Recovered Energy from Salinity Gradients Utilizing Various Poly(Acrylic Acid)-Based Hydrogels

Arginine as a Multifunctional Additive for High Performance S-Cathode

Advancement of sulfur (S) cathode of lithium-sulfur (Li-S) batteries is hindered by issues such as insulating nature of sulfur, sluggish redox kinetics, polysulfide dissolution and shuttling. To address these issues, we initiate a study on applying an important amino acid of protein, arginine (Arg), as a functional additive into S cathode. Based on our simulation study, the positively charged Arg facilitates strong interactions with polysulfides. The experimental results indicate that the interaction enable capability of trapping polysulfides within the S cathode, responsible for reducing shuttle effects. Furthermore, the positively charged Arg also promotes efficient ion diffusion and polysulfides conversion. The new findings include that, with addition of only 1 wt % Arg, the resultant cathode demonstrates effectively enhanced electrolyte wettability, polysulfide adsorption and redox kinetics, leading to enhanced rate performance and long-term cycling stability. This study highlights the great potential of amino acids being able to act as effective functional bio-additives in S cathode, paving a new way to high-performance and sustainable energy storage solutions.

Multi-physics numerical simulation study on thermo-sensitive gel delivery for a local post-tumor surgery treatment

Numerous studies in the literature have proposed the use of thermo-responsive hydrogels for filling cavities after tumor resection. However, optimizing the injection process is challenging due to the complex interplay of various multi-physics phenomena, such as the coupling of flow and heat transfer, multi-phase interactions, and phase-change dynamics. Therefore, gaining a fundamental understanding of these processes is crucial. In this study, we introduce a thermo-sensitive hydrogel formulated with poloxamer 407 and Gellan gum as a promising filling agent, offering an ideal phase-transition temperature along with suitable elastic and viscous modulus properties. We performed multi-physics simulations to predict the flow and temperature distributions during hydrogel injection. The results suggested that the hydrogel should be kept at 4 °C and injected within 90 s to avoid reaching the transition temperature. Cavity filling simulations indicated a symmetric distribution of the hydrogel, with minimal influence from the syringe's position. The temperature gradient at the cavity edge delays gelation during injection, which is essential to guarantee its administration as a liquid. The hydrogel's viscosity follows a sigmoidal function relative to temperature, taking five minutes to reach its maximum value. In summary, the multi-physics simulations carried out in this study confirm the potential of thermo-responsive hydrogels for use in post-tumor surgery treatment and define the conditions for a proper administration. Furthermore, the proposed model can be widely applied to other thermo-responsive hydrogels or under different conditions.

Construction of a Fluorescence/Phase-Change Dual-Mode Sensor Based on Carbon Dots/Poly(acrylic acid) for Highly Selective and Sensitive Detection of Ferric Ions

Fe3+ is one of the crucial metal ions in biological systems, and its excess or deficiency in the body can trigger various diseases, posing a serious threat to human health. Moreover, improper handling or disposal of Fe3+ can lead to water pollution, thereby harming the environment. Therefore, the development of highly selective and sensitive Fe3+ detection probes is particularly urgent. In this paper, a dual-mode sensor based on sol-gel and fluorescence signal responses was developed for the visual detection of Fe3+. The visual sensing method based on the simultaneous response of Fe3+-triggered dual signals can minimize the interference from false-positive signals and enhance detection accuracy. The dual-mode sensor, denoted as PAA@CDs, was constructed by incorporating high-brightness (high fluorescence emission intensity) green-yellow carbon dots (CDs) into poly(acrylic acid) (PAA), which possesses a large number of carboxyl functional groups. Based on the interaction of Fe3+ with the surface functional groups of CDs, nonfluorescent complexes are formed, leading to nonradiative electron transfer, which induces fluorescence quenching and produces a fluorescence signal visible to the naked eye. Additionally, the interaction of Fe3+ with the carboxyl groups of PAA triggers the cross-linking of PAA, causing a sol-gel phase change signal. Consequently, the PAA@CDs exhibit a dual-response signal in Fe3+ detection. Based on the fluorescence method, the linear detection range of PAA@CDs for Fe3+ is 0.05-2.60 mM with a limit of detection (LOD) of 5.14 μM. Meanwhile, using the sol-gel method, the linear detection range is 0.02-2.20 mM, and the LOD is 42.5 μM. Furthermore, the PAA@CDs probes can be successfully applied to the detection of Fe3+ in real water samples, demonstrating their potential value in the analysis of real samples containing multiple ions.

Rice straw derived cellulose-based hydrogels synthesis and applications as water reservoir system

This study synthesized new cellulose-based hydrogels, namely cellulose and cellulose/poly acrylic acid, using cellulose extracted from rice straw via alkaline and acidic pulping processes. The research demonstrated alkaline treatment with sodium hydroxide to be more effective for cellulose extraction compared to acidic treatment. Hydrogel synthesis used graft polymerization and chemical crosslinking with potassium persulfate as initiator and epichlorohydrin as a crosslinker. Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TG), and scanning electron microscopy (SEM) characterized the prepared hydrogels. Important factors determining hydrogel competence are swelling ratio and water retention rate. The cellulose hydrogel exhibited the highest swelling ratio in tap water (9811%) with 76.25 wt% water retention and in artificial hard water (3121.43%) with 64.58 wt% retention after 4 days outdoors at 298 K. Finally, hydrogels were investigated extensively for agricultural applications. Fenugreek seeds germinated and grew well (67% germination after 7 days) in normal soil mixed with 10% cellulose hydrogel. Biodegradability testing exhibited 6% degradation after 40 days and 10% after 120 days in an open-air lab at room temperature and 60% humidity.

Self-Healable, Adhesive, Anti-Drying, Freezing-Tolerant, and Transparent Conductive Organohydrogel as Flexible Strain Sensor, Triboelectric Nanogenerator, and Skin Barrier

Conductive hydrogels have attracted tremendous interest in the construction of flexible strain sensors and triboelectric nanogenerators (TENGs) owing to their good stretchability and adjustable properties. Nevertheless, how to simultaneously achieve high transparency, self-healing, adhesion, antibacterial, anti-freezing, anti-drying, and biocompatibility properties through a simple method remains a challenge. Herein, a transparent, freezing-tolerant, and multifunctional organohydrogel (PAOAM-PDO) as electrode for strain sensors and TENGs was constructed through a free radical polymerization in the 1,3-propanediol (PDO)/water binary solvent system, in which oxide sodium alginate, aminated gelatin, acrylic acid, and AlCl3 were used as raw materials. The obtained PAOAM-PDO exhibited good transparency (>90%), self-healing, adhesiveness, antibacterial property, good conductivity (1.13 S/m), and long-term environmental stability. The introduction of PDO endowed PAOAM-PDO with freezing resistance with a low freezing point of -60 °C, and PAOAM-PDO could serve as a protective skin barrier to prevent frostbite at low temperature. PAOAM-PDO could be assembled as strain sensors to monitor heterogeneous human movements with high strain sensitivity (gauge factor of 7.05, strain = 233%). Meanwhile, PAOAM-PDO could be further fabricated as a TENG with a "sandwich" structure in single electrode mode. Moreover, the resulting TENG achieved electrical outputs with simple hand tapping and served as a self-powered device to light light-emitting diodes. This work displays a feasible strategy to build environment-tolerant and multifunctional organohydrogels, which possess potential applications in the wearable electronics and self-powered devices.

Tandem Osmotic Engine Based on Hydrogel Particles with Antipolyelectrolyte and Polyelectrolyte Effect Fuelled by Both Salinity Gradient Modes

In this study, we propose a new approach to attain energy by salinity gradient engines with pistons based on hydrogels possessing polyelectrolyte and antipolyelectrolyte effects in a tandem arrangement, providing energy in each salinity gradient mode in a repeatable manner. The swelling of hydrogel with a polyelectrolyte effect and shrinking of hydrogel particles possessing an antipolyelectrolyte effect in desalinated water, and subsequent shrinking of hydrogel with polyelectrolyte and swelling of hydrogel antipolyelectrolyte effect in saline water, generate power in both increasing and decreasing salinity modes. To investigate the energy recovery, we scrutinized osmotic engine assemblies by a setup arrangement of pistons with hydrogel particles, with polyelectrolyte and antipolyelectrolyte effects, in tandem. The energy recovery from the tandem engine setup (calculated based on dry form for each polyelectrolyte polyacrylate-based hydrogel-SPA) and antipolyelectrolyte–sulfobetaine-based gel with methacrylate polymeric backbone-SBE) up to 581 J kg⁻¹ and a mean power of 0.16 W kg⁻¹ was obtained by the tandem setup of SPA and SBE hydrogel containing 3% crosslinking density and particle size of 500 microns with an external load of 3.0 kPa. Exchange of sulfobetaine with methacrylamide (SBAm), the main polymer backbone, revealed a positive increase in energy recovery of 670 J kg⁻¹ with a mean power of 0.19 W kg⁻¹ for the tandem system operating under the same parameters (SPA@SBAm). The energy recovery can be controlled, modulated and tuned by selecting both hydrogels with antipolyelectrolyte and polyelectrolyte effects and their performing parameters. This proof of concept provides blue energy harvesting by contributing both polyelectrolyte and antipolyelectrolyte effects in a single tandem setup; together with easy accessibility (diaper-based materials (SPA)) and known antibiofouling, these properties offer a robust alternative for energy harvesting.