Topology-Driven Coulomb Drag in van der Waals Heterostructure with Broken Inversion Symmetry.

As Coulomb drag near charge neutrality (CN) is driven by fluctuations or inhomogeneity in charge density, the topology should play an extremely important role. Interlinking Coulomb drag and topology could reveal how the system's nontrivial topology influences the electron-electron interactions at the quantum level. However, such an aspect is overlooked as most studies focus on symmetric drag systems without topology. To understand this topological aspect, we need to study Coulomb drag in an asymmetric system with a broken inversion symmetry and strong spin-orbit coupling (SOC). Here we experimentally demonstrate the energy-driven Coulomb drag in an asymmetric van der Waals heterostructure composed of black phosphorus and rhenium disulfide characterized by broken inversion symmetry. Temperature-dependent transport measurements near CN provide compelling evidence for the energy-driven Coulomb drag due to electron-hole coupling that is energetically favored in a broken-gap heterojunction, as confirmed by Hall coefficient sign reversal with temperature. Moreover, contrary to the symmetric devices, our results exhibit magnetic-field-free, i.e., topology-driven, Hall drag, revealing an intrinsic coupling between energy and charge modes. This is the manifestation of nonzero Berry curvature, akin to a magnetic field in momentum space, in a Rashba system, which arises from the SOC and broken inversion symmetry of the heterostructure.

Efficient cadmium removal from industrial wastewater generated from smelter using chemical precipitation and oxidation assistance.

The effective treatment of cadmium (Cd) in smelting wastewater is of great industrial importance. This study investigates the efficient removal of Cd from real industrial smelting wastewater via chemical precipitation using a series of experiments. In particular, the effects of different precipitants, agitation conditions, and the addition of NaOCl on Cd removal and pH variation are investigated. CaO (3.75 g/L), NaOH (3.50 g/L), and Ca(OH)2 (3.75 g/L) are found to be effective in elevating the wastewater pH and achieving high Cd removal rates (>99.9%), while the use of NaOH as a precipitant maintains a high Cd removal rate even at low agitation intensities. The properties of the produced sludge and supernatant are also determined using moisture content, particle size, and sludge leaching analyses due to the importance of economic and environmental sustainability in filtration, dewatering, and waste disposal processes. In addition, the addition of 2% NaOCl is tested, revealing that it can improve the Cd removal efficiency of Ca(OH)2, thus potentially reducing processing costs and enhancing the environmental benefits. Overall, these findings offer valuable insights into the removal of Cd from smelting wastewater, with potential implications for both environmental sustainability and economic viability. PRACTITIONER POINTS: CaO, NaOH, and Ca(OH)2 effectively remove Cd (>99.9%) from smelting wastewater. The use of NaOH leads to high Cd removal rates even at low agitation speeds. Adding 2% NaOCl can reduce the Ca(OH)2 dose for more economical Cd removal.

Covalently Bonded Heterostructures with Mixed-Dimensional Carbons for Suppressing Mechanochemical Wear of Diamond under Heavy Loads.

Diamond is widely acknowledged as the hardest naturally occurring material. Nevertheless, when exposed to friction against ferrous metals, it is prone to graphitization or amorphization, which limits the utilization of its extremely high hardness and wear resistance. These issues have persisted for decades without an effective solution. Here, we report that a covalently bonded heterostructure with mixed-dimensional carbons as a high-performance solid lubricant could effectively reduce diamond surface friction and mechanochemical wear with excellent load capacity and durability. When subjected to dry friction and heavy loads (20-150 N), the heterostructure exhibited a notable improvement over pristine diamond with reduced friction coefficients and relative wear rates by 22-45 and 67-91%, respectively. Especially under a 20 N load, the relative wear rate was an order of magnitude lower than that of pristine diamond. Additionally, experiments and molecular dynamics simulations revealed that the heterostructure integrated the outstanding properties of diamond (three-dimensional (3D)), nanographite (3D), and graphene (two-dimensional (2D)), resulting in improved lubrication and antiwear performance that could not be achieved by the individual carbon materials. The findings in this work will be beneficial to overcome the ferrous metal forbidden zone of diamond and are expected to expand the applications of engineered diamond surfaces and graphite/graphene in tribology, mechanics, and electronic fields.

Feasibility study of Aesculus turbinata fruit shell-derived biochar for ammonia removal in wastewater and its subsequent use as nitrogen fertilizer.

In the face of increasing nitrogen demand for crop cultivation driven by population growth, this study presents a sustainable solution to address both the heightened demand and the energy-intensive process of nitrogen removal from wastewater. Our approach involves the removal of nitrogen from wastewater and its subsequent return to the soil as a fertilizer. Using biochar derived from Aesculus turbinata fruit shells (ATFS), a by-product of post-medical use, we investigated the effect of pyrolysis temperature on the NH4-N adsorption capacity of ATFS biochar (ATFS-BC). Notably, the ATFS-BC pyrolyzed at 300 °C (ATFS-BC300) exhibited the highest NH4-N adsorption capacity of 15.61 mg/g. The superior performance of ATFS-BC300 was attributed to its higher number of oxygen functional groups and more negatively charged surface, which contributed to the enhanced NH4-N adsorption. The removal of NH4-N by ATFS-BC300 involved both physical diffusion and chemisorption, with NH4-N forming a robust multilayer adsorption on the biochar. Alkaline conditions favored NH4-N adsorption by ATFS-BC300; however, the presence of trivalent and divalent ions hindered this process. Rice plants were cultivated to assess the potential of NH4-N adsorbed ATFS-BC300 (NH4-ATFS-BC300) as a nitrogen fertilizer. Remarkably, medium doses of NH4-ATFS-BC300 (594.5 kg/ha) exhibited key agronomic traits similar to those of the commercial nitrogen fertilizer in rice seedlings. Furthermore, high doses of NH4-ATFS-BC300 demonstrated superior agronomic traits compared to the commercial fertilizer. This study establishes the viability of utilizing ATFS-BC300 as a dual-purpose solution for wastewater treatment and nitrogen fertilizer supply, presenting a promising avenue for addressing environmental challenges.

Link between T-Linear Resistivity and Quantum Criticality in Ambipolar Black Phosphorus.

The interplay between strong Coulomb interactions and kinetic energy leads to intricate many-body competing ground states owing to quantum fluctuations in 2D electron and hole gases. However, the simultaneous observation of quantum critical phenomena in both electron and hole regimes remains elusive. Here, we utilize anisotropic black phosphorus (BP) to show density-driven metal-insulator transition with a critical conductance ∼e2/h which highlights the significant role of quantum fluctuations in both hole and electron regimes. We observe a T-linear resistivity from the deep metallic phase to the metal-insulator boundary at moderate temperatures, while it turns to Fermi liquid behavior in the deep metallic phase at low temperatures in both regimes. An analysis of the resistivity suggests that disorder-dominated transport leads to T-linear behavior in the hole regime, while in the electron regime, the T-linear resistivity results from strong Coulomb interactions, suggestive of strange-metal behavior. Successful scaling collapse of the resistivity in the T-linear region demonstrates the link between quantum criticality and the T-linear resistivity in both regimes. Our study provides compelling evidence that ambipolar BP could serve as an exciting testbed for investigating exotic states and quantum critical phenomena in hole and electron regimes of 2D semiconductors.

Algae development in rivers with artificially constructed weirs: Dominant influence of discharge over temperature.

Algal blooms contribute to water quality degradation, unpleasant odors, taste issues, and the presence of harmful substances in artificially constructed weirs. Mitigating these adverse effects through effective algal bloom management requires identifying the contributing factors and predicting algal concentrations. This study focused on the upstream region of the Seungchon Weir in Korea, which is characterized by elevated levels of total nitrogen and phosphorus due to a significant influx of water from a sewage treatment plant. We employed four distinct machine learning models to predict chlorophyll-a (Chl-a) concentrations and identified the influential variables linked to local algal bloom events. The gradient boosting model enabled an in-depth exploration of the intricate relationships between algal occurrence and water quality parameters, enabling accurate identification of the causal factors. The models identified the discharge flow rate (D-Flow) and water temperature as the primary determinants of Chl-a levels, with feature importance values of 0.236 and 0.212, respectively. Enhanced model precision was achieved by utilizing daily average D-Flow values, with model accuracy and significance of the D-Flow amplifying as the temporal span of daily averaging increased. Elevated Chl-a concentrations correlated with diminished D-Flow and temperature, highlighting the pivotal role of D-Flow in regulating Chl-a concentration. This trend can be attributed to the constrained discharge of the Seungchon Weir during winter. Calculating the requisite D-Flow to maintain a desirable Chl-a concentration of up to 20 mg/m3 across varying temperatures revealed an escalating demand for D-Flow with rising temperatures. Specific D-Flow ranges, corresponding to each season and temperature condition, were identified as particularly influential on Chl-a concentration. Thus, optimizing Chl-a reduction can be achieved by strategically increasing D-Flow within these specified ranges for each season and temperature variation. This study highlights the importance of maintaining sufficient D-Flow levels to mitigate algal proliferation within river systems featuring weirs.

Graphitic-carbon-nitride-hydrophilicity-dependent photocatalytic degradation of antibiotics with different log Kow.

The surface hydrophilicity of a photocatalyst is an important factor that directly influences its interactions with organic pollutants and significantly impacts its degradation. In this study, we investigated the impact of increased hydrophilicity of g-C3N4 (CN) by alkaline solvothermal treatment on the degradations of three antibiotics (oxytetracycline (OTC), oxolinic acid (OA), and sulfamethoxazole (SMX)) with different log Kow values. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and Fourier-transform infrared (FT-IR) spectroscopy showed no significant differences in the morphology, crystalline structure, and surface functional groups of CN after alkaline solvothermal treatment (Nv-HPCN). However, contact angle analysis revealed that Nv-HPCN (31.8°) was more hydrophilic than CN (61.1°). To assess the hydrophilicity of the antibiotics, the log Kow values of SMX (0.77), OA (0.43), and OTC (-0.34) were measured. Nv-HPCN showed faster OTC degradation than CN, whereas the opposite pattern was observed for the degradation of OA. Scavenger tests showed that O2•- and h+ mainly contributed to the degradation of these antibiotics. Furthermore, the influences of NOM and coexisting anions on antibiotic degradation were investigated. This study thus offers perspectives on the impact of surface hydrophilicity of photocatalysts on the degradation of antibiotics.

Direct Observation of Room-Temperature Magnetic Skyrmion Motion Driven by Ultra-Low Current Density in Van Der Waals Ferromagnets.

The recent discovery of room-temperature ferromagnetism in 2D van der Waals (vdW) materials, such as Fe3GaTe2 (FGaT), has garnered significant interest in offering a robust platform for 2D spintronic applications. Various fundamental operations essential for the realization of 2D spintronics devices are experimentally confirmed using these materials at room temperature, such as current-induced magnetization switching or tunneling magnetoresistance. Nevertheless, the potential applications of magnetic skyrmions in FGaT systems at room temperature remain unexplored. In this work, the current-induced generation of magnetic skyrmions in FGaT flakes employing high-resolution magnetic transmission soft X-ray microscopy is introduced, supported by a feasible mechanism based on thermal effects. Furthermore, direct observation of the current-induced magnetic skyrmion motion at room temperature in FGaT flakes is presented with ultra-low threshold current density. This work highlights the potential of FGaT as a foundation for room-temperature-operating 2D skyrmion device applications.

Pulsed-Mode Metalorganic Vapor-Phase Epitaxy of GaN on Graphene-Coated c-Sapphire for Freestanding GaN Thin Films.

We report the growth of high-quality GaN epitaxial thin films on graphene-coated c-sapphire substrates using pulsed-mode metalorganic vapor-phase epitaxy, together with the fabrication of freestanding GaN films by simple mechanical exfoliation for transferable light-emitting diodes (LEDs). High-quality GaN films grown on the graphene-coated sapphire substrates were easily lifted off by using thermal release tape and transferred onto foreign substrates. Furthermore, we revealed that the pulsed operation of ammonia flow during GaN growth was a critical factor for the fabrication of high-quality freestanding GaN films. These films, exhibiting excellent single crystallinity, were utilized to fabricate transferable GaN LEDs by heteroepitaxially growing InxGa1-xN/GaN multiple quantum wells and a p-GaN layer on the GaN films, showing their potential application in advanced optoelectronic devices.

Single-crystalline GaN microdisk arrays grown on graphene for flexible micro-LED application.

We report the growth of single-crystalline GaN microdisk arrays on graphene and their application in flexible light-emitting diodes (LEDs). Graphene layers were directly grown onc-sapphire substrates using chemical vapor deposition and employed as substrates for GaN growth. Position-controlled GaN microdisks were laterally overgrown on the graphene layers with a micro-patterned SiO2mask using metal-organic vapor-phase epitaxy. The as-grown GaN microdisks exhibited excellent single crystallinity with a uniform in-plane orientation. Furthermore, we fabricated flexible micro-LEDs by achieving heteroepitaxial growth ofn-GaN, InxGa1-xN/GaN multiple quantum wells, andp-GaN layers on graphene-coated sapphire substrates. The GaN micro-LED arrays were successfully transferred onto bendable substrates and displayed strong blue light emission under room illumination, demonstrating their potential for integration into flexible optoelectronic devices.

Exploring the viability of a floating photocatalyst in a continuous stirred tank reactor system for continuous water treatment.

The use of photocatalysts in continuous stirred tank reactor (CSTR) systems allows for efficient and continuous water treatment, thus meeting the demand for scalable technology and comparative data in large-scale implementations. Hence, this study aims to explore the feasibility of a floating photocatalyst within a CSTR system for continuous water treatment. An expanded polystyrene (EPS)-TiO2 composite was synthesized following established methodologies, and their efficacy in removing the water pollutant methylene blue (MB) was compared for both batch and CSTR systems. A nonlinear first-order model was identified as the most suitable approach to accurately simulate MB degradation under experimental conditions, and the calculated pseudo-first-order degradation rate constant (k') for the CSTR system (0.0126-0.0172/min) was found to be superior to that observed for the batch system (0.0113/min). In addition, an increase in the flow rate reduced the retention time, leading to lower MB removal efficiency for the CSTR system. In addition, the EPS-TiO2/UV system with a CSTR configuration was found to efficiently use light and energy based on the calculated quantum yield (Φ = 2.86 × 10-4) and electrical energy per order (EEO = 857.46 kWh/m3/order). The findings of this study contribute to the development of sustainable and efficient water treatment strategies, offering valuable insight into the implementation of practical water treatment processes.

Use of thermally activated Fenton sludge for Cd removal in zinc smelter wastewater: Mechanism and feasibility of Cd removal.

Fenton sludge is a byproduct of the Fenton process that contains large amounts of Fe and Ca. Because of the secondary contamination generated during the disposal of this byproduct, ecofriendly treatment methods are needed. In this study, we used Fenton sludge to remove the Cd discharged from a zinc smelter factory, using thermal activation to enhance the Cd adsorption capacity. Among the various temperatures considered (300-900 °C), the Fenton sludge that was thermally activated at 900 °C (TA-FS-900) adsorbed the highest amount of Cd because of its high specific surface area and high Fe content. Cd was adsorbed onto TA-FS-900 via complexation with C-OH, C-COOH, FeO-, and FeOH and cation exchange with Ca2+. The maximum adsorption of TA-FS-900 was 260.2 mg/g, indicating that TA-FS-900 is an efficient adsorbent, comparable to those reported in the literature. The initial Cd concentration in the zinc smelter wastewater discharged was 105.7 mg/L, 98.4% of which was removed by applying TA-FS-900, suggesting the applicability of TA-FS-900 for real wastewater containing high concentrations of various cations and anions. The leaching of heavy metals from TA-FS-900 was within the EPA standard limits. We concluded that the environmental impact of Fenton sludge disposal can be reduced, and the use of Fenton sludge can add value to the treatment of industrial wastewater in terms of the circular economy and environment.

Giant coercivity enhancement in a room-temperature van der Waals magnet through substitutional metal-doping.

FexGeTe2 (x = 3, 4, and 5) systems, two-dimensional (2D) van der Waals (vdW) ferromagnetic (FM) metals with high Curie temperatures (TC), have been intensively studied to realize all-2D spintronic devices. Recently, an intrinsic FM material Fe3GaTe2 with high TC (350-380 K) has been reported. As substitutional doping changes the magnetic properties of vdW magnets, it can be a powerful means for engineering the properties of magnetic materials. Here, the coercive field (Hc) is substantially enhanced by substituting Ni for Fe in (Fe1-xNix)3GaTe2 crystals. The introduction of a Ni dopant with x = 0.03 can enhance the value of Hc up to ∼200% while maintaining the FM state at room temperature. As the doping level increases, TC decreases, whereas Hc increases up to 7 kOe at x = 0.12, which is the highest Hc reported so far. The FM characteristic is almost suppressed at x = 0.68 and a spin glass state appears. The enhancement of Hc resulting from Ni doping can be attributed to domain pinning induced by substitutional Ni atoms, as evidenced by the decrease in magnetic anisotropy energy in the crystals upon Ni doping. Our findings provide a highly effective way to control the Hc of the 2D vdW FM metal Fe3GaTe2 for the realization of Fe3GaTe2 based room-temperature operating spintronic devices.

Cycling of phosphorus from wastewater to fertilizer using wood ash after energy production.

Quercus wood was used for thermal energy production, and wood bottom ash (WDBA) was used as a medium for water purification and soil fertilizer in accordance with the recently proposed food-water-energy nexus concept. The wood contained a gross calorific value of 14.83 MJ kg-1, and the gas generated during thermal energy production has the advantage of not requiring a desulfurization unit due to its low sulfur content. Wood-fired boilers emit less CO2 and SOX than coal boilers. The WDBA had a Ca content of 66.0%, and Ca existed in the forms of CaCO3 and Ca(OH)2. WDBA absorbed P by reacting with Ca in the form of Ca5(PO4)3OH. Kinetic and isotherm models revealed that the results of the experimental work were in good agreement with the pseudo-second-order and Langmuir models, respectively. The maximum P adsorption capacity of WDBA was 76.8 mg g-1, and 6.67 g L-1 of WDBA dose could completely remove P in water. The toxic units of WDBA tested using Daphnia magna were 6.1, and P adsorbed WDBA (P-WDBA) showed no toxicity. P-WDBA was used as an alternative P fertilizer for rice growth. P-WDBA application resulted in significantly greater rice growth in terms of all agronomic values compared to N and K treatments without P. This study proposed the utilization of WDBA, obtained from thermal energy production, to remove P from wastewater and replenish P in the soil for rice growth.

Value-added application of cattle manure bottom ash for phosphorus recovery from water and replenishment in soil.

This study addresses ways to circulate the flow of phosphorus (P) from water to soil to improve water quality and provide a sustainable supply of P into soil. Here, bottom ash (BA_CCM), the byproduct of the combustion of cattle manure, which is performed for obtaining energy, was used to remove P in wastewater. Next, the P-captured BA_CCM was used as P fertilizer for rice growth. BA_CCM was primarily composed of Ca (49.4%), C (24.0%), and P (9.9%), and the crystalline phases of Ca were calcium carbonate (CaCO3) and hydroxyapatite (Ca5(PO4)3OH). The mechanism of P removal by BA_CCM involves the formation of hydroxyapatite by reacting Ca2+ with PO43-. A reaction time of 3 h was required to achieve P adsorption to BA_CCM, and the maximum P adsorption capacity of BA_CCM was 45.46 mg/g. The increase in solution pH reduced P adsorption. However, at pH > 5, the P adsorption amount was maintained regardless of the pH increase. The presence of 10 mM SO42- and CO32- reduced P adsorption by 28.4% and 21.5%, respectively, and the impact of the presence of Cl- and NO3- was less than 10%. The feasibility of BA_CCM was tested using real wastewater, and 3.33 g/L of BA_CCM dose achieved a P removal ratio of 99.8% and a residual concentration of <0.02 mg/L. The toxicity unit of BA_CCM determined for Daphnia magna (D. magna) was 5.1; however, the BA_CCM after P adsorption (P-BA_CCM) did not show any toxicity to D. magna. BA_CCM after P adsorption was used as an alternative to commercial P fertilizer. Rice fertilized with a medium level of P-BA_CCM showed better agronomic values for most agronomic traits, except root length, than that seen with the commercial P fertilizer. This study suggests that BA_CCM can be used as a value-added product to address environmental issues.

Wafer-Scale Epitaxial Growth of an Atomically Thin Single-Crystal Insulator as a Substrate of Two-Dimensional Material Field-Effect Transistors.

As the electron mobility of two-dimensional (2D) materials is dependent on an insulating substrate, the nonuniform surface charge and morphology of silicon dioxide (SiO2) layers degrade the electron mobility of 2D materials. Here, we demonstrate that an atomically thin single-crystal insulating layer of silicon oxynitride (SiON) can be grown epitaxially on a SiC wafer at a wafer scale and find that the electron mobility of graphene field-effect transistors on the SiON layer is 1.5 times higher than that of graphene field-effect transistors on typical SiO2 films. Microscale and nanoscale void defects caused by heterostructure growth were eliminated for the wafer-scale growth of the single-crystal SiON layer. The single-crystal SiON layer can be grown on a SiC wafer with a single thermal process. This simple fabrication process, compatible with commercial semiconductor fabrication processes, makes the layer an excellent replacement for the SiO2/Si wafer.

Facile synthesis of N vacancy g-C3N4 using Mg-induced defect on the amine groups for enhanced photocatalytic •OH generation.

Photocatalysis offers opportunities to degrade recalcitrant organic pollutants without adding treatment chemicals. Nitrogen (N) vacancy is an effective point-defect engineering strategy to mitigate electron-hole recombination and facilitate hydroxyl radical (•OH) production via superoxide radical (O2•-) generation during photocatalytic application of graphitic carbon nitride (g-C3N4). Here, we report a novel strategy for fabrication of N-vacancy-rich g-C3N4 (NvrCN) via post-solvothermal treatment of Mg-doped g-C3N4. The addition of the Mg precursor during the polycondensation of urea created abundant amine sites in the g-C3N4 framework, which facilitates formation of N vacancies during post-solvothermal treatment. Elemental analysis and electron paramagnetic resonance spectra confirmed a higher abundance of N vacancies in the resultant NvrCN. Further optical and electronic analyses revealed the beneficial role of N vacancies in light-harvesting capacity, electron-hole separation, and charge transfer. N vacancies also provide specific reaction centers for O2 molecules, promoting oxygen reduction reaction (ORR). Therefore, •OH generation increased via enhanced formation of H2O2 under visible light irradiation, and NvrCN photocatalytically degraded oxytetracycline 4-fold faster with degradation rate constant of 1.85 × 10-2 min-1 (light intensity = 1.03 mW/cm2, catalyst concentration = 0.6 g/L, oxytetracycline concentration = 20 mg/L) than pristine g-C3N4. Overall, this study provides a facile method for synthesizing N-vacancy-rich g-C3N4 and elucidates the role of the defect structure in enhancing the photocatalytic activity of g-C3N4.

Effect of water filtration infrared-A (wIRA) sauna on inorganic ions excreted through sweat from the human body.

Sweat discharged as a result of exposure to sauna plays an important role in removing inorganic ions accumulated in the body, including heavy metals. In this study, inorganic ions (toxic and nutrient elements) excreted in the form of sweat from the body using a water-filtered infrared-A (wIRA) sauna were determined using inductively coupled plasma sector field mass spectrometry. The analyzed elements included eight toxic elements (Al, As, Be, Cd, Ni, Pb, Ti, and Hg) and 10 nutrient elements (Ca, Co, Cr, Cu, Fe, Mg, Mn, Se, V, and Zn), and their correlations were determined. Analysis of the sweat obtained from 22 people using the wIRA sauna showed a higher inorganic ion concentration than that obtained from conventional activities, such as exercise or the use of wet sauna, and the concentration of toxic elements in sweat was higher in females than in males. Correlation analysis of the ions revealed a correlation between the discharge of toxic elements, such as As, Be, Cd, and Ni, and discharge of Se and V, and Ni was only correlated with Mn. This study provides fundamental information on nutritional element supplementation when using wIRA sauna for detoxification.

Efficient removal of dyes from aqueous solutions using short-length bimodal mesoporous carbon adsorbents.

Ordered mesoporous carbons (OMCs) with controlled mesopore lengths and volumes were synthesized and investigated to remove the model dye methylene blue (MB) from aqueous solutions. The pore size, specific surface area, pore volume, and pore length of OMCs (CMK-3, sCMK-3, and sCMK-5) were analyzed and benchmarked against commercial activated carbon (AC). CMK-3 and sCMK-3 had narrow pore size distributions (PSDs) centered at ∼4.4 nm, whereas the PSD of sCMK-5 was bimodal, derived from the same pores as CMK-3 (∼4.4 nm) and the inner diameter of the carbon nanotubes (∼5.8 nm). The pore length decreased from 743 nm for CMK-3 to 173 nm for sCMK-3 and 169 nm for sCMK-5, facilitating the MB accessibility and efficient utilization of internal mesopores. The MB adsorption on the prepared adsorbents was well described by a pseudo-second-order kinetic model (R2 > 0.999), and the initial adsorption rate (h) on sCMK-5 was 34.07-fold faster than that on commercial AC. The Langmuir model adequately explained the equilibrium adsorption data, and the increase in the Langmuir maximal adsorption capacity (qm) of the OMCs was proportional to the specific surface area. The MB adsorption on sCMK-5 was endothermic and spontaneous, and proceeded primarily through physical adsorption as well as chemisorption reacting with oxygen atoms in hydroxyl groups. The prepared adsorbents were also suitable for polishing textile wastewater containing color-causing substances along with the background organic matter. These OMCs are promising for treating wastewater as efficient adsorbents for large molecular pollutants such as dyes.

Photoluminescence Path Bifurcations by Spin Flip in Two-Dimensional CrPS4.

Ultrathin layered crystals of coordinated chromium(III) are promising not only as two-dimensional (2D) magnets but also as 2D near-infrared (NIR) emitters due to long-range spin correlation and efficient transition between high- and low-spin excited states of Cr3+ ions. In this study, we report on the dual-band NIR photoluminescence (PL) of CrPS4 and show that its excitonic emission bifurcates into fluorescence and phosphorescence depending on thickness, temperature, and defect density. In addition to the spectral branching, the biexponential decay of PL transients, also affected by the three factors, could be well described within a three-level kinetic model for Cr(III). In essence, the PL bifurcations are governed by activated reverse intersystem crossing from the low- to high-spin states, and the transition barrier becomes lower for thinner 2D samples because of surface-localized defects. Our findings can be generalized to 2D solids of coordinated metals and will be valuable in realizing groundbreaking magneto-optic functions and devices.