Heterostructured Monolayer MoS2 Nanoparticles toward Water-Dispersible Catalysts

Ultrathin and high-performance electromagnetic wave absorbers enabled by phase-engineered FeSiAl@1T/2H MoS2 interfaces

With society progressing toward intelligent systems and the escalating challenges of electromagnetic radiation, the demand for advanced electromagnetic wave (EMW)-absorbing materials has intensified. The prevalent methodology combines magnetic components with dielectric matrices to harness interfacial synergy, enabling concurrent optimization of impedance matching and enhancement in functionality. With better understanding of absorption mechanisms, there has been an increase in microscopic studies. Herein, we demonstrate a hydrothermal route for synthesizing mixed-phase molybdenum disulfide (MoS2-1T/2H) composites with magnetic FeSiAl particles, forming a core-shell FeSiAl@1T/2H MoS2 architecture containing 61% metastable 1T phase. This design leverages the phase-dependent electronic contrast between metallic 1T and semiconducting 2H phases of MoS2. Phase-engineering strategies enable the adjustment of conductive loss and the creation of heterogeneous interfaces, broadening the loss mechanisms and enhancing impedance matching (Z). Achieving an optimal balance between dielectric loss and Z is crucial for improving EMW absorption (EMWA) performance. The material exhibited a minimum reflection loss (RLmin) of -65.6 dB at 1.77 mm and a maximum effective absorption bandwidth (EABmax) of 5.57 GHz at 1.91 mm, offering significant insights into the development of ultra-thin, high-efficiency EMW absorbers. Radar cross-section (RCS) simulations with CST Studio Suite confirmed a 34.0 dB m2 reduction for flat model at 15.81 GHz, providing foundational guidelines for multifrequency adaptive EMWA material engineering.

MnFe2O4/MoS2 catalyst used for ozonation: optimization and mechanism analysis of phenolic wastewater treatment

The performance of catalytic ability of MFe2O4/MoS2 in the ozonation process was investigated in this work. The synthesized MnFe2O4/MoS2 was optimize prepared and then characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photo-electron spectroscopy, and magnetic saturation strength. The results showed that when Cphenol = 200 mg/L, initial pH = 9.0, Q = 0.10 L/min, and CMnFe2O4/MoS2 = 0.10 g/L, MnFe2O4/MoS2 addition improved the degradation efficiency of phenol by 20.0%. The effects of pH, catalyst dosage, and inorganic ions on the phenol removal by the MnFe2O4/MoS2 catalytic ozonation were investigated. Five cycle experiments proved that MnFe2O4/MoS2 had good recyclability and stability. MnFe2O4/MoS2 also showed good catalytic performance in the treatment of coal chemical wastewater pesticide wastewater. The MnFe2O4 doped with MoS2 could provide abundant surface active sites for ozone and promote the stable cycle of Mn2+/Mn3+and Fe2+/Fe3+, thus generating large amounts of •OH and improving the degradation of phenol by ozonation. The MnFe2O4/MoS2/ozonation treatment system provides a technical reference and theoretical basis for industrial wastewater treatment.

Nanocatalysis MoS2/rGO: An Efficient Electrocatalyst for the Hydrogen Evolution Reaction

In this study, a systematic investigation of MoS2 nanostructure growth on a SiO2 substrate was conducted using a two-stage process. Initially, a thin layer of Mo was grown through sputtering, followed by a sulfurization process employing the CVD technique. This two-stage process enables the control of diverse nanostructure formations of both MoS2 and MoO3 on SiO2 substrates, as well as the formation of bulk-like grain structures. Subsequently, the addition of reduced graphene oxide (rGO) was examined, resulting in MoS2/rGO(n), where graphene is uniformly deposited on the surface, exposing a higher number of active sites at the edges and consequently enhancing electroactivity in the HER. The influence of the synthesis time on the treated MoS2 and also MoS2/rGO(n) samples is evident in their excellent electrocatalytic performance with a low overpotential.

Engineering a hierarchically micro-/nanostructured Si@Au-based artificial enzyme with improved accessibility of active sites for enhanced catalysis

The active site accessibility and high loading of gold nanoparticles (AuNPs) are key factors affecting the catalytic activity of supported AuNP-based catalysts. However, the preparation of supported AuNP-based catalysts with highly accessible active sites still remains a challenge. Herein, sphere-on-sphere (SoS) silica microspheres with a hierarchical structure, good dispersion and high surface density of thiol groups (10 SH nm-2) are prepared and used as a platform for the growth of high-density AuNPs. The obtained hierarchical Si@Au micro-/nanostructure consisting of 0.55 μm SoS silica microspheres and 7.3 nm AuNPs (SoS-0.55@Au-7.3) is found to show excellent peroxidase-mimicking activity (Km = 0.033 mM and Vmax = 34.6 × 10-8 M s-1) with merits of high stability and good reusability. Furthermore, the as-obtained SoS-0.55@Au-7.3-based system can sensitively detect hydrogen peroxide (H2O2) with a low detection limit of 1.6 μM and a wide linear range from 2.5 μM to 1.0 mM. The high catalytic activity, excellent stability and good reusability of SoS-0.55@Au-7.3 imply its great prospects in biosensing and biomedical analysis.

Bubble Printing of Layered Silicates: Surface Chemistry Effects and Picomolar Förster Resonance Energy Transfer Sensing

The assembly of nanoparticles on surfaces in defined patterns has long been achieved via template-assisted methods that involve long deposition and drying steps and the need for molds or masks to obtain the desired patterns. Control over deposition of materials on surfaces via laser-directed microbubbles is a nascent technique that holds promise for rapid fabrication of devices down to the micrometer scale. However, the influence of surface chemistry on the resulting assembly using such approaches has so far not been studied. Herein, the printing of layered silicate nanoclays using a laser-directed microbubble was established. Significant differences in the macroscale structure of the printed patterns were observed for hydrophilic, pristine layered silicates compared to hydrophobic, modified layered silicates, which provided the first example of how the surface chemistry of such nanoscale objects results in changes in assembly with this approach. Furthermore, the ability of layered silicates to adsorb molecules at the interface was retained, which allowed the fabrication of proof-of-concept sensors based on Förster resonance energy transfer (FRET) from quantum dots embedded in the assemblies to bound dye molecules. The detection limit for Rhodamine 800 sensing via FRET was found to be on the order of 10-12 M, suggesting signal enhancement due to favorable interactions between the dye and nanoclay. This work sets the stage for future advances in the control of hierarchical assembly of nanoparticles by modification of surface chemistry while also demonstrating a quick and versatile approach to achieve ultrasensitive molecular sensors.

Investigating Solvent-Induced Aggregation in Edge-Functionalized Layered Silicates via All-Atom Molecular Dynamics Simulations

Molecular dynamics simulations can provide the means to visualize and understand the role of intermolecular interactions in the mechanisms involved in molecular aggregation. Along these lines, simulations can allow the study of how surface chemical modifications can influence nanomaterial assembly at the molecular level. Layered silicate clays have been of significant interest for some time, particularly with regard to their use in organic/inorganic nanocomposites. However, despite numerous reports on the covalent linkage of organic moieties via silanol condensation, the theoretical understanding of these systems has heretofore been limited to noncovalent interactions, specifically ionic interactions at the charged basal surfaces. Herein, a model for edge-functionalized layered aluminosilicate clay, based on the siloxane linkage, is presented. In addition to reproducing experimentally observed degrees of molecular aggregation of clay-linked perylene diimide derivatives with different terminal functional groups as a function of solvent composition, a molecular-level understanding of the role of van der Waals interactions and hydrogen bonding of the different end-groups on the aggregation state in different water/N,N-dimethylformamide mixtures is obtained. The reported model provides a means to simulate organic moieties covalently bound to the layered silicate edge, which will enable future simulations of nanocomposites and organic/inorganic hybrids based on this system.

Layered silicate edge-linked perylene diimides: Synthesis, self-assembly and energy transfer

The control over intermolecular interactions between chromophores at nanomaterial interfaces is important for sensing and light-harvesting applications. To that aim, inorganic nanoparticles with anisotropic shape and surface chemistry can serve as useful supports for organic modification. Herein, novel asymmetric perylene diimides with aspartic acid and oleyl terminal groups were grafted to the edges of the layered silicate clay Laponite, a water-dispersible discoidal nanoparticle. The photophysical properties and solvent-dependent self-assembly of the nanoclay-grafted perylenes were investigated, revealing that the polarity of the terminating ligand dictates the aggregation behavior in aqueous solution, where increased water content generally led to the formation of perylene H-aggregates. The anionic basal surface of the nanoclay provided a binding site for a cationic fluorophore, leading to energy transfer from the face-bound donor to the edge-bound perylene acceptor. This study encourages further research on the use of functional ligands for the formation of organic-inorganic hybrids, particularly where inorganic template particles with specific surface chemistry can be exploited to study intermolecular interactions. Overall, these findings should advance further design and implementation of novel semiconducting ligands towards inorganic-organic hybrids, with potential applications in sensing and energy harvesting.

Layered Double Hydroxide-Bismuth Molybdate Hybrids toward Water Remediation via Selective Adsorption of Anionic Species

The steady release of anthropogenic toxins into the biosphere is compromising water security globally. Herein, CoAl layered double hydroxide, a clay-like layered material with a cationic surface charge, was organically modified and used to template the growth of Bi₂MoO₆. The resulting nanohybrid selectively removed the anionic dye methyl orange from aqueous solution and showed an enhancement of greater than 300% in the maximum adsorptivity (1.95 mmol/g) compared to modified CoAl layered double hydroxide (0.42 mmol/g). Interestingly, the observed improvement in adsorption occurs without any significant increase in the surface area of the hybrids. Furthermore, these hybrids exhibit increased broadband visible light absorption, and their photoactivity is slightly improved compared to CoAl layered double hydroxide. This study demonstrates that composites of clay-like materials with Aurivillius oxides are promising sorbent materials for water decontamination and photocatalytic antifouling membranes and shows that the synthetic strategy that was first established with an anionic layered silicate nanoclay can be generalized to other ionic layered materials.

Edge Rich Ultrathin Layered MoS2 Nanostructures for Superior Visible Light Photocatalytic Activity

Nanostructures of layered 2D materials have been proven one of the significant recent trends for visible-light-driven photocatalysis because of their unique morphology, effective optical adsorption, and rich active sites. Herein, we synthesized ultrathin-layered MoS₂ nanoflowers and nanosheets with rich active sites by using a facile hydrothermal technique. The photocatalytic performance of the as-synthesized MoS₂ nanoflowers (NF) and nanosheets (NS) were investigated for the photodegradation of MB (methylene blue), MG (malachite Green), and RhB (rhodamine B) dye under visible light irradiations. Ultrathin-layered nanoflowers showed faster degradation (96% in 150 min) in RhB under visible light irradiation, probably due to a large number of active sites and high available surface area. The kinetic study demonstrated that the first-order kinetic model best explained the process of photodegradation. The MoS₂ nanoflowers catalysts has similar catalytic performance after four consecutive cyclic performances, demonstrating their good stability. The results showed that the MoS₂ nanoflowers have outstanding visible-light-driven photocatalytic activity and could be an effective catalyst for industrial wastewater treatment.

Surface-Encapsulated Bismuth Molybdate-Layered Silicate Hybrids as Sorbents for Photocatalytic Filtration Membranes

Groundwater is being depleted globally at an average rate of more than one meter per year, during a period when more than a quarter of the human population has no access to potable water. Aside from overexploitation, freshwater security is also threatened by climate change and chemical pollution. The contamination of surface and groundwater by industrial substances is also undermining the vitality of ecosystems. It was previously shown that {100}-faceted Bi2MoO6-Laponite hybrids effectively bind and photodegrade molecular species, aiding in the decontamination of water. In this study, the encapsulation of Bi2MoO6-Laponite particles with the polymers butyl acrylate and styrene further enhanced adsorption of methylene blue by 31.4%, with a specific adsorption capacity of 192 μmol/g. The polymer-particle composites were deposited to form membranes and their efficacies in water filtration and photodegradation were examined. Among the different surface modifications examined, the highest dye sorption was obtained by butyl acrylate and styrene (3:2) with a 5 mol % cross-linker. This study provides a method for enhancing the molecular adsorption of composite particles used in membranes capable of multiple cycles of adsorption and photodegradation, advancing the application of such systems to water filtration.

One-Pot Synthesis of One-Dimensional Multijunction Semiconductor Nanochains from Cu1.94S, CdS, and ZnS for Photocatalytic Hydrogen Generation

Chains of alternating semiconductor nanocrystals are complex nanostructures that can offer control over photogenerated charge carriers dynamics and quantized electronic states. We develop a simple one-pot colloidal synthesis of complex Cu_1.94S-CdS and Cu_1.94S-ZnS nanochains exploiting an equilibrium driving ion exchange mechanism. The chain length of the heterostructures can be tuned using a concentration dependent cation exchange mechanism controlled by the precursor concentrations, which enables the synthesis of monodisperse and uniform Cu_1.94S-CdS-Cu_1.94S nanochains featuring three epitaxial junctions. These seamless junctions enable efficient separation of photogenerated charge carriers, which can be harvested for photocatalytic applications. We demonstrate the superior photocatalytic activity of these noble metal free materials through solar hydrogen generation at a hydrogen evolution rate of 22.01 mmol g^-1 h^-1, which is 1.5-fold that of Pt/CdS heterostructure photocatalyst particles.

Facet Engineering of Bismuth Molybdate via Confined Growth in a Nanoscale Template toward Water Remediation

Certain nanomaterials can filter and alter unwanted compounds due to a high surface area, surface reactivity, and microporous structure. Herein, γ-Bi₂MoO₆ particles are synthesized via a colloidal hydrothermal approach using organically modified Laponite as a template. This organically modified Laponite interlayer serves as a template promoting the growth of the bismuth molybdate crystals in the [010] direction to result in hybrid Laponite-Bi₂MoO₆ particles terminating predominantly in the {100} crystal facets. This resulted in an increase in particle size from lateral dimensions of <100 nm to micron scale and superior adsorption capacity compared to bismuth molybdate nanoparticles. These {100}-facet terminated particles can load both cationic and anionic dyes on their surfaces near-spontaneously and retain the photocatalytic properties of Bi₂MoO₆. Furthermore, dye-laden hybrid particles quickly sediment, rendering the task of particle recovery trivial. The adsorption of dyes is completed within minutes, and near-complete photocatalytic degradation of the adsorbed dye in visible light allowed recycling of these particles for multiple cycles of water decontamination. Their adsorption capacity, facile synthesis, good recycling performance, and increased product yield compared to pure bismuth molybdate make them promising materials for environmental remediation. Furthermore, this synthetic approach could be exploited for facet engineering in other Aurivillius-type perovskites and potentially other materials.

Few-Layer ZnIn2S4/Laponite Heterostructures: Role of Mg2+ Leaching in Zn Defect Formation

Designing nanostructures with extended light absorption via defect engineering is a useful approach for the synthesis of efficient photocatalysts. Herein, ZnIn₂S₄ was grown hydrothermally in the modified interlayer space of Laponite, resulting in lamellae consisting of Zn-defective ZnIn₂S₄ several unit cells thick. In the process it was found that Mg²⁺ leached from Laponite during synthesis led to the formation of Zn defects in ZnIn₂S₄. This resulted in nanohybrids with light absorption extended across the visible spectrum and in improved charge transfer due to the layered structure formed via confined growth. Compared with pure ZnIn₂S₄, Zn-defective ZnIn₂S₄-Laponite hybrids have increased photocurrent generation and photocatalytic performance. The leaching of Mg²⁺ and the resulting formation of Zn defects was attenuated by addition of 4 mM Mg²⁺ to the reaction, due to a combination of shifting of the equilibrium of Mg²⁺ leaching toward stability, and increased ionic strength. In summary, this work demonstrates the growth of ∼1 nm thick lamellae of ZnIn₂S₄, presents a unique strategy to generate cation defects in nanomaterials and the mechanism behind it, and also provides an approach to mitigate Mg²⁺ leaching in such syntheses.

Adsorption of atomic hydrogen on monolayer MoS2

The adsorption of atomic hydrogen on monolayer MoS₂has been intensively studied, but the ground-state adsorption configuration remains controversial. In this study, we investigate the adsorption properties of atomic hydrogen on monolayer MoS₂systematically using first-principles density functional theory calculations. We considered all the previously proposed adsorption sites, S-top, bridge, and hollow sites. Among them, S-top is the most energetically preferred, with a tilted S-H bond. Its calculated adsorption energy is -0.72 eV. The next lowest-energy configuration is that the H atom is located at the hollow site; the adsorption energy is slightly higher than the former, by 0.22 eV. The tilting of the S-H bond contributes to the adsorption energy up to -0.29 eV, a factor unrecognized in previous first-principles studies. These results account for the discrepancy in theory. Besides, the effects of spin-polarization also change the relative energetics of possible adsorption configurations.

Surface modification of black phosphorus-based nanomaterials in biomedical applications: Strategies and recent advances

Black phosphorus-based nanomaterials (BPNMs), an emerging member of two-dimensional (2D) nanomaterials, possess excellent physicochemical properties and hold great potential for application in advanced nanomedicines. However, the bare BPNMs easily decrease their biomedical activities due to their degradability and in vivo interactions with biological macromolecules such as plasma proteins, largely restricting their biomedical application. A variety of surface modifications, via chemical, physical or biological approaches, have been developed for BPNMs to avoid these limitations and achieve stable, long-lasting and safe therapeutic effects, thus enlighten the development of the multifunctional BPNMs for more practical application in the field of biomedicine. The present review summarizes the recent advances in the surface modification of BPNMs and the resultant expansion of their biomedical applications. Focus is put on the strategy and method of modification while the effects incurred on the behavior and potential toxicity of BPNMs are also included. The future and challenge of the surface modification of the therapeutic BPNMs are finally discussed.