RESUMEN

Li2SrSiO4:Eu2+ is a promising substitute for traditional Y3Al5O12:Ce3+ (YAG:Ce3+) owing to its strong orange-yellow emission of 4f-5d transition originating from Eu2+ dopant, covering the more red-light region. However, its inevitable luminescence thermal quenching at high temperatures and the self-oxidation of Eu2+ strongly impede their applications. Their remediation remains highly challenging. Herein, an anti-self-oxidation(ASO) concept of Eu2+ in Li2SrSiO4 substrate by adding trivalent rare-earth ions (A3+: A = La, Gd, Y, Lu) for highly efficient and stable orange-yellow light emission have been proposed. A significantly increased orange-yellow emission (202% improvement) from Li2Sr0.95A0.05SiO4:Eu2+ with a wide range near-zero thermal quenching is obtained, superior to other Eu2+ activated phosphors. The presence of A3+ ions with various radii modifies the ASO degree of Eu2+ ions, achieving the tunable chemical state, composition, electronic configuration, crystal-field strength, and luminescent characteristics of the developed phosphors. For the proof of the concept, a W-LED device and a PDMS (Polydimethylsiloxane) luminescent film are fabricated, endowing excellent luminescence performance and thermal stability and the huge application prospects of Li2SrSiO4:Eu2+ in lighting and display fields.

RESUMEN

Droplet-based microfluidics-assisted fabrication of alginate microgels has extensive applications in biomaterials, biomedicines, and related fields. This approach is typically achieved by crosslinking droplets of an aqueous solution of sodium alginate with various divalent and trivalent ions, such as Ca2+, Ba2+, Sr2+, etc. Despite the exceptional features exhibited by bulk alginate hydrogels when using iron ions as the crosslinking reagent, including stimulus responsiveness and complex chemistry, no attention has been given to studying the fabrication of Fe-alginate microgels through droplet microfluidics. In this work, a facile method is presented for fabricating Fe-alginate microgels using single emulsion droplets as templates and an off-chip crosslinking technique to solidify the droplets. The morphologies of the resulting microgels can be systematically adjusted by manipulating different parameters such as viscosities and ionic strength of the collecting solutions. It should be noted that these resulting microgels undergo a color change from light brown to dark brown due to presumed self-oxidation of iron ions within their skeleton structure. Furthermore, these Fe-alginate microgels are functionalized by decorating them with a positively charged linear polymer via electrostatic interactions to impart them with stable fluorescent property. These functionalized Fe-alginate microgels may find potential applications in drug delivery carriers and biomimetic structures.

Asunto(s)

RESUMEN

Enriching erythrocytes and platelets in seconds and providing a fast seal in bleeding sites is vital to fatal hemorrhage control. Herein, hydrophilic chitosan fibrous mats (CECS-D mats) are fabricated by introducing hydrophilic carboxyethyl groups and subsequent catechol groups onto chitosan fibers. Due to strong hydrophilicity, CECS-D mats exhibit rapid liquid-absorption capacity, especially instantaneous absorptivity to the rabbit blood, which can achieve erythrocyte and platelet aggregations quickly by concentrating blood, thus promoting the formation of blood clots. Furthermore, the mats are self-oxidated to form quinone-amine adducts or quinone multimers by adjusting pH conditions, which not only provides tissue adhesion but also induces erythrocyte aggregation and platelet adhesion, further enhancing the seal and triggering quick closure to achieve fast hemostasis. Therefore, the mats reveal superior hemostatic performance in rabbit liver and spleen models over CECS mats and gauze. Especially in the fatal femoral artery injury model of rabbits, the mats reduce the blood loss by ∼75% and shortened the bleeding time by ∼50% compared with CECS mats, which have been reported to have the same hemostatic effect as commercialized Celox products in a swine femoral artery injury model. Besides, the mats are cytocompatible and degradable as well as antibacterial. This chitosan mat is a promising hemostatic material for fatal hemorrhage control.

Asunto(s)

RESUMEN

Currently, the copolymer of dopamine (DA) and pyrrole (PY) via chemical and electrochemical oxidation usually requires additional oxidants, and lacks flexibility in regulating the size and morphology, thereby limiting the broad applications of DA-PY copolymer in biomedicine. Herein, the semiquinone radicals produced by the self-oxidation of DA is ingeniously utilized as the oxidant to initiate the following copolymerization with PY, and a series of quinone-rich polydopamine-pyrrole copolymers (PDAm-nPY) with significantly enhanced absorption in near-infrared (NIR) region without any additional oxidant assistance is obtained. Moreover, the morphology and size of PDAm-nPY can be regulated by changing the concentration of DA and PY, thereby optimizing nanoscale PDA0.05-0.15PY particles (≈ 150 nm) with excellent NIR absorption and surface modification activity are successfully synthesized. Such PDA0.05-0.15PY particles show effective photoacoustic (PA) imaging and photothermal therapy (PTT) against 4T1 tumors in vivo. Furthermore, other catechol derivatives can also copolymerize with PY under the same conditions. This work by fully utilizing the semiquinone radical active intermediates produced through the self-oxidation of DA reduces the dependence on external oxidants in the synthesis of composite materials and predigests the preparation procedure, which provides a novel, simple, and green strategy for the synthesis of other newly catechol-based functional copolymers.

Asunto(s)

RESUMEN

Copper surfaces that exhibit a wide range of achromatic colors while still metallic have not been studied, despite advancements in antireflection coatings. A series of achromatic copper films grown with [111] preferred orientation by depositing 3D porous nanostructures is introduced via coherent/incoherent atomic sputtering epitaxy. The porous copper nanostructures self-regulate the giant oxidation resistance by constructing a curved surface that generates a series of monoatomic steps, followed by shrinkage of the lattice spacing of one or two surface layers. First-principles calculations confirm that these structural components cooperatively increase the energy barrier against oxygen penetration. The achromaticity of the single-crystalline porous copper films is systematically tuned by geometrical parameters such as pore size distribution and 3D linkage. The optimized achromatic copper films with high oxidation resistance show an unusual switching effect between superhydrophilicity and superhydrophobicity. The tailored 3D porous nanostructures can be a candidate material for numerous applications, such as antireflection coatings, microfluidic devices, droplet tweezers, and reversible wettability switches.

RESUMEN

It is known that there are semiconductor oxides involved in mineral dust, which have photocatalytic properties. However, soot particles contained in carbonaceous aerosol and their photoactivity under sunlight are rarely realized. In this study, reactive oxygen species (ROS) such as superoxide anions and hydroxyl radicals were generated upon visible-light irradiation of soot particles, and the production activity was consistent with the carbonaceous core content, indicating that the atmospheric soot particles can serve as a potential photocatalyst. The increase of oxygen-containing functional groups, environmentally persistent free radicals, oxygenated polycyclic aromatic hydrocarbons, and the oxidative potential (OP) of soot after irradiation confirmed the occurrence of visible-light-triggered photocatalytic oxidation of the soot itself. The mechanism analyses suggested that the carbonaceous core caused the production of ROS, which subsequently oxidize the extractable organic species on the soot surface. It is oxidized organic extracts that are responsible for the enhancements of the OP, cell mortality, and intracellular ROS generation. These new findings shed light on both the photocatalytic role of the soot and the importance of ROS during the photochemical self-oxidation of soot triggered by visible light and will promote a more comprehensive understanding of both the atmospheric chemical behavior and health effects of soot particles.

Asunto(s)

RESUMEN

Soil contamination due to chlorinated organics prompts an important environmental problem; however, the iron-based reduction materials and complicated ground environment are the main barriers to implementation and promotion of in situ soil remediation. Therefore, this study aims to evaluate the reductants zero-valent iron (ZVI) and its activated carbon composite (AC-ZVI) in terms of their self-oxidation and selectivity in soil experiments. The results indicated that saturated moisture conditions were beneficial for degradation due to the dispersal of the pollutants from soil particles. Particularly, increasing the water/soil ratio to the over-saturated state would decrease the selectivity of ZVI and AC-ZVI. Meanwhile, increasing the reductant loading decreased the selectivity of ZVI and AC-ZVI, whereas the high initial concentration increased the selectivity of AC-ZVI. In addition, the self-oxidation of ZVI (3.0 ×10-3 h-1) is 4.2 times higher than that of AC-ZVI (0.7 ×10-3 h-1), and the selectivity of AC-ZVI (48%) is 6.9 times higher than that of ZVI (7%), which confirmed that AC-ZVI is a superior iron-based amendment in saturated moisture conditions. Therefore, this study provides a reliable and feasible evaluation method for in situ remediation process, and deepens the understanding of the effects of moisture contents.

Asunto(s)

RESUMEN

As a competitive anode material for sodium-ion batteries (SIBs), a commercially available red phosphorus, featured with a high theoretical capacity (2596 mA h g-1) and a suitable operating voltage plateau (0.1-0.6 V), has been confronted with a severe structural instability and a rapid capacity degradation upon large volumetric change. In particular, the fundamental determining factors for phosphorus anode materials are yet poorly understood, and their interfacial stability against ambient air has not been explored and clarified. Herein, a high-performance phosphorus/carbon anode material has been fabricated simply through ball-milling the carbon black and red phosphorus, delivering a high reversible capacity of 1070 mA h g-1 at 400 mA g-1 after 200 cycles and a superior rate capability of 479 mA h g-1 at 3200 mA g-1. More importantly, we first reveal the significance of inhibiting the exposure of phosphorus/carbon electrode materials to air, even for a short period, for achieving a good electrochemical performance, which would sharply decrease the reversible capacities. With the assistance of synchrotron-based X-ray techniques, the formation and accumulation of insulating phosphate compounds can be spectroscopically identified, leading to the decay of electrochemical performance. At the same time, these passivation layers on the surface of electrode were found to occur via a self-oxidation process in ambient air. To maintain the electrochemical advantages of phosphorus anodes, it is necessary to inhibit their contact with air through a rational coating or an optimal storage condition. Additionally, the employment of a fluoroethylene carbonate (FEC) additive facilitates the decomposition of the electrolyte and favors the formation of a robust solid electrolyte interphase layer, which may suppress the side reactions between the active Na-P compounds and the electrolyte. These findings could help improve the surface protection and interfacial stability of phosphorus anodes for high-performance SIBs.

RESUMEN

Self-oxidation/dissociation of some quaternary ammonium permanganates (QAPs), such as cetyltrimethylammonium permanganate (CTAP) and tetrabutylammonium permanganate (TBAP), have been studied spectrophotometrically in six different organic solvent media of different polarities wherein the compounds show good solubility and stability. The optical densities of the substrates at zero time (ODo) and first-order rate constants of dissociation (k1) have been determined from their successive scanning for 40min. At comparable experimental conditions, absorption capabilities of the substrates are compared from the ODo values in various organic media; the stability of the solutions is compared from the successive scan spectra in those media. The ODo values and the k1 values have been plotted against some solvent parameters to understand their effects on the absorbance and reactivity of the QAPs. These data are also subjected to multiple regression analysis to explain the influence of various solvent parameters on the ion-pairing properties of the substrates, thus elucidating their effects on the process of self-oxidation/dissociation of the substrates.

Asunto(s)