Search Results (45)

Photothermal superhydrophobic surfaces represent a promising solution for passive anti-icing; however, the persistent high solar absorption of static black coatings often leads to undesirable overheating under non-icing conditions. To address this limitation, we developed a smart superhydrophobic polydimethylsiloxane (PDMS) surface embedded with thermochromic capsules (TC) (S-PDMS/TC) featuring reversible thermochromic capability via a facile combination of spin-coating and femtosecond laser ablation. The resulting hierarchical micro-grid structure acts as a sacrificial layer, shielding fragile nanostructures against mechanical abrasion, while endowing the surface with robust superhydrophobicity (contact angle > 155°). Uniquely, S-PDMS/TC exhibits an adaptive color transition from pale yellow to deep black when the temperature drops below 5 °C. This response enables on-demand photothermal enhancement, significantly boosting solar absorption in freezing environments while minimizing heat absorption at room temperature. Consequently, S-PDMS/TC demonstrates superior anti-icing performance, extending the freezing time to 310 s and reducing ice adhesion strength to 40.4 kPa. Notably, during photothermal de-icing, the meltwater exhibits spontaneous dewetting behavior driven by the replenishment of the air cushion, effectively preventing secondary icing. This work presents a mechanically durable and intelligent strategy for ice protection, successfully balancing efficient de-icing with thermal management. Full article

Hollow hydrogels are promising for flexible electronics and bioengineering, yet their fabrication is limited by sacrificial templates, specialized equipment, and complex engineering processes. Herein, a facile wet-spinning strategy is developed to fabricate sodium alginate (SA) hollow hydrogels. Extruding SA/CaCO₃ precursor suspension into an acidic coagulation bath induces simultaneous ionic cross-linking and in situ CO₂ generation, driving the self-formation of hollow tubular architectures with tunable morphologies, mechanical performance, macroscopic architecture, and functional properties. Moreover, the introduction of secondary cross-linking enhances the SA hydrogels’ water retention and resistance to freezing conditions. Utilizing their intrinsic ionic conductivity, the hollow hydrogels demonstrate outstanding sensing performance, enabling reliable detection of both large-amplitude limb motions and subtle muscle activity in the human body. Furthermore, hollow hydrogel tubes with diverse geometries can be readily fabricated by simply modifying the spinning mold, thereby broadening their potential applications. In vitro cytotoxicity assessments further confirm that the SA hollow hydrogels exhibit excellent biocompatibility with minimal cytotoxicity, satisfying the fundamental criteria for bioengineering applications. The combination of a simple yet controllable fabrication strategy with the intrinsic multifunctionality of the SA hollow tubes confers substantial potential for their deployment in bioengineering and flexible electronic applications. Full article

Proteins that span cellular membranes represent around 30% of the proteome and over 50% of drug targets. A variety of synthetic and naturally-occurring small organic molecules interact with membrane proteins and up- and down-regulate protein function. The atomic details of these regulatory molecules offer important information about protein function and aid the discovery, refinement and optimization of new drugs. X-ray crystallography and cryo-electron microscopy (cryo-EM) are not always able to resolve the structures of small molecules in their physiological sites on membrane proteins, particularly if the molecules are unstable or are reactive enzyme substrates. Solid-state nuclear magnetic resonance (SSNMR) is a valuable technique for filling in missing details on the conformations, dynamics and binding environments of small molecules regulators of membrane proteins. SSNMR does not require diffracting crystals possessing long-range order and can be performed on proteins within their native membranes and with freeze-trapping to maintain sample stability. Here, work over the last two decades is described, in which SSNMR methods have been developed to report on interactions of the ATP substrate with the Na,K-ATPase (NKA), an ion-transporting enzyme that maintains cellular potential in all animals. It is shown how a combination of SSNMR measurements on membranous NKA preparations in the frozen and fluid states have provided unique information about the molecular conformation and local environment of ATP in the high-affinity nucleotide site. A combination of chemical shift analysis using density functional theory (DFT) calculations, dipolar coupling measurements using REDOR and measurements of the rates of proton spin diffusion is appraised collectively. The work described herein highlights the methods developed and challenges encountered, which have led to a detailed and unrivalled picture of ATP in its high-affinity binding site. Full article

Current hydrogels used for cartilage tissue engineering often lack the mechanical strength and structural integrity required to mimic native human cartilage. This study addresses this limitation by developing reinforced hydrogels based on a ternary polymer blend of poly(vinyl) alcohol (PVA), gelatin (GL), and chitosan (CH), with gentamicin sulfate (GS) as an antimicrobial agent and a crosslinker. The hydrogels were produced using two crosslinking methods, the freeze/thaw and heated cycles, and reinforced with forcespun polycaprolactone (PCL) nanofiber to improve mechanical performance. Chemical characterization revealed that GS forms weak hydrogen bonds with the ternary polymers, leading to esterification with PVA, and covalent bonds are formed as the result of the free amino group (-NH₂) of chitosan that reacts with the carboxylic acid group (-COOH) of gelatin. SEM images help us to see how the hydrogels are reinforced with polycaprolactone (PCL) fibers produced via force spinning technology, while mechanical properties were evaluated via uniaxial tensile and compressive tests. Water retention measurements were performed to examine the crosslinking process’s influence on the hydrogel’s water retention, while the hydrogel surface roughness was obtained via confocal microscopy images. A constitutive model based on non-Gaussian strain energy density was introduced to predict experimental mechanical behavior data of the hydrogel, considering a non-monotonous softening function. Loading and unloading tests demonstrated that GS enhanced crosslinking without compromising water retention or biocompatibility because of the reaction between the free amino group of CH and the carboxylic group of gelatin. The PCL-reinforced PVA/GL/CH hydrogel shows strong potential for cartilage repair and tissue engineering applications. Full article

To investigate the halogen substitution effect on the anionic spin crossover (SCO) complexes, azobisphenolate ligands with 5,5′-dihalogen substituents from fluorine to iodine were synthesized, and their anionic Fe^III complexes 1F, 1Cl, 1Br, and 1I were isolated. The temperature dependence of magnetic susceptibility and crystal structure revealed that 1F, 1Cl, and 1Br are all isostructural and exhibit SCO with the rotational motion of the cation and ligands, whereas 1I shows incomplete SCO. Note that 1Cl and 1Br showed irreversible and reversible cooperative SCO transitions, respectively. Short intermolecular contacts between the Fe^III complex anions were found despite Coulomb repulsions for all the complexes. The topological analysis of the electron density distributions revealed the existence of X···X halogen bonds, C–H···X, C–H···N, and C–H···O hydrogen bonds, and C–H···π interactions are evident. The dimensionality of intermolecular interactions is suggested to be responsible for the cooperative SCO transitions in 1Cl and 1Br, whereas the disorder due to the freezing of ligand rotations in 1Cl is revealed to inhibit the SCO cooperativity. Full article

Co₇Zn₇Mn₆ is a $\beta$-Mn-type alloy belonging to the Co_xZn_yMn_z ($x+y+z=20$) family that notoriously features a skyrmionic magnetic phase below the ferromagnetic ordering temperature and, in addition, a reentrant spin glass transition at low temperatures. In this work, we have studied the effect of partial substitution of Mn by Fe in the magnetic properties of this alloy. Samples of Co₇Zn₇Mn_6−xFe_x, $0\le x\le 1$, were synthesised using the Bridgman–Stockbarger method, and their structure and composition were fully characterised by XRD and EDS. VSM and AC susceptibility measurements show that the partial substitution of Mn by Fe increases $T_{\mathrm{C}}$ and the skyrmionic region of the magnetic phase diagram is suppressed for $x>0.5$. The AC susceptibility behaviour at low temperatures can be ascribed to the presence of a reentrant spin glass state observed for all compositions, with a spin glass freezing temperature, $T_{\mathrm{g}}$, that shifts to lower temperatures as the Fe content increases. Full article

We used magnetic and synchrotron X-ray diffraction measurements to investigate the possibility of tuning the strength of magnetic interparticle interactions in nanoparticle ensembles via chemical manipulation. Our main result comes from temperature-resolved in-phase ac-susceptibility data collected on 8 nm average-diameter Ni_0.25Zn_0.75Fe₂O₄ (Ni25) and Ni_0.5Zn_0.5Fe₂O₄ (Ni50) nanoparticles at different frequencies, χ′ vs. T|_f. We found that the relative peak temperature variation per frequency decade, $\mathsf{\varphi }=\frac{∆\mathrm{T}}{\mathrm{T}·∆\mathrm{l}\mathrm{o}\mathrm{g}\left(\mathrm{f}\right)}$—a known measure of interparticle interaction strength—exhibits a four-fold increase, from ϕ = 0.04 in Ni50 to ϕ = 0.16 in Ni25. This corresponds to a fundamental change in the nanoparticles’ superspin dynamics, as proven by the fit of phenomenological models to magnetic relaxation data. Indeed, the Ni25 ensemble exhibits superparamagnetic behavior, where the temperature dependence of the superspin relaxation time, τ, is described in the Dorman–Bessais–Fiorani (DBF) model: $\tau \left(\mathrm{T}\right)={\tau }_{\mathrm{r}}\exp \left(\frac{{\mathrm{E}}_{\mathrm{B}}+{\mathrm{E}}_{\mathrm{a}\mathrm{d}}}{{\mathrm{k}}_{\mathrm{B}}\mathrm{T}}\right),$ with parameters τ_r = 4 × 10⁻¹² s, and (E_B + E_ad)/k_B = 1473 K. On the other hand, the nanoparticles in the Ni50 ensemble freeze collectively upon cooling in a spin-glass fashion according to a critical dynamics law: $\tau (\mathrm{T})=\frac{{\tau }_0}{{\left[\frac{\mathrm{T}}{{\mathrm{T}}_{\mathrm{g}}}-1\right]}^{\mathrm{z}\mathsf{\nu }}}$, with τ₀ = 4 × 10⁻⁸ s, T_g = 145 K, and zν = 7.2. Rietveld refinements against powder X-ray diffraction data reveal the structural details that underlie the observed magnetic behavior: an indirect cation replacement mechanism by which non-magnetic Zn ions are incorporated in the tetrahedral sites of the inverse spinel. Full article

In Colombia, Micrurus snakebites are classified as severe according to the national clinical care guidelines and must be treated with specific antivenoms. Unfortunately, these types of antivenoms are scarce in certain areas of the country and are currently reported as an unavailable vital medicine. To address this issue, La Universidad de Antioquia, through its spin-off Tech Life Saving, is leading a project to develop third-generation polyvalent freeze-dried antivenom. The goal is to ensure access to this therapy, especially in rural and dispersed areas. This project aims to evaluate the physicochemical and preclinical parameters (standard quality characteristics) of a lab-scale anti-elapid antivenom batch. The antivenom is challenged against the venoms of several Micrurus species, including M. mipartitus, M. dumerilii, M. ancoralis, M. dissoleucus, M. lemniscatus, M. medemi, M. spixii, M. surinamensis, and M. isozonus, following the standard quality characteristics set by the World Health Organization (WHO). The antivenom demonstrates an appearance consistent with standards, 100% solubility within 4 min and 25 s, an extractable volume of 10.39 mL, a pH of 6.04, an albumin concentration of 0.377 mg/mL (equivalent to 1.22% of total protein), and a protein concentration of 30.97 mg/mL. Importantly, it maintains full integrity of its F(ab′)₂ fragments and exhibits purity over 98.5%. Furthermore, in mice toxicity evaluations, doses up to 15 mg/mouse show no toxic effects. The antivenom also demonstrates a significant recognition pattern against Micrurus venoms rich in phospholipase A₂ (PLA₂) content, as observed in M. dumerilii, M. dissoleucus, and M. isozonus. The effective dose 50 (ED₅₀) indicates that a single vial (10 mL) can neutralize 2.33 mg of M. mipartitus venom and 3.99 mg of M. dumerilii venom. This new anti-elapid third-generation polyvalent and freeze-dried antivenom meets the physicochemical parameters set by the WHO and the regulators in Colombia. It demonstrates significant efficacy in neutralizing the venom of the most epidemiologically important Micrurus species in Colombia. Additionally, it recognizes seven other species of Micrurus venom with a higher affinity for venoms exhibiting PLA₂ toxins. Fulfilling these parameters represents the first step toward proposing a new pharmacological alternative for treating snakebites in Colombia, particularly in dispersed rural areas, given that this antivenom is formulated as a freeze-dried product. Full article

Cloud and bubble chambers have historically been used for particle detection, capitalizing on supersaturation and superheating, respectively. Here, we present new results from a prototype snowball chamber, in which an incoming particle triggers the crystallization of a purified, supercooled liquid. We demonstrate, for the first time, simulation agreement with our first results from 5 years ago: the higher temperature of the freezing of water and significantly shorter time spent supercooled compared to the control in the presence of a Cf-252 fission neutron source. This is accomplished by combining Geant4 modeling of neutron interactions with the Seitz nucleation model used in superheated bubble chambers, including those seeking dark matter. We explore the possible implications of using this new technology for GeV-scale WIMP searches, especially in terms of spin-dependent proton coupling, and report the first supercooling of WbLS (water-based liquid scintillator). Full article

Here, we report the results of our ¹H nuclear magnetic resonance study of the dynamics of water molecules confined in zeolites (mordenite and ZSM-5 structures) with hierarchical porosity (micropores in zeolite lamella and mesopores formed by amorphous SiO₂ in the inter-lamellar space). ¹H nuclear magnetic resonance (NMR) spectra show that water experiences complex behavior within the temperature range from 173 to 298 K. The temperature dependence of ¹H spin-lattice relaxation evidences the presence of three processes with different activation energies: freezing (about 30 kJ/mol), fast rotation (about 10 kJ/mol), and translational motion of water molecules (23.6 and 26.0 kJ/mol for pillared mordenite and ZSM-5, respectively). For translational motion, the activation energy is markedly lower than for water in mesoporous silica or zeolites with similar mesopore size but with disordered secondary porosity. This indicates that the process of water diffusion in zeolites with hierarchical porosity is governed not only by the presence of mesopores, but also by the mutual arrangement of meso- and micropores. The translational motion of water molecules is determined mainly by zeolite micropores. Full article

Vegetatively propagating aquatic angiosperms, the Lemnaceae family (duckweeds) represents valuable genetic resources for circular bioeconomics and other sustainable applications. Due to extremely fast growth and laborious cultivation of in vitro collections, duckweeds are an urgent subject for cryopreservation. We developed a robust and fast DMSO-free protocol for duckweed cryopreservation by vitrification. A single-use device was designed for sampling of duckweed fronds from donor culture, further spin-drying, and subsequent transferring to cryo-tubes with plant vitrification solution 3 (PVS3). Following cultivation in darkness and applying elevated temperatures during early regrowth stage, a specific pulsed illumination instead of a diurnal regime enabled successful regrowth after the cryopreservation of 21 accessions of Spirodela, Landoltia, Lemna, and Wolffia genera, including interspecific hybrids, auto- and allopolyploids. Genome size measurements revealed no quantitative genomic changes potentially caused by cryopreservation. The expression of CBF/DREB1 genes, considered as key factors in the development of freezing tolerance, was studied prior to cooling but was not linked with duckweed regrowth after rewarming. Despite preserving chlorophyll fluorescence after rewarming, the rewarmed fronds demonstrated nearly zero photosynthetic activity, which did not recover. The novel protocol provides the basis for future routine application of cryostorage to duckweed germplasm collections, saving labor for in vitro cultivation and maintaining characterized reference and mutant samples. Full article

The hydration of ions and charge groups controls electro mass transfer through ion exchange systems. The self-diffusion and local mobility of water molecules as well as lithium cations in poly (4-styrenesulfonic acid) and its lithium, sodium and cesium salts were investigated for the first time using pulsed-field gradient NMR (PFG NMR) and NMR relaxation techniques. The temperature dependences of the water molecule and Li⁺ cation self-diffusion coefficients exhibited increasing self-diffusion activation energy in temperature regions below 0 °C, which is not due to the freezing of parts of the water. The self-diffusion coefficients of water molecules and lithium cations, as measured using PFG NMR, are in good agreement with the self-diffusion coefficients calculated based on Einstein’s equation using correlation times obtained from spin-lattice relaxation data. It was shown that macroscopic water molecules’ and lithium cations’ transfer is controlled by local particles jumping between neighboring sulfonated groups. These results are similar to the behavior of water and cations in sulfonic cation exchanger membranes and resins. It was concluded that polystyrenesulfonic acid is appropriate model of the ionogenic part of membranes based on this polymer. Full article

Research on polymer nanocomposite nanofibers has seen remarkable growth over the past several years. One of the main driving forces for this progress is the increasing applicability of polymer nanocomposite nanofibers for technological applications. This review basically aims to present the current state of manufacturing polymer/graphene nanofiber nanocomposites, using appropriate techniques. Consequently, various conducting and thermoplastic polymers have been processed with graphene nano-reinforcement to fabricate the nanocomposite nanofibers. Moreover, numerous methods have been adopted for the fabrication of polymer/graphene nanocomposites and nanofibers including interfacial polymerization, phase separation, freeze drying, template synthesis, drawing techniques, etc. For the formation of polymer/graphene nanocomposite nanofibers, electrospinning can be preferable due to various advantages such as the need for simple equipment, control over morphology, and superior properties of the obtained material. The techniques such as solution processing, melt spinning, and spin coating have also been used to manufacture nanofibers. Here, the choice of manufacturing techniques and parameters affects the final nanofiber morphology, texture, and properties. The manufactured nanocomposite nanofibers have been examined for exceptional structural, microstructure, thermal, and other physical properties. Moreover, the properties of polymer/graphene nanofiber rely on the graphene content, dispersion, and matrix–nanofiller interactions. The potential of polymer/graphene nanocomposite nanofibers has been investigated for radiation shielding, supercapacitors, membranes, and the biomedical field. Hence, this review explains the literature-driven significance of incorporating graphene in polymeric nanofibers. Conclusively, most of the studies focused on the electrospinning technique to design polymer/graphene nanofibers. Future research in this field may lead to advanced innovations in the design and technical applications of nanocomposite nanofibers. To the best of our knowledge, research reports are available on this topic; however, the stated literature is not in a compiled and updated form. Therefore, field researchers may encounter challenges in achieving future advancements in the area of graphene-based nanocomposite nanofibers without first consulting the recent literature, such as an assembled review, to gain necessary insights, etc. Consequently, this state-of-the-art review explores the manufacturing, properties, and potential of polymer/graphene nanocomposite nanofibers. Full article

Site-directed spin labeling followed by investigation using Electron Paramagnetic Resonance spectroscopy is a rapidly expanding powerful biophysical technique to study structure, local dynamics and functions of biomolecules using pulsed EPR techniques and nitroxides are the most widely used spin labels. Modern trends of this method include measurements directly inside a living cell, as well as measurements without deep freezing (below 70 K), which provide information that is more consistent with the behavior of the molecules under study in natural conditions. Such studies require nitroxides, which are resistant to the action of biogenic reductants and have high spin relaxation (dephasing) times, T_m. (1R(S),5R(S),7R(S),8R(S))-1,8-bis(hydroxymethyl)-6-azadispiro[4.1.4.2]tridecane-6-oxyl is a unique nitroxide that combines these features. We have developed a convenient method for the synthesis of this radical and studied the ways of its functionalization. Promising spin labels have been obtained, the parameters of their spin relaxation T₁ and T_m have been measured, and the kinetics of reduction with ascorbate have been studied. Full article

The use of ionic liquid-based membranes as polymer electrolyte membranes for fuel cell applications increases significantly due to the major features of ionic liquids (i.e., high thermal stability and ion conductivity, non-volatility, and non-flammability). In general, there are three major methods to introduce ionic liquids into the polymer membrane, such as incorporating ionic liquid into a polymer solution, impregnating the polymer with ionic liquid, and cross-linking. The incorporation of ionic liquids into a polymer solution is the most common method, owing to easy operation of process and quick membrane formation. However, the prepared composite membranes suffer from a reduction in mechanical stability and ionic liquid leakage. While mechanical stability may be enhanced by the membrane’s impregnation with ionic liquid, ionic liquid leaching is still the main drawback of this method. The presence of covalent bonds between ionic liquids and polymer chains during the cross-linking reaction can decrease the ionic liquid release. Cross-linked membranes reveal more stable proton conductivity, although a decrease in ionic mobility can be noticed. In the present work, the main approaches for ionic liquid introduction into the polymer film are presented in detail, and the recently obtained results (2019–2023) are discussed in correlation with the composite membrane structure. In addition, some promising new methods (i.e., layer-by-layer self-assembly, vacuum-assisted flocculation, spin coating, and freeze drying) are described. Full article