M-N3 Configuration on Boron Nitride Boosts Singlet Oxygen Generation via Peroxymonosulfate Activation for Selective Oxidation.

Singlet oxygen (1O2) is an essential reactive species responsible for selective oxidation of organic matter, especially in Fenton-like processes. However, due to the great limitations in synthesizing catalysts with well-defined active sites, the controllable production and practical application of 1O2 remain challenging. Herein, guided by theoretical simulations, a series of boron nitride-based single-atom catalysts (BvBN/M, M=Co, Fe, Cu, Ni and Mn) were synthesized to regulate 1O2 generation by activating peroxymonosulfate (PMS). All the fabricated BvBN/M catalysts with explicit M-N3 sites promoted the self-decomposition of the two PMS molecules to generate 1O2 with high selectivity, where BvBN/Co possessed moderate adsorption energy and d-band center exhibited superior catalytic activity. As an outcome, the BvBN/Co-PMS system coupled with membrane filtration technology could continuously transform aromatic alcohols to aldehydes with nearly 100 % selectivity and conversion rate under mild conditions, suggesting the potential of this novel catalytic system for green organic synthesis.

Separation and reutilization of heavy metal ions in wastewater assisted by p-BN adsorbent.

Extracting heavy metal ions from wastewater has significant implications for both environmental remediation and resource preservation. However, the conventional adsorbents still suffer from incomplete ion removal and low utilization efficiency of the recovered metals. Herein, we present an extraction and reutilization method assisted by porous boron nitride (p-BN) containing high-density N atoms for metal recovery with simultaneous catalyst formation. The p-BN exhibits stable and efficient metal adsorption performance, particularly for ultra-trace-level water purification. The distribution coefficients towards Pb2+, Cd2+, Co2+ and Fe3+ can exceed 106 mL g-1 and the residual concentrations that reduced from 1 mg L-1 to 0.8-1.3 µg L-1 are much lower than the acceptable limits in drinking water standards of World Health Organization. Meanwhile, the used p-BN after Co ion adsorption can be directly adopted as a high-efficiency catalyst for activating peroxymonosulfate (PMS) in organic pollutant degradation without additional post-treatment, avoiding the secondary metal pollution and the problems of neglected manpower and energy consumption. Moreover, a flow-through multistage utilization system assisted by p-BN/polyvinylidene fluoride (PVDF) membrane is constructed for achieving both metal ion separation and reutilization in the removal of organic pollutants, providing a new avenue for sustainable wastewater remediation.

Ultrasound-mediated multifunctional magnetic microbubbles for drug delivery of celastrol in VX2 liver transplant tumors.

Celastrol (CST) has positive pharmacological effects on various cancers, but clinical application is limited because of poor water solubility and systemic toxicity. Ferric oxide (Fe3O4) has a large specific surface area and can be functionalized by inorganic modification to form complex magnetic drug delivery systems. Herein, Fe3O4 was surface-modified with citric acid and polyethylene glycol (PEG) (via) the Mitsunobu reaction and then covalently bound to CST. Finally, magnetic microbubbles (MMBs) containing perfluoropropane (C3F8) and Fe3O4-PEG2K-CST particles were constructed with poly(lactic-co-glycolic acid) (PLGA) as the shell membrane. In vitro studies showed that ultrasound-mediated MMBs exhibited improved inhibition of VX2 cell proliferation compared to inhibition achieved using MMBs without ultrasound mediation, blank MMBs, or free CST. In ultrasound mode, MMBs have favorable imaging properties. After the application of a high mechanical index, MMBs collapse through the cavitation effect, releasing their internal Fe3O4-PEG2K-CST. The CST is then delivered to the tumor microenvironment under acidic conditions. In magnetic resonance imaging T2 mode, a specific hypointense signal was observed in the tumor area compared with that before treatment, whereas no significant change occurred in the signal intensity of the surrounding organs. After treatment, pathological examination of tumor-bearing rabbit tissues showed that iron elements accumulated in several apoptosis cells in the tumor area, with no apparent abnormalities found in other areas. Thus, ultrasound-mediated MMBs could significantly improve the drug uptake of solid tumors and inhibit tumor growth with favorable biological safety.

A polymer tethering strategy to achieve high metal loading on catalysts for Fenton reactions.

The development of heterogenous catalysts based on the synthesis of 2D carbon-supported metal nanocatalysts with high metal loading and dispersion is important. However, such practices remain challenging to develop. Here, we report a self-polymerization confinement strategy to fabricate a series of ultrafine metal embedded N-doped carbon nanosheets (M@N-C) with loadings of up to 30 wt%. Systematic investigation confirms that abundant catechol groups for anchoring metal ions and entangled polymer networks with the stable coordinate environment are essential for realizing high-loading M@N-C catalysts. As a demonstration, Fe@N-C exhibits the dual high-efficiency performance in Fenton reaction with both impressive catalytic activity (0.818 min-1) and H2O2 utilization efficiency (84.1%) using sulfamethoxazole as the probe, which has not yet been achieved simultaneously. Theoretical calculations reveal that the abundant Fe nanocrystals increase the electron density of the N-doped carbon frameworks, thereby facilitating the continuous generation of long-lasting surface-bound •OH through lowering the energy barrier for H2O2 activation. This facile and universal strategy paves the way for the fabrication of diverse high-loading heterogeneous catalysts for broad applications.

Layered double hydroxide/carbonitride heterostructure with potent combination for highly efficient peroxymonosulfate activation.

Iron-based layered double hydroxides (LDHs) have drawn tremendous attention as a promising peroxymonosulfate (PMS) activators, but they still suffer from low efficiencies limited by electrostatic agglomeration and low electronic conductivity. Herein, a MgFeAl layered double hydroxide/carbonitride (LDH/CN) heterostructure was constructed via triggering the interlayer reaction of citric acid (CA) and urea. CA as a structure-directing agent regulated the interlayer anion of MgFeAl-LDH, which enabled an interfacial tuning in the process of coupling with CN. The obtained LDH/CN heterostructure, as an efficient PMS activator, achieved nearly 100% bisphenol A (BPA) removal rate in 10 min with high specific activity (0.146 L min-1·m-2). Electron paramagnetic resonance (EPR) tests, quenching experiments, electrochemical characterization and X-ray photoelectrons spectroscopy (XPS) tests were applied to clarify the mechanism of BPA degradation. The results unraveled that the activity of the catalyst originated from the heterostructure of LDH and CN with an efficient interfacial electron transfer, which promoted the fast generation of O2•- for rapid pollutant degradation. In addition, the catalyst exhibited excellent applicability in realistic wastewater. This work offered a rational strategy for forming a heterostructure catalyst with a fine interface engineering in actual environmental cleanup.

Fe3O4 nanoparticles encapsulated in boron nitride support via N-doped carbon layer as a peroxymonosulfate activator for pollutant degradation: Important role of metal boosted C-N sites.

Developing highly efficient and stable catalysts for peroxymonosulfate (PMS) based advanced oxidation processes (AOPs) are crucial in the field of environmental remediation. In this work, a facile encapsulated-precursor pyrolysis strategy was reported to prepare a competent PMS-activation catalyst, in which uniformly distributed Fe3O4 nanoparticles were firmly anchored on porous boron nitride (BN) nanosheets by N-doped carbon shell (NC layer). Taking advantage of strong metal-support interaction, the as-synthesized catalyst (BFA-500) could efficiently activate PMS to achieve 100% removal of 4-chlorophenol (4-CP) in 6 min, and the corresponding turnover frequency (TOF) value was 1-2 orders of magnitude higher than that of the benchmark homogeneous (Fe2+) and nanoparticle (Fe0 and Fe3O4) catalysts. Moreover, the well protected encapsulated structure of BFA-500 ensured the remarkable stability that could effectively resist the interference of complex water environment, including initial pH value, various inorganic ions and actual water, and its catalytic activity remained almost unchanged in 5 use-regeneration cycles. More importantly, the generation of O2•- and 1O2 radicals for the 4-CP removal in BFA-500/PMS system was ascribed to Fe3O4 boosted C-N sites containing pyridinic N, where electrons transferred from the embedded Fe3O4 nanoparticles to C-N sites to secure the PMS dissociation into reactive radicals. Overall, this work provided a promising way to design desired PMS-activation catalyst toward wastewater purification.

Enhanced sorption and reduction of Cr(VI) by the flowerlike nanocomposites combined with molybdenum disulphide and polypyrrole.

Developing high-performance adsorbent for hexavalent chromium (Cr(VI)) elimination presents an enticing prospect in environmental remediation. Herein, three-dimensional flowerlike nanospheres composed of molybdenum disulphide and polypyrrole (MoS2@PPy) were successfully prepared via a one-pot hydrothermal and subsequent carbothermal reduction process for the removal of Cr(VI). The effects of pH, adsorbent dosage, co-existing ions, initial Cr(VI) concentration and temperature were investigated systematically by batch experiments. Benefiting from the incorporation of MoS2, the obtained MoS2@PPy composites showed a dramatic increase of specific surface area (149.82 m2·g-1) and adsorption capacity (230.97 mg·g-1) when compared with the pure PPy nanoparticles. Based on the thermodynamics study and X-ray photoelectron spectroscopy analyses, the removal process of Cr(VI) was proved to be exothermic and spontaneous, and accessible under-coordinated Mo(IV) and pyrrolic N groups coupled with redox reactions were conducive to the efficient removal of Cr(VI). Attractively, the MoS2@PPy acted as the electron donor could also activate peroxymonosulphate for the efficient degradation of organic contaminants. These results suggested that the MoS2@PPy was promising in Cr(VI) elimination and other kinds of organic pollutants removal in wastewater.

Activation of peroxymonosulfate by MgCoAl layered double hydroxide: Potential enhancement effects of catalyst morphology and coexisting anions.

The morphology and specific surface area of layered double hydroxide (LDH) are of great significance for optimizing the application of LDH in sewage treatment. Herein, we present a study of the relation between the catalytic property and the morphology of LDH via activating peroxymonosulfate (PMS) for degradation of organic pollutants. The results demonstrated that LDH nanoscrolls possessed a superior performance for methylene blue (MB) degradation, which achieved almost 100% removal in 40 min and the calculated apparent rate constant was about 2.1, 4.5 and 11.5 times higher than that of LDH nanosheets, Co2+ and Co3O4, respectively. According to the results of X-ray photoelectrons spectroscopy (XPS) and electron paramagnetic resonance (EPR), 1O2 was confirmed to play a dominant role in the MB degradation, where the redox cycle of Co3+/Co2+ provided the impetus for the reaction. Moreover, the pH and ion tolerance abilities of LDH nanoscrolls in PMS activating process were determined as well. Remarkably, CO32- and H2PO4- could even promote the generation of •OH and 1O2 to facilitate the progress of reaction. Overall, these findings in the study may provide more opportunities in the preparation of high-efficiency catalysts and give insight into the accelerated degradation of refractory contaminants with surrounding anions.

Construction of durable superhydrophilic activated carbon fibers based material for highly-efficient oil/water separation and aqueous contaminants degradation.

Developing filtering materials with high permeation flux and contaminant removal rate is of great importance for oily wastewater remediation. Herein, a robust three-dimensional (3D) activated carbon fibers (ACFs) based composite with uniformly grown layered double hydroxide (LDH) on the surface was successfully constructed through a feasible hydrothermal strategy. The LDH with a high surface energy and vertically aligned structure could provide superhydrophilicity to ACFs. Systematic investigation confirmed that the 3D material could overcome the size mismatch between the ACFs macropores and tiny emulsified droplets through the combination of size-sieving filtration on the surface and oil droplet coalescence in the fiber network. This process efficiently separated the intractable surfactant-stabilized oil-in-water emulsions with high permeation flux (up to 4.16 × 106 L m-2 h-1 bar-1). Notably, the LDH also had well-dispersed catalytic active sites, which could initiate advanced oxidation processes (AOPs) to efficiently eliminate various types of water-soluble organic pollutants (e.g., pharmaceuticals, phenolic compounds and organic dyes). The resulting modified ACFs exhibited exceptional removal rates for both oil and organic pollutants in the complex sewage during the continuous filtration process. These versatile abilities integrated with the facile preparation method reported herein provide outstanding prospects for the large-scale treatment of oily wastewater.

Synergic fabrication of pembrolizumab loaded doxorubicin incorporating microbubbles delivery for ultrasound contrast agents mediated anti-proliferation and apoptosis.

This study evaluated pembrolizumab-conjugated, doxorubicin (DOX)-loaded microbubbles (PDMs) in combination with ultrasound (US) as molecular imaging agents for early diagnosis of B cell lymphomas, and as a targeted drug delivery system. Pembrolizumab, a monoclonal CD20 antibody, was attached to the surfaces of DOX-loaded microbubbles. PDM binding to B cell lymphoma cells was assessed using immunofluorescence. The cytotoxic effects of PDMs in combination with ultrasound (PDMs + US) were evaluated in vitro in CD20+ and CD20- cell lines, and its antitumor activities were assessed in Raji (CD20+) and Jurkat (CD20-) lymphoma cell-grafted mice. PDMs specifically bound to CD20+ cells in vitro and in vivo. Contrast enhancement was monitored in vivo via US. PDM peak intensities and contrast enhancement durations were higher in Raji than in Jurkat cell-grafted mice (p < 0.05). PDMs + US treatment resulted in improved antitumor effects and reduced systemic toxicity in Raji cell-grafted mice compared with other treatments (p < .05). Our results showed that PDMs + US enhanced tumor targeting, reduced systemic toxicity, and inhibited CD20+ B cell lymphoma growth in vivo. Targeted PDMs could be employed as US molecular imaging agents for early diagnosis, and are an effective targeted drug delivery system in combination with US for CD20+ B cell malignancy treatment.

Well-dispersed iron and nitrogen co-doped hollow carbon microsphere anchoring by g-C3N4 for efficient peroxymonosulfate activation.

Developing single-atom Fenton-like catalysts with the maximum utilization of active sites present an attractive potential in environmental remediation. Herein, the single-atom Fe and N co-doped hollow carbon microsphere loaded g-C3N4 catalyst (HFeNC-g-C3N4) was prepared by an innovative cascade anchoring strategy using polystyrene as the hard template, iron phthalocyanine, polydopamine and urea as the Fe, N and C precursor, in which the in-situ generated g-C3N4 could not only effectively anchor Fe atom to create the well-dispersed Fe-Nx active sites, but also accelerate the electron transfer in peroxymonosulfate (PMS) activation. Taking advantages of such sequential protecting strategy, the as-synthesized HFeNC-g-C3N4 catalyst with single-atom Fe-Nx active sites, verified by XRD, XPS and HAADF-STEM, could work as an efficient Fenton-like catalyst for PMS activation, which achieved almost 100% removal of 4-chlorophenol (4-CP) in 5 min with the turnover frequency calculated to be 34.6 times higher than that of the homogeneous Fe2+ catalyst. The mechanism of O2•- dominated radical combined with nonradical 1O2 pathway was confirmed by quenching experiments and ESR analysis, which might be interrelated to the improvement of pH adaptability and interference immunity of HFeNC-g-C3N4/PMS system. Overall, the present findings provided an innovation strategy for the synthesis of excellent single-atom Fe based catalyst in wastewater purification.

Nitrogen-doped porous carbon encapsulating iron nanoparticles for enhanced sulfathiazole removal via peroxymonosulfate activation.

Developing novel catalyst with both high efficiency and stability presents an enticing prospect for peroxymonosulfate (PMS) activation. In this paper, nitrogen-doped porous carbon encapsulating iron nanoparticles (CN-Fe) was fabricated by a facile carbothermal reduction process using polyaniline (PANI) and α-Fe2O3 as the precursors. The stubborn antibiotics, sulfathiazole (STZ), was employed as a target pollutant, demonstrating that CN-Fe coupled with PMS could achieve 96% removal efficiency and even 57% mineralization rate of STZ within 40 min. More importantly, the rate constant of CN-Fe was calculated to be 0.07665 min-1, which was 6 times higher than that of the commercial α-Fe2O3 catalyst. Furthermore, CN-Fe also presented a favorable catalytic performance for removing other organic pollutants including phenolic compounds and organic dyes. Interestingly, the catalytic activity of the used CN-Fe catalyst could be regenerated after thermal treatment (600 °C) and the as-synthesized CN-Fe catalyst exhibited excellent long-term stability with almost no loss of activity after storage for three months. The catalytic mechanism in the CN-Fe/PMS system was elucidated by electron paramagnetic resonance (EPR), linear sweep voltammetry (LSV), radical and electron trapping tests, which confirmed that sulfate radicals (SO4-), hydroxyl radicals (OH), superoxide radicals (O2-) and singlet oxygen (1O2) were generated in the oxidation process with the assistance of electron transfer between PMS and catalyst. To our knowledge, this was the first attempt for the application of PANI-derived CN-Fe hybrid materials as PMS activators and the findings would provide a simple and promising strategy to fabricate highly efficient and environment-benign catalysts for wastewater remediation.