Search Results (49)

Tocopheramines are a class of antioxidants which are distinguished from tocopherols (vitamin E) by the presence of an amino group instead of the phenolic hydroxyl group. α-Tocopheramine is intensively studied for biomedical applications but also as a stabilizer for synthetic and natural polymers, in particular for cellulose solutions and spinning dopes for cellulosic fibers. This study addresses a fundamental difference in the oxidation chemistry of α-tocopheramine and its tocopherol counterpart: while the formation of the ortho-quinone methide (o-QM) involving C-5a is one of the most fundamental reactions of α-tocopherol, the corresponding ortho-iminoquinone methide (o-IQM) derived from α-tocopheramine has been elusive so far. Synthesis of the transient intermediate succeeded initially via 5a-hydroxy-α-tocopheramine, and its occurrence was confirmed by dimerization to the corresponding spiro-dimer and by trapping with ethyl vinyl ether. Eventually, suitable oxidation conditions were found which allowed for the generation of the o-IQM directly from α-tocopheramine. The underlying oxidation chemistry of α-tocopherol and α-tocopheramine is concisely discussed. Full article

In sodium-ion batteries, the research of electrode and separator materials must work in tandem. However, the existing separators still need to go through a drawn-out procedure in order to satisfy the engineering and technological standards of sodium-ion batteries. A new sodium-ion battery separator was created for this investigation. Electrostatic spinning was used to create polyacrylonitrile (PAN)/ZnO nanofiber films, and varying the ZnO nanoparticle doping level enhanced the nanofiber separator’s cyclic stability. A new flexible PAN separator for sodium-ion batteries is presented in this study. It has good commercial value and may find use in flexible, high safety sodium-ion battery systems. Additionally, it offers some theoretical direction for creating organic polymer separators with excellent safety. Full article

Electrospinning of polymer material has gained a lot of interest in the past decades. Various methods of electrospinning have been applied for different applications, from needle electrospinning to needleless electrospinning. A relatively new variation of electrospinning, namely near-field electrospinning, has been used to generate well-defined patterns. This variation of electrospinning, also known as near-field direct-write electrospinning, allows for precise control of the fiber deposition, sacrificing on the thickness of the resulting fibers. Typically, for this method, melt electrospinning is preferred, since it provides a higher viscosity of the polymer and thereby better control of the fiber deposition. However, when mixing additives into the spinning dope, a solution spinning approach is preferable since it provides a more homogeneous distribution of the additives in the spinning dope. A fluorescent spinning dope of dissolved PET with fluorescent carbon quantum dots has been used to generate the fluorescent patterns. These can be used to generate logos, bar codes, or QR codes to encode information about the material, such as watermarks or counterfeiting tags. Full article

TiO₂ nanoparticles (NPs) doped with W (W:TiO₂), double-doped with W and V (W&V:TiO₂), and loaded with noble metals (W:TiO₂ @Pt/Pd/Ag and W&V:TiO₂@Pt/Pd/Ag) were synthesized by laser pyrolysis followed by chemical impregnation and reduction. Due to its exceptional properties, TiO₂ is considered a key material being used in a wide range of applications. To improve its detection activity, the increase in the specific surface of the material, and the presence of defects in its structure play a decisive role. Doped and double-doped TiO₂ nanoparticles with dimensions in the range of 25–30 nm presented a mixture of phases corresponding to titania, with the anatase phase accounting for the majority (95%). By loading these nanoparticles with small particles of noble metals, a significant increase in the specific surface area by three or even five times the original values was achieved. Sensitive thin films for surface acoustic wave (SAW) sensors were made with the NPs, embedded in polyethyleneimine (PEI) polymer and deposited by spin-coating. Each sensor was tested at CH₄ concentrations between 0.4 and 2%, at room temperature, and the best results were obtained by the sensor with NPs doped with V and decorated with Pd, with a limit of detection (LOD) of 17 ppm, due to the strong catalytic effect of Pd. Full article

Alginate, categorized as a natural-based biodegradable polymer, stands out for its inherently exclusive properties. Although this unique polymer is widely processed using film, coating, and membrane technologies for different usage areas, textile applications are still limited. This study aims to compile promising approaches that will pave the way for the use of wet-spun alginate filaments in textile applications. In this regard, this study provides information about the molecular structure of alginate, the gel formation mechanism, and cross-linking using different techniques. Our literature review categorizes parameters affecting the mechanical properties of wet-spun alginate filaments, such as the effect of ion source and spinning dope concentration, needle diameter, temperature, and coagulants. Following this, a detailed and comprehensive literature review of the various approaches, such as use of additives, preparation of blended filaments, and grafted nanocrystal addition, developed by researchers to produce composite alginate filaments is presented. Additionally, studies concerning the use of different cations in the coagulation phase are reported. Moreover, studies about the functionalism of wet-spun alginate filaments have been offered. Full article

Developing materials with dynamic room-temperature phosphorescence (RTP) properties is crucial for expanding the applications of organic light-emitting materials. In this study, we designed and synthesized two novel RTP molecules by combining functional units, incorporating the folded unit thianthrene into the classic luminescent cores thioxanthone or anthraquinone to construct TASO and TA2O. In this combination, the TA unit contributes to the enhancement of spin–orbit coupling (SOC), while the luminescent core governs the triplet energy level. After the strategic manipulation of SOC using the thianthrene unit, the target molecules exhibited a remarkable enhancement in RTP performance. This strategy led to the successful development of TASO and TA2O molecules with outstanding dynamic RTP properties when exposed to continuous ultraviolet irradiation, a result that can be ascribed to their efficient RTP, improved absorption ability, and oxygen-sensitive RTP properties. Leveraging the oxygen-mediated ultraviolet-radiation-induced RTP enhancement in TASO-doped polymer films, we developed a novel time-resolved detection technique for identifying phase separation in polymers with varying oxygen permeability. This research offers a promising approach for constructing materials with dynamic RTP properties. Full article

To produce highly efficient and repeatable perovskite solar cells (PSCs), comprehending interfacial loss and developing approaches to ameliorate interfacial features is essential. Nonradiative recombination at the SnO₂–perovskite interface in SnO₂-based perovskite solar cells (PSCs) leads to significant potential loss and variability in device performance. To improve the quality of the SnO₂ electron transport layer, a novel polymer-doped SnO₂ matrix, specifically using polyacrylic acid, was developed. This matrix is formed by spin-coating a SnO₂ colloidal solution that includes polymers. The polymer aids in dispersing nanoparticles within the substrate and is evenly distributed in the SnO₂ solution. As a result of the polymer addition, the density and wetting properties of the SnO₂ layer substantially improved. Subsequently, perovskite-based photovoltaic devices comprising SnO₂ and Spiro-OMeTAD layers and using (FAPbI₃)_0.97(MAPbBr₃)_0.03 perovskite are constructed. These optimized devices exhibited an increased efficiency of 17.2% when compared to the 15.7% power conversion efficiency of the control device. The incorporation of polymers in the electron transport layer potentially enables even better performance in planar perovskite solar cells. Full article

Commercially available formulations of the popular conductive polymer, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) are aqueous dispersions that require the addition of secondary dopants such as dimethyl sulphoxide (DMSO) or ethylene glycol (EG) for fabricated films to have the desired levels of conductivity. Clevios^TM F HC Solar, a formulation of PEDOT:PSS produced by Heraeus, GmbH, achieves over 500 S/cm without these secondary dopants. This work studies whether secondary dopants such as DMSO have any additional effect on this type of PEDOT:PSS. The temperature dependencies of the conductivity of F HC Solar spin-coated thin films measured using a four-probe method seem to exhibit different charge transport properties compared with secondary doped PH1000. Observations made using atomic force microscopy (AFM) show that different concentrations of DMSO affect the orientation of the PEDOT domains in the thin film. These morphological changes cause room temperature conductivity to reduce from 640 S/cm in pristine films to as low as 555 S/cm after adding 7 wt% of DMSO along the film. Such tuning may prove useful in future applications of PEDOT:PSS, such as nanoprobes, transistors and hybrid solar cells. Full article

Although the effect of the conductive polymers PEDOT:PSS on the electroluminescence performance of doped-type organic light-emitting diodes (OLEDs) has been studied, the process of PEDOT:PSS regulation of exciton recombination region and concentration within the deoxyribonucleic acid (DNA)-based doped-type BioLEDs is still obscure. In this study, we fabricated Bio-devices with and without PEDOT:PSS using varying spin-coating speeds of PEDOT:PSS. The Alq₃:Rubrene-based BioLEDs achieve higher luminance (44,010 cd/m²) and higher luminance efficiency (8.1 cd/A), which are increased by 186% and 478%, respectively, compared to the reference BioLEDs without PEDOT:PSS. Similarly, the maximum luminance and efficiency of blue TCTA:TPBi exciplex-type BioLEDs are increased by 224% and 464%. In particular, our findings reveal that with an increasing thickness of PEDOT:PSS, the region of exciton recombination shifts towards the interface between the emitting layer (EML) and the hole transport layer (HTL). Meanwhile, the concentration of singlet exciton (S_1,Rub) and triplet exciton (T_1,Rub) increases, and the triplet-triplet annihilation (TTA) process is enhanced, resulting in the enhanced luminescence and efficiency of the devices. Accordingly, we provide a possible idea for achieving high performance doped-type BioLEDs by adding conductive polymers PEDOT:PSS, and revealing the effect of exciton recombination and conversion in BioLEDs given different PEDOT:PSS thicknesses. Full article

Polylactic acid (PLA) is a biodegradable polymer made from natural sources, and its electrospinning (e-spinning) nanofiber membrane doped with antibacterial ingredients is widely used in the field of medical dressings. In this research, 9 wt% of rosmarinic acid (RosA) and 0.04 wt% of graphite oxide (GO) with synergistic antibacterial activity were introduced into the e-spinning PLA precursor solution, and the obtained PLA nanofiber membrane showed good antibacterial properties and wound healing effects. At the same time, a nonionic amphiphilic polymer, polyethylene glycol (PEG), was also introduced into this system to improve the hydrophilicity of the e-spinning membrane for wound healing application. The morphological characterization showed the RosA/GO and PEG did not affect the e-spinning of PLA. The tests of mechanical performance and wettability demonstrated that PEG and RosA/GO incorporated in PLA have migrated easily to the surface of the fiber. The e-spun PLA/PEG/RosA/GO membrane showed good antibacterial activity and promoted initial wound healing quickly, which would be a promising application in wound dressing. Full article

Polyvinylidene fluoride (PVDF)-based dielectric energy storage materials have the advantages of environmental friendliness, high power density, high operating voltage, flexibility, and being light weight, and have enormous research value in the energy, aerospace, environmental protection, and medical fields. To investigate the magnetic field and the effect of high-entropy spinel ferrite (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ nanofibers (NFs) on the structural, dielectric, and energy storage properties of PVDF-based polymers, (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ NFs were prepared via the use of electrostatic spinning methods, and (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄/PVDF composite films were prepared via the use of the coating method. The effects of a 0.8 T parallel magnetic field, induced for 3 min, and the content of high-entropy spinel ferrite on the relevant electrical properties of the composite films are discussed. The experimental results show that, structurally, the magnetic field treatment causes the originally agglomerated nanofibers in the PVDF polymer matrix to form a linear fiber chain with different fiber chains parallel to each other along the magnetic field direction. Electrically, the introduction of the magnetic field enhanced the interfacial polarization, and the (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄/PVDF composite film with a doping concentration of 10 vol% had a maximum dielectric constant of 13.9, as well as a low energy loss of 0.068. The high-entropy spinel ferrite (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ NFs and the magnetic field influenced the phase composition of the PVDF-based polymer. The α-phase and γ-phase of the cohybrid-phase B1 vol% composite films had a maximum discharge energy density of 4.85 J/cm³ and a charge/discharge efficiency of 43%. Full article

The rate of photocatalytic oxidation of polystyrene over 0.1 wt% copper-doped TiO₂ catalyst spin coated onto a flat substrate is investigated as a function of the catalyst deposition spin speed and, hence, film thickness. Photoinduced force microscopy and photoelectron spectroscopy show no evidence of any products of the photocatalytic oxidation remaining on the surface after reaction. The oxidation reaction shows no discernible dependence on spin speed; it is close to zero order in polystyrene concentration and exhibits a ½ life almost 50 times greater than the equivalent photocatalytic oxidation of stearic acid on the same catalysts. No difference between the rate of decay of the aliphatic and aromatic hydrogens of the polymer was observed, suggesting that once a polymer chain begins oxidising, subsequent steps are relatively rapid. This is consistent with the rate-determining step being dependent on the extent of coordination to the surface, which is much more favourable with stearic acid because of its carboxylic group. Full article

In this study, polymer-dispersed liquid crystal (PDLC) membranes were prepared by combining prepolymer, liquid crystal, and nanofiber mesh membranes under UV irradiation. EM, POM, and electro-optic curves were then used to examine the modified polymer network structure and the electro-optical properties of these samples. As a result, the PDLCs with a specific amount of reticular nanofiber films had considerably improved electro-optical characteristics and antiaging capabilities. The advancement of PDLC incorporated with reticulated nanofiber films, which exhibited a faster response time and superior electro-optical properties, would greatly enhance the technological application prospects of PDLC-based smart windows, displays, power storage, and flexible gadgets. Full article

The perovskite LaCoO₃ and La_0.8Sr_0.2CoO₃ thin films were synthesized successfully by a polymer-assisted deposition method. The structural characterization and thermal decomposition measurements indicate that appropriately increasing the annealing temperature is helpful in improving the film crystallinity. Compared with LaCoO₃ films, the Curie temperature is enhanced to a higher temperature in La_0.8Sr_0.2CoO₃ films, which is attributed to the changes in both the valence state and spin state induced by the chemical doping. In addition, a broad transition temperature region is observed in La_0.8Sr_0.2CoO₃ films, revealing the existence of inhomogeneous ground states in this system. Full article

The aim of this project is to fabricate hydrogen-rich silicone doped with magnetic nanoparticles for use as a temperature change indicator in magnetic resonance imaging-guided (MRIg) thermal ablations. To avoid clustering, the particles of mixed MnZn ferrite were synthesized directly in a medical-grade silicone polymer solution. The particles were characterized by transmission electron microscopy, powder X-ray diffraction, soft X-ray absorption spectroscopy, vibrating sample magnetometry, temperature-dependent nuclear magnetic resonance relaxometry (20 °C to 60 °C, at 3.0 T), and magnetic resonance imaging (at 3.0 T). Synthesized nanoparticles were the size of 4.4 nm ± 2.1 nm and exhibited superparamagnetic behavior. Bulk silicone material showed a good shape stability within the study’s temperature range. Embedded nanoparticles did not influence spin–lattice relaxation, but they shorten the longer component of spin–spin nuclear relaxation times of silicone’s protons. However, these protons exhibited an extremely high r₂^* relaxivity (above 1200 L s⁻¹ mmol⁻¹) due to the presence of particles, with a moderate decrease in the magnetization with temperature. With an increased temperature decrease of r₂^*, this ferro–silicone can be potentially used as a temperature indicator in high-temperature MRIg ablations (40 °C to 60 °C). Full article