Poor Thermal Stability Research Articles

Counteracting thermal degradation of LiPF6-based electrolyte with additives or lithium salts: A gas analysis revealing the impact of NMC

One of the weaknesses of the LiPF6-based electrolyte is its poor thermal stability. It can result in an accelerated battery capacity fading and CO2 gas generation due to the formation of PF5 which are highly reactive towards the electrolyte solvents. As the formation of PF5 is inevitable, efforts are dedicated to inhibiting its deleterious impact by adding a Lewis base to form a complex. However, no study investigates the PF5-complexation efficiency through gas analysis. Here, gas analysis shows that N-containing additives are effective in reducing gas generation upon electrolyte storage at 55 °C. Out of our expectations, the trend is reversed when it comes to thermal storage of NMC-graphite batteries, involving competitive chemisorption processes on the NMC acid and basic sites. It turned out that, NMC surface can be more effective than additives in mitigating the thermal degradation of the electrolyte. Furthermore, the gas level thermally generated does not decrease while replacing the culprit LiPF6 salt by mixtures of LiFSI + LiPF6 or LiFSI + LiODFB. Especially in presence of LiODFB, water triggers hydrolysis reactions that also lead to gas evolution.

Broadband NIR phosphor Gd3Lu2Ga3O12: Cr3+, Yb3+ with high thermal stability

Broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) have become important as new NIR light sources in NIR spectroscopy and NIR imaging techniques. However, currently developed broadband NIR phosphors commonly suffer from weak emission and poor thermal stability. In this work, a series of Gd3Lu2Ga3O12: Cr3+ phosphors were synthesized via high-temperature solid-state reaction. Under 460 nm excitation, the phosphors exhibit an intense emission spanning from 650 to 1150 nm with a full width at half maximum (FWHM) of 122 nm. After introducing Yb3+ as a co-dopant, the emission of the phosphor has been broadened greatly. Interestingly, the studied phosphors demonstrate super high thermal stability in a wide temperature range of 35–560 K, with the integrated emission intensity fluctuating within 10 %. At 435 K, the emission intensity of Gd3Lu2Ga3O12: 0.03Cr3+ remains 99.5 % and Gd3Lu2Ga3O12: 0.03Cr3+, 0.01 Yb3+ keeps 102.7 % of the initial intensity at room temperature. These NIR phosphors have been encapsulated with a common commercial 460 nm blue LED chip to fabricate a pc-LED device. The NIR output power of the device reaches 23.93 mW@100 mA, with a photoelectric conversion efficiency of 9.81 % at 20 mA current. The applications of the prepared NIR light source in night vision, and bioimaging have been demonstrated. The results show that these Cr3+/Yb3+ doped garnet phosphors can be effectively used in NIR light sources.

Narrow polydispersity P(AN-MA) copolymers synthesized in continuous flow as potential carbon fiber precursors

In this work, poly (acrylonitrile-methyl acrylate) [P(AN-MA)] copolymers with controllable molecular weights and narrow polydispersity were successfully synthesized in continuous flow without pre-deoxygenation. A dual-reactor method was designed to prepared P(AN-MA) with higher molecular weight and achieve a high yield from 62.57 % to 70.16 %. To facilitate industrial production of P(AN-MA), pre-mixing stage was added in continuous flow for replacing the ultrasonic mixing process. The characteristic mixing time is 27.80 min and the length of Polyfluoroalkoxy (PFA) tube exceeds 74.625 m for thoroughly mixing. Higher molecular weight P(AN-MA) copolymers possess poorer preoxidation properties such as higher initiation temperature, more concentrated heat release and larger activation energy of cyclization reaction as well as lower extent of stabilization and poorer thermal stability against high-temperature treatment. Moreover, 192 g P(AN-MA) was continuously prepared by the dual-reactor method for 105 min without suffering from notable pressure increase.

Significantly improving the thermal stability of alginate lyase AlyC3 from Psychromonas sp. C-3 by computational redesign

Alginate lyase is a key enzyme in the bioproduction of alginate oligosaccharides. The alginate lyase AlyC3, derived from Psychromonas sp. C-3, can hydrolyze homopolymerized mannuronic acid into oligosaccharides (primarily composed of mannuronate trimer), which possess physiological properties such as bacteriostatic and antioxidant activities and show a better application prospect. However, the poor thermal stability hinders its potential application in industrial production. In this study, AlyC3 mutants A35P, L95F, N138Y and M162I were obtained through the protein repair one-stop shop (PROSS) design combined with protein data bank in Europe (proteins, interfaces, structures and assemblies) (PDBePISA) analysis of the dimer interface. The results demonstrated that the thermodynamic and kinetic stability of these single-point mutants were significantly improved compared to the wild-type (WT), with the melting temperature increased by 4.33, 9.35, 9.74 and 11.24 °C, respectively, while the half-life (t1/2) was 1.66, 1.02, 1.02 and 1.53 times higher than that of WT, respectively. Based on this, the beneficial mutations were further combined to obtain a combinatorial mutant, A35P-L95F–N138Y-M162I, which exhibited the superior thermal stability. Notably, the combinatorial mutant's melting and optimal temperature increased by 17.05 and 10 °C, respectively; moreover, the mutant enzyme's t1/2 and enzyme activity were 8.21 times and 123.93% higher than those of the WT, respectively. Structural analyses indicated that increased hydrophobic interactions and polar bonding between the mutated and nearby residues, with improved rigidity in the flexible loop, might account for the significantly improved thermal stability of the reengineered AlyC3, which makes it a robust candidate for alginate oligosaccharide production.

The two-step strategy for enhancing the specific activity and thermostability of alginate lyase AlyG2 with mechanism for improved thermostability

To overcome the trade-off challenge encountered in the engineering of alginate lyase AlyG2 from Seonamhaeicola algicola Gy8T and to expand its potential industrial applications, we devised a two-step strategy encompassing activity enhancement followed by thermal stability engineering. To enhance the specific activity of efficient AlyG2, we strategically substituted residues with bulky steric hindrance proximal to the active pocket with glycine or alanine. This led to the generation of three promising positive mutants, with particular emphasis on the T91S mutant, exhibiting a 1.91-fold specific activity compared to the wild type. To mitigate the poor thermal stability of T91S, mutants with negative ΔΔG values in the thermal flexibility region were screened out. Notably, the S72Ya mutant not only displayed 17.96 % further increase in specific activity but also exhibited improved stability compared to T91S, manifesting as a remarkable 30.97 % increase in relative activity following a 1-hour incubation at 42 °C. Furthermore, enhanced kinetic stability was observed. To gain deeper insights into the mechanism underlying the enhanced thermostability of the S72Ya mutant, we conducted molecular dynamics simulations, principal component analysis (PCA), dynamic cross-correlation map (DCCM), and free energy landscape (FEL) analysis. The results unveiled a reduction in the flexibility of the surface loop, a stronger correlation dynamic and a narrower motion subspace in S72Ya system, along with the formation of more stable hydrogen bonds. Collectively, our findings suggest amino acids substitutions resulting in smaller side chains proximate to the active site can positively impact enzyme activity, while reducing the flexibility of surface loops emerges as a pivotal factor in conferring thermal stability. These insights offer valuable guidance and a framework for the engineering of other enzyme types.

Theoretical study of double antiaromatic structure - cyclo[16]carbon

Cyclo[16]carbon is the first antiaromatic all-carbon ring discovered in recent experiments. We studied its thermal stability and found that cyclo[16]carbon showed poor thermal stability. Subsequently, we studied its bonding properties, electron delocalization and antiaromaticity by quantum chemical calculation and wave function analysis. We observe that cyclo[16]carbon is a doubly antiaromatic system with alternating long and short bonds, where the shorter C-C bond has stronger π interactions and delocalization. In addition, by studying electron spectra and nonlinear optics, we elucidating the contribution of in-plane and out-of-plane π (πin and πout) orbitals to electron excitation, and confirming the nonlinear anisotropy of cyclo[16]carbon. Electrostatic potential (ESP) and local mean ionization energy (ALIE) analyses demonstrate the electrophilic properties of the short C-C bond. Our comprehensive characterization of cyclo[16]carbon will enable researchers to deepen their understanding of cyclo[16]carbon and thus derive its more valuable structure.

Understanding the microstructure evolution of carbon-doped Sb2Te3 phase change material for high thermal stability memory application

The Sb2Te3 phase change material shows a growth-dominated crystallization mechanism with fast phase transition but poor thermal stability of the amorphous state. This work investigated the effects of carbon doping on the thermal stability, microstructure, and electrical properties of the Sb2Te3 material. The 10-year data retention temperature of the material increased to ∼147.3 °C and the size of the grains was limited to ∼10 nm by carbon doping. The formation of the C cluster upon crystallization was found at the grain boundaries, which was accelerated as the temperature increased due to the break of the Sb–C bonds. The memory device based on the carbon-doped Sb2Te3 material exhibited a switching speed of 15 ns and an endurance of ∼105 cycles with a resistance ratio of more than two orders of magnitude. This work suggests that the carbon-doped Sb2Te3 material is a promising candidate for memory applications that require high thermal stability, fast speed, and high endurance.

Emulsification properties of ovalbumin-fucoidan (OVA-FUC) binary complexes

The poor thermal stability and emulsifying properties of ovalbumin (OVA) limit its functional performance, but these limitations may be overcome by forming binary complexes. We prepared binary complexes of OVA and fucoidan (FUC) through electrostatic self-assembly and investigated the emulsifying properties of the complex by measuring the particle size, interfacial membrane thickness, zeta potential, and stability of the emulsion prepared with camellia oil and the complex. The OVA-FUC emulsions have a thicker interfacial membrane, lower mobility, higher viscosity, and better stability compared with the OVA emulsions. The emulsion prepared with 1.5 % OVA-FUC remained stable and homogeneous during storage. They tended to become unstable with freeze–thaw, but the oil encapsulated did not leak after coalescence occurred. With the addition of Ca2+, the OVA-FUC emulsion will be converted into a gel state. These findings indicate that OVA-FUC binary complexes can be used to prepare high-performance emulsions with great potential for development.

Cross-scale deciphering thermal failure process of Ni-rich layered cathode

Ni-rich LiNixCoyMn1-x-yO2 (NCM) layered oxides are low-cost high-energy density cathode materials, but plagued by its poor thermal stability incurred safety concerns. The thermal failure process of the layered cathode is accompanied by heat generation and oxygen release, which drives the battery into thermal runaway (TR). Aiming to fully understand the TR process and the structure evolution, this work applies diverse characterization techniques onto a polycrystalline Ni-rich layered cathode (LiNi0.83Mn0.05Co0.12O2 (PCN83)) to comprehensively investigate its thermal failure process at multiple scales. From macro level, we validate that it is the cathode thermal failure that drives the battery from the heat accumulation stage into TR in adiabatic conditions. From micro level, transmission electron microscopy (TEM) verifies that the thermal failure of PCN83 starts from 150 °C, which is much lower than the TR temperature measured from macro level tests. We reveal that the PCN83 cathode experiences sequential phase transitions before the TR, where the phase transition mechanism is illustrated from the atomic scale and the pore evolution process is unraveled. In situ heating TEM further reveals that thermal failure is preferentially initiated from grain boundaries and defect regions. These findings provide an in-depth understanding of the whole thermal failure process of NMC-based layered cathode materials and sheds new lights on the rational design of Ni-rich cathode materials with improved thermal safety.

Synergistic enhancement of coercivity and thermal stability of nanocrystalline multi-main-phase Nd-Ce-Fe-B magnet via Gd60Y10Cu15Al15 addition

Nanocrystalline multi-main-phase (MMP) Nd-Ce-Fe-B magnet can effectively suppress the magnetic dilution effect of Ce. However, its low coercivity and poor thermal stability have not been adequately overcome. In this work, a novel low-melting-point Gd60Y10Cu15Al15 alloy was introduced into MMP Nd-Ce-Fe-B magnet through intergranular addition for simultaneously enhancing its coercivity and thermal stability. The results show that the intrinsic coercivity Hcj is obviously improved, and its maximum increment is ∼12.3 % at 4 wt% Gd60Y10Cu15Al15 alloy. Especially, the increase in Hcj is more significant, and an abnormally increase in the maximum energy product (BH)max occurs at high temperature of 150 °C. Meanwhile, the reversible temperature coefficients of Hcj (β) and Br (α) are improved simultaneously. These findings imply the enhanced thermal stability for the MMP magnet with Gd60Y10Cu15Al15 addition. The microstructural characterizations, compositional analyses and micromagnetic simulations reveal that the competitive effects of the formed non-ferromagnetic grain boundary (GB) phase and Y or Gd diffusion into the main phase lead mainly to a synergistic improvement in the coercivity and thermal stability of the magnet. This work is expected to provide a promising cost-effective approach for developing the high-performance thermally-stable Nd-Ce-Fe-B magnet and explore more possibilities for effective utilization of Y or Gd rare-earth resources.

Enhancing antithermal-quenching properties of terbium-doped phosphors through Nb/Ta substitution: Insights into the role of intervalence charge transfer and excitation-driven modulation

Currently, the unique 5D4 energy level of terbium (Tb3+) can contribute to narrow-band green light emission, which has high application prospects. However, due to its poor thermal stability at high temperatures, how to enhance the antithermal-quenching properties of Tb-doped phosphors has become a research difficulty in the field of solid-state lighting and temperature sensing. In this contribution, the antithermal-quenching green-emitting of terbium was achieved by Nb/Ta substitution to form GdNb1-xTaxO4:Tb3+ phosphors with various components. Photoluminescence analyses reveal an increasing trend in both the optical band gap and the intervalence charge transfer (IVCT) energy level positions with substitution. Variable-temperature spectrums observed that the phosphors under different compositions presented a large discrepancy in thermal quenching performance. It is elucidated that the elevated position of the IVCT energy level (IVCT-EL) predominantly influences thermal quenching, bolstering its role as a compensatory luminescence channel of 5D3→5D4 far more than functioning as a quenching luminescence channel for Tb3+5D3/5D4. Delving into the perspective of IVCT-EL positioning unveils the intrinsic mechanism through which IVCT-EL positions modulate the thermal quenching properties of phosphors with varying compositions due to the substitution of Ta for Nb. This insight facilitates the realization of enhanced thermal quenching resistance in phosphors. Furthermore, the antithermal-quenching property of Tb3+ in single-phase phosphors can be effectively modulated by excitation at different wavelengths. This tuning scheme not only advances the exploration of terbium-doped antithermal-quenching phosphors but also provides a novel strategy and reference for designing green-emitting phosphors in the fields of lighting and sensing.

Recent Progress in the Composites of Perovskite Nanocrystals and II-VI Quantum Dots: Their Synthesis, Applications, and Prospects

Abstract: The remarkable photoelectric characteristics of perovskite nanocrystals (NCs), including high fault tolerance, tunable photoluminescence (PL) emission, and high carrier mobility, contribute to making them especially attractive for photonic and optoelectronic applications. Unfortunately, the poor environmental thermal and light stability set obstacles to their industrial applications. Over the past 40 years, II-VI semiconductor quantum dots (QDs) have achieved many important photophysics findings and optoelectronic applications. Compared with perovskite NCs, II-VI semiconductor QDs still have a relatively weaker molar absorbance coefficient. Whereas, significant enhancement of both the stability and the optical performance of the composites of perovskite NCs and II-VI QDs are of interest for photovoltaic and optoelectronic devices. The composites of perovskite NCs and II-VI QDs come in two primary types: core/shell structures and heterojunction structures. To better understand the composites of perovskite NCs and II-VI QDs, the approaches of synthesis methods, their optoelectronic properties, carrier dynamics and potential applications in solar cells, light emitting diodes (LEDs) and photodetectors are summarized. Furthermore, the unmet problems and the potential applications are also presented.

Outstanding shape memory effect and thermal stability of Cu–Al–Ni-based high temperature shape memory alloys achieved by Gd and Mn doping

In this paper, the effects of Mn element and rare earth element Gd on the microstructure, thermal stability, mechanical properties and shape memory effect of polycrystalline Cu-12.0Al-4.0Ni and Cu-12.0Al-4.0Ni-1.5Mn-xGd high-temperature shape memory alloy were investigated. The results show that the Cu-12.0Al-4.0Ni alloy exhibits millimeter-sized grain, dual-phase structure with coexistence of 18R and 2H martensite and poor thermal stability. When the Mn and Gd element was added to Cu-12.0Al-4.0Ni alloys, the grain size can be refined by an order of magnitude, and the 2H martensite disappeared completely, accompanied by the formation of the AlCu4Gd phase, meanwhile, thermal stability is significantly improved. The grain refinement improves the mechanical properties and shape memory effect of Cu-12.0Al-4.0Ni-1.5Mn-xGd alloys. When x = 0.3, the compressive fracture stress, compressive fracture strain and recoverable strain can reach 969 MPa, 15 % and 8 %, respectively.

Thermally Robust Solvent-Free Liquid Polyplexes for Heat-Shock Protection and Long-Term Room Temperature Storage of Therapeutic Nucleic Acids.

Nucleic acid therapeutics have attracted recent attention as promising preventative solutions for a broad range of diseases. Nonviral delivery vectors, such as cationic polymers, improve the cellular uptake of nucleic acids without suffering the drawbacks of viral delivery vectors. However, these delivery systems are faced with a major challenge for worldwide deployment, as their poor thermal stability elicits the need for cold chain transportation. Here, we demonstrate a biomaterial strategy to drastically improve the thermal stability of DNA polyplexes. Importantly, we demonstrate long-term room temperature storage with a transfection efficiency maintained for at least 9 months. Additionally, extreme heat shock studies show retained luciferase expression after heat treatment at 70 °C. We therefore provide a proof of concept for a platform biotechnology that could provide long-term room temperature storage for temperature-sensitive nucleic acid therapeutics, eliminating the need for the cold chain, which in turn would reduce the cost of distributing life-saving therapeutics worldwide.

Particle Size Modification of Breadfruit Starch (Artocarpus altilis) into Nanoparticle Size Through Top Down Technique using Acid Hydrolysis

<br /><span style="font-size: 9.0pt; line-height: 150%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: AR-SA; mso-bidi-language: AR-SA; mso-bidi-font-style: italic;" lang="EN-US">Breadfruit (<em>Artocarpus altilis</em>) is a significant starch source, comprising up to 70.25% of its composition, and holds extensive industrial applications. However, the physicochemical properties of natural starch pose several challenges to its direct use as an industrial raw material. These challenges include high viscosity, substantial swelling power, low solubility, significant retrogradation, limited digestibility, and poor thermal stability. To address these issues, modification of the starch particle size to the nanometer scale is proposed, which is anticipated to enhance both functional and physicochemical properties. This study employs a top-down approach through 2.2 N HCl acid hydrolysis at 38°C for 24 hours. This method offers simplicity, efficiency for scale-up in industrial applications, and relatively higher stability than alternative approaches. Particle size analysis using Particle Size Analysis (PSA) revealed an average particle size of 215 nm. Fourier Transform Infrared (FT-IR) spectroscopy showed characteristic bands similar to natural starch, with slight variations in peak intensity, indicating successful acid hydrolysis and structural disruption of the molecular order. Morphological analysis revealed minimal changes in the granules' surface structure, with clumping observed due to acid hydrolysis. The resultant starch nanoparticles exhibited decreased viscosity and swelling while solubility was enhanced. Therefore, nanoparticle starch holds promising applications in food and non-food industries</span><span style="font-size: 9.0pt; line-height: 150%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-ID; mso-fareast-language: AR-SA; mso-bidi-language: AR-SA; mso-bidi-font-style: italic;">.</span>

Dual-functional Separators Regulating Ion Transport Enabled by 3D-Reinforced Polyimide Microspheres Protective Layer for Dendrite-Free and High-Temperature Lithium Metal Batteries.

High-energy-density lithium metal batteries (LMBs) are confronted with crucial concerns of security and a short cycle lifespan caused by the uncontrollable formation of lithium (Li) dendrites. The poor thermal stability and heterogeneous Li deposition of conventional polyolefin separators often cause battery short circuiting and thermal runaway in LMBs. Herein, a novel dual-functional PE composite separator (PI-COOH/PE) coated by carboxyl polyimide (PI) microspheres is fabricated by an etching-acidification method. The three-dimensional (3D) high-temp PI microsphere with rich carboxyl groups on the surface improve the security of LMBs at extremely high temperatures and facilitate the formation of a stable and uniform SEI layer, which contributes to accelerating the Li+ transport and stabilizing the formation of the SEI layer. Consequently, the Li symmetric cell assembled with the (PI-COOH)/PE separator exhibits stable overpotential over 3000 h, and the corresponding Li//NCM811 full cells also show a high-level discharge capacity of 146.6 mAh g-1 at 5 C. Meanwhile, it also demonstrates outstanding cycling stability and thermal safety, which can survive continuously over 160 min at 140 °C (vs 21 min for PE). The above results indicate the (PI-COOH)/PE separator constructed by a low-cost and industrial-friendly strategy simultaneously addresses high-temperature stability and dendrite resistance.

Strategic moderation of thermal stability and curing time of lignin-based phenolic resin by incorporating nanoparticles

In order to solve the problem of poor thermal stability of lignin-based phenolic resin (LPF), nanoparticles such as nano-SiO2, nano-Al2O3 and nano-TiO2 were used as modifiers to modify LPF. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) results showed that nano-SiO2, nano-Al2O3 and nano-TiO2 can be chemically cross-linked with LPF to form Si-O-Si, Al-O and Ti-O, respectively. Scanning electronic microscopy (SEM) results showed that after modifying by nano-SiO2 (SLPF), nano-Al2O3 (ALPF) and nano-TiO2 (TLPF), the small copolymers were significantly reduced and the surface become flat and smooth. Thermogravimetric analysis (TGA) showed that at 800 °C, the thermal stability of SLPF, ALPF and TLPF increased by 4.28, 5.38 and 4.74%, respectively, compared with LPF, the reason was that the introduction of nanoparticles required more energy to be absorbed during thermal degradation. Differential scanning calorimetry (DSC) results showed that the curing temperature of the modified LPF remained basically unchanged, and the curing time was reduced.

Sustained release, antimicrobial, and antioxidant properties of modified porous starch-based biodegradable polylactic acid/polybutylene adipate-co-terephthalate/thermoplastic starch active packaging film

Porous starch (PS) is a modified starch with commendable biodegradable and adsorption properties. PS exhibits poor thermal stability, and the aqueous solution casting method is conventionally used for PS-activated packaging films. This approach limits the large-scale production of films and makes it difficult to play the functions of porous pores. In this study, PS was prepared by enzymatic digestion combined with freeze-drying and adsorbed with clove essential oil (CEO) after cross-linking with sodium trimetaphosphate. Subsequently, a novel PLA/PBAT/TPS/ScPS-CEO sustained release active packaging film was prepared by blending PLA, PBAT, TPS, and ScPS-CEO using industrial melt extrusion. Compared with PS, ScPS effectively slowed down the release of CEO from the film, with the maximum release of active substances at equilibrium increasing by approximately 100 %, which significantly enhanced the persistence of the antimicrobial and antioxidant properties. The polylactic acid/poly (butylene adipate-co-terephthalate)/thermoplastic starch/trimetaphosphate-crosslinked porous starch incorporated with clove essential oil (PLA/PBAT/TPS/ScPS-CEO) film could reduce the proteolysis, lipid oxidation and microbial growth of salmon, extending its shelf life by approximately 100 % at 4 °C. These results indicate that the ScPS can be used in fresh packaging material in practical applications.

Thermal stability optimization of single-leg skutterudite-based thermoelectric devices based on lattice distortion effects

Skutterudite-based (SKD-based) thermoelectric materials are well-known for their high figure-of-merit (zT value) in the intermediate temperature region. Based on the urgent need for long-term high-temperature service, the poor interfacial thermal stability when connected with the Cu electrodes has greatly limited its industrial application. In this work, we propose a novel alloying route for the barrier layers for p-type SKDs. A Fe80Cr17.5Mo2.50/p-SKD junction with matched coefficients of thermal expansion (CTE), high mechanical reliability, and low contact resistivity is obtained. The addition of large-scale Mo causes severe lattice distortion in the barrier alloy, which contributes to the sluggish elemental diffusion. Thus, after aging at 823 K for 600 h, the Fe80Cr17.5Mo2.5 junction has a thinner reaction layer (∼25 μm), lower contact resistivity (∼3.8 μΩ·cm2), and higher shear strength (∼14 MPa), compared with the Mo-free (Fe80Cr20) barrier junction. Our finding opens a new insight for fabricating long-term high thermally stable SKD-based thermoelectric devices with desirable mechanical stability.

UV−Curable choline chloride and bromophenol red covalent functionalized chitosan antibacterial and pH−sensitive hydrogels

Food safety and food freshness issues have become important concerns for consumers and hydrogels with high antibacterial efficiency, low toxicity and pH−sensitive colorimetric intelligence are one of candidates to meet the requirement of food package and food spoilage monitoring. Nevertheless, hydrogels prepared only by assembling the ingredients with non−covalent interactions through time−consuming molding process usually encounter drawbacks such as relatively poor mechanical properties, stability and thermal stability, which always restrict their further applications. To overwhelm these shortcomings, UV−curable choline chloride (ChCl) and bromophenol red (BR) covalent functionalized antibacterial and pH−sensitive cross−linked hydrogels (UV−hydrogels) were developed in this paper. The UV−hydrogels possessed good thermal stability because the initiated thermal decomposition temperature (Td5) is in the range of 135.8–184.7 °C. The DMA analysis revealed that the UV−hydrogels are with good mechanical properties because the elongation at break is in the range of 117–525% and the tensile strength is in the range of 0.8–2.7 MPa. The UV−hydrogels with BR groups exhibited naked eye visible color variation from yellow to dark blue-green with the variation of the pH values from 2 to 14. The antibacterial efficiency of the UV−hydrogels against S. aureus, E. coli and M. albican increased with the increment of covalent−grafted ChCl amount. Cytotoxicity assay demonstrated that the UV−hydrogels are low toxicity against L929 cells. The experiment of monitoring freshness of beef denoted the UV−hydrogels have potential application in animal–derived high protein food packaging and freshness monitoring.