Polydopamine mediated modification of manganese oxide on melamine sponge for photothermocatalysis of gaseous formaldehyde

Biomass-activated carbon-based superhydrophobic sponge with photothermal properties for adsorptive separation of waste oil

The increasing discharge of oily wastewater from life poses a serious threat to the ecological environment and human health. To develop green, efficient, and low-cost materials for oil-water separation, a superhydrophobic photothermal oil-absorbing sponge (CAC-PDA@MF) was prepared by using nanoscale coconut shell activated carbon (CAC) loaded on a melamine sponge in this study. The sponge had excellent superhydrophobicity (WCA of 159.53°) due to the reduction of surface energy by grafting long-chain silanes. The adsorption capacity of the sponge was 69.04 g/g-158.27 g/g for a wide range of oils and organic solvents, and the sponge had excellent mechanical properties for multiple adsorption and recovery of oil. After 50 cycles of oil-water separation, its separation efficiency was maintained at over 98 %. In addition, the material had high acid, alkali, and salt resistance as well as excellent photothermal conversion properties. Its surface temperature rose rapidly to 100 °C and above, at a light intensity of 1.0 kW/m2. The material was capable of adsorbing and recovering high-viscosity oils that were solid or semi-solid at room temperature. Its versatility and commercial value made it a promising candidate for a wide range of applications.

NIR triggered polydopamine coated cerium dioxide nanozyme for ameliorating acute lung injury via enhanced ROS scavenging

Acute lung injury (ALI) is a life threatening disease in critically ill patients, and characterized by excessive reactive oxygen species (ROS) and inflammatory factors levels in the lung. Multiple evidences suggest that nanozyme with diversified catalytic capabilities plays a vital role in this fatal lung injury. At present, we developed a novel class of polydopamine (PDA) coated cerium dioxide (CeO2) nanozyme (Ce@P) that acts as the potent ROS scavenger for scavenging intracellular ROS and suppressing inflammatory responses against ALI. Herein, we aimed to identify that Ce@P combining with NIR irradiation could further strengthen its ROS scavenging capacity. Specifically, NIR triggered Ce@P exhibited the most potent antioxidant and anti-inflammatory behaviors in lipopolysaccharide (LPS) induced macrophages through decreasing the intracellular ROS levels, down-regulating the levels of TNF-α, IL-1β and IL-6, up-regulating the level of antioxidant cytokine (SOD-2), inducing M2 directional polarization (CD206 up-regulation), and increasing the expression level of HSP70. Besides, we performed intravenous (IV) injection of Ce@P in LPS induced ALI rat model, and found that it significantly accumulated in the lung tissue for 6 h after injection. It was also observed that Ce@P + NIR presented the superior behaviors of decreasing lung inflammation, alleviating diffuse alveolar damage, as well as promoting lung tissue repair. All in all, it has developed the strategy of using Ce@P combining with NIR irradiation for the synergistic enhanced treatment of ALI, which can serve as a promising therapeutic strategy for the clinical treatment of ROS derived diseases as well.

Enhanced toluene oxidation by photothermal synergetic catalysis on manganese oxide embedded with Pt single-atoms

The degradation of volatile organic compounds (VOCs) at low temperature remains a big challenge. Photothermal catalysis coupling the advantages of photocatalysis and thermocatalysis is promising to address this issue. However, there is still a long way to construct highly active catalysts and deeply understand the mechanism of photothermal catalysis. Herein, maganese oxide (MnO₂)catalysts embedded with Pt single-atoms (0.11 wt% Pt) have achieved greatly enhanced toluene conversion of 95%, far surpassing most supported Pt photothermal catalysts. The excellent catalytic activity has been disclosed to derive from the synergetic effect oflight-driven thermocatalysis and photocatalysis. The light-driven thermocatalysis predominates and the strong electron transfer from Pt single-atoms to MnO₂ improves the activity of surface lattice oxygen to boost the generation of benzoic acid and the mineralization of toluene. Meanwhile, in photocatalytic process, Pt single-atoms accelerate the generation of superoxide radicals (O₂^-), which facilitate the ring-opening and deep oxidation of toluene. This understanding on the photothermal synergetic mechanism will inspire the design of highly efficient catalysts for VOCs oxidation.

Magnetic, self-heating and superhydrophobic sponge for solar-driven high-viscosity oil-water separation

In this work, a novel oil-adsorption sponge with superhydrophobicity was fabricated using polymer-assisted electroless deposition and dip-coating techniques for depositing a rough polydopamine layer, magnetic particles, and low surface energy polydimethylsiloxane onto the surface of a sponge skeleton. The as-prepared superhydrophobic sponge (WCA > 150° and SA < 5°) exhibited rapid adsorption behavior, large adsorption capacity (up to 50.6 times its own dry weight or above 90% of its own volume), excellent durability (above 80% of the adsorption capacity after 80 recycles), and a self-cleaning property owing to sufficient open-cell pores and superelasticity provided by the melamine-formaldehyde host as well as the hierarchical roughness and convenient magnetic recovery enabled by the polymer-assisted electroless deposition approach. The pump-, gravity-, and solar-driven oil-water separation devices based on the fabricated cubic composites were also demonstrated, particularly the separation of high-viscosity oil-water mixtures via the solar-driven mode, demonstrating the broad prospects of such modified sponges in actual applications. This study provides a new avenue for rationally designing novel oil adsorption and separation materials.

Multi-energies assisted and all-weather recovery of crude oil by superhydrophobic melamine sponge

Efficient and safe recovery of high-viscosity marine crude oil spills is still a worldwide challenge. High-viscosity crude oil is difficult to be removed by traditional adsorbent materials. Although some recent developments in photothermal or electric-thermal oil-absorbing materials, the vertical heat transfer inside and the potential hazard of electrical leakage are difficult to be guaranteed. In order to overcome these problems, we polymerized dopamine (DA) in situ on the skeleton surface of the commercial melamine sponge (MS), and further coated the full-wavelength light-absorbing Fe₃O₄ NPs-Graphene (HF-G) on it to obtain the superhydrophobic sponge with excellent photothermal conversion effect, heat conductivity and magnetic heating capabilities (HF-G/PDA@MS). When the thickness of sponge is 5 mm, the HF-G/PDA@MS shows excellent vertical heat conductivity ability, and can absorb about 80 g/g. It also can be combined with an extra electric-heating device to achieve continuous heating to reduce the viscosity and recover crude oil at night or extreme weather. In addition, the temperature of HF-G/PDA@MS can reach about 40 °C by electromagnetic induction heater, indicating that we can use multiple energies-assisted modes to heat the HF-G/PDA@MS to. This work provides a promising solution and theoretical support for all-weather solving offshore crude oil spills pollution and recovery.

Electrostatic Polydopamine-Interface-Mediated (e-PIM) filters with tuned surface topography and electrical properties for efficient particle capture and ozone removal

Ambient particulate matter (PM) poses severe environmental health risks to the public globally, and efficient filtration technologies are urgently needed for air ventilation. In this contribution, to overcome the efficiency-resistance trade-off for fibrous filtration, we introduced an electrostatic polydopamine-interface-mediated (e-PIM) filter utilizing a combined effect of particle pre-charging and filter polarizing. After delineating the PM-fiber interactions in electrostatic filtration, we designed a composite fiber structure and fabricated the filters by a two-step dip-coating. The surface topography and electrical potential of the polyester (PET) coarse substrates were regulated by successively coating polydopamine (PDA) layers and manganese oxide clusters. By this means, an 8-mm-thick Mn-P @ P-100 filter possessed improved efficiency of 96.05%, 97.60%, and 99.14% for 0.3-0.5 µm, 0.5-1 µm, and 1-3 µm particles, the ultralow air resistance of 10.4 Pa at a filtration velocity of 0.5 m/s, and steady ozone removal property. Compared with the pristine PET substrates, the efficiency for 0.3-0.5 µm particles expanded 12 times. Compared with the pristine PET substrates, the efficiency for 0.3-0.5 µm particles expanded 12 times. We expect e-PIM filters and the filtration prototype will be potential candidates as effective and low-cost air cleaning devices for a sustainable and healthy environment.

A Three-Dimensional Melamine Sponge Modified with MnOx Mixed Graphitic Carbon Nitride for Photothermal Catalysis of Formaldehyde

Much attention has been paid to developing effective visible light catalytic technologies for VOC oxidation without requiring extra energy. In this paper, a series of sponge-based catalysts with rich three-dimensional porosity are synthesized by combining MnOx and graphitic carbon nitride (GCN) with commercial melamine sponges (MS) coated with polydopamine (PDA), demonstrating excellent photothermal catalytic performance for formaldehyde (HCHO). The three-dimensional porous framework of MS can provide a good surface for material modification and a reliable interface for gas-solid interaction. The grown layer of PDA framework not only increases the near-infrared wavelength absorption for improving the light-to-heat conversion of catalysts, but also brings excellent adhesion for the subsequent addition of MnO_X and GCN. The efficient formaldehyde oxidation is attributed to the sufficient oxygen vacancies generated by co-loaded MnO_X and GCN, which is conducive to the activation of more O²⁻ in the oxidation process. As the surface temperature of catalyst rapidly increases to its maximum value at ca. 115 °C under visible light irradiation, the HCHO concentration drops from 160 ppm to 46 ppm within 20 min. The reaction mechanism is certified as a classical Mars-van Krevelen mechanism based on the photo-induced thermal catalysis process.

Ultra-light 3D MnO2-agar network with high and longevous performance for catalytic formaldehyde oxidation

Under the background of indoor air formaldehyde decontamination, a freestanding ultra-light assembly was fabricated via ice-templating approach starting from MnO₂ nanoparticles and environmentally benign agar powder. The 3D composite of agar and MnO₂ (AM-3D) was comparatively studied with powdered counterparts (including pure MnO₂ and mixture of agar and MnO₂) and the 3D-structured agar for formaldehyde oxidation, and their physicochemical properties were examined with XRD, ATR, SEM, XPS, isothermal N₂ adsorption, ESR, Raman, CO-TPR and O₂-TPD. For the single test of formaldehyde oxidation, the AM-3D catalyst exhibited 62.0%-67.0% removal percentage for ~400 mg/m³ formaldehyde, which did not demonstrate significant advantage over the control samples. However, thanks to the porous 3D agar scaffold with large spatial volume that could promote a rapid gas-phase formaldehyde concentration reduction, and the strong interaction between the dispersed MnO₂ particles and agar substrate that could afford a large amount of reactive oxygen species to further oxidize the adsorbed formaldehyde, the AM-3D composite was a much better HCHO-to-CO₂ converter and possessed much more advantageous stability for repeated cycles of formaldehyde oxidation: even after ten cycles, there was still 41.7% of formaldehyde removed. Furthermore, the viable sunlight irradiation could easily restore the activity of the used AM-3D catalyst back to the level approaching that of the fresh one. Finally, reaction pathways were put forward via the infrared spectroscopic and ion chromatographic investigations on the surface intermediates of the spent materials.

Efficient Photothermal Elimination of Formaldehyde under Visible Light at Room Temperature by a MnOx-Modified Multi-Porous Carbon Sphere

Volatile organic compounds (VOCs) exert a serious impact on the environment and human health. The development of new technologies for the elimination of VOCs, especially those from non-industrial emission sources, such as indoor air pollution and other low-concentration VOCs exhaust gases, is essential for improving environmental quality and human health. In this study, a monolithic photothermocatalyst was prepared by stabilizing manganese oxide on multi-porous carbon spheres to facilitate the elimination of formaldehyde (HCHO). This catalyst exhibited excellent photothermal synergistic performance. Therefore, by harvesting only visible light, the catalyst could spontaneously heat up its surface to achieve a thermal catalytic oxidation state suitable for eliminating HCHO. We found that the surface temperature of the catalyst could reach to up 93.8 °C under visible light, achieving an 87.5% HCHO removal efficiency when the initial concentration of HCHO was 160 ppm. The microporous structure on the surface of the carbon spheres not only increased the specific surface area and loading capacity of manganese oxide but also increased their photothermal efficiency, allowing them to reach a temperature high enough for MnO_x to overcome the activation energy required for HCHO oxidation. The relevant catalyst characteristics were analyzed using XRD, measurement of BET surface area, scanning electron microscopy, HR-TEM, XPS, and DRS. Results obtained from a cyclic performance test indicated high stability and potential application of the MnO_x-modified multi-porous carbon sphere.

Unique insights into photocatalytic VOCs oxidation over WO3/carbon dots nanohybrids assisted by water activation and electron transfer at interfaces

Internal electric field (IEF) at heterojunction interfaces can separate photoexcited charge carriers and promote photocatalytic performance. Here we have modified WO₃ nanoplates with carbon dots (CDs) and constructed an interfacial IEF directing from CDs to WO₃ with assistance of their remarkably different work functions. Such electric field drove photoexcited electrons to transport towards CDs and retained photoexcited holes to stay at WO₃, achieving electron/hole spatial separation. H₂O preferred chemisorption on the five-coordinated W atoms of WO₃ with an elongated H-O bond and bent H-O-H angle, which allowed the activation of H₂O and favorable production of ·OH radicals. The WO₃/CDs (WC1) showed a superior photocatalytic activity for visible-light photooxidation of HCHO and CH₃COCH₃ with CO₂ production rate of 411 and 188 μmol g^-1 h^-1, respectively, outperforming most of WO₃-based photocatalysts. The enhanced photocatalytic performance correlated with the IEF-induced charge separation, favorable ·OH production and VOCs chemisorption. Our work confirms the role of CDs cocatalyst in the photocatalytic oxidation of VOCs, which will inspire enthusiasm to develop more advanced heterojunction photocatalysts involving carbon nanomaterials.

Application of silanized melamine sponges in matrix purification for rapid multi-residue analysis of veterinary drugs in eggs by UPLC-MS/MS

Fast and convenient matrix purification is an important prerequisite for high-throughput analysis of drug multiresidues in food. In this study, a silanized melamine sponge was prepared and first applied in the rapid determination of multiclass veterinary drugs in eggs by ultrahigh-performance liquid chromatography-tandem mass spectrometry. Within five seconds, fast, convenient and efficient matrix separation could be achieved through simple soaking and squeezing. Compared to other matrix adsorbents, the developed material demonstrated equivalent or better purification performance. Good validation results were obtained in terms of drug recoveries (61.5%~97.0%, relative standard deviation (RSD) ≤ 10.8%), and linearities (R² ≥ 0.999), as well as low limits of quantitation (0.3 ~ 10.9 μg·kg^-1) and detection (0.1 ~ 3.8 μg·kg^-1). By analyzing 52 egg samples, high concentrations of ofloxacin, trimethoprim, metronidazole, and dimetridazole were found at 542.9, 121.2, 66.1 and 58.0 μg·kg^-1, respectively. The silanized melamine sponge has shown its great potential for rapid analysis of multiclass residues in food safety.

Mussel-Inspired Ag NPs Immobilized on Melamine Sponge for Reduction of 4-Nitrophenol, Antibacterial Applications and Its Superhydrophobic Derivative for Oil-Water Separation

A functional material integrated with a variety of functions is highly desired in wastewater treatment. In this research, a mussel-inspired method of immobilizing silver nanoparticles on the skeleton of a melamine sponge is proposed and applied for water remediation. Ag NPs were reduced in situ and grown on a polydopamine-modified melamine sponge. The catalytic reduction of 4-nitrophenol (4-NP) in the presence of the obtained MS-PDA-Ag was evaluated, and the results demonstrated that the MS-PDA-Ag presented high catalytic reduction activity. In addition, the monolithic MS-PDA-Ag presents excellent reusability with no remarkable decrease in catalytic efficiency after multiple reuses. Owing to the immobilized Ag NPs, the MS-PDA-Ag can also effectively inhibit the growth of bacteria against both gram-positive and gram-negative species, making it possible for bacteria elimination in polluted water. To further explore the possibility of utilizing the MS-PDA-Ag for versatile applications, a superhydrophobic derivative (S-MS-PDA-Ag) was prepared by coating a low-surface-energy substance (octadecanethiol) on the surface of MS-PDA-Ag. The obtained S-MS-PDA-Ag presents the capacities of oil/organics adsorption and water repellence, which can separate the insoluble oil/organics from water. The melamine sponge immobilized with Ag NPs demonstrates prominent catalytic reduction of 4-NP, antibacterial activity and the superhydrophobic derivative presents the capacity of insoluble oil/organics separation from oil-water mixtures, exhibiting high potential in the remediation of polluted water.

Crystal-structure dependent reaction pathways in photocatalytic formaldehyde mineralization on BiPO4

Formaldehyde as significant environmental hazard in air seriously harm the environment and human health. Although photocatalysis has demonstrated the possibility for HCHO degradation, it has long been limited by unsatisfied degradation efficiency and the unclear reaction mechanism. Here, we confirm that surface atomic arrangement of BiPO₄ plays a critical role in photooxidation of HCHO via modulating the reaction pathway, offering 2.63 times enhancement of HCHO degradation efficiency. We dissect the processes in the photocatalytic reaction by DFT calculation, ROS monitoring, and in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) investigation. Specifically, we reveal that the controlling surface atomic arrangement could modulate adsorption model from single-point to bridging, and promote activation of small molecules. Concurrently, the active surface dependent on crystal structure facilitates the efficient transformation of intermediates (HCOOH*) (reducing energy barrier from 0.41 to -0.35 eV), producing final-product (H₂CO₃, ∆G = -0.35 eV) while suppressing toxic by-product (CO, ∆G = 0.32 eV), which contributes to the sustained deep mineralization of HCHO with enhancement by 61.4%. The findings are crucial as they provide crystal-structure related insights into the design of efficient catalysts for photocatalytic HCHO degradation. Ultimately, current molecular understanding should unlock the solar-driven catalytic pathways for other oxidation reactions.

Oxide-based composites: applications in thermo-photocatalysis

Recent progress on oxide-based thermo-photocatalytic composite systems. Role of plasmonic, defect-related, and thermal effects on the catalytic performance.