntos
Fluorcarbonetos , Tensoativos , Estudos Transversais , Concentração de Íons de Hidrogênio , Membranas Artificiais , Polivinil
7.
J Hazard Mater ; 421: 126747, 2022 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-34364210

RESUMO

The synthesis of Bi2WO6 and CeO2 photocatalytic nanomaterials exhibit a great ability to photodegrade the antibiotics and shown excellent oxidation of various organic pollutants. Heterostructure 1:1 & 2:1 Bi2WO6/CeO2 nanocomposite was successfully synthesized via the facile sono-dispersion method and exquisite photocatalytic activity. The 0.5 wt% of nanocomposites were well-grafted on PVDF membrane surface via an in-situ polymerization method using polyacrylic acid. The fourier transform infrared (FTIR) spectra demonstrated that the network formation in PVDF induced by the -COOH functional group in acrylic acid. The grafted membrane morphology and strong binding ability over the membranes were validated by scanning electron microscope with energy dispersion (SEM-EDS) and X-ray photoelectron spectroscopy (XPS), respectively. The permeate flux of 49.2 L.m-2 h-1 and 41.65 L.m-2 h were observed for tetracycline and the humic acid solution respectively for 1 wt% of PVP and 0.5 wt% of photocatalytic nanomaterials in PVDF membrane. The tetracycline and humic acid photodegradation rate of 82% and 78% and total resistance of 1.43 × 1010 m-1 and 1.64 × 1010 m-1, 83.5% and 77% flux recovery ratio were observed with N5 membrane. The 2:1 Bi2WO6/CeO2 nanocomposite grafted membrane showed a high permeate flux and better photodegradation ability of organic pollutants in the wastewater.


Assuntos
Substâncias Húmicas , Tetraciclina , Antibacterianos , Catálise , Polivinil
8.
Water Sci Technol ; 84(9): 2380-2393, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34810318

RESUMO

Novel polyvinylidene fluoride/TiO2/UiO-66-NH2 (PVDF/TiUN) membranes were produced by the delay phase separation method via introducing the TiO2/UiO-66-NH2 (TiUN) nanocomposite into PVDF casting solution. Interconnection of TiO2 and UiO-66-NH2 improved photocatalysis capacity and endowed PVDF/TiUN membranes with self-cleaning capability. Quantitative measurements showed that, firstly, PVDF/TiUN membranes exhibited improved photodegradation kinetics and efficiency (up to 88.1%) to Rhodamine B (RhB). Secondly, the performances of bovine serum albumin (BSA) rejection and permeation of PVDF/TiUN membranes outperformed those of other check samples, indicating enhanced hydrophilicity. Thirdly, rejection rate of BSA reached a breathtaking 98.14% and flux recovery ratio (FRR) of BSA reached a breathtaking 95.37%. Thus, given their excellent anti-contamination property and separation performance, the PVDF/TiUN membrane is very likely to be a novel water treatment membrane.


Assuntos
Incrustação Biológica , Estruturas Metalorgânicas , Incrustação Biológica/prevenção & controle , Membranas Artificiais , Polivinil , Titânio , Zircônio
9.
Water Sci Technol ; 84(9): 2541-2556, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34810330

RESUMO

Ultrafiltration membranes are widely used for the treatment of papermaking wastewater. The antifouling performance of polyvinylidene fluoride (PVDF) ultrafiltration membranes can be improved by changing the hydrophilicity. Here, a novel amphiphilic copolymer material, PVDF grafted with N-isobutoxy methacrylamide (PVDF-g-IBMA), was prepared using ultraviolet-induced Cu(II)-mediated reversible deactivation radical polymerization. The amphipathic copolymer was used to prepare ultrafiltration membrane via NIPS. The prepared PVDF-g-IBMA ultrafiltration membrane was estimated using 1H NMR, FT-IR, and DSC. The contact angle, casting viscosity, and the permeation performance of the PVDF-g-IBMA ultrafiltration membrane were also determined. The pure water flux, bovine serum albumin removal rate, and pure water flux recovery rate of the PVDF-g-IBMA ultrafiltration membrane were 432.8 L·m-2·h-1, 88.4%, and 90.8%, respectively. Furthermore, for the treatment of actual papermaking wastewater, the chemical oxygen demand and turbidity removal rates of the membrane were 61.5% and 92.8%, respectively. The PVDF-g-IBMA amphiphilic copolymer ultrafiltration membrane exhibited good hydrophilicity and antifouling properties, indicating its potential for treating papermaking wastewater.


Assuntos
Incrustação Biológica , Ultrafiltração , Incrustação Biológica/prevenção & controle , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais , Polivinil , Espectroscopia de Infravermelho com Transformada de Fourier , Águas Residuárias
10.
Diagn Interv Radiol ; 27(6): 786-788, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34792034

RESUMO

Bronchial artery embolization (BAE) is considered the first choice treatment for hemoptysis. To our knowledge no cases of BAE using a recent ethylene vinyl alcohol copolymer agent (Squid) have been previously mentioned. Two cases of BAE for remitting hemoptysis using Squid and polyvinyl alcohol particles are reported in this technical note. The final angiographic control confirmed full exclusion of the target territory in both cases. Both patients felt some chest pain immediately after the embolization, not requiring any medications. No more episodes of hemoptysis occurred in the following 3 months after the procedure.


Assuntos
Artérias Brônquicas , Embolização Terapêutica , Animais , Artérias Brônquicas/diagnóstico por imagem , Decapodiformes , Hemoptise/diagnóstico por imagem , Hemoptise/terapia , Humanos , Álcool de Polivinil , Polivinil , Estudos Retrospectivos , Resultado do Tratamento
11.
IET Nanobiotechnol ; 15(4): 427-440, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34694715

RESUMO

The main emphasis herein is on the eco-friendly synthesis and assessment of the antimicrobial potential of silver nanoparticles (AgNPs) and a cytotoxicity study. Silver nanoparticles were synthesised by an extracellular method using bacterial supernatant. Biosynthesised silver nanoparticles were characterised by UV-vis spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, dynamic light scattering, and zeta potential analysis. The synthesised silver nanoparticles exhibited a characteristic peak at 420 nm. TEM analysis depicted the spherical shape and approximately 20 nm size of nanoparticles. Silver nanoparticles carry a charge of -33.75 mV, which confirms their stability. Biogenic polyvinyl pyrrolidone-coated AgNPs exhibited significant antimicrobial effects against all opportunistic pathogens (Gram-positive and Gram-negative bacteria, and fungi). Silver nanoparticles equally affect the growth of both Gram-positive and Gram-negative bacteria, with a maximum inhibition zone observed at 22 mm and a minimum at 13 mm against Pseudomonas aeruginosa and Fusarium graminearum, respectively. The minimum inhibitory concentration (MIC) of AgNPs against P. aeruginosa and Staphylococcus aureus was recorded at between 15 and 20 µg/ml. Synthesised nanoparticles exhibited a significant synergistic effect in combination with conventional antibiotics. Cytotoxicity estimates using C2C12 skeletal muscle cell line via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and lactate dehydrogenase assay were directly related to the concentration of AgNPs and length of exposure. On the basis of the MTT test, the IC50 of AgNPs for the C2C12 cell line was approximately 5.45 µg/ml concentration after 4 h exposure.


Assuntos
Anti-Infecciosos , Nanopartículas Metálicas , Antibacterianos/farmacologia , Anti-Infecciosos/farmacologia , Bacillaceae , Escherichia coli , Fusarium , Bactérias Gram-Negativas , Bactérias Gram-Positivas , Nanopartículas Metálicas/toxicidade , Testes de Sensibilidade Microbiana , Polivinil , Prata , Espectroscopia de Infravermelho com Transformada de Fourier
12.
Molecules ; 26(19)2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34641513

RESUMO

A study on the headspace volatile organic compounds (VOCs) profile of native populations of Sideritis romana L. and Sidertis montana L., Lamiaceae, from Croatia is reported herein, to elucidate the phytochemical composition of taxa from this plant genus, well-known for traditional use in countries of the Mediterranean and the Balkan region. Headspace solid-phase microextraction (HS-SPME), using divinylbenzene/carboxene/polydimethylsiloxane (DVB/CAR/PDMS) or polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber, coupled with gas chromatography-mass spectrometry (GC-MS) was applied to analyze the dried aerial parts of six native populations in total. Furthermore, principal component analysis (PCA) was conducted on the volatile constituents with an average relative percentage ≥1.0% in at least one of the samples. Clear separation between the two species was obtained using both fiber types. The VOCs profile for all investigated populations was characterized by sesquiterpene hydrocarbons, followed by monoterpene hydrocarbons, except for one population of S. romana, in which monoterpene hydrocarbons predominated. To our knowledge, this is the first report on the VOCs composition of natural populations of S. romana and S. montana from Croatia as well as the first reported HS-SPME/GC-MS analysis of S. romana and S. montana worldwide.


Assuntos
Sideritis/química , Compostos Orgânicos Voláteis/análise , Croácia , Dimetilpolisiloxanos/química , Cromatografia Gasosa-Espectrometria de Massas/métodos , Monoterpenos/análise , Compostos Fitoquímicos/análise , Polivinil/química , Análise de Componente Principal , Sesquiterpenos/análise , Microextração em Fase Sólida/instrumentação , Microextração em Fase Sólida/métodos
13.
Artigo em Russo | MEDLINE | ID: mdl-34714007

RESUMO

Chronic subdural hematomas (CSH) usually require surgical evacuation via a burr hole or craniotomy. Certain incidence of recurrent postoperative CSH is known. Middle meningeal artery (MMA) embolization has been described as an alternative surgery for new or recurrent CSH or as a preventive measure to reduce the risk of postoperative recurrence. The authors report successful MMA embolization with 2 non-adhesive embolic agents of various viscosities (SQUID 12 and SQUID 18, Balt USA, Irvine, CA, USA) for recurrent postoperative CSH in a 44-year-old woman.


Assuntos
Embolização Terapêutica , Hematoma Subdural Crônico , Adulto , Feminino , Hematoma Subdural Crônico/terapia , Humanos , Artérias Meníngeas , Polivinil , Viscosidade
14.
Part Fibre Toxicol ; 18(1): 38, 2021 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-34663357

RESUMO

BACKGROUND: Silver nanoparticles (AgNPs) are widely used in biomedicine due to their strong antimicrobial, antifungal, and antiviral activities. Concerns about their possible negative impacts on human and environmental health directed many researchers towards the assessment of the safety and toxicity of AgNPs in both in vitro and in vivo settings. A growing body of scientific information confirms that the biodistribution of AgNPs and their toxic effects vary depending on the particle size, coating, and dose as well as on the route of administration and duration of exposure. This study aimed to clarify the sex-related differences in the outcomes of oral 28 days repeated dose exposure to AgNPs. METHODS: Wistar rats of both sexes were gavaged daily using low doses (0.1 and 1 mg Ag/kg b.w.) of polyvinylpyrrolidone (PVP)-coated small-sized (10 nm) AgNPs. After exposure, blood and organs of all rats were analysed through biodistribution and accumulation of Ag, whereas the state of the liver and kidneys was evaluated by the levels of reactive oxygen species (ROS) and glutathione (GSH), catalase (CAT) activity, superoxide dismutase (SOD) and glutathione peroxidase (GPx), expression of metallothionein (Mt) genes and levels of Mt proteins. RESULTS: In all animals, changes in oxidative stress markers and blood parameters were observed indicating the toxicity of AgNPs applied orally even at low doses. Sex-related differences were noticed in all assessed parameters. While female rats eliminated AgNPs from the liver and kidneys more efficiently than males when treated with low doses, the opposite was observed for animals treated with higher doses of AgNPs. Female Wistar rats exposed to 1 mg PVP-coated AgNPs/kg b.w. accumulated two to three times more silver in the blood, liver, kidney and hearth than males, while the accumulation in most organs of digestive tract was more than ten times higher compared to males. Oxidative stress responses in the organs of males, except the liver of males treated with high doses, were less intense than in the organs of females. However, both Mt genes and Mt protein expression were significantly reduced after treatment in the liver and kidneys of males, while they remained unchanged in females. CONCLUSIONS: Observed toxicity effects of AgNPs in Wistar rats revealed sex-related differences in response to an oral 28 days repeated exposure.


Assuntos
Nanopartículas Metálicas , Povidona , Animais , Feminino , Masculino , Nanopartículas Metálicas/toxicidade , Polivinil , Povidona/toxicidade , Ratos , Ratos Wistar , Prata/toxicidade , Distribuição Tecidual
15.
J Environ Manage ; 300: 113707, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34534759

RESUMO

Selective removal of contaminants from water by membranes is of practical importance for water purification and environmental protection. In the present study, through an in-situ polymerization process, a novel composite of Fe3O4/molecularly imprinted resorcinol -formaldehyde-melamine resin (Fe3O4/MIRFMR) was synthesized. Then, the novel membrane was prepared from a tea filter bag (TFB) as a base substrate which was subsequently coated by a casting solution containing polyvinylidene fluoride (PVDF) matrix, Prunus scoparia gum as a hydrophilic agent and Fe3O4/MIRFMR as selective filler by phase inversion technique. Resorcinol as functional monomers with multiple hydrophilic groups such as -OH, -NH2 and -NH-, were used for selective removal of Rhodamine B (RhB) as target molecule. The Fe3O4/MIRFMR/PVDF/TFB membranes were characterized by FE-SEM, XRD, FTIR, BET, VSM, water contact angle (WCA) and mechanical analysis. The filtration and adsorption of RhB on the prepared membrane was investigated parameters in a cross-module filtration setup. Casting solution containing 0.01 g of Fe3O4/MIRFMR as optimum value showed good wettability, high water flux (42.5 L/m2 h), flux recovery ratio (88.9%), RhB removal efficiency (95.8%). The selectivity of 4.9, 3.3, 2.1 and 2.5 was found to be for RhB compared to AB, MG, EB, and TB dye. It seems that the fabricated membrane could be an effective and selective option for wastewater containing pollutants. The high removal efficiency, fouling resistance, good wettability and stability of the fabricated membrane are promising for use in practical water filtration, especially for selective removal of dyes.


Assuntos
Corantes , Membranas Artificiais , Fenômenos Magnéticos , Polivinil
16.
J Chem Inf Model ; 61(9): 4537-4543, 2021 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-34519202

RESUMO

The pervasive use of portable electronic devices, powered from rechargeable batteries, represents a significant portion of the electricity consumption in the world. A sustainable and alternative energy source for these devices would require unconventional power sources, such as harvesting kinetic/potential energy from mechanical vibrations, ultrasound waves, and biomechanical motion, to name a few. Piezoelectric materials transform mechanical deformation into electric fields or, conversely, external electric fields into mechanical motion. Therefore, accurate prediction of elastic and piezoelectric properties of materials, from the atomic structure and composition, is essential for studying and optimizing new piezogenerators. Here, we demonstrate the application of harmonic-covalent and reactive force fields (FF), Dreiding and ReaxFF, respectively, coupled to the polarizable charge equilibration (PQEq) model for predicting the elastic moduli and piezoelectric response of crystalline zinc oxide (ZnO) and polyvinylidene difluoride (PVDF). Furthermore, we parametrized the ReaxFF atomic interactions for Zn-F in order to characterize the interfacial effects in hybrid PVDF matrices with embedded ZnO nanoparticles (NPs). We capture the nonlinear piezoelectric behavior of the PVDF-ZnO system at different ZnO concentrations and the enhanced response that was recently observed experimentally, between 5 and 7 wt % ZnO concentrations. From our simulation results, we demonstrate that the origin of this enhancement is due to an increase in the total atomic stress distribution at the interface between the two materials. This result provides valuable insight into the design of new and improved piezoelectric nanogenerators and demonstrates the practical value of these first-principles based modeling methods in materials science.


Assuntos
Nanopartículas , Óxido de Zinco , Simulação de Dinâmica Molecular , Polivinil
17.
Int J Mol Sci ; 22(17)2021 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-34502514

RESUMO

In this study, we employed the copolymer poly(methyl vinyl ether-alt-maleic monoethyl ester) (PMVEMA-Es) and three fluorene-based cationic conjugated polyelectrolytes to develop fluorescent nanoparticles with emission in the blue, green and red spectral regions. The size, Zeta Potential, polydispersity, morphology, time-stability and fluorescent properties of these nanoparticles were characterized, as well as the nature of the interaction between both PMVEMA-Es and fluorescent polyelectrolytes. Because PMVEMA-Es contains a carboxylic acid group in its structure, the effects of pH and ionic strength on the nanoparticles were also evaluated, finding that the size is responsive to pH and ionic strength, largely swelling at physiological pH and returning to their initial size at acidic pHs. Thus, the developed fluorescent nanoparticles can be categorized as pH-sensitive fluorescent nanogels, since they possess the properties of both pH-responsive hydrogels and nanoparticulate systems. Doxorubicin (DOX) was used as a model drug to show the capacity of the blue-emitting nanogels to hold drugs in acidic media and release them at physiological pH, from changes in the fluorescence properties of both nanoparticles and DOX. In addition, preliminary studies by super-resolution confocal microscopy were performed, regarding their potential use as image probes.


Assuntos
Portadores de Fármacos/síntese química , Fluorenos/química , Anidridos Maleicos/química , Polivinil/química , Antibióticos Antineoplásicos/farmacologia , Cor , Doxorrubicina/farmacologia , Portadores de Fármacos/química , Ésteres/química , Transferência Ressonante de Energia de Fluorescência/métodos , Humanos , Concentração de Íons de Hidrogênio , Éteres Metílicos/química , Nanogéis/química , Nanopartículas/química , Tamanho da Partícula , Polímeros/química , Compostos de Vinila/química
18.
Int J Mol Sci ; 22(15)2021 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-34361025

RESUMO

In this work, synthesis and optical properties of a new composite based on poly(o-phenylenediamine) (POPD) fiber like structures, poly(vinylidene fluoride) (PVDF) spheres and double-walled carbon nanotubes (DWNTs) are reported. As increasing the PVDF weight in the mixture of the chemical polymerization reaction of o-phenylenediamine, the presence of the PVDF spheres onto the POPD fibers surface is highlighted by scanning electron microscopy (SEM). The down-shift of the Raman line from 1421 cm-1 to 1415 cm-1 proves the covalent functionalization of DWNTs with the POPD-PVDF blends. The changes in the absorbance of the IR bands peaked around 840, 881, 1240 and 1402 cm-1 indicate hindrance steric effects induced of DWNTs to the POPD fiber like structures and the PVDF spheres, as a consequence of the functionalization process of carbon nanotubes with macromolecular compounds. The presence of the PVDF spheres onto the POPD fiber like structures surface induces a POPD photoluminescence (PL) quenching process. An additional PL quenching process of the POPD-PVDF blends is reported to be induced in the presence of DWNTs. The studies of anisotropic PL highlight a change of the angle of the binding of the PVDF spheres onto the POPD fiber like structures surface from 50.2° to 38° when the carbon nanotubes concentration increases in the POPD-PVDF/DWNTs composites mass up to 2 wt.%.


Assuntos
Dimetilformamida/química , Nanotubos de Carbono/química , Polivinil/química , Anisotropia , Nanocompostos/química , Análise Espectral Raman
19.
BMJ Case Rep ; 14(8)2021 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-34376414

RESUMO

We report transarterial Onyx embolization with flow control using rapid ventricular pacing (RVP) in a middle-aged male patient with tentorial dural arteriovenous fistulas (TDAVFs). The patient completed angiographic obliteration in one session without any complications, and the 6-month postangiographic obliteration follow-up showed no evidence of residual or recurrent dural arteriovenous fistulas. RVP may be a novel treatment option of flow control to facilitate the embolic agent penetrating into the venous side and to achieve complete cure in transarterial embolization of TDAVFs.


Assuntos
Malformações Vasculares do Sistema Nervoso Central , Embolização Terapêutica , Malformações Vasculares do Sistema Nervoso Central/diagnóstico por imagem , Malformações Vasculares do Sistema Nervoso Central/terapia , Dimetil Sulfóxido , Humanos , Masculino , Pessoa de Meia-Idade , Polivinil , Estudos Retrospectivos , Resultado do Tratamento
20.
Sensors (Basel) ; 21(16)2021 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-34450718

RESUMO

In this work, new highly sensitive graphene-based flexible strain sensors are produced. In particular, polyvinylidene fluoride (PVDF) nanocomposite films filled with different amounts of graphene nanoplatelets (GNPs) are produced and their application as wearable sensors for strain and movement detection is assessed. The produced nanocomposite films are morphologically characterized and their waterproofness, electrical and mechanical properties are measured. Furthermore, their electromechanical features are investigated, under both stationary and dynamic conditions. In particular, the strain sensors show a consistent and reproducible response to the applied deformation and a Gauge factor around 30 is measured for the 1% wt loaded PVDF/GNP nanocomposite film when a deformation of 1.5% is applied. The produced specimens are then integrated in commercial gloves, in order to realize sensorized gloves able to detect even small proximal interphalangeal joint movements of the index finger.


Assuntos
Grafite , Nanocompostos , Dispositivos Eletrônicos Vestíveis , Polivinil
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