Alcohol Gel Research Articles

Cellulose nanofibrils/polyvinyl alcohol gel microspheres loaded with nickel nanoparticles as catalysts to reduce Cr (VI) by formic acid

Cellulose nanofibrils/polyvinyl alcohol gel microspheres loaded with nickel nanoparticles as catalysts to reduce Cr (VI) by formic acid

A dual physical crosslinking starch-based hydrogel exhibiting high strength, fatigue resistance, excellent biocompatibility, and biodegradability.

Simultaneous realization of high strength, toughness, and fatigue resistance in natural starch-based hydrogel materials is challenging. A facile method of in situ self-assembly and a freeze-thaw cycle was proposed to construct double-network nanocomposite hydrogels of debranched corn starch/polyvinyl alcohol (Gels). Rheology, chemical structure, microstructure, and mechanical property of Gels were investigated. Notably, short linear starch chains were self-assembled into nanoparticles and subsequently into 3D microaggregates, which were tightly wrapped by starch and PVA network. Compared with corn starch single-network and starch/PVA double-network hydrogels, the Gels reached up to a higher compressive strength (ca. 1095.7kPa), and then achieved to ∼20-30-fold improvement in compressive strength. Recovery efficiency exceeded 85% after 20 successive compression loading-unloading cycle tests. Furthermore, the Gels had good biocompatibility to L929 cells. Hence, the high-performance starch hydrogels are thought to serve as a biodegradable and biocompatible material to replace synthetic hydrogels, which can broaden their application fields.

Advanced methodologies for the cleaning of works of art

AbstractCultural heritage assets constitute a fundamental socioeconomic resource, but the actual works of art need to be maintained, counteracting degradation processes, to transfer these benefits to future generations. In particular, the removal of soil, aged coatings, and vandalism/overpaints is one of the most needed interventions in art restoration. Traditional cleaning methodologies, based on classical solution and polymer chemistry, only grant limited control of the cleaning interventions, with the risk of affecting the original components of the artifacts, and often involving the use of toxic or non-environmentally friendly compounds. Alternatively, materials science, colloids, and soft matter have provided valuable and safe solutions in the last decades. This review provides a selection of the most recent and advanced methodologies for the wet cleaning of works of art, spanning from nanostructured cleaning fluids (microemulsions, surfactants swollen micelles) to physical and chemical gels. The new methodologies work on different physico-chemical mechanisms, such as processes for detaching/dewetting, to selectively remove the unwanted layers in sustainable and cost-effective interventions. The best performing systems, like microemulsions confined in “twin-chain” polyvinyl alcohol gels, have been assessed in the cleaning of masterpieces such as works by Pablo Picasso, Jackson Pollock and Roy Lichtenstein. Particular attention is dedicated to “green” chemistry systems, using low-toxicity solvents or bio-based/waste materials to build gel networks. Finally, current trends and future perspectives are given, showing that advanced systems for art cleaning link with transversal fields of crucial importance even beyond Cultural heritage conservation, e.g., detergency, tissue engineering, drug-delivery, food industry and cosmetics.

Lightweight flexible solid-state supercapacitor based on graphene/non-woven fabric electrode

Flexible and lightweight supercapacitors with high safety and fast charging/discharging behavior are ideal power supplies for wearable and portable electronic devices. One of the bottlenecks in this field is to develop high-performance devices with economical materials and applicable fabrication technologies. Here we report an inexpensive, highly flexible, solid-state supercapacitor with graphene coated non-woven fabric (N-rGO) as the collector, electrodeposited Ni/Fe2O3 and polypyrrole (PPY) as the negative and positive materials, respectively. The flexible supercapacitor (FSC) presents a remarkable areal capacitance of 316.2 mF cm−2 with Na2SO4/polyvinyl alcohol gel electrolyte, which delivers an outstanding energy density as high as 43.2 μWh cm−2 at a power density of 0.5 mW cm−2. Furthermore, the device demonstrates excellent electrochemical integrity by well maintaining its capacitance in the cases of cyclic operation and mechanical bending. This research provides a rational design strategy for the facile fabrication of highly flexible, lightweight and low-cost flexible supercapacitors.

Simple fabrication of (CoFe)Se2 @NC electrode materials derived from MOF materials and the electrochemical properties for supercapacitor

Porous carbon nanocomposites and transition metal selenides generated from metal-organic frameworks (MOF) are suitable electrode materials for electrochemical energy storage applications owing to their substantial open space, but their preparation is still fraught with difficulties. Herein, we prepared CoFe Prussian blue-like (CoFe-PBA) nanocubes by a simple co-deposition method and obtained CoFe-PBA@PPy by polymerically assembling CoFe-PBA coated with polypyrrole (PPy), and then successfully prepared (CoFe)Se2 @NC nanocomposites with nitrogen-doped carbon (NC) coated with (CoFe)Se2 by one-step selenization in nitrogen at 400 °C and their structures and morphologies were investigated in depth. This carefully prepared (CoFe)Se2 @NC nanocomposite with an open skeleton structure contains large enough coordination space gaps, porous conduction networks, and a large number of redox-active sites, so that it can largely enhance the kinetic performance of electron and ion transport and facilitate pseudocapacitive reactions, optimize the cycling stability of energy storage devices, and prolong the lifespan of actual devices. Moreover, a stable structure can be maintained during the cycle process and is less likely to collapse, depending on the flexibility and mechanical qualities of the NC. The active material was fixed in nickel foam by a coating method and dried as the electrode for the supercapacitor, and its electrochemical performance was evaluated. The outcomes demonstrated the specific capacitance of the (CoFe)Se2 @NC electrode material could reach 867 F/g at 1 A/g of current density, and its specific capacitance can still reach 640 F/g at a high current density of 5 A/g. Even after 20000 cycles, it still maintains good cycling stability and 99% specific capacitance retention. In addition, we used a brand-new asymmetric all-solid-state supercapacitor (all-solid-state supercapacitor ASC) with (CoFe)Se2 @NC as the positive electrode, Fe2O3/RGO as the negative electrode, and potassium hydroxide/polyvinyl alcohol (KOH/PVA) gel as the electrolyte. The asymmetric all-solid-state supercapacitor of (CoFe)Se2 @NC//Fe2O3/RGO showed remarkable electrochemical performance with an energy density of up to 20 Wh/kg and a power density of 750 W/kg. The supercapacitor was also found to have good cycling stability in the test, with a capacitance retention of 81.1% after 6500 cycles at a current density of 2 A/g.

Reacondicionamiento de la Atención Primaria de Salud para enfrentar la pandemia COVID 19 y percepción de los profesionales sobre las medidas emprendidas en un municipio brasileño

Objective: to describe the Primary Care (PC) scenario regarding reconditioning, equipment and organization of services in order to face the pandemic and to measure the perception by professionals regarding these adaptations. Method: a research with mixed method in a city of the San Pablo state (Brazil). In the quantitative stage, a descriptive cross-sectional study was conducted in 222 PC professionals; the adapted Risk assessment and management of exposure of health care workers in the context of COVID-19 questionnaire by the World Health Organization was implemented. This was followed by the qualitative approach, which consisted in field observation in four PC units. Results: out of the total, 86.94% (n= 193) mentioned that there was an assessment of the signs and symptoms of the users before consultation; 63.96% (n=142) stated that a daily cleaning routine was followed in the waiting room; 92.34% (n= 205) claimed that there were methods available for hand hygiene; 77.48% (n= 172) said that appointments were scheduled in order to maintain physical distancing; 80.12% (n= 178) had not conducted any reconditioning work, and 45.95% (n=102) provided educational materials to users. Conclusions: during field observation, some assessments for signs and symptoms in users were detected; no cleaning actions were observed in the units, it was perceived that there was not enough alcohol gel in the dispenser, there were no marks on the floor to keep distancing, there was a lack of educational materials, and it was not verified that any reconditioning work had been conducted. During data integration, there was convergence regarding physical structure and unit reconditioning.

Fabrication and characterization of colorimetric indicator for Salmon freshness monitoring using agar/polyvinyl alcohol gel and anthocyanin from different plant sources

In order to investigate the sensitivity of anthocyanins from different plant origin as indicators for salmon freshness, nine plant anthocyanins were extracted and fabricated into colorimetric sensor arrays to detect NH3, trimethylamine (TMA), dimethylamine (DMA) to indicate salmon freshness. Rosella anthocyanin had the highest sensitivity for amines, ammonia and salmon. HPLC-MSS analysis indicated that Delphinidin-3 glucoside accounted for 75.48 % of the Rosella anthocyanin. UV–visible spectral analysis showed that the maximum absorbance band of Roselle anthocyanins for acid and alkaline forms were located at 525 nm and 625 nm which showed a relatively broader spectrum than other anthocyanins. An indicator film was fabricated by combining Roselle anthocyanin with agar and polyvinyl alcohol (PVA), which showed visible changes from red to green when employed to monitor the freshness of salmon stored at 4 °C. The ΔE value of Roselle anthocyanin indicator film was changed from 5.94 to >10. The ΔE value also can predict the chemical quality indicators of salmon effectively, especially with characteristic volatile components, and the predictive correlation coefficient was above 0.98. Therefore, the proposed indicating film showed great potential monitoring salmon freshness.

Structural characterization and anti-inflammatory activity of a novel polysaccharide PKP2-1 from Polygonatum kingianum

This study aimed to investigate the structure characterization and antiinflammatory activity of a novel polysaccharide, PKP2-1, from the rhizomes of Polygonatum kingianum Coll. and Hemsl. We isolated a novel polysaccharide, PKP2-1, from the rhizomes of Polygonatum kingianum Coll. and Hemsl. for the first time, which was then successively purified through hot-water extraction, 80% alcohol precipitation, anion exchange and gel permeation chromatography. The in vitro anti-inflammatory activity of PKP2-1 in MH7A cells was assessed using a CCK-8 kit assay. Monosaccharide composition assay revealed that PKP2-1 was mainly composed of glucose, galactose, mannose, and glucuronic acid at an approximate molar ratio of 6:2:2:1. It had a molecular weight of approximately 17.34 kDa. Structural investigation revealed that the backbone of PKP2-1 consisted of (→2, 3)-α-D-Galp(4→, →2)-α-D-Manp(3→, →2)-β-D-Glcp(4→) and α-D-Glcp(3→) residues with side chains (→2)-β-D-Glcp(4→, →1)-α-D-Galp(4→) and α-D-Glcp(3→) branches located at O-3 position of (→2, 3)-α-D-Galp(4→). The in vitro anti-inflammatory activity of PKP2-1 in MH7A cells revealed that PKP2-1 could reduce the expression of IL-11β and IL-6, increase the expression of IL-10 and induce apoptosis of synovial fibroblasts. The PKP2-1 could inhibit MH7A cell growth and potentially be exploited as an anti-inflammatory agent.

Preparation and Study of Polyvinyl Alcohol Gel Structures with Acrylamide and 2-Acrylamido-2-methyl-1-propanesulfonic Acid for Application in Saline Oil Reservoirs for Profile Modification.

Polymer gels can be effectively applied to plug fractured reservoirs and carbonate cave strata. Herein, polyvinyl alcohol (PVA), acrylamide, and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were used as raw materials to prepare interpenetrating three-dimensional network polymer gels using formation saltwater in the Tahe oilfield (Tarim Basin, NW China) as a solvent. The effect of AMPS concentration on the gelation properties of PVA in high-temperature formation saltwater was analyzed. Further, the effect of PVA concentration on the strength and viscoelastic properties of polymer gel was studied. The polymer gel could retain stable continuous entanglement at 130 °C and exhibited satisfactory thermal stability. Continuous step oscillation frequency tests showed that it exhibited an excellent self-healing performance. Scanning electron microscopy images of the simulated core by gel plugging showed that the polymer gel could firmly fill the porous media, indicating that the polymer gel exhibits excellent application prospects in oil and gas reservoirs under high-temperature and high-salinity conditions.

Monkeypox in children and elderly: correspondence.

Monkeypox in children and elderly: correspondence.

Impacts of the COVID-19 pandemic on the reality of Brazilian prisons

Introduction: Since 2020, the world has been suffering the impacts of the new coronavirus, which has assumed the proportions of a global pandemic, a reality that also affects people deprived of liberty and public servants, who work within prison units in Brazil. Objective: To investigate and analyze the impacts and numbers of cases of covid-19 that affected the population deprived of liberty and civil servants in the reality of Brazilian prisons. Design: This research is exploratory and bibliographic in nature, using public domain data, authors and Brazilian legislation. Also, the time lapse of the data reflected here is until April 2021. Results: Information and notifications of cases of covid-19, which affect Brazilian prisons, are not widely publicized and do not follow the update as other segments of the population. In addition, some measures were taken by governments, including the suspension of visits, the purchase of hygiene kits, such as alcohol gel and others. Implications: In this scenario, there was evidence of the indifference and negligence of governments with people deprived of liberty, who do not have their rights enforced in most prisons in the country.

Gel Polymer-Based Composite Solid-State Electrolyte for Long-Cycle-Life Rechargeable Zinc–Air Batteries

Developing high-performance, safe, and flexible solid-state electrolytes (SSEs) for rechargeable solid-state zinc–air batteries (ZABs) is becoming increasingly crucial but remains fraught with tremendous challenges. Herein, a novel multinetwork cross-linked composite gel electrolyte (PVAA-Cellulose) was constructed by introducing poly(acrylic acid) (PAA) and ultrafine cellulose to the poly(vinyl alcohol) (PVA) gel electrolyte. By virtue of the extensive porous network and hydrogen bonding, the PVAA-Cellulose SSEs achieve optimal water retention, thermal stability, and high ionic conductivity of 123 mS cm–1 compared with PVAA (mixture of PVA and PAA). The investigation of the effects of different SSEs on zinc anodes after ZAB cycling reveals that PVAA-Cellulose SSE can effectively inhibit dendrite growth and oxidation byproduct generation on zinc anodes, which contributes to the long-term cycling stability of ZABs. As a result, solid-state ZABs assembled with PVAA-Cellulose SSEs possess a high power density of 74 mW cm–2, a specific capacity of 724 mAh gZn–1, and a long cycle stability of 54 h as well as the outstanding flexibility exhibited by the flexible ZAB devices.

Gel-sol transition of thermoresponsive poly(vinyl alcohol) solution: Validation of the universal critical scaling relations

While undergoing gelation transition, a material passes through a distinctive state called the critical gel state. In the neighborhood of this critical gel state, how viscosity, equilibrium modulus, and relaxation times evolve are correlated by scaling relations, and their universality has been validated for materials undergoing the sol-gel transition. In this work, we extend this approach for the gel-sol transition of a thermoresponsive polymeric system of aqueous poly(vinyl alcohol) (PVOH) gel that passes through the critical state upon increasing temperature. We observe that, in the neighborhood of the critical gel state, the equilibrium modulus and viscosity demonstrate a power law dependence on the relative distance from the critical state in terms of normalized temperature. Furthermore, the relaxation times in the gel and the sol state shows symmetric power law divergence near the critical state. The corresponding critical power law exponents and the dynamic critical exponents computed at the critical gel-sol transition state validate the scaling and hyperscaling relations originally proposed for the critical sol-gel transition very well. Remarkably, the dependence of complex viscosity on frequency at different temperatures shows a comprehensive master curve irrespective of the temperature ramp rate independently in the gel and the sol state. This observation demonstrates how the shape of relaxation time spectrum is independent of both the temperature as well as the ramp rate. Since sol-gel and the gel-sol transitions are opposite to each other, the applicability of the scaling relations validated in this work suggests broader symmetry associated with how the structure evolves around the critical state irrespective of the direction.

Bionic artificial penile Tunica albuginea

Bionic artificial penile Tunica albuginea

Mixed solvent exchange enabled high-performance polymeric gels

Polymeric organohydrogels as emerging soft materials have attracted tremendous interests because of their promising applications in wearable electronics, soft robotics and so on. However, it remains great challenges for the organohydrogels to achieve simultaneously high strength, toughness, stretchability, transparence, biocompatibility and temperature tolerance. Here we report a facile one-step mixed solvent-exchange strategy to prepare high performance organohydrogels (or organogels) by regulating macromolecular noncovalent interaction. The obtained poly(vinyl alcohol) gels have highly dense and homogenous structures comprising abundant hydrogen bonds, entanglements and crystalline domains, originating from the strong interaction of polymer-polymer and polymer-solvent-polymer. Theses gels exhibit excellent mechanical properties with a strength (up to 8.39 ± 0.51 MPa), fracture strain (up to 1127 ± 123%), toughness (52.63 ± 1.98 MJ/m3) and fracture energy (up to 16.34 ± 5.6 kJ m−2), anti-freezing (−65 °C), long-term tolerance (95% of retention coefficient for 14 d), thermal stability (110 °C), transparence (over 90%) and biocompatibility.

Ionic liquid gel electrolyte with a WS2 electrode for highly stable high-voltage solid-state supercapacitors

Highly stable and efficient supercapacitor fabrication is reported using an optimum concentration of 1-butyl-3-methylimidazolium chloride (BMIC) in polyvinyl alcohol (PVA) gel electrolyte and bare WS2-based electrodes.

Minimally invasive esophagectomy for severe stenosis after corrosive esophagitis due to accidental ingestion of alcohol gel: A case report

Minimally invasive esophagectomy for severe stenosis after corrosive esophagitis due to accidental ingestion of alcohol gel: A case report

Development of high strength polyvinyl alcohol gel for water shutoff in carbonate reservoirs

To provide a high-strength, non-resin organic plugging agent for water shutoff in carbonate fracture and cave reservoirs, a high-strength gel was prepared with polyvinyl alcohol 1788 as gelant and p-phthalaldehyde as crosslinker in this study. By selecting latent acids rather than strong acid such as hydrochloric acid and sulfuric acid as catalysts, and by adding clay and sulphonated phenolic resin as stabilisers to the gelation, the drawbacks of short gelation time of polyvinyl alcohol and high dehydration rate of the formed gel soaking in brine were overcame. The evaluation results showed that the gellant composed of 7wt% polyvinyl alcohol, 4wt% clay, 0.3wt% aldehyde crosslinker, 0.25wt% latent acid, 1.5wt% sulfonated phenolic resin, and 0.3wt% hexamethylenetetramine had a gelation time of 2 h at 130 °C. The storage modulus of the gel was up to 2000 Pa, and the dehydration rate of the gel after soaking in synthetic brine for 30 days was less than 15%. Furthermore, the breakthrough pressure gradient in a slim tube with a diameter of 3mm reached 15 MPa / m, which indicated that the gel is a temperature and salinity resistant plugging agent with strong plugging ability.

Ammonia-Nitrogen Reduction in Low Strength Domestic Wastewater by Polyvinyl Alcohol (PVA) Gel Beads

This study aimed to evaluate the efficacy of polyvinyl alcohol (PVA) gel beads as an immobilized biofilm carrier to enhance the reduction rate of Ammonia-Nitrogen (NH3-N) and Chemical Oxygen Demand (COD) in domestic wastewater. Laboratory scale reactors were developed to assess the reduction levels of ammonia-nitrogen and COD with and without PVA gel beads using optimal and non-optimal treatment mode settings based on operation procedures from the sewage treatment plant in Taman Kajang Utama, Selangor. The treatment method used is an activated sludge sequencing batch reactor with a treatment cycle duration of 288 minutes. The findings showed the ammonia-nitrogen reduction by non-optimal treatment mode is more effective, with a reduced rate of 62.96% to 65.71% compared to optimal treatment mode with a reduced rate of 30.94% and treatment without PVA gel beads (optimal and non-optimal) with a reduced rate of 32.41% to 47.85%. The ammonia-nitrogen reduction rate using PVA gel beads for non-optimal treatment mode was significantly increased from 17.86% to 18.82% and complied with ammonia-nitrogen reduction parameter 10mg/L, Standard A of Environmental Quality (Sewage) Regulations 2009 (EQSR 2009). The rate of COD reduction using the non-optimal treatment mode was also more stable, with a reduced rate of 70.68%. It was also found that the COD reduction rate using PVA gel beads for the non-optimal mode was better than the optimal mode, which was 70.68% compared to 42.0%, and both treatment modes complied with COD reduction parameters 120mg/L, Standard A of EQSR 2009.

Semi-solid electrolyte with layered heterometallic low-valent electron-mediator enabling indirect destruction of gaseous toluene

The electrochemical degradation of air pollutants, particularly volatile organic compounds (VOCs), at their gaseous state is a promising method. However, it remains at an infant stage due to sluggish solid–gas electron transfers at room temperature. We established a triphase reaction condition using a semi-solid electrolyte layer between the electrode and membrane to enhance the electron transfer at room temperature. A polyvinyl alcohol (PVA) gel layer was inserted between a bimetallic layered CuNi(CN)4 complex coated Cu foam electrode (TCNi-Cu) and Nafion 324 membrane for the degradation of gaseous toluene. The cyclic voltammetry of TCNi-Cu using a sodium hydroxide-coated copper mesh electrode at a triphase showed Cu1+ and Ni1+ stabilization at −0.7 and −0.9 V, respectively, which was similar to the liquid phase electron transfer behavior. The degradation capacity of gaseous toluene without using electrogenerated TCNi-Cu + PVA gel was 0.54 mg cm2 min−1, whereas that of TCNi-Cu + PVA gel layers was 1.17 mg cm−2min−1, which revealed the mediation effect at a triphase condition. Toluene was converted into oxygen-containing products, such as butanol, propanol, and acetone (without reduction products), which revealed that indirect oxidation occurred at the cathode using an in-situ generated oxidant, such as OH˙ radical. As an electron-mediator, Cu1+ was used to form oxidants for the degradation of toluene at −0.7 V. The toluene removal rate reached 1.4 μmol h−1, with an energy efficiency of 0.15 Wh L−1. This study is the first attempt to describe a liquid-electrolyte-free cathodic half-cell in electrochemical application to VOCs degradation, highlighting the electron transfer at room temperature.