Porous Polyvinyl Alcohol Research Articles

A Laser-Induced Photoelectrochemical Sensor for Natural Sweat Cu2+ Detection

Tracking fluctuations in the Cu2+ level in sweat is meaningful for non-invasive and real-time assessment of Cu2+-abnormality-related diseases and provides important diagnostic information. However, the user-unfriendly ways to obtain sweat and sweat biofouling have limited the development of this field. Herein, we exploit a highly sensitive photoelectrochemical (PEC) sensor as a detection method, a powerful laser engraving technique for the large-scale fabrication of laser-induced graphene and In-doped CdS (LIG-In-CdS) photoelectrodes, and a hydrophilic porous polyvinyl alcohol (PVA) hydrogel for natural sweat collection for fingertip touch sweat Cu2+ monitoring. The proposed sensor has several very attractive features: (i) the LIG-In-CdS photoelectrode with high photoelectric conversion efficiency can be produced by a cheap 450 nm semiconductor laser system; (ii) the sensor performs Cu2+ detection with a wide linear range of 1.28 ng/mL~5.12 μg/mL and good selectivity; (iii) the PVA hydrogel possesses an excellent antifouling effect ability and a rapid natural sweat collection ability; and (iv) the sensor exhibits feasibility and good reliability for PEC sensing of sweat Cu2+. Thus, these advantages endow the proposed method with a great deal of potential for smart monitoring of heavy metals in sweat in the future.

A Wearable PVA Film Supported TiO2 Nanoparticles Decorated NaNbO3 Nanoflakes‐Based SERS Sensor for Simultaneous Detection of Metabolites and Biomolecules in Human Sweat Samples

AbstractSweat is one of the non‐invasive diagnostic biofluids that provides critical information about human health. In this work, a wearable sweat sensor integrated with a polymer‐based fluid absorption layer modified with titanium oxide (TiO2) nanoparticles decorated sodium niobate (NaNbO3) nanoflakes in porous polyvinyl alcohol (PVA) film matrix is demonstrated for the detection of vital metabolites (such as glucose and urea) and biomolecules (ascorbic acid (AA) and uric acid (UA)) in human sweat samples via surface‐enhanced Raman scattering (SERS). The TiO2@NaNbO3/PVA (SERS patch) exhibits a low limit of detection (LOD) of 0.50, 0.80, 1.00, and 100 mm towards AA, glucose, UA, and urea, respectively. The SERS patch displays a high enhancement factor with a low accumulation time of 20s which can be ascribed to the surface coordination between the TiO2@NaNbO3 and the analytes leading to interfacial charge‐transfer transition (ICTT). Besides, the photo‐induced charge transfer (PICT) resonance significantly amplifies the SERS signal. The SERS patch is successful in the simultaneous determination of AA, glucose, UA, and urea in simulated sweat samples with minimal mutual interference. The high efficacy of the SERS patch proves it as an ideal platform for a wide range of wearable healthcare monitoring applications.

Chemically Cross-Linked Graphene Oxide as a Selective Layer on Electrospun Polyvinyl Alcohol Nanofiber Membrane for Nanofiltration Application.

Graphene oxide (GO) nanosheets were utilized as a selective layer on a highly porous polyvinyl alcohol (PVA) nanofiber support via a pressure-assisted self-assembly technique to synthesize composite nanofiltration membranes. The GO layer was rendered stable by cross-linking the nanosheets (GO-to-GO) and by linking them onto the support surface (GO-to-PVA) using glutaraldehyde (GA). The amounts of GO and GA deposited on the PVA substrate were varied to determine the optimum nanofiltration membrane both in terms of water flux and salt rejection performances. The successful GA cross-linking of GO interlayers and GO-PVA via acetalization was confirmed by FTIR and XPS analyses, which corroborated with other characterization results from contact angle and zeta potential measurements. Morphologies of the most effective membrane (CGOPVA-50) featured a defect-free GA cross-linked GO layer with a thickness of ~67 nm. The best solute rejections of the CGOPVA-50 membrane were 91.01% for Na2SO4 (20 mM), 98.12% for Eosin Y (10 mg/L), 76.92% for Methylene blue (10 mg/L), and 49.62% for NaCl (20 mM). These findings may provide one of the promising approaches in synthesizing mechanically stable GO-based thin-film composite membranes that are effective for solute separation via nanofiltration.

Mechanically Strong, Low Thermal Conductivity and Improved Thermal Stability Polyvinyl Alcohol-Graphene-Nanocellulose Aerogel.

Porous aerogel materials have advantages of a low density, low thermal conductivity and high porosity, and they have broad application prospects in heat insulation and building energy conservation. However, aerogel materials usually exhibit poor mechanical properties. Single-component aerogels are less likely to possess a good thermal stability and mechanical properties. It is necessary to prepare multiple-composite aerogels by reinforcement to meet practical application needs. In this experiment, a simple preparation method for polyvinyl alcohol (PVA)–graphene (GA)–nanocellulose (CNF) ternary composite aerogels was proposed. This is also the first time to prepare ternary composite aerogels by mixing graphene, nanocellulose and polyvinyl alcohol. A GA–CNF hydrogel was prepared by a one-step hydrothermal method, and soaked in PVA solution for 48 h to obtain a PVA–GA–CNF hydrogel. PVA–GA–CNF aerogels were prepared by freeze drying. The ternary composite aerogel has advantages of excellent mechanical properties, a low thermal conductivity and an improved thermal stability, because strong hydrogen bonds form between the PVA, GA and CNF. The composite aerogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, Brunauer–Emmett–Teller analysis, dynamic thermal analysis, thermogravimetry and thermal constant analysis to characterize the properties of the ternary composite aerogels. The lightweight, low-density and porous PVA–GA–CNF composite aerogels withstood 628 times their mass. The thermal conductivity of the composite aerogels was 0.044 ± 0.005 W/mK at room temperature and 0.045 ± 0.005 W/mK at 70 °C. This solid, low thermal conductivity and good thermal stability PVA–GA–CNF ternary composite aerogel has potential application in thermal insulation.

Janus Polypyrrole Nanobelt@Polyvinyl Alcohol Hydrogel Evaporator for Robust Solar-Thermal Seawater Desalination and Sewage Purification.

The state-of-the-art solar-thermal evaporators demonstrating high energy utilization efficiency, a high evaporation rate, and salt rejection are highly desirable in solar-driven low-energy water purification/harvesting. Herein, a novel Janus solar evaporator is constructed by loading polypyrrole (PPy) nanobelts on the polyvinyl alcohol (PVA) hydrogel. The PPy nanobelts present a high solar absorption of 98.3%, leading to a localized solar-thermal efficiency of 82.5% when insulated from bulk water by the PVA hydrogel. The porous PVA hydrogel and the hydrophilic PPy nanobelts enable the efficient three-dimensional water transport. Taking advantages of the synergistic effect in the water-energy nexus, the Janus PPy nanobelt@PVA hydrogel evaporator evaporates water with a high rate of 2.26 kg m-2 h-1 via 80.1% solar energy from 1 sun irradiance with a low PPy loading of ∼3 mg cm-2 even at a rate of 2.64 kg m-2 h-1 via 96.3% solar energy for a biomimetic conical evaporator. The Janus evaporator presents superior salt-resistant desalination and contaminant purification performance in seawater and sewage. Furthermore, a portable solar-thermal purifier equipped with the Janus evaporator desalts real seawater far above the drinking water standard with over a 99.9% salt rejection rate and eliminates 95.8% of chemical oxygen demand in real sewage, highlighting its potential for advanced clean water harvesting.

An environmental energy-enhanced solar steam evaporator derived from MXene-decorated cellulose acetate cigarette filter with ultrahigh solar steam generation efficiency

Although solar energy is promising for water purification, there is still a room for further improving the solar steam generation efficiency. Herein, an environmental energy-enhanced solar steam evaporator is fabricated by immersing a cellulose acetate fiber-based cigarette filter (CF) in an aqueous solution of polyvinyl alcohol (PVA) followed by freeze-drying and decorating with MXene sheets. The presence of MXene is to absorb solar light and convert solar energy to thermal energy for efficient water evaporation, while the porous PVA network generated inside the pores of the filter during the freeze-drying process accommodates the dispersed MXene sheets and interconnects the CF and MXene. Because of the constructed PVA/MXene network inside the CF porous architecture and the hydrophilic feature of both MXene and PVA, the resultant MXene/PVA modified CF (MPCF) is highly hydrophilic and competent for rapid upward transfer of water. Interestingly, in addition to the normal energy input by the incident solar light, the large-area sidewall of MPCF gains thermal energy from the environment in the forms of heat convection and heat radiation to enhance the solar steam generation efficiency, resulting in an ultrahigh water evaporation rate of 3.38 kg m−2 h−1 with an outstanding evaporation efficiency of 132.9%.

Preparation and bacteriostatic research of porous polyvinyl alcohol / biochar / nanosilver polymer gel for drinking water treatment

Microbial contamination in drinking water has become an important threat to human health. There is thus an urgent need to develop antibacterial materials to treat drinking water. Here, porous silver-loaded biochar (C–Ag) was prepared using corn straw as the substrate and silver as the antibacterial agent. C–Ag was then uniformly distributed in polyvinyl alcohol gel beads of eluted calcium carbonate to prepare p-PVA/C–Ag antibacterial composite. The polymer composites were tested by FT-IR, XRD, SEM and TG-DSC. The results showed that C–Ag was more evenly distributed in the PVA gel spheres. Antibacterial experiments showed that p-PVA/C–Ag greatly inhibited Escherichia coli. Practical application tests revealed that p-PVA/C–Ag showed high and sustained bactericidal inhibition and reusability. Generally, p-PVA/C–Ag composite shows high potential to be applied to drinking water treatment.

Porous polymer composite separators with three-dimensional ion-selective nanochannels for high-performance Li–S batteries

Lithium-sulfur (Li–S) batteries have been regarded as one kind of the most attractive candidates for next-generation energy storage devices for their high theoretical energy density and fairly low cost. However, the “shuttle effect” caused by diffusion of soluble polysulfides and uncontrollable growth of lithium dendrite seriously deteriorate the long-term cycle stability and safety of Li–S batteries in practical applications. Herein, a highly porous polyvinyl alcohol (PVA)/sodium carboxylmethyl cellulose (CMC) composite separator with three-dimensional ion-selective nanochannels has been successfully fabricated via a facile non-solvent induced separation method. The abundant negative –COO- groups inside the nanochannels can hinder the undesired polysulfides penetrating through the separator, but allow Li+ transporting rapidly and induce uniform lithium stripping/plating. As a result, the Li–S battery using the porous PVA/CMC composite separator realizes stable cycling with a low decay rate of 0.045% per cycle over 500 cycles at 1 C. This work offers a feasible strategy to design advanced multifunctional Li–S battery separators.

An efficient approach to strengthen polyvinyl alcohol physical hydrogel via in situ growing NH2-decorated polysiloxane structures

This study aims to reveal a novel approach to synthesize high strength polyvinyl alcohol (PVA) physical hydrogel through the freezing-thawing method, with γ-aminopropyl triethoxysilane agent as an auxiliary factor. It was shown that the synthesized PVA-based hydrogels had high water content, excellent mechanical properties, and good biocompatibility. The saline agent γ-aminopropyl triethoxysilane in PVA solution was hydrolyzed and polymerized into NH2-decorated polysiloxane structures, which could be anchored to the porous PVA network and acted as a very effective hydrogen bond acceptor/donor, and thereby arousing a large increase in strength and toughness of PVA hydrogels. Meanwhile, the hydrophobic polysiloxane structures also increased the crystal cross-linking of PVA network and promoted a well-distributed porous PVA network. This work provides a simple and efficient route to synthesize high strength PVA-based physical hydrogel with desirable structure and properties.

Preparation and evaluation of ion-exchange porous polyvinyl alcohol microspheres as a potential drug delivery embolization system

The present study aimed to develop a new drug delivery system with efficient drug loading and sustained drug release for potential application in transarterial chemoembolization (TACE). The porous polyvinyl alcohol microspheres (PPVA MS) were prepared by a combination of inverse emulsification and thermal-induced phase separation (TIPS) method, this was followed by the grafting polymerization of sodium 4-styrene sulfonate (SSS) onto the PPVA MS to obtain the grafted PPVA-g-PSSS MS. The prepared PPVA MS showed a well-defined spherical shape with ‘honeycomb-like’ porous structure, which could be readily tailored by adjusting the quenching temperature. In vitro biocompatibility analysis indicated the non-cytotoxic and hemocompatible nature of PPVA MS. The porous structure and presence of ionically charged groups in the PPVA-g-PSSS MS favoured the loading of cationic doxorubicin (DOX) onto the MS through ionic-interactions and demonstrated a sustained drug release pattern. Moreover, the cytotoxicity of DOX-loaded PPVA-g-PSSS (DOX@PPVA-g-PSSS) MS against HepG2 cells and the intracellular uptake of DOX demonstrated the potent in vitro antitumor activity. Furthermore, the central auricular artery embolization in rabbits showed that both the PPVA-g-PSSS and DOX@PPVA-g-PSSS MS could occlude the auricular arteries and induced superior embolization effects, such as progressive ear appearance changes, irreversible parenchymal damage and fibrosis, and ultrastructural alternations in endothelial cells. Besides, the DOX fluorescence was distributed around the embolized arteries, without decreasing its intensity when prolonged embolization up to 15 days. These findings suggest that the newly developed DOX@PPVA-g-PSSS MS could be employed as a promising drug-loaded embolic agent for the treatment of hepatocellular carcinoma.

Achieving reliable partial nitrification and anammox process using polyvinyl alcohol gel beads to treat low-strength ammonia wastewater

In this study, polyvinyl alcohol (PVA) gel beads were used to aid the partial nitrification and anammox process (PN/A) for treating low-strength ammonia wastewater. When treating synthetic and municipal wastewater, the reactor amended with PVA gel beads achieved a total nitrogen removal efficiency of 75.1 ± 8.4% and 66.6 ± 7.0% respectively, while the control reactor without PVA gel beads achieved 63.2 ± 7.8% and 28.2 ± 11.5% respectively. Dissolved oxygen (<0.5 mg O2 L−1) and substrate diffusion in porous PVA gel beads facilitated the formation of microbial stratification in the gel beads. Unclassified Candidatus Brocadiaceae (major anammox bacteria) and Ignavibacterium (major ammonia oxidizing bacteria) enriched in the inside and outside layers of PVA gel beads, which benefited the synergetic cooperation of these bacteria and protecting them from environmental fluctuations. This study provides a promising solution for achieving a reliable PN/A process in mainstream wastewater treatment.

Comparative study on the mechanical behavior of the interface between natural cartilage and artificial cartilage

ABSTRACT This paper studies the deviation rate between natural knee cartilage and polyvinyl alcohol hydrogel artificial cartilage under different compression conditions; when the artificial cartilage is subjected to loads of 10 N, 30 N, 50 N, 70 N, and 90 N, the relationship between Poisson’s ra tio and the stress; simulates the stress-strain/ relationship of adding macromolecular activator to synovial fluid, pure polyvinyl alcohol hydrogel and porous polyvinyl alcohol hydrogel subjected to different compression amount and compression time. The results show that under the same amount of compression, the deviation rates of Mises stress, maximum principal stress and maximum principal strain of the contact surface of artificial cartilage and natural cartilage are stable at 2.996%, 3.912% and 3.67%, respectively. The stress-strain/ deviation rate of the artificial cartilage on the contact surface does not change with time and compression after increasing to a certain value; under the same load, the higher the concentration, the lower the Poisson’s ratio; 20% polyvinyl alcohol hydrogel under a load of 90 N, the artificial cartilage bears a load of 10 N to 90 N, and its Poisson’s ratio decreases from 0.6 to 0.425. Compared with adding DPPC phospholipid or γ-globulin/ alone, adding DPPC phospholipid and γ-globulin/ to synovial fluid has better lubricating properties.

Novel PVA-Based Porous Separators Prepared via Freeze-Drying for Enhancing Performance of Lithium-Ion Batteries

To address the challenges encountered by conventional polyolefin separator for lithium-ion batteries (LIBs) i.e., the porous polyvinyl alcohol (PVA) separator with tailored structure was developed ...

Removal of phosphate at low concentration from water by porous PVA/Al2O3 composites

ABSTRACT The porous polyvinyl alcohol (PVA)/Al2O3 composite by supporting activated alumina on the cross-linked network of PVA has been successfully prepared and its property for the removal of phosphate in aqueous solution was also evaluated. The structure of the PVA/Al2O3 was examined by scanning electron microscopy. It showed that the activated alumina particles with an average size of 1 μm were evenly dispersed and fixed in the cross-linked network structure of PVA. The effects of adsorption time, solution temperature, pH, initial concentration of phosphate, Al2O3 loading rate, dosage and coexisting ions on the phosphate removal were further studied. The results showed that the highest removal phosphate efficiency of 95% can be obtained with the Al2O3 loading rate of PVA/Al2O3 being 60 wt.% at pH of 4 at 30 °C. The maximum adsorption capacities of by PVA/Al2O3 suggested by the Langmuir isothermal model was 10.12 mg/g. The adsorption process of phosphate can be fit well with a pseudo-second-order model (R 2 = 0.9900). The PVA/Al2O3 composite exhibited a high selective adsorption of phosphate in the presence of commonly coexisting anions except the obvious effect of in water. Meanwhile, the PVA/Al2O3 composite can be easily separated and recovered due to the granulation of adsorbent. PVA/Al2O3 composite also shows the excellent properties of regeneration and recycling use with the removal efficiency of phosphate was 88.93%, 88.38% and 94.34% after three cycles, respectively. It can be proposed that the PVA/Al2O3 composite is a promising recyclable adsorbent for removing phosphate at low concentration from aqueous solution.

Therapeutic cobalt ion incorporated in poly(vinyl alcohol)/bioactive glass scaffolds for tissue engineering

Hybrid scaffolds appear as a promising strategy to accelerate bone tissue repair due to their biocompatibility and to combine physical, mechanical and biological characteristics similar to those of human bone tissue. However, there are no studies in hybrid scaffolds using the sol–gel method and a foaming system, with the direct incorporation of cobalt therapeutic ion. In this work, novel porous polyvinyl alcohol polymer (PVA)/bioactive glasses (BG) hybrids scaffolds containing cobalt were obtained, combining the PVA non-toxicity, non-carcinogenicity and processability to the BG bioactivity and osteogenic properties and Co angiogenic effect by the sol–gel and foaming processing method, in order to obtain a new scaffold with angiogenic properties. The effects of Co incorporation on scaffold structure, bioactivity and ion release were evaluated. Cell viability and cell growth assay were performed on human umbilical vein endothelial cells, demonstrating excellent mitochondrial activity without cytotoxicity and cell-friendly environment. Hybrid scaffolds supported fast ion release and an elastic modulus of 20.19 MPa. The presence of cobalt was confirmed by SEM and EDS. Co-incorporated samples showed high porosity and favorable pore size. PVA–BG hybrid scaffolds containing Co showed ionic release rate in the therapeutic range and are promising for angiogenesis in tissue engineering applications.

Biomimetic polyvinyl alcohol/type II collagen hydrogels for cartilage tissue engineering

Type II collagen (Col-II) is one of the important organic components of the cartilage extracellular matrix (ECM). Such natural material is known for its good biocompatibility, but it could not provide a good supporting environment for seed cells due to its rapid degradation and poor strength. In the present work, different contents of Col-II were incorporated into porous polyvinyl alcohol (PVA) to fabricate porous PVA/Col-II composite hydrogels for cartilage tissue engineering. The results illustrate that, after incorporation of Col-II, the elasticity modulus of the composite hydrogels firstly increases, and then decreases (under moisture state). The elasticity modulus of PVA/Col-II (at the ratio of 1:1) hydrogels reaches 11 ± 1.7 KPa, about two-fold higher than pure PVA hydrogels (4.9 ± 0.6 KPa). Meanwhile, all hydrogels exhibit relatively high water content (> 95%) and porosity (> 75%). The degradation analysis indicates that Col-II incorporation induce a high degradation ratio of the composite hydrogels. Cell culture results show PVA/Col-II hydrogels have no negative effects on cells viability and proliferation. The PVA/Col-II hydrogels may possess a potential application in the field of articular cartilage tissue engineering and regeneration.

Fabrication of moth eye-like patterned polystyrene films and their functionalization with polyaniline via interfacial reaction

Moth eye-like patterned (MEP) polystyrene (PS) films with a hexagonal array of microdomes mimicking natural moth eye were fabricated by pouring a PS solution on a honeycomb-patterned porous polyvinyl alcohol film using as a template. The surface of microdomes on the PS MEP film containing benzoyl peroxide (BPO) was functionalized with polyaniline (PANI) through interfacial reaction by using aniline hydrochloride to enhance their functionality of the MEP patterned film. The PANI functionalization on the MEP film was confirmed by UV–visible spectroscopy, scanning electron microscopy and EDX analysis.

Reconfigurable solid-state electrolytes for high performance flexible supercapacitor

To realize high performance and a flexible supercapacitor, it is necessary to address the fundamental issues including low ionic conductivity of solid electrolytes and high interfacial resistance of electrode/electrolyte pairs. Here we present unique solid-state electrolytes by integrating highly engineered nano-porous polyvinyl alcohol (PVA) with super-flat vertically aligned single-walled carbon nanotubes (VA-SWNTs). Highly engineered PVA nano-porous films are fabricated by a generic freeze-thaw process followed by water-miscible solvent treatment in order to create highly controlled nano/microscale pores inside of PVA. Such highly porous PVA films act as both reconfigurable electrolyte template and separator where H3PO4 aqueous solution or ionic liquids can be selectively inserted for a variety of power requirements in flexible electronic applications. Our developed pore formation process is suitable for directly integrating high performance VA-SWNTs electrode as it allows the effective permeation of the polymer electrolyte into nanoscale inter-tube space enabling the easy access and faster transport of ions for higher power capability. This unique entity of reconfigurable electrolyte and nanostructured electrode demonstrates high power and energy densities and remarkable stability after 10,000 charge/discharge cycles.

Green synthesis of porous polyvinyl alcohol membranes functionalized with l‐arginine and their application in the removal of 4‐nitrophenol from aqueous solution

ABSTRACTGreen and single‐step synthesis of porous poly(vinyl alcohol) membrane functionalized with l‐arginine (PVA‐g‐Arg) is presented. Crosslinking, l‐arginine functionalization and pore forming occurred simultaneously by a thermally induced process without using a crosslinker or an initiator. As‐synthesized PVA‐g‐Arg membranes possessed a porous structure with an average pore size of 32–56 μm depending on the amount of l‐arginine. The PVA‐g‐Arg were utilized as adsorbent membranes for the removal of 4‐nitrophenol (4‐NP) from aqueous solutions and demonstrated higher adsorption capacity than that of the unmodified PVA porous membrane. The pseudo‐second‐order described satisfactorily the kinetic adsorption of 4‐NP by the membranes while the isotherms followed both the Langmuir and Freundlich models. The negative values of ΔG° and thermodynamic parameters confirmed that the adsorption of 4‐NP by the PVA‐g‐Arg membranes was spontaneous and exothermic. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47835.

Shape-adaptive composite foams with high expansion and absorption used for massive hemorrhage control and irregular wound treatment

Effective bleeding control is becoming more and more important in the military field and civilian trauma arena. However, traditional hemostats present limitations, they have been proven to be less useful for irregular, deep or penetrating wounds with uncontrollable hemorrhage caused by minor-caliber weapons, shrapnel or explosive devices. Here, a series of porous polyvinyl alcohol (PVA)/alginate composite foams (PACFs) were prepared through crosslinking reaction and lyophilization process. The effect of different content of alginate on the physicochemical properties and hemostatic function of the PACF were evaluated. The results demonstrated that PACF could not only rapidly absorb plasma, but also stimulate blood cells, thus further promoting blood coagulation. In addition, the PACF with higher alginate content showed increased capability to enhance thrombus generation, blood clotting, and blood cells adhesion and aggregation. More importantly, the PACF exhibited over 2000% volume expansion, high flexibility and shape-adaptive ability, and could therefore expand to entirely fill and conform to the shape of wound cavity. The in vivo hemostatic tests further demonstrate the high hemostatic efficiency of PACF. These results suggest that PACF has strong potential as a hemostatic material to be applied for massive hemorrhage control and deep/irregular wounds treatment.