Monolayer Research Articles

Isotherm Study, Adsorption Kinetics and Thermodynamics of Lead Using Combination Adsorbent of Chitosan and Coffee Ground Activated Carbon

The presence of lead metal in water naturally due to its mobility can cause the nature of water to become toxic and endanger the environmental ecosystem because it bioaccumulates in the food chain. The purpose of this study was to study the maximum adsorption capacity through an isotherm model, to determine the rate of adsorption kinetics in the use of chitosan and coffee grounds adsorbents in reducing lead concentrations in industrial wastewater and to study its thermodynamic magnitude. The research method was carried out using experiments in the laboratory followed by quantitative data analysis to determine the isotherm model and adsorption kinetics. The results showed that the adsorption isotherm follows the Langmuir isotherm model with a correlation coefficient of 0.9970 with a maximum adsorption capacity of 1.0511 mg.g-1 which indicates that chemical adsorption occurs in the mono layer with a homogeneous distribution of adsorption sites with adsorption energy. constant and negligible interactions between lead metal molecules (adsorbate). Study of lead adsorption kinetics using chitosan-activated carbon coffee grounds following the Weber-Morris/intra-particle diffusion model with a correlation coefficient of 0.9920 with a diffusion rate of 76.512 g.mg-1.hour-1 indicating that intra-particle diffusion is the rate step limiting in the overall biosorption process. Negative ΔGo values ​​indicate that the adsorption reaction takes place spontaneously, ΔHo of 0.8130 indicates an endothermic reaction, and ΔSo of 4.1888 indicates an increase in the randomness of the adsorption process at the adsorbent interface and lead during adsorption.

Computer Simulation Study of Lithium and Oxygen Adsorption on Ruthenium Dioxide (110) Surface

Metal oxides are widely considered as excellent catalysts in lithium-air batteries to promote the production of stable discharge products and achieve superior electrochemical performance. The lithium–air (Li–air) battery is a metal–air electrochemical cell or battery chemistry that uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current. Despite various studies exploring the use of metal oxides as effective catalysis, the catalytic activity of ruthenium oxide (RuO2) towards lithium and oxygen ions is not fully understood. In this work, we investigate the adsorptions of lithium and oxygen on the RuO2 (110) surface using density functional theory (DFT) method. Due of the size of the supercell, and assuming that oxygen atoms occupy bulk-like positions around the surface metal atoms, only five values of (gamma) Γ are possible if constraint to a maximum of 1 monolayer (ML) of adatoms or vacancies: Γ= 0 surface is the stoichiometric surface, Γ= 1, 2 are the partially and totally oxidised surfaces, and Γ=-1, -2 are the partially and totally reduced surfaces. The addition of two oxygen atoms revealed the most stable adsorption energy is the mono-clear followed by bridging configuration. The lithium orientation between two bridging oxygen and in plane oxygen (bbi) orientation is much more stable, thus lithium generally prefers to adsorb where it will be triply coordinated to two bridging oxygen atoms and one in plane oxygen atom. Rutile RuO2 has been widely considered as an excellent catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in non-aqueous.

High Surface Area MoS2 and WS2 As Active HER Catalysts

The ever-increasing demand for clean energy necessitates a widespread adoption of clean energy carriers, namely green hydrogen. However, its production via electrolysis remains expensive. To achieve the needed drop in production cost, efficient catalyst materials are sought after to overcome the energy barrier of water splitting. Transition metal dichalcogenides (TMDCs) such as tungsten and molybdenum disulfide (WS2, MoS2) have been identified as promising catalysts because of their remarkably low Gibbs free energy for hydrogen adsorption.[1] The main challenge for these materials is the precise fabrication of continuous (mono)layers to achieve the desired functional properties.[2] Bottom-up material fabrication approaches like the vapor phase methods CVD and ALD offer several advantages. The use of chemical reactions of gas phase species allows precise thickness control, high quality films and allow large areas to be coated.This study focused on the fabrication of WS2 and MoS2 layers via metal organic chemical vapor deposition (MOCVD) and subsequent investigation of the properties of the resulting films in relation to the applied process conditions. Depositions were performed on FTO substrates and their thickness dependent capability to catalyze the electrochemical hydrogen evolution reaction (HER) were investigated in detail.For WS2 the selective growth of the semiconducting hexagonal phase with the targeted stoichiometry at a deposition temperature of 600°C was achieved (Fig 1 a). Similarly, in the case of MoS2, the hexagonal phase could be selectively deposited from 400 °C onwards and with pronounced crystallinity at 600°C (Fig. 1 b) which also showed the best stochiometric match and highest purity. The thin film characterization was further supported by Raman spectroscopy which serves as probe to verify the formed phase and layer number for 2D-materials. UV-VIS spectroscopy was employed to assess the semiconducting behavior allowing for band gap determination via the Tauc plot. Morphology and surface topography, especially interesting in the realm of HER catalysis, were assessed by SEM and HR-TEM showing the typical flakelike features known for these materials in their hexagonal phase (Fig 1 c). Electrochemical LSV experiments of WS2 in H2SO4 showed thickness dependence of the overpotentials which correlates with the flake density and the availability of vertical edge sites most active for HER (Fig 1 d). Similar studies for MoS2 are ongoing. These results are especially noteworthy as previous studies on WS2 deposited onto FTO have reported notably higher overpotentials.[3,4] This study demonstrates the potential of large area and high surface area TMDCs as effective HER electrocatalysts.[1] S. H. Noh, J. Hwang, J. Kang, M. H. Seo, D. Choi, B. Han, J. Mater. Chem. A 2018, 6, 20005–20014.[2] K. S. Novoselov, D. Jiang, A. K. Geim, et al. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 10451–10453.[3] J.-L. Wree, J.-P. Glauber, A. Devi, et al. J. Mater. Chem. C 2021, 9, 10254–10265.[4] J.-L. Wree, E. Ciftyurek, A. Devi, et al. Dalton Trans. 2020, 49, 13462–13474. Figure 1

Metastable atomic-ordered configurations for Al1/2Ga1/2N predicted by Monte-Carlo method based on first-principles calculations

Metastability of Al n /12Ga1−n/12N (n= 2–10: integer) with the 1–2 monolayer (ML) in-plane configuration towards the c [0001] direction has been demonstrated recently. To theoretically explain the existence of these metastable structures, relatively large calculation cells are needed. However, previous calculations were limited to the use of small calculation cell sizes to estimate the local potential depth (Δσ) of ordered Al1/2Ga1/2N models. In this work, we were able to evaluate large calculation cells based on the interaction energies between proximate Al atoms (δE Al–Al) in AlGaN alloys. To do this, δE Al–Al values were estimated by first-principles calculations (FPCs) using a (5a 1 × 5a 2 × 5c) cell. Next, a survey of the possible ordered configurations using various large calculation cell models was performed using the estimated δE Al–Al values and the Monte-Carlo method. Then, various Δσ values were estimated by FPCs and compared with the configurations previously reported by other research groups. We found that the ordered configuration obtained from the (4a 1 × 2a 2 × 1c) calculation cell (C 42) has the lowest Δσ of −9.3 meV/cation and exhibited an in-plane configuration at the c(0001) plane having (–Al–Al–Ga–Ga–) and (–Al–Ga–) sequence arrangements observed along the planes. Hence, we found consistencies between the morphology obtained from experiment and the shape of the primitive cell based on our numerical calculations.

Insight into Controllable Metal-Support Interactions in Metal/Metal Electrocatalysts for Efficient Energy-Saving Hydrogen Production.

Controllable metal-support interaction (MSI) modulations have long been studied for improving the performance of catalysts supported on metal oxides. However, the corresponding in-depth study for metal1-metal2 (M1-M2) composited configurations is rarely achieved due to the lack of reliable models and manipulation mechanisms of MSI modifications. We modeled ruthenium on copper support (Ru-Cu) metal catalysts with negligible interfacial contact potential (e0.06 V) and investigated MSI-dependent hydrogen evolution reaction (HER) catalysis kinetics induced by an electronic hydroxyl (HO-) modifier. Comprehensive simulations and characterizations confirmed that adjusting the HO- coverage can readily realize the tailorable improvement of MSI, facilitating charge migration at the Ru-Cu interface and optimizing the overall HER pathway on active Ru. As a result, a 5/10 monolayer (ML) HO-modified catalyst (5/10 ML) exhibits superior HER activity and durability owing to the relatively stronger MSI. This catalyst also ensured sustainable and efficient hydrogen generation in a urea electrolyzer with significant energy savings. Our work provides a valuable reference for optimizing the MSI-activity relationship in M1-M2 catalysts that target more than just HER.

Noncontact Layer Stabilization of Azafullerene Radicals: Route toward High-Spin-Density Surfaces.

We deposit azafullerene C59N• radicals in a vacuum on the Au(111) surface for layer thicknesses between 0.35 and 2.1 monolayers (ML). The layers are characterized using X-ray photoemission (XPS) and X-ray absorption fine structure (NEXAFS) spectroscopy, low-temperature scanning tunneling microscopy (STM), and by density functional calculations (DFT). The singly unoccupied C59N orbital (SUMO) has been identified in the N 1s NEXAFS/XPS spectra of C59N layers as a spectroscopic fingerprint of the molecular radical state. At low molecular coverages (up to 1 ML), films of monomeric C59N are stabilized with the nonbonded carbon orbital neighboring the nitrogen oriented toward the Au substrate, whereas in-plane intermolecular coupling into diamagnetic (C59N)2 dimers takes over toward the completion of the second layer. By following the C59N• SUMO peak intensity with increasing molecular coverage, we identify an intermediate high-spin-density phase between 1 and 2 ML, where uncoupled C59N• monomers in the second layer with pronounced radical character are formed. We argue that the C59N• radical stabilization of this supramonolayer phase of monomers is achieved by suppressed coupling to the substrate. This results from molecular isolation on top of the passivating azafullerene contact layer, which can be explored for molecular radical state stabilization and positioning on solid substrates.

Optical spectrum of n-type and p-type monolayer MoS2 in the presence of proximity-induced interactions

In this paper, we examined the effects of proximity-induced interactions such as Rashba spin-orbit coupling and effective Zeeman fields (EZFs) on the optical spectrum of n-type and p-type monolayer (ML)-MoS2. The optical conductivity is evaluated using the standard Kubo formula under random-phase approximation by including the effective electron–electron interaction. It has been found that there exist two absorption peaks in n-type ML-MoS2 and two knife shaped absorptions in p-type ML-MoS2, which are contributed by the inter-subband spin-flip electronic transitions within conduction and valence bands at valleys K and K′ with a lifted valley degeneracy. The optical absorptions in n-type and p-type ML-MoS2 occur in THz and infrared radiation regimes and the position, height, and shape of them can be effectively tuned by Rashba parameter, EZF parameters, and carrier density. The interesting theoretical predictions in this study would be helpful for the experimental observation of the optical absorption in infrared to THz bandwidths contributed by inter-subband spin-flip electronic transitions in a lifted valley degeneracy monolayer transition metal dichalcogenides system. The obtained results indicate that ML-MoS2 with the platform of proximity interactions make it a promising infrared and THz material for optics and optoelectronics.

Appearance of Different Conductance States in Monomolecular Films of Ferrocene-Decorated Triptycene-Based Tripods

Appearance of Different Conductance States in Monomolecular Films of Ferrocene-Decorated Triptycene-Based Tripods

Strain-induced effects on the optoelectronic properties of ZrSe2/HfSe2 heterostructures.

Two-dimensional semiconductor materials have received much attention in recent years due to their wide variety of applications in the field of nano-optoelectronic devices. In this project, we applied stresses ranging from -6 to +6% to the ZrSe2/HfSe2 heterostructure and systematically investigated its electrical and optical properties. It is discovered that stress can effectively modulate the forbidden bandwidth of the ZrSe2/HfSe2 heterojunction; whereas, under compressive stress, the forbidden bandwidth of the material decreases further until the bandgap is zero, leading to the material's transformation from semiconductor to metal. The forbidden band gap of the ZrSe2/HfSe2 heterojunction increases with increasing horizontal biaxial tensile strain. We discovered that the light absorption performance of this heterostructure is significantly better than that of its similar monomolecular layer and that its light absorption intensity can reach an order of magnitude of 104. Under compressive and tensile stresses, the ZrSe2/HfSe2 heterojunctions exhibit different degrees of red or blue shift. The results indicate that constructing ZrSe2/HfSe2 heterojunctions and applying horizontal biaxial stresses to them can significantly modulate the optoelectronic properties of the materials. ZrSe2/HfSe2 heterojunction is a new type of high-performance photogenerated carrier transport device with a wide range of applications. The calculations in this study are carried out the first principles approach of density functional theory, as implemented in the CASTEP module of Materials-Studio2019. The researchers used an ultrasoft reaction potential to calculate the interactions between the ion core and the electrons and applied the Perdew-Burke-Ernzerhof (PBE) and the generalized gradient approximation (GGA) to perform the calculations. The Monkhorst-Pack technique was employed to create the k-point samples utilized for integration on the Brillouin zone, and the k-point grid was uniformly 6 × 6 × 1. In addition, in order to avoid interactions between the atomic layers affecting the properties and stability of the material, such interactions were prevented by adding a 30 Å vacuum layer. Using a plane-wave energy cutoff of 500 eV and the convergence accuracy of the iterative process was set to 1 × 10-5 eV to ensure the accuracy of the computational results, and in addition. The maximum stress in the lattice was limited to less than 0.05 GPa or the interaction force between neighboring atoms was lower than 0.03 eV/Å. For the calculation of the properties of the optical properties, a k-point grid of 18 × 18 × 1 is used for optimization, and the polarization direction of the material is not taken into account, considering that the material is isotropic. This study proposes to apply the Tkatchenko-Scheffler (TS) dispersion correction method in DFT-D to appropriately represent the interlayer van der Waals interaction forces to solve inaccuracies in the computation of van der Waals interactions via density functional theory.

MiRNA-194-3p represses NF-κB in gliomas to attenuate iPSC genes and proneural to mesenchymal transition

Severe tumor heterogeneity drives the aggressive and treatment refractory nature of glioblastomas (GBMs). While limiting GBM heterogeneity offers promising therapeutic potential, the underlying mechanisms that regulate GBM plasticity remain poorly understood. We utilized 14 patient-derived and four commercially available cell lines to uncover miR-194-3p as a key epigenetic determinant of stemness and transcriptional subtype in GBM. We demonstrate that miR-194-3p degrades TAB2, an important mediator of NF-κB activity, decreasing NF-κB transcriptional activity. The loss in NF-κB activity following miR-194-3p overexpression or TAB2 silencing decreased expression of induced pluripotent stem cell (iPSC) genes, inhibited the oncogenic IL-6/STAT3 signaling axis, suppressed the mesenchymal transcriptional subtype in relation to the proneural subtype, and induced differentiation from the glioma stem cell (GSC) to monolayer (ML) phenotype. miR-194-3p/TAB2/NF-κB signaling axis acts as an epigenetic switch that regulates GBM plasticity and targeting this signaling axis represents a potential strategy to limit transcriptional heterogeneity in GBMs.

A method for the efficient removal of Pb(II) by D001 resin in a rotating packed bed

The treatment of Pb(II) is a challenging problem. In this study, a new approach for removal of Pb(II) using D001 resin in a rotating packed bed (RPB) is proposed, and the adsorption behaviors and mechanisms are investigated. The results reveal that under optimal conditions (initial Pb(II) concentration c0 = 100 mg L−1, high-gravity factor β = 36.33, liquid flow rate QL = 60 L h−1, initial solution pH = 5.0, and temperature T = 303 K), the removal rate of Pb(II) in RPB is 95.54 % at 120 min, which is 12.18 % and 9.81 % higher than that in thermostatic shaker (TS) and stirred tank reactor (STR). The adsorption of Pb(II) by D001 resin can be well described by the Langmuir adsorption isotherm and the adsorption heat is 13.24 kJ mol−1, and it is a typical monomolecular layer adsorption. It is also found that the adsorption mechanism of Pb(II) by D001 resin in RPB follows the pseudo-first-order kinetics, and the rate constant k1 is 1.72 and 1.64 times that in TS and STR. The R-SO3Na is the dominant group and Na+ undergoes ion exchange with Pb (II) on the surface of D001 resin. This study provides a new method for the treatment of Pb(II).

Effect of cationic dendrimer on membrane mimetic systems in the form of monolayer and bilayer

Interactions between a zwitterionic phospholipid, 1, 2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and four anionic phospholipids dihexadecyl phosphate (DHP), 1, 2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG), 1, 2-dipalmitoyl-sn-glycero-3-phosphate (DPP) and 1, 2-dipalmitoyl-sn-glycero-3-phospho ethanol (DPPEth) in combination with an additional amount of 30 mol% cholesterol were separately investigated at air-buffer interface through surface pressure (π) - area (A) measurements. π-A isotherm derived parameters revealed maximum negative deviation from ideality for the mixtures comprising 30 mol% anionic lipids. Besides the film functionality, structural changes of the monomolecular films at different surface pressures in the absence and presence of polyamidoamine (PAMAM, generation 4), a cationic dendrimer, were visualised through Brewster angle microscopy and fluorescence microscopic studies. Fluidity/rigidity of monolayers were assessed by surface dilatational rheology studies. Effect of PAMAM on the formation of adsorbed monolayer, due to bilayer disintegration of liposomes (DPPC:anionic lipids= 7:3 M/M, and 30 mol% cholesterol) were monitored by surface pressure (π) - time (t) isotherms. Bilayer disintegration kinetics were dependent on lipid head group and chain length, besides dendrimer concentration. Such studies are considered to be an in vitro cell membrane model where the alteration of molecular orientation play important roles in understanding the nature of interaction between the dendrimer and cell membrane. Liposome-dendrimer aggregates were nontoxic to breast cancer cell line as well as in doxorubicin treated MDA-MB-468 cell line suggesting their potential as drug delivery systems.

Charge Transfer and Asymmetric Coupling of MoSe2 Valleys to the Magnetic Order of CrSBr.

van der Waals heterostructures composed of two-dimensional (2D) transition metal dichalcogenides and vdW magnetic materials offer an intriguing platform to functionalize valley and excitonic properties in nonmagnetic TMDs. Here, we report magneto photoluminescence (PL) investigations of monolayer (ML) MoSe2 on the layered A-type antiferromagnetic (AFM) semiconductor CrSBr under different magnetic field orientations. Our results reveal a clear influence of the CrSBr magnetic order on the optical properties of MoSe2, such as an anomalous linear-polarization dependence, changes of the exciton/trion energies, a magnetic-field dependence of the PL intensities, and a valley g-factor with signatures of an asymmetric magnetic proximity interaction. Furthermore, first-principles calculations suggest that MoSe2/CrSBr forms a broken-gap (type-III) band alignment, facilitating charge transfer processes. The work establishes that antiferromagnetic-nonmagnetic interfaces can be used to control the valley and excitonic properties of TMDs, relevant for the development of opto-spintronics devices.

Isotropic Contact Properties in Monolayer GeAs Field-Effect Transistors

Owing to the tunable bandgap and high thermodynamic stability, anisotropic monolayer (ML) GeAs have arisen as an attractive candidate for electronic and optoelectronic applications. The contact properties of ML GeAs with 2D metal (graphene, Ti2CF2, V2CF2, and Ti3C2O2) and Cu electrodes are explored along two principal axes in field-effect transistors (FET) by employing ab initio electronic structure calculations and quantum transport simulations. Weak van der Waals interactions are found between ML GeAs and the 2D metal electrodes with the band structure of ML GeAs kept the same, while there is a strong interaction between ML GeAs and the Cu metal electrode, resulting in the obvious hybridization of the band structure. Isotropic contact properties are seen along the two principal directions. P-type lateral Schottky contacts are established in ML GeAs FETs with Ti3C2O2, graphene, and Ti2CF2 metals, with a hole Schottky barrier height (SBH) of 0.12 (0.20), 0.15 (0.11), and 0.29 (0.21) eV along the armchair (zigzag) direction, respectively, and an n-type lateral Schottky contact is established with the Cu electrode with an electron SBH of 0.64 (0.57) eV. Surprisingly, ML GeAs forms ideal p-type Ohmic contacts with the V2CF2 electrode. The results provide a theoretical foundation for comprehending the interactions between ML GeAs and metals, as well as for designing high-performance ML GeAs FETs.

Ultra-low Pt loading catalyst on (Nb–Ti)2AlC support as advanced material for low-temperature fuel cell application

ABSTRACT The oxygen reduction reaction was investigated at 10 monolayers (MLs) of Pt electrodeposited on (Nb–Ti)2AlC substrate. Following the discussion of detailed kinetics and electrodeposition optimisation in the authors’ previous paper, the focus of this research was on stability testing. Previously performed optimisation results showed the best activity shown by 10 monolayers of Pt. Catalyst characterisation was performed by scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. SEM, EDS and XPS analysis showed that the surface was covered with a homogeneous layer of Pt. TEM analysis of a cross-section confirmed the presence of Pt layer of thickness ∼3.5 nm, corresponding to the 10 MLs of Pt. Although the mass activity for the ORR at 0.8 V vs. RHE of 37.4 A g−1 was comparable with the best one for the Pt/C benchmark, US Department of Energy Protocols revealed excellent catalyst stability – the loss of electrochemically active surface area (EASA) was found to be only 9.3%.

Polyaniline as a Nitrogen Source and Lignosulfonate as a Sulphur Source for the Preparation of the Porous Carbon Adsorption of Dyes and Heavy Metal Ions.

Using agricultural and forestry wastes as raw materials, adsorbent materials were prepared for dye adsorption in wastewater, which can minimize the environmental load and fully realize sustainability by treating waste with waste. Taking lignosulfonate as a raw material, due to its molecular structure having more reactive groups, it is easy to form composite materials via a chemical oxidation reaction with an aniline monomer. After that, using a sodium lignosulfonate/polyaniline composite as the precursor, the activated high-temperature pyrolysis process is used to prepare porous carbon materials with controllable morphology, structure, oxygen, sulfur, and nitrogen content, which opens up a new way for the preparation of functional carbon materials. When the prepared O-N-S co-doped activated carbon materials (SNC) were used as adsorbents, the adsorption study of cationic dye methylene blue was carried out, and the removal rate of SNC could reach up to 99.53% in a methylene blue solution with an initial concentration of 100 mg/L, which was much higher than that of undoped lignocellulosic carbon materials, and the kinetic model conformed to the pseudo-second-order kinetic model. The adsorption equilibrium amount of NC (lignosulfonate-free) and SNC reached 478.30 mg/g and 509.00 mg/g, respectively, at an initial concentration of 500 mg/L, which was consistent with the Langmuir adsorption isothermal model, and the adsorption of methylene blue on the surface of the carbon material was a monomolecular layer. The adsorption of methylene blue dye on the carbon-based adsorbent was confirmed to be a spontaneous and feasible adsorption process by thermodynamic parameters. Finally, the adsorption of SNC on methylene blue, rhodamine B, Congo red, and methyl orange dyes were compared, and it was found that the material adsorbed cationic dyes better. Furthermore, we also studied the adsorption of SNC on different kinds of heavy metal ions and found that its adsorption selectivity is better for Cr3+ and Pb2+ ions.

Multi-scale utilization of lignin: A catalytic hydrogenation strategy based on catechyl lignin nanoparticles

With an abundance of oxygen-containing groups on the hydrophilic shell of lignin nanoparticles (LNPs), this biomaterial can serve as a catalytic support to adsorb and load metals. Herein, catechyl lignin oligomers from castor seed coats (Cas) were extracted via solvothermal pretreatment and prepared as LNPs using the solvent shifting method. Pd2+ ions were then stabilized and reduced in situ on the surface of LNPs, which were further utilized for the catalyzed hydrogenation of lignin-derived aldehydes. Due to the homogeneous building units and linear linkages, the lignin oligomers from Cas exhibited superior self-assembly capacity with a lower π-π interaction energy than those from conventional lignocelluloses, resulting in a high yield of LNPs with a smooth surface. The high content of phenolic hydroxyl groups in catechyl-dominant LNPs resulted in efficient Pd2+ ions adsorption via chemisorption of monomolecular layer and a partial reduction of the Pd2+ ions into metallic states. In addition, the Cas-derived Pd/LNPs exhibited exceptional catalytic activity for the hydrogenation of lignin-derived aldehydes with high selectivity to alcohols under mild conditions. This could be attributed to the interaction preference of the reaction substrate according to the construction of LNPs: strong hydrogen bond between the aldehyde group of the substrate and the hydrophilic shell of LNPs, as well as the hindered π-π interactions between the benzene ring of the substrate and the hidden hydrophobic core of LNPs. This study, therefore, successfully employed lignin with a broad range of molecular weights from oligomers to monomers, paving the way for a comprehensive lignin biorefining industry.

Easy separation dual-function Cu2O@LDH@Fe3O4 adsorbent for the removal of Cr(VI) under dark conditions: Experimental and mechanistic study

Designing a magnetic adsorbent material that is both reducible and has strong adsorption properties is significant in reducing Cr(VI) ion pollution. Herein, a 3D multifunctional composite adsorbent for Cr(VI) ions was obtained by using Fe3O4 surface-arrayed magnesium iron layered double hydroxides (Mg/Fe-LDH) micro sheets as a substrate with in situ growth of Cu2O nanoparticles (Cu2O NPs) on their surfaces. Under dark conditions, adsorption capacity of the Cu2O@LDH@Fe3O4 for Cr(VI) was up to 218.82 mg·g−1, surpassing that of Cu2O, Mg/Fe-LDH@Fe3O4, and Mg/Fe-LDH by factors of 1.39, 4.41, and 8.32 respectively. Surprisingly, the removal of Cr(VI) was as high as 76.16 % by the Cu2O@LDH@Fe3O4 (Cinitial = 200 mg/L, pH = 3). Kinetic, isotherm, and thermodynamic results reveal that the removal of Cr(VI) by the Cu2O@LDH@Fe3O4 is consistent with the pseudo-second-order kinetic model of spontaneous monomolecular layer chemisorption. Density functional theory (DFT) calculations show that HCrO4- has a lower energy band gap and is more easily reduced by Cu2O. Therefore, the reason for the adsorbent having more removal effect under acidic conditions was revealed. The XPS and FT-IR experimental mechanism analysis results indicated that Cr(VI) is immobilized on the Cu2O@LDH@Fe3O4 surface through electrostatic interactions, followed by reduction to Cr(III) by Cu2O NPs, which is subsequently adsorbed on the surface of the Cu2O@LDH@Fe3O4. This novel adsorbent structure and unique Cr(VI) removal mechanism provide new ideas for the design of future adsorbents.

Germanium surface cleaning and ALD of a protective boron nitride overlayer

Germanium exhibits superior hole and electron mobility compared with silicon, making it a promising candidate for replacement of silicon in certain future CMOS applications. In such applications, achieving atomically clean Ge surfaces and the subsequent deposition of ultrathin passivation barriers without interfacial reaction are critical. In this study, we present in situ x-ray photoelectron spectroscopy (XPS) investigations of hydrocarbon removal from the Ge surface utilizing atomic oxygen at room temperature, as well as removal of hydrocarbons and of germanium oxide (GeO2) through atomic hydrogen treatment at 350 °C. Subsequently, atomic layer deposition (ALD) was used to create a protective layer of hexagonal boron nitride (h-BN) with an average thickness of 3 monolayers (ML). Tris(dimethylamino)borane and ammonia precursors were utilized at 450 °C for the deposition process. Intermittent in situ XPS analysis during ALD confirmed h-BN growth, stoichiometry, and the absence of interfacial reaction with Ge. XPS analysis after subsequent exposure of the Ge film with a h-BN overlayer of ∼9 Å average thickness to 7.2 × 104 l of atomic O (O3P) at room temperature yielded no evidence of Ge oxidation, with only the surface layer of the h-BN film exhibiting oxidation. These results present a practical and scalable route toward the preparation of clean Ge surfaces and subsequent deposition of protective, nanothin h-BN barriers for subsequent processing.

Effect of Modified Biochar Prepared by Co-pyrolysis of MgO on Phosphate Adsorption Performance and Seed Germination.

Biochar is currently used as a phosphate adsorbent in water and subsequently as a soil amendment. In this study, modified biochar was prepared directly by co-pyrolysis of MgO and rice straw, and a preliminary ecotoxicological assessment was performed before the application of modified biochar to soil. The effects of single factors, such as pyrolysis temperature, dosage, pH, and coexisting ions, on phosphate adsorption performance were investigated. In addition, after phosphate adsorption, the effects of modified biochar leachate on the germination of corn and rice seeds were examined. The results showed that phosphate adsorption by the modified biochar first increased and then decreased as the pyrolysis temperature increased, with modified biochar prepared at 800 °C showing the greatest adsorption. In addition, a comprehensive cost analysis showed that the best phosphate adsorption effect of modified biochar was achieved at a dosage of 0.10 g and a solution pH of 3. In contrast, the presence of competitive coexisting ions, Cl- , NO3 - , CO3 2- , and SO4 2- , reduced the phosphate adsorption capacity of the modified biochar. The adsorption kinetics results revealed that the process of phosphate adsorption by the modified biochar was more in line with the pseudo-second-order model and dominated by chemisorption. Moreover, the adsorption isotherm results indicated that the process was more in line with the Langmuir model and dominated by monomolecular layer adsorption, with a maximum adsorption of 217.54 mg/g. Subsequent seed germination tests showed that phosphate-adsorbed modified biochar leachate had no significant effect on the germination rate of corn seeds, whereas it improved the germination rate of rice seeds. Together, these results provide guidance for the application of modified biochar firstly as an adsorbent of phosphate and subsequently as a soil remediator.