Polyvinyl Alcohol Matrix Research Articles

A hydrogen-bonded curdlan-chitosan/polyvinyl alcohol edible dual functional hydrogel bandage against MRSA promotes wound healing

The most prevalent complication arising from skin injuries is bacterial infection, where pathogenic bacteria proliferate significantly at the wound site, leading to subsequent complications like septic shock and sepsis. Although antibiotics presently effectively manage wound infections caused by common bacteria, the escalating prevalence of antibiotic-resistant strains necessitates urgent novel approaches for addressing such infections. Here, we present CS9P1-RA, a dual functional hydrogel dressing, based on polyvinyl alcohol (PVA) matrix crosslinked through hydrogen bonding. CS9P1-RA combines chitosan (CS), a food-derived antibacterial agent, with the natural compound rosmarinic acid (RA) to specifically target skin injuries caused by MRSA. Computational and molecular biology assays illustrate RA's ability to selectively inhibit the activity of Staphylococcus aureus (S. aureus) serine/threonine phosphatase (Stp1), reducing the S. aureus pathogenicity. CS9P1-RA showcases exceptional antibacterial efficacy (MIC = 1 mg/mL) and demonstrates potency in reducing virulence (IC50 = 7.424 μM on Stp1). Notably, it effectively curbs bacterial growth and accelerates wound healing in the mice model, thereby fulfilling the practical requirements for clinical applications. Moreover, the mechanical properties of CS9P1-RA ensure user comfort during treatment. This work introduces a fresh design paradigm for dressing materials, offering a promising solution for treating skin injuries inflicted by antibiotic-resistant bacterial infections.

Tuning the optical and electrical properties by gamma irradiation of silver nanoparticles decorated graphene oxide on glutaraldehyde crosslinked polyvinyl alcohol matrix

In this study, we propose a facile in-situ approach to fabricate a silver (Ag) NPs decorated graphene oxide (GO) blended with glutaraldehyde (GA) crosslinked polyvinyl alcohol (PVA) matrix, resulting in a PVA/GO-Ag/GA nanocomposite. We investigated how gamma radiation affected the optical and electrical properties of the resulting nanocomposites. Our study reveals that exposure to gamma radiation decreases the band gap of PVA/GO-Ag/GA from 6.06 to 3.35 eV for a 2 kGy dose. The direct current (dc) electrical conductivity was measured to be 2.30 × 10−5 S cm−1 for a 2 kGy dose. Additionally, Jonscher's power law analysis of the alternating current (ac) conductivity behavior suggests that the conduction mechanism in the samples is most likely due to charge carrier transport after gamma irradiation. In conclusion, our findings demonstrate that irradiating PVA/GO-Ag/GA nanocomposites with gamma wavelengths yields tunable electrical and optical properties, making them potential candidates for optoelectronic and electromagnetic applications.

A chitosan derivative/phytic acid polyelectrolyte complex endowing polyvinyl alcohol film with high barrier, flame-retardant, and antibacterial effects

Films with high barrier, flame-retardant, and antibacterial properties are beneficial in terms of food and logistics safety. Herein, a polyelectrolyte complex (PEC) of N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride (HTCC, chitosan derivative) and phytic acid (PA) was successfully prepared and then incorporated into a polyvinyl alcohol (PVA) matrix to fabricate a composite film with satisfactory barrier, fire-retardant, and antibacterial properties. The influence of HTCC/PA (HTPA) on the structural, physical and functional properties of the PVA matrix was investigated. Compared with the PVA film, PVA-HTPA6 film exhibited 3.38 times of flexibility and 83.33 % and 80.64 % of water vapor permeability and oxygen permeability, respectively. Benefiting from HTPA, the PVA-HTPA6 film exhibited outstanding flame-retardant capacity, with a high LOI value (33.30 %) and immediate self-extinguishing behaviour. Furthermore, the HTPA endowed the films with excellent antibacterial properties. Compared with other films, the PVA-HTPA6 film effectively maintained the quality of pork during storage at 4 °C for 9 days. Our findings indicate that the films are promising for packaging and logistics safety with oil-containing foods.

Triple-Mechanism Enhanced Flexible SiO2 Nanofiber Composite Hydrogel with High Stiffness and Toughness for Cartilaginous Ligaments.

Hydrogels are widely used in tissue engineering, soft robotics and wearable electronics. However, it is difficult to achieve both the required toughness and stiffness, which severely hampers their application as load-bearing materials. This study presents a strategy to develop a hard and tough composite hydrogel. Herein, flexible SiO2 nanofibers (SNF) are dispersed homogeneously in a polyvinyl alcohol (PVA) matrix using the synergistic effect of freeze-drying and annealing through the phase separation, the modulation of macromolecular chain movement and the promotion of macromolecular crystallization. When the stress is applied, the strong molecular interaction between PVA and SNF effectively disperses the load damage to the substrate. Freeze-dried and annealed-flexible SiO2 nanofibers/polyvinyl alcohol (FDA-SNF/PVA) reaches a preferred balance between enhanced stiffness (13.71 ± 0.28MPa) and toughness (9.9 ± 0.4MJ m-3). Besides, FDA-SNF/PVA hydrogel has a high tensile strength of 7.84 ± 0.10MPa, super elasticity (no plastic deformation under 100 cycles of stretching), fast deformation recovery ability and excellent mechanical properties that are superior to the other tough PVA hydrogels, providing an effective way to optimize the mechanical properties of hydrogels for potential applications in artificial tendons and ligaments.

The nanocrystalline cellulose from Ananas comosus leaf wastes: An overview to extraction, purification, and applications as curcumin drug delivery system

Currently, antibacterial materials are attracting considerable attention across various fields. In this study, curcumin (Cur) was prepared with nanocrystal cellulose (NCC) into the polyvinyl alcohol (PVA) matrix to improve the functional properties of a pure Cur-NCC-PVA film. The NCC was obtained from Ananas comosus leaves and characterized by Fourier transform infrared (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and particle size analysis. The variations of Cur concentrations (50, 75, and 100 μg) were added to prepare Cur-NCC-PVA films. The release kinetics of Cur from the films was determined using a spectrophotometer and the release kinetic model was obtained using Korsmeyer-Peppas kinetic model. The antibacterial activity of Cur-NCC-PVA films was established using the diffusion method. The results of NCC characteristics showed satisfactory significance. The FTIR showed a functional group of chemical composition that confirmed the removal of non-cellulosic constituents. XRD confirmed the crystallinity index of NCC of 75.89%. Meanwhile, the particle size of NCC of 268.45 nm. The development of Cur-NCC-PVA films showed a uniform yellow color. The release of curcumin in all films was increased depending on the time following the zero-order kinetic reaction. The non-Fickian kinetics demonstrated the mechanism of Cur release from the film. The Cur-NCC-PVA films in Cur concentration of 100 μg were confirmed to have the highest antibacterial activity and significantly different between 50 and 75 μg Cur-NCC-PVA films against Bacillus subtilis, Streptococcus spp., and Escherichia coli. The Cur-NCC-PVA films described the potential activity for topical formulation in skin disease treatment.

Preparation and Characterization of PVA/ CNC/ ε-Polylysine Biocomposites for Potential Food Packaging Application

In recent years, there has been an increasing focus on creating sustainable and biodegradable materials for use in food packaging. The purpose of this study is to examine the impact of incorporating Cellulose Nanocrystals (CNC)/ε-Polylysine (ε-PL) additives into a Polyvinyl Alcohol (PVA) matrix for food packaging. Different filler concentrations and PVA/ε-PL ratios (5:0.3 wt%), (5:0.6 wt.%), and (5:0.9 wt.%) were used to produce the PVA/CNC/ε -PL nanocomposite films through solvent casting. Additionally, PVA and PVA/CNC were prepared for control purposes. The thin film samples were then characterized using a visual inspection, thickness, optical microscopy, FTIR-ATR and XRD. Visual inspection of the nanocomposite films against the logo showed that the increasing weight ratio of CNC/ε-PL did not significantly affect the transparency of the nanocomposites, while those under the polarized optical microscopy exhibited the birefringent patterns observed in the samples with CNC. The FTIR-ATR analysis of the nanocomposite films revealed the functional groups associated with the PVA, CNC, ε-PL, and the mixtures are consistent. The tensile test demonstrated a substantial enhancement in the presence of CNC and CNC/ε-PL. In summary, the PVA/CNC/ε-PL nanocomposites present a promising potential as biodegradable materials for food packaging applications.

Phosphorescent acyclic cucurbituril solid supramolecular multicolour delayed fluorescence behaviour.

Organic photoluminescent macrocyclic hosts have been widely advanced in many fields. Phosphorescent hosts with the ability to bind organic guests have rarely been reported. Herein, acyclic cucurbituril modified with four carboxylic acids (ACB-COOH) is mined to present uncommon purely organic room-temperature phosphorescence (RTP) at 510 nm with a lifetime of 1.86 μs. Its RTP properties are significantly promoted with an extended lifetime up to 2.12 s and considerable quantum yield of 6.29% after assembly with a polyvinyl alcohol (PVA) matrix. By virtue of the intrinsic self-crimping configuration of ACB-COOH, organic guests, including fluorescence dyes (Rhodamine B (RhB) and Pyronin Y (PyY)) and a drug molecule (morphine (Mor)), could be fully encapsulated by ACB-COOH to attain energy transfer involving phosphorescent acyclic cucurbituril. Ultimately, as-prepared systems are successfully exploited to establish multicolor afterglow materials and visible sensing of morphine. As an expansion of phosphorescent acyclic cucurbituril, the host afterglow color can be readily regulated by attaching different aromatic sidewalls. This study develops the fabrication strategies and application scope of a supramolecular phosphorescent host and opens up a new direction for the manufacture of intelligent long-lived luminescent materials.

Synergistic effects of polymaleic acid and di(dioctylpyrophosphato) ethylene titanate on B4C modification in highly filled polymer fibers for improved neutron protection safety and wear comfort of articles

Developing wearable articles with radiation protection safety and wear comfort is one of the urgent issues in that flourishing nuclear technologies are accompanied by increasing radiation threats. However, current wearable articles either display insufficient shielding performance or exhibit poor air and water vapor permeability, which are difficult to meet the growing demand of personal protection in nuclear environments. In this paper, polymaleic acid (PMA) and di(dioctylpyrophosphato) ethylene titanate (DPET) have been used to superficially modify boron carbide (B4C) particles for constructing sufficient hydrogen bonds with polyvinyl alcohol (PVA) matrix. Synergistic effects of PMA and DPET lead to enhanced interfacial interaction. As high as 55 wt% B4C/PVA fibers have been obtained with smooth wet spinning. Their multi-layered fabrics display excellent air and water vapor permeability meanwhile thermal neutron shielding. Three-layer B4C/PVA fabrics have 89.2 % thermal neutron (0.025 eV) shielding rate. In addition, 321.1 mm/s air and 2236.2 g/m2·24 h water vapor permeability have been measured. Besides, the fabrics still show great flexibility in spite of the fibers with extreme filling of inorganic particles. This work provides alternative wear articles to cope with the dilemma of radiation protection safety and wear comfort in neutron radiation environments.

Construction of multiple crosslinked networks for the preparation of high-performance lignin-containing cellulose nanofiber reinforced polyvinyl alcohol films

Polyvinyl alcohol (PVA) film, a promising alternative to non-biodegradable plastic packaging films for food and medical packaging, is limited by poor water resistance. In this work, a simple solvent evaporation self-assembly was used to construct a nanophase separation structure to establish dense interfacial hydrogen bonding, covalent bonding and iron metal ion coordination interactions between lignin-containing cellulose nanofibers (LCNFs) and PVA matrix to improve the interfacial force and solve the problem of poor compatibility of LCNFs in PVA. The iron ion (Fe3+) coordination tended to combine with the more active lignin phenolic hydroxyl group to construct the nanophase separation structure. Covalent crosslinking of glutaraldehyde (GA) improved the interfacial compatibility of PVA/LCNF films, enhanced the interfacial bonding and formed a homogeneous structure. The multi-nanophase structures improved the strength and elastic modulus of the PVA/LCNF film and provided the films with extremely low water absorption, water vapor transmission rate and excellent UV-shielding. Compared with pure PVA film, PVA-10L-5Fe-3GA film had about 106.9 % higher tensile strength, 93.9 % lower water absorption and 93.4 % lower mass loss, 69.8 % lower water vapor transmission coefficient, and was able to shield UV at 200–400 nm, which is highly expected to be used in packaging films.

Molecule structure design by synergistic crosslinking in the PVA matrix and its physical properties regulation

Environmentally friendly polyvinyl alcohol (PVA) has a broad range of potential applications in membrane science. This article describes the co-crosslinking used to adjust the water resistance and swelling level of PVA molecules and broaden their applications. To integrate functional groups and carbon chains in the PVA matrix, the crosslinking agents glutaraldehyde (GA) and ammonium persulfate (APS) were used, the complexity of the PVA crosslinking structure can be dramatically increased. The results showed that the crosslinked PVA film's water resistance and thermal stability qualities have improved. The synergistic crosslinked film's swelling percentage, maximum decomposition temperature, and diffusion constant altered from 590 %, 242.9 ℃, and 1.13 × 10−11 m2/s to 129 %, 344.7 ℃, 0.02 × 10−11 m2/s respectively. The synergistic crosslinked film's swelling percentage, maximum decomposition temperature, and diffusion constant were altered with the molecule structure design. This method can give a novel reference to the performances design of hydrophilic polymers in different applications.

Polyvinyl alcohol films incorporated with clove essential oil emulsions stabilized by soy protein isolate-derived amyloid fibrils: Fabrication, characterization, and its application for active packaging

This study aimed to prepare a novel emulsion film with high stability, using soy protein-derived amyloid fibrils (SAFs) as an emulsifier incorporating clove essential oil (CEO) as the active component, and the polyvinyl alcohol (PVA) matrix to stabilize the system. The results demonstrated that SAFs can successfully stabilize CEO. Emulsion prepared by SAFS and CEO (SAC) exhibited a small droplet size and better dispersibility compared with SPI and CEO (SC) emulsion. According to FT-IR results, PVA addition increased the hydrogen bond interactions among emulsion film components, thus further reinforcing the protein matrix, increasing the tensile strength (TS) (41.18 MPa) and elongation at break (E) (121.62 %) of the films. The uniform appearance of SAC-PVA (SACP) emulsion films was confirmed by SEM images. Furthermore, SACP emulsion films show distinctive barrier properties, optical properties, and outstanding antioxidant properties. Finally, emulsion films exhibited excellent preservation of strawberries, resulting in an effective decline of the decay rate.

Nanostructural Characterization of Luminescent Polyvinyl Alcohol/Graphene Quantum Dots Nanocomposite Films.

This study focuses on the fabrication of polymer nanocomposite films using polyvinyl alcohol (PVA)/graphene quantum dots (GQDs). We investigate the relationship between the structural, thermal, and nanoscale morphological properties of these films and their photoluminescent response. Although according to X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and differential thermal analysis (DTA), the incorporation of GQDs does not significantly affect the percentage crystallinity of the PVA matrix, for a range of added GQD concentrations, atomic force microscopy (AFM) showed the formation of islands with apparent crystalline morphology on the surface of the PVA/GQD films. This observation suggests that GQDs presumably act as nucleating agents for island growth. The incorporation of GQDs also led to the formation of characteristic surface pores with increased stiffness and frictional contrast, as indicated by ultrasonic force microscopy (UFM) and frictional force microscopy (FFM) data. The photoluminescence (PL) spectra of the films were found to depend both on the amount of GQDs incorporated and on the film morphology. For GQD loads >1.2%wt, a GQD-related band was observed at ~1650 cm-1 in FT-IR, along with an increase in the PL band at lower energy. For a load of ~2%wt GQDs, the surface morphology was characterized by extended cluster aggregates with lower stiffness and friction than the surrounding matrix, and the PL signal decreased.

Multifunctional and pH‐responsive dialdehyde cellulose/polyvinyl alcohol composite film reinforced with curcumin

AbstractThe rational design of food packaging films with good antimicrobial activity, antioxidant activity, and monitorability is of great importance in intelligent packaging. In this study, an active composite film was prepared by adding curcumin to a dialdehyde cellulose (DAC)/polyvinyl alcohol (PVA) matrix. It was found that the Cur/DAC/PVA composite film exhibited optimal tensile strength at 30°C. The tensile strength of the composite film control PVA/DAC film was observed to increase by 176% due to the affection of hydrogen bonding. Under the influence of curcumin, the UV barrier property and antioxidant activity of the composite film were significantly increased, and the ABTS+• was removed by 0.5Cur/DAC/PVA up to 88% at low curcumin content. The water solubility and water vapor permeability were both reduced to some degree. It was also observed that composite film displayed an inhibitory effect on the growth of Staphylococcus aureus bacteria. Meanwhile, the Ritger and Peppas release model was used to study the release control capability of curcumin. Furthermore, the Cur/DAC/PVA composite film demonstrated excellent color response to pH, which it they could be used for intelligent packaging with real‐time visual monitoring.

Carbon dots-based fluorescent films to act as a potential antioxidant agent and pH ratiometric sensor for skin applications

The wound healing process is accompanied by changes in pH values. Monitoring this physicochemical parameter can indicate the effectiveness of the applied treatment and act as early identification of wound infection. This study focuses on the development of a fluorescent film-based polyvinyl alcohol (PVA) and carbon dots (CDs) derived from lemon bagasse (CD-L) and ortho-phenylenediamine (CD-oPD) named to act as antioxidants and potential ratiometric fluorescent pH sensors, in wound applications. The I460/I550 intensity ratio, as a function of pH value for the dual-system CDs prepared from the mixture of CD-L and CD-oPD, named CD-L/oPD, was investigated. The fit corresponded to a sigmoidal function in the pH range of 5–10, with a relationship having a r2 = 0.992. The variation in the values of the I460/I550 ratio allows for the visualization of the color change from yellowish-green to green with increasing pH. Through a simulated ex vivo pig skin model, it was possible to note that the films prepared from mixed of the CD-L and CD-oPD carbon dots incorporated in a matrix PVA named CD-L/oPD-F was more efficient at visually discriminating color in relation to changes in pH than the films prepared from both individual CD-L (CD-L-F) and CD-oPD (CD-oPD-F) carbon dots. CD-L and CD-oPD demonstrated antioxidant capacity against reactive oxygen species (ROS). The IC50 values for CD-L and CD-oPD were 56.7 and 39.5 μg mL−1 in the DPPH● inhibition assay, and 25.1 and 63.4 μg mL−1 in the HOCl scavenging one, respectively. MTT viability assays using human non-tumoral skin fibroblast (HFF-1) cell showed a cell survival rate of over 80% for both CDs up to a concentration of 1,000 μg mL−1. Finally, the developed films can act in a bifunctional way, by monitoring healing through pH changes and by acting as an antioxidant agent in the treatment of wounds.

Thin selective layered mixed matrix membranes (MMMs) with defective UiO-66 induced interface engineering toward highly enhanced pervaporation performance

The thin selective layer in mixed matrix membranes (MMMs) with high pervaporation performance is in high demand because of their high productivity. However, it has been limited because of the defective interface of sieving fillers in MMMs and the instability to permeate molecules, resulting in instability and degradation in the membrane state and pervaporation performance. Herein, we synthesized defective UiO-66 (DUiO66) by controlling the concentration of the reactants and then analyzed the characteristics of the defects. We confirmed that defects of the missing linker are induced in its structure, and DUiO66 (1.324) has a higher defect density than conventional UiO66 (1.064). Those led to the highly enhanced interface of DUiO66 with polyvinyl alcohol (PVA) matrix and water solvent, resulting in mechanical stability and a uniformed thin selective layer. Crosslinked thin-layered PVA MMMs with DUiO66 (XPDUiO66) were applied to the flat-sheet type and hollow fiber type membranes and then examined for the pervaporation performance to separate IPA/water solution (mainly 80/20 and 90/10 (w/w)). The thin-layered flat type and hollow fiber type XPDUiO66 revealed a dramatic increase in flux by 5.6 and 5.0 times compared to the free-standing type MMM while almost maintaining selectivity. Notably, the flat-sheet type XPDUiO66-2 increased around 606% and 1,664% in PSI relative to XPVA at a feed solution of 80/20 and 90/10 (w/w) IPA/water, respectively. The current work offers significant findings on the relationship between defective MOF-applied MMMs and pervaporation performance.

Surface-Enhanced Raman Scattering Studies of Au-Ag Bimetallic Nanoparticles with a Tunable Surface Plasmon Resonance Wavelength Synthesized by Picosecond Laser Irradiation

Here, we present a simple and green method of preparing Au-Ag bimetallic nanoparticles (NPs) with a tunable surface plasmon resonance (SPR) wavelength by using picosecond laser irradiation. Au-Ag alloy NPs have been produced by irradiating the solutions containing respective metallic salts in a polyvinyl alcohol (PVA) matrix using a picosecond laser in a single-step process. The SPR wavelength of the Au-Ag bimetallic NPs is observed to be shifted/changed with the Au-Ag concentration and the laser irradiation parameters. The Au-Ag NPs embedded in the PVA matrix are advantageous for Surface-Enhanced Raman scattering (SERS) applications. The estimated enhancement factors (EFs) were observed to vary as a function of conditions of the Au-Ag bimetallic alloy NPs synthesis and also on the concentration of Au at a fixed input fluence of irradiation. The SERS active platforms of Au-Ag bimetallic NPs showed EFs as high as of the order of 108 for Crystal Violet (CV) dye samples at nano molar concentrations. The present study demonstrates a simple, single-step, and green method that fabricates Au-Ag alloy-based nanocomposites suitable for SERS investigations with significantly higher orders of EFs.

Unique Visualization Growth Process of Long-Lived Room Temperature Phosphorescence in Polymer System.

Recently, embedding organic phosphors into the polyvinyl alcohol (PVA) matrix has emerged as a convenient strategy to obtain efficient long-lived room temperature phosphorescence (RTP) via forming strong intermolecular hydrogen bonds with organic phosphors to minimize nonradiative relaxations. Regrettably, it is discovered that PVA is unable to trigger RTP emission when a novel functional phosphor THBE containing six extended biphenyl formaldehyde arms is doped into PVA matrix. Surprisingly, the excellent long-lived RTP emission can be easily obtained by doping THBE into PVA analogs, poly(vinyl alcohol-co-ethylene) (PVA-co-PE). The unique visualization growth process (i.e., white streak generation) of long-lived RTP is observed by UV light-driven aggregation of functional molecules THBE in PVA-co-PE matrix. The phosphorescent intensity of the luminescent film is enhanced by 55 times, from 729 to 40,785 a.u., and its phosphorescence lifetime is increased by 38 times, from 37.08 to 1415.41ms. Due to the dynamically reversible RTP performance, as well as the permeability, flexibility, and wrinkle-free properties of the luminescent film, it can be utilized to create cutting-edge information storage devices.

Graphene nanoribbon doped PVA nanocomposites for improved UVC blocking and luminescence down‐shifting applications

AbstractGraphene nanoribbon (GNR) is quasi‐one dimensional carbon based nanomaterial, distinct from graphene and less explored nanofiller in optical and optoelectronic applications. Herein flexible poly vinyl alcohol (PVA) nanocomposites of 0, 0.25, 0.5 and 0.75 wt % compositions of GNR were prepared by using solution intercalation technique and characterized by spectroscopic methods to assess their structural and optical characteristics. The characterization of PVA@GNR nanocomposites revealed Vander Waals binding of GNR to PVA chains and also considerable crystallographic changes in PVA matrix upon the incorporation of GNR. The optical investigations showed UV‐visible absorption in the wavelength range of 200–280 and 350–520 nm which enhanced on increase in GNR dopant concentration. The decrease in the optical band gap and Urbach energy was also observed for the nanocomposites with increase in dopant concentrations thereby suggesting the formation of localized states in the forbidden band region. The refractive index, absorption coefficient, extinction coefficient and optical conductivity of PVA nanocomposites showed excellent agreement with the band gap revelations and indicated UVC light blocking properties in the wavelength of 200–280 nm. Further, the GNR incorporated PVA nanocomposites exhibited improved thermal stability, wettability transitions (hydrophilic to near hydrophilic) and excellent luminescent down‐conversion properties with a high Stokes's shift (100 nm) compared to pristine PVA nanocomposites. The study concludes that the proposed PVA@GNR nanocomposites can ideally fit optical and photovoltaic device applications owing to their transparency coupled with UV blocking and luminescence down‐shifting attributes.

A shining transmutation of lignin into multicolor carbon dots via the dynamic solvent-fractionation engineering

As a fascinating luminescent subclass, the rapid growth of versatile carbon dots from ideally sustainable biomass has been shouldering the duty of relieving energy and environment pressures that is committed to carbon neutrality. Despite the renewable lignin with conjugated aromatic structure, tunable linkages and functional species (e.g.,–OH, –COOH and –OCH3), the fabrication of multicolor lignin-derived carbon dots (LCDs) covering the red-emissive luminescence is awkward by lacking the task-specific techniques and modulating mechanisms. Herein, a library of blue, green and red-emissive LCDs is built through a stepwise solvent-fractionation engineering with dynamic ethanol sieving and dichloromethane/water extraction. By refined lignin, it is revealed that their average molecular weights and –OH/COOH contents dominate the nanosize, reactivity, lifetime, and photophysical features of LCDs. We then showcase the gradient lignin structure to involve LCDs properties capable of driving their potential functions in the multi-target sensing and solid-state luminescent films. Monitoring tetracycline and metal-ions (Fe3+, Al3+ and/or Ag+) with the ideal selectivity and sensitivity within a broad concentration is accomplished via evaluating the linear correlations. Transparent solid-state luminescent composite films that demonstrate the promising scalability of reserving perishable fruit are successfully prepared using red-emitting LCDs as additives in polyvinyl alcohol matrix. Hence the in-depth understanding of lignin chemistry will provide a technical guidance to achieving multicolor LCDs with tailored fluorescence performances and functionalities.

Enhancing thermal stability, mechanical properties, and flammability of polyvinyl alcohol using amide‐functionalized hydrogel and zinc oxide nanoparticles

AbstractNew polyvinyl alcohol (PVA) nanocomposites containing zinc oxide (ZnO) nanoparticles and a hydrogel were prepared by the solution casting method. ZnO nanoparticles grafted co‐polymer (Zn‐g‐CP) was synthesized through the reaction of ZnO nanoparticles with vinyltriethoxysilane and then the radical co‐polymerization with 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS). The amide functionalized hydrogel was prepared via an in situ polymerization of acrylamide and N,N′‐methylene bisacrylamide (MBA) as a crosslinker in a solution of PVA. The corresponding results indicated that the simultaneous presence of both Zn‐g‐CP and hydrogel could significantly increase flammability, thermal stability, and the tensile strength of PVA. The results of the X‐ray diffraction (XRD) and field‐emission scanning electron microscopy (FE‐SEM) indicated a uniform dispersion of ZnO nanoparticles and an enhanced compatibility with the PVA matrix. Thermogravimetric analysis (TGA) in both N2 and air atmospheres, indicated that the temperature at 50% mass loss and the char residue values of PVA nanocomposite containing 6 wt% of Zn‐g‐CP in the presence of hydrogel (PZH12 sample) were enhanced, which was evident by the increased thermal decomposition temperature. The peak of heat release rate (pHRR) value of the PZH12 sample was obtained 56.9% lower than that of the neat PVA demonstrating a significant improvement in flammability behavior. Also, the flame‐retardant performance of PZH12 improved, as compared to the pure PVA, with UL‐94 V1 rating and LOI of 27.2%. The tensile strength (Ts) and elongation at break (EB) values for the mentioned sample enhanced by 62.5% and 7.2% compared to those of the neat PVA, respectively.Highlights Preparation of vinyl functionalized ZnO nanoparticles (VZnO). ZnO grafted co‐polymer (Zn‐g‐CP) from a radical polymerization on the VZnO surface. Preparation of an amide‐sulfonated hydrogel in the PVA solution. The effect investigation of hydrogel and Zn‐g‐CP on the PVA properties. The results exhibited the enhanced flame retardancy and mechanical properties of PVA.