2D Monolayer Research Articles

Influence of cutoff radius and tip atomic structure on energy barriers encountered during AFM tip sliding on 2D monolayers

In computational studies using the Lennard–Jones (LJ) potential, the widely adopted 2.5 σ cutoff radius effectively truncates pairwise interactions across diverse systems (Santra et al 2008 J. Chem. Phys. 129 234704, Chen and Gao 2021 Friction 9 502–12, Bolintineanu et al 2014 Part. Mech. 1 321–56, Takahiro and Kazuhiro 2010 J. Phys.: Conf. Ser. 215 012123, Zhou et al 2016 Fuel 180 718–26, Toxvaerd and Dyre 2011 J. Chem. Phys. 134 081102, Toxvaerd and Dyre 2011 J. Chem. Phys. 134 081102). Here, we assess its adequacy in determining energy barriers encountered by a Si monoatomic tip sliding on various two-dimensional (2D) monolayers, which is crucial for understanding nanoscale friction. Our findings emphasize the necessity of a cutoff radius of at least 3.5 σ to achieve energy barrier values exceeding 95% accuracy across all studied 2D monolayers. Specifically, 3.5 σ corresponds to 12.70 Å in graphene, 12.99 Å in MoS2 and 13.25 Å in MoSe2. The barrier values calculated using this cutoff support previous experiments comparing friction between different orientations of graphene and between graphene and MoS2 (Almeida et al 2016 Sci. Rep. 6 31569, Zhang et al 2014 Sci. China 57 663–7). Furthermore, we demonstrate the applicability of the 3.5 σ cutoff for graphene on an Au substrate and bilayer graphene. Additionally, we investigate how the atomic configuration of the tip influences the energy barrier, finding a nearly threefold increase in the barrier along the zigzag direction of graphene when using a Si(001) tip composed of seven Si atoms compared to a monoatomic Si tip.

Photo-Cross-linked Gelatin Methacryloyl Hydrogels Enable the Growth of Primary Human Endometrial Stromal Cells and Epithelial Gland Organoids.

In vitro three-dimensional (3D) models are better able to replicate the complexity of real organs and tissues than 2D monolayer models. The human endometrium, the inner lining of the uterus, undergoes complex changes during the menstrual cycle and pregnancy. These changes occur in response to steroid hormone fluctuations and elicit crosstalk between the epithelial and stromal cell compartments, and dysregulations are associated with a variety of pregnancy disorders. Despite the importance of the endometrium in embryo implantation and pregnancy establishment, there is a lack of in vitro models that recapitulate tissue structure and function and as such a growing demand for extracellular matrix hydrogels that can support 3D cell culture. To be physiologically relevant, an in vitro model requires mechanical and biochemical cues that mimic those of the ECM found in the native tissue. We report a semisynthetic gelatin methacryloyl (GelMA) hydrogel that combines the bioactive properties of natural hydrogels with the tunability and reproducibility of synthetic materials. We then describe a simple protocol whereby cells can quickly be encapsulated in GelMA hydrogels. We investigate the suitability of GelMA hydrogel to support the development of an endometrial model by culturing the main endometrial cell types: stromal cells and epithelial cells. We also demonstrate how the mechanical and biochemical properties of GelMA hydrogels can be tailored to support the growth and maintenance of epithelial gland organoids that emerge upon 3D culturing of primary endometrial epithelial progenitor cells in a defined chemical medium. We furthermore demonstrate the ability of GelMA hydrogels to support the viability of stromal cells and their function measured by monitoring decidualization in response to steroid hormones. This study describes the first steps toward the development of a hydrogel matrix-based model that recapitulates the structure and function of the native endometrium and could support applications in understanding reproductive failure.

Relaxation effects in transition metal dichalcogenide bilayer heterostructures

While moiré structures in twisted bilayer transition metal dichalcogenides (TMDCs) have been studied for over a decade, the importance of lattice relaxation effects was pointed out only in 2021 by DiAngelo and MacDonald1, who reported the emergence of a Dirac cone upon relaxation. TMDCs of group 6 transition metals MX2 (M = Mo, W, X = S, Se) share layered structures with pronounced interlayer interactions, exhibiting a direct band gap when exfoliated to a two-dimensional (2D) monolayer. As their heterolayers are incommensurable, moiré structures are present in the bilayers even if stacked without a twist angle. This study addresses the challenge of accurately modeling and understanding the structural relaxation in twisted TMDC heterobilayers. We show that the typical experimental situation of finite-size flakes stacked upon larger flakes can reliably be modeled by fully periodic commensurate models. Our findings reveal significant lattice reconstruction in TMDC heterobilayers, which strongly depend on the twist angle. We can categorize the results in two principal cases: at or near the untwisted configurations of 0° and 60°, domains with matching lattice constants form and the two constituting layers exhibit significant in-phase corrugation—their out-of-plane displacements are oriented towards the same direction in all local stackings—while at large twist angles—deviating from the 0° and 60°—the two layers show an out-of-phase corrugation. In particular, we reveal that the lattice reconstruction results from the competition between the strain energy cost and the van der Waals energy gain. Additionally, our systematical study highlights structural disparities between heterostructures composed of different or identical chalcogen atoms. Our research not only confirms the reliability of using periodic commensurate models to predict heterostructure behavior but also enriches the understanding of TMDC bilayer heterostructures.

Recent Advances in the Synthesis and Application of Monolayer 2D Metal‐Organic Framework Nanosheets

Monolayer 2D metal‐organic framework (MOF) nanosheets, characterized by abundant exposed active sites and tunable structure and function (such as altering the metal nodes or organic ligands), have emerged as a pivotal class of 2D materials, demonstrating irreplaceable applications across diverse research domains in materials and chemistry. This review provides a comprehensive survey of the latest research progress in the synthesis of monolayer 2D MOF nanosheets. Specifically, recent synthetic strategies, including top‐down and bottom‐up methods, are delved and their applications in gas separation, catalysis, sensing platforms, and energy storage are explored. Additionally, the challenges faced in the investigation of monolayer 2D MOF nanosheets are elucidated and future opportunities for these materials as a novel generation of 2D materials are outlined.

Infrared Photodetector Based on van der Waals MoS2/MoTe2 Hetero‐Bilayer Modulated by Photogating

AbstractPhotodetectors based on 2D hetero‐bilayers can overcome the bandgap limitations of individual 2D monolayers and operate at relatively long wavelengths. However, ultra‐low light absorptions within hetero‐bilayers result in extremely weak photoresponsivity. Here, an infrared photodetector based on the MoS2/MoTe2 type‐II hetero‐bilayer is demonstrated to reach a photoresponsivity of 0.55 A W−1 at 1550 nm, well beyond energy band cut‐offs of monolayer MoS2 and MoTe2, primarily resulted from the photogating effect. Raman and photoluminescence (PL) spectroscopy reveal strong interlayer couplings in the hetero‐bilayer, and a broad PL peak around 1550 nm is observed that is ascribed to interlayer transitions of carriers. The photodetector showcases a broadband detection capability from 1100 to 1700 nm, with a peak at 1550 nm corresponding to the interlayer absorption. Electrical characterization of the hetero‐bilayer‐based field‐effect transistor and kelvin probe force microscopy reveal efficient interlayer hole transfer. The highly responsive MoS2/MoTe2 infrared photodetector offers a large photo‐gain of ≈103 and a time constant of 130 ms. The research illuminates how interlayer transitions affect 2D hetero‐bilayer‐based photodetectors and advances the utilization of layered semiconductor heterostructures.

Simple and Rapid Monolayer Self-Assembly of Nanoparticles at the Air/Water Interface.

Colloidal crystals and their two-dimensional (2D) monolayers, which have been commonly applied in nanosphere lithography, have the potential to revolutionize many engineering disciplines; however, current production techniques are hampered by a restricted preparation area, laborious procedures, and the need for advanced equipment. We propose a self-assembly-driven, simple, and low-cost method to prepare 2D colloidal nanosphere monolayers with excellent repeatability across wide regions. The self-assembly capability of colloidal polystyrene (PS) nanospheres at the air/water interface was utilized to transfer the assembled monolayers onto a substrate. This innovative method combines the advantages of methods that permit deposition at the air/water interface, such as Langmuir and drop coating, in order to deliver defect-free, simple-to-install, and simple-to-apply deposition across vast regions. Using field emission scanning electron microscopy and atomic force microscopy, the resultant coatings were characterized. The size of the nanospheres was reduced using an oxygen plasma etch process in an inductively coupled plasma reactive ion etching system, and the reflectance properties of the substrates for various nanosphere sizes were investigated. By evaporation of a thin gold capping layer on the templates, their optical properties were compared using surface-enhanced Raman scattering spectroscopy. This work has the potential to expand the use of nanosphere lithography by offering a simple and reproducible method that eliminates the need for complicated experimental setups and reduces the amount of material required for monolayer coating, thus lowering the cost.

Interfacial construction of 2D Au74Pt23Te3 nanotrough array for boosting alcohol electrooxidation

Two-dimensional (2D) Pt-based multi-metallic nanostructures have been demonstrated to be used as outstanding electrocatalysts for direct alcohol fuel cell owing to the merits of raising electrocatalytic activity and enhancing the durability of catalysts as well as saving Pt utilization. Herein, we develop an interface-confined strategy, achieving 2D close-packed AuPtTe nanotrough array. This strategy involves two steps: (1) assembly of Te nanowires into 2D monolayer array at hexane/water interfaces, and (2) transformation of 2D interfacial Te nanowire array into AuPtTe nanotrough array by interface-confined etching of PtCl62– and AuCl4– in the water subphase. Optimized 2D Au74Pt23Te3 nanotrough array exhibits ∼3.36 and ∼2.15 A mgAu+Pt–1 in the mass activity towards ethanol and methanol electrooxidation, respectively, ∼5 and 3 times that of commercial Pt/C, and shows superior durability to Pt/C, which may be attributed to the synergistic effects of the trough-like morphology and optimal composition. This work may open up a new perspective on the designing of components, morphologies, and compositions of advanced catalysts.

Assessment of P-glycoprotein function using canine intestinal organoid-derived epithelial interfaces

P-glycoprotein (P-gp), a multidrug efflux pump encoded by the ABCB1 (formerly MDR1) gene, plays a crucial role in limiting drug absorption and eliminating toxic compounds in both humans and dogs. However, species-specific differences in P-gp substrates necessitate the development of canine-specific evaluation systems. Canine intestinal organoids derived monolayers offer a promising platform for studying drug transport, yet P-gp-mediated transport in these models remains unexplored. We generated canine colonoid-derived 2D monolayers to investigate ABCB1 gene expression and P-gp function. We employed widely recognised P-gp substrates, Rhodamine 123 and Doxorubicin, in conjunction with the P-gp inhibitor PSC833 at Days 5 and 10 of culture. A significant increase in gene expression of P-gp encoded by the ABCB1 was noted on Day 10 compared to Day 5 of culture. Despite this disparity in gene expression, the transport activity of P-gp, as assessed by the efflux of Rhodamine 123 and Doxorubicin with PSC833 inhibition, did not exhibit significant differences between these two time points. However, the inhibition of P-gp function by PSC833 confirms the presence of functional P-gp in our model. Canine intestinal organoid-derived monolayers provide a valuable tool for investigating P-gp-mediated drug transport. These findings highlight the potential for predicting drug bioavailability and adverse reactions in veterinary medicine, aligning with principles of ethical and sustainable research.

Modeling 3D Tumor Invasiveness to Modulate Macrophage Phenotype in a Human-Based Hydrogel Platform.

The immune system is a pivotal player in determining tumor fate, contributing to the immunosuppressive microenvironment that supports tumor progression. Considering the emergence of biomaterials as promising platforms to mimic the tumor microenvironment, human platelet lysate (PLMA)-based hydrogel beads are proposed as 3D platforms to recapitulate the tumor milieu and recreate the synergistic tumor-macrophage communication. Having characterized the biomaterial-mediated pro-regenerative macrophage phenotype, an osteosarcoma spheroid encapsulated into a PLMA hydrogel bead is explored to study macrophage immunomodulation through paracrine signaling. The culture of PLMA-Tumor beads on the top of a 2D monolayer of macrophages reveals that tumor cells triggered morphologic and metabolic adaptations in macrophages. The cytokine profile, coupled with the upregulation of gene and protein anti-inflammatory biomarkers clearly indicates macrophage polarization toward an M2-like phenotype. Moreover, the increased gene expression of chemokines identified as pro-tumoral environmental regulators suggest a tumor-associated macrophage phenotype, exclusively stimulated by tumor cells. This pro-tumoral microenvironment is also found to enhance tumor invasiveness ability and proliferation. Besides providing a robust in vitro immunomodulatory tumor model that faithfully recreates the tumor-macrophage interplay, this human-based platform has the potential to provide fundamental insights into immunosuppressive signaling and predict immune-targeted response.

Quantum chemical modeling of alkane 2D monolayer formation on graphene

The paper presents a quantum chemical approach for assessment of the thermodynamic parameters of association for alkanes CnH2n+2 (n = 6–14) and polyaromatic hydrocarbons (PAH) of the coronene series as model structures of the graphene surface within the framework of semiempirical methods. The enthalpy, entropy and Gibbs energy of formation and binding for alkanes with PAH were calculated using the PM3 and PM6-DH2 methods. It is shown that an adequate description of the interactions in the regarded complexes requires the use of PM6-DH2 method, since it contains corrections for dispersion interactions and hydrogen bonds. The parallel orientation of the alkane molecule relative to the coronene plane is proved to be more energetically preferable than perpendicular one, which is consistent with experimental data.Intermolecular C–H/π interactions are revealed to be crucial in the 2D film formation of alkanes on graphene/graphite. While interactions between alkane molecules make a destabilizing contribution due to the implementation of energetically unfavorable types of intermolecular CH/HC interactions. This stipulates a threshold chain length of alkanes capable of film formation on the graphene/graphite surface at standard temperature: 14 and 19 carbon atoms for parallel and perpendicular oriented alkanes, respectively. The obtained threshold values of the alkane chain length, as well as the geometric parameters of their orientation in 2D monolayers on the graphene/graphite surface are consistent with available experimental data.

The first-principles study of 2D monolayer T-Mo2C as promising anode material for Lithium-ion Batteries

The growing demand for renewable energy technologies emphasizes the necessity for advancements in anode materials to enhance the performance of lithium-ion batteries (LIBs). In this research, we employ first-principles calculations to investigate the properties of a T-Mo2C monolayer proposed as an anode material. Phonon dispersion calculations and ab initio molecular dynamics (AIMD) simulations are conducted to assess the dynamical stability and thermal characteristics of the T-Mo2C monolayer as an anode material. Remarkably low diffusion barriers of 0.029 eV (Li) and 0.01 eV (Na and K) have been identified, facilitating rapid ion mobility. Furthermore, a monolayer of metal ions (M = Li, Na, K) absorbed onto T-Mo2C is explored, revealing a high specific capacity of approximately 1314.37 mAh/g (Li), 262.87 mAh/g (Na), and 32.85 mAh/g (K). The average open circuit voltage is determined to be 0.08 V (Li), 0.68 V (Na), and 2.59 V (K). This research provides a comprehensive overview of T-Mo2C monolayer as a high-capacity anode material, emphasizing its significant contributions to advancing energy storage systems, particularly in the context of LIBs. The findings presented here pave the way for the development of efficient and sustainable energy storage solutions to meet the escalating demands of the renewable energy landscape.

Deviatoric stress-induced metallization, layer reconstruction and collapse of van der Waals bonded zirconium disulfide

In contrast to two-dimensional (2D) monolayer materials, van der Waals layered transition metal dichalcogenides exhibit rich polymorphism, making them promising candidates for novel superconductor, topological insulators and electrochemical catalysts. Here, we highlight the role of hydrostatic pressure on the evolution of electronic and crystal structures of layered ZrS2. Under deviatoric stress, our electrical experiments demonstrate a semiconductor-to-metal transition above 30.2 GPa, while quasi-hydrostatic compression postponed the metallization to 38.9 GPa. Both X-ray diffraction and Raman results reveal structural phase transitions different from those under hydrostatic pressure. Under deviatoric stress, ZrS2 rearranges the original ZrS6 octahedra into ZrS8 cuboids at 5.5 GPa, in which the unique cuboids coordination of Zr atoms is thermodynamically metastable. The structure collapses to a partially disordered phase at 17.4 GPa. These complex phase transitions present the importance of deviatoric stress on the highly tunable electronic properties of ZrS2 with possible implications for optoelectronic devices.

Enhancing Magnetic Hyperthermia Efficacy through Targeted Heat Shock Protein 90 Inhibition: Unveiling Immune-Mediated Therapeutic Synergy in Glioma Treatment.

The induction of heat stress response (HSR) mediated by the generation of heat shock proteins (HSPs) on exposure to magnetic hyperthermia-mediated cancer therapy (MHCT) decreases the efficacy of localized heat treatment at the tumor site, and thus therapy remains a significant challenge. Hence, the present study examined differential HSR elicited in glioma cells post-MHCT under different tumor microenvironment conditions (2D monolayers, 3D monoculture, and coculture spheroids) to recognize target genes that, when downregulated, could enhance the therapeutic effect of MHCT. Gene expression analysis following MHCT revealed that HSP90 was upregulated as compared to HSP70. Hence, to enhance the efficacy of the treatment, a combinatorial strategy using 17-DMAG as an inhibitor of HSP90 following MHCT was investigated. The effects of combinatorial therapy in terms of cell viability, HSP levels by immunofluorescence and gene expression analysis, oxidative stress generation, and alterations in cellular integrity were evaluated, where combinatorial therapy demonstrated an enhanced therapeutic outcome with maximum glioma cell death. Further, in the murine glioma model, a rapid tumor inhibition of 65 and 53% was observed within 8 days at the primary and secondary tumor sites, respectively, in the MCHT + 17-DMAG group, with abscopal effect-mediated complete tumor inhibition at both the tumor sites within 20 days of MHCT. The extracellularly released HSP90 from dying tumor cells further suggested the induction of immune response supported by the upregulation of IFN-γ and calreticulin genes in the MHCT + 17-DMAG group. Overall, our findings indicate that MHCT activates host immune systems and efficiently cooperates with the HSP90 blockade to inhibit the growth of distant metastatic tumors.

Human Brain In Vitro Model for Pathogen Infection-Related Neurodegeneration Study.

Recent advancements in stem cell biology and tissue engineering have revolutionized the field of neurodegeneration research by enabling the development of sophisticated in vitro human brain models. These models, including 2D monolayer cultures, 3D organoids, organ-on-chips, and bioengineered 3D tissue models, aim to recapitulate the cellular diversity, structural organization, and functional properties of the native human brain. This review highlights how these in vitro brain models have been used to investigate the effects of various pathogens, including viruses, bacteria, fungi, and parasites infection, particularly in the human brain cand their subsequent impacts on neurodegenerative diseases. Traditional studies have demonstrated the susceptibility of different 2D brain cell types to infection, elucidated the mechanisms underlying pathogen-induced neuroinflammation, and identified potential therapeutic targets. Therefore, current methodological improvement brought the technology of 3D models to overcome the challenges of 2D cells, such as the limited cellular diversity, incomplete microenvironment, and lack of morphological structures by highlighting the need for further technological advancements. This review underscored the significance of in vitro human brain cell from 2D monolayer to bioengineered 3D tissue model for elucidating the intricate dynamics for pathogen infection modeling. These in vitro human brain cell enabled researchers to unravel human specific mechanisms underlying various pathogen infections such as SARS-CoV-2 to alter blood-brain-barrier function and Toxoplasma gondii impacting neural cell morphology and its function. Ultimately, these in vitro human brain models hold promise as personalized platforms for development of drug compound, gene therapy, and vaccine. Overall, we discussed the recent progress in in vitro human brain models, their applications in studying pathogen infection-related neurodegeneration, and future directions.

Multiaction Pt(IV) Prodrugs Releasing Cisplatin and Dasatinib Are Potent Anticancer and Anti-Invasive Agents Displaying Synergism between the Two Drugs.

Herein, we describe the general design, synthesis, characterization, and biological activity of new multitargeting Pt(IV) prodrugs that combine antitumor cisplatin and dasatinib, a potent inhibitor of Src kinase. These prodrugs exhibit impressive antiproliferative and anti-invasive activities in tumor cell lines in both two-dimensional (2D) monolayers of cell cultures and three-dimensional (3D) spheroids. We show that the cisplatin moiety and dasatinib in the investigated Pt(IV) complexes are both involved in the mechanism of action in MCF7 breast cancer cells and act synergistically. Thus, combining dasatinib and cisplatin into one molecule, compared to using individual components in a mix, may bring several advantages, such as significantly higher activity in cancer cell lines and higher selectivity for tumor cells. Most importantly, Pt(IV)-dasatinib complexes hold significant promise for potential anticancer therapies by targeting epithelial-mesenchymal transition, thus preventing the spread and metastasis of tumors, a value unachievable by a simple combination of both individual components.

Two-Dimensional and Spheroid-Based Three-Dimensional Cell Culture Systems: Implications for Drug Discovery in Cancer

The monolayer (two-dimensional or 2D) cell culture, while widely used, lacks fidelity in replicating vital cell interactions seen in vivo, leading to a shift toward three-dimensional (3D) models. Although monolayers offer simplicity and cost-effectiveness, spheroids mimic cellular environments better. This is due to its nutrient gradients, which influence drug penetration and provide a more accurate reflection of clinical scenarios than monolayers. Consequently, 3D models are crucial in drug development, especially for anti-cancer therapeutics, enabling the screening of cell cycle inhibitors and combination therapies vital for heterogeneous tumor populations. Inhibiting processes like migration and invasion often require drugs targeting the cytoskeleton, which can exhibit dual functionality with cell cycle inhibitors. Therapeutic approaches with promising anti-cancer potential often exhibit reduced efficacy in 3D cell culture compared to their performance in monolayer settings, primarily due to the heightened complexity inherent in this system. In the face of this scenario, this review aims to survey existing knowledge on compounds utilized in both 2D and 3D cell cultures, assessing their responses across different culture types and discerning the implications for drug screening, particularly those impacting the cell cycle and cytoskeletal dynamics.

Triethylene Glycol Squalene Improves Hair Regeneration by Maintaining the Inductive Capacity of Human Dermal Papilla Cells and Preventing Premature Aging.

De novo hair follicle (HF) regeneration, achieved through the replenishment of the dermal papilla (DP), acknowledged as the principal orchestrator of the hair growth cycle, is emerging as a prospective therapeutic intervention for alopecia. Nonetheless, multiple attempts have shown that these cells lose key inductive properties when cultured in a two-dimensional (2D) monolayer, leading to precocious senescence engendered by oxidative stress and inflammatory processes. Consequently, the three-dimensional (3D) spheroid technique is presently widely employed for DP cell culture. Nevertheless, substantiating the regenerative potential of these cells within the hair follicle (HF) milieu remains a challenge. In this current study, we aim to find a new approach to activate the inductive properties of DP cells. This involves the application of hair-growth-stimulating agents that not only exhibit concurrent protective efficacy against the aging process but also induce HF regeneration. To achieve this objective, we initially synthesized a novel highly amphiphilic derivative derived from squalene (SQ), named triethylene glycol squalene (Tri-SQ). Squalene itself is a potent antioxidant and anti-inflammatory compound traditionally employed as a drug carrier for alopecia treatment. However, its application is limited due to its low solubility. Subsequently, we applied this newly synthesized derivative to DP cells. The data obtained demonstrated that the derivative exhibits robust antioxidant and anti-inflammatory activities while concurrently promoting the expression of genes associated with hair growth. Moreover, to further assess the hair regrowth inductive properties of DP cells, we cultured the cells and treated them with Tri-SQ within a 3D spheroid system. Subsequently, these treated cells were injected into the previously depilated dorsal area of six-week-old male C57BL/6 mice. Results revealed that 20 days postinjection, a complete regrowth of hair in the previously hairless area, particularly evident in the case of 3D spheroids treated with the derivative, was observed. Additionally, histological and molecular analyses demonstrated an upregulation of markers associated with hair growth and a concurrent decrease in aging hallmarks, specifically in the 3D spheroids treated with the compound. In summary, our approach, which involves the treatment of Tri-SQ combined with a 3D spheroid system, exhibited a notably robust stimulating effect. This effect was observed in the induction of inductive properties in DP cells, leading to HF regeneration, and concurrently, it demonstrated an inhibitory effect on cellular and follicular aging.

Understanding the Electronic Structure and Chemical Bonding in the 2D Fullerene Monolayer.

Recently synthesized two-dimensional (2D) monolayer quasi-hexagonal-phase fullerene (qHPC60) demonstrates excellent thermodynamic stability. Within this monolayer, each fullerene cluster is surrounded by six adjacent C60 cages along an equatorial plane and is connected by both C-C single bonds and [2 + 2] cycloaddition bonds that serve as bridges. In this study, we investigate the stability mechanism of the 2D qHPC60 monolayer by examining the electronic structure and chemical bonding through state-of-the-art theoretical methodologies. Density functional theory (DFT) studies reveal that 2D qHPC60 possesses a moderate direct electronic band gap of 1.46 eV, close to the experimental value (1.6 eV). It is found that the intermolecular bridge bonds play a crucial role in enhancing the charge flow and redistribution among C60 cages, leading to the formation of dual π-aromaticity within the C60 sphere and stabilizing the 2D framework structure. Furthermore, we identify a series of delocalized superatom molecular orbitals (SAMOs) within the 2D qHPC60 monolayer, exhibiting atomic orbital-like behavior and hybridization to form nearly free-electron (NFE) bands with σ/π bonding and σ*/π* antibonding properties. Our findings provide insights into the design and potential applications of NFE bands derived from SAMOs in 2D qHPC60 monolayers.

Broadband tunable resonance modes from multi-composition monolayer MoS2(1−x)Se2x with SiO2 microsphere cavity

Two-dimensional (2D) monolayer transition metal dichalcogenides (TMDCs) that are compatible with Si-based substrates have already exhibited huge application potential in optoelectronics and photonics. The MoS2(1−x)Se2x ternary alloy consisting of two different chalcogens, as a class of lasing gain medium, enriches the family of 2D TMDC materials. Here, monolayer MoS2(1−x)Se2x ternary alloys with tunable composition have been synthesized via single-step chemical vapor deposition method. Raman and photoluminescence studies demonstrate that the bandgap of grown monolayer MoS2(1−x)Se2x alloys can be gradually tuned from 1.59 to 1.82 eV, indicating the continuous changes of the chemical composition x from 0.82 to 0. The oscillation characteristic is further investigated, where the MoS2(1−x)Se2x alloy provides optical gain for the SiO2 microsphere resonant cavity. The achieved resonance modes in a broadband range from 610 to 810 nm not only extend the range of potential TMDC-based lasers, but also drive the applications of alloy materials in various optoelectronics devices.

Universality of optoelectronic and thermoelectric properties of novel two-dimensional CrSiM2N (M=As, P and N[dbnd]Se, Te) monolayers and their vdWHs with MoTe2

In this study, we introduce a novel two-dimensional (2D) monolayer of CrSiM2N (M = As, P and NSe, Te) and explore its electronic properties. For the first time, we employ density functional theory and investigate the electronic and thermoelectric (TE) properties of CrSiM2N (M = As, P and NSe, Te) monolayers. Our calculated phonon band structure confirms that these monolayers are stable and can potentially be synthesized experimentally. The CrSiM2N (M = As, P and NSe, Te) monolayers exhibit an indirect band nature, with the CBM and VBM located at the K and G-points of the first Brillouin zone, respectively. We have also calculated the thermoelectric properties of these systems, which suggest that these monolayers could play a crucial role in enhancing the thermoelectric performance. Furthermore, we investigated the electronic, optical and thermoelectric properties of CrSiM2N (M = As, P and NSe, Te) and MoTe2 van der Waals heterostructures (vdWHs). The electronic band structure exhibits an indirect semiconductor nature, with the conduction band maxima and valence band minima originating from the CrSiM2N (M = As, P and NSe, Te) and MoTe2 monolayers, thereby confirming a type II band alignment. The optical properties indicate that these vdWHs can absorb a broad range of light, from the ultraviolet to the visible and infrared regions. We demonstrated that CrSiM2N (M = As, P and NSe, Te) monolayers exhibit p-type TE behavior, while their vdWHs counterparts exhibit n-type TE behavior.