New Insights into the Role of Humic Acid in Permanganate Oxidation of Diclofenac: A Novel Electron Transfer Mechanism

Humic acid (HA) ubiquitously existing in aquatic environments has been reported to significantly impact permanganate (KMnO4) decontamination processes. However, the underlying mechanism of the KMnO4/HA system remained elusive. In this study, an enhancing effect of HA on the KMnO4 oxidation of diclofenac (DCF) was observed over a wide solution pH range of 5-9. Surprisingly, the mechanism of HA-induced enhancement varied with solution pH. Quenching and chemical probing experiments revealed that manganese intermediates (Mn(III)-HA and MnO2) were responsible for the enhancement under acidic conditions but not under neutral and alkaline conditions. By combining KMnO4 decomposition, galvanic oxidation process experiments, electrochemical tests, and FTIR and XPS analysis, it was interestingly found that HA could effectively mediate the electron transfer from DCF to KMnO4 in neutral and alkaline solutions, which was reported for the first time. The formation of an organic-catalyst complex (i.e., HA-DCF) with lower reduction potential than the parent DCF was proposed to be responsible for the accelerated electron transfer from DCF to KMnO4. This electron transfer likely occurred within the complex molecule formed through the interaction between HA-DCF and KMnO4 (i.e., HA-DCF-KMnO4). These results will help us gain a more comprehensive understanding of the role of HA in the KMnO4 oxidation processes.

Shifting Emphasis from Electro- to Catalytically Active Sites: Effects of Pore Size of Flow-Through Anodes on Water Purification

A flow-through anode has demonstrated high efficiency for micropollutant abatement in water purification. In addition to developing novel electrode materials, a rational design of its porous structure is crucial to achieve high electrooxidation kinetics while sustaining a low cost for flow-through operation. However, our knowledge of the relationship between the pore structure and its performance is still incomplete. Therefore, we systematically explore the effect of pore size (with a median from 4.7 to 49.4 μm) on the flow-through anode efficiency. Results showed that when the pore size was <26.7 μm, the electrooxidation kinetics was insignificantly improved, but the permeability declined dramatically. Traditional empirical evidence from hydrodynamic modeling and electrochemical tests indicated that a flow-through anode with a smaller pore size (e.g., 4.7 μm) had a high mass transfer capability and large electroactive area. However, this did not further accelerate the micropollutant removal. Combining an overpotential distribution model and an imprinting method has revealed that the reactivity of a flow-through anode is related to the catalytically active volume/sites. The rapid overpotential decay as a function of depth in the anode would offset the merits arising from a small pore size. Herein, we demonstrate an optimal pore size distribution (∼20 μm) of typical flow-through anodes to maximize the process performance at a low energy cost, providing insights into the design of advanced flow-through anodes in water purification applications.

Ti3C2Tx MXene/urchin-like PANI hollow nanosphere composite for high performance flexible ammonia gas sensor

Ammonia (NH₃) has been used as a typical indicator to monitor food spoilage, human health, and air quality. However, the development of flexible NH₃ sensors with high response, excellent selectivity and low cost remains a huge challenge. Herein, a high performance NH₃ sensor based on Ti₃C₂T_x MXene nanosheet/urchin-like PANI hollow nanosphere composite (MP) was fabricated through template method and in situ polymerization. The NH₃ sensor is fabricated with no high cost electrodes through directly depositing this composite on flexible polyethylene terephthalate (PET) during polymerization. This optimized MP film sensor exhibits high response of 3.70 to 10 ppm NH₃ at room temperature, which is 4.74-fold in comparison with urchin-like PANI hollow nanosphere (u-PANI). It also shows excellent selectivity, good repeatability, satisfactory flexibility, air stability and low detection limit of 30 ppb. The effective morphology control and heterojunction construction of MP composite are responsible for superior sensing performance. Moreover, the application of this film sensor in the monitoring of the spoilage process of fresh pork is demonstrated. This study offers a new strategy for fabricating high performance flexible room-temperature NH₃ sensors, which may be scale fabrication and application in daily life.

Indirect charging of carbon by aqueous redox mediators contributes to the enhanced desalination performance in flow-electrode CDI

Reversible electrochemical separation based on flow electrodes (e.g., flow-electrode capacitive deionization (FCDI)) is promising to desalinate brackish water, a reliable alternative source of freshwater. The deployment of redox mediators (RMs) in FCDI offers an energy-efficient means to improve the process performance, but the nature of the RMs-mediated charge transfer remains poorly understand. We therefore systematically investigated commonly-used RMs including sodium anthraquinone-2-sulfonate (AQS), 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), hydroquinone (HQ) and ferricyanide ([Fe(CN)₆]^3-). Results showed that the desalination rate could be increased by over 260% with the addition of 10 mM [Fe(CN)₆]^3-. The lowest efficiency of AQS among the RMs should be ascribed to its reduction potential of -0.84 V (vs. Ag/AgCl) exceeding the potential (-0.48 V) of the negatively charged current collector at 1.2 V. While aqueous TEMPO and HQ could facilitate salt removal, their loss of efficiencies upon sorption onto the carbon surface indicated the insignificant pseudocapacitive contribution to ion migration. In-situ cyclic voltammetry measurements demonstrated the crucial role of the indirect charging of the flowable carbon materials to enhance the desalination performance in RMs-mediated FCDI. To sum up, results of this work pave a way to understand the RMs-mediated charge transfer and ion migration in FCDI, which would serve the purpose of design and optimization of the flow electrode systems for wider environmental applications.

Construction of multifunctional porcine acellular dermal matrix hydrogel blended with vancomycin for hemorrhage control, antibacterial action, and tissue repair in infected trauma wounds

Prevention of bacterial infection and reduction of hemorrhage, the primary challenges posed by trauma before hospitalization, are essential steps in prolonging the patient's life until they have been transported to a trauma center. Extracellular matrix (ECM) hydrogel is a promising biocompatible material for accelerating wound closure. However, due to the lack of antibacterial properties, this hydrogel is difficult to be applied to acute contaminated wounds. This study formulates an injectable dermal extracellular matrix hydrogel (porcine acellular dermal matrix (ADM)) as a scaffold for skin defect repair. The hydrogel combines vancomycin, an antimicrobial agent for inducing hemostasis, expediting antimicrobial activity, and promoting tissue repair. The hydrogel possesses a porous structure beneficial for the adsorption of vancomycin. The antimicrobial agent can be timely released from the hydrogel within an hour, which is less than the time taken by bacteria to infest an injury, with a cumulative release rate of approximately 80%, and thus enables a relatively fast bactericidal effect. The cytotoxicity investigation demonstrates the biocompatibility of the ADM hydrogel. Dynamic coagulation experiments reveal accelerated blood coagulation by the hydrogel. In vivo antibacterial and hemostatic experiments on a rat model indicate the healing of infected tissue and effective control of hemorrhaging by the hydrogel. Therefore, the vancomycin-loaded ADM hydrogel will be a viable biomaterial for controlling hemorrhage and preventing bacterial infections in trauma patients.

Enhanced photocatalytic degradation of perfluorooctanoic acid by Ti3C2 MXene-derived heterojunction photocatalyst: Application of intercalation strategy in DESs

In-situ construction of heterojunction photocatalyst on two-dimensional (2D) Ti₃C₂ MXene substrate has been proved to be a feasible method to enhance the photocatalytic degradation of organic pollutants. However, the limited interlayer spacing of 2D Ti₃C₂ hinders the in-situ growth of TiO₂ photocatalyst. Herein, the intercalation strategy was developed in deep eutectic solvents (DESs) method to achieve interlayer expansion of Ti₃C₂ and improve Ti₃C₂-derived photocatalyst performance. Because of the intercalation of choline cations, the DESs method synthesized Ti₃C₂ (Ti₃C₂-DES) had the larger c-lattice parameter than that of traditional HF method synthesized Ti₃C₂ (Ti₃C₂-HF). The interlayer space of Ti₃C₂-DES could be intercalated with more water molecule for oxidization of the Ti atoms, which remarkably promoted the in-situ growth of TiO₂ crystals. The formed heterojunction between (001) and (101) facets enhanced carriers separation. The Ti₃C₂ substrate with excellent conductivity further promoted carriers transfer. As a result, Ti₃C₂/TiO₂ photocatalyst exhibited superior perfluorooctanoic acid (PFOA) removal performance (almost 100% removal efficiency and 49% defluorination efficiency within 16 h) compared with the traditional Ti₃C₂-HF/TiO₂ (22% removal efficiency and 12% defluorination efficiency within 16 h). This study provides a feasible strategy for enhancing photocatalytic degradation of PFOA by Ti₃C₂ MXene-derived heterojunction photocatalyst.

Analysis of related factors in complications of stereotactic radiosurgery in intracranial tumors

OBJECT

To investigate the related factors in complications of stereotactic radiosurgery for intracranial tumors.

METHODS

A retrospective review of 146 patients with intracranial tumors treated with stereotactic radiosurgery was conducted. Sixty-five patients received single-dose treatment and the rest received fractionated stereotactic radiosurgery. Ninety-five patients received conventional radiotherapy in the meantime.

RESULTS

Follow-up period was 18-54 months. Follow-up rate was 92.5% and 39 patients (26.7%) had different complications. The Cox statistics showed that target volume, target peripheral dose, target maximal dose, and ratio of maximal dose to peripheral dose are related to the complications. Conversely, neither type of tumor disease, gender, radiation schedule with or without conventional radiotherapy, target minimal dose, nor ratio of target peripheral isodose volume to target volume were found to be related to complications.

CONCLUSION

Target volume and dose are the major factors causing complications, and the optimization of the therapeutic planning can play a significant role in reducing them.