Search Results (625)

Gold nanoparticles (AuNPs) are attracting more and more attention in life sciences, especially due to their versatile physicochemical properties whereby their colloidal stability in water and organic solvents is crucial. In this study, a systematic comparison of different polymers, synthesis methods and solvents was carried out. The AuNPs were synthesized using the ligand exchange reaction/postsynthetic addition reaction (PAR) and the one-pot synthesis with the polymers poly(vinyl alcohol) (PVA), poly(ethylene glycol) (PEG), poly(vinylpyrrolidone) (PVP) and poly(acrylic acid) (PAA), each with different molar weight averages. Analysis of the AuNP@Polymer conjugates by transmission electron microscopy (TEM) finds essentially unchanged gold nanoparticle core sizes of 11–18 or 11–19 nm in water and ethanol, respectively. The hydrodynamic diameter from dynamic light scattering (DLS) lies largely in the range from 20 to 70 nm and ultraviolet-visible spectroscopy (UV-Vis) showed gold plasmon resonance band maxima between 517 and 531 nm over both synthesis methods and solvents for most samples. The polymer PVA showed the best colloidal stability in both synthesis methods, both in water and after transfer to ethanol. An increased instability in ethanol could only be noted for the PEG coated samples. For the polymers PVP and PAA, the stability depended more specifically on the combination of synthesis method, polymer molecular weight and solvent. Full article

Conductive polymer hydrogels have attracted extensive attention in wearable devices, soft machinery, and energy storage due to their excellent mechanical and conductive properties. However, their preparation is often complex, expensive, and time-consuming. Herein, we report a facile precipitation method to prepare conductive polymer composite hydrogels composed of poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA), and poly(3,4-ethylenedioxythiophene) (PEDOT) via straightforward solution blending and centrifugation. During the preparation, PEDOT, grown along the PAA template, is uniformly dispersed in the hydrogel matrix. After shaping and rinsing, the PEDOT/PAA/PVA hydrogel shows good mechanical and electrical properties, with a conductivity of 4.065 S/m and a Young’s modulus of 311.6 kPa. As a strain sensor, it has a sensitivity of 1.86 within 0–100% strain and a response time of 400 ms. As a bioelectrode, it exhibits lower contact impedance than commercially available electrodes and showed no signs of skin irritation in the test. The method’s versatility is confirmed by the observation of similar performance of hydrogels with different compositions (e.g., polyaniline (PANI)/PAA/PVA). These results demonstrate the broad applicability of the method. Full article

Electrochemical water splitting has emerged as a pivotal strategy for advancing sustainable and renewable energy technologies. However, its practical deployment is often hampered by sluggish reaction kinetics, large overpotentials, and the high cost of efficient electrocatalysts. To overcome these critical challenges, a novel bifunctional electrocatalyst based on electropolymerized CeO₂-NiO with polyacrylic acid (Ce-Ni-PAA) has been rationally engineered for overall water splitting. The strategic incorporation of conductive polymer framework enables effective modulation of the local electronic structure, enhances charge transport pathways, and maximizes the density of electrochemically accessible active sites, thereby substantially boosting catalytic performance. When evaluated in a 1 M KOH alkaline medium, the optimized Ce-Ni-PAA_0.5/NF hybrid demonstrates remarkable catalytic activity with 366.5 mV overpotential at 50 mA cm⁻², coupled with lower Tafel slope of 93.5 mV dec⁻¹. Additionally, the Ce-Ni-PAA_0.5/NF electrocatalyst exhibits exceptional ECSA of 1092.3 cm², which confirms the presence of a significantly larger number of electrochemically active sites. The electrocatalyst retains its performance even after 5000 continuous cycles of operation. The superior performance is attributed to the synergistic effects arising from the enriched composition, efficient electron transport channels, and abundant catalytic centers. Collectively, this study not only highlights the significance of rational structural and compositional design but also offers valuable insights toward the development of next-generation, cost-effective bifunctional electrocatalysts with strong potential for scalable water splitting and clean energy applications. Full article

An increase in the production of cationic dyes is expected over the next decade, which will have an impact on health and the environment. This work reports an adsorbent hydrogel composed of poly(acrylic acid) [poly(AA)] and Fe₃O₄ particles, prepared by radical polymerization and in situ co-precipitation of Fe³⁺ and Fe²⁺. This Fe₃O₄/poly(AA) composite hydrogel was used to evaluate its potential for removing the cationic dyes methylene blue (MB) and crystal violet (CV) from aqueous solutions. Instrumental characterization of the hydrogel was performed by FTIR, XRD, TGA, VSM, and physicochemical analysis (swelling and response to changes in pH). The results show that the incorporation of Fe₃O₄ particles improves the adsorption capacity of MB and CV dyes to a maximum adsorption of 571 and 321 mg/g, respectively, under the best conditions (pH 6.8, dose 1 g/L, time 24 h). The adsorption data best fit the pseudo-first order (PFO) kinetic model and the Freundlich isothermal model, indicating mass transfer via internal and/or external diffusion and active sites with different adsorption potentials. Moreover, the thermodynamic analysis confirmed that the adsorption process was spontaneous and exothermic, with physisorption as the dominant mechanism. In addition, the Fe₃O₄/poly(AA) hydrogel is capable of removing 95% of the dyes after ten consecutive adsorption–desorption cycles, demonstrating the potential of hydrogels loaded with Fe₃O₄ particles for the treatment of wastewater contaminated with dyes. Full article

A novel glucose biosensor is developed based on a tilted fiber Bragg grating (TFBG) functionalized with a pH-responsive polyelectrolyte multilayer membrane, onto which glucose oxidase (GOD) is immobilized. The sensing film is constructed via layer-by-layer self-assembly of poly(ethylenimine) (PEI) and poly(acrylic acid) (PAA), which undergoes reversible swelling and refractive index (RI) changes in response to local pH variations. These changes are transduced into measurable shifts in the resonance wavelengths of TFBG cladding modes. The catalytic action of GOD oxidizes glucose to gluconic acid, thereby modulating the interfacial pH and actuating the polyelectrolyte membrane. With an optimized (PEI/PAA)₄(PEI/GOD)₁ structure, the biosensor achieves highly sensitive glucose detection, featuring a wide measurement range (10⁻⁸ to 10⁻² M), a low detection limit of 27.7 nM, and a fast response time of ~60 s. It also demonstrates excellent specificity and robust performance in complex biological matrices such as rabbit serum and artificial urine, with recovery rates of 93–102%, highlighting its strong potential for point-of-care testing applications. This platform offers significant advantages in stability, temperature insensitivity, and miniaturization, making it well-suited for clinical glucose monitoring and disease management. Full article

The application of organic amendments and humic acids (HA) often ameliorates saline soils, but the mechanisms responsible for their positive action have never been fully clarified. HA from four different origins (Elliott soil—EHA, peat—PHA, leonardite—LHA and compost—CHA) and polyacrylic acid (PAA) were characterized by acid–base titrations and ¹H-NMR spectroscopy and tested in laboratory experiments by measuring changes in electric conductivity (EC) and pH following micro-additions of Na₂CO₃ or NaCl. The effective salinity amelioration potential (SAP_eff) of HA, which expresses the amount of Na₂CO₃ neutralized per unit weight of HA at a given pH, was calculated. PAA had the highest capacity of mitigation, corresponding to 49.9 mg Na₂CO₃ g⁻¹, followed by LHA, EHA and PHA, whose SAP_eff values were similar and only slightly lower, and with CHA having the lowest value (25.1 mg Na₂CO₃ g⁻¹ HA). All substances failed to display any effect at constant pH when NaCl was the only salt present. The dissociation of acid groups, when HA become exposed to a more alkaline pH, produces an excess of negative charges that attracts more cations within the diffuse double layer. Because of the slower diffusion of HA and their tendency to aggregate at high ionic strengths, this action reduces the osmolarity of the soil solution and therefore mitigates salinity stress. Full article

The application of lipases in biphasic oil–water emulsions offers an efficient and sustainable alternative to conventional chemical synthesis. However, the natural immiscibility of these phases is a substantial limitation. To address this issue, we proposed a dual-stabilized emulsion system combining a nonionic emulsifier (Kolliphor^® CS 20) and cross-linked polyacrylic acid (Carbopol^® Ultrez 10), exceeding conventional single-stabilized systems. The activity of Candida antarctica lipase B (CALB), both in its free form and immobilized onto an IB-D152 support, was investigated in the prepared emulsion system. The olive oil emulsion stabilized with 10.0% Kolliphor^® CS 20 and 0.1% Carbopol^® Ultrez 10 significantly enhanced the lipolytic activity of immobilized CALB (156.27 ± 3.91 U/g of support), compared to the activity obtained in the emulsion stabilized only with 10.0% Kolliphor^® CS 20 (71.11 ± 3.86 U/g of support). On the other hand, the activity of immobilized CALB in the emulsion containing 5.0% Kolliphor^® CS 20 and 0.1% Carbopol^® Ultrez 10 (62.22 ± 3.85 U/g of support) was lower than in the corresponding system without Carbopol^® Ultrez 10 (72.03 ± 4.63 U/g of support), stabilized with only 5.0% Kolliphor^® CS 20. Furthermore, immobilization onto IB-D152 led to lipase hyperactivation, with activity approximately eight-fold higher than that of free CALB. This dual emulsion stabilization strategy not only improves emulsion stability but also enhances lipase activity, offering new opportunities for scalable, high-performance biocatalysis using emulsions in industrial applications. Full article

In this study, interface models of different polymer fibers and geopolymer products were constructed and the microscopic action mechanisms behind different polar oxygen-containing functional groups were revealed by analyzing the static structure of the interface and fiber pull-out process. The results show that, compared with polypropylene (PP) fibers, there is a strong hydrogen bond interaction in polyvinyl alcohol (PVA) and polyacrylic acid (PAA) fibers, respectively. After reaching equilibrium, the interlayer spacing of PVA and PAA fibers becomes smaller. At the interface, there are both ionic bonds and hydrogen-bonding connections, and the stability of ionic bonds is greater than that of hydrogen bonds. As the loading rate increases, the shear strength shows an increasing trend. Since the carboxyl of PAA fibers has stronger polarity than the hydroxyl of PVA fibers, the end deformation of the matrix is greater. During the pull-out process, the influence of the loading rate is greater than the anchoring effect of hydroxyl in PVA fibers but lower than that of carboxyl in PAA fibers. Full article

This study evaluated a biomimetic filler strategy for two-step universal dental adhesives by integrating amine-functionalized mesoporous silica nanoparticles (MSNs) loaded with polyacrylic acid-stabilized amorphous calcium phosphate (PA–ACP) into the primer phase. MSNs were synthesized and characterized by FTIR, N₂ sorption (BET), and HRTEM to confirm structural integrity and effective PA–ACP loading. Two commercial adhesives (G2 Bond and OptiBond eXTRa) were modified by incorporating different volumes fractions (10, 15, 20 vol%) of PA–ACP/MSN. Wettability (contact angle), microtensile bond strength (μTBS), and cytotoxicity (indirect MTT assay using human periodontal ligament fibroblasts, HPLFs) were assessed. The results demonstrated that incorporating up to 15 vol% PA–ACP/MSN maintained favorable wettability and bond strength, comparable to those of the unmodified controls. At 20 vol%, significant increases in contact angles and reductions in bond strength indicated impaired primer infiltration. Cytotoxicity testing confirmed high fibroblast viability (>70%) across all tested concentrations, verifying the biocompatibility of PA–ACP/MSN-filled primers. This work confirms the feasibility of a biomimetic adhesive design using PA–ACP/MSN in the primer phase without compromising immediate wettability and immediate μTBS up to 15 vol%. Remineralization is a potential capability that requires verification in future studies. Full article

Enhancing the safety of lithium-ion batteries (LIBs) by replacing flammable electrolytes is a key challenge. Ionic liquid (IL)-based electrolytes are considered an interesting alternative due to their thermal and chemical stability, high voltage stability window, and tunable properties. This study investigates the electrochemical behavior of two newly synthesized ILs, comparing them to conventional alkyl carbonate-based electrolytes. Nitrogen-doped carbon silicon oxycarbide (NC-SiOC), used as the active material in negative electrodes, was combined with two polymeric binders: poly(acrylic acid) (PAA) and poly(acrylonitrile) (PAN). NC-SiOC/PAN electrodes exhibited a significantly higher initial charge capacity—approximately 25–30% greater than their PAA-based counterparts in the first cycle at 0.1 A g⁻¹ (850–990 mAh g⁻¹ vs. 600–700 mAh g⁻¹), and demonstrated an improved initial Coulombic efficiency (67% vs. 62%). Long-term cycling stability over 1000 cycles at 1.6 A g⁻¹ retained 75–80% of the initial 0.1 A g⁻¹ capacity. This outstanding performance is attributed to the synergistic effects of nitrogen-rich carbonaceous phases within the NC-SiOC material and the cyclized-PAN binder, which facilitate structural stability by accommodating volumetric changes and enhancing solid electrolyte interphase (SEI) stability. Notably, despite the lower ionic transport properties of the IL electrolytes, their incorporation did not compromise performance, supporting their feasibility as safer electrolyte alternatives. These findings offer one of the most promising electrochemical performances reported for SiOC materials to date. Full article

This study examines the effects of three polymer binders—polyvinyl alcohol (PVA), polyethylene glycol (PEG), and polyacrylic acid (PAA) on the mechanical properties and dry–wet cycle corrosion resistance of cement mortar at different dosages (1–4%). Mechanical testing combined with scanning electron microscopy (SEM) and molecular dynamics (MD) simulations was conducted to validate the experimental findings and reveal the underlying mechanisms. Results show that polymers reduce early-age strength but improve flexural performance, and at low dosage, enhance compressive strength. PVA and PAA exhibited a pronounced improvement in mechanical strength while PVA and PEG showed a significant improvement in wet cycle corrosion resistance. SEM observations indicated that polymers encapsulate cement particles, enhancing interfacial bonding while partially inhibiting hydration. MD simulations revealed that PVA and PAA interact with Ca²⁺ via Ca-O coordination, while PEG primarily forms hydrogen bonds, resulting in distinct water-binding capacities (PEG > PVA > PAA). These interactions explain the enhanced mechanism of mechanical and dry–wet cycle resistance properties. This work combined experimental and molecular-level validation to clarify how polymer–matrix and polymer–water interactions govern mechanical and durability, respectively. The findings provide theoretical and practical guidance for designing advanced polymer binders with tailored interfacial adhesion and water absorption properties to improve cementitious materials. Full article

Polymer binders are crucial components in providing both mechanical support and chemical stability to the structure of porous Li-ion electrodes. Particularly in silicon anodes, the active material undergoes substantial volume expansion of up to 275%. Due to the mechanical constraint of the current collector, these silicon materials tend to expand in the normal direction while exhibiting substantial particle rearrangement and plastic deformation. Conventional rigid binders such as polyacrylic acid (PAA) and polyimide (PI), while providing satisfactory initial capacity, do not eliminate diminished long-term performance. Our research attempts to develop binder formulations that can accommodate sufficient flexibility for the substantial volume changes of silicon particles. Specifically, we explore the use of short-chain polymer binders and a strategic blend of binders with different molecular weights. Experiments have demonstrated that cells combining both long- and short-chain PAA binders delivered an initial capacity of 2200 mAh/g at a 0.1C rate, compared to 1700 mAh/g for pristine PAA cells. Initial work indicated that shorter polymer chains might compromise the adhesion to the current collector, so we developed a multilayer anode (MLA) structure to mitigate this issue. Nevertheless, at this early stage of development, there was no observed increase in cycling performance for the MLA electrodes. Full article

High-performance batteries for military and extreme environment applications require alternatives to conventional liquid lithium-ion batteries (LIBs), which suffer from poor low-temperature performance and safety risks. All-solid-state lithium batteries (ASSLBs) offer enhanced safety and superior low-temperature capability. In this work, we designed and fabricated composite solid-state electrolytes using polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA) as polymer matrices, N,N-dimethylformamide (DMF) as the solvent, and lithium bis(trifluoromethane sulfonimide) (LiTFSI) as the lithium salt. Composite solutions with varying PAA mass ratios were prepared. Advanced three-dimensional (3D) printing technology enabled the rapid and precise fabrication of electrolyte membranes. An ionic conductivity of about 2.71 × 10⁻⁴ S cm⁻¹ at 25 °C, high mechanical strength, and good thermal properties can be achieved through component and 3D printing process optimization. Assembled LiCoO₂||PVDF@PAA||Li ASSLBs delivered an initial discharge capacity of 165.3 mAh/g at 0.1 mA cm⁻² (room temperature), maintaining 98% capacity retention after 300 cycles. At 0 °C, these cells provided 157.4 mAh/g initial capacity with 85% retention over 100 cycles at 0.1 mA cm⁻². This work identifies the optimal PAA ratio for enhanced electrochemical performance and demonstrates the viability of 3D printing for advanced ASSLB manufacturing. Full article

This study examined a novel ethoxy-segment-regulated hydrophobic associative amphiphilic copolymer, P(AA-AAEO_n), and systematically evaluated its solution self-assembly behavior and enhanced oil recovery (EOR) performance. The influence of ethylene oxide (EO) chain length and polymer concentration on particle size distribution and aggregation morphology was analyzed using dynamic light scattering (DLS). The results revealed a concentration-dependent transition from intramolecular to intermolecular association, accompanied by a characteristic decrease followed by an increase in hydrodynamic diameter. At a fixed AA:AAEO_n molar ratio (400:1), increasing EO segment length increased aggregate size and improved colloidal stability. Viscometric analysis showed that longer EO chains markedly increased molecular chain flexibility and solution viscosity. Interfacial tension measurements demonstrated superior interfacial activity of P(AA-AAEO_n) compared to polyacrylic acid (PAA), and longer EO chains further reduced oil–water interfacial tension. Emulsification tests verified its strong ability to emulsify crude oil. Sandpack flooding experiments and micromodel studies demonstrated effective conformance control and high displacement efficiency, achieving up to 30.65% incremental oil recovery. These findings offered essential insights for designing hydrophobic associative polymers with tunable interfacial properties for EOR applications. Full article

This study aimed to develop and characterise novel hydrogels based on natural bioactive compounds for topical antimicrobial applications. Four gel systems were formulated using different polymers, namely polyacrylic acid (Carbopol 940, CBP-G), chitosan with high and medium molecular weights (CTH-G and CTM-G), and sodium alginate (ALG-G), incorporating tinctures of Verbena officinalis and Aloysia triphylla, Laurus nobilis essential oil, and a β-cyclodextrin–clove essential oil complex. All gels displayed a homogeneous macroscopic appearance and maintained stability for over 90 days. Rheological studies demonstrated gel-like behaviour for CBP-G and ALG-G, with well-defined linear viscoelastic regions and distinct yield points, while CTM-G exhibited viscoelastic liquid-like properties. SEM imaging confirmed uniform and continuous matrices, supporting controlled active compound distribution. Thermogravimetric analysis (TG-DTA) revealed a two-step degradation profile for all gels, characterised by high thermal stability up to 230 °C and near-total decomposition by 500 °C. FTIR spectra confirmed the incorporation of bioactive compounds and products and highlighted varying interaction strengths with polymer matrices, which were stronger in CBP-G and CTH-G. Antimicrobial evaluation demonstrated that chitosan-based gels exhibited the most potent inhibitory and antibiofilm effects (MIC = 2.34 mg/mL) and a cytocompatibility assessment on HaCaT keratinocytes showed enhanced cell viability for chitosan gels and dose-dependent cytotoxicity for alginate formulations at high concentrations. Overall, chitosan-based gels displayed the most favourable combination of stability, antimicrobial activity, and biocompatibility, suggesting their potential for topical pharmaceutical use. Full article